Discussion
This retrospective, single-center study of early and long-term results of CABG in dialysis-dependent end-stage renal disease patients showed satisfactory early mortality results with no increased operative or DSWI risk with BITA grafting. The long-term results were also better in the BITA group.
BITA grafting did not increase the overall operative mortality. Our safety-focused operative strategy and postoperative management likely led to successful early results. To ensure patient safety, we minimized operative invasiveness. In patients with impaired heart function, severe left main trunk disease, or preoperative hemodynamic instability, we inserted an IABP preoperatively. We did not hesitate to insert an IABP intraoperatively or switch to on-pump surgery when patients became hemodynamically unstable during the operation. Moreover, we focused on postoperative fluid management and avoided postoperative intravascular dehydration to reduce the risk of non-occlusive mesenteric ischemia (NOMI). Hypovolemic shock, cardiogenic shock, and administration of alpha-adrenergic drugs were the most significant postoperative risk factors for NOMI17,18. Patients’ body weight was gradually adjusted to reach their preoperative dry weight at around the end of the first postoperative week.
Previous studies reported that BITA grafting was a risk factor for DSWI19-21, however, we found no differences in the frequency of DSWI between the groups. Our patients’ ITAs were harvested by skilled surgeons using the skeletonization technique with a harmonic scalpel, which reduces the risk of DSWI22.
The long-term results showed superior MACE-free rates and less cardiac-related death in the BITA group. The BITA group showed a clear trend towards improved survival, although there was no significant difference. This might partly be because of a short follow-up period and small number of patients. Another cause might be the characteristics of dialysis patients, who are immunocompromised and exhibit accelerated atherosclerotic and arteriosclerotic changes23,24. Therefore, they are at a higher risk for non-cardiac comorbidities such as infection, stroke, and organ impairment. However, BITA grafting could have contributed to preventing cardiac-related events.
Currently, there is no consensus on the efficacy of BITA grafting in dialysis patients currently exists15. The limited number of studies on CABG in dialysis patients are mostly from Japan. BITA grafting leads to significantly fewer cardiac-related events, but not superior overall survival, when compared to SITA grafting25. BITA grafting also may lead to reduced MACE in DM patients, although no significant difference was observed in the overall cohort17. Although most patients in our study underwent off-pump CABG, previous studies included both on-pump and off-pump procedures. This reflects changing surgical trends in Japan, where surgeons have switched from on-pump to off-pump CABG between the late 1990s and early 2000s, during which time the off-pump technique evolved25,26. Propensity-matched analysis of off-pump CABG in hemodialysis patients was reported in 2018, which better reflected contemporary practices in Japan. Here, BITA grafting had no advantages for mid-term overall survival, freedom from cardiac death, or from cardiac events 15.
BITA grafting achieved a significantly better MACE-free rate and resulted in significantly fewer cardiac deaths. Though not significantly different, the BITA group showed superior 5-year overall survival rates over those of the SITA group. This may be because GEA use (in 4.2% of patients) in the SITA group was less common than in previous reports (22.3% in Nakahara et al.’s study) 15. Multiple arterial grafting offers some survival benefit over single arterial grafting27,28. Although we tried to use GEAs, they are often calcified and ungraftable in dialysis patients, and are prone to flow competition with the native coronary artery29. Therefore, to improve the patency of SVGs, we started no-touch harvesting in 2019, whose long-term patency is equal to ITAs30,31. Future analyses should clarify the efficacy of no-touch SVGs compared to GEA grafts.
Multivariate analysis revealed that age and incomplete revascularization significantly predicted remote death. Incomplete revascularization during off-pump CABG was an independent predictor of cardiac death, which was more pronounced in patients with impaired heart function32. In cases with difficult complete surgical revascularization, hybrid revascularization involving CABG and percutaneous coronary intervention should be considered to minimize perioperative risk and prevent remote cardiac death.
There are several limitations to this study. First, this was a single-center, non-randomized, retrospective, and observational study. Second, the number of patients was relatively small; no definitive conclusions could be reached. Third, the follow-up period was relatively short.