Does a patient with second-degree type II atrioventricular (AV) block require evaluation for myocardial ischemia?

Yes, ischemic evaluation is warranted in patients with second-degree type II AV block

Patients with second-degree type II (Mobitz II) AV block should undergo evaluation for structural heart disease, including assessment for myocardial ischemia, as part of their comprehensive workup. While type II AV block is typically degenerative and located in the His-Purkinje system, ischemia represents a potentially reversible cause that must be excluded before proceeding to permanent pacing.

Why Ischemic Evaluation Matters

Type II second-degree AV block is always abnormal and typically indicates infra-nodal disease 1, 2. However, myocardial ischemia can cause reversible AV block, particularly when:

• Critical stenoses affect the left anterior descending artery (especially proximal lesions before the first septal branch, which perfuses the conduction system) 3
• Right coronary artery involvement occurs (which supplies the AV node in most patients) 4, 5, 6
• Coronary vasospasm is present 6

Recent case evidence demonstrates that revascularization can completely resolve AV block in selected patients, avoiding unnecessary permanent pacemaker implantation 3, 7.

Recommended Evaluation Algorithm

All patients with type II second-degree AV block should receive:

1. History and physical examination - specifically assessing for:

   • Anginal symptoms (though may be absent) 8
   • Syncope or presyncope 9
   • Risk factors for coronary disease
   • Timing of block onset (acute vs. chronic)

2. Echocardiogram - to detect structural heart disease and regional wall motion abnormalities 2

3. Exercise stress test - particularly valuable because:

   • Distal AV block appearing during exercise (when not due to ischemia) indicates His-Purkinje damage with poor prognosis 1
   • Can provoke ischemia-related conduction abnormalities
   • Helps distinguish ischemic from degenerative causes 2

4. Consider coronary evaluation if:

   • Structural heart disease is present
   • Ischemic symptoms exist
   • Risk factors are significant
   • Block appeared acutely
   • Regional wall motion abnormalities are detected

Critical Context: Post-MI Setting

In the acute myocardial infarction setting, the approach differs significantly 10:

• Persistent advanced second-degree or complete heart block with bilateral bundle branch block after MI requires permanent pacing (Class I indication) 10
• The prognosis relates more to extent of myocardial injury than the block itself 10
• Transient AV block without intraventricular conduction defects does NOT require permanent pacing 10

Important Caveats

Do not delay pacemaker implantation if the patient is symptomatic or has high-risk features, as type II AV block commonly progresses to complete heart block 1. The ischemic evaluation should be expedited but not postpone necessary pacing.

Distinguish true Mobitz II from mimics 11:

• 2:1 AV block cannot be classified as type I or II without additional rhythm strips
• Atypical Wenckebach can masquerade as type II block
• Concealed His bundle extrasystoles may create pseudo-AV block

Bottom Line

Permanent pacing is recommended for acquired second-degree Mobitz type II AV block regardless of symptoms 12, 13. However, before implantation, evaluate for reversible causes including ischemia through echocardiography and stress testing at minimum 2. If critical coronary lesions are identified, revascularization may restore conduction and avoid permanent pacing in select cases 3, 7. This is particularly relevant when the block appears acutely or in patients with significant coronary risk factors.