What are the implications of a new incomplete Right Bundle Branch Block (RBBB)?

From the Guidelines

A new incomplete right bundle branch block (RBBB) is associated with a worse short-term prognosis in acute pulmonary embolism (PE) and typically does not require specific treatment on its own, but rather evaluation for underlying cardiac conditions and regular cardiac follow-up. This condition occurs when there is partial delay in electrical conduction through the right bundle branch of the heart's conduction system. For most patients, especially those who are asymptomatic, no intervention is necessary beyond regular cardiac follow-up 1. However, it's essential to evaluate for any underlying cardiac conditions that might have caused the conduction delay, such as coronary artery disease, cardiomyopathy, or valvular heart disease. A comprehensive cardiac workup may include an echocardiogram to assess heart structure and function, stress testing if coronary artery disease is suspected, and possibly ambulatory ECG monitoring if symptoms like palpitations or dizziness are present. The significance of incomplete RBBB lies in its potential to progress to complete RBBB or to indicate underlying cardiac pathology, as noted in the 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1.

Some key points to consider in the management of incomplete RBBB include:

• Evaluation for underlying cardiac conditions, such as coronary artery disease, cardiomyopathy, or valvular heart disease
• Regular cardiac follow-up to monitor for progression or development of symptoms
• Consideration of a comprehensive cardiac workup, including echocardiogram, stress testing, and ambulatory ECG monitoring as needed
• Recognition of the potential for incomplete RBBB to progress to complete RBBB or indicate underlying cardiac pathology, as defined in the 2018 ACC/AHA/HRS guideline 1.

In the context of acute pulmonary embolism, the presence of a new incomplete RBBB has been shown to correlate with worse short-term prognosis, as noted in the American Heart Association scientific statement on the management of massive and submassive pulmonary embolism, iliofemoral deep vein thrombosis, and chronic thromboembolic pulmonary hypertension 1. Therefore, close monitoring and evaluation for underlying cardiac conditions are crucial in patients with a new incomplete RBBB, particularly in the setting of acute PE.

From the Research

Implications of a New Incomplete Right Bundle Branch Block (RBBB)

• A new incomplete RBBB can have both benign and pathological implications, and its presence on an electrocardiogram (ECG) requires careful evaluation 2.
• Incomplete RBBB is a common ECG finding, more frequent in men and athletes, and usually does not require further evaluation unless abnormalities are found on clinical examination 2.
• The presence of a new incomplete RBBB can be associated with various conditions, including atrial septal defect (ASD), and combining it with a defective T wave can increase the specificity and positive predictive values for diagnosing ASD 3.
• A new RBBB without other acute ECG changes can be a significant finding, and its presence may warrant urgent coronary angiography and cardiac catheterization, especially in patients with acute onset chest pain and positive biomarkers of myocardial necrosis 4.
• The early signs of right bundle branch block include a diminution of the S wave amplitude in lead V2, followed by slurring or notching of the upstroke of the S wave, and eventually the development of a r' deflection 5.
• In some cases, a new incomplete RBBB can occur during atrial fibrillation, and its presence can be associated with complex interactions between the RR cycle length and mechanisms affecting intraventricular conduction 6.

Diagnostic Considerations

• Clinicians should be familiar with the ECG findings of incomplete RBBB and be able to differentiate it from pathological patterns such as type-2 Brugada ECG pattern, right ventricular enlargement, and arrhythmogenic right ventricular cardiomyopathy 2.
• The presence of a new incomplete RBBB should prompt a thorough clinical evaluation, including a physical examination and laboratory tests, to exclude underlying heart disease 2.
• The combination of incomplete RBBB with other ECG findings, such as a defective T wave, can provide valuable diagnostic information and help guide further evaluation and management 3.

Clinical Significance

• A new incomplete RBBB can have significant clinical implications, including an increased risk of cardiac complications and the need for urgent coronary angiography and cardiac catheterization in certain cases 4.
• The presence of a new incomplete RBBB should be carefully evaluated in the context of the patient's clinical presentation and medical history, and its implications should be considered when developing a treatment plan 2, 3, 4.