Introduction
- SVT indicates tachycardia with atrial rates >100 beats per minute
- Immediate direct-current (DC) cardioversion is indicated in hemodynamically unstable patients
- More options available for management of hemodynamically stable patients in SVT of unknown etiology
a. Traditionally excludes ventricular tachycardias and atrial fibrillation (AF)
b. Includes: atrial tachycardias, atrioventricular (AV) junctional tachycardias, and AV reentrant
tachycardias
a. First-line: vagal maneuvers
i. Valsalva maneuver or carotid sinus massage
b. Second-line (strength of recommendation varies by ACC and ESC)
i. Adenosine
ii. IV non-dihydropyridine calcium channel blockers (i.e. diltiazem or verapamil)
iii. IV beta-blockers (i.e. esmolol or metoprolol)
Clinical Detail
| Parameter | Adenosine | Diltiazem | Verapamil |
|---|---|---|---|
| Dose | 6 mg x 1; repeat 12 mg q1-2min x2 if no effect. Can use an initial 12 mg dose if caffeine ingested within 4 hours | 0.25 mg/kg; repeat with 0.35 mg/kg IV in 15 minutes if needed | 2.5 to 5 mg; repeat with 5-10 mg IV every 15-30 minutes |
| Administration | IV bolus as proximal to heart as possible with stopcock or diluted in 20-30 mL normal saline | Slow IV push over 2-5 mins | Slow IV push over 2-5 mins |
| PK | Onset: 20-30 sec; Duration: 10-20 sec | Onset: ~3 min; Duration: 3-4 hours | Onset: 2-7 min; Duration: 2-5 hours |
| Adverse Effects | Dyspnea, chest tightness, dizziness, headache, facial flushing, nausea, “electric shock” sensation, transient AV block | Hypotension, worsening heart failure, bronchospasm, bradycardia; caution in >1st degree AV block or SA node dysfunction | Hypotension, worsening heart failure, bronchospasm, bradycardia; caution in >1st degree AV block or SA node dysfunction |
| Mechanism of Action | Slows conduction through the AV node through a different mechanism, binding to A1 receptors | Inhibits calcium ion from entering slow channels or select voltage-sensitive areas of vascular smooth muscle and myocardium during depolarization | Inhibits calcium ion from entering slow channels or select voltage-sensitive areas of vascular smooth muscle and myocardium during depolarization |
| Conversion Rate | — | 87-92% | 86-98% |
| Caution | Contraindicated in preexcitation rhythms such as Wolff-Parkinson-White syndrome (WPW) | Contraindicated in preexcitation rhythms such as Wolff-Parkinson-White syndrome (WPW) | Contraindicated in preexcitation rhythms such as Wolff-Parkinson-White syndrome (WPW) |
| Comments | PEARL: Draw up adenosine dose in 20 mL syringe then qs to 20 mL with normal saline and use to IV fast push | PEARL: Administering 1-2 grams of calcium gluconate prior to diltiazem administration may limit hypotension | — |
Evidence
| Author, year | Design / sample size | Intervention & Comparison | Outcome |
|---|---|---|---|
| Sternbach et al. 1986 | Observational; n=11 | IV diltiazem 0.25 mg/kg over 5 min | Conversion in 64% patients; significant ↓ in HR and ↓ SBP of 12.4 mmHg |
| McCabe et al. 1991 | Observational; n=37 | IV adenosine 6 mg rapid push then 12 mg q2 min x2 if no effect | 88% conversion in patients with SVT |
| Hood et al. 1992 | Prospective, crossover, RCT; n=25 | I1 = IV adenosine administered in rapid 40 mcg/kg increments q2 min up to 20 mg; I2 = IV verapamil at 70 mcg/kg administered over 5 min and repeated q5 min up to 15 mg | No significant difference in conversion; ↑ SBP after conversion with adenosine; no change in mean SBP after conversion with verapamil |
| Gausche et al. 1994 | Observational; n=129 | IV adenosine 12 mg rapid push, repeated x1 after 2 min if no effect | 85% conversion with the first dose; 31% conversion with the second dose; 24% of patients appeared in severe distress after administration |
| Lim et al. 2002 | Prospective, RCT; n=184 | IV verapamil 1 mg/min up to 20 mg vs. IV diltiazem 2.5 mg/min up to 50 mg | 98.8% conversion rate for verapamil; 96.3% conversion rate for diltiazem; no significant differences in success rate |
| Lim et al. 2009 | Prospective, RCT; n=206 | I = either IV verapamil 1 mg/min up to 20 mg or IV diltiazem 2.5 mg/min up to 50 mg total; C = IV adenosine 6 mg followed by 12 mg if needed | ↑ conversion rate with CCBs (98% vs. 86.5%); 1 patient developed hypotension with CCBs; mean SBP drop of 13 mmHg with verapamil and 7 mmHg with diltiazem |
| Alabed et al. 2017 | Cochrane review; n=622 | Adenosine vs CCBs at variable doses | No significant difference in conversion rate (89.7% vs. 92.9%); 1 reported case of hypotension in CCB group not requiring treatment |
Conclusions
patients. The decrease in systolic blood pressure may not be much of a concern if patients are normotensive. There is
not enough evidence to recommend one agent over in the absence of contraindications to either age
References
Brugada et al. European Heart Journal. 2019;00:1-66
Page et al. Circulation. 2015;133:506-74
Adenosine [Lexi-drugs]
Diltiazem [Lexi-drugs]
McDowell et al. Acad Emerg Med. 2020;27(1):61-3
Sternbach et al. Clin Cardiol. 1986;9:145-49
McCabe et al. Ann Emerg Med. 1992;21(4):358-61
Hood et al. American Heart Journal. 1992;123:1543-49
Gausche et al. Ann Emerg Med. 1994;24(2):183-89
Lim et al. Resuscitation. 2002;52:167-74
Lim et al. Resuscitation. 2009;80:523-28
Alabed et al. Cochrane Database. 2017;10:1-36
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