Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiac disease affecting one person in 500 and usually manifests in young adulthood [
28]. Several genetic mutations, mainly of proteins coding of the cardiac sarcomere [
26], have been linked to HCM. Patients with HCM can present with various symptoms ranging from dyspnea, palpations and fatigue to sudden cardiac death due to malignant arrhythmias [
8,
9]. Therefore, identification of young patients with subclinical HCM and patients at risk of HCM is important. The morphological hallmarks of HCM are left ventricular (LV) diastolic failure due to hypertrophy and stiffening of the myocardium, decreased myocardial perfusion and fibrosis [
2,
17,
35]. Cardiovascular magnetic resonance (CMR) has the ability to assess both LV thickness and volumes [
25], presence of ischemia using stress CMR [
35] and hyperenhancement on LGE-CMR [
33], which has been shown to correspond to fibrosis in HCM [
31]. The mechanisms and relation of the development of hypoperfused areas and fibrosis are, however, not fully understood. The genetic defect may cause a direct collagen deposition in the myocardium and vasculature causing hypoperfusion and myocardial fibrosis [
16,
38]. An alternative hypothesis is that hypoperfusion occurs first with subsequent replacement fibrosis [
4,
32]. The prognostic value of LGE in HCM remains elusive [
11,
18], and ischemia has been proposed as an earlier marker of disease [
4,
29,
32]. We have earlier showed that global perfusion is decreased in the same cohort of young patients with HCM investigated in the current study [
12]. However, the relationship between regional perfusion, hypertrophy and fibrosis has not been studied in young HCM patients and HCM-risk subjects. An important question is whether these changes are present already at the very early stage of the disease, i.e., before the onset of myocardial hypertrophy.
Therefore, the aim of this study was to (1) measure if regional perfusion is decreased in young patients with HCM and in HCM-risk subjects and (2) determine whether hypoperfused areas are larger than areas with fibrosis.