[ { "start": 54942, "end": 54961, "text": "Normal physiology", "kind": "literal", "quote": "'" }, { "start": 54968, "end": 54987, "text": "Normal physiology", "kind": "literal", "quote": "'" }, { "start": 54994, "end": 55016, "text": "Stage 1 · Physiology", "kind": "literal", "quote": "'" }, { "start": 55021, "end": 55046, "text": "The reference rectangle", "kind": "literal", "quote": "'" }, { "start": 55057, "end": 55235, "text": "A textbook resting loop: EF ~55%, SV ~80 mL, 120/80 mmHg. Ventriculo-arterial coupling (Ea/Ees) sits near 0.7, so the heart delivers stroke work at close to maximum efficiency.", "kind": "literal", "quote": "'" }, { "start": 55270, "end": 55283, "text": "Ea/Ees ~0.7", "kind": "literal", "quote": "'" }, { "start": 55294, "end": 55362, "text": "Physiologic reference: Sagawa 1988; Suga 1979 elastance framework.", "kind": "literal", "quote": "'" }, { "start": 55376, "end": 55543, "text": "The loop runs counter-clockwise through four phases. The width is stroke volume; the enclosed area is stroke work.", "kind": "literal", "quote": "'" }, { "start": 55554, "end": 55776, "text": "Three boundary lines define the space. ESPVR (top-left) is set by contractility. EDPVR (bottom) is set by passive stiffness. Ea (the diagonal) is the arterial load the ventricle ejects against.", "kind": "literal", "quote": "'" }, { "start": 55785, "end": 56001, "text": "
Anchor point: peak LV pressure ≈ aortic systolic pressure here. The ventricle and the aorta communicate through a wide-open valve. Keep that in mind; in aortic stenosis they diverge.
", "kind": "literal", "quote": "`" }, { "start": 56021, "end": 56031, "text": "Exercise", "kind": "literal", "quote": "'" }, { "start": 56038, "end": 56065, "text": "Exercise / catecholamines", "kind": "literal", "quote": "'" }, { "start": 56072, "end": 56094, "text": "Stage 1 · Physiology", "kind": "literal", "quote": "'" }, { "start": 56099, "end": 56118, "text": "Bigger and taller", "kind": "literal", "quote": "'" }, { "start": 56129, "end": 56297, "text": "Sympathetic drive raises contractility (steeper ESPVR) while venous return raises preload. The loop grows in every direction: more SV, higher pressure, higher output.", "kind": "literal", "quote": "'" }, { "start": 56344, "end": 56410, "text": "Contractile & Frank–Starling reserve; Sunagawa coupling reserve.", "kind": "literal", "quote": "'" }, { "start": 56424, "end": 56581, "text": "Exercise recruits both preload (venous return) and contractility (β-adrenergic ESPVR steepening). Stroke volume and output climb together.", "kind": "literal", "quote": "'" }, { "start": 56592, "end": 56755, "text": "Note that Ea/Ees falls. Contractility rises faster than load, so coupling shifts toward the efficient end. This is contractile reserve.", "kind": "literal", "quote": "'" }, { "start": 56764, "end": 56921, "text": "
Real hearts also raise heart rate; this fixed-rate model shows only the per-beat mechanics, so output here is conservative.
", "kind": "literal", "quote": "`" }, { "start": 56940, "end": 56954, "text": "Hypovolaemia", "kind": "literal", "quote": "'" }, { "start": 56961, "end": 56989, "text": "Hypovolaemia / haemorrhage", "kind": "literal", "quote": "'" }, { "start": 56996, "end": 57018, "text": "Stage 1 · Physiology", "kind": "literal", "quote": "'" }, { "start": 57023, "end": 57049, "text": "Small loop, shifted left", "kind": "literal", "quote": "'" }, { "start": 57060, "end": 57243, "text": "Loss of circulating volume drops preload. The loop slides down the EDPVR and shrinks, with a lower SV and a lower pressure, while EF is preserved because contractility is untouched.", "kind": "literal", "quote": "'" }, { "start": 57269, "end": 57283, "text": "EF preserved", "kind": "literal", "quote": "'" }, { "start": 57294, "end": 57351, "text": "Frank–Starling descent; classic haemorrhage physiology.", "kind": "literal", "quote": "'" }, { "start": 57365, "end": 57527, "text": "Everything hinges on preload. Less filling → the loop starts further left on the EDPVR → smaller stroke volume by the Frank–Starling mechanism.", "kind": "literal", "quote": "'" }, { "start": 57538, "end": 57691, "text": "Because ESPVR (contractility) is unchanged, ejection fraction stays normal even as output falls. EF is a poor marker of volume status.", "kind": "literal", "quote": "'" }, { "start": 57700, "end": 57855, "text": "
Bedside link: this is the loop of a fluid-responsive patient. Give volume and the loop climbs back up the Starling curve.
", "kind": "literal", "quote": "`" }, { "start": 57872, "end": 57895, "text": "Dobutamine / inotrope", "kind": "literal", "quote": "'" }, { "start": 57902, "end": 57925, "text": "Inotrope (dobutamine)", "kind": "literal", "quote": "'" }, { "start": 57932, "end": 57954, "text": "Stage 1 · Physiology", "kind": "literal", "quote": "'" }, { "start": 57959, "end": 57987, "text": "Steeper ESPVR, smaller ESV", "kind": "literal", "quote": "'" }, { "start": 57998, "end": 58168, "text": "An inotrope steepens the ESPVR: the ventricle empties to a smaller end-systolic volume at the same afterload, so SV and EF rise. Mild vasodilation lowers afterload too.", "kind": "literal", "quote": "'" }, { "start": 58212, "end": 58281, "text": "β1-agonism; ESPVR slope as load-independent inotropy (Suga–Sagawa).", "kind": "literal", "quote": "'" }, { "start": 58295, "end": 58475, "text": "Inotropes act on the ESPVR slope. A steeper line means the same end-systolic pressure is reached at a much smaller volume. The ventricle empties more completely.", "kind": "literal", "quote": "'" }, { "start": 58486, "end": 58651, "text": "The result is a taller, wider loop with a low ESV. Efficiency improves, but at a real cost the loop does not show: myocardial oxygen demand rises.", "kind": "literal", "quote": "'" }, { "start": 58660, "end": 58797, "text": "
Contrast with preload: a fluid bolus moves you along a fixed ESPVR; an inotrope tilts the ESPVR itself.
", "kind": "literal", "quote": "`" }, { "start": 58816, "end": 58841, "text": "Pure afterload increase", "kind": "literal", "quote": "'" }, { "start": 58848, "end": 58879, "text": "Vasoconstriction (↑afterload)", "kind": "literal", "quote": "'" }, { "start": 58886, "end": 58908, "text": "Stage 1 · Physiology", "kind": "literal", "quote": "'" }, { "start": 58913, "end": 58930, "text": "Tall and narrow", "kind": "literal", "quote": "'" }, { "start": 58941, "end": 59123, "text": "Raising afterload alone (vasopressor, hypertension) tilts Ea steeper. The aortic valve opens later and closes sooner, so ESV climbs and SV falls. The loop grows taller but narrows.", "kind": "literal", "quote": "'" }, { "start": 59165, "end": 59225, "text": "Afterload sensitivity; steeper Ea reduces SV at fixed Ees.", "kind": "literal", "quote": "'" }, { "start": 59239, "end": 59447, "text": "Afterload is the diagonal Ea line. Steepen it and the loop must reach a higher pressure to eject. The aortic valve opens later, and the loop closes at a higher end-systolic volume.", "kind": "literal", "quote": "'" }, { "start": 59458, "end": 59590, "text": "Net effect: taller, narrower loop, lower stroke volume. The failing ventricle is far more afterload-sensitive than the normal one.", "kind": "literal", "quote": "'" }, { "start": 59599, "end": 59724, "text": "
Coupling shifts up: Ea/Ees rises. Push it far enough and the heart uncouples from its load.
", "kind": "literal", "quote": "`" }, { "start": 59743, "end": 59779, "text": "Vasodilation / afterload reduction", "kind": "literal", "quote": "'" }, { "start": 59786, "end": 59812, "text": "Vasodilator (↓afterload)", "kind": "literal", "quote": "'" }, { "start": 59819, "end": 59841, "text": "Stage 1 · Physiology", "kind": "literal", "quote": "'" }, { "start": 59846, "end": 59865, "text": "Wider, lower loop", "kind": "literal", "quote": "'" }, { "start": 59876, "end": 60026, "text": "Lowering afterload flattens Ea. The valve opens earlier, ESV falls, and SV rises. This is the mechanism behind afterload reduction in heart failure.", "kind": "literal", "quote": "'" }, { "start": 60068, "end": 60131, "text": "Vasodilator therapy in HFrEF; afterload-reduction physiology.", "kind": "literal", "quote": "'" }, { "start": 60145, "end": 60274, "text": "Drop the afterload and the ventricle empties more completely: lower ESV, larger SV. The loop widens and drops.", "kind": "literal", "quote": "'" }, { "start": 60285, "end": 60427, "text": "This is why afterload reduction helps the failing heart so much more than the normal one. A flat, weak ESPVR is very sensitive to afterload.", "kind": "literal", "quote": "'" }, { "start": 60436, "end": 60578, "text": "
Load a failing preset, then reduce MAP: watch SV jump. Now do the same on the normal heart. It barely moves.
