Objective The end-systolic pressure–dimension relationship (ESPDR) and the preload recruitable stroke work (PRSW) relationship are load-insensitive measures of contractility, but their clinical application has been limited by the need to record multiple beats over a wide volume range. In this study, we therefore sought to validate a new method to concomitantly determine the ESPDR and the PRSW relationship from a single beat.

Methods Pressure–dimension loops were recorded in 14 conscious dogs under various haemodynamic and pathological conditions. Multiple-beat PRSW relationship was determined for its slope (M_w) and for a dimension-axis intercept (D_w). The ESPDR represented by the formula , was estimated from a steady-state, single-beat late-systolic pressure–dimension relationship. The single-beat M_w was determined as an end-systolic pressure when the end-systolic dimension was equal to D_w.

Results A strong correlation was observed between multiple-beat and single-beat ESPDRs (zero-stress dimension; r=0.98, p<0.0001). The single-beat estimation of M_w calculated using the wall thickness was strongly correlated with the actual M_w (r=0.93, p<0.0001) and was sensitive enough to detect the change in contractility by dobutamine infusion (p<0.001) and by tachycardia-induced heart failure (p<0.001). Similar results were obtained for M_w estimated without information on wall thickness.

Conclusions M_w can be interpreted as an end-systolic pressure when the end-systolic dimension is equal to D_w. By using the non-linear ESPDR, accurate single-beat estimation of the ESPDR and M_w is possible even without information on wall thickness. These results should enhance the applicability of pressure–volume framework to clinical medicine.