Contemporary family screening in hypertrophic cardiomyopathy: the role of cardiovascular magnetic resonance

Genetic testing in relatives of hypertrophic cardiomyopathy (HCM) patients leads to early identification of pathogenic DNA variant carriers (G+), before the onset of left ventricular hypertrophy. Routine phenotyping consists of electrocardiography (ECG) and transthoracic echocardiography (TTE). Cardiovascular magnetic resonance (CMR) has become valuable in the work-up of HCM. In this study, we investigated the value of CMR in phenotyping of G+ family members.

This study included 91 G+ subjects who underwent ECG, TTE and CMR, with a maximal wall thickness (MWT) <15 mm on TTE. The relative performance of TTE and CMR regarding wall thickness measurements and HCM diagnoses was assessed. HCM was defined as MWT of ≥13 mm. Logistic regression was performed to assess whether ECG and TTE parameters can predict CMR results. Most subjects (75%) had an MWT <13 mm on TTE, of which 23 (34%) were diagnosed with HCM based on CMR. MWT differences (range 1–10 mm) were often caused by an anterobasal hook-shaped thickening of the myocardium not visible on TTE. Two of 23 (9%) subjects with HCM on TTE were reclassified as no HCM on CMR. Normal ECG and TTE results almost excluded reclassifications by CMR. The prevalence of other HCM-related abnormalities on CMR was low.

CMR reclassified 27% of subjects. Subjects with normal ECG/TTE results were reclassified in a low number of cases, justifying screening with ECG and TTE in G+ relatives. In subjects with abnormal ECGs and/or poor TTE image quality, CMR is indicated.