This retrospective cohort study included 268 consecutive patients diagnosed with ACS (unstable angina, NSTEMI, or STEMI) who underwent CMR during hospitalization between January 2020 and December 2022 at the National Institute of Cardiology Ignacio Chavez. The inclusion criteria were confirmed diagnosis of ACS based on clinical presentation, electrocardiography (ECG), and troponin levels, and additionally availability of CMR data. Echocardiographic parameters were recorded only for the patients who had undergone transthoracic echocardiography as part of their clinical evaluation. Patients with congenital heart disease, severe valvular disease, or prior myocardial infarction were excluded. The authors confirm that patient consent is not applicable to this article. This is a retrospective study using deidentified data; therefore, the IRB did not require consent from the patient.

RV dysfunction was defined as a RV ejection fraction (RVEF) <50%, measured using CMR, following standard guidelines for the quantification of ventricular volumes and ejection fraction. Although other studies define moderate or severe RV dysfunction at lower cut-offs (<40%–45%), we chose 50% as a conservative threshold to enhance sensitivity for detecting early or mild RV impairment in the ACS setting.

Clinical, cardiac magnetic resonance imaging, and echocardiographic data were collected from electronic medical records.

Clinical follow-up was conducted for up to 2 years after the index ACS event. Follow-up data were obtained from electronic medical records and outpatient clinic visits. The primary follow-up endpoints included all-cause mortality, incident heart failure, and stroke. Incident heart failure was defined as the new clinical diagnosis of heart failure documented during hospitalization or follow-up, based on symptoms, physical examination, and objective evidence of structural or functional cardiac abnormality consistent with current ESC guidelines, irrespective of ejection fraction category. Follow-up was censored at the date of the last available clinical evaluation or documentation of an event.

All statistical procedures were prospectively defined and performed with R software (version 4.4.1; R Foundation for Statistical Computing). Statistical significance was set at a 2-sided p < 0.05; corresponding 95 % confidence intervals (CI) are reported where appropriate.

Patients were stratified according to RV systolic function on cardiovascular magnetic resonance imaging CMR, with RV dysfunction defined as a right-ventricular ejection fraction (RVEF) < 50 %. Distributions of continuous variables were examined with the Shapiro–Wilk test. Because not all variables met the assumption of normality, continuous data are presented as median and interquartile range (IQR) and compared between groups with the Wilcoxon rank-sum (Mann–Whitney U ) test. Categorical variables are expressed as number (percentage) and compared with Pearson’s χ² test; Fisher’s exact test was substituted when any expected cell count was < 5. The same analytic framework was applied to the echocardiographic subcohort (160/268 patients with complete studies).

To identify variables independently associated with RV dysfunction, we fitted a logistic-regression model. Candidate covariates comprised all variables exhibiting p < 0.10 on univariable testing together with clinically important factors specified a priori, including demographics (age, sex, BMI), cardiovascular risk factors (hypertension, diabetes, dyslipidemia, smoking), measures of ACS severity (Killip–Kimball class, GRACE, TIMI scores), in‐hospital complications (ventricular septal defect, mitral regurgitation, ventricular rupture, pericardial effusion), and CMR metrics (LVEF, EDV, ESV). Backward stepwise elimination was applied with a retention threshold of p < 0.05. Collinearity was assessed by variance-inflation factors (VIF); values > 3 prompted removal of the redundant covariate. Model calibration was examined with the Hosmer–Lemeshow goodness-of-fit test. Results are reported as odds ratios (OR) with 95% CI.

All-cause mortality, incident heart failure, and stroke were evaluated as dichotomous outcomes during the prespecified follow-up period. Owing to the low event rates and absence of precise event-time data, only crude incidences were compared between RV-dysfunction strata using χ² or Fisher’s exact tests, without construction of time-to-event models.