BOSTON--In heart attack survivors who received implanted cardioverter defibrillators (ICDs), mortality benfit was sustained over eight years of follow up, according to the results of late-breaking clinical trial presented May 14 at the 30th annual scientific sessions of the Heart Rhythm Society (HRS).
The study that first tested the effectiveness of ICDs, the 2002 MADIT II (Multicenter Automatic Defibrillator Implantation Trial II), changed medical U.S. guidelines, and made thousands of MI survivors eligible for ICD therapy. MADIT II enrolled 1,232 patients with ischemic left ventricular dysfunction who were followed up through November 2001.
Led by Arthur Moss, MD, professor of medicine at the University of Rochester Medical Center in Rochester, N.Y., the study found that the devices reduced the risk of sudden cardiac death by 31 percent in MI survivors. At the same time, the ICD therapy could extend the average patient's life by about two months over a follow-up period that averaged about two years per patient. While that survival benefit was meaningful to patients, some critics argued that it did not make sense for the healthcare system to pay $25,000 for a device that provided a modest extension of life in patients with chronic cardiac disease.
However, the current study watched the same patients for eight years, and found that patients with ICDs lived an average of more than a year longer, "greatly amplifying" the value of the treatment and arguing that it is dramatically more cost effective as a chronic therapy, according to the new study's lead author Ilan Goldenberg, MD, research associate professor within the Heart Research Follow-up Program at the University of Rochester, who presented the findings at HRS.
For the current long-term efficacy study, Goldenberg and colleagues acquired post-trial mortality data from the U.S. (through December 2006) and European (through March 2009) National Death Registries. At eight years of follow up, the researchers found that MADIT II patients who had an ICD for eight years had a 37 percent lower chance of death from any cause than those without one, which translates into 1.2 life-years saved.
"These results show that ICDs extend the long-term survival of patients with life-threatening heart conditions," Goldenberg said. "These results emphasize the life-saving value of ICDs as chronic therapy for high-risk cardiac patients."
When outcome was assessed separately during the early and late phases of the follow-up period, the researchers said that ICD therapy was shown to be associated with a significant survival benefit during the first four years after enrollment; and with additional life-saving benefit during the extended four to eight year follow-up period.
Goldenberg reported that post-trial ICD efficacy was shown to be influenced by heart failure (HF) status at trial closure: patients who did not experience symptomatic HF during the trial derived a pronounced survival benefit from the ICD after trial closure, whereas post-trial ICD efficacy was significantly attenuated among patients who developed symptomatic HF during the study.
Furthermore, device-pacing programming was shown to affect long-term outcome with an ICD: patients who received dual-chamber devices during the trial (set to pacing rate at DDD-60 to 70) experienced an increase in mortality rate during the late phase of the extended follow-up period, and accordingly did not derive a significant benefit from the ICD during the post-trial period, whereas patients who received single-chamber devices (set to back-up pacing rate at VVI-40 to 50) derived enhanced benefit from the ICD during the post-trial period.
Goldenberg concluded that long-term device efficacy was enhanced among patients who received a limited amount of right ventricular pacing from the ICD, and among those who did not develop HF progression during the study. He also noted that he and his colleagues are now following up with the data compiled from MADIT II with subgroup analyses, including gender differences.