Introduction/ Purpose: The purpose of this study was to investigate the effect on clinical phenotype of a new autosomal dominant missense mutation (H562R/a1685g), not described previously, in KCNH2 gen. This mutation was originally described in a person of the family after suffering a resuscitated sudden cardiac death.
Methods: We studied 30 related individuals (aged 44±26 years, 50% males) from a person with KCNH2-H562R/a1685g mutation. A clinical evaluation with electrocardiographic assessment was carried out in each of them.
Results: We found the mutation in 13 individuals (43%), mean age 45±25 years and 46% males. In this group of patients, 76% (n=10) had prolonged QT interval in the electrocardiogram, defined as QTc value >450ms en males and >470ms in females, being the mean value of the QTc in this population of 504,60ms±38,56ms. However, 3 individuals presented the genetic mutation without prolonged QTc. Among individuals with positive genetic diagnosis, 5 patients (38,5%) presented events: all of them suffered repetitive syncopes, one had a sudden cardiac death (SCD) and the other a resuscitated SCD. All clinical events occurred at rest and some of them in relation to the use of drugs that cause increased QT interval (erythromycin and fluoxetine).
Conclusions: KCNH2-H562R/a1685g is a new mutation responsible of long QT syndrome type 2. The study of 30 members of our family reveals a high penetrance of this new mutation. Further studies are required to analyze the effects of this mutation on the function and traffic of KCNH2 channels.