Cardiovascular diseases are common complications of CKD and also are the most common cause of death[1]. According to the United States Renal Data System (USRDS), the cardiac mortality accounts for approximately 45%[7]. It is increasingly recognized that patients with advanced CKD who underwent revascularization had worse outcomes than that with normal renal function. However, there is a lack of international guidelines for revascularization therapy for CKD patients in the worldwide.
In our research, patients in the CABG group were relatively young, basically less than 65 years old and were mainly male; the proportion of emergency operations was relatively low, the preoperative cardiac function and size were basically normal, all surgeries were simple bypass surgeries and OPCABG accounted for nearly 90%. The low risk factors and the good preoperative baseline status could have reduced the mortality rates and incidences of complications. There are some studies on the analysis of risk factors for CABG mortality in advanced CKD patients, Li et al.[8] reported 134 cases of dialysis patients who underwent CABG and found that age, history of cerebral stenosis and emergency surgery were risk factors for death. Gautam R. Shroff[9] reported that age over 65 years, white race, peritoneal dialysis and heart failure were independent risk factors for death. ASCERT[10] indicated that the risk factors for death include age, COPD, cerebrovascular diseases, low EF, female, preoperative IABP, CPB, combined surgery, CCS/NYHA grade IV and incomplete vascularization.
The risk of surgery for advanced CKD patients is higher than that for general patients. Valentino Bianco et al.[11] reported that dialysis patients had a higher operative (30-day) mortality (8.6%), higher blood transfusion rate, higher rate of ventilator use for more than 24 h, higher incidence of sternal wound infection, second thoracotomy and new-onset AF. Rahmanian et al.[12] found that the mortality rate for dialysis patients undergoing cardiac surgeries was 3.9 times (12.7%) that for general patients and that dialysis was a risk factor for in-hospital death, which may be due to preoperative dysregulation of blood calcium and phosphorus, abnormal blood lipids and platelet metabolism, and severe coronary artery calcification in ESRD patients. In this study, the in-hospital mortality rate (9.3%) for the CABG group and the incidence of perioperative complications were roughly similar to that previously reported in western countries.
For CAD patients combined with advanced CKD, it is still controversial whether CABG or PCI should be chosen for revascularization. Chung Hee Baek[13] reported that the CABG group had fewer MACCEs than the DES group but that the overall survival rate did not differ. Manabe S[14] reported that the MACCE-free survival rate and angina-free survival rate were significantly higher in patients receiving CABG surgery than in those receiving PCI. Terazawa et al.[15] analyzed 125 dialysis patients who underwent CABG and PCI found that revascularization with CABG was superior to DES. Akira Marui[3] reported that PCI and CABG exhibited no significant difference in all-cause death; however, the PCI group had a higher risk of revascularization than the CABG group. In 2014, ESC/EACTS reported that CABG was superior to PCI for treating CAD patients with moderate to severe renal diseases[16]. In the present study, we found that the two groups exhibited no significant differences at the end of the 1-year follow-up. But during the end of the 5-year follow-up, the CABG group had a better survival rate, higher freedom from MACCEs and freedom from revascularization than the PCI group, indicating that the treatment efficacy of CABG was better than that of PCI.
The long-term survival rate of the CABG group in our study was slightly higher than that reported abroad. Gaudam R. Shroff et al.[9] reported that the 1- and 5-year survival rates in CABG were 70% and 28%, while the DES group had 1- and 5-year survival rates of 71% and 24%, respectively. Leontyev et al.[17] analyzed 483 dialysis patients who underwent CABG and found that the 2, 4, and 6-year survival rates were 64.1%, 42.2%, and 30.6%, respectively. Our finding might be related to the following reasons. First, in our study, the patients had better preoperative biochemical indicators, such as liver function, hemoglobin, albumin, and had basically normal blood lipid levels. Anemia can lead to a series of pathophysiological changes, resulting in reduced quality of life and decreased patient survival. High albumin is a nutritional status and inflammation marker for dialysis patients. The CABG group in this study had hemoglobin levels of 111.29 ± 20.27 g/dl and albumin levels of 38.83 ± 6.02 g/dl, were better that those of patients in the US[18]. Second, the mainly procedure we used was OPCABG, which avoids the use of extracorporeal circulation, reduces the need for blood transfusions and the release of inflammatory mediators, and shortens ventilator assistance and ICU care time. For patients with intolerance due to compromised cardiac function, the timely use of IABP and extracorporeal circulation can ensure the safety of complete revascularization and surgery. Third, the increased survival rate may be related to the race of the patients. Rangrass et al.[19] found that the quality of life of different ethnic groups after CABG treatment varies greatly. For the Asian population, Marui et al.[3] reported that patients with three-vessel disease or left main artery disease have a better 5-year mortality rate, MI rate and revascularization rate after CABG than after PCI. Previous studies also reported that white race is a risk factor for death[10].
The reported mortality rates for dialysis patients in different countries and different regions vary. The Chinese National Renal Data System (CNRDS) reported dialysis patient mortality rates in China in 2007, 2008, 2009 and 2010 of 7.4%, 7.6%, 9.0% and 8.6%, respectively[20], lower than those reported in the United States and Japan. The possible reasons might be dialysis patients in China are generally in good condition, and the average age is relatively low. The most common primary disease is primary glomerular diseases, while in American patients, renal failure is mainly related to diabetes and hypertension[7]. Furthermore, Chinese dialysis patients mostly receive treatment in hospitals, and the contact between doctors and patients is conducive to improving patient compliance and improving long-term prognosis.
The incidence of recent and long-term revascularization in CABG group was significantly better than PCI patients, findings that may be attributable to several factors. First, CABG treatment can provide complete revascularization, however in PCI procedure criminal vessels were always firstly handled. Second, transit time flow measurement was universally used during bypass surgery to ensure long-term patency. Third, preoperative blood glucose and blood lipid levels in patients with CABG were lower than PCI. The increased blood glucose or lipid levels may reduce the patency rate of the graft or the stent.
Recently, ISCHEMIA-CKD study[21] reported that PCI did not reduce the risk of death or nonfatal myocardial infarction in patients with moderate to severe myocardial ischemia compared with drug therapy. However, this study focused on patients with moderate myocardial ischemia (61.4%), with an average follow-up time of only 2.2 years. According to our study, long-term follow-up shows that CABG could improve the prognosis of advanced CKD patients with severe myocardial ischemia, which needs more RCT studies to confirm.