DIRECT DEPRESSION OF MYOCARDIAL CONTRACTILITY BY THE AEROSOL PROPELLANT GAS, DICHLORODIFLUOROMETHANE

¹ Department of Medicine, Section of Cardiology, University of Illinois Hospital and College of Medicine, Chicago, Illinois

To determine if fluoroalkane propellant gases have a direct negative inotropic action, perhaps contributing to the death of youths who inhale these gases for intoxicant purposes, we investigated the effects of the most commonly used one, dichlorodifluoromethane (Freon 12), on the in vitro contractile performance of 35 rat left ventricular papillary muscles. Without changing compliance of the series elastic element and with little effect on time to peak isometric tension, dichlorodifluoromethane at a bath concentration of 11.35 mg/100 ml quickly and reversibly reduced the amount and rate of isometric force development and the extent and velocity of isotonic shortening to (mean ± S.E.) 33 ± 2, 36 ± 1, 51 ± 3 and 48 ± 3% of control and shifted force-velocity curves markedly downward and to the left. The negative inotropic effects of dichlorodifluoromethane occurred whether the bath was well oxygenated or deoxygenated. These effects were dose-related, with the lowest concentration of dichlorodifluoromethane in the bath fluid, 1.06 mg/100 ml, causing approximately a 20% depression in the amount and rate of isometric force development. These results show that dichlorodifluoromethane is directly toxic to ventricular myocardium and suggest that depression of myocardial contractile state may play a role in the sudden death of youths who deliberately inhale aerosol propellants.