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Catecholamine‐Provoked Microvoltage T Wave Alternans in Genotyped Long QT Syndrome
Author(s) -
NEMEC JAN,
ACKERMAN MICHAEL J.,
TESTER DAVID J.,
HEJLIK JOSEPH,
SHEN WINKUANG
Publication year - 2003
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1046/j.1460-9592.2003.t01-1-00249.x
Subject(s) - medicine , t wave alternans , long qt syndrome , cardiology , qt interval , sudden cardiac death
Macrovoltage T wave alternans (TWA) has been described in congenital long QT syndrome (LQTS). Microvoltage T wave alternans (μV‐TWA) at low heart rate (HR) is a marker of arrhythmogenic risk in many conditions, but its significance in LQTS has not been established. Twenty‐three genotypically heterogeneous patients with LQTS and 16 control subjects were studied at rest and during phenylephrine and dobutamine provocation. Genotyping was established by PCR amplification and DNA sequencing of the three most common LQTS genes; KCNQ1/KVLQT1 (LQT1), KCNH2/HERG (LQT2), and SCN5A (LQT3). μV‐TWA was determined using Fast Fourier transform. Precluded by ectopy, μV‐TWA could not be assessed in 8 of 23 patients with LQTS. In the remaining 15 patients with LQTS, μV‐TWA occurred at lower HR in LQTS than in controls (117 ± 49vs153 ± 37 beats/min; P < 0.05). Patients with LQTS developed μV‐TWA at HR < 150 beats/min more often than controls (10/15 vs 2/16; P = 0.003). However, μV‐TWA was not detected in the 3 individuals with a history of out‐of‐hospital cardiac arrest including a 14‐year‐old male with an F339del‐KVLQT1 mutation (LQT1) who had dobutamine‐provoked polymorphic ventricular tachycardia requiring external defibrillation. Catecholamine‐provoked μV‐TWA occurs at lower HR in patients with LQTS than in healthy people but does not identify high risk subjects. (PACE 2003; 26:1660–1667)