Bilateral bifascicular blocks of the LAFB variant may progress to complete AV block (or third-degree AV block). This progression is typically slow and seen in only about 2–4% of these patients per year because the left posterior fascicle is resistant to any underlying disease. Treatment includes cardiac pacing.

Bilateral bifascicular blocks of the LPFB variant may progress faster to third-degree AV block. Patients with clinical symptoms such as dizziness or syncope are candidates for cardiac pacing. A 24-hour Holter monitor may help discover asymptomatic episodes of second- or third-degree AV block.