Novel, single-beat approach for determining both end-systolic pressure-dimension relationship and preload recruitable stroke work

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 (Mw) and for a dimension-axis intercept (Dw). The ESPDR represented by the formula Pes(Des) = A ln (Des=D0)=(Des=D0)3g, was estimated from a steady-state, single-beat late-systolic pressure- dimension relationship. The single-beat Mw was determined as an end-systolic pressure when the endsystolic dimension was equal to Dw. 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 Mw calculated using the wall thickness was strongly correlated with the actual Mw (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 Mw estimated without information on wall thickness. Conclusions: Mw can be interpreted as an endsystolic pressure when the end-systolic dimension is equal to Dw. By using the non-linear ESPDR, accurate single-beat estimation of the ESPDR and Mw is possible even without information on wall thickness. These results should enhance the applicability of pressure-volume framework to clinical medicine.