Relationship of Fibrillatory Waves and P Waves in the Electrocardiogram

The amplitude of the fibrillatory waves and the P terminal force were compared in 100 consecutive patients. These electrocardiographic measures of atrial activity were made first in atrial fibrillation and then after electrical conversion to sinus rhythm. When the same patient was studied, the occurrence of a coarse fibrillatory wave and an abnormal P terminal force, or a fine fibrillatory wave and a normal P terminal force, was found to be a highly significant relationship. This relationship suggests that the factors responsible for the characteristic of the terminal portion of the P wave recorded in sinus rhythm probably determine the magnitude of the fibrillatory wave that occurs when atrial fibrillation is present. The finding of a coarse fibrillatory wave or an abnormal P terminal force should suggest the electrocardiographic diagnosis of left atrial hypertrophy or "strain."