Conversions in off-pump coronary surgery

There have been 784 coronary artery bypass grafting (CABG) procedures performed at a new center for treating cardiovascular disease in Tuzla, Bosnia and Herzegovina, and the surgical team has been fully trained in offpump coronary artery bypass (OPCAB) surgery. All surgical patients were considered for on-pump CABG (ONCAB) and OPCAB surgical procedures. Minimally invasive direct coronary artery bypass grafting and robotic procedures were done as OPCAB. For multivessel median sternotomy cases, the selection criteria were arbitrary (approximately 50% were performed as ONCAB for perfusionist training). Patients who were scheduled for and began their operations as OPCAB but who were then placed on cardiopulmonary bypass during the surgical procedure were counted as conversions. The outcomes of converted patients were studied and are the subject of this report.

Of the 784 CABG procedures, 391 (49.6%) were scheduled and performed as ONCAB operations; 357 (45.5%) were performed as OPCAB; and 36 (9.2% of the originally scheduled OPCAB patients or 4.6% of the total number of CABG surgeries) were originally scheduled as OPCAB operations but were converted to ONCAB. Reasons for conversions were hemodynamic instability (21 patients), difficult revision of grafts (8), ventricular fibrillation (5), and poor native vessel (2). Outcomes of patients undergoing conversions were analyzed with respect to the conversion cause. When the cause of the conversion was mild-to-moderate hemodynamic instability or difficult graft revision (n = 27), no adverse ischemic effects were seen; however, when the cause of conversion was severe hemodynamic instability, ventricular fibrillation, or cardiac arrest (n = 9), 6 patients (66.6%) had severe ischemic complications involving the central nervous system or the myocardium.

Myocardial ischemia must be monitored and treated aggressively in OPCAB surgery. In patients with mild hemodynamic instability, conversion did not adversely affect outcome. In patients with severe hemodynamic compromise and cardiac arrest, serious complications of cerebral and myocardial ischemia were observed. The appropriate timing of conversion is essential.