Abnormal P-waves morphology as a marker of atrial abnormality in a population-based cohort of patients with normal P-wave duration

Background Biphasic P-wave morphology in inferior leads and P-wave duration (PWD) ≥120 ms are the key features that define interatrial block (IAB) as partial or advanced depending on the polarity of the terminal atrial depolarization vector in the frontal plane. However, multi-component or fractionated P-waves preclude reliable morphology categorization though may reflect advanced atrial substrate. Furthermore, P-waves with normal PWD <120 ms are not defined as IAB even if they exhibit abnormal morphology. Purpose We hypothesized that abnormal P-wave morphology is a marker of atrial myopathy even if PWD is normal and studied the association of different P-waves morphology subtypes, including multi-component or fractionated (atypical) P-waves, with increased supraventricular ectopic activity as a marker of atrial myopathy. Methods We included 909 subjects with PWD <120 ms on resting electrocardiogram (ECG) from the population-based Swedish CArdioPulmonary bioImage Study (544 females, 60%, mean age 57 ±4 years). All participants underwent 24-hour Holter ECGs. Resting ECGs were digitally processed and analyzed using Glasgow algorithm which defines PWD as the time from the P-wave earliest onset to the latest end in any lead. P-wave morphology was defined automatically as positive, negative or biphasic. P-waves with non-positive morphology in inferior leads were reviewed manually by two trained cardiologists. The morphology of the P-waves in inferior leads was categorized as biphasic +/- or negative and as atypical if multicomponent/fractionated (Figure). Increased supraventricular ectopic activity was defined as ≥500 premature atrial complexes (PACs)/24 h. To assess the association of P-waves morphology subtypes with PACs>500/24hr, logistic regression analysis adjusted for age and gender was performed. Results Atypical P-waves were observed in 215 subjects (24%) and were associated with increased supraventricular ectopic activity in univariate logistic regression analysis and after adjustment for age and gender (ORadj 2.00, 95%CI 1.16-3.44, p=0.013). Biphasic +/- or negative P-waves were observed in 327 subjects (36%): in 22% only in lead III, in 13% in leads III and aVF and in 1% in leads III, aVF and II; and were not associated with increased supraventricular ectopic activity. Conclusion In the population-based sample of subjects with normal PWD, multimodal/fractionated P-wave morphology is common and is associated with increased supraventricular ectopic activity. Our findings suggest that P-wave morphology is a non-invasive marker of atrial myopathy, which should be considered in patients without IAB and assessed regardless of PWD.