Coronary artery disease (CAD) is the leading cause of morbidity and mortality in patients with chronic kidney disease (CKD), but no study has yet compared the short- and long-term outcomes of coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI) with drug-eluting stents for multivessel CAD among non-hemodialysis-dependent (HD) patients with CKD. In our institution’s registry, we identified 812 patients with CKD (glomerular filtration rate <60 ml/min) who had undergone either CABG or PCI for multivessel CAD from May 2003 to December 2006. Of these patients, 725 had non-HD CKD, and 87 were hemodialysis-dependent. The rates of 30-day and long-term mortality, 30-day major adverse cardiovascular events, and hemodialysis dependence after revascularization were compared between these 2 groups by computing the hazard ratios from a Cox proportional hazards model and adjusting them for the baseline covariates and propensity score. After either CABG or PCI, 2.4% of the patients with non-HD CKD were hemodialysis dependent. Compared to PCI, CABG was associated with postoperative hemodialysis dependence (odds ratio 3.2, 95% confidence interval 1.1 to 9.3; p <0.001). However, among patients with non-HD CKD and 3-vessel CAD, those who underwent CABG tended to have a lower long-term mortality rate than those who underwent PCI (hazard ratio 0.61, 95% confidence interval 0.36 to 1.03; p = 0.06). In the patients with non-HD CKD treated for 2-vessel CAD, those who underwent CABG or PCI had a similar long-term mortality risk (hazard ratio 1.12, 95% confidence interval 0.52 to 2.34; p = 0.7). In conclusion, in patients with non-HD CKD and multivessel CAD, CABG led to better survival than PCI with drug-eluting stents, but CABG patients had a greater short-term risk of requiring permanent hemodialysis.
Coronary artery disease (CAD) is the leading cause of death in patients with chronic kidney disease (CKD). Patients with CKD who undergo coronary revascularization have worse survival than other patients with CAD. Observational studies comparing coronary artery bypass grafting (CABG), percutaneous coronary intervention (PCI), and medical therapy in patients with CKD have suggested that CABG might produce better long-term survival than PCI. However, most of these studies were done in the bare-metal stent era. The advent of drug-eluting stents and aggressive metabolic control treatment regimens has made PCI significantly more reliable. Although large registry studies of the general population have suggested that CABG leads to better survival than PCI, even with the more reliable drug-eluting stent, the risk of surgical complications and worsening kidney function after CABG might alter the relative benefit of these treatments for patients with CKD. The availability of drug-eluting stents has decreased the restenosis and repeat revascularization rates in the CKD patient population, much as it has in the general population. Therefore, we examined the complication and survival rates of patients treated with drug-eluting stent-PCI or CABG in a retrospective, nonrandomized analysis.
Methods
We identified 812 consecutive patients with CKD who underwent either CABG or drug-eluting stent-PCI for multivessel CAD at the Texas Heart Institute at St. Luke’s Episcopal Hospital (Houston, Texas) from May 1, 2003 to December 31, 2006. The stent implantation methods used have been previously described. In the CABG procedures, internal mammary artery grafts were used whenever possible, and complete revascularization with arterial and venous grafts was attempted.
The study was performed by using data from the Texas Heart Institute Research Database (THIRDBase). The patient data, coronary anatomic characteristics, and procedural data were collected for all patients. Follow-up was established by interviewing the patients and by consulting the United States vital statistics database and the Social Security Death Index.
