Prediction of left atrial pressure from the second sound-opening snap interval

There is a high correlation between the height of the V wave of the pulmonary capillary wedge tracing and the second aortic sound-opening snap interval, which allows a prediction of the former with reasonable accuracy. The accuracy of this prediction appears unaffected by the type of mitral valve lesion or by the presence of atrial fibrillation. The prediction becomes inaccurate in the presence of aortic insufficiency or in other situations which may change the relation between the brachial systolic pressure and the aortic pressure at the time of aortic valve closure. From these data a prediction graph has been derived which will allow more accurate prediction of the height of the V wave from the phonocardiogram.