Nearly 80 percent of older adults who received an implantable cardioverter-defibrillator (ICD) survived at least two years, according to a registry analysis of Medicare beneficiaries.

A multivariable analysis found that the risk of death at two years increased significantly with age. All of the adults received an ICD for secondary prevention of sudden cardiac death.

Lead researcher Frederick Masoudi, MD, MSPH, of the University of Colorado Anschutz Medical Campus, and colleagues published their results online Jan. 16 in the Journal of the American College of Cardiology.

The researchers evaluated 12,420 adults who enrolled in the National Cardiovascular Data Registry ICD registry between 2006 and 2009 after receiving an ICD for secondary prevention.

CMS requires all Medicare beneficiaries receiving an ICD for primary prevention to enroll in the registry, but it does not have the same requirement for adults receiving an ICD for secondary prevention. Still, 91 percent of hospitals submitted data on patients receiving an ICD for secondary prevention.

The patients in this analysis also had a prior episode of sudden cardiac arrest, which the researchers defined as tachycardic arrest, sustained, monomorphic ventricular tachycardia or sustained polymorphic ventricular tachycardia. They received single-chamber, dual-chamber or cardiac resynchronization therapy-defibrillator devices.

The mean age was 75 years old, while 90.9 percent of patients were white, 75.1 percent had ischemic heart disease and 40.5 percent had a left ventricular ejection fraction of greater than 35 percent.

Electrophysiologists performed 68.6 percent of the ICD implantations, while 86.2 percent of the implantations were performed in a private or community hospital and 55.3 percent of the implantations were performed at teaching hospitals.

At 30 days, 2.3 percent of patients had died, which ranged from 1.5 percent in the youngest group (65 to 69 years old) to 3 percent in the oldest group (80 years old or older).

At one year, 14.3 percent of patients had died, which ranged from 9.9 percent in the youngest group to 18.9 percent in the oldest group.

At two years, 21.8 percent of patients had died, which ranged from 14.7 percent in the youngest group to 28.9 percent in the oldest group.

“In this population, there is a very high risk for these cardiac events to happen again,” Masoudi said in a news release. “I was surprised to see the survival rates in our study were as high as they were.”

The all-cause hospitalization rates were 16.2 percent within 30 days of ICD implantation (range of 14.6 percent in the youngest group to 18.5 percent in the oldest group); 52.6 percent within one year of ICD implantation (range of 48.2 percent to 57.9 percent); and 65.4 percent within two years of ICD implantation (range of 60.5 percent to 71.5 percent).

The heart failure hospitalization rates were 3.1 percent within 30 days (range of 2.4 percent to 3.6 percent); 14 percent within one year (range of 10.9 percent to 17.2 percent); and 18.8 percent within two years (range of 14.7 percent to 23.5 percent).

In addition, 8.8 percent of patients were admitted to skilled nursing facilities within 30 days, 17.3 percent were admitted within one year and 21.6 percent were admitted within two years.

After adjusting for several factors, adults who were at least 80 years old had twice the risk for death and admission to a skilled nursing facility and significantly higher risk of all-cause and heart failure hospitalizations compared with those who were 65 to 69 years old.

The study had a few limitations, according to the researchers, including that it did not include have a comparison group of patients who did not receive an ICD. Thus, they said they could not make inferences about the effectiveness of ICD therapy. They also did not collect patient-reported health status outcomes and functional status, and they did not have device therapy data.