Is it safe to start a patient with Wolff-Parkinson-White syndrome on metoprolol?

Metoprolol is Contraindicated in Wolff-Parkinson-White Syndrome

Beta-blockers like metoprolol are contraindicated in patients with Wolff-Parkinson-White syndrome and should not be initiated in this patient. 1

Rationale for Contraindication

• Beta-blockers can worsen outcomes in WPW syndrome by potentially accelerating conduction through the accessory pathway during atrial fibrillation, which can precipitate ventricular fibrillation 1
• The American College of Cardiology/American Heart Association/European Society of Cardiology guidelines explicitly state that intravenous administration of beta-blocking agents is contraindicated in patients with WPW who have pre-excited ventricular activation in atrial fibrillation (Class III recommendation, Level of Evidence: B) 1
• This contraindication extends to oral beta-blockers as well, as the same physiological concerns apply regardless of route of administration 2

Mechanism of Harm

• In WPW syndrome, an accessory pathway (Kent bundle) allows electrical impulses to bypass the AV node 3
• Beta-blockers slow conduction through the AV node but do not affect the accessory pathway 1
• During episodes of atrial fibrillation, beta-blockers can:
  • Slow conduction through the normal AV nodal pathway 1
  • Allow preferential conduction through the accessory pathway 1, 2
  • Lead to rapid ventricular rates and potentially fatal ventricular arrhythmias 1

Other Medications to Avoid in WPW

• Non-dihydropyridine calcium channel antagonists (verapamil, diltiazem) are also contraindicated for the same reason 1, 4
• Digoxin is contraindicated in patients with WPW due to its positive inotropic effects and ability to enhance conduction through the accessory pathway 1, 4

Appropriate Management Options

• Catheter ablation of the accessory pathway is the recommended first-line treatment for symptomatic patients with WPW syndrome 1, 2
• For acute management of pre-excited atrial fibrillation:
  • Immediate electrical cardioversion is recommended for hemodynamic instability 1, 2
  • Intravenous procainamide or ibutilide can be used in hemodynamically stable patients 1, 2
• For antihypertensive therapy in patients with WPW:
  • Dihydropyridine calcium channel blockers (e.g., amlodipine) are a safer option 4
  • ACE inhibitors or ARBs are also appropriate alternatives 4
  • Thiazide diuretics can be considered as well 4

Risk Assessment

• The risk of sudden cardiac death in WPW is estimated at 0.15-0.2% annually in general WPW patients, but higher (2.2%) in symptomatic patients 2
• Risk factors for sudden cardiac death include:
  • History of symptomatic tachycardia 2
  • Short RR intervals (<250 ms) between pre-excited beats during atrial fibrillation 2
  • Multiple accessory pathways 2
  • Posteroseptally located pathways 2

Conclusion

Starting metoprolol in a patient with Wolff-Parkinson-White syndrome poses a significant risk and is contraindicated according to established guidelines. Alternative antihypertensive medications should be selected, and definitive treatment with catheter ablation should be considered.