Variation in Dual- vs Single-Chamber-ICD Use Highlights Missing Data

Reed Miller

April 26, 2012

April 25, 2012 (Denver, Colorado) — A new study on the use of dual- and single-chamber implantable cardioverter defibrillators (ICDs) in patients without a pacemaker indication highlights the critical need for more research on the best device for these patients, according to the study's lead investigator [1].

Dr Dan Matlock (University of Colorado Denver School of Medicine, Aurora) and colleagues conducted a cross-sectional study of hospital-level variation in the use of dual-chamber implantable defibrillators in patients without a documented pacing indication from 2005 through 2009 in the National Cardiovascular Data Registry (NCDR). Results of the study are published in the April 23, 2012 issue of the Archives of Internal Medicine. "The evidence on this has been conflicting. A lot of the trials studying ICDs use only single-lead ICDs, but there are some studies that suggest that a dual-lead ICD is better," Matlock explained to heartwire .

For example, the DATAS study showed that dual-chamber ICDs reduced clinically significant adverse events compared with single-chamber ICDs in patients with a standard ICD indication. However, the dual-chamber devices' ability to reduce inappropriate shocks remains controversial, according to Matlock et al, and recent research from the NCDR database showed that dual-chamber ICDs increase the risk of procedural complications, including in-hospital death, by over 40% compared with single-chamber ICDs.

"These were patients where the doctor had a choice of a single- or dual-lead ICD, and we found astounding variation," Matlock said. The study shows that dual-chamber ICDs were implanted in about 58% of the 87 115 patients in the study, but the rates of dual-chamber implants for the 1293 hospitals ranged from 0% at 33 centers to 100% at 109 centers.

"What jumped out as surprising is what didn't cause the variation: the patients had relatively little influence on whether or not the dual-lead was implanted," he said. The study controlled for a variety of patient factors, including atrial fibrillation, diabetes, hypertension, and the use of dialysis, and found nothing in the patient characteristics that could explain the wide variation in dual- vs single-lead implants.

"And that was a bit of a surprise. In practice-variation research in general, the common criticism is that 'it must be something about the patients.' But here, because of the rich data in the NCDR registry, we were able to look at a lot of patient variables in ways that other recent variation studies haven't been able to."

Patient characteristics did not appear to influence the decision to use a dual- vs single-chamber ICD, but geographical region and type of hospital did, with the chances of a patient getting a dual-chamber device generally increasing the further west they lived. Only 36.4% of patients in New England received a dual-chamber device, compared with 66.4% of patients in the Pacific region.

Just under half of patients treated at university hospitals were implanted with a dual-chamber device, compared with over 69% of patients at private or community hospitals (odds ratio 0.65). Also, surgeons were about twice as likely to choose a dual-chamber device as an electrophysiologist.

Variation Does Not Mean Inappropriate

"We're definitely not saying that physicians who are putting in dual leads are doing the wrong thing or that physicians putting in single leads are doing the wrong thing. That's the wrong message to take," Matlock said. "We're trying to say that we clearly need more evidence on what is the right decision for patients who don't have a clear indication for a dual-lead ICD.

"All of these physicians, when they're putting in a single or dual lead, are doing what they think is right. There's evidence pointing both ways, but the fact that it conflicts is why we're seeing this variation," he said. "We need a randomized trial of patients with single- and dual-lead ICDs, and we need better comparative-effectiveness data from large registries to generate some real-world knowledge."

In an accompanying editor's note, Dr Rita Redberg (University of San Francisco, California) is more pessimistic about the study's message. The paper by Matlock et al is included in the Archives ongoing "Less is More" series.

"Despite the absence of data to support benefit for patients receiving a dual-chamber implantable cardioverter-defibrillator compared with a single-chamber ICD for a nonpacing indication, most implants are of dual-chamber ICDs," Redberg said. "In contrast to the lack of data for benefit, there are data from multiple randomized and observational trials suggesting increased harm."

Matlock was supported by the National Institute on Aging. Disclosures for the coauthors are listed in the paper.