Follow-Up After Myocardial Infarction to Explore the Stability of Arrhythmogenic Substrate: The Footprint Study.

OBJECTIVES: This study aimed to characterize the long-term scar remodeling process after an acute myocardial infarction (AMI) and the underlying scar-related arrhythmogenic substrate using serial late gadolinium enhancement cardiac magnetic resonance (LGE-CMR). BACKGROUND: Little is known about the time course needed for completion of the scar healing process after an AMI, which can be assessed by noninvasive cardiac imaging techniques such as LGE-CMR. METHODS: Fifty-six patients with revascularized ST-segment elevation AMI (STEMI) were consecutively included. LGE-CMR (3-T) was obtained at 7 days, 6 months, and 4 years after STEMI. The myocardium was segmented into 10 layers from the endocardium to epicardium, characterizing the core, border zone (BZ), and BZ channels (BZCs) using a dedicated post-processing software. RESULTS: Mean age of the patients was 57 ± 11 years; 77% were men. Left ventricular ejection fraction improved at 6 months from 47% to 51% (p < 0.001) and remained stable at 4 years (53%; p = 0.21). Total scar mass decreased from 20.3 ± 14.6 g to 15.3 ± 13.3 g (6 months) and to 12.7 ± 11.7 g (4 years) (p < 0.001). Thirty of 56 (53%) patients showed a mean of 1.5 ± 1.3 BZCs/patient at 7 days, decreasing to 1.2 ± 1.3 (6 months) and 0.8 ± 1.0 (4 years) (p < 0.01). Only 42% of the initial BZCs remained present after 4 years. There were no arrhythmic events after a mean follow-up of 62.5 ± 7.4 months. CONCLUSIONS: CMR data post-processing permitted a dynamic assessment of quantitative and qualitative post-AMI scar characteristics. Scar size and number of BZCs steadily decreased 4 years after AMI. BZC distribution was significantly modified during this time. These dynamic parameters could be reliably assessed with CMR; their evaluation might be of prognostic value.

Identification of the potentially arrhythmogenic substrate in the acute phase of ST-segment elevation myocardial infarction.

BACKGROUND: Predicting sudden cardiac death risk in the first months after ST-segment elevation myocardial infarction (STEMI) remains challenging. OBJECTIVE: The purpose of this study was to investigate the ability of late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) to identify the potentially arrhythmogenic substrate and its temporal evolution after STEMI. METHODS: One hundred consecutive patients with a first STEMI were included. Three-dimensional high-resolution LGE-CMR was obtained at 3 T on days 7 and 180. Left ventricular wall was segmented and characterized by pixel signal intensity algorithm in 5 layers from endocardium to epicardium. A 3-dimensional color-coded shell map was obtained for each layer, depicting scar core and border zone (BZ) distribution. Presence and characteristics of BZ channels were registered for each layer. RESULTS: At 180 days, left ventricular ejection fraction had improved significantly (from 46.7% ± 10% to 51.5% ± 10%; P <.001) and scar mass was reduced (from 22.6 ± 20 g to 13.8 ± 12 g; P <.001). Most BZ channels (89%) were identified in the same myocardial layer and American Heart Association (AHA) segment, with the same orientation and morphology in both studies. Early LGE-CMR had 96% sensitivity and 90% specificity for predicting presence of BZ channels at 180 days. Greater presence was observed in patients with no-reflow phenomenon at baseline (P = .01). CONCLUSION: Most BZ channels can be identified by LGE-CMR at day 7 post-STEMI and, despite scar mass reduction, remain unaltered at 6 months, suggesting that the potentially arrhythmogenic substrate is established within the first week post-STEMI.