Sometimes, more is not better, as researchers report in a new study of implantable defibrillators, devices that use electrical shocks to prevent sudden cardiac arrest in people with potentially life-threatening heart arrhythmias. In research published today in JAMA, investigators found that implantation of newer “dual-chamber” implantable cardioverter-defibrillators (ICDs) is associated with a higher risk of device-related complications when compared with single-chamber ICDs. At the same time, rates of hospitalization or death among patients during the first year after implantation were the same regardless of whether patients received a single- or dual-chamber device.
In theory, compared with single-chamber devices, dual-chamber ICDs produce electrograms that are easier for physicians to interpret, and these devices are better able to identify dangerous arrhythmias, reducing unnecessary electrical shocks. But dual-chamber ICDs are more difficult to implant and may be associated with more infections and displacement of wires, or leads, requiring reoperations.
For the JAMA article, researchers retrospectively studied 32 034 patients who received a single-chamber or dual-chamber device for primary prevention (to prevent sudden cardiac arrest in people who are at high risk for this problem) from 2006 to 2009. Complication rates were 3.51% for single-chamber devices compared with 4.72% for dual-chamber devices. Rates of 1-year mortality, as well as 1-year all-cause hospitalization or hospitalization for heart failure, were similar. The increased complication rate without an apparent increase in benefit led the researchers to ask why almost two-thirds of all ICDs implanted in this population for primary prevention were dual-chamber devices.
Lead author Pamela N. Peterson, MD, MSPH, an associate professor of medicine at the Denver Health Medical Center in Colorado, discusses her team’s findings:
news@JAMA: What prompted you to study single-chamber versus dual-chamber ICD use for primary prevention?
Dr Peterson: We had several reasons. First, the major trials that looked at primary prevention with ICDs predominately tested single-chamber devices, and when dual chambers came out, there was little study of their effects for primary prevention. Second, with the introduction of dual-chamber ICDs, we saw practice pattern changes, with a significant number of patients receiving them. Third, we also saw great geographical variation in the use of single- or dual-chamber ICDs that was not associated with patient characteristics.
news@JAMA: You compared the devices in terms of primary prevention of life-threatening arrhythmias. What are the characteristics of a patient that would suggest implanting an ICD for primary prevention?
Dr Peterson: They can be patients who have a reduced ejection fraction: their heart function is weak. Also, those at high risk for these irregular heart rhythms, who are at risk for sudden cardiac arrest.
news@JAMA: Why have clinicians turned to implanting dual-chamber ICDs for the primary prevention of dangerous arrhythmias?
Dr Peterson: As technology advances, it is hard to believe the advanced technology is not better than the prior technology. One theoretical benefit of the dual chamber is that it is better able to detect and differentiate a lethal from nonlethal arrhythmia, but the data have yet to show that. Also, the culture of practice is a significant player in this geographic variation we observed. It becomes a “this is the way we do it here” culture.
news@JAMA: What issues do patients discuss with clinicians when they are being considered for an ICD?
Dr Peterson: The decision whether to receive a device at all is the most important decision, and there aren’t great data to support one device over the other. Once it’s decided that a patient needs a device, the choice of single chamber or dual chamber often doesn’t involve the patient. It’s often a physician-level decision.