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Arthur A M Wilde - One of the best experts on this subject based on the ideXlab platform.

  • andersen tawil syndrome scarier for the doctor than for the patient who when and how to treat
    Europace, 2013
    Co-Authors: Arthur A M Wilde
    Abstract:

    This editorial refers to ‘Cardiac characteristics and long-term oUtcome in Andersen–Tawil syndrome patients related to KCNJ2 mUtation’ by E. Delannoy et al ., on page 1805. Andersen–Tawil syndrome (ATS) is a rare arrhythmia disorder combining a signatUre arrhythmia phenotype, consisting of a pronoUnced U-Wave and freqUent ventricUlar extrasystoles ( FigUre 1 ) with extracardiac featUres inclUding periodic paralysis and dysmorphic featUres.1 Occasionally, complex ventricUlar arrhythmias inclUding bidirectional ventricUlar tachycardia and ventricUlar fibrillation occUr.1 The pronoUnced U-Wave can easily be distingUished from the ST segment, and becaUse the QT interval itself is actUally not prolonged,2,3 the generally Used synonym long-QT syndrome type 7 seems inappropriate.2 Instead, ATS shoUld probably be Used, and becaUse of the presUmed heterogenetic basis, ATS type 1 is the appropriate terminology for at least half the cases in whom mUtations are foUnd in the KCNJ2 gene which encodes for the inward rectifying potassiUm channel Kir2.1 (condUcting the inward rectifying potassiUm cUrrent I K1).4 Other caUsal genes are likely to be present bUt have not been identified yet. FigUre 1 Typical ECG of an ATS1 patient. Please note the large U-Wave and related ectopy (inlay). Loss-of-fUnction mUtations lead to less I K1. It has been shown that the amplitUde of I K1 is critical for the amplitUde of the U-Wave.5 Indeed, decreased I K1 amplitUde exaggerates the U-Wave and increased I K1 amplitUde diminishes the U-Wave.5 Based on these data, most probably, intrinsic differences in the terminal part of the ventricUlar action potential, critically …

Li Zhang - One of the best experts on this subject based on the ideXlab platform.

  • The enigmatic sixth Wave of the electrocardiogram: the U Wave.
    Cardiology journal, 2008
    Co-Authors: Andrés Ricardo Pérez Riera, Celso Ferreira, Celso Ferreira Filho, Marcelo U. Ferreira, Adriano Meneghini, Augusto Hiroshi Uchida, Edgardo Schapachnik, Sergio Dubner, Li Zhang
    Abstract:

    The U Wave is the last, inconstant, smallest, roUnded and Upward deflection of the electrocardiogram. Controversial in origin, it is sometimes seen following the T Wave with the TU jUnction along the baseline or fUsed with it and before P of the following cycle on the TP segment. In this review we will stUdy its temporal location related to monophasic action potential, cardiac cycle and heart soUnds, polarity, voltage or amplitUde, freqUency and shapecontoUr. We will analyze the clinical significance of negative, alternant, prominent U Wave, and the difference between T Wave with two peaks (T 1 –T 2 ) and trUe U Wave. Finally we will analyze the foUr main hypotheses aboUt the soUrce of U Wave: repolarization of the intraventricUlar condUcting system or PUrkinje fibers system, delayed repolarization of the papillary mUscles, afterpotentials caUsed by mechanoelectrical hypothesis or mechanoelectrical feedback, and the prolonged repolarization in the cells of the mid-myocardiUm (“M-cells”).

  • electrocardiographic featUres in andersen tawil syndrome patients with kcnj2 mUtations characteristic t U Wave patterns predict the kcnj2 genotype
    Circulation, 2005
    Co-Authors: Li Zhang, Woodrow D Benson, Martin Tristanifirouzi, Louis J Ptacek, Rabi Tawil, Peter J Schwartz, Alfred L George, Minoru Horie, Gregor Andelfinger
    Abstract:

    BackgroUnd— The ECG featUres of Andersen-Tawil syndrome (ATS) patients with KCNJ2 mUtations (ATS1) have not been systematically assessed. This stUdy aimed to define ECG featUres of KCNJ2 mUtation carriers, to determine whether characteristic T-U–Wave patterns exist, and to establish whether T-U patterns predict the ATS1 genotype. Methods and ResUlts— In phase I, evalUation of T-U morphology in ECGs of 39 KCNJ2 mUtation carriers identified characteristic T-U patterns: prolonged terminal T downslope, wide T-U jUnction, and biphasic and enlarged U Waves. In phase II, ATS1 genotype prediction by T-U pattern was evalUated in the next 147 ECGs (57 other KCNJ2 mUtation carriers, 61 Unaffected family members, and 29 ATS patients withoUt KCNJ2 mUtations), with a sensitivity of 84% and specificity of 97%. Characteristic T-U patterns were present in 91% (87/96), in whom an enlarged U Wave was predominant (73%). In phase III, QTc, QUc, and T- and U-Wave dUration/amplitUde were compared in the 96 ATS1, 29 non-KCNJ2 AT...

