INTRACAVITARY ULTRASOUND IMPAIRS LEFT-VENTRICULAR PERFORMANCE - PRESUMED ROLE OF ENDOCARDIAL ENDOTHELIUM

Irradiation of isolated cardiac muscle by high-power, high-frequency, continuous wave ultrasound selectively damages endocardial endothelium (EE). We evaluated this ultrasound effect in vivo on the performance of the intact ejecting canine left ventricle (LV). A cylindrical ultrasound probe (0.9 MHz, 25 W), mounted on a catheter, was inserted in the LV cavity through an apical stab wound and was activated for 60, 120, and 240 s, followed each time by a recovery period of 10-15 min. Ultrasound transiently and repeatedly abbreviated the time interval from end diastole to peak (-)dP/dt (from 241 +/- 30 to 229 +/- 32 ms after 240 s; P < 0.001), accelerated LV pressure fall, did not alter peak (+)-dP/dt or peak systolic pressure, increased diastolic and systolic segment lengths, and decreased fractional shortening. Microscopic analysis revealed dispersed granulocytes attached to the EE. EE cells were visibly damaged only in a limited area surrounding the probe. Accordingly, high-power, high-frequency, continuous wave ultrasound reversibly modulated LV performance, presumably by transient alteration of EE function.