Family Matters

• Editorials
• genetic testing
• heart failure
• long QT syndrome
• penetrance
• risk factors

See Article by van Velzen et al

Hypertrophic cardiomyopathy (HCM) is a clinically heterogeneous disease affecting up to 1 in 200 of the general population.¹ Primarily an autosomal dominantly inherited trait, first-degree relatives have a 50% risk of inheriting the underlying gene variant, though there are many examples of incomplete penetrance and variable expression. The factors that influence disease onset and severity are largely unknown, but it is a well-recognized phenomenon in HCM. Within one family there may be relatives who never develop disease, others who will present with only mild features, and tragically some will suffer the most serious outcomes of heart failure or sudden cardiac death. There is little to guide the discussion with families before a decision to undergo cascade genetic testing, and evidence relating to penetrance and outcomes of relatives remains sparse.

In this issue, van Velzen et al² present their long-term experience of cascade family screening in HCM. Over a 31-year period, a total of 777 relatives from 209 families were seen for family screening in the Erasmus Medical Center. Because of the widespread availability of genetic testing in the Netherlands, there is a unique ability to understand the long-term outcomes to the family. There were 620 relatives (80%) who underwent cascade genetic testing, with 264 (43%) shown to be genotype positive, whereas 356 (57%) were genotype negative and released from ongoing clinical surveillance. A third of the asymptomatic adult relatives were diagnosed with HCM at their first clinical evaluation, and annual cardiac mortality was calculated to be 0.3% per year. For the remainder of relatives, 16% developed disease during the mean 7-year follow-up period. Risk of cardiac events in unaffected gene carriers was very low with annual cardiac mortality of 0.1% per year, …