Right Bundle Branch BlockEdit
Right bundle branch block (RBBB) is a common electrocardiographic finding that reflects a delay in the conduction of electrical impulses through the right bundle branch of the heart’s conduction system. It is not a disease in itself, but rather a pattern that can occur in healthy individuals as well as in people with structural heart disease. On a standard electrocardiogram (ECG), RBBB is identified by a QRS complex that is widened (usually 120 ms or more) and a characteristic pattern in the right precordial leads, reflecting delayed right ventricular activation. It is important to distinguish this pattern from other intraventricular conduction abnormalities, particularly left bundle branch block, which has different implications for diagnosis and management. electrocardiography cardiac conduction system
RBBB can be encountered incidentally during routine testing or during evaluation for chest pain, dyspnea, syncope, or palpitations. In many people, especially older adults, it coexists with conditions such as hypertension, coronary artery disease, cardiomyopathy, or prior myocardial infarction, but it can also occur without evident heart disease. Because it may indicate an underlying pathology, clinicians often assess for associated conditions through history, physical examination, imaging, and laboratory testing. The pattern may be more clinically meaningful when accompanied by symptoms or signs of structural heart disease. ischemic heart disease myocardial infarction
Pathophysiology
The heart’s conduction system coordinates the timing of ventricular contraction. The right bundle branch relays impulses to the right ventricle. When the right bundle branch is blocked, right ventricular activation is delayed relative to the left ventricle, producing a widened QRS complex and a distinctive ECG morphology. The classic ECG features of RBBB include an rSR' pattern in the right chest leads (V1–V2) and a wide, often terminal S wave in the lateral leads (I, aVL, V5–V6). These electrical findings reflect intact left-sided conduction with delayed right-sided activation. The overall effect on cardiac output is typically small in isolated cases but can be more pronounced when RBBB coexists with other conduction abnormalities or with significant structural heart disease. electrocardiography conduction system
Etiology and epidemiology
RBBB arises from a spectrum of causes, ranging from benign to clinically significant: - Idiopathic or age-related degeneration of the conduction system. - Ischemic heart disease or prior myocardial infarction. - Hypertension, cardiomyopathy, or other forms of structural heart disease. - Congenital conduction system abnormalities. - Acute conditions such as myocarditis or pulmonary embolism in some settings. Patients without structural heart disease may have isolated RBBB, while others have concomitant conditions that influence prognosis and management. The pattern is more prevalent in older adults and can be detected in the general population or alongside cardiovascular risk factors. ischemic heart disease cardiomyopathy congenital heart disease
Clinical features
Most individuals with isolated RBBB are asymptomatic and aware of the finding only because an ECG was performed for another reason. When RBBB is present with underlying heart disease, symptoms may reflect that disease (for example, chest pain with ischemia, dyspnea from heart failure, or syncope related to more extensive conduction abnormalities). The presence of RBBB can complicate the interpretation of other cardiac conditions, particularly in the setting of acute chest pain or suspected myocardial infarction, where it can mask or mimic ischemic changes on ECG. myocardial infarction heart failure
Diagnosis
Diagnosis rests on ECG findings and is supplemented by imaging and laboratory testing as indicated: - ECG: QRS duration of 120 ms or longer, with an rsR' pattern in V1–V2 and a broad terminal S wave in I, aVL, and V6. Incomplete RBBB has a QRS duration between about 110–120 ms. These features help distinguish RBBB from other intraventricular blocks. electrocardiography - History and examination to assess for underlying heart disease. - Echocardiography or cardiac imaging to evaluate structure and function if clinically indicated. In some cases, stress testing or advanced imaging may be used to evaluate for ischemia or cardiomyopathy. echocardiography cardiac imaging - Laboratory testing as guided by symptoms (e.g., troponin in the workup of chest pain). myocardial infarction
Management
Management is largely determined by the clinical context: - Isolated, asymptomatic RBBB without evidence of structural heart disease typically requires no specific therapy beyond routine cardiovascular risk assessment and monitoring. pacemaker is not routinely indicated in these cases. cardiac conduction system - If RBBB coexists with significant underlying disease (e.g., coronary artery disease, heart failure, or cardiomyopathy), treatment targets that disease. This can include pharmacologic therapy for heart failure or ischemia, lifestyle changes, and risk-factor modification. coronary artery disease heart failure - In patients with progressive conduction disease or syncope where complete heart block is a concern, a permanent pacemaker may be indicated to maintain adequate heart rhythm and rate. The decision rests on the overall conduction status and clinical presentation rather than the RBBB pattern alone. pacemaker atrioventricular block - In the acute setting of chest pain or suspected myocardial infarction, RBBB should prompt appropriate evaluation and adherence to current guidelines for ischemia assessment, recognizing that RBBB can complicate ECG interpretation. Some guidelines discuss carefully integrating ECG, biomarker data, and imaging to avoid missed diagnoses. myocardial infarction
Prognosis
Prognosis depends largely on the presence and severity of coexisting heart disease rather than the RBBB pattern itself. Isolated RBBB in a structurally normal heart generally carries a favorable prognosis, whereas RBBB in the setting of heart failure, prior myocardial infarction, or dilated cardiomyopathy is associated with higher risk and may reflect a greater burden of cardiovascular disease. Ongoing monitoring for progression of conduction disease may be indicated in selected patients. heart failure myocardial infarction
Controversies and debates
Within clinical practice, several debates surround RBBB, particularly in how aggressively to pursue diagnostic workups in various contexts: - Isolated RBBB and screening: Some clinicians favor a conservative approach for asymptomatic individuals without signs of cardiac disease, while others advocate targeted assessment for occult cardiomyopathy in older patients or those with risk factors. The balance is between avoiding unnecessary testing and missing a clinically important condition. echocardiography ischemic heart disease - Ischemia interpretation with RBBB: RBBB can obscure or alter representative ST-T changes on the ECG, complicating the diagnosis of acute coronary syndromes. Debates exist about the need for additional criteria or imaging when RBBB is present in chest pain scenarios, and how to integrate biomarkers and risk scores. myocardial infarction - Conduction disease progression and pacing: Whether patients with RBBB should receive pacing depends on the evolution of the conduction system disease and the presence of symptoms such as syncope or documented high-grade block. Some argue for earlier pacing in certain conduction disorders, while others emphasize a watchful waiting approach to avoid unnecessary device therapy. pacemaker atrioventricular block - Distinguishing benign patterns from pathology in aging populations: In older adults, distinguishing benign RBBB from early signs of progressive cardiomyopathy or multilead ischemia can be challenging, leading to differing practice patterns regarding referral for advanced imaging or stress testing. cardiomyopathy