We defined CKD as an estimated glomerular filtration rate of <60 ml/min/1.73 m 2 . The estimated glomerular filtration rate was calculated by using the 4-variable Modification of Diet in Renal Disease study equation: estimated glomerular filtration rate = 186.3 × (serum creatinine mg/dl) −1.154 × age −0.203 × (0.742 if female) × (1.21 if black). Patients with an estimated glomerular filtration rate <60 ml/min were divided into an end-stage renal disease group (patients with an estimated glomerular filtration rate <15 ml/min or dialysis dependence, or both) and a non-hemodialysis-dependent (HD) CKD group with an estimated glomerular filtration rate <60 ml/min but >15 ml/min. The other variables recorded included hypertension (defined as a documented history of hypertension or current use of antihypertensive drugs), angina severity (Canadian Cardiovascular Society class), congestive heart failure (New York Heart Association class), diabetes mellitus (fasting blood glucose level >125 mg/dl or use of hypoglycemic agents), peripheral vascular disease, stroke, chronic obstructive pulmonary disease, number of diseased vessels, and dyslipidemia (documented hyperlipidemia or use of lipid-lowering medications). Patients were excluded if they had stenosis >50% in the left main coronary artery, acute myocardial infarction within the previous 7 days, redo CABG or saphenous vein graft stenting, emergency CABG, concomitant operations such as mitral valve or aortic valve repair, renal transplant, or PCI without stent placement.
The outcomes studied included 30-day all-cause mortality, 30-day major adverse cardiovascular events (death, myocardial infarction, stroke, revascularization, hemodialysis dependence, and repeat revascularization), and long-term all-cause mortality.
The Student t test was used to compare continuous variables, and the chi-square test or Fisher’s exact test was used to analyze the categorical variables, as appropriate. A logistic regression model with a forward stepwise variable selection process was developed to determine the clinical predictors of major adverse cardiovascular events and early mortality in the non-HD CKD and end-stage renal disease groups separately.
Propensity score analysis was performed to control for selection bias. The 25 variables used to calculate the score included proximal left anterior descending artery CAD, body mass index, age, gender, Canadian Cardiovascular Society angina class, New York Heart Association functional class, unstable angina, history of myocardial infarction, hypertension, diabetes mellitus, smoking, stroke, peripheral vascular disease, and neoplasm. Unadjusted Kaplan-Meier survival curves were constructed, and the curves were compared by using the log-rank test. The propensity score was subsequently included in the Cox proportional hazards model as a covariate to calculate the hazard ratios (HRs). Retrospective power analysis, which is widely considered invalid by statisticians, was not performed. The statistical analyses were performed by using Statistical Analysis System software, version 9.1.3 (SAS Institute, Cary, North Carolina).
Results
Of the 812 patients who met the criteria for inclusion in the present study, 87 were in the end-stage renal disease group. Of these, 54 underwent CABG and 33 underwent PCI with drug-eluting stents. Of the patients with non-HD CKD, 241 patients underwent CABG and 484 underwent PCI with drug-eluting stents. A total of 268 arterial grafts and 637 venous grafts were used during CABG, and 536 drug-eluting stents were placed during PCI.
A comparison of patient characteristics ( Table 1 ) showed that the patients with non-HD CKD who underwent CABG were more likely to be younger, male, and obese, to have a history of smoking and chronic obstructive pulmonary disease, and to have proximal left anterior descending artery disease than those who underwent PCI. In both the non-HD CKD and the end-stage renal disease groups, most patients who underwent CABG had 3-vessel CAD (74% and 76%, respectively). However, the patients with non-HD CKD and those in the end-stage renal disease group who underwent PCI had comparable rates of 2-vessel and 3-vessel CAD.
