Ultrasonic Sensors For Measuring Regional Ventricular Function

Measurement of systolic wall thickening by sonomicrometry is an accurate index of regional left ventricular (LV) function, but the trauma of crystal inserion precludes its clinical use. We have developed a 4-mm 10 MHz ultrasonic probe which can either be sutured or applied via suction to the epicar-diuui and can measure wall thickening at anv depth of the LV wall. In 18 dogs, the suction probe correlated well (r=0.97) with previously validated sutured probe. To assess clinical feasibility, the probe was applied to the epicardium of 45 patients undergoing coronary bypass surgery. Good wall thickening tracings were obtained with no trauma. Transmural LV thickening fraction prior to bypass surgery was 32 ± 6 % (X ± SEM) at the midventricular lateral wall, 29 ± 5 % at the anterior basal wall and 25 ± 5 % at the midventricular posterior wall. Right ventricular thickening fraction averaged 25 ± 4 %. In general, wall thickening during immediate postoperative period remained unchanged compared to preoperative thickening fraction. Exteriorization of a wire attached to the sutured probe allows in situ monitoring of wall thickening for 48-72 h after surgery and subsequent removal. Thus, this probe is an accurate, atraumatic method for measuring right and LV regional function. Transmural, endocardial and epicardial function can be mapped at various sites during surgery and post-operatively one can follow serial changes of regional function and assess the effects of cardioplegia and other therapeutic interventions.