", "kind": "literal", "quote": "`" }, { "start": 60593, "end": 60614, "text": "Systolic HF (HFrEF)", "kind": "literal", "quote": "'" }, { "start": 60621, "end": 60642, "text": "Systolic HF · HFrEF", "kind": "literal", "quote": "'" }, { "start": 60649, "end": 60674, "text": "Stage 2 · Heart failure", "kind": "literal", "quote": "'" }, { "start": 60679, "end": 60706, "text": "Flat, wide, shifted right", "kind": "literal", "quote": "'" }, { "start": 60717, "end": 60898, "text": "The defining lesion is a flattened ESPVR (low Ees). The ventricle dilates to compensate (Frank–Starling), so EDV rises but SV and EF fall. Coupling is badly deranged (Ea/Ees ≫ 1).", "kind": "literal", "quote": "'" }, { "start": 60946, "end": 61042, "text": "Guideline HFrEF (EF ≤40%). Eccentric remodelling flattens and shifts the ESPVR. Burkhoff 2005.", "kind": "literal", "quote": "'" }, { "start": 61056, "end": 61242, "text": "HFrEF is a contractility problem: the ESPVR flattens. The ventricle cannot generate pressure, so it dilates to keep stroke volume up. The loop shifts far to the right.", "kind": "literal", "quote": "'" }, { "start": 61253, "end": 61468, "text": "EDV rises but ESV rises more, so ejection fraction falls below 40%. Chronic eccentric remodelling makes the chamber more compliant, which is why filling pressure stays survivable despite the large volume.", "kind": "literal", "quote": "'" }, { "start": 61477, "end": 61622, "text": "
Why afterload reduction works: with a flat ESPVR, a small drop in Ea buys a large gain in SV. Try lowering MAP.
", "kind": "literal", "quote": "`" }, { "start": 61639, "end": 61661, "text": "Diastolic HF (HFpEF)", "kind": "literal", "quote": "'" }, { "start": 61668, "end": 61690, "text": "Diastolic HF · HFpEF", "kind": "literal", "quote": "'" }, { "start": 61697, "end": 61722, "text": "Stage 2 · Heart failure", "kind": "literal", "quote": "'" }, { "start": 61727, "end": 61753, "text": "Narrow loop, steep floor", "kind": "literal", "quote": "'" }, { "start": 61764, "end": 61940, "text": "A stiff ventricle (steep EDPVR) cannot fill at normal pressure. EF is preserved but the loop is small and end-diastolic pressure is high. This is congestion with a normal EF.", "kind": "literal", "quote": "'" }, { "start": 61992, "end": 62076, "text": "HFpEF (EF ≥50%). Steep EDPVR and raised filling pressure. Zile 2004; Borlaug 2020.", "kind": "literal", "quote": "'" }, { "start": 62090, "end": 62239, "text": "HFpEF is a filling problem. The EDPVR is steep and shifted up, so end-diastolic pressure is high even though the chamber is small.", "kind": "literal", "quote": "'" }, { "start": 62250, "end": 62443, "text": "Systolic function (ESPVR) is intact, so ejection fraction stays ≥50%, which is exactly why the diagnosis is missed. The pathology lives on the bottom border of the loop, not the top.", "kind": "literal", "quote": "'" }, { "start": 62452, "end": 62624, "text": "
Toggle the EDPVR overlay: the steep exponential floor is the whole disease. High LVEDP → high left-atrial pressure → pulmonary congestion.
", "kind": "literal", "quote": "`" }, { "start": 62641, "end": 62660, "text": "Cardiogenic shock", "kind": "literal", "quote": "'" }, { "start": 62667, "end": 62686, "text": "Cardiogenic shock", "kind": "literal", "quote": "'" }, { "start": 62693, "end": 62718, "text": "Stage 2 · Heart failure", "kind": "literal", "quote": "'" }, { "start": 62723, "end": 62753, "text": "Collapsed loop, low pressure", "kind": "literal", "quote": "'" }, { "start": 62764, "end": 62951, "text": "End-stage pump failure: a nearly flat ESPVR with hypotension. Output and pressure fall together, the loop collapses, and Ea/Ees is extreme. This is the substrate for mechanical support.", "kind": "literal", "quote": "'" }, { "start": 63002, "end": 63069, "text": "SCAI shock stages; substrate for Impella/ECMO. DanGer Shock 2024.", "kind": "literal", "quote": "'" }, { "start": 63083, "end": 63258, "text": "Cardiogenic shock is HFrEF taken to the edge: a nearly flat ESPVR plus hypotension. Cardiac output and blood pressure fall together, and the loop collapses.", "kind": "literal", "quote": "'" }, { "start": 63269, "end": 63460, "text": "Ventriculo-arterial coupling is severely deranged. The ventricle can no longer match its load. This is the physiologic substrate where mechanical circulatory support is considered.", "kind": "literal", "quote": "'" }, { "start": 63469, "end": 63636, "text": "
Now layer on a device: select Impella and watch the loop shrink and unload; select VA-ECMO and watch afterload and LV pressure climb.
", "kind": "literal", "quote": "`" }, { "start": 63651, "end": 63679, "text": "Restrictive cardiomyopathy", "kind": "literal", "quote": "'" }, { "start": 63686, "end": 63702, "text": "Restrictive CM", "kind": "literal", "quote": "'" }, { "start": 63709, "end": 63735, "text": "Stage 2 · Cardiomyopathy", "kind": "literal", "quote": "'" }, { "start": 63740, "end": 63763, "text": "Tiny, very stiff loop", "kind": "literal", "quote": "'" }, { "start": 63774, "end": 63963, "text": "Extreme diastolic stiffness (amyloid, fibrosis) with a small chamber. Systolic function is relatively preserved but filling is choked, giving a small loop with very high filling pressure.", "kind": "literal", "quote": "'" }, { "start": 63987, "end": 63998, "text": "small EDV", "kind": "literal", "quote": "'" }, { "start": 64019, "end": 64094, "text": "Infiltrative/restrictive physiology; steepest EDPVR. Cardiac amyloidosis.", "kind": "literal", "quote": "'" }, { "start": 64108, "end": 64281, "text": "Restrictive cardiomyopathy is HFpEF's severe cousin: an extremely steep EDPVR in a small, non-compliant chamber. Filling stops abruptly at high pressure.", "kind": "literal", "quote": "'" }, { "start": 64292, "end": 64474, "text": "The loop is small and tall-floored. EF can look near-normal, masking a ventricle that physically cannot accept volume. This is the hallmark of infiltrative disease such as amyloid.", "kind": "literal", "quote": "'" }, { "start": 64483, "end": 64687, "text": "
Distinguish from constriction: restriction is a myocardial stiffness problem (this loop); constriction is a pericardial constraint the LV-only model can only approximate.
", "kind": "literal", "quote": "`" }, { "start": 64702, "end": 64731, "text": "Hypertrophic cardiomyopathy", "kind": "literal", "quote": "'" }, { "start": 64738, "end": 64755, "text": "Hypertrophic CM", "kind": "literal", "quote": "'" }, { "start": 64762, "end": 64788, "text": "Stage 2 · Cardiomyopathy", "kind": "literal", "quote": "'" }, { "start": 64793, "end": 64821, "text": "Hyperdynamic, small cavity", "kind": "literal", "quote": "'" }, { "start": 64832, "end": 65023, "text": "A thick, hypercontractile ventricle with a small, stiff cavity. ESPVR is steep (high EF, near-empty at end-systole) but the EDPVR is stiff. Dynamic outflow obstruction is not captured here.", "kind": "literal", "quote": "'" }, { "start": 65044, "end": 65058, "text": "small cavity", "kind": "literal", "quote": "'" }, { "start": 65078, "end": 65168, "text": "Sarcomeric HCM; hyperdynamic with diastolic dysfunction. Mavacamten (EXPLORER-HCM 2020).", "kind": "literal", "quote": "'" }, { "start": 65182, "end": 65347, "text": "HCM gives a hyperdynamic, small-cavity loop: a steep ESPVR empties the ventricle almost completely (high EF), while a stiff EDPVR impairs filling.", "kind": "literal", "quote": "'" }, { "start": 65358, "end": 65561, "text": "The main clinical problem, dynamic LVOT obstruction, depends on flow, geometry and SAM, which a lumped single-chamber model cannot represent. Read this loop as the substrate, not the gradient.", "kind": "literal", "quote": "'" }, { "start": 65570, "end": 65718, "text": "
Myosin inhibitors (mavacamten) deliberately lower Ees to relieve obstruction. This is the opposite of an inotrope.
", "kind": "literal", "quote": "`" }, { "start": 65738, "end": 65766, "text": "Hypertensive heart disease", "kind": "literal", "quote": "'" }, { "start": 65773, "end": 65793, "text": "Hypertensive heart", "kind": "literal", "quote": "'" }, { "start": 65800, "end": 65826, "text": "Stage 2 · Cardiomyopathy", "kind": "literal", "quote": "'" }, { "start": 65831, "end": 65857, "text": "Tall loop, high pressure", "kind": "literal", "quote": "'" }, { "start": 65868, "end": 66033, "text": "Chronic pressure overload: high afterload with concentric hypertrophy that stiffens the EDPVR. EF is preserved early; peak pressures are high and the loop is tall.", "kind": "literal", "quote": "'" }, { "start": 66059, "end": 66075, "text": "concentric LVH", "kind": "literal", "quote": "'" }, { "start": 66095, "end": 66158, "text": "Pressure-overload concentric remodelling; precursor to HFpEF.", "kind": "literal", "quote": "'" }, { "start": 66172, "end": 66359, "text": "Sustained hypertension is chronic afterload overload. The ventricle answers with concentric hypertrophy: thicker walls that generate high pressure but stiffen diastole.", "kind": "literal", "quote": "'" }, { "start": 66370, "end": 66507, "text": "Early on EF is preserved and the loop is simply tall. Over years the stiff EDPVR dominates and the picture converges on HFpEF.", "kind": "literal", "quote": "'" }, { "start": 66516, "end": 66653, "text": "
