LOS ANGELES – Patients with advanced chronic kidney disease who receive an implantable cardioverter defibrillator are not like other patients who receive these devices.
But results from a trio of studies reported at the meeting show how hard it is for researchers to get a clear handle on what makes chronic kidney disease patients different, whether they have different outcomes than defibrillator recipients without CKD, and what is the best approach for judiciously using implantable cardioverter defibrillators (ICDs) in patients with renal dysfunction.
Mitchel L. Zoler/IMNG Medical Media
Dr. Matthew Reynolds
It’s a particularly relevant question because CKD is linked with a substantially increased risk for sudden cardiac death (patients on dialysis have about a fivefold higher risk for sudden cardiac death, compared with patients with normal or mildly impaired renal function), but patients with CKD were excluded from the major trials that proved the efficacy of ICDs for preventing sudden cardiac death. The lack of data from randomized, prospective trials leaves questions about the efficacy, and perhaps as importantly, the cost efficiency of ICDs in CKD patients.
"Should patients with CKD get ICDs? I don’t know the answer, but I don’t think that, categorically, patients with CKD should be excluded from ICD treatment," commented Dr. Matthew Reynolds, a cardiac electrophysiologist and director of the Economics and Quality of Life Research Center at Harvard Medical School in Boston. But many patients with CKD, especially advanced disease, are not good ICD candidates.
"For a lot of patients with CKD, someone decides not to place an ICD. Those patients are not represented" in studies that focus on ICD recipients, said Dr. Reynolds, who cochaired the session where the three studies were presented.
"For every CKD patients who gets an ICD, an electrophysiologist has made a decision that this was a CKD patient who could benefit. It’s hard to extrapolate from that" to all CKD patients, agreed Dr. Paul Varosy, director of electrophysiology at the Denver Veterans Administration Medical Center. "Patients with CKD who get ICDs are fundamentally different patients."
Dr. Paul Varosy
The aim of one of the studies reported was to assess ICD efficacy in CKD patients by comparing survival between patients with ICDs divided into stage III CKD (an estimated glomerular filtration rate [GFR] of 30-59 mL/min per 1.73 m2), stage IV or V (a GFR of less than mL/min per 1.73 m2), or no CKD. The study examined 3-year follow-up data from 556 patients who received an ICD or similar device during 2006-2010 at the Minneapolis Veterans Administration Medical Center at the University of Minnesota. The series included 301 patients with no CKD, 230 with stage III CKD, and 25 patients with more severe CKD.
The analysis showed a similar incidence of appropriate and inappropriate shocks from the ICDs in all three groups, and roughly similar efficacy of the ICDs for preventing sudden cardiac death, Dr. Selcuk Adabag said at the Annual Scientific Sessions of the American Heart Association. But mortality rates rose substantially higher as renal function worsened, rising from 17% in patients without CKD to 30% in those with stage III disease, and to 56% in those with stage IV or V disease, reported Dr. Adabag, a cardiac electrophysiologist at the University of Minnesota in Minneapolis.
The mortality differences were hardly surprising, and they likely have little direct relationship to the ICDs. "In patients with CKD, the worse the disease, the worse their prognosis. CKD is a complex disease with a whole range of [mortality] risk factors; preventable sudden cardiac death is just one" of the risks these patients face, Dr. Varosy said in an interview.
Selection bias makes the ICD observations questionable, Dr. Reynolds said. "I’m very concerned about concluding that ICDs have similar effectiveness in patients with stage IV or V CKD, compared with no CKD. The study had only 25 patients with stage IV or V disease. I have to think that there was some belief that these were good candidates and that there were a lot of other patients with severe CKD where a physician decided not to implant an ICD. Those patients are not represented in the data," Dr. Reynolds said.
Another study ran a pair of meta-analyses to explore the interactions of ICDs and CKD. In both analyses, CKD was defined as patients on dialysis, those with a creatinine clearance of less than 60 mL/kg per 1.73 m2, or patients with a serum creatinine of at least 1.5 mg/dL.
The first analysis looked at the impact of ICDs on all-cause death among CKD patients at high risk for sudden cardiac death. The literature search found five reports that addressed this issue, in a total of 17,460 patients, which showed that ICD placement linked with a statistically significant 35% cut in total mortality, compared with similar, propensity-score matched patients who did not get ICDs, Dr. Nader Makki said at the meeting.