impact of preemptive phosphodiesterase III inhibition on left ventricular diastolic performance after valve replacement for aortic stenosis

ABSTRACT

Left ventricular diastolic dysfunction [LVDD] in aortic stenosis is an important independent risk factor for early and late postoperative mortality. We hypothesized that enoximone or milrinone, administered after releasing the aortic cross-clamp improved the diastolic function of the left ventricle as assessed by transesophageal echocardiography [TEE] in patients with aortic stenosis undergoing aortic valve replacement. Forty-five adult patients with valvular aortic stenosis and preserved systolic function scheduled for primary aortic valve replacement were randomly assigned to one of three equal groups; in group M [milrinone group, n = 15] patients received milrinone with a loading dose of 50 microg/kg followed by an infusion of 0.5 microg/kg/min for 6 hours. In group E [enoximone group, n = 15] patients were given enoximone after release of aortic cross-clamp, with an initial bolus of 0.5 mg/kg followed by a continuous infusion of 2.5 microg/kg/min for 6 hours, and in group C [control group, n = 15] patients received saline bolus and infusion at the same time and interval as the first two groups. Hemodynamic parameters and transesophageal echocardiographic assessment of left ventricular end-diastolic area [EDA], transmitral inflow velocity, and tissue doppler imaging [TDI] of the mitral annulus parameters were assessed pre-bypass [Tl], post-bypass [12] after administration of the test drug and separation from CPB, and at the end of the operation after chest closure [T3]. Cardiac index showed a statistically significant increase [p < 0.05], while the systemic vascular resistance showed statistically significant decrease [p < 0.05] in T2 and T3 compared to Tl in the three groups. Cardiac index was significantly higher [p < 0.05] and the systemic vascular resistance was significantly lower [p < 0.05] in T2 and T3 in both the milrinone and enoximone groups compared to the control group at the same intervals. Left ventricular end-diastolic area showed a decrease in all groups which was statistically significant [p < 0.05] comparing T2 and T3 to Tl but without intergroup difference. Peak E-wave velocity, peak A-wave velocity and E/A ratio of the transmitral flow were comparable in the three groups. E-wave deceleration time was significantly decreased [p < 0.05] in T2 and T3 in the three groups. Tissue Doppler analysis of the peak early mitral annular velocity revealed no significant difference between the three groups. The administration of milrinone or enoximone after release of aortic cross-clamp in valve replacement for aortic stenosis did not improve ventricular diastolic function and failed to show increase in the indices of compliance and relaxation compared to the control