Kunihisa Miwa - One of the best experts on this subject based on the ideXlab platform.

  • exercise indUced U Wave alterations as a marker of well developed and well fUnctioning collateral vessels in patients with effort angina
    Journal of the American College of Cardiology, 2000
    Co-Authors: Kunihisa Miwa, Keiko Nakagawa, Tadakazu Hirai, Hiroshi Inoue
    Abstract:

    OBJECTIVES We soUght to determine whether exercise-indUced U-Wave alterations are observed in association with well-developed and well-fUnctioning collateral vessels. BACKGROUND AlthoUgh exercise-indUced electrocardiographic (ECG) U-Wave alterations inclUding negative and prominent U Waves have been established as a marker of significant or critical narrowing of a major coronary artery, the relation between this finding and the degree of collateral development has not yet been determined. METHODS Patients with stable effort angina were divided into two groUps according to the presence (groUp A, n = 46) or absence (groUp B, n = 79) of exercise-indUced either negative or prominent U Waves in the precordial leads; the clinical profiles, coronary angiographic findings and also ischemic statUs dUring 60 s of coronary balloon occlUsion were compared between the two groUps. RESULTS The incidence of severe angina (CCS [Canadian CardiovascUlar Society] class III or IV) was higher (p < 0.05) in groUp A (52%) than in groUp B (32%) patients. Good collateral vessels (Rentrop grade 2 or 3) into the perfUsion territory of the cUlprit vessel were observed more freqUently (p < 0.05) in groUp A (70%) than in groUp B (43%) patients. Coronary balloon angioplasty was carried oUt in 23 patients of groUp A and 40 patients of groUp B. Both ischemic ST changes (52% vs. 85%) and angina (57% vs. 80%) dUring balloon inflation were less (p < 0.05) freqUently observed in groUp A than in groUp B. The incidence of no apparent myocardial ischemia with ST deviation or angina dUring the balloon inflation was higher (p < 0.05) in groUp A (39%) than in groUp B (10%) patients. In the prediction of the absence of myocardial ischemia dUring balloon inflation by the presence of exercise-indUced U-Wave alterations, the sensitivity was 69% (9/13) and the specificity was 72% (36/50) in the stUdy patients. CONCLUSIONS Exercise-indUced U-Wave alterations are a marker for well-developed collateral circUlation in patients with stable bUt severe effort angina. This finding is also highly predictive of the absence of myocardial ischemia dUring transient coronary balloon occlUsion and possibly of low-risk for development of acUte myocardial infarction or hemodynamic instability Upon abrUpt closUre of the cUlprit coronary artery.

  • Transient terminal U Wave inversion as a more specific marker for myocardial ischemia
    American Heart Journal, 1993
    Co-Authors: Kunihisa Miwa, Yuko Miyagi, Masatoshi Fujita, Akira Fujiki, Shigetake Sasayama
    Abstract:

    Transient U Wave inversion can be caUsed either by regional myocardial ischemia or by an elevation of systemic blood pressUre. The characteristics of U Wave inversion dUring chest pain attacks in 21 patients with variant angina were compared with those observed in 38 patients with hypertension withoUt apparent ischemic heart disease. Differentiation was possible according to the ECG phase in which U Wave inversion appeared. U Wave inversion was considered to be significant if there was a discrete negative deflection of more than 0.05 mV within the TP segment. U Wave inversion proceeded to positive deflection of U Wave in patients with hypertension withoUt ischemic heart disease (initial U Wave inversion). In contrast, inverted U Wave occUrred after positive U Wave deflection dUring attacks in patients with variant angina (terminal U Wave inversion). When cold pressor test was performed in patients with variant angina dUring treatment with calciUm entry blockers, no patient had either anginal attacks or ischemic ST-segment deviation, bUt 9 of 21 patients (43%) had transient initial U Wave inversion, which was followed by positive U Wave deflection. U Wave inversion can be classified as initial U Wave inversion and terminal U Wave inversion according to the phasic relationship to positive U Wave deflection; the latter is observed in association with regional myocardial ischemia. The former seems to be related to elevated blood pressUre rather than to myocardial ischemia.

Fotios Kardaras - One of the best experts on this subject based on the ideXlab platform.

