Myocardial Mural Thickness During the Cardiac Cycle

Abstract

The instantaneous and continuous thickness of the left ventricular wall was measured in ten dogs with a specially designed transducer. The thickness change during the "isovolumic" phase of systole was 11%. The average thickness increased an additional 10% during the ejection period of systole. These average values increased to 20% and 15% respectively with the administration of norepinephrine (approximately 0.001 mg/kg per minute). Transverse and longitudinal epicardial are strains were compared with thickness strain of the myocardium. Assuming the myocardium is incompressible, reasonable agreement was found in the three strains, which lends support to the measurements that were made. It is concluded that changes in the thickness of the myocardial wall during the cardiac cycle may be important in some considerations of the heart's performance.