Instability of repolarization in LQTS mutation carriers compared to healthy control subjects assessed by vectorcardiography

Vahedi, Farzad; Diamant, Ulla‐Britt; Lundahl, Gunilla; Bergqvist, Gabriel; Gransberg, Lennart; Jensen, Steen M.; Bergfeldt, Lennart

doi:10.1016/j.hrthm.2013.05.001

Cited by 8 publications

(5 citation statements)

References 34 publications

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“…Because both VG and T area are rate dependent and decrease with increasing HR, the lack of difference in HR between the groups is of note (Fig. 2D) (26). This result is in agreement with in vitro studies using optical mapping in the Langendorff preparation of hearts from the transgenic rabbit model of LQT1 (3).…”

Section: Dispersion Of Vrsupporting

confidence: 87%

“…There was a correlation between T p-e and QT when taking all adult LQT1 and LQT2 mutation carriers and the controls together (r ϭ 0.44, r 2 ϭ 0.19; P Ͻ 0.000). Furthermore, in a recent study applying beat-to-beat analysis, our laboratory showed that the longer the QT interval, the larger was its instantaneous instability and also the instability of T area and VG (26). Compared with age-and sex-matched controls, the instability was more than doubled.…”

Section: Dispersion Of Vrmentioning

confidence: 93%

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Electrophysiological phenotype in the LQTS mutations Y111C and R518X in the KCNQ1 gene

Diamant

Vahedi

Winbo

et al. 2013

Journal of Applied Physiology

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Long QT syndrome is the prototypical disorder of ventricular repolarization (VR), and a genotype-phenotype relation is postulated. Furthermore, although increased VR heterogeneity (dispersion) may be important in the arrhythmogenicity in long QT syndrome, this hypothesis has not been evaluated in humans and cannot be tested by conventional electrocardiography. In contrast, vectorcardiography allows assessment of VR heterogeneity and is more sensitive to VR alterations than electrocardiography. Therefore, vectorcardiography was used to compare the electrophysiological phenotypes of two mutations in the LQT1 gene with different in vitro biophysical properties, and with LQT2 mutation carriers and healthy control subjects. We included 99 LQT1 gene mutation carriers (57 Y111C, 42 R518X) and 19 LQT2 gene mutation carriers. Potassium channel function is in vitro most severely impaired in Y111C. The control group consisted of 121 healthy subjects. QRS, QT, and T-peak to T-end (Tp-e) intervals, measures of the QRS vector and T vector and their relationship, and T-loop morphology parameters were compared at rest. Apart from a longer heart rate-corrected QT interval (QT heart rate corrected according to Bazett) in Y111C mutation carriers, there were no significant differences between the two LQT1 mutations. No signs of increased VR heterogeneity were observed among the LQT1 and LQT2 mutation carriers. QT heart rate corrected according to Bazett and Tp-e were longer, and the Tp-e-to-QT ratio greater in LQT2 than in LQT1 and the control group. In conclusion, there was a marked discrepancy between in vitro potassium channel function and in vivo electrophysiological properties in these two LQT1 mutations. Together with previous observations of the relatively low risk for clinical events in Y111C mutation carriers, our results indicate need for cautiousness in predicting in vivo electrophysiological properties and the propensity for clinical events based on in vitro assessment of ion channel function alone.

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Section: Dispersion Of Vrsupporting

confidence: 87%

Section: Dispersion Of Vrmentioning

confidence: 93%

Electrophysiological phenotype in the LQTS mutations Y111C and R518X in the KCNQ1 gene

Diamant

Vahedi

Winbo

et al. 2013

Journal of Applied Physiology

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“…Atrial fibrillation may also affect the precision of the VCG parameters by the continuous atrial activity superimposed on the QRST complex and not cancelled out by signal-averaging in the QRST complexes. Furthermore, increased ventricular repolarization variability is a salient feature of the long QT syndrome and other arrhythmia prone conditions [23][24][25]. Guided by the instability value, 70 recordings with the highest values were picked for manual scrutiny.…”

