Incidence and outcomes of acute myocardial infarction with arrhythmic onset: A retrospective cohort study

Introduction

Patients with acute coronary syndrome (ACS) have concomitant ventricular arrhythmic events (VA). Literature data are conflicting regarding short- and long-term prognosis. International guidelines do not recommend defibrillator (ICD) implantation in the first 40 days after a myocardial infarction. However, some patients may have an increased arrhythmic risk and deserve closer monitoring.

Purpose

The aim of our study was to define the incidence of arrhythmic events in a population of patients admitted for ACS to the Cardiac Intensive Care Unit (CICU) of a tertiary center and to determine the short- and long-term prognosis in patients with arrhythmic onset compared with patients without arrhythmic onset.

Methods

This is a single-center retrospective cohort data analysis of 1587 consecutive patients admitted with a diagnosis of ACS to the CICU of Niguarda Hospital of Milan, from 2014 to 2022. We classified the patients into two groups according to the arrhythmias at presentation: VA (sustained VT or VF) and no-VA. Kaplan–Meier (KM) estimated the probability of remaining event free in the time after ACS and were compared between VA and no-VA groups, using the log-rank test. Cox regression analysis was used to explore the association of specific variables with the occurrence of cardiac events in univariate and multivariate analysis. Statistical analyses were performed with R 42.0 statistical package (R Core Team, Vienna, Austria).

Results

Among 1587 ASC patients, 4.6 % had arrhythmic onset (4.0 had a diagnosis of VF and 0.6 % of VT). Patients with VA were significantly younger (63 y. vs 67 y., p = 0.026) and had a lower incidence of cardiovascular risk factors, such as hypertension and dyslipidemia, compared with no-VA group. VA group had a higher risk of arrhythmias during the hospitalization (9.6 % vs 1.3 %, p < 0.001) and had a clinical course characterized by a significantly higher use of mechanical support with intra-aortic balloon pumps (IABP, 35.6 % vs. 6.8 %, p < 0.001) and a greater use of inotropic drugs (34 % vs. 9 %, p < 0.001). We observed in VA group a six-fold increase in-hospital mortality (23 % vs 4 %, p < 0.001), identifying arrhythmic presentation as a marker of worse in-hospital prognosis in patients admitted with ACS. Likewise, mortality at 40 days after the acute event was higher in the VA group than in the no-VA group (22 % vs. 5 %, p < 0.001). Conversely, during a median follow-up of 5.9 years, VA onset did not affect long-term mortality in patients discharged alive.

Conclusion

In this long-term follow-up retrospective registry involving a large cohort of patients with ACS admitted to the CICU, concomitant VA at admission was found to be linked with an increase in in-hospital arrhythmic complications and in-hospital mortality. The mortality rate at 40 days post-ACS was also notably higher in the VA group. This study underscores the complexity of arrhythmic presentation in ACS patients, emphasizing the critical need for vigilant monitoring throughout their hospitalization and particularly in the initial 6 weeks following the event index. This heightened surveillance is justified by the documented elevated levels of morbidity and mortality during this phase.