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Defibrillators Fight Long-term Post-Myocardial Infarction Mortality Risk: Presented at NASPE

By Peggy Peck

WASHINGTON, DC -- May 20, 2003 -- Implantable cardioverter-defibrillators (ICDs) can help reduce the risk of mortality and sudden death after a myocardial infarction (MI).

The total risk for mortality and sudden death increases over time -- for as long as 15 years post-MI.

These findings, from a new analysis of data collected by the Multicenter Automatic Defibrillator Implantation Trial II (MADIT-II), were presented here on May 16^th at the 24^th Annual Scientific Sessions of the North American Society of Pacing and Electrophysiology.

David J. Wilber, MD, a George M. Eisenberg Professor of Cardiovascular Sciences Medicine, Loyola University Health System, in Maywood, Illinois, noted that, based on the MADIT-II trial (1997-2001), "good evidence-based medicine supports the aggressive use of prophylactic [ICDs] in the very late phase of MI-associated ejection fractions under 30%."

In this analysis of MADIT-II data, Dr. Wilber and his colleagues examined the time-dependence of mortality risk and ICD benefit in MADIT-II patients. Time from last MI was unavailable in 73 of the 1,232 participants, but the remaining 1,159 patients were enrolled at least 1 month after MI (mean 81 months).

They randomised 699 patients to an ICD and 460 to a control group that received conventional best medical care. Additional therapy included angiotensin-converting enzyme (ACE)-inhibitor therapy in 72% of patients, beta blockers in 71%, and at least one revascularisation procedure in 77%.

Overall, after a mean follow-up of 20 months, mortality was 19.8% with the control group, and 14.2% with an ICD -- a 31% reduction in mortality.

When the researchers examined mortality by time from last MI in both treatment groups and divided into quartiles, they found a trend toward increased mortality as a function of time from MI (P=0.11) in control patients.

"This means the benefit from ICDs actually increases over time," said Dr. Wilber "It makes the case for implanting ICDs even if the MI is remote." The hazard ratio for overall mortality benefit (ICD:controls) in the shortest duration post MI quartile (1-17 months) was 1.08 (P=0.81), while the hazard ratio for the remaining three quartiles (>18 months) was 0.56 (P<0.001).

Explaining the rationale for the new analysis, Dr. Wilber noted that earlier studies of MI survival, especially those conducted in the 1970s and 1980s, found the early mortality burden to be significant, but "advances in treatment have significantly altered that picture," he noted. "With early revascularisation and better pharmacological therapy, there have been significant improvements in the survival of MI patients with low ejection fractions." Those advances, he said, have changed the epidemiology of post MI risk.


[Study title: Time-dependence of Mortality Risk and Defibrillator Benefit Following Myocardial Infarction: Lessons from the Multicenter Automatic Defibrillator Implantation Trial II. Abstract 130]

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