Section: Methodological Aspects Limitations and Implicationsmentioning

confidence: 99%

Automatic identification of a stable QRST complex for non-invasive evaluation of human cardiac electrophysiology

et al. 2020

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Background A vectorcardiography approach to electrocardiology contributes to the non-invasive assessment of electrical heterogeneity in the ventricles of the heart and to risk stratification for cardiac events including sudden cardiac death. The aim of this study was to develop an automatic method that identifies a representative QRST complex (QRSonset to Tend) from a Frank vectorcardiogram (VCG). This method should provide reliable measurements of morphological VCG parameters and signal when such measurements required manual scrutiny. Methods Frank VCG was recorded in a population-based sample of 1094 participants (550 women) 50-65 years old as part of the Swedish CArdioPulmonary bioImage Study (SCAPIS) pilot. Standardized supine rest allowing heart rate stabilization and adaptation of ventricular repolarization preceded a recording period lasting �5 minutes. In the Frank VCG a recording segment during steady-state conditions and with good signal quality was selected based on QRST variability. In this segment a representative signal-averaged QRST complex from cardiac cycles during 10s was selected. Twenty-eight morphological parameters were calculated including both conventional conduction intervals and VCG-derived parameters. The reliability and reproducibility of these parameters were evaluated when using completely automatic and automatic but manually edited annotation points.

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“…T amplitude is the maximal amplitude of the T-wave vector inscribed in the T loop. These measures are all global measures of VR dispersion and provide information beyond what can be obtained from routine 12-lead ECG measures (Draisma, Schalij, Wall, & Swenne, 2006;Geselowitz, 1983;Hurst, 2005;Man, Maan, Schalij, & Swenne, 2015;Vahedi et al, 2013;Van Huysduynen et al, 2005;Wecke et al, 2013;Wecke, Rubulis, Lundahl, Rosen, & Bergfeldt, 2007). In the analysis, we primarily focused on changes in these parameters during acceleration of HR.…”

Section: Adaptation Of Vr Duration and Dispersionmentioning

confidence: 99%

Adaptation of ventricular repolarization duration and dispersion during changes in heart rate induced by atrial stimulation

Axelsson

Brännlund

Gransberg

et al. 2019

Noninvasive Electrocardiol

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Background The duration of ventricular repolarization (VR) and its spatial and temporal heterogeneity are central elements in arrhythmogenesis. We studied the adaptation of VR duration and dispersion and their relationship in healthy human subjects during atrial pacing. Methods Patients 20‐50 years of age who were scheduled for ablation of supraventricular tachycardia without preexcitation but otherwise healthy were eligible. Vectorcardiography recordings with Frank leads were used for data collection. Incremental atrial pacing from a coronary sinus electrode was performed by decrements of 10ms/cycle from just above sinus rate, and then kept at a fixed heart rate (HR) just below the Wenckebach rate for ≥5min and then stopped. VR duration was measured as QT and VR dispersion as T area, T amplitude and ventricular gradient. The primary measure (T90 End) was the time to reach 90% change from baseline to the steady state value during and after pacing. Results A complete study protocol was accomplished in 9 individuals (6 women). VR duration displayed a monophasic adaptation during HR acceleration lasting on average 20s. The median (Q1‐Q3) T90 End for QT was 85s (51‐104), a delay by a factor >4. All dispersion measures displayed a tri‐phasic response pattern during HR acceleration and T90 End was 3‐5 times shorter than for VR duration. Conclusions Even during close to “physiological” conditions, complex and differing response patterns in VR duration and dispersion measures followed changes in HR. Extended knowledge about these responses in disease conditions might assist in risk evaluation and finding therapeutic alternatives.

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Instability of repolarization in LQTS mutation carriers compared to healthy control subjects assessed by vectorcardiography

Cited by 8 publications

References 34 publications

Electrophysiological phenotype in the LQTS mutations Y111C and R518X in the KCNQ1 gene

Electrophysiological phenotype in the LQTS mutations Y111C and R518X in the KCNQ1 gene

Automatic identification of a stable QRST complex for non-invasive evaluation of human cardiac electrophysiology

Adaptation of ventricular repolarization duration and dispersion during changes in heart rate induced by atrial stimulation

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