The through-line: hypertensive heart → concentric LVH → HFpEF is one continuous EDPVR-steepening story.
", "kind": "literal", "quote": "`" }, { "start": 66668, "end": 66685, "text": "Aortic stenosis", "kind": "literal", "quote": "'" }, { "start": 66692, "end": 66714, "text": "Aortic stenosis (AS)", "kind": "literal", "quote": "'" }, { "start": 66721, "end": 66741, "text": "Stage 3 · Valvular", "kind": "literal", "quote": "'" }, { "start": 66746, "end": 66773, "text": "Tall loop, LV≫Ao pressure", "kind": "literal", "quote": "'" }, { "start": 66784, "end": 67003, "text": "A fixed obstruction the ventricle must overcome. Peak LV pressure rises far above aortic pressure. That difference is the trans-valvular gradient. The loop becomes tall and pressure-loaded with concentric hypertrophy.", "kind": "literal", "quote": "'" }, { "start": 67016, "end": 67029, "text": "peak LVP≫Ao", "kind": "literal", "quote": "'" }, { "start": 67042, "end": 67058, "text": "concentric LVH", "kind": "literal", "quote": "'" }, { "start": 67069, "end": 67159, "text": "Severe AS (Vmax ≥4 m/s, AVA ≤1 cm²). Class I for AVR when symptomatic. 2020 ACC/AHA VHD.", "kind": "literal", "quote": "'" }, { "start": 67173, "end": 67350, "text": "AS is an outflow obstruction. The ventricle generates a much higher pressure than the aorta ever sees. The difference is the trans-valvular gradient.", "kind": "literal", "quote": "'" }, { "start": 67361, "end": 67591, "text": "Toggle Peak LV pressure and Aortic pressure lines: the gap between them is the gradient, and it is the whole disease. Chronic pressure overload drives concentric hypertrophy and a stiffer EDPVR.", "kind": "literal", "quote": "'" }, { "start": 67600, "end": 67775, "text": "
Why this matters: in every other condition here, peak LVP ≈ aortic SBP. AS is the exception, and that gap is what a valve replacement erases.
", "kind": "literal", "quote": "`" }, { "start": 67789, "end": 67819, "text": "Chronic aortic regurgitation", "kind": "literal", "quote": "'" }, { "start": 67826, "end": 67851, "text": "Aortic regurg · chronic", "kind": "literal", "quote": "'" }, { "start": 67858, "end": 67878, "text": "Stage 3 · Valvular", "kind": "literal", "quote": "'" }, { "start": 67883, "end": 67909, "text": "Huge, wide loop, low DBP", "kind": "literal", "quote": "'" }, { "start": 67920, "end": 68108, "text": "Diastolic backflow volume-overloads the ventricle. It dilates eccentrically to accommodate a very large total stroke volume, with a wide pulse pressure and low aortic diastolic pressure.", "kind": "literal", "quote": "'" }, { "start": 68129, "end": 68138, "text": "wide PP", "kind": "literal", "quote": "'" }, { "start": 68139, "end": 68148, "text": "low DBP", "kind": "literal", "quote": "'" }, { "start": 68159, "end": 68246, "text": "Chronic severe AR; eccentric remodelling. AVR by LVESD/EF criteria. 2020 ACC/AHA VHD.", "kind": "literal", "quote": "'" }, { "start": 68260, "end": 68445, "text": "In aortic regurgitation, blood leaks back into the ventricle during diastole. The loop loses its clean isovolumic relaxation. Volume keeps entering as pressure falls.", "kind": "literal", "quote": "'" }, { "start": 68456, "end": 68692, "text": "Chronic AR gives the heart time to dilate eccentrically, so it carries a huge total stroke volume at survivable filling pressure. The runoff back through the valve drops aortic diastolic pressure, widening the pulse pressure.", "kind": "literal", "quote": "'" }, { "start": 68701, "end": 68867, "text": "
Compare with acute AR: same leak, but no time to remodel. The small stiff ventricle raises its filling pressure instead of dilating.
", "kind": "literal", "quote": "`" }, { "start": 68886, "end": 68914, "text": "Acute aortic regurgitation", "kind": "literal", "quote": "'" }, { "start": 68921, "end": 68944, "text": "Aortic regurg · acute", "kind": "literal", "quote": "'" }, { "start": 68951, "end": 68971, "text": "Stage 3 · Valvular", "kind": "literal", "quote": "'" }, { "start": 68976, "end": 69001, "text": "Normal-size LV, ↑↑LVEDP", "kind": "literal", "quote": "'" }, { "start": 69012, "end": 69207, "text": "A sudden severe leak (endocarditis, dissection) into a normal, non-dilated ventricle. It cannot accommodate the volume, so LV end-diastolic pressure rises sharply. This is a surgical emergency.", "kind": "literal", "quote": "'" }, { "start": 69266, "end": 69334, "text": "Acute severe AR: surgical emergency; premature MV closure on echo.", "kind": "literal", "quote": "'" }, { "start": 69348, "end": 69524, "text": "Acute AR is a different disease from the chronic form. The leak is just as severe, but the ventricle is normal-sized and stiff. It has had no time to dilate.", "kind": "literal", "quote": "'" }, { "start": 69535, "end": 69716, "text": "Unable to accommodate the regurgitant volume, end-diastolic pressure rises steeply. Clinically this can slam the mitral valve shut early and cause flash pulmonary oedema.", "kind": "literal", "quote": "'" }, { "start": 69725, "end": 69888, "text": "
Chronic vs acute is the exam favourite: same lesion, opposite loops, because remodelling either had time to happen or it did not.
", "kind": "literal", "quote": "`" }, { "start": 69902, "end": 69919, "text": "Mitral stenosis", "kind": "literal", "quote": "'" }, { "start": 69926, "end": 69948, "text": "Mitral stenosis (MS)", "kind": "literal", "quote": "'" }, { "start": 69955, "end": 69975, "text": "Stage 3 · Valvular", "kind": "literal", "quote": "'" }, { "start": 69980, "end": 70006, "text": "Small loop, shifted left", "kind": "literal", "quote": "'" }, { "start": 70017, "end": 70207, "text": "The obstruction is at inflow, upstream of the ventricle. The LV underfills, so SV falls, but LV systolic function and EF are preserved. The pressure and the problem are in the left atrium.", "kind": "literal", "quote": "'" }, { "start": 70254, "end": 70330, "text": "Rheumatic MS; gradient across MV → ↑LAP/PCWP. Balloon valvuloplasty / MVR.", "kind": "literal", "quote": "'" }, { "start": 70344, "end": 70532, "text": "Mitral stenosis is unique here: the lesion sits upstream of the ventricle. The LV simply cannot fill, so the loop is small and shifted left with a reduced stroke volume.", "kind": "literal", "quote": "'" }, { "start": 70543, "end": 70780, "text": "Crucially, LV contractility and ejection fraction are preserved. The ventricle is normal, it is simply underfilled. The high pressure and the pathology are in the left atrium (↑LAP, ↑PCWP), which this LV-only loop cannot show.", "kind": "literal", "quote": "'" }, { "start": 70789, "end": 70953, "text": "
Reading tip: a small loop with a normal-shaped ESPVR and preserved EF points upstream. Think inflow obstruction, not pump failure.
", "kind": "literal", "quote": "`" }, { "start": 70968, "end": 70998, "text": "Chronic mitral regurgitation", "kind": "literal", "quote": "'" }, { "start": 71005, "end": 71030, "text": "Mitral regurg · chronic", "kind": "literal", "quote": "'" }, { "start": 71037, "end": 71057, "text": "Stage 3 · Valvular", "kind": "literal", "quote": "'" }, { "start": 71062, "end": 71095, "text": "Wide loop, no isovolumic phases", "kind": "literal", "quote": "'" }, { "start": 71106, "end": 71301, "text": "Systolic backflow into the low-pressure atrium. The ventricle ejects the moment pressure exceeds atrial pressure, so isovolumic contraction is lost. EF looks high but forward output is reduced.", "kind": "literal", "quote": "'" }, { "start": 71314, "end": 71327, "text": "no true IVC", "kind": "literal", "quote": "'" }, { "start": 71335, "end": 71349, "text": "deceptive EF", "kind": "literal", "quote": "'" }, { "start": 71360, "end": 71451, "text": "Chronic primary MR; EF overstates function. Repair is preferred to replacement. 2020 VHD.", "kind": "literal", "quote": "'" }, { "start": 71465, "end": 71717, "text": "In MR the ventricle has a low-pressure escape route into the left atrium. It starts ejecting as soon as LV pressure passes atrial pressure, so there is no true isovolumic contraction. The top-left corner of the loop is gone.", "kind": "literal", "quote": "'" }, { "start": 71728, "end": 71927, "text": "Because part of the ejection is backward, EF overstates real function: a \"normal\" EF of 65% may hide meaningful systolic impairment. Chronic MR dilates the ventricle eccentrically.", "kind": "literal", "quote": "'" }, { "start": 71936, "end": 72107, "text": "
Surgical trap: after repair, EF often falls. The low-pressure escape route is gone and true function is unmasked. Operate before EF <60%.
