Purpose: Acute exacerbations of chronic obstructive pulmonary disease (COPD) sometimes appear to occur without a precipitating cause. Heterogeneous repolarization and arrhythmias occur in COPD patients. Given the close inter-relation between heart and lung, we hypothesized that unrecognized arrhythmias might be precipitants of acute exacerbations. Methods: Electrocardiograms (ECG) of thirty patients during acute exacerbations were compared with ECG during stable phase. P wave dispersion was used to assess atrial depolarization heterogeneity, and dispersion of QT interval to assess ventricular repolarization. p < 0.05 was considered significant. Frequent exacerbations were defined as two or more exacerbations in a year. Results: Mean age of patients was 70.3 ± 11.8 SD years. P wave dispersion was greater during acute exacerbation than during stable phase (56.7 ± 19.2 vs 47.7 ± 15.9 ms, p = 0.009). There was a trend toward greater QTc dispersion (108.3 ± 61.7 vs 90.3 ± 47.0 ms, p = 0.13) in acute exacerbation compared to stable phase. Sixteen (53%) had frequent exacerbations. There was a significant difference in PR interval during stable phase between those with frequent exacerbations and those without (163.9 + 17.4 vs. 145.1 + 22.8; p = 0.02). The P wave dispersion during stable phase was greater in those with frequent exacerbations, but did not reach statistical significance (52.6 + 18.8 vs. 42.2 + 9.8 ms; p = 0.06). Conclusions: P wave dispersion is more in the acute phase than in stable phase, and is greater in patients with more frequent exacerbations. This does not prove, but suggests an intriguing possibility that P wave dispersion predates acute exacerbations. This might be a new target for prediction, prevention and therapy of acute exacerbations of COPD. © 2012 Elsevier Ltd. All rights reserved.