Overview
PV pressure is sampled from the same ventricular pressure function used by the catheter trace. Volume is synthesized from forward flow, regurgitation, shunts, device drainage and a phenotype-specific filling/cavity model. It is not conductance-catheter data or measured echo volume.
LV and RV loops use separate pressure functions and volume accounting. The low-pressure RV ejection contour is not a scaled LV rectangle. Loop width is chamber volume excursion; with regurgitation, shunts or a pump it is not automatically net systemic stroke volume.
Cavity and preload
Representative cavity sizes distinguish normal, dilated/ischemic, stiff, constrained, depleted and chronically volume-loaded phenotypes. A logarithmic pressure-loading term changes volume relative to the phenotype’s reference EDP: cavity + compliance-like coefficient × ln((transmural filling + 3)/(reference EDP + 3)). The coefficient is a teaching parameter, not measured compliance.
Mild/moderate isolated valve disease has no assumed chronic ventricular remodeling. Severe chronic MR/AR or TR/PR can add a volume-loaded cavity. Acute MR/AR does not receive chronic dilation solely from its acute label. Actual flow conservation can still increase EDV when a large total stroke volume needs room.
Volume trajectory and leakage
For ordinary organized flow, forward SV comes from nominal flow, rate and beat strength. Regurgitant fractions add recirculating SV; EDV/ESV bounds prevent negative residual volume. Smooth segments connect filling, contraction, ejection and relaxation around pressure-derived valve events.
MR permits volume loss outside conventional ejection; AR permits backflow throughout relaxation, so truly isovolumic phases disappear. Late-systolic MVP initially preserves closure. Impella drainage and VSD flow are integrated through the cycle; blood does not wait for the normal aortic ejection phase to leave the LV.
Support and shunt balance
Impella volume drainage continues during contraction and relaxation. ECMO return is outside the LV loop, so supported total systemic output is not assigned as LV stroke volume. RV delivery includes blood later drained by Impella but excludes ECMO bypass.
Septal flow is balanced between chambers and ductal flow is assigned to its correct downstream connection. During VF or a ventricular pause, a normal closed stroke-work loop is not drawn. Out-of-range large volumes are flagged as limited extrapolations rather than interpreted as reliable measurements.
Respiratory stabilization and display smoothing
Respiratory loading is held consistently across a whole modeled cardiac cycle rather than warping different parts of one loop with different breaths. The live cycle study uses end expiration; paused comparison can select end inspiration or respiratory mean. Tamponade endpoint comparisons retain opposite LV/RV filling responses unless buffered by a large ASD.
The axes reserve respiratory headroom and do not shrink on every expiration. A brief display-only interpolation can smooth regular-beat outline changes; irregular/ectopic beats and alternating assistance are not averaged away. Interpolated geometry never feeds measurements, Wiggers or inspection.
What the loop cannot establish
The model does not fit ESPVR, EDPVR, pressure–volume area, end-systolic elastance, coronary energetics or true contractility from data. An attractive loop is not proof of patient-specific ventricular mechanics. Its value is explaining the shared pressure/flow assumptions visibly.
References & further reading
