Management of Mobitz Type II AV Block
Mobitz Type II second-degree AV block requires permanent pacemaker implantation due to high risk of progression to complete heart block and sudden cardiac death, regardless of symptoms.
Immediate Assessment and Risk Stratification
The critical distinction between Mobitz Type I (Wenckebach) and Mobitz Type II is essential, as they have fundamentally different prognoses and management approaches. While the provided evidence includes a case of Mobitz Type I during dengue recovery that resolved spontaneously 1, Mobitz Type II represents infranodal conduction disease with unpredictable progression to complete heart block.
Key Distinguishing Features to Confirm:
- Mobitz Type II: Constant PR interval with sudden dropped QRS complexes, typically with wide QRS (≥120ms) indicating infranodal block
- Mobitz Type I: Progressive PR prolongation before dropped beat, typically narrow QRS indicating AV nodal block 1
Definitive Management Algorithm
Step 1: Immediate Stabilization
- Assess hemodynamic stability and symptoms (syncope, presyncope, heart failure, chest pain)
- If symptomatic or hemodynamically unstable: initiate temporary pacing immediately (transcutaneous or transvenous)
- Continuous cardiac monitoring until definitive therapy
Step 2: Exclude Reversible Causes
- Review medications (beta-blockers, calcium channel blockers, digoxin, antiarrhythmics)
- Check electrolytes, particularly potassium and magnesium 1
- Assess for acute myocardial infarction (especially inferior MI)
- Consider Lyme disease in endemic areas
- Evaluate for infiltrative diseases if clinically indicated
Step 3: Permanent Pacemaker Implantation
This is the definitive treatment for Mobitz Type II, even in asymptomatic patients, because:
- High risk of progression to complete heart block (unpredictable timing)
- Risk of sudden cardiac death
- Infranodal location means unreliable escape rhythm if complete block develops
The pacemaker should be:
- Dual-chamber (DDD) system preferred to maintain AV synchrony
- Single-chamber ventricular (VVI) acceptable if atrial dysfunction present
- Rate-responsive features considered based on patient activity level
Critical Pitfalls to Avoid
Do not observe or delay pacing in Mobitz Type II - Unlike Mobitz Type I, which may be benign and reversible (as demonstrated in the dengue case where autonomic tone played a role 1), Mobitz Type II requires intervention regardless of symptoms.
Do not confuse with Mobitz Type I - The dengue hemorrhagic fever cases showed Mobitz Type I that resolved with exercise testing and normalized autonomic tone 1. This benign, reversible pattern does NOT apply to Mobitz Type II.
Do not rely on exercise testing - While exercise normalized conduction in Mobitz Type I 1, this response is not expected in Mobitz Type II and should not delay definitive therapy.
Do not attribute to transient causes without clear evidence - The functional AV node impairment seen during dengue recovery 1 represents a completely different pathophysiology than the structural infranodal disease of Mobitz Type II.
Post-Pacemaker Management
- Pacemaker interrogation at 2-4 weeks, then every 3-6 months
- Monitor for appropriate sensing and capture
- Assess battery life and lead integrity
- Adjust settings based on patient symptoms and pacing burden
- Continue management of underlying cardiac conditions
Special Considerations
If Mobitz Type II occurs in the setting of acute MI, temporary pacing is indicated immediately, with permanent pacemaker decision based on whether block persists beyond the acute phase (typically 2-3 weeks for anterior MI, may resolve with inferior MI if due to ischemia rather than structural damage).