The elusive link between LQT3 and Brugada syndrome - The role of flecainide challenge

Background-Defects of the SCN5A gene encoding the cardiac sodium channel ar e associated with both the LQT3 subtype of long-QT syndrome and Brugada syn drome (BS). The typical manifestations of long-QT syndrome (QT interval pro longation) and BS (ST segment elevation in leads V1 through V3) may coexist in the same patients, which raises questions about the actual differences between LQT3 and BS. Intravenous flecainide is the standard provocative tes t used to unmask BS in individuals with concealed forms of the disease, and oral flecainide has been proposed as a treatment option for LQT3 patients because it may shorten their QT interval. Methods and Results-We tested the possibility that in some LQT3 patients, f lecainide might not only shorten the QT interval, but also produce an eleva tion of the ST segment. A total of 13 patients from 7 LQT3 families receive d intravenous flecainide using the protocol used for BS. As expected, QT, Q Tc, JT, and JTc interval shortening was observed in 12 of the 13 patients, and concomitant ST segment elevation in leads V1 through V3 (greater than o r equal to 2 mm) was observed in 6 of the 13. Conclusions-The data demonstrate that flecainide may induce ST segment elev ation in LQT3 patients, raising concerns about the safety of flecainide the rapy and demonstrating the existence of an intriguing overlap between LQT3 and BS.