RISK OF CARDIAC EVENTS IN FAMILY MEMBERS OF PATIENTS WITH LONG QT SYNDROME

Objectives. This study sought to identify risk factors for cardiac eve nts (syncope, aborted cardiac arrest or sudden cardiac death) in famil y members of patients with the long QT syndrome. Background. Patients with the long QT syndrome are known to be at high risk for cardiac eve nts. Whenever the first member of a family is identified as having the long QT syndrome (proband), there is concern regarding the likelihood of cardiac events in other family members. Methods. A multivariate lo gistic regression model was used to evaluate the risk of cardiac event s in 637 family members who were first- and second-degree relatives of 151 probands with the long QT syndrome and in a subset of 513 family members who were not receiving beta-adrenergic blocking agents. There were 293 first-degree (46%) and 344 second degree relatives (54%) (293 men [46%], 344 women [54%]). Fifty percent of the family members had a corrected QT interval (QTc) >0.44 s, and relative tachycardia and br adycardia were observed in 12% and 25%, respectively. Results. The ris k of cardiac events occurring before age 40 in family members not taki ng beta-blockers was influenced by the QTc interval (odds ratio [OR] 1 .18/0.01 increase in QTc value; 95% confidence interval [CI] 1.12 to 1 .24), relative tachycardia (OR 2.21, 95% CI 0.97 to 5.02) or bradycard ia (OR 2.24, 95% CI 1.10 to 4.56) and an interaction term combining ge nder and closeness of the relationship to the proband (OR for female f irst-degree relative 3.23 vs. all second-degree relatives, 95% CI 1.67 -6.22). Conclusions. Female first-degree relatives of patients with th e long QT syndrome have a higher risk of cardiac events than male firs t- or second-degree relatives, independent of recorded electrocardiogr aphic findings. Not only bradycardia, but also tachycardia increases r isk of cardiac events in family members of patients with the long QT s yndrome.