Cardiovascular Magnetic Resonance Imaging in the Assessment of the Management of Multivessel Coronary Artery Disease in Acute ST-Segment Elevation Myocardial Infarction

Background: Cardiovascular Magnetic Resonance (CMR) comprehensively assesses myocardial injury in ST-segment elevation myocardial infarction (STEMI). Complete revascularization (CR) may improve outcomes compared to an infarct-related artery (IRA)-only strategy in patients with multivessel disease at primary percutaneous coronary intervention (PPCI). However, CR could cause additional non-IRA infarcts. Objectives: To determine optimal techniques for quantifying infarct characteristics and myocardial strain in STEMI. To assess whether in-hospital CR was associated with increased myocardial injury compared to an IRA-only strategy in the CvLPRIT-CMR substudy. To investigate differences in myocardial injury associated with staged and immediate in-hospital CR. To assess CMR predictors of segmental myocardial functional recovery post-STEMI. Methods: Multicentre PROBE-design trial in STEMI patients with multivessel disease and ≤12 hours symptom duration. Patients were randomized to IRA-only PCI or in-hospital CR. Contrast-enhanced CMR was performed at 3 days post-PPCI and stress CMR at 9 months. The pre-specified primary endpoint was infarct size (IS) on acute CMR. Accuracy, feasibility and observer variability for semi-automated CMR methods of quantifying infarct size and area-at-risk (AAR) were assessed. Strain quantification using Feature Tracking and tagging was assessed. Functional recovery in dysfunctional segments was assessed at follow-up CMR on wall-motion scoring. Results: 205 of 296 patients in the main trial participated in CvLPRIT-CMR and 203 (105 IRA, 98 CR) completed acute CMR. There was a strong trend towards reduced AAR in the CR group (p=0.06). Total IS was similar with IRA-only PCI: 13.5% (6.2-21.9%) and CR: 12.6% (7.2-22.6) of LV mass, p=0.57. The CR group had an increased incidence of non-IRA MI at acute CMR (22/98 vs. 11/105, P=0.02). There was no difference in total IS or ischemic burden between the groups at follow-up CMR. Full-width half-maximum, Otsu's Automated Thresholding and Feature Tracking were used for IS, AAR and strain analysis. Immediate CR was associated with reduced IS. Conclusions: In-hospital CR for multivessel disease in STEMI leads to a small increase in CMR non-IRA MI but total IS was not different from an lRA-only PCI strategy. The comparable ischaemic burden in the groups suggests that the similarly improved medium-term clinical outcomes seen in the CvLPRIT, PRAMI and DANAMI-3- PRIMULTI studies are unlikely to be ischaemia-driven and instead may result from stabilization of unstable plaques and improved collateral flow to the ischaemic AAR.