| Variable | Non-HD CKD (n = 725) | ESRD (n = 87) | ||||
|---|---|---|---|---|---|---|
| DES-PCI (n = 484) | CABG (n = 241) | p Value | DES-PCI (n = 33) | CABG (n = 54) | p Value | |
| White | 90% | 93% | 0.27 | 82% | 70% | 0.29 |
| Age (>65 years) | 72% | 67% | 0.14 | 41% | 30% | 0.36 |
| Men | 60% | 67% | 0.07 | 31% | 30% | 0.9 |
| Diabetes mellitus | 11% | 13% | 0.4 | 35% | 33% | 0.9 |
| Lipid-lowering drugs | 79% | 71% | 0.01 | 63% | 49% | 0.26 |
| Smoker | 47% | 54% | 0.003 | 39% | 45% | 0.6 |
| Body mass index >26 kg/m 2 | 23% | 27% | 0.2 | 20% | 21% | 0.9 |
| Canadian Cardiovascular Society angina class III or IV | 37% | 33% | 0.3 | 43% | 42% | 0.9 |
| Previous myocardial infarction | 19% | 18% | 0.7 | 24% | 24% | 0.9 |
| New York Heart Association class III or IV | 40% | 56% | <0.001 | 31% | 24% | 0.26 |
| Peripheral vascular disease | 28% | 28% | 0.9 | 37% | 36% | 0.9 |
| Previous neoplasm | 13% | 16% | 0.2 | 6% | 19% | 0.07 |
| Previous stroke | 10% | 10% | 0.8 | 13% | 24% | 0.2 |
| Previous chronic obstructive pulmonary disorder | 27% | 37% | 0.012 | 37% | 52% | 0.21 |
| Valvular heart disease not requiring surgery | 14% | 10% | 0.19 | 9% | 9% | 0.9 |
| Proximal left anterior descending artery disease | 44% | 58% | <0.001 | 46% | 48% | 0.9 |
| No. of narrowed coronary arteries | <0.01 | <0.01 | ||||
| 2 | 53% | 26% | 52% | 24% | ||
| 3 | 47% | 74% | 48% | 76% | ||
In the non-HD CKD group, the unadjusted 30-day mortality rate was similar after CABG and PCI (4.6% vs 2.3%; p = 0.09). The method of revascularization was not a predictor of short-term mortality on multivariate regression analysis (odds ratio [OR] 2.1, 95% confidence interval [CI] 0.84 to 5.3; p = 0.1). Instead, the predictors were heart failure (New York Heart Association class III or IV; OR 4.2, 95% CI 1.2 to 14.1; p = 0.02), history of myocardial infarction (OR 2.8, 95% CI 1.1 to 7.2; p = 0.04), and history of stroke (OR 4.5, 95% CI 1.4 to 14.7; p = 0.01). The short-term major adverse cardiovascular event rates were greater in the patients who had undergone CABG (15%) than in those who had undergone PCI (7.5%; p = 0.002). The PCI patients required more repeat revascularization at 30 days than did the CABG patients (2.7% vs 0.4%, respectively; p = 0.04).
Patients with non-HD CKD had a 2.5% incidence of hemodialysis dependence within 30 days after any revascularization procedure. On univariate analysis, more patients from the CABG subgroup became dialysis dependent than patients from the PCI subgroup (4.2% vs 1.5%, respectively; p = 0.02). Multivariate analysis showed that CABG independently predicted postprocedural hemodialysis dependence (OR 3.2, 95% CI 1.1 to 9.3; p = 0.03).
In the end-stage renal disease group, the unadjusted 30-day mortality was not significantly different between patients who had undergone CABG and those who had undergone PCI (6.1% vs 3.7%, respectively; p = 0.6). On multivariate analysis, the CABG and PCI subgroups had comparable 30-day mortality (HR 0.4, 95% CI 0.02 to 6.3; p = 0.4). The unadjusted rate of major adverse cardiovascular events was greater in the CABG subgroup (18%) than in the PCI subgroup (3.8%; p = 0.01). The repeat revascularization rates at 30 days were similar between the PCI and CABG patients in the end-stage renal disease group (1.9% vs 0%; p = 0.9).
Patients with non-HD CKD were followed up for a median period of 822 days in the PCI subgroup and 828 days in the CABG subgroup. The unadjusted long-term survival rate for all patients with non-HD CKD ( Figure 1 ) was not different for those in the CABG subgroup (85%) and the PCI subgroup (86%; log-rank p = 0.5). The long-term mortality rate adjusted for the propensity score and confounding variables was not significantly different between the patients with non-HD CKD who underwent CABG or PCI (HR 0.7, 95% CI 0.46 to 1.13; p = 0.16; Figure 2 ).
