Left atrial involvement in acute pulmonary edema

The incidence of the ECG finding of left atrial involvement was evaluated during the acute episode and on days 4 and 7 in 50 patients admitted with acute pulmonary edema. During the acute episode of pulmonary edema 38 (76 per cent) of the patients had left atrial involvement on the initial ECG. On day 4 only 16 (38.1 per cent) of 42 patients who were available for follow-up ECG's still had left atrial involvement (p < 0.001). By day 7 the incidence of left atrial involvement had decreased further to nine (25.7 per cent) positives in 35 patients. There was a high incidence of left atrial involvement on the ECG during acute pulmonary edema, but with resolution of the pulmonary edema left atrial involvement frequently disappeared. This suggests that the posterior rotation of the terminal P wave vector producing left atrial involvement is dependent more on increased left atrial pressure and volume than on increased left atrial mass.