Cases reported "Long QT Syndrome"

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1/43. Preoperative hypoglycaemia, propranolol and the Jervell and Lange-Nielsen syndrome.

    The Jervell and Lange-Nielsen syndrome is an autosomal recessive trait characterized by deafness and electrocardiographic changes. These changes include prolongation of the QT interval and T-wave inversion. Treatment may include the use of beta-blockers to prevent the development of malignant ventricular arrhythmias and sudden death. We report a patient with this syndrome, who was receiving propranolol orally and who became hypoglycaemic during the preoperative fasting period prior to cochlear implantation.
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2/43. Prominent bifid T waves observed in the QT prolongation caused by complete atrioventricular blockade in a hypokalemic diabetic patient.

    A 63-year-old diabetic man was admitted with general fatigue. Electrocardiogram (ECG) on admission showed complete atrioventricular (AV) blockade associated with prominent bifid T waves. The second component of the bifid T waves was distinguished from U waves by the beat-to-beat varying bifidity and the nadir between the two components located at > or = 1 mm above the isoelectric line. Range of absolute QT interval was 535 to 650 ms. hypokalemia (3.6 mEq/L) was noted at admission. Partial restoration of the potassium level (3.9 mEq/L) prior to temporary ventricular demand pacing obscured the bifid T waves and attenuated the QT prolongation and dispersion to some extent (absolute QT interval ranging 520 to 620 ms). It was concluded that marked bradycardia caused by complete AV blockade (ie, a junctional escaped rhythm at a rate of 42 beats/min), hypokalemia, and underlying diabetes mellitus contributed in concert to the QT prolongation and dispersion leading to the prominent bifid T waves.
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3/43. nicorandil abolished repolarisation alternans in a patient with idiopathic long qt syndrome.

    A 23 year old woman with idiopathic long qt syndrome had repeated syncopal attacks associated with torsades de pointes. T wave alternans (TWA) was recorded and the QT interval was abnormally prolonged during treadmill exercise test. Monophasic action potential (MAP) alternans also appeared after an abrupt shortening of the cycle length in electrophysiological study. After intravenous administration of nicorandil 6 mg, both TWA and MAP alternans disappeared.
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4/43. long qt syndrome with a high mortality rate caused by a novel G572R missense mutation in KCNH2.

    In a four-generation family with long qt syndrome, syncopes and torsades de pointes ventricular tachycardia (TdP) were elicited by abrupt awakening in the early morning hours. The syndrome was associated with a novel KCNH2 missense mutation, G572R, causing the substitution of a glycine residue at position 572, at the end of the S5 transmembrane segment of the HERG K( )-channel, with an arginine residue. This segment is involved in the channel pore and the mutation may cause a reduction in the rapidly activating delayed rectifier K current (Ikr), or changed gating properties of the ion channel, leading to prolonged cardiac repolarization. The electrocardiograms of affected persons showed prolonged QT interval and notched T waves. Despite treatment with atenolol, 200 mg twice daily, the proband still experienced TdP episodes. Three untreated relatives of the proband died suddenly, and unexpectedly, at 18, 32, and 57 years of age. The G572R mutation is thus associated with a high mortality rate, and the clinical presentation illustrates that some mutations may not be controllable by just beta-blockade.
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5/43. Familial hypertrophic cardiomyopathy associated with prolongation of the QT interval.

    In a 61 year old female patient who suffered from atypical chest pain we diagnosed long qt syndrome by QTc duration of 467 ms, macroscopic T wave alternans and notched T waves in three leads and hypertrophic cardiomyopathy with asymmetric thickening of basal parts of the septum (2.0 cm) without relevant outflow tract obstruction by echocardiography. coronary angiography could exclude coronary artery disease. In a systematic family screening two sons of the patient could also be diagnosed as having long qt syndrome with QTc durations of 472 and 496 ms and asymmetric septal thickening (1.8 and 2.1 cm, respectively). One of these two sons suffered from pre-syncope, the other was asymptomatic despite maximum sports activity. In the third son, LQTS and hypertrophic cardiomyopathy could be excluded.
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6/43. prenatal diagnosis of QT prolongation by magnetocardiography.

    magnetocardiography constitutes a new tool for monitoring fetal cardiac activity. The fetal magnetocardiogram (FMCG) recorded noninvasively over the maternal abdomen is detectable with high temporal resolution and permits analysis of all parts of the PQRST waveform. In this way measurements of cardiac time intervals, including the QT interval, become possible. The following article constitutes the first report of antenatal detection of QT prolongation in two fetuses by FMCG.
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7/43. Novel arrhythmogenic mechanism revealed by a long-QT syndrome mutation in the cardiac Na( ) channel.

