Hemodynamic effects of oral amiodarone on left ventricular function before and after global ischemia

We evaluated the hemodynamic effects of amiodarone on left ventricular (LV) function after global ischemia. Amiodarone was administered orally at 15 mg/kg/day for an average of 28 days to a group of 10 dogs. The concentration of amiodarone in serum and LV myocardium was 0.40 +/- 0.24 micrograms/ml and 44 +/- 27.0 micrograms/g, respectively. This experimental group and a control group of 10 dogs each underwent 120 min of aortic cross-clamping with cold crystalloid cardioplegia resulting in an average myocardial temperature of 15 degrees C. LV function measurements by pulse-transit sonomicrometry and Millar solid-state micromanometers were processed by a minicomputer. Compared to the nontreated control group, oral amiodarone for 28 days produced depression of LV contractility which was reflected by lower slope of the end-systolic pressure-volume relation (Evmax), percentage shortening of segment length, left ventricular pressure-segment length loop area, and slope of the end-systolic pressure-segment length relation (Esmax). After ischemia, percentage recovery of LV global function (Evmax and mean velocity of circumferential fiber shortening) and regional function (Esmax) was significantly better in the amiodarone group than in the control group. We conclude that oral amiodarone for 28 days results in a depression of LV contractility but the combination of amiodarone and ischemia does not act synergistically to further depress postischemic LV function.