ICD implantation reduces mortality in heart attack patients

Findings from the latest PreSCD II analysis show that patients protected against sudden cardiac death by an implantable cardioverter defibrillator (ICD) one month or more after MI showed a non-significantRemarkably," says investigator Professor Heinz Völler from the Klinik am See in Ruedersdorf, Germany, "we observed in the data a survival benefit that increased with the time interval between MI and ICD implantation."

Based on the MADIT II trial results, ejection fraction is predominantly used for risk stratification in MI patients to determine implantation of an ICD. The PreSCD II analysis was thus stratified according to patients who presented with a severely reduced ejection fraction (≤30%), a moderately impaired (31-40%) or normal heart function. "We were surprised that in the high risk group of patients with severely reduced heart function, which comprised only 2.5% of the registry population, only 22% of them were protected by an ICD as primary prevention of sudden cardiac death," said Professor Völler.

Between December 2002 and May 2005 the PreSCD II registry enrolled 10,612 MI survivors in 19 rehabilitation centres in Germany. Left ventricular function was determined in all patients one month or later after the index infarction, thus evaluating the risk for sudden cardiac death. All patients with a reduced ejection fraction of ≤40% plus a random sub-sample of the patients with preserved EF (n = 2058) were observed for at least 36 months for clinical events and mortality.

Commenting on the results, Professor Völler said: "Patients who survive myocardial infarction have an increased risk for sudden cardiac death. Randomised controlled trials like MADIT II and SCD-HeFT showed that patients with impaired left ventricular function are particularly protected against sudden cardiac death by an implantable defibrillator. All-cause mortality was morreduced up to 31% by the ICD. However, in these trials the ICD was predominantly implanted several months after acute Mi. Other trials like DINAMIT and IRIS failed to demonstrate an ICD benefit if implanted early after myocardial infarction. International guidelines on anti-arrhythmic therapy reflect these results.

"The PreSCD II registry has confirmed the findings of the randomised clinical trials in a real life environment, where ICD implantation rates were lower than suggested by study results and guidelines. Noteworthy in this registry was an increasing reduction of mortality over time, depending on the time interval between index infarction and ICD implantation. However, when interpreting the data, it should be remembered that registry analyses do not in general have the confirmative power of a randomised controlled trial with causal connections."