CARDIODEPRESSION BY CLASS-I ANTIARRHYTHMIC DRUGS - EVIDENCE OF THE HEMODYNAMICALLY EFFECTIVE COMPONENTS

Cardiodepression is a potential unwanted side effect of an antiarrhythmic drug therapy. Such drug-induced impairment of left ventricular pump function which clinically may amount to critical dimensions derives from both, central (contractility) and peripheral (preload, afterload) influences. Conventional parameters like ejection fraction and cardiac index are load-dependent and, therefore, are unfit to serve as parameters of contractility changes. Therefore, the analysis of the endsystolic pressure-volume relations was used which presently (due to its load insensitivity) is considered the most sensitive index of left ventricular contractility. In 5 study groups comprised of patients with still normal ventricular function we assessed hemodynamics and contractility changes as induced by 5 different class-I antiarrhythmic drugs and compared the results with those of respective study results in the literature. The drug-induced impairment of regular parameters of ventricular function was quantitatively rather moderate (between 8 and 30%), but it was variable and not amenable to statistical evaluation. A decline in contractility was found: by 34% at rest and by 24% during stimulated tachycardia; without significant differences being encountered between drug effects. The diminished contractility (proven here by load-independent methodology) as induced by class-I antiarrhythmic drugs, apparently was humorally adequately compensated for, since no clinical symptomatology was encountered. However, in patients with impaired ventricular function beyond NYHA-class III cardiodepression from antiarrhythmic acting drugs could be expected to be more marked.