CCT for Comprehensive Risk Stratification Following STEMI

Background / State of Art

STEMI remains a leading cause of mortality. In the first year, STEMI survivors face an incident burden of heart failure (HF) as high as 25%, of ischemic events up to 18.3% and of LTA up to 1.5%.

CMR has emerged as the most potent tool to predict adverse left ventricular (LV) remodeling following STEMI. Infarct size (IS), microvascular obstruction (MVO) and intramyocardial hemorrhage (IMH) measured by CMR are all independent HF predictors, able to outperform clinical and reperfusion parameters and to predict long-term adverse remodeling among patients with initially preserved LV ejection fraction (LVEF).

Systematic CMR implementation following STEMI into routine clinical practice is difficult for several reasons, including limited availability, high costs as well as practical issues such as time and staff allocation. Moreover, CMR does not assess the coronary tree failing to provide a risk assessment comprehensive of the atherothrombotic component, beyond HF and arrhythmias.

Since recent advances in CCT technology have expanded its applicability beyond accurate morpho-functional assessment to the characterization of the myocardium, allowing for quantification of IS, MVO and extracellular volume (ECV). CCT may now offer unprecedent opportunities to provide a comprehensive risk assessment following STEMI with an ever-increasing available technology, with moderate costs and logistic effectiveness, and with very low radiation dose exposure with current scanners and protocols.

Hypotesis and Significance

Despite giant leaps forward in the acute and chronic management, STEMI remains a leading cause of mortality and morbidity worldwide.

Risk stratification is the foundation to tailoring treatment selection and intensity. However, the current tools to predict adverse events following STEMI including HF development, recurrent atherothrombotic events and life-threatening arrhythmias have poor prediction abilities or require cumbersome and often unavailable diagnostic technologies.

CMR has emerged as the most potent tool to predict adverse LV) remodeling following STEMI. Current post-MI arrhythmic risk stratification to mandate implantable cardioverter defibrillator implantation is chiefly based on LV EF. However, the evaluation of scar burden by CMR may outperform EF to predict life-threatening arrhythmias and has the potential to improve management among patients without a current indication for an implantable cardioverter defibrillator.

Systematic CMR implementation following STEMI into routine clinical practice is difficult for several reasons, including limited availability, high costs as well as practical issues such as time and staff allocation. Moreover, while providing excellent myocardial tissue characterization, CMR does not assess the coronary tree failing to provide a risk assessment comprehensive of the atherothrombotic component, beyond HF and arrhythmias.

Since recent advances in CCT technology have expanded its applicability beyond accurate morpho-functional assessment to the characterization of the myocardium, CCT may now offer unprecedent opportunities to provide a comprehensive risk assessment following STEMI with an ever-increasing available technology, with moderate costs and logistic effectiveness, and with very low radiation dose exposure with current scanners and protocols.

While preliminary data on the CCT performance to assess myocardial tissue characteristics are promising, accurate validation of this technology against CMR and clinical outcomes in large populations will be pivotal for clinical implementation. Moreover, the application of this technology to stratify HF and arrhythmic risk following STEMI has never been assessed.

The CT-STEMI study will be the first to assess the potential of CCT to provide a comprehensive risk assessment following STEMI in a large contemporary population, to lay the bases for a paradigm shift in post-STEMI risk stratification.

Specific Aim 1 To compare the diagnostic accuracy of a comprehensive CCT protocol to that of CMR, the non-invasive gold standard.

Specific Aim 2 To determine the prognostic value of CCT-assessed myocardial tissue STEMI-related adverse features.

Specific Aim 3 To evaluate the atherosclerotic burden in patients with post-acute STEMI.

For this purpose, in this prospective study, a total of two hundred patients will be recruited and undergo coronary computed tomography (CCT) and cardiac magnetic resonance imaging (CMR) during the post-acute phase of ST-elevation myocardial infarction (STEMI).

Experimental Design Aim 1

The CMR study will be used as the reference standard to assess the accuracy of CCT in evaluating morpho-functional parameters such as Left Ventricular End-Diastolic Volume (LVEDV), Left Ventricular End-Systolic Volume (LVESV), LVEF, Right Ventricular End-Diastolic Volume (RVEDV), Right Ventricular End-Systolic Volume (RVESV), and Right Ventricular Ejection Fraction (RVEF). Additionally, the study will also examine myocardial tissue characteristics including IS, myocardial edema, MVO, IMH, and ECV.

Experimental Design Aim 2

The patients will undergo follow-up procedures starting from the commencement of the study. Co-primary endpoints will be:

• Atherothrombotic primary endpoint: composite of recurrent acute coronary syndrome, ischemic stroke or cardiovascular death
• HF and arrhythmic primary endpoint: composite of new congestive HF or sustained ventricular arrhythmia or appropriate Implantable Cardioverter-Defibrillator (ICD) intervention or sudden cardiac death or resuscitated cardiac arrest

Individual CCT predictors (EF, IS, myocardial edema, MVO, IMH and ECV) will be evaluated and compared with those derived from CMR.

Experimental Design Aim 3

The purpose of this sub-study is to report the prevalence and features of non-culprit plaques, as well as to investigate the independent predictive significance of CCT-assessed coronary plaque characteristics on event prediction.