Intraventricular conduction delay natural history, complications and prognosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mugilan Poongkunran M.B.B.S [2]

Intraventricular conduction delay usually has no prognostic significance in patients without underlying heart disease but may progress to complete heart block or ventricular arrhythmia with worse prognosis in underlying heart disease.

• Right bundle branch block :
  • In patients without evidence of structural heart disease, RBBB has no prognostic significance.
  • When cardiac disease is present, the coexistence of RBBB suggests advanced disease.
  • RBBB is an independent predictor of all-cause mortality in patients with known or suspected coronary heart disease.
  • In the setting of an acute MI, RBBB is associated with a significant increase in mortality.

• Left bundle branch block :
  • The presence of isolated LBBB has no adverse prognostic significance.
  • In patients with LBBB associated with ischemic heart disease, hypertension, or cardiomyopathy, the prognosis depends on the severity of the underlying heart disease. The highest incidence of sudden cardiac death is among patients with LBBB and cardiac disease.
  • In patients with acute MI and heart failure, the presence of LBBB is associated with a worse prognosis.
  • Unfortunately, patients whose only manifestation of an acute MI is a left bundle branch block are less frequently treated with reperfusion therapy, and they have a worse prognosis.^[1]
  • Because the presence of LBBB can represent the clinical onset of LV structural disease, the finding of LBBB on resting ECG requires further evaluation with echocardiogram and Holter monitoring for assessment of LV function, as well as identifying both advanced degrees of AV block and heart disease-related tachyarrhythmias.

• Hemiblocks :
  • Isolated LAF block does not itself imply a risk factor for cardiac mortality or morbidity.
  • The prognosis of LAF block is primarily related to the underlying heart disease.
  • LAF block in the setting of acute MI is probably associated with increased mortality.

• Complications :
  • Pulmonary arterial line placement ^[2] in a patient with LBBB can result in a complete heart block if the right bundle branch is traumatized during the process.
  • Progression to higher degree AV block: It was shown in the Swedish study that the risk of progression was more pronounced in left block than in right bundle branch block.
  • Bradycardia
  • Ventricular arrythymias
  • Delay in the diagnosis of MI: Presence of LBBB or RBBB can delay the diagnosis of an acute MI.
  • Sudden cardiac death is a potential complication when associated with a heart attack.

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