Remote myocardial fibrosis predicts adverse outcome in patients with myocardial infarction on clinical cardiac magnetic resonance imaging

Background
Heart failure (HF) most commonly occurs in patients who have had a myocardial infarction (MI), but factors other than MI size may be deterministic. Fibrosis of myocardium remote from the MI is associated with adverse remodelling. We aimed to i) Investigate the association between remote myocardial fibrosis, measured using cardiovascular magnetic resonance (CMR) extracellular volume (ECV), and HF and death following MI, ii) Identify predictors of remote myocardial fibrosis in patients with evidence of MI, and determine the relationship with infarct size.
Methods
Multicentre prospective cohort study of 1,199 consecutive patients undergoing CMR with evidence of MI on late gadolinium enhancement. Median follow-up 1,133 (895-1,442) days. Cox proportional hazards modelling was used to identify factors predictive of the primary outcome, a composite of first hospitalisation for HF (HHF) or all-cause mortality, post-CMR. Linear regression modelling was used to identify determinants of remote ECV.
Results
Remote myocardial fibrosis was a strong predictor of primary outcome (χ2: 15.6, HR: 1.07 per 1% increase in ECV, 95% CI: 1.04-1.11, p<0.001), and was separately predictive of both HHF and death. The strongest predictors of remote ECV were diabetes, sex, natriuretic peptides, and body mass index, but, despite extensive phenotyping, the adjusted model R2 was only 0.283. The relationship between infarct size and remote fibrosis was very weak.
Conclusions
Myocardial fibrosis, measured using CMR ECV, is a strong predictor of HHF and death in patients with evidence of MI. The mechanisms underlying remote myocardial fibrosis formation post-MI remain poorly understood, but factors other than infarct size appear to be important.