Risk and predictors of dyssynchrony cardiomyopathy in left bundle branch block with preserved left ventricular ejection fraction

Abstract

Background: Left bundle branch block (LBBB) and left ventricular (LV) dyssynchrony likely contribute to progressive systolic dysfunction. The evaluation of newly recognized LBBB includes screening for structural heart abnormalities and coronary artery disease (CAD). In patients whose LV ejection fraction (EF) is preserved during initial testing, the incidence of subsequent cardiomyopathy is not firmly established.

Hypothesis: The risk of developing LV systolic dysfunction among LBBB patients with preserved LVEF is high enough to warrant serial imaging.

Methods: We screened records of 1000 consecutive patients with LBBB from our ECG database and identified subjects with an initially preserved LVEF (≥45%) without clinically relevant CAD or other cause for cardiomyopathy. Baseline imaging, clinical data, and follow-up imaging were recorded to determine the risk of subsequent LV systolic dysfunction (LVEF ≤40%).

Results: (Data are mean + SD) 784 subjects were excluded, the majority for CAD or depressed LVEF upon initial imaging. Of the remaining 216, 37 (17%) developed a decline in LVEF(≤40%) over a mean follow-up of 55 ± 31 months; 94% of these patients had a baseline LVEF≤60% and LV end systolic diameter (ESD) ≥ 2.9 cm indicating that these measures may be useful to define which patients warrant longitudinal follow-up. The negative predictive value of a LVEF>60% and LVESD <2.9 cm was 98%.

Conclusions: Seventeen percent of patients with LBBB and initial preserved LVEF develop dyssynchrony cardiomyopathy. We believe the risk of developing dyssynchrony cardiomyopathy is high enough to warrant serial assessment of LV systolic function in this high-risk population.

Keywords: cardiomyopathy; dyssynchrony; heart failure; left bundle branch block.

FIGURE 1

Study population‐reasons for exclusion. Flow chart depicting the subjects screened for this analysis with excluded patients and reason for exclusion shown on the right. 24 patients were excluded (not shown) because the LBBB was found to be intermittent (n = 22) or the ECG did not meet criteria for LBBB (n = 2)

FIGURE 2

Scatter plots of baseline left ventricular end systolic diameter (ESD) and left ventricular ejection fraction (LVEF). Although there is great overlap between the groups, the vast majority (94%) of patients who developed a cardiomyopathy (decline in LVEF, Group 2) demonstrated an initial LVESD of ≥2.9 cm whereas slightly more than half of the preserved LVEF group had an initial LVESD ≥2.9 cm. No patients who developed a cardiomyopathy had an initial LVEF above 60%. In patients with an LVESD of ≥2.9 cm and an LVEF ≤60%, the relative risk of developing a cardiomyopathy was 18.4. The negative predictive value for an LVESD <2.9 cm and LVEF >60% was 98%

FIGURE 3

Time course for the development of dyssynchrony cardiomyopathy. Kaplan‐Meier curve of the time course for the decline in LV systolic function among the cardiomyopathy group (Group 2). The dashed lines represent the 95% confidence intervals. The mean follow‐up period was 55 ± 31 months with the median time to develop a LVEF ≤40% being 48 months. All patients in Group 2 developed a cardiomyopathy within 125 months after the first identification of a LBBB