    Variant 3 of the congenital long-QT syndrome (LQTS-3) is caused by mutations in the gene encoding the alpha subunit of the cardiac Na( ) channel. In the present study, we report a novel LQTS-3 mutation, E1295K (EK), and describe its functional consequences when expressed in hek293 cells. The clinical phenotype of the proband indicated QT interval prolongation in the absence of T-wave morphological abnormalities and a steep QT/R-R relationship, consistent with an LQTS-3 lesion. However, biophysical analysis of mutant channels indicates that the EK mutation changes channel activity in a manner that is distinct from previously investigated LQTS-3 mutations. The EK mutation causes significant positive shifts in the half-maximal voltage (V(1/2)) of steady-state inactivation and activation ( 5.2 and 3.4 mV, respectively). These gating changes shift the window of voltages over which Na( ) channels do not completely inactivate without altering the magnitude of these currents. The change in voltage dependence of window currents suggests that this alteration in the voltage dependence of Na( ) channel gating may cause marked changes in action potential duration because of the unique voltage-dependent rectifying properties of cardiac K( ) channels that underlie the plateau and terminal repolarization phases of the action potential. Na( ) channel window current is likely to have a greater effect on net membrane current at more positive potentials (EK channels) where total K( ) channel conductance is low than at more negative potentials (wild-type channels), where total K( ) channel conductance is high. These findings suggest a fundamentally distinct mechanism of arrhythmogenesis for congenital LQTS-3.
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8/43. prenatal diagnosis of QT prolongation by fetal magnetocardiogram--use of QRS and T-wave current-arrow maps.

    To determine the T wave of a fetal magnetocardiogram (FMCG), we have evaluated the T/QRS ratio and obtained current-arrow maps that indicate weak currents. We measured FMCG signals for 52 normal fetuses and two abnormal fetuses with prolonged QT waves by using three superconducting quantum interference device (SQUID) systems: a nine-channel system, a 12-channel vector system and a 64-channel system. The T/QRS ratio was calculated for all the normal fetuses from the maximum magnitudes of the QRS complex and the T wave. Current-arrow maps of the QRS complex (R wave) and T wave were obtained by using the 64-channel system, and the phase differences of the total-current vectors were calculated by using the current-arrow maps. The results showed that the T/QRS ratio had a wide variability of 0.35 for the normal fetuses. However, the magnitude of the prolonged T wave was as weak as the detection limit of the SQUID magnetometer. Although the T/QRS ratios for the fetuses with QT prolongation were within the normal range (< 0.35), the weak magnitude of the prolonged T wave could be evaluated. On the other hand, by comparing the current-arrow maps of the R and T waves for the normal fetuses, we found that the maximum-current arrows were indicated as either in the same direction or in opposite directions. These patterns could be identified clearly by the phase differences. Very weak prolonged T waves for the two abnormal fetuses could be determined by using these current-arrow maps and phase differences. Consequently, although the T/QRS ratios of FMCG signals have a wide distribution, we have concluded that the current-arrow map and phase difference can be used to determine the T wave of an FMCG signal.
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9/43. Long QT interval resembling long qt syndrome in a newborn with electrolyte dysbalance.

    The Q-T interval by electrocardiogram may be prolonged as a congenital or acquired condition. The congenital form, long qt syndrome (LQTS) is an electrical disorder associated with a high mortality rate. However, in newborns, electrolyte abnormalities are one of the most common causes of a long Q-T interval. We describe a newborn with a prolonged Q-T interval (0.55 secs) and abnormal T waves resembling LQTS. In this case, the patient had an electrolyte disturbance which was effectively treated. This case emphasizes the importance of investigating and distinguishing between the congenital and acquired forms of prolonged Q-T intervals.
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10/43. Spontaneous T wave alternans and premature ventricular contractions during febrile illness in a patient with brugada syndrome.

    A 69-year-old man who had experienced syncope and ventricular fibrillation was referred to our hospital. ECG showed a right bundle branch block pattern with ST segment elevation in the right precordial leads. When the patient presented to the hospital with febrile illness, spontaneous T wave alternans and premature ventricular contractions were observed. When the patient became afebrile, ST segment elevation improved, and T wave alternans and premature ventricular contractions disappeared.
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