Single-chamber ICDs better when pacing isn't required



Among patients receiving an implantable cardioverter-defibrillator for primary prevention who don’t have indications for pacing, the use of a dual-chamber rather than a single-chamber ICD doesn’t appear to confer any advantage, according to a report in the May 15 issue of JAMA.

In a nationwide retrospective cohort study involving over 32,000 such patients, there was no significant difference between patients who received single-chamber devices and those who received dual-chamber devices in 1-year mortality, rate of hospitalization for any cause, or rate of hospitalization for heart failure, said Dr. Pamela N. Peterson of the Denver Health Medical Center, and her associates.

However, there was an important disadvantage with the dual-chamber ICDs: They carried a higher rate of complications such as infection and lead displacement. They also were more costly than were single-chamber devices because placement is more complex, and time-consuming and later mechanical dysfunction is more common.

"Therefore, among patients without clear pacing indications, the decision to implant a dual-chamber ICD for primary prevention should be considered carefully," Dr. Peterson and her colleagues said.

They performed this cohort study because of the "lack of clarity" regarding the long-term safety and outcomes of dual-chamber ICDs compared with single-chamber ICDs. "Despite the absence of compelling evidence to support these more costly devices ... current practice is highly variable," they noted.

The investigators used data from the National Cardiovascular Data Registry’s ICD component to identify 32,034 patients who received ICDs at 1,270 hospitals across the country during 2006-2009. A total of 19,788 (62%) received a dual-chamber device and 12,246 (38%) a single-chamber device.

All of these study subjects received the ICDs for primary prevention only, and none had any indications for pacing.

The initial data analysis examined rates of any serious complications, including pneumothorax requiring a chest tube (within 30 days of the placement), hematoma requiring a blood transfusion or evacuation (within 30 days), cardiac tamponade (within 30 days), lead revision (within 90 days), device-related infection (within 90 days), and recurrent ICD implantation (within 90 days).

The unadjusted rate of any such complications were significantly higher with dual-chamber ICDs. The largest difference between single- and dual-chamber devices occurred with the most common complication in this study: mechanical dysfunction of the ICD requiring repeat operation for system revision.

At 1 year, the unadjusted rates of hospitalization for heart failure (14.7% vs 15.5%), of hospitalization for all causes (43.8% vs. 44.9%), and of mortality (9.9% vs. 10.1%) were similar between patients who received a single-chamber device and those who received a dual-chamber device.

The investigators then performed a propensity-matched analysis involving 11,619 patients who received a single-chamber and the same number who received a dual-chamber ICD. In this analysis, the rate of serious complications also was significantly lower with single-chamber devices (3.5%) than with dual-chamber devices (4.7%), with the largest absolute difference again occurring in mechanical complications requiring system revision.

Again, rates of all-cause hospitalization, heart failure hospitalization, and mortality were comparable between the two study groups at 1 year, the investigators said (JAMA 2013;309:2025-34).

The results remained consistent in further analyses of clinically important subgroups of patients, regardless of age, sex, or the presence or absence of renal dysfunction at the time of operation.

These findings indicate that dual-chamber ICDs "do not appear to offer any clinical benefit" over single-chamber ICDs, at least with regard to death or hospital readmission, Dr. Peterson and her associates said.

Their study was limited in that it could not address other important outcomes, such as patients’ quality of life or the development of atrial fibrillation, because no data were available regarding these factors.

This study was supported by the Agency for Healthcare Research and Quality and the American College of Cardiology Foundation’s National Cardiovascular Data Registry. Dr. Peterson reported no financial conflicts of interest; one of her associates reported receiving grant money from Boston Scientific.

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