", "kind": "literal", "quote": "`" }, { "start": 72126, "end": 72154, "text": "Acute mitral regurgitation", "kind": "literal", "quote": "'" }, { "start": 72161, "end": 72184, "text": "Mitral regurg · acute", "kind": "literal", "quote": "'" }, { "start": 72191, "end": 72211, "text": "Stage 3 · Valvular", "kind": "literal", "quote": "'" }, { "start": 72216, "end": 72242, "text": "Non-dilated LV, high LAP", "kind": "literal", "quote": "'" }, { "start": 72253, "end": 72479, "text": "A sudden leak (papillary muscle rupture, chordal rupture) into a normal-sized, stiff atrium. Forward output crashes and left atrial and PCWP pressures rise sharply. The result is cardiogenic shock and flash pulmonary oedema.", "kind": "literal", "quote": "'" }, { "start": 72532, "end": 72611, "text": "Acute severe MR: papillary rupture after MI; giant v-waves. Emergent surgery.", "kind": "literal", "quote": "'" }, { "start": 72625, "end": 72807, "text": "Acute MR is the emergency form: the leak hits a normal, non-compliant left atrium. Pressure has nowhere to go, so LA (and PCWP) pressure spikes with giant v-waves.", "kind": "literal", "quote": "'" }, { "start": 72818, "end": 73016, "text": "The ventricle is hyperdynamic and small, but forward output collapses. The picture is flash pulmonary oedema and cardiogenic shock, classically after papillary-muscle rupture in acute MI.", "kind": "literal", "quote": "'" }, { "start": 73025, "end": 73176, "text": "
Same lesion, remodelling makes the loop: chronic MR dilates and compensates; acute MR cannot, and decompensates fast.
", "kind": "literal", "quote": "`" }, { "start": 73197, "end": 73222, "text": "Before TAVR (severe AS)", "kind": "literal", "quote": "'" }, { "start": 73229, "end": 73251, "text": "Pre-TAVR (severe AS)", "kind": "literal", "quote": "'" }, { "start": 73258, "end": 73282, "text": "Stage 5 · Intervention", "kind": "literal", "quote": "'" }, { "start": 73287, "end": 73314, "text": "Tall loop, large gradient", "kind": "literal", "quote": "'" }, { "start": 73342, "end": 73491, "text": "Severe symptomatic AS at the point of intervention: tall pressure-loaded loop, a wide LV–aortic gradient, concentric hypertrophy and a stiff EDPVR.", "kind": "literal", "quote": "'" }, { "start": 73504, "end": 73517, "text": "peak LVP≫Ao", "kind": "literal", "quote": "'" }, { "start": 73555, "end": 73623, "text": "PARTNER / Evolut: TAVR non-inferior to surgery across risk strata.", "kind": "literal", "quote": "'" }, { "start": 73637, "end": 73841, "text": "This is severe aortic stenosis just before valve replacement. The ventricle is generating a large gradient to force blood through a fixed orifice, with concentric hypertrophy behind it.", "kind": "literal", "quote": "'" }, { "start": 73852, "end": 74006, "text": "Switch to After TAVR to watch the intervention: the gradient collapses, afterload falls, and the loop widens as forward stroke volume recovers.", "kind": "literal", "quote": "'" }, { "start": 74015, "end": 74176, "text": "
Watch peak LVP: before, it towers over aortic pressure; after, they converge. That collapse is the entire haemodynamic benefit.
", "kind": "literal", "quote": "`" }, { "start": 74197, "end": 74209, "text": "After TAVR", "kind": "literal", "quote": "'" }, { "start": 74234, "end": 74258, "text": "Stage 5 · Intervention", "kind": "literal", "quote": "'" }, { "start": 74263, "end": 74291, "text": "Gradient gone, loop widens", "kind": "literal", "quote": "'" }, { "start": 74318, "end": 74486, "text": "The orifice is restored. Peak LV pressure now sits at aortic systolic pressure, afterload drops, SV rises, and the loop normalises. Hypertrophy regresses over months.", "kind": "literal", "quote": "'" }, { "start": 74499, "end": 74512, "text": "peak LVP≈Ao", "kind": "literal", "quote": "'" }, { "start": 74542, "end": 74623, "text": "Immediate afterload relief; reverse remodelling over months. PARTNER long-term.", "kind": "literal", "quote": "'" }, { "start": 74637, "end": 74811, "text": "The valve is fixed. Peak LV pressure and aortic systolic pressure are reunited: the gradient is gone. The abrupt fall in afterload lets stroke volume rise.", "kind": "literal", "quote": "'" }, { "start": 74822, "end": 75001, "text": "Toggle back to Before TAVR to see the contrast. The concentric hypertrophy and stiff EDPVR take months to regress, so filling pressure improves more slowly than output.", "kind": "literal", "quote": "'" }, { "start": 75010, "end": 75172, "text": "
Occasional paradox: EF can dip transiently after relief, unmasking systolic dysfunction the high afterload had been propping up.
", "kind": "literal", "quote": "`" }, { "start": 75191, "end": 75222, "text": "Before MV surgery (severe MR)", "kind": "literal", "quote": "'" }, { "start": 75229, "end": 75250, "text": "Pre-MVR (severe MR)", "kind": "literal", "quote": "'" }, { "start": 75257, "end": 75281, "text": "Stage 5 · Intervention", "kind": "literal", "quote": "'" }, { "start": 75286, "end": 75311, "text": "Wide loop, deceptive EF", "kind": "literal", "quote": "'" }, { "start": 75338, "end": 75519, "text": "Severe chronic MR at the point of surgery: a dilated ventricle with a wide loop, high total SV, and an EF that flatters true function because of the low-pressure regurgitant path.", "kind": "literal", "quote": "'" }, { "start": 75540, "end": 75548, "text": "no IVC", "kind": "literal", "quote": "'" }, { "start": 75549, "end": 75563, "text": "EF flattered", "kind": "literal", "quote": "'" }, { "start": 75574, "end": 75644, "text": "Primary MR: repair before EF <60% or LVESD >40 mm. 2020 ACC/AHA VHD.", "kind": "literal", "quote": "'" }, { "start": 75658, "end": 75804, "text": "Severe chronic MR just before surgery: dilated ventricle, wide loop, no isovolumic contraction, and a deceptively preserved EF.", "kind": "literal", "quote": "'" }, { "start": 75815, "end": 76006, "text": "Switch to After MV surgery. Restoring valve competence removes the backward escape. End-diastolic volume falls and true function is revealed, sometimes with a lower EF than before.", "kind": "literal", "quote": "'" }, { "start": 76015, "end": 76174, "text": "
Timing is everything: operate while EF is still ≥60% and LVESD <40 mm, before irreversible dysfunction hides behind the leak.
", "kind": "literal", "quote": "`" }, { "start": 76194, "end": 76212, "text": "After MV surgery", "kind": "literal", "quote": "'" }, { "start": 76236, "end": 76260, "text": "Stage 5 · Intervention", "kind": "literal", "quote": "'" }, { "start": 76265, "end": 76292, "text": "IVC restored, EF unmasked", "kind": "literal", "quote": "'" }, { "start": 76318, "end": 76489, "text": "Valve competence restored: isovolumic contraction returns, end-diastolic volume falls, forward output improves, and EF often drops as true systolic function is unmasked.", "kind": "literal", "quote": "'" }, { "start": 76502, "end": 76515, "text": "IVC returns", "kind": "literal", "quote": "'" }, { "start": 76523, "end": 76532, "text": "true EF", "kind": "literal", "quote": "'" }, { "start": 76543, "end": 76609, "text": "Post-repair EF fall is expected. The low-impedance leak is gone.", "kind": "literal", "quote": "'" }, { "start": 76623, "end": 76788, "text": "The valve is competent again. The top-left corner of the loop, isovolumic contraction, reappears, and the dilated ventricle shrinks toward normal.", "kind": "literal", "quote": "'" }, { "start": 76799, "end": 76995, "text": "Forward stroke volume improves, but EF may fall: without the low-pressure escape route, the ventricle's real contractile state shows through. That drop is expected, not a complication.", "kind": "literal", "quote": "'" }, { "start": 77004, "end": 77126, "text": "
Repair beats replacement for long-term LV function whenever the valve anatomy allows it.
", "kind": "literal", "quote": "`" }, { "start": 77146, "end": 77173, "text": "Before CRT (LBBB + HFrEF)", "kind": "literal", "quote": "'" }, { "start": 77180, "end": 77204, "text": "Pre-CRT (dyssynchrony)", "kind": "literal", "quote": "'" }, { "start": 77211, "end": 77235, "text": "Stage 5 · Intervention", "kind": "literal", "quote": "'" }, { "start": 77240, "end": 77267, "text": "Wide, flat, wasteful loop", "kind": "literal", "quote": "'" }, { "start": 77295, "end": 77449, "text": "Dyssynchronous HFrEF: left bundle branch block makes the septum and free wall contract out of phase, wasting work as functional MR and a low, flat loop.", "kind": "literal", "quote": "'" }, { "start": 77469, "end": 77484, "text": "functional MR", "kind": "literal", "quote": "'" }, { "start": 77485, "end": 77495, "text": "wide QRS", "kind": "literal", "quote": "'" }, { "start": 77506, "end": 77584, "text": "CRT for EF ≤35%, LBBB, QRS ≥150 ms. MADIT-CRT; about 30% are non-responders.", "kind": "literal", "quote": "'" }, { "start": 77598, "end": 77812, "text": "In LBBB, the ventricle contracts out of sequence. The septum fires early and the free wall late. Force is wasted stretching still-relaxed segments rather than ejecting, and functional MR appears.", "kind": "literal", "quote": "'" }, { "start": 77823, "end": 78046, "text": "The loop is wide, flat and inefficient. Switch to After CRT to resynchronise: biventricular pacing recovers coordinated contraction, effectively raising functional contractility without any drug.", "kind": "literal", "quote": "'" }, { "start": 78055, "end": 78200, "text": "
CRT is mechanical, not pharmacologic: it fixes timing. Best responders have EF ≤35%, true LBBB and QRS ≥150 ms.
