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

Abstract

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.

Keywords: arrhythmogenic substrate; border zone channels; cardiac magnetic resonance; myocardial infarction; ventricular arrhythmias.