Newer Inotropic Agents in the Management of Arrhythmias Associated With Cardiac Failure

Abstract

While a number of anti-arrhythmic drugs are currently available for the control of both atrial and ventricular arrhythmias, these drugs all have the relative disadvantage of a negative inotropic characteristic. Other than digitalis, there are no anti-arrhythmic drugs in current use that possess the inotropic effect that may be required in patients who have arrhythmias with associated heart failure.We have been interested in the use of three newer agents possessing this characteristic, i.e. phentolamine, glucagon and bretylium tosylate. These drugs have been studied in a series of patients with varying types of arrhythmias associated with congestive heart failure and the efhcacy of these agents will be listed in subsequent paragraphs. METHOD OF STUDYEleven patients with arrhythmias and heart failure were given glucagon in a dose of 3 mg., intravenously, at 20 minute intervals for three doses and then placed on an infusion of 10 mg./hour for periods of four to eight hours. Thirteen patients with similar type arrhythmias and heart failure were given phentolamine in a dose of .3 mg./minute, intravenously, for periods of 15 to 60 minutes. Fifteen patients with arrhythmias and heart failure were given bretylium tosylate in a dose of 5 mg./kg. in a single intravenous dose and then 5 mg./kg., intramuscularly, at six hour intervals for four doses.The varying arrhythmias studied are shown in Table 1. Characteristics of the patient population are shown in Table 2. Patients were all followed by frequent electrocardiographic studies, clinical assessment of failure, central venous pressure monitoring in some cases, determination of changes in urinary output and frequent determinations of blood pressure. Table 3 illustrates the efhcacy of these differing agents on the control of the arrhythmias studied. RESULTS OF STUDYIt can readily be seen that the majority of arrhythmias showed improvement with each of the agents tested with premature ventricular contractions respondat CARLETON UNIV on July 3, 2015 ang.sagepub.com Downloaded from

Further evaluation of phentolamine (‘Regitine’) in cardiac arrhythmias

“…3.6 Phentolarnine is the only antiarrhythmic drug in current clinical use, other than digitalis, which has a positive inotropic effect. 7 In an earlier study, we reported the favourable effects of the drug in ventricular arrhythmias not due to digitalis; the dosage used was 0.3 mg. per min. I.V.…”