", "kind": "literal", "quote": "`" }, { "start": 78221, "end": 78232, "text": "After CRT", "kind": "literal", "quote": "'" }, { "start": 78239, "end": 78266, "text": "Post-CRT (resynchronised)", "kind": "literal", "quote": "'" }, { "start": 78273, "end": 78297, "text": "Stage 5 · Intervention", "kind": "literal", "quote": "'" }, { "start": 78302, "end": 78326, "text": "Loop lifts and narrows", "kind": "literal", "quote": "'" }, { "start": 78353, "end": 78535, "text": "Biventricular pacing restores synchronous contraction: functional contractility rises, functional MR falls, and the loop lifts and narrows. Reverse remodelling follows over months.", "kind": "literal", "quote": "'" }, { "start": 78548, "end": 78565, "text": "↑functional Ees", "kind": "literal", "quote": "'" }, { "start": 78572, "end": 78589, "text": "reverse remodel", "kind": "literal", "quote": "'" }, { "start": 78600, "end": 78676, "text": "Acute resynchronisation + chronic reverse remodelling. CARE-HF, MADIT-CRT.", "kind": "literal", "quote": "'" }, { "start": 78690, "end": 78892, "text": "Resynchronisation recoordinates the contraction. Functional contractility rises, functional MR falls, and the loop lifts and narrows. There is more stroke volume for less wasted work.", "kind": "literal", "quote": "'" }, { "start": 78903, "end": 79095, "text": "The acute benefit is immediate; reverse remodelling then shrinks the ventricle over 3–6 months. Compare with Before CRT to see both the height gain and the width reduction.", "kind": "literal", "quote": "'" }, { "start": 79104, "end": 79236, "text": "
~30% of patients are non-responders. Patient selection by QRS morphology and duration is critical.
", "kind": "literal", "quote": "`" }, { "start": 79276, "end": 79288, "text": "Physiology", "kind": "literal", "quote": "'" }, { "start": 79373, "end": 79405, "text": "Heart failure & cardiomyopathy", "kind": "literal", "quote": "'" }, { "start": 79479, "end": 79497, "text": "Valvular disease", "kind": "literal", "quote": "'" }, { "start": 79575, "end": 79607, "text": "Interventions · before → after", "kind": "literal", "quote": "'" }, { "start": 81511, "end": 81520, "text": "Impella", "kind": "literal", "quote": "'" }, { "start": 82012, "end": 82030, "text": "Pin a loop first", "kind": "literal", "quote": "'" }, { "start": 82152, "end": 82166, "text": "Normal heart", "kind": "literal", "quote": "'" }, { "start": 82237, "end": 82247, "text": "Without ", "kind": "literal", "quote": "'" }, { "start": 82395, "end": 82413, "text": "Before treatment", "kind": "literal", "quote": "'" }, { "start": 82508, "end": 82518, "text": "Pinned: ", "kind": "literal", "quote": "'" }, { "start": 82761, "end": 82783, "text": "", "kind": "literal", "quote": "'" }, { "start": 82847, "end": 82862, "text": "Dotted loop: ", "kind": "literal", "quote": "'" }, { "start": 82886, "end": 82912, "text": "No reference loop shown.", "kind": "literal", "quote": "'" }, { "start": 83206, "end": 83219, "text": "", "kind": "tail", "quote": "}" }, { "start": 83360, "end": 83373, "text": "", "kind": "tail", "quote": "}" }, { "start": 83963, "end": 83983, "text": "", "kind": "tail", "quote": "}" }, { "start": 84109, "end": 84121, "text": "", "kind": "tail", "quote": "}" }, { "start": 84366, "end": 84387, "text": "", "kind": "tail", "quote": "}" }, { "start": 84576, "end": 84588, "text": "EDPVR", "kind": "tail", "quote": "}" }, { "start": 84826, "end": 84839, "text": "", "kind": "tail", "quote": "}" }, { "start": 84996, "end": 85008, "text": "ESPVR · Ees ", "kind": "middle", "quote": "}" }, { "start": 85214, "end": 85227, "text": "", "kind": "tail", "quote": "}" }, { "start": 85378, "end": 85390, "text": "Ea ", "kind": "middle", "quote": "}" }, { "start": 85594, "end": 85607, "text": "", "kind": "tail", "quote": "}" }, { "start": 85768, "end": 85780, "text": "", "kind": "tail", "quote": "}" }, { "start": 86089, "end": 86101, "text": "", "kind": "tail", "quote": "}" }, { "start": 86455, "end": 86467, "text": "peak LVP ", "kind": "middle", "quote": "}" }, { "start": 86645, "end": 86657, "text": "", "kind": "tail", "quote": "}" }, { "start": 86822, "end": 86834, "text": "", "kind": "tail", "quote": "}" }, { "start": 87394, "end": 87407, "text": "", "kind": "tail", "quote": "}" }, { "start": 87536, "end": 87551, "text": "", "kind": "tail", "quote": "}" }, { "start": 87647, "end": 87659, "text": "", "kind": "middle", "quote": "}" }, { "start": 87824, "end": 87837, "text": "", "kind": "tail", "quote": "}" }, { "start": 87960, "end": 87973, "text": "", "kind": "tail", "quote": "}" }, { "start": 88108, "end": 88120, "text": "", "kind": "middle", "quote": "}" }, { "start": 88239, "end": 88251, "text": "", "kind": "middle", "quote": "}" }, { "start": 88335, "end": 88347, "text": "LV volume (mL)", "kind": "tail", "quote": "}" }, { "start": 88453, "end": 88486, "text": "LV pressure (mmHg)", "kind": "tail", "quote": "}" }, { "start": 88646, "end": 88698, "text": "", "kind": "tail", "quote": "}" }, { "start": 88758, "end": 88795, "text": "", "kind": "tail", "quote": "}" }, { "start": 89521, "end": 89542, "text": "", "kind": "tail", "quote": "}" }, { "start": 89961, "end": 89983, "text": "", "kind": "tail", "quote": "}" }, { "start": 90115, "end": 90127, "text": "", "kind": "tail", "quote": "}" }, { "start": 90651, "end": 90663, "text": "LVP ", "kind": "middle", "quote": "}" }, { "start": 92996, "end": 93023, "text": "   LV pressure ", "kind": "middle", "quote": "}" }, { "start": 93041, "end": 93071, "text": " mmHg  ·  volume ", "kind": "middle", "quote": "}" }, { "start": 93089, "end": 93117, "text": " mL  ·  aortic ", "kind": "middle", "quote": "}" }, { "start": 93136, "end": 93143, "text": " mmHg", "kind": "tail", "quote": "}" }, { "start": 93407, "end": 93493, "text": "Hover the loop to trace pressure, volume and valve events through the cardiac cycle.", "kind": "literal", "quote": "'" }, { "start": 94395, "end": 94435, "text": "", "kind": "literal", "quote": "'" }, { "start": 94436, "end": 94463, "text": "", "kind": "literal", "quote": "'" }, { "start": 94506, "end": 94513, "text": "Pause", "kind": "literal", "quote": "'" }, { "start": 94514, "end": 94533, "text": "Animate the cycle", "kind": "literal", "quote": "'" }, { "start": 100745, "end": 100758, "text": "Orientation", "kind": "literal", "quote": "'" }, { "start": 100765, "end": 100784, "text": "What a PV loop is", "kind": "literal", "quote": "'" }, { "start": 100789, "end": 100839, "text": "One heartbeat, drawn as pressure against volume.", "kind": "literal", "quote": "'" }, { "start": 100857, "end": 100871, "text": "The two axes", "kind": "literal", "quote": "'" }, { "start": 100878, "end": 101081, "text": "Forget time for a moment. A pressure–volume loop plots left-ventricular pressure (y-axis, mmHg) against left-ventricular volume (x-axis, mL) across a single heartbeat.", "kind": "literal", "quote": "'" }, { "start": 101088, "end": 101220, "text": "Because both pressure and volume change continuously, one beat traces out a closed loop. The loop runs counter-clockwise.", "kind": "literal", "quote": "'" }, { "start": 101241, "end": 101263, "text": "Open the normal loop", "kind": "literal", "quote": "'" }, { "start": 101289, "end": 101313, "text": "Width is stroke volume", "kind": "literal", "quote": "'" }, { "start": 101320, "end": 101544, "text": "The loop’s width is the volume ejected each beat, the stroke volume. Its right edge is end-diastolic volume (EDV, the fullest point); its left edge is end-systolic volume (ESV, the emptiest).", "kind": "literal", "quote": "'" }, { "start": 101551, "end": 101671, "text": "Ejection fraction is simply SV ÷ EDV. Everything else on the loop explains why that width is what it is.", "kind": "literal", "quote": "'" }, { "start": 101681, "end": 101695, "text": "Area is work", "kind": "literal", "quote": "'" }, { "start": 101702, "end": 101889, "text": "The area enclosed by the loop is stroke work, the mechanical work the ventricle does on the blood each beat. A tall, wide loop does more work than a small one.", "kind": "literal", "quote": "'" }, { "start": 101896, "end": 101959, "text": "Turn on the stroke-work fill to see the enclosed area shaded.", "kind": "literal", "quote": "'" }, { "start": 101980, "end": 101999, "text": "Shade stroke work", "kind": "literal", "quote": "'" }, { "start": 102048, "end": 102112, "text": "I can point to stroke volume and ejection fraction on the loop", "kind": "literal", "quote": "'" }, { "start": 102113, "end": 102153, "text": "I know the loop runs counter-clockwise", "kind": "literal", "quote": "'" }, { "start": 102172, "end": 102183, "text": "Mechanics", "kind": "literal", "quote": "'" }, { "start": 102190, "end": 102207, "text": "The four phases", "kind": "literal", "quote": "'" }, { "start": 102212, "end": 102290, "text": "Two valves, opening and closing in sequence, carve the loop into four sides.", "kind": "literal", "quote": "'" }, { "start": 102308, "end": 102325, "text": "Follow one beat", "kind": "literal", "quote": "'" }, { "start": 102332, "end": 102433, "text": "Start at the bottom-right corner (end-diastole, mitral valve just closed) and go counter-clockwise:", "kind": "literal", "quote": "'" }, { "start": 102440, "end": 102847, "text": "1 · Isovolumetric contraction: both valves shut, pressure rises straight up, volume fixed. 