Echocardiographic definition of the left ventricular centroid. II. Determination of the optimal centroid during systole in normal and infarcted hearts

Although two-dimensional echocardiography is widely used in both clinical and experimental evaluations of regional cardiac wall motion, there is no established clinical method for quantitative analysis of the wall motion, not even for the normal radial motion observed in short-axis images. Measurement of radial wall motion requires determination of a centroid from which the radii emanate. Depending on its definition, the centroid is variously affected throughout systole by cardiac translation, regional wall motion and any shift of the subject position or transducer. A floating centroid is defined relative to the ventricular walls frame by frame, whereas a fixed centroid never moves with respect to the transducer. Evaluation of the best approach to definition of a centroid was previously presented (part I, this issue). The next question is how to use the centroid.This study examines which of four centroid applications provides the best reference for quantifying regional wall motion during systole. Method 1 is a floating centroid (defined separately for every image frame), method 2 uses the end-diastolic centroid as a fixed reference for all image frames, method 3 uses the end-systolic centroid as a fixed reference and method 4 uses the average as a fixed refer- ence. Wall motion was measured with respect to each of these centroids by determining radial wall motion from end-diastole to end-systole and correlating radial motion throughout the cardiac cycle with that in normal control hearts. Results were analyzed with respect to interobserver variance, symmetry of contraction in normal hearts (closeness of agreement of excursions for 36 equiangular radiais in the short-axis view) and correlation of abnormal contraction with microsphere distribution and infarct staining.For the normal canine heart with restricted translation, there was no significant difference in motion symmetry attributable to any method of centroid application. For the infarcted dog heart with limited translation, wall motion analysis best corresponded with microsphere distribution when a fixed reference for wall motion analysis was used (p < 0.005). The technique that best corresponded to microsphere distribution and histologic staining incorporated information throughout the cardiac cycle rather than merely analyzing end points (that is, systole versus diastole)