A patient with an extensive anteroseptal myocardial infarction develops a new right bundle branch block. Occlusion of which vessel best explains involvement of the interventricular conduction tissue?

• A Posterior descending artery
• B Acute marginal branch of the right coronary artery
• C Septal perforating branches of the anterior interventricular artery ✓
• D Left marginal branch of the circumflex artery

Explanation

The anterior two-thirds of the interventricular septum, including much of the conduction pathway supplying the right bundle branch, is supplied by septal perforating branches arising from the anterior interventricular (LAD) artery. Occlusion of these branches in an anteroseptal infarct produces right bundle branch block. The posterior descending artery supplies only the posterior third of the septum and the AV node territory.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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