Bury My Heart at Wounded Knee

ANSWER

The correct diagnosis includes normal sinus rhythm with a left-axis deviation, right bundle branch block, and left anterior fascicular block, consistent with bifascicular block.

Left-axis deviation is evidenced by an axis beyond –30°. A right bundle branch block is marked by a QRS duration > 120 ms, an RSR’ pattern in lead V₁ and often V₂ and V₃, and wide S waves in lateral leads V₅ and V₆.

A left anterior fascicular block is identified by a left-axis deviation beyond –45°, a QR complex in lead I, and an RS complex in leads II and III.

The combination of a right bundle and left anterior fascicular block constitute bifascicular block. In this case, only the left fascicle conducts normally, putting this patient at risk for trifascicular block (ie, third-degree or complete heart block).