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Hypertrophic cardiomyopathy (HCM) is characterised by a high genetic, pathological and clinical heterogeneity, with an unpredictable natural history, and represents a challenge in terms of diagnosis, risk stratification and management. Although many patients have a benign clinical course, sudden cardiac death (SCD) can occur as the first manifestation of HCM in asymptomatic, often young subjects.1 Ventricular tachyarrhythmias represent the main underlying mechanism of SCD. The myocardial substrate creating arrhythmia susceptibility consists of myocyte disarray and hypertrophy, expansion of interstitial matrix with diffuse fibrosis, and small artery dysplasia responsible for silent microvascular ischaemia and myocyte death, ultimately repaired as replacement fibrosis.2 Although HCM is caused by sarcomere genes mutation, an important component of the phenotypic expression is determined by increased myocardial connective tissue. Different patterns of fibrosis have been described: increase in pericellular and fascicular connective tissue, plexiform fibrosis associated with myocardial disarray, perivascular fibrosis and microscopic replacement scars.3
There is emerging evidence that myocardial fibrosis is an early and fundamental manifestation of HCM, elevated levels of serum C-terminal pro-peptide of type I procollagen indicating increased myocardial collagen synthesis in sarcomere-mutation carriers without overt disease.4 There are data suggesting that myocardial fibrosis may have a pathophysiological role in the occurrence of SCD5 even in patients without conventional risk factors.6 Information about HCM histology is limited to specific phenotypes and stages of the disease, as data derive mainly from ex-vivo studies of patients who died suddenly, or from patients with end-stage disease who underwent heart transplantation.3 ,5
In the implantable cardioverter defibrillator era, increased attention has been given to proper stratification of risk for SCD by identifying more accurate clinical markers since conventional risk factors for SCD have a very low positive predictive value.1 Therefore, in vivo imaging of myocardial fibrosis by contrast-enhanced …
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