Intravenous administration of diltiazem in the treatment of supraventricular tachyarrhythmias.

Unlabelled: The aim of the study was to investigate the efficacy of diltiazem bolus intravenous administration, compared to disopyramide, in the treatment of various types of paroxysmal supraventricular tachyarrhythmias.

Method: Fifty patients (23 males, 27 females, mean age 47.7 +/- 15.2 years) with paroxysmal supraventricular tachyarrhythmia (20 with paroxysmal atrial tachycardia, 23 with paroxysmal atrial fibrillation and rapid ventricular response and 7 with atrial fluttering) were studied. Diltiazem at a dose of 0.25-0.30 mg/kg BW or disopyramide at a dose of 50 mg were given bolus IV. If conversion of the arrhythmia to sinus rhythm could not be achieved with the initial drug, the alternate was given. The order of administration of the drugs was random, independent of the type of the arrhythmia. Before and during drug administration detailed clinical examination and frequent blood pressure (BP) measurements were performed. Twenty-four hour Holter monitoring was done in all patients, starting with the administration of the antiarrhythmic drug.

Results: 1) Paroxysmal atrial tachycardia: diltiazem administration converted the arrhythmia to sinus rhythm in all patients while disopyramide in only 1 of 9 patients who received this drug. 2) Paroxysmal atrial fibrillation: disopyramide converted the arrhythmia in 5 patients without significant change in ventricular response in the others. Diltiazem did not convert the arrhythmia though it caused significant decrease in ventricular response (< 100 bpm) and in 1 patient an important bradycardia (45 bpm). 3) Atrial fluttering: disopyramide converted the arrhythmia to sinus rhythm in 1 patient without significant change in the ventricular response in the others. Diltiazem caused significant decrease in the ventricular response without conversion to sinus rhythm. During conversion to sinus rhythm an AV junctional rhythm of short duration (< 1 min) was noticed in 5 patients and a short pause (< 2 sec) with or without an initial premature contraction in the remaining 21. Disopyramide administration was not associated with side effects. Diltiazem administration cause small (< 20 mm Hg), transient (< 30 min) decrease of BP without symptoms with the exception of the patient with bradycardia in whom the BP decrease was significant (90/60 from 160/80 mm Hg) followed by intense symptoms which lasted for six hours.

Conclusions: Diltiazem administration is extremely effective in conversion of paroxysmal atrial tachycardia to sinus rhythm. In addition it retards ventricular response in patients with atrial fibrillation and fluttering. Compared to disopyramide these effects of diltiazem are more pronounced and clinically pertinent.