COMPARISON OF PRELOAD RECRUITABLE STROKE WORK, END-SYSTOLIC PRESSURE-VOLUME AND DP/DTMAX-END-DIASTOLIC VOLUME RELATIONS AS INDEXES OF LEFT-VENTRICULAR CONTRACTILE PERFORMANCE IN PATIENTS UNDERGOING ROUTINE CARDIAC-CATHETERIZATION

The end-systolic pressure-volume relation, the relation between stroke work and end-diastolic volume, termed the preload recruitable stroke work relation, and the relation between the peak of the first derivative of left ventricular pressure (dP/dt(max)) and end-diastolic volume have been employed as linear indexes of left ventricular contractile performance in laboratory animals. The purpose of this study was to examine the relative utility of these indexes during routine cardiac catheterization in seven human subjects (mean age 48 +/- 18 [SD] years) with a normal left ventriculogram and coronary angiogram. Left ventricular pressure was recorded continuously with a micromanometer catheter, and left ventricular volume was derived from digital subtraction contrast ventriculograms obtained at 30-ms intervals. Transient occlusion of the inferior vena cava with a balloon-tipped catheter was employed to obtain beat to beat reductions in left ventricular pressure and volume over 8.7 +/- 1.7 cardiac cycles. Stroke work declined by 49 +/- 13% during vena caval occlusion, but end-systolic pressure fell by only 26 +/- 11 %, and changes in dP/dt(max) were small and inconsistent (12 +/- 22%). Consequently, the range of data available for determination of the preload recruitable stroke work relation greatly exceeded that for the end-systolic pressure-volume relation and the dP/dt(max)-end-diastolic volume relation, and much less linear extrapolation from the measured data was required to determine the volume-axis intercept. Preload recruitable stroke work relations were highly linear (r = 0.95 +/- 0.07), and much more so than end-systolic pressure-volume relations (r = 0.79 +/- 0.23). The correlation between dP/dt(max) and end-diastolic volume was very poor over the limited range examined (r = 0.30 +/- 0.48). The slopes and volume-axis intercepts of the end-systolic pressure-volume relations in normal hearts were more variable; SD/mean values = 78% and 183%, respectively, compared with 40% and 46% for the preload recruitable stroke work relations. The volume-axis intercepts of the end-systolic pressure-volume relations were spuriously negative in six of seven subjects, but those of the preload recruitable stroke work relations were positive in all cases. Thus, with the limited range of pressure-volume data obtainable during cardiac catheterization in human subjects, the preload recruitable stroke work relation appears to have greater clinical utility than the end-systolic pressure-volume relation or the dP/dt(max)-end-diastolic volume relation as a linear index of left ventricular contractile performance.