Vasopressin in Bradyarrhythmia from Inferior STEMI
Yes, vasopressin is indicated as a positive chronotropic medication for hemodynamically unstable bradyarrhythmia in inferior STEMI, specifically when there is hemodynamic intolerance or high-degree AV block without a stable escape rhythm. 1
Clinical Context
Bradyarrhythmias are common in inferior STEMI due to increased vagal tone (Bezold-Jarisch reflex) and typically involve supra-Hisian AV block that often resolves spontaneously or after reperfusion. 1, 2 However, when hemodynamic compromise occurs, immediate intervention is required to prevent mortality.
Treatment Algorithm
First-Line Therapy: Atropine
- Atropine remains the initial drug of choice for symptomatic bradycardia with hemodynamic compromise (heart rate <50 bpm with systolic BP <80-90 mmHg). 1, 2
- Dosing: 0.5-1.0 mg IV bolus, repeated every 3-5 minutes to maximum 3 mg total dose. 1, 2
- Target: Achieve minimally effective heart rate (approximately 60 bpm). 2
Second-Line: Vasopressin and Other Chronotropic Agents
When atropine fails or is insufficient, the 2017 ESC Guidelines explicitly recommend intravenous positive chronotropic medications including epinephrine, vasopressin, and/or atropine as Class I, Level C indication. 1
Alternative pharmacologic agents include: 2
- Epinephrine: 2-10 mcg/min IV or 0.1-0.5 mcg/kg/min IV, titrated to effect
- Dopamine: 5-20 mcg/kg/min IV, starting at 5 mcg/kg/min, increasing by 5 mcg/kg/min every 2 minutes
- Isoproterenol: 1-20 mcg/min (use with caution due to increased myocardial oxygen demand)
Third-Line: Temporary Pacing
- Temporary pacing is indicated when positive chronotropic medications fail. 1
- Transcutaneous pacing is preferred for immediate intervention, while transvenous pacing is considered if prolonged support is anticipated. 2
Critical Considerations
Urgent Revascularization
Urgent angiography with revascularization is indicated if the patient has not received previous reperfusion therapy, as this addresses the underlying cause of the bradyarrhythmia. 1, 2
Atropine Cautions
While atropine is first-line, use with caution as it may cause: 3
- Loss of protective parasympathetic tone against ventricular fibrillation
- Myocardial infarct extension
- Adverse effects correlate with doses >1.0 mg initially or cumulative doses >2.5 mg over 2.5 hours
Expected Course
AV block in inferior MI typically resolves within 72 hours as acute ischemia improves with reperfusion. 2 Continuous ECG monitoring for progression of conduction abnormalities is essential. 2
Key Pitfall to Avoid
Do not withhold vasopressin or other chronotropic agents while waiting for temporary pacing setup in hemodynamically unstable patients. The ESC Guidelines place vasopressin at the same recommendation level (Class I) as atropine for this specific indication, making it a legitimate and guideline-supported option when bradycardia with hemodynamic intolerance persists. 1