Comparative hemodynamics of antiarrhythmic drugs.

It is important to consider the hemodynamic effects of antiarrhythmic drugs, because the majority of patients who require these drugs already have compromised cardiac function. The presently available antiarrhythmic agents vary in their potential for producing negative inotropic effects on the myocardium; they vary, as well, as to the mechanisms by which these effects are produced. The drugs in each of the Vaughan-Williams' classes are discussed in terms of the extent to which they affect cardiac output and the mechanisms by which they may depress cardiac function. Practically all antiarrhythmic agents can decrease cardiac output when administered intravenously. However, when given orally to patients with congestive heart failure, amongst Class I agents, encainide and mexilitine appear to have a reasonably good safety record with respect to the worsening of congestive heart failure. Class III antiarrhythmics also appear to be well tolerated in patients with severe LV dysfunction.