Isolated bundle branch block and left ventricular dysfunction.
BACKGROUND
Population studies have identified the presence of bundle branch block (BBB) as a risk factor for increased mortality in patients with known cardiac disease. It is unknown how chronic ventricular dyssynchrony resulting solely from conduction delay affects ventricular function.


RESULTS
Subjects were retrospectively identified from the University of California, San Francisco, electrocardiogram database with QRS prolongation. Subjects who had no evidence of heart disease and had baseline and serial studies evaluating ongoing risk of coronary artery disease status and left ventricular function were followed over time. Documentation of a minimum of 2 serial evaluations of cardiac status were present in a total of 51/176 (20%) subjects with isolated BBB who constitute the study population. After a mean follow-up of 52 +/- 45 months-adjusting for differences due to age, sex, the presence of hypertension, hyperlipidemia, and diabetes mellitus-left ventricular ejection fraction diminished by -7.3 +/- 12% per year in the isolated left BBB cohort versus -1.9 +/- 4% in isolated right BBB cohort and -1.1 +/- 3% reduction in the isolated nonspecific intraventricular conduction delay cohort (P =.019).


CONCLUSIONS
Left bundle branch block itself may be a cause of ventricular dysfunction.
University of California, San Francisco, USA.
Seung-Joon
SJ
Lee
Charles
C
McCulloch
Iqwal
I
Mangat
Elyse
E
Foster
Teresa
T
De Marco
Leslie A
LA
Saxon
D000368:Aged; D002037:Bundle-Branch Block / Q000150:complications* / Q000453:epidemiology; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D015995:Prevalence; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors; D018487:Ventricular Dysfunction, Left / Q000150:complications* / Q000453:epidemiology