Verapamil in the Management of Supraventricular Tachyarrhythmias Occurring after a Recent Myocardial Infarction FRANS HAGEMEIJER

DURING THE ACUTE phase of myocardial infarction in man, supraventricular tachyarrhythmias may be observed in 10% of all patients." 2 Their onset is often heralded by frequent supraventricular extrasystoles, which may escape detection by conventional monitoring techniques. The mechanism of their genesis is still debated: atrial stretch caused by incipient ventricular failure, ischemia of the sinus node, atrial infarction, or pericardial effusion with mechanical stimulation of the atria. A sustained supraventricular tachyarrhythmia may require emergency treatment when a very rapid ventricular response is associated with severe anginal pain or with a marked drop in blood pressure and in cardiac output. Even when it seems well tolerated, a rapid heart action exerts unfavorable effects on ischemic myocardium by increasing oxygen requirements. Supraventricular tachyarrhythmias may thus increase the extent of ischemia and the area of necrosis. Verapamil has been shown3"8 to terminate many supraventricular tachyarrhythmias rapidly, or at least to slow the ventricular response by a prolongation of atrioventricular conduction time.91 The other cardiovascular actions of verapamil include a slight slowing of the sinus rate;5' 9, 10, 12, 13 arterial vasodilation, particularly of the coronary arteries, with an associated drop in blood pressure;'2, 13 negative inotropic properties are observed at doses higher than those usually given in clinical practice.6" 12, 14, 15 Profound hypotension and cardiac arrest have been reported when verapamil was administered to patients in severe heart failure or those treated simultaneously with beta-blocking agents,4 16-20 resulting probably from the calcium antagonistic properties of verapamil.'3' 18, 21-24 A calcium antagonist could be dangerous in the acute phase of myocardial infarction if these hearts are abnormally sensitive. Reported therapeutic trials3'8 included few patients with a recent myocardial infarction; no dangerous side effects were observed. We therefore investigated the safety and therapeutic effectiveness of titrated doses of verapamil administered intravenously to patients with a prolonged supraventricular tachyarrhythmia occurring shortly after an acute myocardial infarction. following: reversion to sinus rhythm; a ventricular rate slower than 100/min; hypotension; a pulmonary capillary wedge pressure rising above 15 mm Hg; signs of intolerance; a maximum dose of 20 mg. Reversion to sinus rhythm was observed in 7/8 patients in atrial flutter and in 1/8 patients in atrial fibrillation; in all the ventricular rate could be slowed below 100/min without untoward effects.