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A reproducible canine model of stone heart (irreversible left ventricular rigor) is described. During the studies, perfusion of the coronary circulation with various concentrations and compositions of magnesium sulfate solutions did not significantly influence the development of stone heart. Approximately 90 minutes of normothermic, ischemic arrest appeared to be the turning point for the transition of left ventricles from a flaccid state to one of rigor. In spite of left ventricular rigor, right ventricles remained flaccid and could be defibrillated. Ultrastructural studies showed that mitochondria were destroyed in left ventricles in rigor while right ventricular mitochondria were preserved even after two hours of normothermic, ischemic arrest. In either ventricle, glycogen granules were dissipated after two hours. The increased incidence of left ventricular rigor after two hours of normothermic, ischemic arrest compared with one hour of ischemic arrest was highly significant.

Giant left atrium is an unusual finding in mitral valve disease. The chief question about the enlarged atrium is whether to reduce its size by partial excision of its wall. Simple mathematical considerations suggest that partial excision offers no significant hemodynamic benefit.