Comparative efficacy of three indexes of left ventricular performance derived from pressure-volume loops in heart failure induced by tachypacing

Objectives. The purpose of this study was to serially evaluate the response and variability of the end-systolic pressure-volume relation, the left ventricular end-diastolic volume-peak positive first derivative of left ventricular pressure (dP/dt) relation and the left ventricular end-diastolic volume-stroke work relation in the development of progressive left ventricular dysfunction. Background. Evaluation of systolic performance of the failing left ventricle may be enhanced by using relatively load-insensitive measures of left ventricular performance. The end-systolic pressure-volume, left ventricular end-diastolic volume-peak positive dP/dt and left ventricular end-diastolic volume-stroke work relations adequately define left ventricular performance under multiple leading conditions, but efficacy has not been fully assessed in the failing heart, particularly in the intact circulation. Methods. Fourteen dogs underwent instrumentation and rapid pacing to heart failure. Variably loaded pressure-volume beats were produced by inferior vena cava occlusion. The dogs were evaluated at baseline and at three progressively more severe levels of left ventricular dysfunction. Results. There was a progressive increase in left ventricular volumes at end-diastole ([mean value ± SE]60 ± 28 to 73 ± 29 ml, p < 0.001) and end-systole (39 ± 19 to 61 ± 27 ml, p < 0.001) during the 3 weeks of rapid pacing and a progressive decline in peak positive dP/dt (1,631 ± 410 to 993 ± 222 nun Hg/s, p < 0.001) and ejection fraction (37 ± 8% to 16 ± 11%, p < 0.001). There was a corresponding decline in the slope of each of the three relations: for end-systolic pressure-volume, 6.3 ± 2.2 to 2.8 ± 0.7 (p < 0.05); for left ventricular end-diastolic volume-stroke work, 61.9 ± 9,1 to 26.5 ± 2.4 (p < 0.05); and for left ventricular end-diastolic volume-peak positive dP/dt, 47.1 ± 13.6 to 20.31 ± 6.8 (p < 0.05). There was also a corresponding increase in position volumes: for end-systolic pressure-volume, 33.6 ± 3.9 to 61.2 ± 6.6 ml (p < 0.05); for left ventricular end-diastolic volume-stroke work, 46.2 ± 3.6 to 89.3 ± 7.6 ml (p < 0.05); and for left ventricular end-diastolic volume-peak positive dP/dt, 29.1 ± 19.1 to 68.6 ± 25.9 ml (p < 0.05). The relative degree of change in each of the three relations was similar as more severe heart failure developed. The coefficients of variation for position were significantly less than the variation for slopes. The response of volume intercepts was heter