Bifascicular heart block
See brief interpretation of 12 lead EKG above
– right bundle branch block, RBBB (rSR’ configuration in lead V1 and QRS ≥ 0.12 sec)
– left anterior fascicular block, LAFB (left axis deviation with absence of other cause and initial R’s in inferior leads; II, III, aVF)
Bifascicular heart block is the combination of right bundle branch block and block of either the left anterior fascicle or the left posterior fascicle (recall the electrical conduction system of the heart).
The fascicle involved will often be the left anterior fascicle as the left posterior fascicle receives dual blood supply and is more resistant to myocardial ischemia.
Asymptomatic bifascicular block requires no treatment. Pacemaker implantation may be relevant if the patient has seizures – however other arrhythmia such as (intermittent) AV blocks or ventricular tachycardia should also be considered as cause of seizures.