Electrocardiographic detection of left atrial enlargement. Correlation of P wave with left atrial dimension by echocardiography.

The validity of various electrocardiographic P wave measurements was tested in 48 patients by comparing them to left atrial dimensions determined by echocardiography (echo), a proved method of left atrial size estimation. Of all the measurements considered, only the width of the P wave (PW), the P terminal force in lead V1 (PV1), and the PW/PR segment ratio (PW/PR) showed statistically significant correlations with left atrial size measurements by echo, with r values of 0-746, 0-491, and 0-479, respectively. The results indicated that P widths in excess of 105 ms were present in all the patients who had left atria equal to or greater than 3-8 cm by echo and in 11 per cent of patients without atrial enlargement (false positives), and that when measurements were less than 105 ms left atrial enlargement was unlikely.