Myocardial changes in malignant hyperthermia.

Although consideral information is available concerning the structural and biochemical changes in the skeletal muscles of patients with malignant hyperthermia, little is known of the cardiac changes in this disease. However, ventricular fibrillation and cardiac arrest are frequent in these patients. In 3 patients with malignant hyperthermia, contraction bands and foci of myofiberlysis were found in the heart at necropsy. Ultrastructurally, areas of myofiber overstretching adjacent to contraction bands and foci of extensive myofiberlysis were associated with disruptions of the sarcolemma. Similar ultrastructural findings have been reported in the skeletal muscles of these patients and are thought responsible for the hyperkalemia which is a constant feature of malignant hyperthermia. Our findings suggest that the ventricular arrhythmias, frequent in this disease, are the result of direct damage to cardiac muscle rather then secondary to elevated plasma levels of potassium.