Sudden Paradoxical QT‐Interval Prolongation Exacerbating T‐Wave Alternans in a Patient with Type 3 Long QT Syndrome

We report a case with type 3 congenital long QT syndrome, who exhibited a sudden paradoxical QT‐interval prolongation during a progressive increase in heart rate, which exacerbated T‐wave alternans.     

T‐Wave Morphology in Short QT Syndrome

Background: Short QT syndrome (SQTS) is an inherited disorder characterized by a short QT interval and vulnerability to ventricular tachyarrhythmias. The diagnostic criteria for this syndrome are not well defined, since there is uncertainty about the lowest normal limits for the corrected QT (QTc) interval. Objective: The aim of this study was to determine whether T‐wave morphology parameters are abnormal in short QT subjects and whether those parameters can help in the diagnosis of SQTS. Methods and Results: We describe three families (10 patients) with short QT intervals (QTc 310 ± 32 ms). Seven subjects had suffered serious arrhythmic events and three were asymptomatic. T‐wave morphology was assessed using the principal component analysis (PCA). QTc was significantly shorter and T‐wave amplitude in lead V₂ higher in the short QT subjects compared to healthy controls (n = 149), (P < 0.001 for both). The total cosine of the angle between the main vectors of the QRS and T‐wave loops (TCRT) was markedly abnormal among the symptomatic patients with short QT syndrome (n = 7) (TCRT –0.14 ± 0.55 vs 0.36 ± 0.51, P = 0.019). None of the three asymptomatic patients with short QT but without a history of arrhythmic events had an abnormally low TCRT. Conclusion: Our observations suggest that patients with a short QT interval and a history of arrhythmic events have abnormal T‐wave loop parameters. These electrocardiogram (ECG) features may help in the diagnosis of SQTS in addition to the measurement of the duration of QT interval from the 12‐lead ECG.     

Wolff–Parkinson–White Syndrome and Acute Pulmonary Embolism: A Case Report

A 48‐year‐old woman admitted to the emerhency departments due to sudden onset of dyspnea. The diagnosis of pulmonary embolism (PE) was made and thrombolytic therapy was started. Baseline ECG showed signs of right ventricular overload and after thrombolysis, short PR, wide QRS, and delta wave indicating Wolf‐Parkinson‐White (WPW) pattern were appeared. In this case report, we discuss ECG of patient with PE mimicknig WPW.     

QT Prolongation and T‐Wave Alternans during Catheter Ablation of Atrial Fibrillation: A Case Report

We report a case of a 63‐year‐old woman who developed profound QT prolongation, T‐wave alternans, and spontaneous ventricular fibrillation during catheter ablation of atrial fibrillation. A thorough search into the possible mechanisms identified the use of sevoflurane, an inhalational gas anesthetic as the culprit. The patient was converted to propofol anesthesia and her QT interval normalized promptly.     

Electrocardiographic T‐ and U‐Wave Discordance

Background: Abundant information has been reported regarding the U wave, which almost entirely has been focused on U waves in isolation. There has been little investigation of discordant T and U waves. Methods: Of 18,750 consecutively recorded electrocardiograms, 143 patients were categorized resulting in three groups. Group A: 53 patients with negative T waves and positive U waves (Type I Discordance); Group B: 26 patients with positive T waves and negative U waves (Type II Discordance); and Group C: 63 patients with negative T and negative U waves. Each patient's chart was reviewed for relevant clinical, laboratory, and medical history. Results: Coronary disease was slightly more common in Group A (64%) than in Group B (46%) (P = 0.174; ns). Coronary disease in Group C was extremely common (88%; P <0.001). Hypertension in the two discordant groups was similar: Group A (60%) versus Group B (58%) (P = ns), Group C was significantly higher (88%) (P <0.001). Left ventricular hypertrophy was 49% in Group A and 58% in Group B (P = ns), but Group C was significantly higher at 70% (P = 0.038). Conclusions: This appears to be the first investigation of the associations of discordant T and U waves. We found that the significance of any U wave is not independent of their respective T wave. In addition, we propose that the U wave not be analyzed in isolation, but rather with respect to its T wave.     

Microvolt T‐Wave Alternans during Holter Monitoring in Children and Adolescents

Background: Time‐domain microvolt T‐wave alternans (TWA) has been described as a noninvasive marker of sudden cardiac death in adults. The incidence of TWA in pediatric populations has not been defined well. The aim of the study was to determine peculiarities of TWA in children. Methods: We examined 68 healthy patients—newborns (20) and children in age group of 7–17 years (48)—and 85 pediatric patients: ventricular premature beats—65; dilated cardiomyopathy (DCMP)—2; long QT syndrome (LQTS)—10; Brugada syndrome (BrS)—5, catecholaminergic ventricular tachycardia (CVT)—3. All underwent Holter monitoring (HM) with definition of the peak value of TWA by modified moving average method. Results: In healthy newborns, TWA was 32 ± 8 (12–55) μV (HR 123–156 bmp). In healthy children (7–17 years) it was 30 ± 11 (10–l 55) μV, (HR 64–132 bmp) without any differences between boys and girls. In all group of patients, TWA were significantly higher (P < 0.05) than in healthy. Circadian peak of TWA was found (90%) in a second part of day and at sleep (8%). Among them 60% (LQTS, BrS, and DCPM) had TWA > 55 μV. Conclusion: Time‐domain TWA during HM in children was independent of age, gender, and heart rate. In 94% healthy children, values of TWA do not exceed 55 μV but 20–50% children with cardiac pathology had TWA more than 55 μV. Night circadian type of TWA in diseases with risk of life‐threatening arrhythmias associated with TWA was more than 55 μV. Ann Noninvasive Electrocardiol 2010;15(2):138–144     

Global T-wave inversion: limited QT dispersion despite QTc prolongation--a correlate of benignity in patients with strikingly abnormal electrocardiograms.

