Abstract 12557: Prevalence and Long Term Prognosis of Patients with Complete Bundle Branch Block with Normal Left Ventricular Ejection Fraction Referred for Stress Echocardiogram

Abstract

Background: Left bundle branch block (LBBB) is an independent predictor of mortality in patients with coronary artery disease (CAD) and heart failure. Whether patients with LBBB and a normal left ventricular ejection fraction (EF) and normal stress echo (SE) are at high risk has not been previously studied.

Methods: We studied 4281 patients with normal EF (>55%) who were referred for stress echocardiogram from 1997 - 2008. Complete bundle branch block (BBB) was determined on resting ECG. Patients were divided into presence of any Right bundle branch block (RBBB) and LBBB. Patients were followed for mean of 8 ± 3.4 yrs for all-cause mortality assessed using the SSDI.

Results: There were 187 (4.4%) patients with BBB. There were 31 patients (0.7%) patients with LBBB and 156 (3.6%) patients with RBBB. Patients with BBB were older males and likely to undergo dobutamine stress but otherwise CAD risk factors were comparable. As compared to patients without BBB, LBBB was associated with ischemia/scar but RBBB was not, 22% vs. 48% vs. 24% respectively; p=0.002. There were 766 (18%) deaths. After adjusting for age, gender, CAD risk factors, BMI, stress mode, history of MI/PCI/CHF, using patients without BBB and a normal SE as reference,, patients with BBB and normal stress echo had no increased risk for death (HR =1.1,95% CI 0.73 - 1.76; 0.6). However, among patients with abnormal stress echo, those with any BBB (HR=2.04, 95% CI 1.3 - 3.2; p=0.002) had a greater risk for all-cause mortality compared to those without BBB (HR=1.6, 95% CI 1.3 - 1.9; p<0.001). Furthermore, patients with LBBB had the highest mortality compared to RBBB and no BBB. 7.8%/yr vs. 3%/yr vs. 2.8%/yr; p<0.0001.

Conclusions: In patients with normal EF referred for SE, complete BBB and a normal SE has a benign prognosis similar to those without a BBB. However, BBB with abnormal SE does portend worse outcomes. The worst prognosis in LBBB patients with an abnormal SE.