Jennie Z. Ma

Comparative Survival of Dialysis Patients in the United States After Coronary Angioplasty, Coronary Artery Stenting, and Coronary Artery Bypass Surgery and Impact of Diabetes

Background—The optimal method of coronary revascularization in dialysis patients is controversial. The purpose of this study was to compare the long-term survival of dialysis patients in the United States after PTCA, coronary stenting, or CABG. Methods and Results—Dialysis patients hospitalized from 1995 to 1998 for first coronary revascularization procedures after renal replacement therapy initiation were identified from the US Renal Data System database. All-cause and cardiac survival was estimated by the life-table method and compared by the log-rank test. The impact of independent predictors on survival was examined in a Cox regression model. The in-hospital mortality was 8.6% for 6668 CABG patients, 6.4% for 4836 PTCA patients, and 4.1% for 4280 stent patients. The 2-year all-cause survival (mean±SEM) was 56.4±1.4% for CABG patients, 48.2±1.5% for PTCA patients, and 48.4±2.0% for stent patients (P <0.0001). After comorbidity adjustment, the relative risk (RR) for CABG (versus PTCA) patients was 0.80 (95% CI 0.76 to 0.84, P <0.0001) for all-cause death and 0.72 (95% CI 0.67 to 0.77, P <0.0001) for cardiac death. For stent (versus PTCA) patients, the RR was 0.94 (95% CI 0.88 to 0.99, P =0.03) for all-cause death and 0.92 (95% CI 0.85 to 0.99, P =0.04) for cardiac death. In diabetic (versus PTCA) patients, the RR for CABG surgery was 0.81 (95% CI 0.75 to 0.88, P <0.0001) for all-cause death and 0.71 (95% CI 0.64 to 0.78, P <0.0001) for cardiac death, and the RR for the stent procedure was 0.99 (95% CI 0.91 to 1.08, P =NS) for all-cause death and 0.99 (95% CI 0.89 to 1.11, P =NS) for cardiac death. Conclusions—In this retrospective study, dialysis patients in the United States had better long-term survival after CABG surgery than after percutaneous coronary intervention. Stent outcomes were relatively worse in diabetic patients. Our data support the need for large clinical registries and prospective trials of surgical and percutaneous coronary revascularization procedures in dialysis patients.

Mortality risks of peritoneal dialysis and hemodialysis

Studies of outcomes associated with dialysis therapies have yielded conflicting results. Bloembergen et al showed that prevalent patients on continuous ambulatory peritoneal dialysis (CAPD) or continuous cycling peritoneal dialysis (CCPD) had a 19% higher mortality risk than hemodialysis patients, and Fenton et al, analyzing Canadian incident patients, found a 27% lower risk. Attempting to reconcile these differences, we evaluated incident Medicare patients (99,048 on hemodialysis, 18,110 on CAPD/CCPD) from 1994 through 1996, following up to June 30, 1997. Patients were followed to transplantation, death, loss to follow-up, 60 days after modality change, or end of the study period. For each 3-month survival period, we used an interval Poisson regression to compare death rates, adjusting for age, gender, race, and primary renal diagnosis. A Cox regression was used to evaluate cause-specific mortality, and proportionality was addressed in both regressions by separating diabetic and nondiabetic patients. The Poisson regressions showed CAPD/CCPD to have outcomes comparable with or significantly better than hemodialysis, although results varied over time. The Cox regression found a lower mortality risk in nondiabetic CAPD/CCPD patients (women younger than 55 years: risk ratio [RR] = 0. 61; Cl, 0.59 to 0.66; women age 55 years or older: RR = 0.87; Cl, 0. 84 to 0.91; men younger than 55 years: RR = 0.72; Cl, 0.67 to 0.77; men age 55 years or older: RR = 0.87; Cl, 0.83 to 0.92) and in diabetic CAPD/CCPD patients younger than 55 (women: RR = 0.88; Cl, 0. 82 to 0.94; men: RR = 0.86; Cl, 0.81 to 0.92). The risk of all-cause death for female diabetics 55 years of age and older, in contrast, was 1.21 (Cl, 1.17 to 1.24) for CAPD/CCPD, and in cause-specific analyses, these patients had a significantly higher risk of infectious death. We conclude that, overall, within the first 2 years of therapy, short-term CAPD/CCPD appears to be associated with superior outcomes compared with hemodialysis. It also appears that patients on the two therapies have different mortality patterns over time, a nonproportionality that makes survival analyses vulnerable to the length of follow-up. Further investigation is needed to evaluate both the potential explanations for these findings and the use of more advanced statistical methods in the analysis of mortality rates associated with these dialytic therapies.

