Implantable cardioverter defibrillators did not improve mortality in selected heart-attack patients with abnormal heart rhythm markers

Key take-aways

• Implantable cardioverter defibrillator (ICD) therapy is used in patients with severe left ventricular systolic dysfunction.
• The REFINE-ICD trial investigated whether an ICD could improve survival in patients with a prior myocardial infarction, persistent moderate left ventricular systolic dysfunction and abnormal ambulatory ECG markers.
• While the presence of abnormal ECG markers was associated with a higher rate of death, survival was not improved with ICDs compared with medical therapy alone.
• Further research efforts are needed to better manage these post-MI patients.

Madrid, Spain - 30 August 2025: Prophylactic implantable cardioverter defibrillator therapy did not reduce mortality in patients with a prior myocardial infarction, persistent moderate left ventricular systolic dysfunction and abnormal ECG markers, according to late-breaking research presented in a Hot Line session today at ESC Congress 2025.¹

An implantable cardioverter defibrillator (ICD) is a small electrical device fitted in the chest that detects irregular and fast heart rhythms. ICD therapy is used in patients with a prior cardiac arrest or severely impaired left ventricle (LV) pumping ability (severe LV systolic dysfunction).

Principal Investigator, Professor Derek Exner from the Libin Cardiovascular Institute, Calgary, Canada, explained why the REFINE-ICD trial was conducted: "From earlier studies we knew that the risk of death was high after a myocardial infarction (MI), notably among patients with persistent, moderate LV systolic dysfunction and ECG markers associated with ventricular arrhythmia risk. We tested the hypothesis that an ICD may help these patients live longer than those who receive optimal medical therapy alone."

The open-label, investigator-initiated REFINE-ICD trial was conducted in Canada, USA, Europe, Middle East and Africa. In total, nearly 2,000 patients with a prior MI (≥2 months) underwent ambulatory ECG testing to assess two markers of ventricular arrhythmia risk: heart rate turbulence and T wave alternans. Of these, 597 patients with LVEF 36−50%, impaired heart rate turbulence and abnormal T wave alternans were randomised to an ICD added to medical therapy or medical therapy alone.

The mean age of the patients was 65 years and 19% were women. Overall mortality was higher in patients with both abnormal ECG markers compared with those without (hazard ratio [HR] 2.59; 95% confidence interval [CI] 1.97 to 3.40; p<0.001).

During mean follow-up of around 5.7 years in randomised patients with abnormal ECG markers, total mortality was not reduced with ICDs: 24.5% of patients died in the ICD group and 21.3% died in the control group (HR 1.07; 95% CI 0.77 to 1.50; p=0.69). Almost half of deaths (47.4%) were adjudicated as non-cardiac deaths. Cardiac mortality was not reduced in the ICD group vs. controls (8.8% vs. 7.6%, respectively; HR 1.11; 95% CI 0.63 to 1.945). Sudden cardiac death occurred in 2.6% of patients in the ICD group and 3.8% in the control group (HR 0.66; 95% CI 0.27 to 1.62).

Summing up, Professor Exner said: "In this trial, patients with a prior MI, persistent moderate LV systolic dysfunction and ECG markers of ventricular arrhythmia risk had twice the incidence of death as similar patients without these risk markers. Although overall, the risk of death was lower than expected and half of all deaths were non-cardiac. Importantly, ICD therapy did not reduce total mortality, cardiac death and sudden cardiac death. Further research efforts are needed to better manage these patients."

ENDS