Ventricular systolic assessment in patients with dilated cardiomyopathy by preload-adjusted maximal power: Validation and noninvasive application

Abstract

Background: Noninvasive cardiac-specific analysis of contractile function in patients with dilated heart failure remains problematic. This study tests whether maximal power divided by the square of end-diastolic volume (PWR(mx)/EDV2, or preload-adjusted PWR(mx)) can provide such assessment. Methods and Results: To validate the load insensitivity of the PWR(mx) index and determine its response to contractile change, 24 subjects with chronic dilated cardiomyopathy underwent invasive pressure-volume catheterization study using the conductance catheter technique. Preload was transiently reduced by 30% using balloon occlusion of the inferior vena cava, and afterload impedance was lowered by 50%, induced by a bolus injection of nitroglycerin. Contractile state was varied by intravenous dobutamine, verapamil, or esmolol. PWR(mx) was calculated from the simultaneous product of ventricular pressure and rate of volume change (dV/dt), the latter derived from the volume catheter signal. PWR(mx) varied directly with preload but was minimally influenced by afterload. However, PWR(mx)/EDV2 was not significantly altered by either loading change. PWR(mx)/EDV2 did vary with contractility, correlating closely with changes in the end-systolic pressure- volume relation (r=.91, P