Myocardial Infarction Complicated by Heart Block

  • Acute coronary syndrome (ACS) involves rupture or erosion of a coronary plaque with exposure of the subendothelial matrix to circulating blood and subsequent platelet adhesion, platelet activation, and platelet aggregation
  • A thrombus forms, resulting in partial or complete occlusion of the lumen of the coronary artery
  • The initial ECG is nondiagnostic in up to 50% of patients presenting with chest pain, but remains a critical part of the evaluation
  • Complete heart block (CHB) may be associated with an anterior or inferior wall MI
  • High degree AV block is associated with an increase in mortality in patients with an inferior or anterior myocardial infarction
  • Complete heart block with inferior MI generally results from an intranodal lesion and isassociated with a narrow QRS complex and develops in a progressive fashion from 1st to 2nd to 3rd degree block
  • Patients with inferior MI and CHB may be resistant to atropine and its use during active ischemia may cause ventricular fibrillation!
  • Temporary transvenous pacing is recommended
  • Patients with inferior MI and CHB typically don’t need permanent pacing as the rhythm is transient and resolves within 5-7 days

Click on the link below to see an ECG of inferior MI with complete heart block!

ECG (courtesy of Life in the Fast Lane)