Antagonism of drug-induced pulsus alternans in dogs

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Abstract
Pulsus alternans and pseudoalternans were produced in dogs anesthetized with pentobarbital by intravenous injections of moderate doses of one of several pharmacologic agents. Ventricular alternation was alleviated or abolished by a) drugs with positive inotropic action, b) drugs that reduced peripheral resistance, and c) drugs with antiarrhythmic activity. Digoxin and ouabain shortened the periods of drug-induced alternation. Norepinephrine and aminophylline promptly abolished pulsus alternans which had been experimentally established. Electrical stimulation of the cardiac sympathetic nerves resembled injected norepinephrine. Moderate does of nitroglycerin and large doses of histamine terminated pulsus alternans which had been evoked by methoxamine. Smaller doses of histamine were not always effective. Hexamethonium abolished alternation in the absence of marked vasoconstriction, but was ineffective against methoxamine-induced alternans. Hemorrhage from a large artery was effective. Quinidine promptly relieved pulsus alternans, as did two experimental antiarrhythmic drugs, o-methylcyclizine and B.W. 51–41. Procaine amide was not effective.