We read with great interest the report of Magnani et al on P-wave duration and risk for longitudinal atrial fibrillation (AF) in patients aged ≥60 years from the Framingham Heart Study. Using a single-channel electrocardiographic (ECG) recording, the investigators found that maximum P-wave duration at the upper fifth percentile was associated with long-term AF risk in an elderly community-based cohort. Moreover, they found no significant associations between P-wave dispersion and the incidence of AF or mortality. Although the results are interesting, we believe that they should be considered cautiously because of the lack of simultaneous recording of all 12 ECG leads.

Simultaneous recording of ECG leads has been considered a prerequisite to calculate any “P-wave dispersion index” since the early report of Buxton and Josephson. They introduced the isoelectric interval, which was derived by subtracting the longest P-wave duration in the standard limb lead from the total P-wave duration, measured from the earliest onset to the latest end of the P wave in any of the simultaneously recorded leads I, II, and III. Our research group has introduced P-wave dispersion as a simple ECG predictor of paroxysmal lone AF. Although acceptable intraobserver and interobserver error in the measurement of P-wave duration on 12-lead electrocardiography have been reported, well-known difficulties in defining P-wave onset and offset may restrict the accuracy and reproducibility of the measurements. To overcome some of these restrictions, averaging techniques used in advanced recording devices and magnified graticules on standard computer screens have proved useful in the accurate evaluation of common P-wave descriptors. In any case, simultaneous recording of all 12 ECG leads is mandatory to reduce the time-related well-known lability of P-wave features. The lability of P-wave characteristics in normal subjects has been reported previously. Changes in P-wave amplitude during physical daily activities, such as positional changes, respiration, and exercise, have already been demonstrated. Finally, the circadian behavior of P-wave characteristics may also induce possible imprecision in measurements when a single-channel ECG recording is used. To achieve greater precision in measuring P-wave dispersion, we believe that simultaneous recording of all 12 ECG leads is mandatory to examine AF risk, particularly when a single ECG is recorded in each patient.