So I Don’t Have to Feel Like Death?

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Rachel Rafeq
Emergency medicine pharmacist and toxicology enthusiast. Trained in medication safety and I apply that to everything. I love photography and world schooling my kids.

The Pre-brief

  • Supraventricular tachycardia (SVT) is a common arrhythmia with a prevalence of 2 per 1000 adults
  • SVT is an umbrella category of rhythm abnormalities that includes atrial fibrillation, atrial flutter, sinus tachycardia, atrioventricular nodal reentrant tachycardia, and atrioventricular reciprocating tachycardia
  • SVTs are often recurrent and sometimes persistent, resulting in 50,000 emergency department visits annually 
  • Clinical presentation includes palpitations, anxiety, light-headedness, chest pain, and dyspnea –  a 12- lead electrocardiogram is essential for diagnosis
  • Treatment goal is to terminate the rhythm by decreasing conduction through the atrioventricular (AV) node
  • Pharmacologic therapy with adenosine has been first line for many years due to it’s ultra-short acting duration and efficacy in terminating regular tachyarrhythmias when caused by AV reentry, but is associated with a number of adverse events and patient discomfort
  • An alternative medication is diltiazem, a non-dihydropyridine calcium channel blocker (CCB)

What is the mechanism of action of Adenosine and Calcium Channel Blockers in stable SVT?

Both adenosine and calcium channel blockers (CCBs) function as AV nodal blockers to help reset the heart back to normal sinus rhythm. Adenosine inhibits cyclic adenosine monophosphate (cAMP) mediated calcium influx and increases potassium conduction. This leads to AV nodal conduction inhibition and prolongs the AV nodal refractory period. CCBs block calcium dependent conduction through the AV node.

What is the issue with Adenosine?

Clinically, adenosine is an appropriate first line agent; however, it is associated with several adverse effects. These effects include headache, dizziness, facial flushing, dyspnea, gastrointestinal distress, and neck discomfort.  Notable is the patient’s feeling that their “heart stopped” or the sensation of an “electric shock”. 

What is the Alternative?

Up until 2020, adenosine remained the first line agent, and has been for the past 10+ years. The 2020 American Heart Association (AHA) guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care provided an update, which stated that there are no appreciable differences in success or major adverse event rates between calcium channel blockers and adenosine.  

In addition, a Cochrane systematic review of seven randomized control trials published in 2018, found similar rates of conversion to normal sinus rhythm between adenosine and non-dihydropyridine CCBs (90% vs 93%). I am specifically shouting out Diltiazem, because although Verapamil is another non-dihydropyridine CCB, it has fallen out of favor due to its higher risk of hypotension compared to adenosine and diltiazem which can destabilize the tachycardia .  The large benefit with using diltiazem is that there is no association with the “electric shock” or “heart stop” feeling that is synonymous  with adenosine. 

What is the Dose and Administration Technique of Diltiazem?

What is the Dose and Administration Technique of Adenosine? 

  • 6 mg rapid intravenous push (IVP) over 1-2 seconds immediately followed by a flush; May repeat 1-2 minutes later with a double dose of  12 mg IVP if SVT is not terminated with the first dose. This can be repeated one additional time for a total of three doses. If administration is via the central line, the initial dose should be decreased to 3 mg. 
  • Notable association with “electric shock” sensation
  • Administration caveats:
    • Flush
      • Requires immediate 20 mL 0.9% sodium chloride flush after dose. This is required because while most drugs are metabolized in the liver, adenosine is metabolized in the erythrocytes and vascular endothelial cells, so it does not make it to the liver. It has a half-life of 10 seconds so the flush is important to help it reach the heart before it is metabolized and excreted.
    • Arm Elevation 
      • Should you elevate the arm upon administration of adenosine? The thought is that arm elevation will help expedite medication delivery and improve the success rate of SVT termination. Most recently, Daengbubpha and colleagues studies this specific intervention (double syringe technique of 6 mg adenosine vs double syringe technique of 6 mg adenosine  plus arm elevation to 90 degrees perpendicular to a horizontal plane for 10 seconds) and found no difference. 
    • Single Syringe 
      • Recent literature has proven that for ease of administration, adenosine may be administered as a single syringe of adenosine plus sodium chloride flush. The dose is prepared as 6 mg of adenosine plus 18-20 mL of 0.9% sodium chloride in a single syringe. If a higher dose is required, it may be administered via the same method. 

Picking Between the Two:

Consider diltiazem when:

  • The patient has had previous negative experiences with adenosine
  • The patient has had frequent relapses despite adenosine administration
  • The patient has had frequent atrial or ventricular ectopic beats and is at risk of early recurrence of the arrhythmia

Consider adenosine when:

  • The patient has poor left ventricular function
  • The patient is on a beta blocker

Do not use either AV nodal blocker if:

  • The patient has history of wolff-parkinson-white (WPW) syndrome 
    • WPW is caused by abnormal electrical conduction through an accessory pathway that bypasses the AV node. Therefore, if AV nodal blockers are used, they will force conduction into the abnormal accessory pathways, exacerbating the syndrome. 

The Debrief

  • When pharmacotherapy is required for stable SVT, adenosine has historically been the drug of choice
  • Diltiazem offers an alternative option with fewer adverse effects, most notably it also eliminates the concerns of “electric shock” sensation and “heart stop” which are characteristic with adenosine
  • The 2020 AHA guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care were updated to state that adenosine is no  longer favorable over calcium channel blockers but rather that there are no appreciable differences between the two agents
  • Consider diltiazem as a slow intravenous infusion 2.5 mg/min for your next stable SVT patient which will not only simplify the administration but also provide a more positive patient experience  


  1. Alabed S, Sabouni A, Providencia R, Atallah E, Qintar M, Chico TJ. Adenosine versus intravenous calcium channel antagonists for supraventricular tachycardia. Cochrane Database Syst Rev. 2017;10(10):CD005154. Published 2017 Oct 12. doi:10.1002/14651858.CD005154.pub4
  2. Alabed S, Providência R, Chico TJA. Cochrane corner: adenosine versus intravenous calcium channel antagonists for supraventricular tachycardia. Heart. 2018;104(24):1993-1994. doi:10.1136/heartjnl-2017-312909
  3. Adenocard® (adenosine) [package insert]. Lake Forest, IL: Hospira Inc; March 2022
  4. Lim SH, Anantharaman V, Teo WS, Chan YH. Slow infusion of calcium channel blockers compared with intravenous adenosine in the emergency treatment of supraventricular tachycardia. Resuscitation. 2009;80(5):523-528. doi:10.1016/j.resuscitation.2009.01.017
  5. Panchal AR, Bartos JA, Cabañas JG, et al. Part 3: Adult Basic and Advanced Life Support: 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2020;142(16_suppl_2):S366-S468. doi:10.1161/CIR.0000000000000916
  6. Daengbubpha P, Wittayachamnankul B, Sutham K, Chenthanakij B, Tangsuwanaruk T. Comparing methods of adenosine administration in paroxysmal supraventricular tachycardia: a pilot randomized controlled trial. BMC Cardiovasc Disord. 2022;22(1):15. Published 2022 Jan 26. doi:10.1186/s12872-022-02464-5
  7. McDowell M, Mokszycki R, Greenberg A, Hormese M, Lomotan N, Lyons N. Single-syringe Administration of Diluted Adenosine. Acad Emerg Med. 2020;27(1):61-63. doi:10.1111/acem.13879
  8. Chhabra L, Goyal A, Benham MD. Wolff Parkinson White Syndrome. [Updated 2021 Aug 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from:

The Debrief

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  1. Reference one here.
  2. more here


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