Severe aortic atherosclerosis is a risk factor for stroke during coronary artery bypass grafting (CABG). The purpose of this study was to evaluate the incidence of postoperative neurologic complications after off-pump CABG (OPCAB) with a proximal seal system (Heartstring).From January 2011 to December 2014, 729 patients underwent isolated OPCAB. The cohort was divided into two groups (Heartstring [HS] and aortic no-touch [NT]). The severity of aortic atherosclerosis (Katz grade) was evaluated by intraoperative epiaortic ultrasonography (EUS). The primary endpoints were postoperative neurologic complications (early stroke and minor events (delirium, transient ischemic attack, and syncope) ), and the secondary endpoints were late major adverse cardiac and cerebrovascular events (MACCEs) and death.The mean age of all patients was 65.1 +/- 9.5 years, and a severe Katz grade (IV or V) was demonstrated to be an independent risk factor of long-term mortality (HR 3.53: 95% CI 1.06-11.75: P = 0.04) and MACCEs (HR 2.41: 95% CI 1.19-4.92: P = 0.02), but no significant differences were found for early stroke (0.9% versus 1.7%: P = 0.53) and minor neurologic complications (14.6% versus 9.9%: P = 0.05) between the groups regardless of the Katz grade. The 5-year overall survival rate did not differ significantly between the groups (90.9% versus 87.6%: P = 0.61).Although a higher Katz grade was identified as an independent risk factor of death and MACCEs, the HS group was not inferior in terms of neurologic complications regardless of the Katz grade. Therefore, the Heartstring system might be safely and efficiently used with EUS to decrease the incidence of neurologic complications.