2 · Ejection: the aortic valve opens, blood leaves, volume falls. 3 · Isovolumetric relaxation: the aortic valve shuts, pressure drops straight down. 4 · Filling: the mitral valve opens, the ventricle refills along the bottom.", "kind": "literal", "quote": "'" }, { "start": 102868, "end": 102893, "text": "Animate the four phases", "kind": "literal", "quote": "'" }, { "start": 102942, "end": 102972, "text": "The corners are valve events", "kind": "literal", "quote": "'" }, { "start": 102979, "end": 103205, "text": "Each corner is a valve opening or closing: ① MV closes (start of contraction), ② AV opens (start of ejection), ③ AV closes (end-systole), ④ MV opens (start of filling).", "kind": "literal", "quote": "'" }, { "start": 103212, "end": 103416, "text": "The two vertical sides are isovolumetric: all valves are closed, so volume can’t change. Keep this in mind: several diseases are defined by which vertical side is missing.", "kind": "literal", "quote": "'" }, { "start": 103426, "end": 103450, "text": "Why counter-clockwise?", "kind": "literal", "quote": "'" }, { "start": 103457, "end": 103649, "text": "Because the ventricle fills at low pressure (bottom), then generates high pressure to eject (top), then relaxes. Energy flows in during systole and the loop closes as it relaxes and refills.", "kind": "literal", "quote": "'" }, { "start": 103664, "end": 103806, "text": "In mitral regurgitation, blood leaks back into the atrium the instant pressure rises, before the aortic valve opens. Which phase disappears?", "kind": "literal", "quote": "'" }, { "start": 103809, "end": 103975, "text": "Isovolumetric contraction. With a hole into the low-pressure atrium, volume starts falling as soon as pressure rises, so the left vertical wall of the loop is lost.", "kind": "literal", "quote": "'" }, { "start": 103989, "end": 104026, "text": "I can name the four phases in order", "kind": "literal", "quote": "'" }, { "start": 104027, "end": 104065, "text": "I know which sides are isovolumetric", "kind": "literal", "quote": "'" }, { "start": 104084, "end": 104096, "text": "Boundaries", "kind": "literal", "quote": "'" }, { "start": 104103, "end": 104120, "text": "The three lines", "kind": "literal", "quote": "'" }, { "start": 104125, "end": 104222, "text": "A loop lives inside a frame of three lines. Learn the frame and every disease becomes readable.", "kind": "literal", "quote": "'" }, { "start": 104240, "end": 104262, "text": "ESPVR: contractility", "kind": "literal", "quote": "'" }, { "start": 104269, "end": 104467, "text": "The end-systolic pressure–volume relationship is the ceiling the loop’s top-left corner rides on. Its slope is Ees, a load-independent measure of contractility.", "kind": "literal", "quote": "'" }, { "start": 104474, "end": 104649, "text": "Steeper ESPVR = stronger heart = the ventricle empties to a smaller volume against the same pressure. Slide contractility and watch the top-left corner track the green line.", "kind": "literal", "quote": "'" }, { "start": 104670, "end": 104682, "text": "Show ESPVR", "kind": "literal", "quote": "'" }, { "start": 104751, "end": 104770, "text": "EDPVR: compliance", "kind": "literal", "quote": "'" }, { "start": 104777, "end": 105041, "text": "The end-diastolic pressure–volume relationship is the curved floor. It is passive: how stiff the ventricle is when it fills. A stiff ventricle (HFpEF, restrictive, hypertrophy) climbs this curve steeply: small volume, high filling pressure.", "kind": "literal", "quote": "'" }, { "start": 105062, "end": 105089, "text": "Compare a stiff ventricle", "kind": "literal", "quote": "'" }, { "start": 105136, "end": 105150, "text": "Ea: the load", "kind": "literal", "quote": "'" }, { "start": 105157, "end": 105419, "text": "The effective arterial elastance line is the diagonal from EDV on the x-axis to the end-systolic corner. It summarises everything the ventricle ejects against (resistance + stiffness of the arterial tree) as one number, Ea = ESP / SV.", "kind": "literal", "quote": "'" }, { "start": 105426, "end": 105596, "text": "Where ESPVR (Ees) meets Ea sets the operating point. Their ratio, Ea/Ees, is ventriculo-arterial coupling, which is optimal near 0.6–1.2.", "kind": "literal", "quote": "'" }, { "start": 105617, "end": 105639, "text": "Show all three lines", "kind": "literal", "quote": "'" }, { "start": 105710, "end": 105745, "text": "ESPVR slope = contractility (Ees)", "kind": "literal", "quote": "'" }, { "start": 105746, "end": 105773, "text": "EDPVR = passive stiffness", "kind": "literal", "quote": "'" }, { "start": 105774, "end": 105804, "text": "Ea = load; Ea/Ees = coupling", "kind": "literal", "quote": "'" }, { "start": 105823, "end": 105831, "text": "Levers", "kind": "literal", "quote": "'" }, { "start": 105838, "end": 105873, "text": "Preload, afterload, contractility", "kind": "literal", "quote": "'" }, { "start": 105878, "end": 105951, "text": "Three independent levers move the loop. Change one at a time and watch.", "kind": "literal", "quote": "'" }, { "start": 105969, "end": 105978, "text": "Preload", "kind": "literal", "quote": "'" }, { "start": 105985, "end": 106205, "text": "Preload is how full the ventricle is before it contracts (EDV). Add preload and the loop’s right edge slides right: more stretch, more stroke volume (the Frank–Starling mechanism), same ESPVR corner.", "kind": "literal", "quote": "'" }, { "start": 106226, "end": 106241, "text": "Raise preload", "kind": "literal", "quote": "'" }, { "start": 106297, "end": 106308, "text": "Afterload", "kind": "literal", "quote": "'" }, { "start": 106315, "end": 106530, "text": "Afterload is the pressure the ventricle must beat against. Raise it and the aortic valve opens later and higher: the loop grows taller and narrower, stroke volume falls, end-systolic volume rises.", "kind": "literal", "quote": "'" }, { "start": 106551, "end": 106568, "text": "Raise afterload", "kind": "literal", "quote": "'" }, { "start": 106595, "end": 106610, "text": "Contractility", "kind": "literal", "quote": "'" }, { "start": 106617, "end": 106833, "text": "Contractility rotates the ESPVR ceiling upward. A stronger heart empties further for the same load: end-systolic volume falls, stroke volume and EF rise. This is the one lever that is truly intrinsic to the muscle.", "kind": "literal", "quote": "'" }, { "start": 106854, "end": 106886, "text": "Add contractility (dobutamine)", "kind": "literal", "quote": "'" }, { "start": 106933, "end": 106947, "text": "Isolate them", "kind": "literal", "quote": "'" }, { "start": 106954, "end": 107152, "text": "The determinant sliders on the simulator move each lever independently, which you cannot do at the bedside. Return to normal, then push one slider at a time and predict the loop before it redraws.", "kind": "literal", "quote": "'" }, { "start": 107167, "end": 107281, "text": "You raise afterload but stroke volume barely changes and EF stays high. What does that tell you about the ESPVR?", "kind": "literal", "quote": "'" }, { "start": 107284, "end": 107481, "text": "The ventricle has strong contractility (steep ESPVR / large contractile reserve). A steep ESPVR is relatively afterload-insensitive; a flat one (failing heart) is exquisitely afterload-sensitive.", "kind": "literal", "quote": "'" }, { "start": 107495, "end": 107541, "text": "Preload → width via Frank–Starling", "kind": "literal", "quote": "'" }, { "start": 107542, "end": 107577, "text": "Afterload → taller, narrower", "kind": "literal", "quote": "'" }, { "start": 107578, "end": 107614, "text": "Contractility → rotates ESPVR", "kind": "literal", "quote": "'" }, { "start": 107633, "end": 107645, "text": "Energetics", "kind": "literal", "quote": "'" }, { "start": 107652, "end": 107681, "text": "Work, oxygen and efficiency", "kind": "literal", "quote": "'" }, { "start": 107686, "end": 107751, "text": "The loop is also an energy diagram, and oxygen is the currency.", "kind": "literal", "quote": "'" }, { "start": 107769, "end": 107793, "text": "PVA predicts MVO₂", "kind": "literal", "quote": "'" }, { "start": 107800, "end": 108061, "text": "The pressure–volume area (PVA) is stroke work plus the potential energy stored in the contracted muscle. Suga showed PVA is linearly related to myocardial oxygen consumption, so the loop predicts how much O₂ the beat costs.", "kind": "literal", "quote": "'" }, { "start": 108082, "end": 108100, "text": "Shade PVA energy", "kind": "literal", "quote": "'" }, { "start": 108153, "end": 108178, "text": "Efficiency and coupling", "kind": "literal", "quote": "'" }, { "start": 108185, "end": 108447, "text": "Efficiency is the fraction of that energy that becomes useful work: SW / PVA. It