Prospective evaluation of atrial tachyarrhythmias in patients with interatrial block

Introduction Interatrial block (P-wave ≥ 110 ms) is clinically associated with left atrial enlargement and electromechanical dysfunction as well as atrial tachyarrhythmias. We prospectively evaluated the incidence of such arrhythmias, especially atrial fibrillation among patients with interatrial block over the course of 1 year. Methods 118 patients (aged 48 to 104 years; female 56.6%) who had been hospitalized between December 15, 2004 and January 14, 2005 were identified and divided into 3 groups based on their respective baseline electrocardiogram (interatrial block = 41 patients, sinus non-interatrial block = 51 patients and atrial tachyarrhythmia = 24 patients). Patients were subsequently followed for 12 months for pertinent cardiovascular events (heart failure, peripheral embolism, transient ischemic attacks and stroke), atrial tachyarrhythmias (atrial fibrillation and atrial flutter) and death as endpoints. Results 19 patients (17.9%) had atrial fibrillation during the 12-month follow-up (sinus non-interatrial block group = 4 [9.1%], interatrial block group = 12 [29.3%] and atrial tachyarrhythmia group = 3 [14.3%]). Coronary artery disease, hypertension, pre-existing atrial fibrillation history, dilated cardiomyopathy, atrioventricular valvular disease and interatrial block (age- and sex-adjusted hazard ratio = 4.2; 95% confidence interval 1.2–14.4; p = 0.02) were significantly associated with future events of atrial fibrillation. However, logistic regression analysis indicated that interatrial block was not an independent predictor of future atrial fibrillation whereas only history of pre-existing atrial tachyarrhythmias was (hazard ratio = 23.6; 95% confidence interval 4.5–121.7; p = 0.0002). Conclusion Interatrial block may be associated with atrial fibrillation but in a 12-month period, does not appear to be an independent predictor of future atrial fibrillation. Continued prospective investigation of such a relationship is certainly warranted given its already known consequences.