Survival rates increase with more activity in patients with ICDs and CRT devices

Patients with implantable cardioverter-defibrillators (ICDs) or cardiac resynchronization therapy (CRT) devices who were most active had improved health outcomes and were more likely to survive, according to a registry analysis.

Researchers broke the patients into five groups based on their activity level, which was captured automatically in the ICD and CRT devices. After a year, the survival rate was 98.7 percent in the most active group and 86.5 percent in the least active group. After four years, the survival rates were 90.5 percent and 50 percent, respectively.

Lead researcher Daniel B. Kramer, MD, MPH, of Beth Israel Deaconness Medical Center in Boston, and colleagues published their findings online in the Journal of the American Heart Association on May 15.

They evaluated data from the Altitude registry, which Boston Scientific established in 2008 to track information from its ICD and CRT devices through the Latitude clinical remote monitoring system. The FDA approved the Latitude system in 2005.

The trial, which was funded by Boston Scientific, included 98,437 patients enrolled in the Altitude registry who received new or replacement ICD or CRT devices from Jan. 1, 2008 to Dec. 31, 2012. The mean age was 67.7, and 71.7 percent of patients were male. Of the patients, 56.6 percent received an ICD and 43.4 percent received a CRT device.

The mean activity level from 30 to 60 days after implantation was 107.5 minutes per day. Activity ranged from 32.5 minutes per day in the least active group to 207.7 minutes per day in the most active group. Patients in the least active group were more likely to be older and female and were more likely to receive a CRT device compared with the most active group.

The survival rate for the entire cohort was 95 percent after a year and 76.1 percent after four years. After adjusting for several variables such as age, gender and device, Kramer et al found that a lower mean baseline activity was independently associated with a higher risk of death.

They mentioned a few study limitations, including that the activity measurements from the ICDs have not been validated against other accepted measurements. The trial also did not include clinical covariates or the cause of deaths.