2-O Interval as an indicator of left atrial pressure

Abstract

The time interval between the aortic closure sound and O point or the apexcardiogram (2-O) interval) was determined in a group of 38 normotensive patients and correlated with the mean left atrial or pulmonary capillary wedge pressure. Twenty-three patients had an elevated left atrial pressure and an average 2-O interval of 0.076 seconds. Fifteen patients had a normal left atrial pressure with an average 2-O interval of 0.10 seconds. Both normal and abnormal left atrial pressures occurred at 2-O intervals of 0.08 seconds or more. A 2-O interval of 0.07 seconds or less was associated with a left atrial pressure of 18 mm Hg or more. On the basis of this study, it is concluded that the 2-O interval is a simple, accurate, non-invasive method of predicting an elevated left atrial pressure in normotensive patients with severe coronary artery or myocardial disease.