The elastance model behind the loop
This simulator draws a left ventricular pressure-volume loop from the time-varying elastance model of Suga and Sagawa. Three reference lines frame it: the ESPVR, a straight line of slope Ees through the unstressed volume V0; the EDPVR, an exponential curve whose steepness is set by the chamber stiffness constant B; and the arterial elastance line Ea, drawn from end-diastolic volume on the volume axis to the end-systolic point. Six sliders set Ees, Ea, EDV, B, heart rate and V0; end-systole falls where the ESPVR and Ea line intersect.
Hemodynamic readouts and ventriculo-arterial coupling
Each change updates stroke volume, ejection fraction, cardiac output, end-systolic and end-diastolic pressure, stroke work as the area enclosed by the loop, and the Ea/Ees coupling ratio. Readouts are flagged against the tool's bands: ejection fraction normal from 55 to 70 percent, cardiac output from 4.0 to 8.0 L/min, and coupling normal from 0.5 to 1.3 and borderline up to 1.5. Moving one slider at a time separates preload, afterload and contractility.
Drugs and interventions
Fifteen agents are grouped as inotropes (dobutamine, milrinone, isoproterenol, low- and high-dose dopamine), vasopressors (phenylephrine, norepinephrine), vasodilators (nitroprusside, nitroglycerin, phentolamine, an ACE inhibitor and a dihydropyridine calcium channel blocker), metoprolol as a negative inotrope, and volume as fluids or diuretics. Each acts by shifting Ees, Ea, EDV or B, so phenylephrine moves the Ea line alone while nitroglycerin, mainly a venodilator, pulls preload down. Agents stack additively.
Disease states
Eighteen presets set all six parameters at once; drugs then stack on top. Heart failure covers HFrEF, HFpEF and dilated cardiomyopathy; shock, cardiogenic shock at SCAI stage C/D, warm septic shock and hypovolemic shock; remodeling, concentric and eccentric LVH; pericardial disease, constrictive pericarditis and tamponade. Valve disease includes aortic and mitral stenosis and regurgitation plus mixed lesions AS+AR, AS+MR, MS+MR and MS+AS. Regurgitant loops lose their vertical limbs: mitral regurgitation abolishes isovolumic contraction, aortic regurgitation abolishes isovolumic relaxation, and each tilts the opposite limb slightly.
Mechanical circulatory support
Five configurations layer onto any disease and drug combination. The intra-aortic balloon pump unloads modestly by counterpulsation, adding about 0.5 L/min. Impella CP and Impella 5.0 are transvalvular axial pumps that unload the ventricle directly, lower LVEDP and progressively triangularize the loop; with the 5.0 the aortic valve may not open. VA-ECMO raises afterload and distends the left ventricle despite full systemic support, which is why LV venting is considered. ECPELLA adds an Impella to ECMO, unloading while perfusing.
Comparing loops and worked cases
A ghost loop is stored automatically before the first drug, disease or device is chosen, so each new loop is drawn against its own baseline; snapshots can also be taken manually. Toggles hide the ESPVR, EDPVR and Ea lines, the phase labels and the animated tracing. The phase-label toggle also carries markers for mitral and aortic valve opening and closing, and renames any limb no longer isovolumic. Three worked examples load full scenarios, one of them cardiogenic shock supported with an Impella CP and dobutamine.