Qualitative and quantitative assessement of ECG characteristics in patients with Andersen–Tawil syndrome
█ Original article
Borbás János1, Takács Hedvig1, Környei László2, Katona Márta3, Ördög Balázs4
1Szegedi Tudományegyetem, II. sz. Belgyógyászati Klinika és Kardiológiai Központ, Szeged
2Gottsegen György Országos Kardiológiai Intézet, Budapest
3Szegedi Tudományegyetem, Gyermekgyógyászati Klinika, Szeged
4Szegedi Tudományegyetem, Farmakológiai és Farmakoterápiai Intézet, Szeged
Background: Andersen–Tawil syndrome (ATS) is a multisystem disorder mainly caused by mutations in KCNJ2 gene which encodes the main pore-forming protein of the inward rectifier K+ channel, Kir2.1. The disease is characterized by ventricular arrhythmias, periodic paralysis, dysmorphic features and specific ECG alterations.
Objective: Our aim was to qualitatively and quantitatively analyse typical ECG characteristics, described in the literature, in our patient cohort with ATS in comparison with that of observed in patients with the long QT syndrome (LQTS).
Patients and methods: Seven patients (6 females, 1 male, avg. age 25.4±11 yrs) with genetically confirmed ATS (three patients with p.Arg218His, one patient each with p.Arg312Glu, p.del302Val, p.Glu293Lys and p.Met307Ile KCNJ2 mutations) were examined. Quantitative ECG parameters [premature ventricular beats (PVB)/bigeminy, couplet, NSVT] and corrected QT and QU intervals, the duration and amplitude of the U waves were manually measured on good quality 12-lead resting ECG recordings. Data were compared to that of age- and sex-matched control patients with long QT syndrome (LQTS).
Results: Frequent ventricular extra-systoles (or bigeminy) were present in 71% (5/7) of ATS patients. Couplets or NSVT was observed in 57% (4/7) of ATS patients. As for quantitative ECG parameters corrected QT interval was significantly shorter in ATS patients compared to LQTS patients (451.2±44.4 vs. 518.4±66.4 ms, p<0.04), while corrected QU interval did not differ significantly (575.7±75.7 vs. 583.8±76.4 ms, p<0.84). The QTc was prolonged only in 43% (3/7) of ATS patients. The U waves were significantly longer (U wave duration: 143.0±26.3 vs. 78.5±18.5 ms, p<0.004) and taller (U vawe amplitude: 0.139±0.04 vs. 0.064±0.02 mV, p<0.0002) in ATS patients.
Conclusion: Patients with ATS usually exhibit typical ECG changes representing frequent ventricular ES, bigeminy or NSVT. Prolongation of the corrected QT interval is not typical and QTc may be in the normal range. U waves are more prominent, being longer and taller in these patients.