From the Guidelines
Exercise-induced Right Bundle Branch Block (RBBB) is not typically associated with an increased risk of death and cardiac events, unlike exercise-induced Left Bundle Branch Block (LBBB) 1. When considering the effects of stress on cardiac conduction, it's essential to differentiate between various types of bundle branch blocks. According to the 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay 1, exercise-induced LBBB has been linked to a higher risk of adverse cardiac events, but there is no such association reported for exercise-induced RBBB.
Key points to consider:
- Exercise stress testing can be used to evaluate cardiac function under physical exertion, and it may reveal intermittent RBBB that is not visible at rest 1.
- The standard Bruce protocol is commonly used for exercise stress testing, with the goal of achieving 85% of the age-predicted maximum heart rate 1.
- Pharmacological stress testing using dobutamine or adenosine can be an alternative for patients who cannot exercise adequately.
- The primary concern during stress testing is to monitor for significant symptoms like chest pain, severe shortness of breath, or concerning arrhythmias, and to terminate the test if necessary.
In clinical practice, the absence of a reported association between exercise-induced RBBB and increased cardiac risk 1 suggests that RBBB can be induced by stress without necessarily implying a worse prognosis. However, it is crucial to interpret the results of stress testing in the context of the individual patient's overall clinical presentation and medical history.
From the Research
Right Bundle Branch Block (RBBB) and Stress
- RBBB is a condition where there is a blockage in the right bundle branch of the heart's electrical conduction system 2.
- Studies have shown that RBBB can be associated with increased risk of cardiovascular morbidity and mortality 2, 3.
- Exercise stress tests have been used to evaluate the risk of RBBB in patients without prior diagnosis of cardiovascular disease 2, 4, 5.
Exercise-Induced RBBB
- Exercise-induced RBBB is a rare occurrence during routine clinical exercise testing 5.
- One study found that exercise-induced RBBB was associated with a higher annual death rate compared to those with normal ST response or abnormal ST depression 5.
- However, another study found that exercise-induced RBBB was benign and not associated with increased risk of mortality 5.
RBBB and Cardiovascular Disease
- RBBB has been shown to be a marker of early cardiovascular disease 2.
- Patients with RBBB have been found to have a higher prevalence of hypertension, decreased functional aerobic capacity, and slower heart rate recovery on exercise testing 2.
- RBBB has also been associated with increased risk of cardiovascular-related mortality 2, 3.
Predictors of Mortality in RBBB
- Ischemia at stress echocardiography, left anterior fascicular block, age >65 years, and wall motion score index at rest have been identified as multivariate predictors of mortality in patients with RBBB 3.
- The presence of RBBB has been shown to be an important predictor of late recurrence of atrial fibrillation and/or atrial tachycardia after pulmonary vein isolation 6.