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Patient
83-year-old man, with severe mitral regurgitation awaiting surgery; three syncopes in two days at home with facial trauma and fracture of the malar bone;
Trace
On arrival at the emergency room, normal PR interval (180 ms), complete right bundle branch block pattern (QRS duration 120 ms, rSR' pattern in V1) with left anterior fascicular block (left axis, q wave in lead I and wide S wave in lead II);
Trace
The patient is admitted with telemetry monitoring; new syncope episode with evidence on the tracing of a prolonged asystole with numerous blocked P waves; rare ventricular escape rhythms;
Trace
A dual-chamber pacemaker is implanted; the electrocardiogram shows a rhythm predominantly detected in the atrium (a single paced atrial cycle) and paced in the ventricle (low right ventricular septal pacing lead explaining QRS negativity in lead I and in inferior leads); DDD pacing mode (synchronization of the ventricles on the paced or sensed atria);
Exergue
A left axis deviation in a patient with right bundle branch block points to the presence of an associated left anterior fascicular block.
This patient initially presented a bifascicular block. The left axis deviation adding to a typical pattern of right bundle branch block should evoke the associated diagnosis of left anterior fascicular block.