What is the role of verapamil (calcium channel blocker) in treating premature atrial contractions (PACs) and premature ventricular contractions (PVCs)?

Role of Verapamil in Treating PACs and PVCs

Verapamil is effective for treating premature ventricular contractions (PVCs) in patients with structurally normal hearts, but has limited utility for premature atrial contractions (PACs). 1

Mechanism of Action

• Verapamil is a calcium channel blocker that works by slowing conduction through the AV node and increasing AV node refractoriness 1, 2
• It selectively blocks calcium ion influx across cell membranes of arterial smooth muscle and cardiac conductive/contractile cells 2
• This mechanism makes it particularly effective for arrhythmias involving the AV node 3

Efficacy for PVCs

• In patients with symptomatic PVCs in an otherwise normal heart, verapamil is recommended as a first-line treatment alongside beta-blockers 1
• Clinical studies show verapamil has moderate efficacy (15% response rate) in suppressing idiopathic PVCs, though less effective than propafenone (42% response rate) 4
• For patients with suspected PVC-induced cardiomyopathy, class IC antiarrhythmic drugs have shown better efficacy than calcium channel blockers 5

Efficacy for PACs

• Verapamil has limited evidence supporting its use specifically for isolated PACs 1
• It may reduce heart rate during PAC episodes, potentially making symptoms less noticeable, but does not significantly reduce PAC frequency 1

Special Considerations

Interfascicular Reentrant VT (Belhassen Tachycardia)

• Verapamil is highly effective for a specific type of ventricular tachycardia called verapamil-sensitive idiopathic left ventricular tachycardia (interfascicular reentry) 1
• For sustained hemodynamically tolerated verapamil-sensitive idiopathic LVT, intravenous verapamil is recommended for VT termination 1
• Chronic therapy with oral verapamil can be useful for recurrent verapamil-sensitive idiopathic LVT 1

Short-Coupled Torsade de Pointes

• Intravenous verapamil should be considered to acutely suppress or prevent electrical storm or recurrent ICD discharges in patients with short-coupled torsade de pointes 1
• However, this is a rare condition requiring specialized management and typically ICD implantation 1

Dosing Guidelines

• For intravenous administration in acute settings: 5-10 mg over 60 seconds 1
• For oral administration in chronic management: starting dose of 120 mg daily, which can be titrated up to 480 mg daily in divided doses 3

Contraindications and Precautions

• Verapamil is contraindicated in patients who have taken beta-blockers due to risk of profound bradycardia and hypotension 1, 6
• Should not be used in patients with Wolff-Parkinson-White syndrome with atrial fibrillation/flutter 1, 3
• Contraindicated in patients with significant left ventricular dysfunction, increased risk for cardiogenic shock, and second or third-degree AV block without a cardiac pacemaker 6
• Use with caution in patients with heart failure or impaired ventricular function 3

Treatment Algorithm

1. First-line therapy for symptomatic PVCs in structurally normal hearts:

   • Beta-blockers or non-dihydropyridine calcium channel blockers (including verapamil) 1

2. If first-line therapy is ineffective or not tolerated:

   • Consider other antiarrhythmic medications 1
   • Consider catheter ablation, especially for patients with frequent symptomatic PVCs 1, 4

3. For verapamil-sensitive idiopathic LVT:

   • Intravenous verapamil for acute termination 1
   • Oral verapamil for chronic management 1

4. For PACs:

   • Limited role for verapamil; beta-blockers are generally preferred 1

Clinical Pearls

• Radiofrequency catheter ablation has shown superior long-term efficacy (88%) compared to antiarrhythmic drugs for symptomatic idiopathic PVCs 4
• Verapamil is more effective for supraventricular arrhythmias than for most ventricular arrhythmias, with the exception of specific types like interfascicular reentrant VT 7
• The response to verapamil can help differentiate the mechanism of arrhythmias in some cases, as certain VTs are verapamil-sensitive while others are not 1