EFFECT OF HEART-RATE, PRE- AND AFTERLOAD, AND MYOCARDIAL INOTROPIC STATUS ON AMPLITUDE OF INTEGRATED ULTRASOUND BACKSCATTER

The purpose of the study was to evaluate diagnostic significance of cy clic variation of integrated ultrasound backscatter from the myocardiu m. Effect of changes in heart rate, mean arterial pressure, pre- and a fterload, and myocardial inotropic state on sound backscatter was stud ied with transesophageal echocardiography in 34 patients during uncomp licated coronary artery bypass surgery. Left ventricular cross-section al images at the level of papillary muscles were monitored. Cyclic var iation of intefrated backscatter and percent systolic wall thickening were calculated for each segment. Cyclic variation of integrated backs catter and percent systolic wall thickening significantly decreased du ring myocardial ischemia (from 3,9+/-1,2 dB to 2,7+/-0,5 dB from 37+/- 7% to 18+/-5%, respectively) and during infusion of protamine sulfate (from 3,5+/-1,2 dB to 2,7+/-0,7 dB and from 31+/-15 to 23+/-9%, respec tively). There was no correlation between cyclic variation and such he modynamic indexes as heart rate, preload and afterload. Cyclic variati on of integrated backscatter correlated significantly with percent sys tolic wall thickening (r=0,43, p<0,05). Thus cyclic variation of integ rated backscatter of ultrasound from cardiac tissues is sensitive to c hanges of myocardial contractile state and does not depend on hemodyna mic parameters.