The effect of verapamil cardioplegia on myocardial ultrastructure

The calcium channel blocker, verapamil, was evaluated as an adjunct to cold cardioplegia in 16 randomized patients with unstable angina pectoris who received saphenous vein bypass grafts. Myocardial biopsies taken before cardioplegia showed various degrees of ischemic change as assessed by ultrastructural parameters (mitochondrial swelling, matrix clearance, and sarcotubular dilatation). After reperfusion, the majority of the patients had progressive changes of ischemia, with marked mitochondrial and sarcotubular swelling, depletion of glycogen, chromatin clumping, and myofibrillar disruption; amorphous mitochondrial densities were occasionally seen. The ultrastructural changes after cardioplegia were dependent primarily on the extent of preexisting ischemic damage and did not correlate with the use of verapamil. Verapamil did not protect the ischemic myocardium during cold cardioplegia as assessed ultrastructurally.