Relationship between P wave form and left atrial pressure and volume in mitral valve disease.

The P wave of the ECG, recorded with both conventional and special techniques, was compared with left atrial (LA) pressure and volume in 22 patients with mitral valve disease. The patients were also compared with 2 groups of normal subjects as to the P wave, recorded with the special technique. Changes in the P wave, such as increased duration, increased bipeak interval or P terminal force were significantly more common in the patients than in normal subjects. Among the patients, no significant correlations were found between degree of LA pressure elevation, LA enlargement and P wave changes. It is concluded that for the diagnosis of increased LA load it is more useful to study the terminal vector of the P wave than signs of increased atrial asynchrony. Recordings with high amplification and paper speed as in the present special technique are of advantage for such measurements. However, the special leads by themselves were not ideal for study of an increased terminal vector directed to the left and backwards.