Fig. 2. In vivo left ventricular contractilities (LV dP/dt) and mean left ventricular pressures (LVP) are shown in the first 10 min after administration of 2 mg/kg succinylcholine at time = 0 min for the same animals as in fig. 1. Succinylcholine caused a significant decrease of LV dP/dt and mean LVP in MHS, MHS D (dantrolene), but not in MHS V (vecuronium) or normals. The number sign indicates the administration of epinephrine, and the changes in cardiac function in MHS V1 was considered to be caused by an air embolus (*).