A 50-year-old female presents to your ER with a chief complaint of palpitations. A 12-lead ECG shows supraventricular tachycardia at a rate of 165 bpm, and she is put on telemetry. She is clinically stable. You attempt the modified Valsalva maneuver with no effect. You explain that you will have to give her medication to bring her heart rhythm back to normal. She asks if you will give her “that adenosine drug” and shudders as she recalls hearing from a friend who presented to the hospital with a similar complaint that “it felt like she was dying.”
Supraventricular tachycardia (SVT) is a common arrhythmia seen in the ER, encompassing multiple abnormal rhythms such as atrial fibrillation, atrial flutter, atrioventricular reentrant tachycardia, and atrioventricular nodal reentrant tachycardia. Unstable patients typically require cardioversion for initial management. However, stable patients can be medically managed with medications focused on decreasing conduction through the atrioventricular (AV) node.
Current General Practice
The typical first medication for managing stable SVT is an adenosine push. However, most patients complain that the primary side effect of this medication is the sensation of “impending doom” due to the sinus pause.1 Other side effects include headache, dizziness, facial flushing, and dyspnea. Are there other options that could be used as first-line therapy for stable SVT?
The Evidence for Diltiazem
Diltiazem is a non-dihydropyridine calcium channel blocker. A 2017 Cochrane systematic review of 7 RCTs (622 patients) found similar conversion rates to sinus rhythm with adenosine or calcium channel blockers (90% versus 93%) and no significant difference in significant adverse events.1 This data was incorporated into the 2020 American Heart Association guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care.2 Some differences between the two medications included more adverse events with adenosine than diltiazem, with a longer time to conversion for diltiazem (6.5 minutes) compared to adenosine (1.48 minutes).3,4 Diltiazem can be given as a slow IV infusion of 2.5mg/min or an IV push of 0.25mg/kg.
One common concern regarding using calcium channel blockers for SVT is the possible side effect of hypotension. In the past, this was more of a concern with the use of verapamil as opposed to diltiazem. However, as mentioned above, recent systematic reviews found no appreciable difference in significant adverse events (including hypotension) between diltiazem and adenosine.
As a reminder, both adenosine and diltiazem are contraindicated in pre-excitation syndromes such as Wolf-Parkinson White, as use may lead to ventricular fibrillation.
Diltiazem is a reasonable consideration as a first-line alternative to adenosine for converting stable SVTs. Systematic reviews have shown no difference in rates of conversion or significant adverse effects between diltiazem and adenosine. In addition, while diltiazem takes longer to take effect, it results in a more comfortable patient experience without the unpleasant “heart-stopping” sensation of adenosine.
Back to Case
You mention that another medication, diltiazem, may be used, which has a similar success rate and would not cause the uncomfortable “heart-stopping” sensation of adenosine. It will, however, require more time to take effect. Nevertheless, the patient quickly decides to go with this new option and is given diltiazem with a successful conversion to sinus rhythm.
This post was copyedited by Saad Razzaq
Reviewing with the staff
Diltiazem is safe, effective and well tolerated by patients in treating supraventricular tachycardia. Unfortunately, it is an often-overlooked alternative to adenosine. I hope that increased awareness of the evidence will lead to shared decision-making in the treatment of SVT.