Regional variation in the timing and extent of left ventricular wall motion in normal subjects

Right anterior oblique cineangiograms from 19 subjects without evidence of heart disease were analysed to assess regional non-uniformity in the time of onset of systolic inward motion, amplitude of systolic motion, time of peak inward motion, and wall motion during the isovolumic relaxation period. The left ventricular silhouette was digitised frame by frame for a full cardiac cycle. These four wall motion variables were quantitatively measured along 40 chords drawn from equally spaced points on the end diastolic silhouette to the nearest point on the end systolic silhouette. Onset of systolic inward motion was significantly non-uniform, being delayed by up to 120 ms in the anterior apical chords compared with the areas of earliest inward motion near the base of the heart. More uniformity was noted in time of peak inward motion; the differences between regions were not statistically significant. Amplitude of systolic motion was significantly less at the apical and mid-anterior segments than elsewhere in the heart. Wall motion during the isovolumic relaxation period is outward and greatest in the mid-anterior segments, but inward in the proximal inferior segments and mitral valve region. These data suggest that contraction of muscle fibres in the anterior apical segments is initially isometric due to the considerable afterload at the onset of contraction, this afterload being the result of earlier contraction elsewhere in the ventricle. This may partly explain the propensity for aneurysms to be located in the anterior apical region. When the timing and extent of wall motion in disease states are analysed, account must be taken of the non-uniformity in the normal heart.