The Architecture of the Heart in Systole and Diastole

Techniques for rapid fixation of the canine left ventricle in systole or diastole that have permitted analysis of ventricular geometry under known hemodynamic conditions are described. Six ventricles were arrested at and diastole, 7 at end ejection, and 7 in diastole following acute ventricular overdistension. The architecture of the ventricles was analyzed from measurements of the fixed ventricles and silicone-rubber casts of the ventricular cavities. In ventricles of matched weights, the average reduction, from end diastole to end ejection, of the apex to mitral valve distance was 4.6%, while that from apex to aortic valve was less than 1%. The minor internal equator was reduced by 26%, the midwall radius by 16%, and the outer radius by 8.5%. The ratio of the average end-diastolic volume minus end-systolic volume to the end-diastolic volume (analogous to stroke volume/end-diastolic volume) averaged 59%. The average wall thickness was 28% greater in systolic than in diastolic ventricles. The papillary muscle volume averaged 5.0%e of ventricular volume at end diastole and 14.7% at end systole. The area of the mitral valve orifice averaged 28% less at end systole than at end diastole; this area was 39% more in the hearts subjected to over-transfusion than in those with normal filling pressures. These data provide a framework for construction of a geometric model suitable for use in analyses of the mechanics of left ventricular contraction. Moreover, the methods described offer the possibility of correlating ventricular geometry and ultrastructure with cardiac function in normal and in abnormal hearts.