Clinical value of electrocardiographic parameters in genotyped individualswith familial long QT syndrome

Rate corrected QT interval (QTc) and QT dispersion (QTd) have been suggeste d as markers of an increased propensity to arrhythmic even ts and efficacy of therapy in patients with long QT syndrome (LQTS). To evaluate whether QT c and QTd correlate to genetic status and clinical symptoms in LQTS patient s and their relatives, ECGs of 116 genotyped individuals were analyzed. JTc and QTc were longest in symptomatic patients (n = 28). Both QTd and JTd we re significantly higher in symptomatic patients than in asymptomatic (n = 2 9) or unaffected family members (n = 59). The product of QTd/JTd and QTc/JT c was significantly different among all three groups. Both dispersion and p roduct put additional and independent power on identification of mutation c arriers when adjusted for sex and age in a logistic regression analysis. Th us, symptomatic patients with LQTS show marked inhomogenity of repolarizati on in the surface EGG. QT dispersion and QT product might be helpful in fin ding LQTS mutation carriers and might serve as additional ECG tools to iden tify asymptomatic LQTS patients.