Background. Hemodynamic instability during heart displacement in off- pump multivessel coronary artery bypass grafting might be related to right heart dysfunction. The Enabler (HemoDynamics Systems Ltd, Upper Yoqneam, Israel)is a cannula pump that expels blood from the right atrium into the pulmonary artery. We studied the hemodynamic changes and the role of the enabler during heart displacement. Methods. Nine anesthetized sheep were assessed for hemodynamic changes during 90-degree heart displacement with or without Enabler support. Hemodynamic parameters included cardiac output, systemic arterial blood pressures, and left and right heart filling pressures. Results. Heart displacement caused a significant decrease in cardiac output and systemic blood pressure (46% ± 5%, p = 0.001; and 20% ± 5%, p = 0.009, respectively), with a concomitant 137% ± 24% (p = 0.003) increase in central venous pressure. No significant change in left atrial pressure was observed. Activation of the Enabler caused a significant increase in cardiac output and systemic blood pressure (67% ± 15%, p = 0.01; and 17% ± 7%, p = 0.04, respectively), as well as a decrease in central venous pressure by 49% ± 8% (p = 0.0001). Conclusions. Heart displacement causes hemodynamic instability mainly by right heart dysfunction. The Enabler significantly stabilized circulation during vertical displacement of the beating heart. (C) 2000 by The Society of Thoracic Surgeons.