Differential Diagnosis for RBBB

The differential diagnosis for Right Bundle Branch Block (RBBB) can be organized into the following categories:

• Single most likely diagnosis
  • Idiopathic or age-related RBBB: This is the most common cause of RBBB, often seen in older adults without any underlying cardiac disease. It is usually asymptomatic and discovered incidentally on an electrocardiogram (ECG).
• Other Likely diagnoses
  • Cor pulmonale: RBBB can be associated with cor pulmonale, which is right ventricular enlargement and failure secondary to pulmonary disease. Conditions such as chronic obstructive pulmonary disease (COPD) and pulmonary embolism can lead to this.
  • Pulmonary embolism: While not all pulmonary embolisms cause RBBB, it is a significant enough association to warrant consideration, especially in the context of acute onset.
  • Cardiac sarcoidosis: This condition can cause RBBB among other conduction abnormalities due to granulomatous infiltration of the heart.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed)
  • Pulmonary embolism with hemodynamic instability: Although mentioned earlier, it's crucial to emphasize that any sign of hemodynamic instability (e.g., hypotension, syncope) in the context of RBBB should prompt an immediate consideration of pulmonary embolism.
  • Acute myocardial infarction: While RBBB itself is not a direct indicator of myocardial infarction, in the context of chest pain or other symptoms suggestive of acute coronary syndrome, it's critical to consider the possibility, especially if there are associated ST-segment changes.
• Rare diagnoses
  • Arrhythmogenic right ventricular cardiomyopathy (ARVC): A rare condition characterized by replacement of the right ventricular myocardium by fatty tissue, leading to arrhythmias and potentially RBBB.
  • Cardiac tumors: Rarely, cardiac tumors can infiltrate the conduction system, leading to RBBB.
  • Infiltrative diseases (e.g., amyloidosis): These can affect the heart and lead to conduction abnormalities, including RBBB.

Each of these diagnoses has a different set of implications for patient management and prognosis, highlighting the importance of a thorough evaluation in the context of RBBB.