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.