EFFECTS OF PSYCHOPHARMACOLOGIC AGENTS ON MYOCARDIAL CONTRACTILITY

¹ Cardiology Branch, National Heart and Lung Institute and Laboratory of Clinical Science, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland

Although psychopharmacologic agents are widely used as adjuncts in the management of patients with cardiac disease, their effects on myocardial contractility are unknown. Accordingly, we studied the effects of lithium chloride, chlorpromazine (Thorazine), diazepam (Valium) and chlordiazepoxide (Librium) on the intrinsic contractile properties of isolated cat papillary muscles. Lithium chloride at a concentration of 4.0 mEq/ liter significantly increased peak isometric tension and the rate of tension development (dT/dt). Tension at 10 mEq/liter increased by an average of 0.9±0.2 g/mm² or 21% from control . At this concentration dT/dt increased 7.9±2.2g/mm²/sec or 33% from control Chiorpromazine and chlordiazepoxide produced no changes at concentrations that encompassed the range of blood levels found in patients being treated with these drugs. However, at higher concentrations decreases in tension and dT/dt were observed. The addition of diazepam over a wide range of concentrations failed to produce any significant changes in papillary muscle contractility.