The Relationship of Increased Left Atrial Volume and Pressure to Abnormal P Waves on the Electrocardiogram

Left atrial volume and pressure measurements in 23 normal subjects and 117 cardiac patients were compared with several electrocardiographic criteria for left atrial disease. Both P duration in lead II and V 1 terminal force (the area inscribed by the terminal portion of the P in lead V 1 ) showed a highly significant correlation with changes in left atrial volume but related less well to increases in left atrial pressure. Diagnostically, both criteria accurately predicted normal or increased left atrial size in two thirds of all patients. The V 1 terminal force was more accurate in predicting left atrial pressure abnormalities in all subjects and particularly reliable in detecting increased pressure and volume in mitral stenosis. The P/PR segment ratio was less helpful in the detection of left atrial disease.