  • swimming triggered aborted sUdden cardiac death in a patient with andersen tawil syndrome
    International Journal of Cardiology, 2006
    Co-Authors: Michalis Efremidis, Loukas K Pappas, Antonios Sideris, Konstantinos P Letsas, Gerasimos Gavrielatos, Fotios Kardaras
    Abstract:

    In this report we describe the case of a 42-year-old woman who experienced an episode of near drowning dUring recreational swimming. A diagnosis of Andersen-Tawil syndrome was made based on the patient's dysmorphic featUres, characteristic T-U-Wave patterns and ventricUlar arrhythmias. To oUr knowledge, this is the first report of a swimming-triggered cardiac event in a patient with Andersen-Tawil syndrome.

Gerard Van Herpen - One of the best experts on this subject based on the ideXlab platform.

  • The U Wave in the electrocardiogram: A solUtion for a 100-year-old riddle
    Cardiovascular Research, 2005
    Co-Authors: Jan A. Kors, Gerard Van Herpen
    Abstract:

    Objective : In the electrocardiogram (ECG) the U Wave follows the T, which is considered to reflect the repolarization of the cardiac ventricles. Despite the U Wave's well-known clinical relevance, a satisfactory explanation of its origin is still oUtstanding. We have Undertaken to explain the formation of the U Wave by means of a simple digital model of the left ventricle. Methods : The model employs a mUlti-layered segment of the myocardiUm. To each layer an action potential (AP) is assigned with shape and dUration according to pUblished data. The potential differences between the APs prodUce time-varying electrical soUrces. Each soUrce contribUtes to the potentials in an arbitrary point P of the body. The strength of this contribUtion is determined by a specific coefficient, the “lead vector”, linking P to the soUrce. The ECG recorded at P is calcUlated as the sUm of all potential contribUtions. ResUlts : The repolarization Waves constrUcted in this way reprodUce the natUral aspects of a T Wave followed by a U Wave. The creation of a U Wave is conditional on small voltage differences between the tail ends of the APs. No fUndamental demarcation exists between U Wave and preceding T Wave. The morphology of the T–U Wave is dependent on the geometrical position of P with respect to the myocardiUm. ConclUsion : T and U form a continUUm. Together they are the resUltant of one and the same process of repolarization of the ventricUlar myocardiUm. This has implications for the measUrement of QT dUration and for safety testing of drUg-indUced QT prolongation.

  • The U Wave explained as an intrinsic part of repolarization
    Computers in Cardiology 2005, 2005
    Co-Authors: Jan A. Kors, Gerard Van Herpen
    Abstract:

    In the ECG the U Wave follows the T, which is considered to reflect ventricUlar repolarization. Several hypotheses aboUt the genesis of the U Wave have been pUt forward, bUt a satisfactory explanation is still oUtstanding. We present a simple digital model of the left ventricle that simUlates the formation of the U Wave on the basis of known electrophysiological processes responsible for the electrical soUrces in the myocardiUm, and of the physical laws, embodied in the lead vector concept, which link the potentials in or on the body to these soUrces. The repolarization Waves constrUcted by the model reprodUce the natUral aspects of a T Wave followed by a U Wave. The creation of a U Wave appears to be conditional on small voltage differences between the tail ends of the action potentials assigned to the myocardial cells. No fUndamental demarcation exists between U Wave and preceding TWave

  • The elUsive U Wave: a simple explanation of its genesis
    Journal of Electrocardiology, 2003
    Co-Authors: Jan A. Kors, Gerard Van Herpen
    Abstract:

    Abstract Of the varioUs Waveforms in the electrocardiogram (ECG), the U Wave has been the most elUsive. After the first description of a U Wave by Einthoven several hypotheses were pUt forward as to its origin. Three of these are freqUently qUoted, ie: 1) the repolarization of the PUrkinje fibres; 2) the prolonged repolarization of the M-cells in the midmyocardiUm; and 3) after-potentials, possibly caUsed by mechanical forces in the ventricUlar wall. However, none of these hypotheses has gained general acceptance. We present a simple mUltilayered digital model of the myocardiUm, which explains the formation of the U Wave on the basis of known electrophysiological processes responsible for the electrical soUrces in the myocardiUm, and of the physical laws, formUlated in the lead vector concept, which link the potentials in or on the body to these soUrces. A realistic action potential (AP) is assigned to each layer. The timing of the APs is sUch that a normal ventricUlar wall activation is simUlated. The differences in APs between adjacent layers create cUrrent soUrces D i that contribUte to the potential coUrse at an arbitrary observation point P throUgh the heart vector-lead vector relationship. AssUming a homogeneoUs infinite mediUm, withoUt changing the AP shapes or dUrations and withoUt introdUcing after potentials, different realistically shaped T and U Waves are simUlated. Their amplitUdes and configUrations are dependent on the valUe of L, viz. the relative distance of the observation point to the myocardiUm. The gradUal and varying transition from T Wave into the U brings into qUestion the traditional view that the end of T Wave represents the end of the myocardial repolarization: T and U together mUst be considered as one repolarization complex. The traditional concept of QT prolongation woUld then need revision.