Perioperative Assessment of Segmental Left Ventricular Function in Man: Effects of Nitroprusside After Bypass Operations

Direct on-line assessment of postoperative ventricular function has not been possible. We assessed the feasibility of using pulse-transit sonomicrometry to measure regional function in man postoperatively. Ultrasonic transducers (3 mm in diameter) were implanted along the minor axis of the left ventricle at midwall depth into a region supplied by a bypass graft. All wires were tunneled subcutaneously. Pressures, ECG, and regional dimensions were monitored in eight patients continuously, and at 48 to 72 hours postoperatively, the effects of sodium nitroprusside were assessed. The transducers were withdrawn with no complications. Nitroprusside was associated with an increase in systolic shortening from 1.60 ± 0.19 to 1.92 ± 0.25 mm and rate of shortening from 12.13 ± 1.85 to 15.34 ± 2.38 mm/s at constant end-diastolic lengths. Using this technique for recording regional dimensions, nitroprusside therapy augmented function at a constant preload.