Cascade screening in families with inherited cardiac diseases driven by cardiologists: feasibility and nationwide outcome in long QT syndrome.

Objectives: We assessed the outcome of cascade screening of families with congenital long QT syndrome (LQTS) in Danish heart centers.

Methods: Affected family members were identified through systematic family screening.

Results: In total, 228 affected relatives were identified from 90 families. A disease-causing mutation useful for presymptomatic genetic testing was found in 82% of probands. Two-thirds of affected relatives fulfilled electrocardiographic criteria for the diagnosis, whereas diagnosis was based on genetic findings in only one-third. The majority of affected relatives were asymptomatic. Symptomatic relatives and probands most often presented with syncope, followed by aborted cardiac arrest and sudden cardiac death. A serious cardiac event (SCE, such as syncope, aborted cardiac arrest or cardiac arrest) was reported by 32% of affected relatives and 87% of probands (p < 0.0001). Fifty-two percent of affected relatives were on β-blockers and 11% had an implantable cardioverter defibrillator (ICD), as compared to 88 and 49% of probands (p < 0.0001). Appropriate ICD therapy was given to 13% of affected relatives and to 27% of probands (p = 0.1).

Conclusions: Clinically driven cascade screening of Danish LQTS families identified 2-3 affected relatives per proband. Affected relatives had milder disease courses, but SCEs in a subset strongly support screening. Danish cardiologists have adopted cascade screening of LQTS families according to specific Danish guidelines.