ICD Therapy Proves Beneficial Regardless of Time of Implantation

According to a retrospective sub-study of the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT), there is no evidence that implantable cardioverter-defibrillator (ICD) benefit varies with time from myocardial infarction (MI) to device implantation.

Accordingly, single lead ICD benefit is not restricted to patients with a remote MI (>18 months). The study, published in the March edition of HeartRhythm, the official journal of the Heart Rhythm Society, suggests that ICD therapy post-MI decreases the chances of SCD starting immediately after the post-infarct period of 0-40 days.

In SCD-HeFT, 2,521 patients across the U.S., Canada, and New Zealand were randomly assigned to single lead, shock-only ICD therapy, amiodarone or placebo (double blind). The trial analyzed the use of ICDs in patients who experienced MI, yet had no previous life-threatening arrhythmia.

The purpose of the trial was to determine the efficacy of ICDs as a primary prevention therapy for patients with moderate heart failure. The trial found that ICD therapy significantly decreased the relative risk of mortality by 23%.

This retrospective sub-study, led by Jonathan Piccini, MD, for the SCD-HeFT investigators, analyzed the outcomes of ICD therapy in post-MI patients to determine whether mortality benefit varied as a function of time. Data from 712 patients were analyzed and divided into tertiles based on the amount of time that had passed between the patients MI and the implantation of a single-lead ICD.

Analysis revealed that patients randomized to ICD therapy (versus placebo) were less likely to experience SCD in all three groups: 6.2% versus 14.2% within the first 2.11 years, 5.8% versus 10.3% between 2.11 and 7.31 years, and 2.5% versus 17.4% over 7.31 years. A sensitivity analysis was also conducted and revealed that there was no evidence that ICD benefit varied between ICD implantation within the first 18 months or after.

“It is widely known that the risk of SCD is most common in people immediately following a heart attack, yet some evidence suggests that the benefits of ICD therapy may be restricted to those patients who are more than a year after their MI,” Piccini, of the Duke University Medical Center and Duke Clinical Research Institute, said in a statement.

“However, the SCD-HeFT results show that the benefit of single lead, conservatively programmed ICD therapy is not limited to those patients remote from a myocardial infarction. Ensuring that eligible patients receive primary prevention defibrillator therapy is likely to be more important than when the device is implanted, outside of 40 days.”

Although future, prospective trials must take place in order to determine the optimal time and programming for ICD implantation after MI, the SCD-HeFT analysis has shown there is no evidence that ICD benefit varied with time from MI to implantation.

Therefore, ICD implantation, at least as implemented in SCD-HeFT, should not be restricted to patients with remote MI (> 18 months), as previously suggested. The differences in outcome between SCD-HeFT and prior studies are not clear but the use of a simpler, more conservatively programmed ICD may be responsible.

There are also some important limitations to the SCD-HeFT analysis. Patients with MI, unstable angina, or coronary revascularization within the last 30 days were not eligible for enrollment in SCD-HeFT. Additionally, only 10% of the patients in the SCD-HeFT analysis were within six months of their most recent MI.