LBBB DDx

LBBB is usually seen in patients with structural heart disease (hypertrophy, dilatation, fibrosis, etc.)

• Also seen in those with ischemic heart disease, valvular disease, and various cardiomyopathies

May be caused by inflammatory changes, advanced hyperkalemia, digitalis toxicity, or primary diseases of the conduction system (Lenegre's or Lev's disease, where there is fibrosis or degeneration of the conduction system that results in heart block)

Patients may have a LBBB at baseline that may have no relevance to their presenting symptoms in acute settings

In patients presenting with symptoms of acute ischemia, new or old LBBB may make the detection of acute MI challenging

LBBB may have no adverse prognostic significance in those without evidence of structural heart disease, such as young patients with idiopathic LBBB