From the Guidelines
True Right Bundle Branch Block (RBBB) on ECG is a significant finding that requires further investigation to determine the underlying cause, especially if newly diagnosed or accompanied by symptoms, as it may indicate underlying heart disease such as coronary artery disease, cardiomyopathy, or pulmonary conditions like pulmonary embolism. The key diagnostic features of RBBB include an rSR' pattern (rabbit ear appearance) in lead V1, with a wide R' wave, and wide S waves in leads I and V6, as well as secondary repolarization changes 1. RBBB occurs when electrical conduction through the right bundle branch is delayed or blocked, forcing the electrical impulse to travel through the left bundle branch first and then spread to the right ventricle in a slower, abnormal pattern.
Some key points to consider in patients with RBBB include:
- The presence of RBBB on ECG increases the risk of left ventricular systolic dysfunction, although the yield is lower than in patients with Left Bundle Branch Block (LBBB) 1
- Electrocardiography is the primary method of diagnosing potential conduction disorders, and ambulatory electrocardiographic monitoring can be used to document clinically significant arrhythmias in asymptomatic patients 1
- An echocardiogram may be useful in patients with suspected structural heart disease, as it can uncover treatable disease or impact management decisions such as cardiac resynchronization device placement 1
- Patients with RBBB may have similar outcomes to patients with LBBB, and new or presumably new RBBB is not an uncommon presentation of transmural acute myocardial infarction (AMI), occurring in approximately 5% to 10% of AMI patients 1
In patients with RBBB, it is essential to investigate the underlying cause, especially if newly diagnosed or accompanied by symptoms, and to monitor for any progression or development of additional conduction abnormalities. Regular cardiac follow-up is recommended, and further testing such as echocardiography or ambulatory electrocardiographic monitoring may be necessary to determine the underlying cause and to guide management decisions 1.
From the Research
True RBB on ECG
- The right bundle branch block (RBBB) is a condition where the right bundle branch of the heart's electrical conduction system is blocked, causing the heart's ventricles to contract abnormally 2.
- RBBB can be caused by various factors, including catheter-induced trauma during right heart catheterization, and can result in different electrocardiographic patterns 3.
- The presence of RBBB on an electrocardiogram (ECG) can be a predictor of sudden cardiac arrest due to pulmonary embolism, particularly when accompanied by a QR pattern in lead V1 4.
- Idiopathic RBBB, which is often considered harmless, may actually be linked to negative health outcomes, including impaired myocardial shortening and reduced longitudinal strain in both the left and right ventricles 5.
ECG Patterns and RBBB
- RBBB can manifest as different ECG patterns, including a QR pattern in lead V1, which has a high positive predictive value for diagnosing cardiac arrest caused by high-risk pulmonary embolism 4.
- The morphological diversity in RBBB patterns is likely related to multiple factors, including the site of block, nature of defect, degree of conduction delay, and associated pathologies 3.
- Distinguishing RBBB from a normal ECG variant, such as rsr', is important, particularly when associated with left hemiblocks, as it may warrant extensive cardiac evaluation 3.
Clinical Implications
- The presence of RBBB on an ECG can have significant clinical implications, including the risk of sudden cardiac arrest due to pulmonary embolism, and may require advanced treatments, such as systemic thrombolysis or invasive embolectomy 4.
- Idiopathic RBBB may be associated with impaired myocardial function, including reduced longitudinal strain and synchronization of both the left and right ventricles, which can have negative health outcomes 5.
- Avoidance of catheter-induced RBBB is advised in certain situations, such as in the presence of baseline complete left bundle branch block, or when approaching arrhythmic substrates linked to the right His-Purkinje system 2.