Fig. 1: Cardiac magnetic resonance (CMR) imaging.

The linked videos, as indicated in each separate panel, are available as Supplementary Videos 1–6. a, b Patient 1 findings at the time of the diagnosis showed dilated cardiomyopathy (left ventricle end-diastolic volume 105 mL/m², Z+2.4, end-systolic volume 65 mL/m², Z+4.5) and poor left ventricular systolic function (ejection fraction EF 38%). The right ventricular size and the systolic function were normal (right ventricular end-diastolic volume 87 mL/m², Z-0.5 end-systolic volume 47 mL/m², Z+1, EF 46%) in four-chamber and short-axis cine. Both right and left atria were mildly dilated, as a marker of diastolic dysfunction. c Gadolinium-enhanced T1 fat-saturated images showed mild late enhancement in the mid-myocardium of the intraventricular septum (arrows). d, e Patient 2 findings at the time when she was listed for heart transplantation showed pericardial effusion (stars), small left and right ventricles, and bi-atrial dilatation (left ventricular end-diastolic volume 43 mL/m², Z–3 and left ventricular end-systolic volume 22 mL/m², Z–1.2). The left ventricular systolic function was moderately decreased (ejection fraction EF 37%). Delayed enhancement imaging showed no evidence of a myocardial scar or focal fibrosis. f However, T1 mapping showed globally abnormal inversion times as a marker of diffuse fibrosis. g, h Patient 3 demonstrated, at the time of the diagnosis, bi-atrial enlargement but normal ventricular end-diastolic volumes (left ventricular end-diastolic volume 75 mL/m², Z 0.5 and left ventricular end-systolic volume 41 mL/m², Z 2.7, right ventricular end-diastolic volume 55 mL/m², Z–2.9 and right ventricular end-systolic volume 28 mL/m², Z–0.9). The right ventricular systolic function was normal (EF 50%) but left ventricular systolic function was mildly decreased on CMR (EF 45%). i CMR delayed enhancement imaging showed no evidence of a myocardial scar. The T1 mapping sequence was not performed.