Relationship between interatrial pressure gradient and motion of the interatrial septum

To evaluate interatrial septal motion throughout the cardiac cycle, echocardiograms of the septum were obtained by esophageal echocardiography simultaneously with left and right atrial pressures using Millar's micromanometers in nine subjects with sinus rhythm. There were four patients with atypical chest pain but with normal coronary arteries, two with old myocardial infarction, one with angina pectoris, one with aortic regurgitation and one with sick sinus syndrome. The relationship between interatrial pressure gradient (IAPG: left atrial pressure minus right atrial pressure) and the motion of the septum was examined. In all nine patients, the curves of IAPG showed two peaks near the second heart sound and during the atrial contraction period, and the motion of the septum throughout the cardiac cycle showed a similar pattern except during the late diastolic period. During atrial contraction the septum moved posteriorly (decrease in left atrial dimension) against the IAPG. Therefore, except during the atrial contraction period, the motion of the atrial septum is considered to be dependent on this pressure gradient. During the atrial contraction period, the direction of the septal movement might be dependent on the force of active contraction of the left atrial muscles.