Is a New Right Bundle Branch Block a Sign of Coronary Artery Disease?
By Michael H. Crawford, MD, Editor
SYNOPSIS: For asymptomatic subjects without known cardiac or renal disease, coronary lesions by CT angiography are more frequent in those with right bundle branch block vs. those without.
SOURCE: Lee H, Jeon YJ, Kang BJ, et al. Frequency and significance of right bundle branch block and subclinical coronary atherosclerosis in asymptomatic individuals. Am J Cardiol 2021;158:30-36
Researchers have seen an association between right bundle branch block (RBBB) with all-cause and cardiovascular (CV) mortality in subjects without known heart disease.1 However, such studies did not exclude subjects with symptoms that could have been caused by heart disease.
Lee et al recruited 8,103 asymptomatic subjects (mean age 54 years, 65% men) who were self-referred for a general health exam to undergo an ECG and a cardiac CT angiogram (CTA), which included a coronary calcium score (CAC). After excluding subjects with a history of CV disease, other ECG abnormalities, atrial fibrillation, or chronic renal disease, 7,205 formed the final population of whom 116 showed RBBB. Baseline characteristics of the RBBB group indicated they were older, recorded higher systolic blood pressure readings, and were more likely to have been diagnosed with diabetes. Also, their mean CAC score was 98 vs. 41 in those without RBBB (P = 0.003). Any plaque by CTA was found in 47% of RBBB subjects and 35% of those without RBBB (P = 0.007). However, when adjusted for risk factors for coronary artery disease (CAD), RBBB was not associated with CAD by CTA, as demonstrated in a propensity score analysis matching RBBB patients 5:1 with 580 subjects without RBBB (HR, 0.87; 95% CI, 0.57-1.32). The authors concluded RBBB was not associated with an increased risk of subclinical CAD in asymptomatic subjects without a history of heart or renal disease vs. those without RBBB.
COMMENTARY
This is somewhat of a mixed message in that RBBB was associated with subclinical CAD in asymptomatic subjects without known CAD, but not when adjusted for risk factors for CAD. RBBB as an isolated finding is not of much significance unless the individual exhibits risk factors for CAD. This is consistent with prior studies showing that RB is a risk factor for morbidity and mortality in patients with known CAD but not those without CAD, where it is generally considered benign. Consequently, if a patient with known CAD or in whom the risk of subclinical CAD is high and develops new RBBB, it may be a cause for concern. It would be reasonable to evaluate the patient further, control risk factors better, or follow closer, depending on the clinical situation. On the other hand, a new isolated RBBB without symptoms, known disease, or significant risk factors may not require any further evaluation. This study does not address this issue directly, as there are no follow-up data.
The fact this work was conducted only at a single center in Korea is a weakness. There may be a referral bias since the patients were seeking a medical evaluation. Also, some patients showed left anterior fascicular block with RBBB, but there were too few subjects here with RBBB to analyze separately.
RBBB is rare in the general population, but becomes more common with older age. In older patients, RBBB may be just the result of an aging cardiac conduction system or a manifestation of cardiac disease. A thorough clinical evaluation should help clinicians sort this out in most patients and certainly seems appropriate, especially in older patients in whom this is a new finding. At a minimum, patients with RBBB should be told to seek medical help if they develop symptoms suggestive of complete heart block. In patients with known heart disease or at high risk for it, a new RBBB would suggest progression of the disease, which may require intensifying care or follow up depending on the situation.
The significance of RBBB must be assessed in the clinical context of the patient. It may be a benign finding or a risk factor for subsequent cardiac morbidity and mortality.
REFERENCE
- Gaba P, Pedrotty D, DeSimone CV, et al. Mortality in patients with right bundle-branch block in the absence of cardiovascular disease. J Am Heart Assoc 2020;9:e017430.
For asymptomatic subjects without known cardiac or renal disease, coronary lesions by CT angiography are more frequent in those with right bundle branch block vs. those without.
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