Prophylactic implantable cardioverter-defibrillator (ICD) therapy did not reduce overall mortality among patients with acute MI and clinical features that placed them at increased risk, according to the randomized, prospective IRIS trial published Thursday in the New England Journal of Medicine.
The rate of death, including sudden cardiac death, is highest early after an MI, according to the authors. Yet, the current guidelines do not recommend the use of an ICD within 40 days after an MI for the prevention of sudden cardiac death.
Gerhard Steinbeck, MD, from Ludwig-Maximilians University in Munich, and his IRIS (Immediate Risk Stratification Improves Survival) investigators tested the hypothesis that patients at increased risk who are treated early with an ICD will live longer than those who receive optimal medical therapy alone.
The open-label, investigator-initiated, multicenter trial registered 62,944 unselected MI patients. Of this total, 898 patients were enrolled five to 31 days after the event if they met the following clinical criteria: a reduced left ventricular ejection fraction (at least less than 40 percent) and a heart rate of 90 or more beats per minute on the first available ECG, as well as rapid non-sustained ventricular tachycardia (more than 150 beats per minute).
Of the 898 patients, the researchers randomly assigned 445 to treatment with an ICD and 453 to medical therapy alone.
During a mean follow up of 37 months, 233 patients died; 116 patients in the ICD group and 117 patients in the control group. As a result, the authors deduced that “[o]verall mortality was not reduced in the ICD group.”
They also reported that there were fewer sudden cardiac deaths in the ICD group than in the control group (27 vs. 60), but the number of non-sudden cardiac deaths was higher (68 vs. 39).
While ICD implementation “significantly reduced” the rate of sudden cardiac death, those results were counterbalanced by an increase in the rate of cardiac death from others causes, according to Steinbeck and colleagues.
The authors also noted that the difficulties in conducting this study originated from “unanticipated and multifactorial improvement in outcomes” for contemporary MI patients. “After hospital discharge of patients whose MI is treated according to current guidelines, sudden cardiac death is not as great a threat as it once was,” they wrote.
The researchers concluded that the increased risk of nonsudden cardiac death after ICD implementation “deserves further study.”