By Jeffrey Zimmet, MD, PhD

Associate Professor of Medicine, University of California, San Francisco; Director, Cardiac Catheterization Laboratory, San Francisco VA Medical Center

Dr. Zimmet reports no financial relationships relevant to this field of study.

SYNOPSIS: This retrospective study of patients presenting with non-ST-segment elevation myocardial infarction showed higher mortality among patients with chronic kidney disease and lower use of coronary angiography and percutaneous coronary intervention.

SOURCE: Murray J, Balmuri A, Saurav A, et al. Impact of chronic kidney disease on utilization of coronary angiography and percutaneous coronary intervention, and their outcomes in patients with non-ST elevation myocardial infarction. Am J Cardiol 2018;122:1830-1836.

Chronic kidney disease (CKD) is a strong independent predictor of cardiac disease, profoundly affecting cardiovascular health and outcomes. CKD also clearly affects provider behavior, especially regarding the use of iodinated contrast agents and the fear of contrast-induced nephropathy. Given that a substantial proportion of patients presenting with acute coronary syndromes also carry a diagnosis of renal dysfunction, this is a highly pertinent issue that has been studied at length. Murray et al took a broad view of this problem, using the National Inpatient Sample to study trends in coronary angiography use and both percutaneous and surgical revascularization in patients with CKD presenting with non-ST-segment elevation myocardial infarction (NSTEMI). Patients were classified based on renal function into three groups: those without a CKD diagnosis, those with CKD who did not require dialysis, and those with CKD who required renal replacement therapy (RRT). For each group, the authors assessed outcomes that included mortality, length of stay, and hospitalization costs.

Among 3,654,586 hospital admissions for NSTEMI between 2001 and 2012, most were without significant CKD (group 1). A total of 533,387 patients had CKD without need for RRT (group 2), and 107,696 patients had CKD and required RRT (group 3). Reported in-hospital mortality rates were significantly higher in patients with CKD (8.6% in group 3, 6.9% in group 2) compared with those without CKD (3.9%) even after adjusting for other predictors. Mortality rates improved modestly over the study period (from 5.8% in 2001 to 3.9% in 2011), with a more marked improvement among patients in group 2 (from 13.3% in 2001 to 5.9% in 2012).

While just over half of the entire cohort underwent invasive coronary angiography, the rates differed significantly among groups, with the highest rate among those without CKD and the lowest among those with CKD who did not require RRT (54%, 36.1%, and 45.9% undergoing cardiac cath in groups 1, 2, and 3, respectively). Although the use of cardiac cath increased over the study period (from 42% in 2001 to 60% in 2012), coronary angiography rates remained significantly lower in groups 2 and 3. On the other hand, PCI rates increased significantly over the course of the study, especially among CKD patients. The use of PCI in patients in group 1 doubled over the study period, while it nearly quadrupled in group 2. Between 2001 and 2012, the overall rate of CABG use in NSTEMI patients did not change significantly, except in group 3, which saw a steady rise in CABG rates (from about 5% to about 7%). In a multivariate logistic regression analysis, PCI was associated with a lower risk of mortality (odds ratio, 0.31; P < 0.001) across all three groups, regardless of CKD. The authors drew several conclusions. CKD is associated with a higher risk of short-term mortality in patients hospitalized for NSTEMI. Patients with NSTEMI are less likely to undergo invasive cardiac cath and PCI if they have concurrent CKD. Use of coronary angiography and PCI have increased in all patients over time (more so among patients with CKD). Finally, cath and PCI were associated with better short-term survival rates, even after adjusting for baseline risk.

COMMENTARY

It should come as no surprise that CKD is associated with a higher risk of mortality as well as longer length of stay and higher hospital costs among patients presenting with NSTEMI. It also is not surprising that patients with CKD are offered invasive diagnostic and therapeutic options at lower rates compared with those with normal renal function. The fact that patients with CKD on RRT were offered these procedures at higher rates compared with those not on RRT strongly suggests that concern for causing acute kidney injury by contrast-induced nephropathy is a major deciding factor when it comes to using invasive approaches in this subset of patients. The Murray et al study supports a mortality benefit of an invasive approach in patients with NSTEMI and CKD, a population for whom there is little direct evidence and about whom guidelines are noncommittal. Overall, the results of this study are encouraging. Although the authors rightly noted the systematic underuse of invasive therapies in the CKD population, their data clearly show an increase in coronary revascularization use over the study period, with a marked concomitant improvement in mortality specific to the nondialysis CKD group. Of course, treatment decisions should be individualized; however, cardiac cath and PCI should not be withheld from these patients who stand to benefit.