Implanted devices that can shock a failing heart back into regular rhythm do an excellent job of keeping patients alive, two new University of Michigan studies find.
The research also suggests that doctors may be able to categorize their patients according to their individual risk factors, to determine who might get the largest benefit from the expensive devices, called implanted cardiac defibrillators, or ICDs. The studies also reinforce the importance of providing good follow-up care to all heart failure patients, whether or not they receive an implanted device.
With Medicare poised to start covering ICDs for many more patients than ever before, the new results come just in time to help doctors decide which patients might get the greatest benefit from the costly devices. More than half a million more people may qualify for ICDs, which cost around $20,000, under Medicare guidelines that will take effect soon.
The data were presented here today in two talks at the Scientific Sessions of the American Heart Association by a U-M Cardiovascular Center team that analyzed data from 7,000 veterans treated for heart trouble in Veterans Affairs hospitals between 1995 and 1999. All had congestive heart failure, heart muscle damage caused by clogged blood vessels, and a heart rhythm irregularity called ventricular arrhythmia. Of the 7,000 patients, 1,442 had received an ICD.
The researchers found that those who received an ICD were 60 percent less likely to die in the next year, and 48 percent less likely to die in three years, than those who did not receive an ICD. Most of this reduction in death risk was due to reduction in heart-related deaths. ICDs are specifically designed to prevent sudden cardiac death, in which the heart's electrical system goes haywire, causing it to stop beating.
But ICD recipients who had co-existing medical conditions, especially diabetes or kidney failure, were much more likely to die within a year of getting the device than other patients. So were patients who received an ICD, but didn't get heart-protecting medications that are part of standard heart-failure therapy.
It's the first "real world" study of the effect of ICDs on mortality rates among heart failure patients with ischemic heart disease treated outside of clinical trials, says lead researcher and U-M cardiology fellow Paul Chan, M.D.
"We need to make sure that as this technology is disseminated out of the carefully controlled environment of clinical trials and into the broader population, we assess whether the benefit seen in those trials is sustained," says Chan.
"And indeed, we see that those who received an ICD had significantly less mortality," he continues. "For every five people with heart failure and ischemic heart disease who received an ICD, one life was saved over three years. But those with certain pre-existing conditions were more likely to die within a year, despite the benefits of ICDs."
In all, 20 percent of patients who didn't receive ICDs died of heart-related causes by the end of the first year after their hospitalization, compared with 8 percent of those who received ICDs. By the end of three years, 36 percent of patients who didn't receive ICDs died of heart-related causes, as compared with 23 percent of those who did. Death rates due to non-heart causes were similar between the two groups.
Chan and his mentor, U-M internal medicine professor and VA Ann Arbor Healthcare System researcher Rodney Hayward, note that the finding of major differences in mortality benefit among different patient groups should help doctors decide which patients are less likely to die within a year of ICD implantation, and how to manage them after they've received the device.