Clinical assessment
Bifascicular block by itself is usually asymptomatic and is an incidental finding on ECG.
In some patients, bifascicular block can progress to complete or intermittent heart block, as conduction through the single remaining fascicle fails. This can manifest as presyncope or syncope, dyspnoea or weakness on exertion.
The rate of progression of bifascicular block to complete heart block is approximately 1% per year in asymptomatic patients, and as high as 17% per year in symptomatic individuals. The risk is higher if the bifascicular block is associated with 1st degree AV block.