[Ultrastructure of the myocardium in the calcium channel blocker withdrawal syndrome].

Changes in the ultrastructure of rat myocardial cells were investigated after withdrawal of therapy with the calcium entry blockers diltiazem, nifedipine, and verapamil. Two hours after the last administration the ultrastructure was without significant changes in comparison to the control group. However the incidence of contracture bands, dehiscence of intercalated discs and lesions of mitochondria observed 30 hours after therapy withdrawal demonstrated serious damage of myocardial tissue. The recorded changes, practically identical with changes associated with the calcium paradox, were the consequence of withdrawal of calcium entry blocker therapy. The reported morphological changes reflected biochemical and functional changes characteristic of the calcium entry blocker withdrawal syndrome.