Slow infusion of calcium channel blockers compared with intravenous adenosine in the emergency treatment of supraventricular tachycardia.

INTRODUCTION: The emergency treatment of supraventricular tachycardia (SVT) has, over the last two decades, changed from verapamil to adenosine primarily owing to documented hypotensive episodes occurring with rapid bolus infusions of the calcium channel blocker. Slow infusions of calcium channel blockers have not previously demonstrated hypotension to any significant degree. The aim of this study was to compare the efficacy and safety of bolus intravenous adenosine and slow infusion of the calcium channel blockers verapamil and diltiazem in the emergency treatment of spontaneous SVT.

METHODS: A prospective randomized controlled trial with one group receiving bolus intravenous adenosine 6 mg followed, if conversion was not achieved, by adenosine 12 mg; and the other group receiving a slow infusion of either verapamil at a rate of 1mg per minute up to a maximum dose of 20mg, or diltiazem at a rate of 2.5mg per minute up to a maximum dose of 50mg. These infusions would be stopped at time of conversion of the SVT or when the whole dose was administered. Heart rate and blood pressure was continuously monitored during drug infusion and for up to 2h post-conversion.

RESULTS: A total of 206 patients with spontaneous SVT were analysed. Of these, 102 were administered calcium channel blockers (verapamil=48, diltiazem=54) and 104 were given adenosine. The conversion rates for the calcium channel blockers (98%) were statistically higher than the adenosine group (86.5%), p=0.002, RR 1.13, 95% CI 1.04-1.23. The initial mean change in blood pressure post-conversion in the calcium channel blocker group was -13.0/-8.1 mmHg (verapamil) and -7.0/-9.4 mmHg (diltiazem) and 2.6/-1.7 mmHg for adenosine. Only one patient in the calcium channel group (0.98%) (95% CI 0.025-5.3) developed hypotension, and none in the adenosine group.

CONCLUSION: Slow infusion of calcium channel blockers is an alternative to adenosine in the emergency treatment of stable patients with SVT. Calcium channel blockers are safe and affordable for healthcare systems where the availability of adenosine is limited.