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

Objectives: 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.

Methods: 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.

Results: 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.

Conclusions: 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.