Patients receiving an implantable cardioverter–defibrillator (ICD) for primary prevention of sudden cardiac death with no indication for pacing are better off with a single-chamber than a dual-chamber device 1 year after implantation, according to Pamela Peterson and colleagues. In their report published in JAMA, data from 32,034 patients from the National Cardiovascular Data Registry's ICD registry in the USA were retrospectively analysed for associations between ICD type and mortality at 1 year, readmission to hospital for any cause or for heart failure, and device-related complications within 90 days.

“This study was prompted by several observations,” says Peterson. “First, many people (up to two-thirds) with left ventricular systolic dysfunction who receive an ICD for primary prevention and do not have a pacing indication are treated with dual-chamber devices. Second, marked geographic variation in the use of dual-chamber ICDs exists that is unrelated to patient characteristics. Third, there is little evidence to support this practice, and guidelines are not explicit regarding the type of device that should be used in this context.”

Data were analysed according to both overall and propensity-matched cohorts. In each analysis, device type was not associated with either 1-year mortality or hospitalization for any cause. Admission for heart failure was lower for patients receiving a single-chamber than a dual-chamber ICD in the overall cohort (14.72% vs 15.54%; P = 0.047), but this difference was not observed in the propensity-matched cohort.

The use of a dual-chamber compared with a single-chamber device was, however, associated with an increased risk of device-related complications in both the overall and propensity-matched cohorts (4.76% vs 3.53% and 4.72% vs 3.51%, respectively; P <0.001 for each). Implantation of dual-chamber ICDs is more complex and has a longer procedural time than implantation of single-chamber ICDs. Complications included pneumothorax requiring a chest tube at 30 days; haematoma requiring blood transfusion or evacuation at 30 days; cardiac tamponade at 30 days; mechanical complications requiring reoperation for system, generator, or lead revision at 90 days; device-related infection at 90 days; and recurrent ICD implantation at 90 days. The largest absolute difference among these complications was for mechanical complications requiring repeat operation for system revision (1.43% vs 1.98% for single-chamber and dual-chamber ICDs, respectively, in the propensity-matched cohort; P = 0.001).

Credit: NPG

Physicians in this study implanted a dual-chamber device in 62% of patients without an indication for pacing. This preference for dual-chamber devices could be related to physician perceptions about long-term outcomes. Initially implanting a dual-chamber device could be preferable in patients whose disease progresses so as to require an upgrade from a single-chamber ICD to a dual-chamber ICD. In the JAMA paper, Peterson et al. highlight that, for this approach to be the least costly, the rate of upgrades would have to be 10%, nearly double the rate observed in clinical trials.

“It remains unclear whether dual-chamber devices result in less need for device revision or lower rates of ICD therapies over time,” says Peterson. “Future studies are needed to determine whether the increased complications associated with dual-chamber devices are offset by a reduction in inappropriate therapies or a reduction in need for device revision.”