Results of the DAPA trial, published in Circulation: Arrhythmia and Electrophysiology, demonstrated that the use of early prophylactic implantable cardioverter defibrillator (ICD) in high-risk post-primary percutaneous coronary intervention (PCI) patients was associated with lower all-cause and cardiac mortality rates. However, the results of this trial should be interpreted with caution, since the trial was stopped prematurely.
The optimal timing of ICD implantation in STEMI patients treated with primary angioplasty is not identified yet. Previous clinical trials have failed to show the benefit of early ICD implantation (4-60 days) in post-MI patients with a low left ventricular ejection fraction (≤35-40%). The risk of sudden cardiac death (SCD) is high within the post STEMI period. However, ICD implantation after 40 days may not be indicated due to left ventricular remodeling and a potential increase in LVEF post-primary PCI. The Defibrillator After Primary Angioplasty (DAPA) trial evaluated all-cause and cardiac mortality of patients undergoing early prophylactic ICD implantation after PCI for STEMI. Following a recommendation from the data safety board, the trial was terminated early after just 38% of the planned sample size was enrolled due to slow enrollment.
This multicenter, randomized, controlled trial included patients with STEMI who had undergone primary PCI and met at least one of the following criteria: LVEF<30% within 4 days after admission, primary ventricular fibrillation (VF) within 24 hours (during PCI excluded), signs of heart failure on admission (Killip class ≥ 2), and/or thrombolysis in myocardial infarction (TIMI) flow post PCI < 3. The participants were randomized in a 1:1 ratio to receive either ICD implantation or conventional therapy within 30 to 60 days of the STEMI event. The primary endpoint was all-cause mortality at 3 and 9-years. The secondary endpoints of the study included the incidence of sudden cardiac death (SCD) and hospital admission for sustained ventricular tachyarrhythmias or appropriate ICD therapy.
A total of 266 patients with primary PCI for STEMI were included in the study with 131 patients allocated to the ICD arm and 135 patients assigned to the conventional therapy arm. After 3-years of follow-up, the primary outcome of interest was significantly lower among patients who received ICD implantation (5%) compared to the conventional therapy group (13%) (Hazard ratio (HR):0.37; [95% CI: 0.15-0.95]; p=0.04). This result remained similar at a median of 9-years follow-up (HR: 0.58; [95% CI: 0.37-0.91]; p=0.02). In terms of cardiac mortality, ICD implantation was associated with fewer deaths (11%) compared to the control group (22%) (HR: 0.52; [95% CI: 0.28-0.99]; p=0.04). Although not statistically significant, the incidence of SCD was also lower in the ICD group (3.1%) compared to the control group (5.9%) (HR 0.45; [95% CI 0.14–1.50]; p=0.19).
The results of this study should be interpreted with consideration of the following limitations. First, the premature termination of the study makes it underpowered for analysis. Second, the study used more than one inclusion criteria, so results should be interpreted with consideration of the patient characteristics. The high treatment crossovers (10.2%) within the first 3 years of the study and the lack of information on treatment crossovers between 3 and 9 years are additional limitations of the trial. Furthermore, while pharmacotherapy of the participants was similar at baseline, there is a lack of data regarding the follow-up medical therapy which may have impacted the mortality rates.
In conclusion, this prematurely terminated trial suggests that early prophylactic ICD implantation may be associated with a better survival rate in patients at high risk of death after primary PCI for STEMI. The results of this trial should be confirmed in future studies.