Incomplete right bundle branch block: a novel electrocardiographic marker for lone atrial fibrillation.

AIMS: P-wave morphology and PR interval have both been previously associated with atrial fibrillation (AF). We hypothesized that incomplete right bundle branch block (IRBBB) would be associated with early-onset lone AF. METHODS AND RESULTS: We conducted a case-control study comparing electrocardiographic (ECG) markers from patients with early-onset lone AF and from a healthy control population. We included 187 patients with early-onset lone AF and 383 healthy controls. Sixty-two lone AF patients were excluded from the study because of AF at the time of enrolment or because of the use of antiarrhythmic drugs. For the remaining 125 patients with paroxysmal or persistent lone AF (84% males, mean age 37), controls were matched on a 1:1 basis on the parameters gender and age. A significantly higher proportion of the lone AF population had an IRBBB compared with the subjects in the control group (33.6 vs. 10.4%; P<0.001). In multivariable analysis adjusted for conventional risk factors, IRBBB was strongly associated with lone AF [odds ratio (OR) 5.43; 95% confidence interval (CI) 2.30-13.02; P<0.001]. Lone AF patients had a significantly longer PR interval than the control group (175.1 vs. 160.9 ms; P<0.001), but in multivariable analysis, every 10 ms increase in the PR interval was only borderline significantly associated with an OR of 1.15 (95% CI 0.99-1.32; P=0.060) for lone AF. CONCLUSION: We are the first to report that IRBBB is strongly and independently associated with early-onset lone AF.