P1475Risk stratification after STEMI. Ejection fraction by echocardiography as the gatekeeper for a selective use of cardiac magnetic resonance
Authors: Marcos Garces V , Gonzalez J , Gavara J , Rios-Navarro C , Bonanad C , Chorro F J , Ortiz J T , Rodriguez J , Mendieta G , Rodriguez-Palomares J F , Valente F , Garcia-Dorado D , Lopez-Lereu M P , Monmeneu J V , Bodi V 
Published: October 2019

Abstract

Introduction
Cardiac magnetic resonance (CMR) has emerged as the most potent non-invasive imaging technique for risk stratification after ST-segment elevation myocardial infarction (STEMI) but an indiscriminate use in all patients is unfeasible. Echocardiography (Echo) has been universally used for prognostication in this scenario. We hypothesized that left ventricular ejection fraction (LVEF) by Echo can represent the gatekeeper for selecting those patients who benefit most from CMR for prognostic purposes.

Methods
Data were obtained from a large prospective registry of reperfused STEMI patients (n=516) in whom Echo (2D and Doppler variables) and CMR (cine images, microvascular obstruction and infarct size) were simultaneously recorded at pre-discharge (7±2 days). Major adverse cardiac events (MACE) were defined as a combined clinical end-point: death or re-admission for acute heart failure (whichever occurred first). Patients were categorized in reduced LVEF (r-LVEF, <40%), mid-range LVEF (mr-LVEF, 40–49%) and preserved LVEF (p-LVEF, ≥50%). Hierarchical multivariate Cox regression analyses including first clinical+Echo variables and then CMR variables where carried out. C-statistics, “net reclassification” (NRI) and “integrated discrimination” (IDI) indexes were obtained.

Results
During a mean and median follow-up of 4 years, 86 first MACE (17%) were registered (39 deaths and 47 re-admissions for acute heart failure). In the whole study group (n=516), the independent predictors of MACE were time to revascularization (min), GRACE score, CMR-LVEF (%) and CMR-microvascular obstruction (% of LV mass); C-statistic 0.82 (p<0.001). The MACE rate in patients with r-LVEF, mr-LVEF and p-LVEF was 47%, 23% and 11% by Echo-LVEF and 45%, 17% and 8% by CMR-LVEF. LVEF was lower by CMR than by Echo (51±13 vs. 54±10, p<0.001) and r-LVEF was more frequently detected by CMR (n=94, 18%) than by Echo (n=48, 9%), p<0.001. CMR significantly improved clinical+Echo stratification in those 112 patients (22%) with mr-Echo-LVEF (C-statistitics 0.74 vs 0.82; NRI and IDI: p<0.05) but it did not in those 355 patients (69%) with p-Echo-LVEF (C-statistitics 0.75 vs 0.76; NRI and IDI: non-significant) and in those 49 patients (9%) with r-Echo-LVEF (C-statistitics 0.77 vs 0.77; NRI and IDI: non-significant).
Figure 1. Risk stratification after STEMI

Conclusions
Applied in an individualized manner, Echo-LVEF appears as a useful gatekeeper for a selective use of CMR soon after STEMI for prognostic purposes. The event rate is high in patients with reduced Echo-LVEF and low in those with preserved Echo-LVEF; CMR does not seem to significantly improve risk stratification in these scenarios. Nevertheless, the occurrence of mid-range Echo-LVEF permits discriminating the specific subset of STEMI patients (less than a quarter) who really benefit from pre-discharge CMR in terms of risk assessment.

Acknowledgement/Funding
Funded by “Instituto de Salud Carlos III”/FEDER (PIE15/00013, PI17/01836, and CIBERCV16/11/00486 grants) and Generalitat Valenciana (GV/2018/116).