Devices used to expose the posterior coronary artery in OPCABG surgery may cause ischemia

Off-pump coronary artery bypass graft (OPCABG) surgery is commonly used to revascularize diseased hearts. In order to graft a posterior artery in this procedure, the heart must be lifted from the chest cavity using an apical suction device to expose the surgical field. In the process, this device may cause unwanted myocardial ischemia. We measured myocardial electrical impedance (MEI), a parameter that responses to myocardial ischemia, as well as ST-segment changes during OPCABG surgery in five patients undergoing revascularization of the left anterior descending (LAD) and posterior descending coronary artery (PDA). MEI increased with the application of the suction device in these patients, suggesting myocardial ischemia. ST-segment changes were negligible while the heart was raised from the chest cavity but increased immediately when the heart was returned to the normal position. Our data suggest that the apical suction device causes ischemia that is virtually undetected with ST-segment monitoring while the heart is raised and electrically disconnected from the body. MEI has the potential to detect intra-operative ischemia monitor.