Time course of changes in P-wave duration during exercise.

The exercise-induced increase in P-wave duration reported previously has not been studied on a minute-by-minute basis. We measured the P duration in 47 normal subjects and 43 coronary artery disease (CAD) patients each minute during an exercise test. We found that prolongation of the P wave in those with CAD occurs relatively early and the difference between normal subjects and CAD patients is greater near maximum exercise. The data suggest that an increase in P-wave duration may reflect an increase in the left-ventricular end-diastolic pressure and may occur earlier that ST-segment depression.