Quantitation and significance of horizontal cardiac motion in M mode and two dimensional echocardiography

Abstract

Cardiac structures are continuously moving during the cardiac cycle so that constantly changing acoustical interfaces are being recorded by the theoretically static echographic beam. The characteristic movement of the base of the heart toward the apex in systole appears as horizontal motion when imaged in two dimensional echocardiographic parasternal long axis views. The quantitative characteristics of horizontal motion were studied in 50 control patients, 25 patients with decreased cardiac output, 20 with volume overload and 10 with pericardial effusion. The angle of cardiac shift at the aorto-interventricular septal junction was 8 ± 2 ° (mean ± standard deviation) in control patients, and this change constituted 21 ± 6 percent of the area within the arc containing the standard M mode information. Horizontal shifts were decreased in patients with decreased cardiac output (4 ± 2 °; p < 0.001) and increased in patients with volume overload (11 ± 4 °; p < 0.001) or pericardial effusion (10 ± 3 °; p < 0.025). With use of the concept of horizontal motion, the interventricular septal hinge point was noted to be in the area of the membranous interventricular septum, rather than at the junction of the upper and middle thirds of the interventricular septum in 80 percent of normal subjects, 72 percent of patients with decreased cardiac output, 60 percent of those with pericardial effusion, 52 percent of those with left-sided volume overload and 40 percent of those with right-sided volume overload. The concept of horizontal cardiac motion was also pertinent to the interpretation of aortic valve opening, the transposition of aortic root information to apparent left ventricular outflow tract level, one form of pseudosystolic anterior mitral motion, abnormal left atrial echoes, echoes mimicking flail posterior mitral leaflet and interpretation of left atrial wall motion at the left atrial-left ventricular junction. In conclusion, horizontal cardiac motion is a significant physiologic phenomenon of potential clinical importance. It causes important changes in the echographic recording of acoustical information.