P-wave Indices: Derivation of Reference Values from the Framingham Heart Study

Background: P-wave indices, an electrocardiographic phenotype reflecting atrial electrophysiology and morphology, may be altered in multiple disease states or by cardiovascular risk factors. Reference values for P-wave indices, providing cut points for their classification and interpretation, have not yet been established and are essential toward facilitating clinical application and comparison between studies.

Methods: We randomly selected 20 men and 20 women from 10-year age intervals between <25 years to 76-85 years from the Framingham Heart Study Original and Offspring Cohorts, excluding subjects with prevalent cardiovascular disease, hypertension, diabetes or obesity. The total included 295 subjects; eligibility in women >75 years was limited by exclusion criteria. We used a digital measurement technique with demonstrated intrarater reproducibility to determine P-wave indices. P-wave indices examined included the maximum, mean, lead II and PR durations, dispersion, and the standard deviation of duration.

Results: All P-wave indices were significantly (P < 0.0001) correlated with advancing age. Means of all P-wave indices were lower in women as compared to men. PR-interval duration was strongly correlated with maximum, mean, and lead II mean P-wave durations. In multivariable models adjusting for significant anthropometric and clinical associations risk factors, significant differences persisted by age and sex in P-wave indices.

Conclusions: In our healthy sample without cardiovascular disease, hypertension, diabetes, or obesity, men and older subjects had longer mean P-wave indices. Our description of P-wave indices establishes reference values for future comparative studies and facilitates the classification of P-wave indices.