Electrocardiographic abnormality associated with increased risk of atrial fibrillation, congestive heart failure

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Left anterior fascicular block may be a clinically relevant marker of an individual’s propensity to develop atrial fibrillation or congestive heart failure, a new study published online on 17 April 2013 in the Journal of the American Medical Association (JAMA) has found.

“Left anterior fascicular block is considered a benign electrocardiographic finding, but its long-term consequences have not been comprehensively studied,” wrote Mala C Mandyam, University of California, San Francisco and colleagues.


Mandyam and colleagues investigated the long-term outcomes of participants with left anterior fascicular block in the absence of manifest cardiovascular disease in the Cardiovascular Health Study (CHS).


Established in 1989, CHS is a prospective cohort study of individuals 65 years of age or older sampled from Medicare eligibility lists nationwide in the USA. Of the 1,664 participants who met the criteria for this analysis, the 39 individuals (2.3%) with baseline left anterior fascicular block were older and more likely male.


At follow-up (median 16 years), 380 participants had developed atrial fibrillation; 328, congestive heart failure; and 954 had died. Sixteen participants (41%) with left anterior fascicular block developed atrial fibrillation; 17 (44%), congestive heart failure; and 33 (85%) died. After adjusting for various factors, left anterior fascicular block remained significantly associated with atrial fibrillation, congestive heart failure, and death.


“Given previous histopathological studies, these findings suggest that left anterior fascicular block may be a clinically relevant marker of an individual’s propensity to left heart fibrosis. Further research is needed to determine if left anterior fascicular block is an important predictor of consequent adverse outcomes,” the authors concluded.