Elsevier

Resuscitation

Volume 80, Issue 5, May 2009, Pages 523-528
Resuscitation

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

https://doi.org/10.1016/j.resuscitation.2009.01.017Get rights and content

Abstract

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 1 mg per minute up to a maximum dose of 20 mg, or diltiazem at a rate of 2.5 mg per minute up to a maximum dose of 50 mg. 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 2 h 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.

Introduction

Paroxysmal supraventricular tachycardia (SVT) is a common cardiac emergency presenting to the Emergency Department (ED). Since the 1970s intravenous verapamil has been the drug of choice1, 2 for the treatment of SVT. The 1986 American Heart Association guidelines for Cardiopulmonary Resuscitation and Emergency Cardiac Care recommended that verapamil be given as a 2.5–5 mg intravenous bolus over 2 min and 5–10 mg over 2 min to be given after 15–30 min of the first dose if the SVT persisted3 or recurred and if blood pressure remains acceptable. For the 1992 American Heart Association Guidelines, adenosine was recommended as the initial drug of choice for haemodynamically stable paroxysmal SVT. The sequence of agents recommended was adenosine twice (6 mg followed by 12 mg). If the blood pressure had not dropped and the SVT persisted up to two doses of verapamil (2.5–5 mg) intravenous over 2 min followed by 5–10 mg over 2 min could be given. When treating the elderly or when blood pressures were within the lower range of normal, smaller doses (2–4 mg) of verapamil over a longer period (3–4 min) were recommended for the first dose.4 The main reason given for adenosine as the first choice drug was that adenosine does not cause hypotension to the same degree as verapamil because adenosine has a very short half-life (<10 s).

A previous randomized controlled trial (161 patients) by our group compared intravenous verapamil and intravenous diltiazem5 given as slow infusions (verapamil at a rate of 1 mg per minute and diltiazem at a rate of 2.5 mg per minute). This showed a conversion rate of more than 97% with only one patient (1%) developing hypotension. This finding suggests that the haemodynamic instability previously attributed to verapamil may be related to the speed of verapamil administration.

There are few studies directly comparing the effectiveness of adenosine and calcium channel blockers. Most of these studies recruited subjects with laboratory-induced SVT.6, 7, 8 In addition, they used a rapid bolus of intravenous calcium channel blocker given over 15 s (except for the study by Hood and Smith).7 These studies generally conclude that adenosine and verapamil are both highly effective in the termination of SVT.

There has been no previous large prospective, randomized controlled trial comparing the usefulness of intravenous adenosine vs. slow-infusion calcium channel blockers in a clinical patient-care environment. The aim of this study was to compare the efficacy and safety of bolus intravenous adenosine with the slow infusion of verapamil or diltiazem, in the termination of spontaneous SVT in the ED.

Section snippets

Methods

This was a prospective, randomized, controlled clinical trial in patients presenting with SVT to an ED. The study was approved by the hospital Ethics Committee.

Results

From 1st January 1997 to 31st March 1999, over a 27-month period, a total of 236 patients with regular narrow complex tachycardia not converted by vagal maneuvers were treated by, the Singapore General Hospital ED. Of these, none were pregnant by clinical history, and 3 had signs of impaired cerebral perfusion or heart failure. All three had concomitant medical problems and all were converted with 6 mg IV bolus of adenosine. The remaining 233 patients were enrolled into the trial.

Twenty-seven

Discussion

Verapamil, diltiazem and adenosine compounds exert their maximum effect on the AV node by lengthening intranodal conduction time significantly.10, 11 The effect of calcium channel blockers on paroxysmal SVT has been best studied with verapamil. Early studies suggest that adequate dosage of verapamil resulting in an initial plasma concentration exceeding 72 ng/ml is needed to effect conversion.12 These concentrations were then achieved by giving bolus doses of verapamil at 0.075–0.15 mg/kg body

Conclusion

Calcium channel blockers administered as a slow infusion offer an alternative to adenosine in the emergency treatment of stable SVT patients. In our study slow calcium channel blocker infusions were more effective than bolus IV adenosine 6 mg followed by 12 mg in converting stable spontaneous SVT. Calcium channel blockers are safe and affordable for healthcare systems where the availability of adenosine is limited.

Conflict of interest statement

We hereby declare that there is no conflict of interest in conducting this randomized clinical trial.

Acknowledgement

We wish to acknowledge the Department of Clinical Research, Singapore General Hospital for funding of adenosine and diltiazem.

References (22)

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    *

    A Spanish translated version of the summary of this article appears as Appendix in the final online version at doi:10.1016/j.resuscitation.2009.01.017.

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