LOS ANGELES—Baseline renal function is highly associated with worse 90-day outcomes among patients undergoing primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (STEMI), investigators reported at the American Heart Association Scientific Sessions 2012.

John P. Vavalle, MD, MHS, an interventional cardiology fellow at Duke University Medical Center in Durham, N.C., and colleagues elsewhere examined the impact of baseline renal disease on outcomes in patients undergoing primary PCI for STEMI as part of the 4,897-patient Assessment of Pexelizumab in Acute Myocardial Infarction (APEX AMI) trial. The impact of renal disease on outcomes in STEMI patients undergoing primary PCI has not been widely studied, Dr. Vavalle noted.

The new study is notable for patient population, he said. “Our analysis included patients with very advanced renal disease, including patients on dialysis, while many clinical trials similar to APEX had previously excluded these populations,” he commented. “So we have a very rich dataset.”

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Dr. Vavalle’s team estimated patients’ glomerular filtration rate (GFR, mL/min/1.73m2) using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation and classified patients according to stages of CKD by GFR.

Results showed a stepwise significant increase in the pre-specified 90-day composite outcome of death, shock, and heart failure, which correlated directly with the degree of renal impairment. The incidence of 90-day death, shock, or heart failure was 4.5%, 8.0%, 19.9%, and 30.3% among patients with a GFR above 90, 60-90, 30-60, and below 30, respectively. The incidence was 37.5% among patients on dialysis at baseline.

Compared with subjects who had normal renal function, patients with a GFR below 30 had an almost eightfold increased risk of death, shock, or heart failure at 90 days.

Additionally, patients with more severe CKD had significantly longer delays to PCI. The time from symptom onset to primary PCI was 4.2 hours in dialysis-dependent patients and 3.3 hours in patients with a GFR above 90.

Despite a similar distribution of pre-intervention Thrombolysis in Myocardial Infarction (TIMI) flow grades in the coronary arteries, post-intervention angiographic outcomes were significantly worse with increasing degrees of renal failure.

Patients with worse renal function at baseline also had significantly higher rates of atrial fibrillation, severe bleeding, infection, mechanical complications, and time spent in the intensive care unit.

“So, the take-home message is that we found worse outcomes across the board with worse baseline renal function,” Dr. Vavalle said. 

The analysis also revealed that the factors most likely to predict in-hospital, post-catheterization, and acute kidney injury (AKI) in STEMI patients undergoing PCI were age, female gender, presenting Killip class III or IV heart failure, and PCI duration. In this analysis, PCI duration was used as a surrogate for exposure to contrast media.

“Many times, in the throes of an acute ST-elevation MI, we take patients to the cath lab emergently without any knowledge of their baseline renal function,” Dr. Vavalle said. “If we do know the patient’s baseline renal function, we are often very concerned about those patients with baseline renal disease because we tend to think that they are at higher risk of acute renal failure or AKI. However, our data suggest that in this population the risk of AKI is not highly associated with baseline renal function, and provide further evidence that we should take these STEMI patients to the cath lab without delay and use as little contrast as we need to get the job done with the understanding that these patients with baseline renal disease are more likely to have poorer angiographic and long-term outcomes.”