Introduction: Coronary artery ectasia (CAE) is defined as localized or diffuse dilatation of the epicardial coronary arteries. We sought to determine whether isolated CAE may alter P-wave duration and dispersion (PD). Methods: The study population consisted of 26 patients (mean age: 61.6 +/- 11.0 years) with isolated CAE (group 1) and sex- and age-matched 26 control subjects (group 2). Both groups underwent a standard 12-lead surface electrocardiogram recorded at 50 mm/s. Maximal (P(max)) and minimal P-wave durations (P(min)) are measured. PD was defined as the difference between P(max) and P(min). Results: In group 1, P(max) (114.2 +/- 10.4 ms vs 104.8 +/- 10.6 ms, p < 0.002) and PD (34.0 +/- 12.7 ms vs 24 +/- 10.6, p < 0.004) were significantly higher than those of group 2. Moreover a significant correlation was found between P,,,, and PD with ectatic segment number (r=0.625, r=0.626. respectively; p=< 0.001); and P(max) and PD with ectatic vessel number (r=0.698, r=0.704 respectively; p=< 0.0001). Conclusion: Isolated CAE and the degree of the ectasia were found to be associated with prolonged P(max) and PD. (c) 2007 Elsevier Ireland Ltd. All rights reserved.