VERTICAL DISPLACEMENT OF THE BEATING HEART BY THE OCTOPUS TISSUE STABILIZER - INFLUENCE ON CORONARY FLOW

Background. In beating heart coronary artery bypass graft operations, biventricular pump failure, as observed after exposure of the posterio r circumflex branches by sternotomy, may originate from mechanical obs truction to coronary flow. Methods, Regional coronary blood Bow was me asured in 8 anesthetized, paced, beta-blocked pigs, and the beating he art was fully retracted. Results. Displacement decreased cardiac outpu t from 4.8 +/- 1.1 L/min (mean +/- standard deviation) to 2.8 +/- 1.2 L/min (p < 0.001), a 42% +/- 6% decrease that resulted in a decrease i n mean arterial pressure by 48% +/- 6% (mean +/- standard error of the mean; p < 0.001) and a reduction in coronary blood flow in the left a nterior descending coronary artery, the right coronary artery, and the circumflex coronary artery by 34% +/- 6%, 25% +/- 8%, and 50% +/- 10% , respectively (all p < 0.05 versus baseline). Relative circumflex cor onary artery now was 20.1% +/- 8.3% lower than the combined relative v alue of left anterior descending coronary artery and right coronary ar tery flows (p = 0.046). Subsequent 20 degrees head-down tilt significa ntly increased ventricular preload pressures and restored cardiac outp ut and mean arterial pressure as well as coronary blood flow. Conclusi ons. It is inferred that coronary blood flow was not mechanically obst ructed during anterior displacement of the porcine beating heart, beca use augmentation of preloads by the maneuver of Trendelenburg restored coronary flow parallel to the recovery of cardiac output and mean art erial pressure while the heart remained retracted by 90 degrees. (C) 1 998 by The Society of Thoracic Surgeons.