Diastolic ventricular properties in patients during coronary revascularization. Intermittent ischemic arrest versus cardioplegia.

ABSTRACT

Left ventricular diastolic properties were examined in 24 patients undergoing coronary revascularization with either 32 degrees C intermittent ischemic arrest (IA) or 4 degrees C potassium cardioplegia (CP) for myocardial protection. The ages, numbers of grafts, and preoperative cardiac function were similar for the two groups of patients. For compliance data, hearts were filled passively during bypass perfusion to diastolic pressures between 0 and 20 mm Hg by clamping the left ventricular vent. Simultaneously, minor axis dimensions were measured with 8 mm epicardial ultrasonic crystals. End-diastolic lengths (EDL), normalized to a Lagrangian strain definition (epsilon), were compared at each pressure (P) by the nonlinear regression equation, P = alpha(e beta epsilon-1). Both elastic constants, alpha and beta, as well as linear regression slopes (k) of pressure-strain data were compared as indices of ventricular stiffness. Prior to determinations, the EDL at 0 mm Hg transmural pressure was defined as l0. At each filling pressure, a leftward shift in the compliance curve developed following IA but not CP. Moreover, shifts in alpha, beta, and k constants occurred with IA alone, l0 did not change in either group. Therefore, stiffening did not occur when CP was used for protection, despite ischemic durations twice those of IA (31 versus 15 minutes). These data confirm CP to be a superior method of cardiac protection during coronary bypass grafting and show diastolic ventricular properties to be a sensitive indicator of subclinical ischemic injury.