Urgent Pump Conversion: When Does It Occur and How Can We Prevent It?

Abstract

Off-pump coronary artery bypass grafting is widely performed to prevent cardiopulmonary bypass complications. However, on-pump conversion occurs unexpectedly and is associated with high morbidity and mortality. We have determined the preoperative risk factors that predict conversion based on a large number of off-pump cases that we experienced. Careful intraoperative displacement of the heart and snaring of the coronary arteries are essential to prevent the hemodynamic instability that results in the need for an urgent institution of cardiopulmonary bypass. Transesophageal echocardiography is very useful for proper heart positioning. With this imaging modality, we can observe pulmonary artery obstruction, right ventricular obstruction, mitral regurgitation, and other conditions that can cause hemodynamic instability. If there are ST-segment changes on the electrocardiogram, an intracoronary shunt should be used. The grafting sequence is also important. When there is hemodynamic collapse despite several preventive measures, the patient must be converted to on-pump coronary artery bypass grafting (CABG). The increase in morbidity and mortality with conversion can be reduced by converting rapidly from off-pump to on-pump CABG before encountering significant hemodynamic instability.