Observational Study Affirms Higher Kidney Injury Risk After CABG vs PCI

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The likelihood of developing acute kidney injury (AKI) is higher after coronary artery bypass grafting (CABG) than after percutaneous coronary intervention (PCI) for multivessel disease, according to a study published in the September 9, 2014, issue of the Journal of the American College of Cardiology.

Relatively few such patients will require dialysis as a result, but “because more than 1 million coronary revascularizations are performed each year in the United States, procedure-related AKI may account for several hundred new patients requiring maintenance dialysis each year, exacting a large physical, mental, and financial toll on patients and the health care system,” write Alan S. Go, MD, of Kaiser Permanente Northern California (Oakland, CA), and colleagues. “Our findings underscore the need to include the risk for AKI when considering revascularization strategies for multivessel coronary disease and to continue to work to decrease the high incidence of AKI after coronary revascularization overall.”

Methods
Dr. Go and colleagues retrospectively analyzed 2 observational cohorts of patients undergoing a first documented coronary revascularization for multivessel disease: patients treated within their hospital system from January 1996 through December 2008, and a nationally representative sample of fee-for-service Medicare beneficiaries treated between 1992 and 2008. The researchers used propensity scoring to match 1,004 patients undergoing PCI with 1,933 undergoing CABG in the Kaiser cohort and to match 52,578 patients undergoing each procedure in the Medicare cohort.
AKI was defined in the Kaiser cohort as an increase in serum creatinine of ≥ 0.3 mg/dL or to ≥ 150% above baseline, a ≥ 4.0 mg/dL absolute increase with an acute increase of at least 0.5 mg/dL, or use of renal replacement therapy. In the Medicare cohort, it was defined according to discharge diagnosis codes and use of dialysis.


AKI Common, But Dialysis Rare

The rate of AKI was 20.4% in the Kaiser cohort and 6.2% in the Medicare cohort; the odds of developing the complication were higher after CABG vs PCI in both cohorts (table 1). 

Table 1. Odds of AKI with CABG vs PCI by Cohort

 

OR

95% CI

Kaiser

1.60

1.30-1.96

Medicare

2.56

2.42-2.71


In the Kaiser cohort, the strength of the relationship did not vary according to baseline kidney function or diabetes status. However, in the Medicare cohort the association was weaker in patients with vs without either pre-existing chronic kidney disease (OR 2.10 vs 2.79) or diabetes (OR 2.14 vs 2.98).

The percentage of patients who developed AKI severe enough to require dialysis was only 0.4% in the Kaiser group and 0.2% in the Medicare group. Further analysis of this endpoint was not possible for the Kaiser patients due to low numbers.

Medicare patients were more likely to develop AKI requiring dialysis after CABG than after PCI both in the overall cohort (0.4% vs 0.1%; P < .0001) and in the subgroup with pre-existing chronic kidney disease (2.9% vs 1.3%; P < .0001). Of the patients who needed dialysis during hospitalization, 14.9% still required it 90 days later. 

Should AKI Risk Factor into Revascularization Decision?

AKI has been associated in prior studies with longer hospital stays, more periprocedural complications, and higher long-term risks of chronic kidney disease, end-stage renal disease, and death, the authors note, adding that their findings support incorporating AKI risk into the revascularization decision for multivessel disease. This decision “must balance the higher periprocedural morbidity and mortality risks with the long-term survival advantages of CABG compared with PCI,” Dr. Go and colleagues write, noting that this is particularly important for patients with underlying chronic kidney disease. 

Additionally, preferences and circumstances of individual patients need to be considered, they say. “For some patients, the risk for requiring long-term dialysis may pose such a large quality-of-life threat that they may prefer PCI, despite the shorter long-term survival associated with this strategy; the opposite may be true for other patients.” 

Richard Solomon, MD, of the University of Vermont (Burlington, VT), agreed that the threat of dialysis—though “extremely small”—could be an issue for certain patients, particularly those with the most severe deficits in kidney function before the procedure and in the elderly, who might not be willing to accept the risk of lifelong dialysis for a survival benefit they might not obtain. But, he told TCTMD in a telephone interview, “it’s probably not going to enter into the decision making regarding PCI vs bypass surgery for most patients.”

Dr. Solomon pointed out that even though the study affirms the higher risk of AKI following CABG, it is limited by the possibility of confounding by factors that could not be accounted for using propensity scoring.

The study authors acknowledge that their analysis did not include information on left ventricular function, use of cardiopulmonary bypass during CABG, or the amount or type of contrast used during PCI—all factors that have been associated with the development of post-revascularization AKI.

 


Source:
Chang TI, Leong TK, Boothroyd DB, et al. Acute kidney injury after CABG vs PCI: an observational study using 2 cohorts. J Am Coll Cardiol. 2014;64:985-994.

 

Disclosures:

 

  • The study was supported by the American Heart Association.
  • Drs. Go and Solomon report no relevant conflicts of interest.

 

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