Abnormal repolarization dynamics revealed in exercise test in long QT syndrome mutation carriers with normal resting QT interval

Abstract

LQTS mutation carriers lacking diagnostic QT interval prolongation exhibit abnormal QT and Tpe interval adaptations during physical exercise test. Looking for subtype-specific adaptations might facilitate the identification of LQTS mutation carriers when molecular genetic analysis is not available.

Long QT Syndrome with Nocturnal Cardiac Events Caused by a <i>KCNH2</i> Missense Mutation (G604S)

“…The QT/QTc interval response during the treadmill test was atypical of LQT3 genotype but it was not fully typical of LQT2 patients either (the slight QTc interval prolongation by exercise) according to the previous study by Hekkala et al (11).…”

Secondly ECG recordings in the emergency room revealed Garenoxacin-induced abnormal QT interval prolongation in a patient with multiple syncopal attacks

“…Although magnitude of the QTc interval prolongation by the two tests were mild, type-3 LQTS seemed less likely because the QTc interval was not shortened by sympathetic stimulation. Measurements of the interval between the peak and end of T wave (Tp-e) would be useful in discrimination between the types of LQTS in more detail [22,23]. However, our patient showed flat, biphasic or inverted T wave in most of the ECG leads (Figs.…”

“…In this patient, we prescribed metoprolol before obtaining the results of the genetic examination. This was because (a) beta-blocker is believed to be a first line medical treatment in most of the LQTS patients [18][19][20], and (b) results of the epinephrine infusion test and treadmill exercise test suggested either type-1 or type-2 LQTS [21][22][23]. Although magnitude of the QTc interval prolongation by the two tests were mild, type-3 LQTS seemed less likely because the QTc interval was not shortened by sympathetic stimulation.…”

Sudden Cardiac Death and Genetic Ion Channelopathies

“…Given the presence of incomplete penetrance and QT variability, exercise stress testing, Holter monitoring, and pharmacological challenge may be useful as diagnostic tests. [23][24][25] Once diagnosis is established, ␤-blocker therapy is recommended. LQT1 patients respond very well to ␤-blockers 26,27 ; interestingly, lack of compliance is the most important cause of events occurring during antiadrenergic treatment in LQT1.…”