INFLUENCE OF PRELOAD, AFTERLOAD, AND CONTRACTILITY ON MYOCARDIAL ULTRASONIC TISSUE CHARACTERIZATION WITH INTEGRATED BACKSCATTER

Influence of hemodynamic changes in preload, afterload and contractili ty on myocardial integrated backscatter (IB) was studied in 26 adult m ongrel dogs by measuring myocardial IB calibrated with the backscatter from the blood during volume infusion (preload alteration), during ao rtic constriction (afterload alteration), and during dobutamine or pro pranolol infusion (contractility alteration). Changes in preload, afte rload or contractility did not significantly affect the calibrated myo cardial IB either in the septum or in the posterior wall. Changes in p reload and afterload did not affect the magnitude of cyclic variation in IB. However, dobutamine produced a significant increase in the magn itude of cyclic variation in IB and propranolol significantly decrease d the magnitude of cyclic variation in IB. These data indicated that t he calibrated myocardial IB is independent of preload, afterload and c ontractility, and that the magnitude of cyclic variation in IB is infl uenced by contractility. We may estimate static (related to histologic al changes such as fibrosis, edema, necrosis, and so on) and dynamic ( related to myocardial contraction such as sarcomere length, muscle fib er orientation, and so on) properties of the myocardium more precisely using myocardial IB calibrated with the backscatter from the blood in addition to the magnitude of cyclic variation in IB.