peaks when Ea/Ees is near 0.6–1.0. A failing heart (flat ESPVR, high Ea) is uncoupled: it spends oxygen on pressure it can’t convert to output.", "kind": "literal", "quote": "'" }, { "start": 108468, "end": 108492, "text": "See an uncoupled heart", "kind": "literal", "quote": "'" }, { "start": 108552, "end": 108573, "text": "Why unloading helps", "kind": "literal", "quote": "'" }, { "start": 108580, "end": 108834, "text": "Anything that lowers PVA lowers oxygen demand: reducing afterload, reducing volume, or mechanically unloading the ventricle. This is the logic behind afterload reduction in HF and behind Impella in cardiogenic shock: shrink the loop, spend less oxygen.", "kind": "literal", "quote": "'" }, { "start": 108848, "end": 108890, "text": "PVA ≈ myocardial oxygen consumption", "kind": "literal", "quote": "'" }, { "start": 108891, "end": 108931, "text": "Efficiency = SW/PVA, best when coupled", "kind": "literal", "quote": "'" }, { "start": 108950, "end": 108959, "text": "Failure", "kind": "literal", "quote": "'" }, { "start": 108966, "end": 108982, "text": "HFrEF vs HFpEF", "kind": "literal", "quote": "'" }, { "start": 108987, "end": 109035, "text": "Two heart failures, two different lines break.", "kind": "literal", "quote": "'" }, { "start": 109053, "end": 109079, "text": "HFrEF: the ceiling falls", "kind": "literal", "quote": "'" }, { "start": 109086, "end": 109326, "text": "In heart failure with reduced EF, contractility collapses: the ESPVR flattens. The ventricle can’t empty, so it dilates to preserve output (Frank–Starling). The loop shifts right, EF falls, and Ea/Ees uncouples.", "kind": "literal", "quote": "'" }, { "start": 109347, "end": 109359, "text": "Load HFrEF", "kind": "literal", "quote": "'" }, { "start": 109411, "end": 109435, "text": "HFpEF: the floor rises", "kind": "literal", "quote": "'" }, { "start": 109442, "end": 109686, "text": "In HF with preserved EF the systolic line is fine. The problem is the EDPVR. A stiff ventricle climbs the diastolic curve steeply: normal EF, but high filling pressure at a small volume. That pressure backs up into the lungs.", "kind": "literal", "quote": "'" }, { "start": 109707, "end": 109719, "text": "Load HFpEF", "kind": "literal", "quote": "'" }, { "start": 109766, "end": 109797, "text": "Same syndrome, opposite loops", "kind": "literal", "quote": "'" }, { "start": 109804, "end": 109986, "text": "Side by side, HFrEF is a wide, short, right-shifted loop; HFpEF is a narrow, tall loop crammed against a steep diastolic curve. Both raise filling pressure, by different mechanics.", "kind": "literal", "quote": "'" }, { "start": 110001, "end": 110097, "text": "Which line would you target with a positive inotrope, and which is essentially inotrope-proof?", "kind": "literal", "quote": "'" }, { "start": 110100, "end": 110294, "text": "Inotropes steepen the ESPVR, which helps in HFrEF. HFpEF’s problem is the passive EDPVR, which inotropes don’t fix; that’s why HFpEF has been so hard to treat pharmacologically.", "kind": "literal", "quote": "'" }, { "start": 110308, "end": 110337, "text": "HFrEF = flat ESPVR, dilated", "kind": "literal", "quote": "'" }, { "start": 110338, "end": 110373, "text": "HFpEF = steep EDPVR, preserved EF", "kind": "literal", "quote": "'" }, { "start": 110392, "end": 110400, "text": "Valves", "kind": "literal", "quote": "'" }, { "start": 110407, "end": 110430, "text": "Reading valve disease", "kind": "literal", "quote": "'" }, { "start": 110435, "end": 110508, "text": "One question unlocks every valve lesion: which phase or line is broken?", "kind": "literal", "quote": "'" }, { "start": 110526, "end": 110551, "text": "A framework, not a list", "kind": "literal", "quote": "'" }, { "start": 110558, "end": 110752, "text": "Stenosis = obstruction to forward flow. Regurgitation = backward leak that erases an isovolumetric phase. Where the lesion sits (aortic vs mitral) decides which corner moves.", "kind": "literal", "quote": "'" }, { "start": 110762, "end": 110779, "text": "Aortic stenosis", "kind": "literal", "quote": "'" }, { "start": 110786, "end": 111019, "text": "The ventricle must generate huge pressure to force blood through a narrow valve, so peak LV pressure rises far above aortic pressure. That gap is the gradient. Turn on the peak-LVP line to see LV and aorta diverge.", "kind": "literal", "quote": "'" }, { "start": 111040, "end": 111057, "text": "Aortic stenosis", "kind": "literal", "quote": "'" }, { "start": 111107, "end": 111139, "text": "Aortic vs mitral regurgitation", "kind": "literal", "quote": "'" }, { "start": 111146, "end": 111422, "text": "AR fills the ventricle in diastole (aortic leak): no true isovolumetric relaxation, wide loop, low diastolic BP. MR empties into the atrium in systole: no true isovolumetric contraction, the left wall of the loop vanishes.", "kind": "literal", "quote": "'" }, { "start": 111443, "end": 111465, "text": "Mitral regurgitation", "kind": "literal", "quote": "'" }, { "start": 111511, "end": 111529, "text": "Acute vs chronic", "kind": "literal", "quote": "'" }, { "start": 111536, "end": 111852, "text": "Chronicity changes the EDPVR. Chronic volume overload remodels eccentrically into a compliant, dilated chamber that tolerates the volume. An acute lesion hits a normal-sized, stiff ventricle: filling pressure rises sharply. Compare chronic vs acute MR to see the same leak on two different floors.", "kind": "literal", "quote": "'" }, { "start": 111873, "end": 111883, "text": "Acute MR", "kind": "literal", "quote": "'" }, { "start": 111937, "end": 111952, "text": "Test yourself", "kind": "literal", "quote": "'" }, { "start": 111966, "end": 112068, "text": "A loop has lost its left vertical wall and sits shifted left with a low peak pressure. Which lesion?", "kind": "literal", "quote": "'" }, { "start": 112071, "end": 112212, "text": "Mitral regurgitation. The systolic leak into the atrium erases isovolumetric contraction and unloads the ventricle, lowering peak pressure.", "kind": "literal", "quote": "'" }, { "start": 112226, "end": 112261, "text": "AS → LV–aortic gradient", "kind": "literal", "quote": "'" }, { "start": 112262, "end": 112292, "text": "AR erases IVR; MR erases IVC", "kind": "literal", "quote": "'" }, { "start": 112293, "end": 112326, "text": "Acute lesions hit a stiff floor", "kind": "literal", "quote": "'" }, { "start": 112345, "end": 112363, "text": "Support & repair", "kind": "literal", "quote": "'" }, { "start": 112370, "end": 112397, "text": "Devices and interventions", "kind": "literal", "quote": "'" }, { "start": 112402, "end": 112470, "text": "How mechanical support and valve/lead procedures reshape the loop.", "kind": "literal", "quote": "'" }, { "start": 112488, "end": 112505, "text": "IABP vs Impella", "kind": "literal", "quote": "'" }, { "start": 112512, "end": 112812, "text": "The balloon pump nudges: it lowers afterload and improves coronary flow, modestly shrinking the loop. Impella actively drains the ventricle. The loop shrinks and triangularises, PVA (oxygen demand) drops sharply. Layer each device onto cardiogenic shock and watch.", "kind": "literal", "quote": "'" }, { "start": 112833, "end": 112851, "text": "Impella on shock", "kind": "literal", "quote": "'" }, { "start": 112912, "end": 112933, "text": "The VA-ECMO paradox", "kind": "literal", "quote": "'" }, { "start": 112940, "end": 113228, "text": "VA-ECMO rescues the circulation but punishes the ventricle: retrograde aortic flow raises afterload, so the loop is pushed up and right and PVA rises. Adding an Impella to vent the LV (ECPELLA) pulls it back down. This is the rationale for LV venting.", "kind": "literal", "quote": "'" }, { "start": 113249, "end": 113272, "text": "VA-ECMO, then compare", "kind": "literal", "quote": "'" }, { "start": 113348, "end": 113364, "text": "TAVR, MVR, CRT", "kind": "literal", "quote": "'" }, { "start": 113371, "end": 113694, "text": "Interventions are best read as before → after pairs. TAVR abolishes the aortic gradient (loop widens, peak LVP drops to aortic). MVR restores isovolumetric contraction and unmasks true EF. CRT re-coordinates a dyssynchronous ventricle so the loop lifts and narrows.", "kind": "literal", "quote": "'" }, { "start": 113715, "end": 113742, "text": "Pre-TAVR (then pick Post)", "kind": "literal", "quote": "'" }, { "start": 113794, "end": 113829, "text": "Impella unloads; ECMO can distend", "kind": "literal", "quote": "'" }, { "start": 113830, "end": 113861, "text": "LV venting lowers PVA on ECMO", "kind": "literal", "quote": "'" }, { "start": 113862, "end": 113903, "text": "Interventions read as before→after", "kind": "literal", "quote": "'" }, { "start": 114147, "end": 114172, "text": "", "kind": "head", "quote": "`" }, { "start": 114495, "end": 114546, "text": "
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Evidence · ", "kind": "head", "quote": "`" }, { "start": 118256, "end": 118471, "text": "", "kind": "literal", "quote": "`" }, { "start": 118756, "end": 125553, "text": "\n

