Determinants of left ventricular preload-adjusted maximal power

1 Hydraulics Laboratory, Institute Biomedical Technology, Ghent University, 9000 Gent; 2 Hemodynamic Research Center, University of Liege, 4000 Liege; and 3 Centre for Experimental Surgery and Anaesthesiology, Katholieke Universiteit Leuven, 3000 Leuven, Belgium Maximal left ventricular (LV) hydraulic power output (PWR max ), corrected for preload as PWR max /(V ed ) (where V ed is the end-diastolic volume and is a constant coefficient), is an index of LV contractility. Whereas preload-adjusted maximal power (PAMP) is usually calculated with = 2, there is uncertainty about the optimal value of ( = 1 for the normal LV and 2 for the dilated LV). The aim of this work is to study the determining factors of . The data set consisted of 245 recordings (steady state and vena cava occlusion) in 10 animals in an ischemic heart pig model. The occlusion data yielded the slope ( E es ; 2.01 ± 0.77 mmHg/ml, range 0.71-4.16 mmHg/ml) and intercept (V 0 ; 11.9 ± 22.6 ml; range 76 to 39 ml) of the end-systolic pressure-volume relation, and the optimal -factor (assessed by fitting an exponential curve through the V ed -PWR max relation) was 1.94 ± 0.88 (range 0.29-4.73). The relation of with V ed was weak [ = 0.60 + 0.02(V ed ); r 2 = 0.20]. In contrast, we found an excellent exponential relation between V 0 and [ = 2.16 r 2 = 0.70]. PAMP, calculated from the steady-state data, was 0.64 ± 0.40 mW/ml 2 (range 0.14-2.83 mW/ml 2 ) with a poor correlation with E es ( r = 0.30, P