Mortality Varies by Revascularization Method in Dialysis Patients

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Dialysis patients who undergo coronary artery bypass graft (CABG) surgery have higher in-hospital mortality than those who receive drug-eluting stents (DES), according to a large observational study of US practice patterns published online April 9, 2013, in Circulation. CABG is associated with better long-term survival, however, and less need for repeat revascularization.

Charles A. Herzog, of the University of Minnesota, Minneapolis (Minneapolis, MN), and colleagues used the United States Renal Data System to identify 23,033 Medicare patients on dialysis who underwent CABG (n = 6,178) or were implanted with DES (n = 11,844) or BMS (n = 5,011) between 2004 and 2009. Of the CABG surgeries, 4,521 (73%) were performed using an internal mammary graft (IMG). CABG patients tended to be younger than PCI patients and less likely to have hypertension as the primary cause of renal failure.

CABG Good for the Long Haul

In-hospital mortality was highest for CABG (8.2%) and lowest for DES (2.7%), with BMS falling in between (4.9%; P < 0.0001 vs. DES). But on Kaplan-Meier analysis, CABG provided the highest long-term survival (table 1).

Table 1. Kaplan-Meier Survival Estimates

In addition, in-hospital mortality was numerically lower for CABG patients who received an IMG than for those who received another type of graft (7.8% vs. 9.3%; P = 0.059). By 2 years, use of an IMG conferred a significant survival advantage among CABG patients (59.6% vs. 50.6%; P < 0.0001).

More than half (55.1%) of the 14,000 deaths that occurred were related to cardiovascular causes and 9.6% to infection, which was more commonly the reason for mortality in CABG patients compared with PCI patients. Withdrawal from dialysis caused 7.4% of deaths.

Independent predictors of mortality were higher age, longer dialysis duration, and comorbidities, while African-American race was associated with lower mortality for CABG (HR 0.88; 95% CI 0.81-0.95; P = 0.0009), DES (HR 0.87; 95% CI 0.82-0.91; P < 0.0001), and BMS (HR 0.86; 95% CI 0.79-0.94; P = 0.006). Diabetes did not affect mortality risk.

Repeat revascularization was required for 12.5% of CABG patients, 28.7% of DES patients, and 24.9% of BMS patients.

Over the course of the study period, the overall number of annual revascularization procedures decreased from 4,347 in 2004 to 3,344 in 2009. While the proportion of CABG procedures remained steady at approximately 25% to 30%, DES were more commonly used than BMS toward the beginning of the study from 2004 to 2006 at 59% vs. 15% of all procedures, respectively. The pattern abruptly changed starting in 2007, when BMS use grew by 85% and DES use dropped by 41%. Preliminary data from 2010 not included in the current analysis suggest a rebound for DES.

DES May Work When Mammary Grafts Not an Option

The researchers caution against making direct comparisons among the 3 procedure types, given that the choice of treatment in clinical practice depends on complex patient- and lesion-related variables that cannot be captured using an administrative database. “To derive conclusions directly applicable to clinical practice, a prospective randomized study would be the ideal method of evaluating comparative outcomes of dialysis patients undergoing PCI with DES versus CABG surgery,” they advise.

That said, Dr. Herzog and colleagues propose that “DES may be a reasonable consideration in dialysis patients in whom an IMG . . . is not an appropriate option in the revascularization strategy, or whose overall life expectancy is judged to be limited.

“For some patients, PCI with DES might be preferable,” they continue, “as the higher perioperative mortality (and likely morbidity) of CABG might be judged to be an inferior choice, despite potentially superior long-term survival.”

Such nuanced decisions illustrate the need for a multidisciplinary “heart team approach,” the investigators note.

Dialysis Patients Are Different

In addition, the paper points out that the lack of long-term benefit with DES in this population demonstrates the unique characteristics of patients with end-stage renal disease, whose lesions often have severe calcification and medial thickening. Neointimal hyperplasia and late lumen loss are also increased in this subgroup, accompanied by higher rates of in-stent restenosis, which tends to be diffuse.

“Finally, the pathophysiological factors underlying the process of accelerated atherosclerosis also predispose to stent thrombosis, a phenomenon of particular concern with DES,” the researchers add.

 

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Source:
Shroff GR, Solid CA, Herzog CA. Long-term survival and repeat coronary revascularization in dialysis patients following surgical and percutaneous coronary revascularization with drug-eluting and bare metal stents in the United States. Circulation. 2013;Epub ahead of print.

 

 

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