Reference & method

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How the simulator computes each loop, how it was calibrated, and where to read more.
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Free. Open. For everyone.
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CardioMechanics is FOAMed, or Free Open-Access Medical education. No login, no paywall, no tracking. Fork it, host it, teach with it, remix it. Physiology should be a commons.

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The model

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Each loop is integrated numerically (time step 2 ms) over several beats until it stabilises. The ventricle is a time-varying elastance chamber; the arterial system is a two-element Windkessel; the valves are pressure-driven conductances.

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Time-varying elastance. Instantaneous pressure follows an activation function that rises and falls each beat:

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E(t) = (Ees − 0.1)·sin³(πt/Ts) + 0.1 for 0 ≤ t ≤ Ts\nP_lv(t) = max[ E(t)·(V − V₀) , P_edpvr(V) ]
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Passive filling (EDPVR) is an exponential; its amplitude (stiffness) and curvature are the two diastolic sliders:

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P_edpvr(V) = 2·s + 1.2·s·exp(0.016·β·V) s = stiffness, β = curvature
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Arterial load (Windkessel). Aortic pressure is driven by ejected flow against a compliance and a runoff resistance toward mean arterial pressure:

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dP_ao/dt = [ Q_out + Q_device − (P_ao − MAP)/R ] / C
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Valves are linear conductances that open on a favourable gradient: mitral inflow (kFill), aortic outflow (kAv). Lesions scale these: aortic stenosis reduces kAv; aortic/mitral regurgitation add a reverse conductance; mitral stenosis reduces kFill.

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Calibration & validation

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Two deliberate choices keep the model honest for teaching. First, the aortic-valve conductance is set so that in normal physiology peak LV pressure equals aortic systolic pressure (no artefactual gradient), while severe aortic stenosis still produces a genuine ~50 mmHg trans-valvular gradient. Second, arterial compliance is fixed rather than re-tuned for each condition, so a failing heart shows a genuinely low stroke volume instead of having it normalised away.

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Every one of the 24 conditions was checked against expected ranges for stroke volume, ejection fraction, chamber volumes, aortic pressure, filling pressure and ventriculo-arterial coupling. Chronic volume-overload lesions are modelled with compliant (eccentric) chambers; acute lesions and restrictive or hypertrophic hearts are modelled with stiff chambers. This matches how the ventricle remodels.

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Support-device sanity checks: IABP and Impella both reduce pressure–volume area (oxygen demand); Impella raises total output while shrinking the loop; VA-ECMO reproduces the LV-distension paradox (rising PVA); ECPELLA vents that distension.
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What the model does not do

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This is a single left-ventricle model. It has no right heart, no explicit atria, no lungs, no baroreflex, and a fixed heart rate. That means it cannot represent tamponade or constriction (pericardial coupling), right-heart failure, pulmonary hypertension, dynamic LVOT obstruction, or true rate effects. Cardiac output at high heart rates is therefore conservative. Conditions that depend on those mechanisms are described in the library but not simulated. Numbers are physiologically plausible, not patient-specific.

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Educational use only. Nothing here is a clinical tool or a substitute for measured haemodynamics.

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Foundations & further reading

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  1. Suga H, Sagawa K. Instantaneous pressure–volume relationships and their ratio in the excised, supported canine left ventricle. Circ Res 1974.
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  2. Suga H. Total mechanical energy of a ventricle model and cardiac oxygen consumption. Am J Physiol 1979. PVA ≈ MVO₂.
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  3. Sunagawa K, Maughan WL, Burkhoff D, Sagawa K. Left ventricular interaction with arterial load studied in isolated canine ventricle. Am J Physiol 1983. Ea and coupling.
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  4. Sagawa K, Maughan L, Suga H, Sunagawa K. Cardiac Contraction and the Pressure–Volume Relationship. Oxford, 1988.
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  5. Burkhoff D, Mirsky I, Suga H. Assessment of systolic and diastolic ventricular properties via pressure–volume analysis. Am J Physiol Heart Circ Physiol 2005.
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  6. Kelly RP, et al. Effective arterial elastance as an index of arterial vascular load in humans. Circulation 1992.
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  7. Burkhoff D, et al. Hemodynamics of mechanical circulatory support. J Am Coll Cardiol 2015. IABP, Impella, VA-ECMO on the PV loop.
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Credits & licence

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CardioMechanics 2.0 is a rebuild of the original CardioMechanics simulator. The elastance + Windkessel formulation follows the widely taught digital model popularised by Nick Mark, MD, grounded in the classical work of Suga, Sagawa, Sunagawa, Burkhoff and Kelly cited above. Zero external dependencies: one HTML file, works offline.

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Released for free reuse in the spirit of FOAMed. Attribution appreciated. Not for clinical use.

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", "kind": "literal", "quote": "`" } ]