Should Metoprolol Be Held Before Cardioversion?
No, metoprolol should not be held before cardioversion for atrial fibrillation. Beta-blockers like metoprolol do not interfere with the cardioversion procedure itself and should be continued to control heart rate and potentially improve maintenance of sinus rhythm after successful cardioversion 1, 2.
Rationale for Continuing Metoprolol
Beta-blockers do not reliably terminate atrial fibrillation or facilitate electrical cardioversion, but they serve important supportive roles 1. The primary concerns around cardioversion relate to anticoagulation management and hemodynamic stability, not beta-blocker therapy 1.
Key Supporting Evidence:
Metoprolol improves post-cardioversion outcomes: Research demonstrates that metoprolol CR started before cardioversion and continued afterward significantly increases the proportion of patients maintaining sinus rhythm at 6 months (46% vs 26% with placebo, p<0.01) 3.
Rate control during procedure: If cardioversion fails or the patient reverts to atrial fibrillation, metoprolol provides ventricular rate control, reducing heart rate during atrial fibrillation episodes (98 ± 23 beats/min with metoprolol vs 107 ± 27 beats/min with placebo) 4.
No guideline recommendation to hold: Major guidelines from the AHA/ACC/HRS, ESC, and European Heart Journal make no recommendation to discontinue beta-blockers before cardioversion 1.
Important Caveats and Monitoring
Bradycardia Risk
Monitor for severe bradycardia after cardioversion, as metoprolol can cause bradycardia, sinus pause, heart block, and cardiac arrest 5. Patients with first-degree AV block, sinus node dysfunction, or conduction disorders are at increased risk 5.
Hemodynamic Considerations
The FDA label warns that chronically administered beta-blocking therapy should not be routinely withdrawn prior to major surgery, but acknowledges the impaired ability of the heart to respond to reflex adrenergic stimuli may augment risks 5. However, cardioversion is not a surgical procedure requiring general anesthesia in most cases, and the benefits of continued rate control typically outweigh theoretical concerns.
Specific Contraindications
Do not use metoprolol in patients with:
- Decompensated heart failure or cardiogenic shock 5
- Severe bradycardia or high-degree AV block without pacemaker 5
- Active bronchospasm (relative contraindication) 5
Clinical Algorithm
Assess hemodynamic stability: If the patient is hemodynamically unstable, proceed immediately with electrical cardioversion while initiating anticoagulation 1.
Continue metoprolol at current dose: Do not hold or reduce the dose before cardioversion unless contraindications exist 2, 3.
Ensure adequate anticoagulation: For AF duration >48 hours or unknown duration, ensure therapeutic anticoagulation for at least 3 weeks before cardioversion, or perform TEE to exclude thrombus 1.
Monitor post-cardioversion: Check heart rate and rhythm after cardioversion, watching for bradycardia or conduction abnormalities 5.
Continue metoprolol long-term: Maintain beta-blocker therapy after successful cardioversion to reduce recurrence risk 3, 4, 6.
Common Pitfalls to Avoid
Do not abruptly discontinue metoprolol in patients with coronary artery disease, as this can cause severe exacerbation of angina, myocardial infarction, and ventricular arrhythmias 5.
Do not confuse cardioversion anticoagulation protocols with beta-blocker management: The critical pre-procedure consideration is anticoagulation status, not beta-blocker therapy 2.
Do not assume beta-blockers will facilitate cardioversion: While they improve post-cardioversion sinus rhythm maintenance, they do not enhance the acute success of electrical or pharmacological cardioversion 1.