Prognostic importance of myocardial infarct characteristics

Abstract

Left ventricular (LV) systolic function and volumes are independent predictors of long-term survival after myocardial infarction (MI).1,2 The prognostic importance of LV pump function is mainly based on the association between systolic function and future risk of cardiac mortality related to heart failure and its consequences. Furthermore, the evidence-base for post-MI cardioprotective drug therapies, such as beta-blockers3 and angiotensin-converting enzyme inhibitors,4 is at least in part attributable to improvements in LV systolic function and attenuation of remodelling.5,6 This commentary focuses on the additive clinical utility of infarct characteristics, in addition to LV function, for prognostication after MI. Our commentary is stimulated by the publication by Lonborg et al .,7 who studied the prognostic importance of final infarct size 3 months after MI. To appreciate how their paper might be important, one must first understand the strengths and limitations of what is currently known about the clinical significance of infarct characteristics. Until recently, the assessment of myocardial infarct characteristics, such as infarct scar, microvascular obstruction (MVO), and myocardial haemorrhage, was the exclusive domain of pathologists at post-mortem examination. Since the clinical significance of these problems in vivo was not known no specific treatments exist. Cardiac magnetic resonance imaging (CMR) provides pathological information non-invasively. CMR reveals infarct scar as a bright area of late gadolinium enhancement ∼15 min after gadolinium contrast administration.8,9 MVO is delineated by a central dark area within the hyper-enhanced infarct zone and occurs in about two-fifths of patients after MI.10 Focal haemorrhagic transformation within the infarct zone is revealed by a central dark zone on T2- or T2*-weighted CMR11–14 and occurs in about one-third of patients.12–14 Myocardial salvage is the amount of ischaemically injured, but …