Does the use of a free internal mammary artery graft on the left anterior descending artery compromise long-term survival?†

Abstract

The aim of the study was to determine if there is a long-term outcomes disadvantage associated with using the internal mammary artery (IMA) as a free graft to the left anterior descending artery (LAD) during coronary artery bypass graft surgery. Between 1991 and 2014, 21 876 consecutive patients underwent isolated primary coronary artery bypass graft surgery at our institution. Among these, 238 underwent a free IMA (f-IMA) graft to bypass the LAD. Propensity score matching with bootstrap analysis was performed to produce a cohort of 222 f-IMA patients matched to 222 patients with in situ IMA grafting to the LAD. Early and long-term outcomes including survival, readmission for cardiovascular causes and repeat revascularization up to a maximum of 23 years post-coronary artery bypass graft surgery were compared. Provincial vital statistics and administrative hospital readmission data were used to analyse long-term outcomes. Operative mortality [3.2% f-IMA vs 1.9% in situ IMA; odds ratio = 1.79, 95% confidence interval (CI) = 0.91-3.52] and the majority of postoperative adverse events were not significantly different among matched patients. The risk of late death was not significantly different between the 2 matched groups (hazard ratio = 1.14, 95% CI = 0.92-1.41, P = 0.15). The risk of hospital readmission for cardiovascular reasons was significantly higher in the f-IMA group (54.5% vs 47.3%, odds ratio = 1.4; 95% CI = 1.10-1.72), although repeat revascularization (18.4% vs 13.5%; odds ratio = 1.53, 95% CI = 0.96-2.44) was not significantly different between the matched groups. Late survival and the need for repeat coronary revascularization were not influenced by using the IMA as a free graft to the LAD. However, there is a small but significant increase in the risk of hospital readmission for cardiac reasons.