Abstract and Introduction
Abstract
Introduction Patients with cardiac arrhythmias are generally instructed to avoid caffeine intake. A comprehensive evaluation of the electrophysiological effects of caffeine on atrial and ventricular tissues in humans has not previously been performed.
Methods and Results Eighty patients (31 men, mean age 49 ± 14 years) with symptomatic supraventricular tachycardia (SVT) undergoing an electrophysiologic study (EPS) prior to catheter ablation were randomized to receive oral caffeine or placebo. Caffeine at a dosage of 5 mg/kg (moderate intake) or placebo tablets were administered orally at a mean time of 57 ± 13 minutes prior to the EPS. The median (IQR) caffeine level in patients receiving caffeine was 7.4 μg/mL (4.7–8.7), as compared with 0.15 (0.00–0.61) in patients receiving placebo, P < 0.0001. Caffeine was associated with a significant increase in resting systolic and diastolic blood pressures as compared with placebo, while the resting heart rate was not significantly different between both groups. Caffeine was not associated with significant effects on the effective refractory period of the atrium or ventricle, as well as on AV node conduction. SVT was induced in all but 3 patients; there was no significant difference between groups receiving placebo or caffeine on SVT inducibility or the cycle length of induced tachycardias.
Conclusions Caffeine, at moderate intake, was associated with significant increases in systolic and diastolic blood pressures, but had no evidence of a significant effect on cardiac conduction and refractoriness. Furthermore, no effect of caffeine on SVT induction or more rapid rates of induced tachycardias was found.
Introduction
Caffeine has become widely available for consumption, with potentially large quantities associated with energy drinks. In clinical practice, patients with a history of cardiac arrhythmias are typically instructed by their physician to discontinue caffeine intake. There have been few reports of invasive electrophysiologic evaluation of the effects of caffeine in animals and patients. Studies in cardiac patients or volunteers reported electrophysiological effects on atrial, AV node, or ventricular refractoriness that suggested the potential for caffeine intake to be detrimental in patients with supraventricular tachycardia (SVT) or other cardiac arrhythmias. The objective of this prospective randomized placebo controlled study was to determine if caffeine in moderate amounts was associated with cardiac electrophysiology effects.