In current pressure-volume (PV) literature hemodynamic stress using preload reduction is employed to acquire indices of cardiac contractility. The isochrone points in the PV loop where the Maximal PV ratio occurs is called the end systolic ventricular elastance Emax. The Emax (point in given loop) was originally modeled by Suga and Sagawa as being linear (1,2,3) as at this point the ratio of P vs. V can be also referred as end systolic chamber elastance (to extrapolate it for LV and RV chamber). Emax approximates the slope Ees of the end-systolic pressure-volume relationship (ESPVR)..

ESPVR is frequently used to measure cardiac contractility in research and clinical practice purposes.

The maximal PV ratio point(s) Emax however differs from the end systolic point(s) on the PVL plane for every beat during the preload reduction maneuver.

What are in your opinion (hemodynamic conditions e.g., high afterload, low amount of preload or other) where the ES points would better characterize the ESPVR relationship as compared to using Emax points?

I have attached a PDF to summarize the question in more detail. Data are collected from swine model using both Emax and ES points, while modeling is using linear and quadratic fitting without fixed V0 (3) during hemodynamic stress during IVC occlusion.

References:

1. Suga H, Sagawa K, Shoukas AA. Load independence of the instantaneous pressure-volume ratio of the canine left ventricle and effects of epinephrine and heart rate on the ratio. Circ Res. 1973 Mar;32(3):314-22. doi: 10.1161/01.res.32.3.314. PMID: 4691336.

2. Suga H, Sagawa K. Instantaneous pressure-volume relationships and their ratio in the excised, supported canine left ventricle. Circ Res. 1974 Jul;35(1):117-26. doi: 10.1161/01.res.35.1.117. PMID: 4841253.

3. Claessens TE, Georgakopoulos D, Afanasyeva M, Vermeersch SJ, Millar HD, Stergiopulos N, Westerhof N, Verdonck PR, Segers P. Nonlinear isochrones in murine left ventricular pressure-volume loops: how well does the time-varying elastance concept hold? Am J Physiol Heart Circ Physiol. 2006 Apr;290(4):H1474-83.