Implantable-cardioverter-defibrillator after ST-elevation myocardial infarction: when and how frequently is it implanted and what is the rate of appropriate interventions? Insight from Trieste registry

Background: There are limited data on implantable-cardioverter-defibrillator (ICD) implantation after ST-elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (pPCI). Therefore, we evaluated when and how frequently an ICD is implanted after pPCI, the rate of appropriate ICD interventions, and predictors of ICD implantation. Methods: We analyzed STEMI patients treated with pPCI at the University Hospital of Trieste, Italy, between January 2010 and December 2019. We cross-matched patients' data with those present in the Trieste ICD registry. Results: Among 1805 consecutive patients treated with pPCI, 3.6% underwent ICD implantation during a median follow-up of 6.7 [interquartile range (IQR) 4.3-9.2] years. At 12 months, the mean number of ICD implantations was 2.3/100 patients [95% confidence interval (95% CI) 1.7-3.1] and remained stable over time (at 24 months: 2.5/100 patients, 95% CI 2.0-3.5 and at 36 months: 2.6/100 patients, 95% CI 2.3-3.8); 83.1% of ICDs were implanted for primary prevention, and more than half (55%) were implanted in patients with ejection fraction more than 35% at the moment of STEMI discharge. The rate of appropriate ICD interventions was 16.9% at a median follow-up of 5.7 years (IQR 3.3-8.3 years) after ICD implantation. At 12 months, the mean number of appropriate ICD interventions was 5/100 patients and 7/100 patients after 24 months. In patients with ejection fraction more than 35% at STEMI discharge (median ejection fraction 43%; IQR 40-48), independent predictors of ICD implantation were male sex, anterior STEMI and troponin peak more than 100 000 ng/dl. Conclusion: The rate of ICD implantations after pPCI is low; however, the rate of appropriate ICD interventions is high. A relevant subgroup of patients received ICD implantations at follow-up despite a nonsevere ejection fraction at discharge after STEMI. Among these patients, those with high troponin release deserve strict follow-up and full optimal medical treatment.