What is the recommended management for a patient with second-degree atrioventricular block Mobitz type I (Wenckebach)?

Management of Second-Degree Mobitz Type I (Wenckebach) AV Block

Mobitz Type I (Wenckebach) generally requires no specific treatment or continuous monitoring in most patients, as it has a benign prognosis and rarely progresses to complete heart block. 1, 2

Key Diagnostic Features

• Wenckebach is characterized by progressive lengthening of the PR interval before a dropped QRS complex, followed by a reset to a shorter PR interval. 2
• The QRS complex is typically narrow because the block occurs at the AV node level. 2
• The P-wave to QRS ratio exceeds 1:1 (e.g., 3:2 or 4:3 patterns), reflecting that some atrial beats are conducted. 2

Clinical Significance and Prognosis

• Wenckebach has a benign prognosis and does not influence survival; progression to complete heart block is rare. 1, 2
• This rhythm is commonly observed in healthy athletes, during sleep, or with heightened vagal tone. 1, 2
• The block typically occurs at the AV node level and is associated with a faster, more reliable escape mechanism compared to infranodal blocks. 2

Monitoring Recommendations

• In-hospital continuous cardiac monitoring is generally not required for asymptomatic Wenckebach. 1, 2
• Monitoring may be considered on an individual basis if the arrhythmia is frequent or occurs during exertion, but this is not routinely necessary. 2
• Asymptomatic patients with Wenckebach awaiting evaluation do not require telemetry. 1

When to Consider Intervention

• Permanent pacemaker implantation is rarely required for Wenckebach unless the patient is symptomatic during exercise. 2
• Evaluate for reversible causes including:
  • Increased vagal tone (most common in healthy individuals) 2
  • Medications: beta-blockers, non-dihydropyridine calcium channel blockers, or digoxin 2
  • Inferior wall myocardial infarction 2
  • Electrolyte abnormalities 2

Response to Pharmacologic Interventions

• Atropine improves AV nodal-level blocks including Wenckebach, but is typically unnecessary unless the patient is symptomatic with bradycardia. 2
• If atropine is needed for symptomatic bradycardia, administer 0.5 mg IV every 3-5 minutes to a maximum total dose of 3 mg. 3

Critical Pitfalls to Avoid

• Do not confuse Wenckebach with Mobitz Type II block—the latter requires immediate pacemaker evaluation regardless of symptoms. 2, 4
• A 2:1 AV block cannot be classified as Wenckebach or Mobitz II without observing consecutive beats to assess PR interval behavior. 2
• Do not misinterpret atrial bigeminy with blocked premature atrial contractions as true AV block. 2
• Rarely, Wenckebach can occur at the infranodal (His-Purkinje) level rather than the AV node; this variant has a worse prognosis and may require pacing. 5 An electrophysiology study can identify the level of block if clinical suspicion is high.

Special Populations

• In athletes and young healthy individuals, Wenckebach is a physiologic adaptation and requires no intervention. 2
• In patients with inferior MI, Wenckebach typically resolves spontaneously and does not require permanent pacing. 2
• In patients on negative chronotropic medications, consider dose reduction or discontinuation if clinically appropriate. 2