The finding was to be presented Thursday at the Heart Rhythm Society annual meeting, in Boston.

"This study proves that ICD therapy, sustained for over eight years, does in fact improve survival rates and ultimately save lives," study author Dr. Ilan Goldenberg, of the University of Rochester Medical Center, N.Y., said in a heart society news release.

In the study, the researchers tracked outcomes for more than 1,200 patients with ischemic left ventricular dysfunction who enrolled in the study in 2001.

After eight years of follow-up, 61 percent of patients without an ICD had died of any cause, compared to 45 percent of those with the implanted device. The 16 percent jump in survival equals an average gain in life span of 1.2 years over the eight-year period, the team said.

Long-term effectiveness of the devices was enhanced among patients who received some left ventricular pacing and among those who did not go on to develop heart failure, the researchers added.

More information

There's more on cardiac defibrillation at the American Heart Association .