A comparison of coronary angioplasty and coronary artery bypass grafting outcomes in chronic dialysis patients

The objective of this study was to compare the outcomes of angina, myocardial infarction (MI), cardiac death, and all-cause death following percutaneous transluminal coronary angioplasty (PTCA) or coronary artery bypass grafting (CABG). The study design was based on retrospective, nonrandomized analysis and was set in referral teaching hospitals and community hospitals. Eighty-four chronic dialysis patients with symptomatic coronary artery disease without prior revascularization were included in the study. Twenty-four patients underwent PTCA of one or more vessels, and 60 patients underwent CABG. Recurrence of angina, MI, cardiac death, and all-cause death following revascularization as well as the number of inpatient days preprocedure and postprocedure were recorded. The two patient groups were comparable in terms of age, sex, history of MI, left ventricular mass and function, and angina severity. Diabetes mellitus was more prevalent in the PTCA group. The CABG group had more severe coronary artery disease. The 2-year survival rate of the CABG patients (66%; 95% confidence interval = 53.79) did not differ from that of the PTCA patients (51%; 95% confidence interval = 27.65). Thirteen PTCA patients were restudied 106 +/- 108 days after recurrence of angina; nine (69%) of these patients were found to have angiographic restenosis. The postprocedure risk of angina and the combined endpoints of angina, MI, and cardiovascular death were significantly greater following PTCA than CABG. Percutaneous transluminal coronary angioplasty was the only consistent predictor of outcomes; the adjusted relative risks (compared with CABG) of postprocedure angina and combined endpoints were 16.4 and 10.2, respectively, and were several-fold higher than the unadjusted risks. We conclude that in chronic dialysis patients with symptomatic coronary disease, patients undergoing PTCA have a higher risk of subsequent angina and combined angina, MI, and cardiovascular death than those undergoing CABG. The optimal approach to coronary revascularization in this patient population remains to be determined.

Trends in anemia treatment with erythropoietin usage and patient outcomes

Recombinant erythropoietin, first approved for Medicare reimbursement in June 1989, was prescribed at initial doses for dialysis patients of 2,500 to 2,700 U per administration independent of hematocrit level. By 1997, however, patients with hematocrits less than 30% were administered 6,000 U/dose, compared with 4,500 U administered to patients with hematocrits of 33% to 36%. Since 1990, the percentage of patients with hematocrits less than 30% decreased from 60% to 22% in 1997, whereas the percentage of patients with hematocrits of 33% to 36% increased from 10% to 30%. In 1997, Medicare initiated the Hematocrit Measurement Audit (HMA) policy, which was directed at reducing the percentage of claims for hematocrits greater than 36% and increasing the stability of the hematocrit levels. The policy change achieved the initial effect but resulted in a reduction of the mean hematocrit as well. The policy was changed in 1998 in response to patient and provider concerns. Mortality studies show that hematocrits less than 30% (or hemoglobin levels < 110 g/L) are associated with an 18% to 40% increased associated risk for death. Higher hematocrits of 33% to 36% appear to be associated with a 7% reduced risk for death. The risk for hospitalization parallels that of mortality. Patients with sustained hematocrits of 33% to 36% over 1 year appear to have the best outcome compared with patients with hematocrits that decrease. The latter are at greater risk than those patients in whom the hematocrits increase. In conclusion, dramatic improvements in hemodialysis patient hematocrits have occurred since 1989. Mortality and hospitalization studies support the National Kidney Foundation Dialysis Outcomes Quality Initiative (NKF DOQI) target hematocrit range of 33% to 36% as providing the best associated outcomes.

Serum albumin and mortality after renal transplantation

The incidence, causes, and consequences of hypoalbuminemia after renal transplantation are not well defined. We examined clinical correlates of serum albumin measured at 3 months, 6 months, 1 year, and annually thereafter in 706 renal transplant recipients who survived at least 6 months with a functioning allograft. Follow-up was 7.0 +/- 4.2 years. Hypoalbuminemia (< or = 3.5 g/dL) was most common at 3 months (31%, n = 692), least common at 1 year (12%, n = 656), and then became increasingly common among survivors, for example, 14% (n = 466) at 4 years, 20% (n = 204) at 8 years, and 29% (n = 77) at 12 years after transplantation. By multiple linear regression, variables that correlated (P < 0.05) with lower serum albumin at 3, 6, 12, and 24 months included age, diabetes, proteinuria, and cytomegalovirus infection. Other independent correlates on at least one of these occasions included renal function and chronic disease (malignancy, liver disease, and cardiovascular disease). Serum albumin, as a time-averaged and time-dependent covariate, was a strong independent risk factor for death using Cox proportional hazards analysis (relative risk for each g/dL increment, 0.26; 95% confidence interval, 0.16 to 0.44 [1.00 = no risk]). The effects of albumin on mortality were independent of age, diabetes, serum lipids, renal function, chronic liver disease, malignancies, and cardiovascular disease. The effects of albumin on mortality were evident even when the analysis was restricted to patients dying several years after albumin was measured. Thus, hypoalbuminemia is common and serum albumin is a strong independent risk factor for all-cause mortality after renal transplantation.