ORLANDO, March 31 -- Early implantation of cardioverter defibrillators (ICDs) after acute myocardial infarction did not reduce overall mortality in a trial of high-risk patients, researchers here reported.
As expected the ICDs did reduce sudden cardiac death compared with optimal medical therapy (P P
Dr. Steinbeck reported results of the IRIS (Immediate Risk Stratifications Improves Survival) study here during the final, late-breaking clinical trials session of the American College of Cardiology meeting.
The trial randomized 445 patients to ICDs (415 actually received devices)
and 453 to optimal medical therapy.
Entry criteria included impairment of left ventricular function (40% or less) on day 5 to 31 following MI, plus a heart rate of more than 90 beats per minute, and/or nonsustained ventricular tachycardia at a rate of 150 bpm or faster during Holter-ECG monitoring on day 5 to 31 following MI.
Action Points
- Explain to interested patients that this study investigated an off-label use of implantable cardioverter defibrillators.
- Note that this study was published as an abstract and presented orally at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
The patients were enrolled from June 1999 through October 2007 and were followed for a mean of 37 months.
ICDs were implanted an average of 8.8 days after randomization.
Overall, the mortality rate was almost identical for patients randomized to ICD implantation within 30 days of MI and those who were randomized to optimal medical therapy -- 117 deaths in the control arm versus 116 in the ICD arm.
But the puzzling finding was the excess number of nonsudden cardiac deaths in the ICD arm.
"This may indicate that [ventricular tachycardia/ventricular fibrillation] in the early period following MI is not a cause of sudden death, but an indicator of the patient's risk of dying anyway, but death takes another door," Dr. Steinbeck said.
Or it might "a side-effect of the defibrillator -- that inappropriate shocks from the ICD might damage the heart," he said.
In any case, he said the answer won't be known until he and colleagues complete an ongoing mechanistic analysis. He would not speculate on the time frame for that.
Claudio D. Schuger, M.D., of Henry Ford Hospital, said that it was even more troubling "that these lines continue to diverge for two years and more. Nobody understands this."
Dr. Schuger, who chaired the plenary session at which IRIS results were reported, said he found the presentation by the IRIS investigators to be of little value. That's because a previous trial called DYNAMIT (Defibrillator in Acute Myocardial Infarction Trial) had already reported that early implantation did not improve survival in this population.
Current recommendations are to delay implantation for 40 days.
Timothy Gardner, M.D., president of the American Heart Association and director of the Heart and Vascular Institute at Christiana Care in Wilmington, Del., said it was clear that the findings, which he said didn't surprise him, clearly indicated that it would not be advisable to pursue expanding early ICD implantation to include this population.
| The IRIS trial was supported by Medtronic Bakken Research Center and AstraZeneca.
|
Primary Source
American College of Cardiology
Source Reference: Steinbeck G "A randomized study of the effects of defibrillation implantation early after myocardial infarction in high risk patients on optimal medical therapy" ACC 2009; Session 416.