BACKGROUND: The global T-inversion (GTI) electrocardiogram (ECG) is strikingly abnormal with major QTc prolongation, but with a surprisingly good prognosis by Kaplan-Meier curve. This contrasts with most significant QTc prolongations. HYPOTHESIS: This study was undertaken to ascertain QT interval dispersion (QTd) in global T wave inversion, a clinically benign long QTc ECG. METHODS: Longest and shortest QT intervals in all 12 leads in 35 consecutive patients with GTI were determined by two mutually blinded observers. QTd was determined by subtraction (maximum-minimum) and QTc was calculated using the Bazett formula. RESULTS: There was a 2:1 female preponderance QTc was prolonged and equal for men (0.471) and women (0.469). Observer variability of under 2% permitted averaging of QT measurements. Composite mean QTd was 55 ms. The literature revealed a range of QTd in normal subjects of 39 to 59 ms (mostly 49 to 59 ms). Patient series with abnormal QTd were well above this level. CONCLUSION: Despite a strikingly abnormal ECG with marked QTc prolongation, QT dispersion was limited in global T inversion, consistent with its previously demonstrated benignity.     

Effects of Head‐Up Tilt‐Table Test on the QT Interval

Background. The QT interval shortens in response to sympathetic stimulation and its response to epinephrine infusion (in healthy individuals and patients with long QT syndrome) has been thoroughly studied. Head‐up tilt‐table (HUT) testing is an easy way to achieve brisk sympathetic stimulation. Yet, little is known about the response of the QT interval to HUT. Methods. We reviewed the electrocardiograms of HUT tests performed at our institution and compare the heart rate, QT, and QTc obtained immediately after HUT with the rest values. Results. The study group consisted of 41 patients (27 females and 14 males) aged 23.9 ± 8.4 years. Head‐up tilting led to a significant shortening of the RR interval (from 825 ± 128 msec at rest phase to 712 ± 130 msec in the upward tilt phase, P < 0.001) but only to a moderate shortening of the QT interval (from 363.7 ± 27.9 msec during rest to 355 ± 30.3 msec during upward tilt, P = 0.001). Since the RR interval shortened more than the QT interval, the QTc actually increased (from 403 ± 21.5 msec during rest phase to 423.2 ± 27.4 msec during upward tilt, P < 0.001). The QTc value measured for the upward tilt position was longer than the resting QTc value in 33 of 41 patients. Of those, 4 male patients and 2 female patients developed upward‐tilt QTc values above what would be considered abnormal at rest. Conclusions. During HUT the QT shortens less than the RR interval. Consequently, the QTc increases during head‐up tilt. Ann Noninvasive Electrocardiol 2010;15(3):245–249     

Assessment of Microvolt T‐Wave Alternans in High‐Risk Patients with the Congenital Long‐QT Syndrome

Background: Microvolt T‐wave alternans (MTWA) has been used for arrhythmogenic risk stratification in cardiac disease conditions associated with increased risk of sudden cardiac death. Macroscopic T‐wave alternans has been observed in patients with congenital long‐QT syndrome (LQTS). The role of MTWA testing in patients with LQTS has not been established. Objective: To determine the diagnostic value of MTWA testing in high‐risk patients with LQTS. Methods and results: We assessed MTWA in 10 consecutive LQTS index patients who survived cardiac arrest or had documented torsade de pointes tachycardia and 6 first‐degree family members with congenital LQTS which had been genotyped in 13 of 16 subjects (7 index patients, 6 family members). No LQTS‐causing mutation was identified in 3 index patients with overt QT prolongation. MTWA was assessed during standardized bicycle exercise testing using the spectral method and yielded negative (n = 8) or indeterminate (n = 2) results in index patients, respectively. Similarly, all first‐degree family members tested MTWA negative except for one indeterminate result. Two genotype positive family members could not be tested (two children—4 and 9 years of age). Conclusion: In patients with congenital LQTS, free from structural heart disease and with a history of life‐threatening cardiac arrhythmias, assessment of MTWA does not yield diagnostic value. Hence, determination of MTWA in lower risk LQTS patients without spontaneous arrhythmic events is likely not to be useful for arrhythmia risk stratification.     

Relation between Beat‐to‐Beat QT Interval Variability and T‐Wave Amplitude in Healthy Subjects

Objectives: Elevated beat‐to‐beat QT interval variability (QTV) has been associated with increased cardiovascular morbidity and mortality.The aim of this study was to investigate interlead differences in beat‐to‐beat QTV of 12‐lead ECG and its relationship with the T wave amplitude. Methods: Short‐term 12‐lead ECGs of 72 healthy subjects (17 f, 38 ± 14 years; 55 m, 39 ± 13 years) were studied. Beat‐to‐beat QT intervals were extracted separately for each lead using a template matching algorithm. We calculated the standard deviation of beat‐to‐beat QT intervals as a marker of QTV as well as interlead correlation coefficients. In addition, we measured the median T‐wave amplitude in each lead. Results: There was a significant difference in the standard deviation of beat‐to‐beat QT intervals between leads (minimum: lead V₃ (2.58 ± 1.36 ms), maximum: lead III (7.2 ± 6.4 ms), ANOVA: P < 0.0001). Single measure intraclass correlation coefficients of beat‐to‐beat QT intervals were 0.27 ± 0.18. Interlead correlation coefficients varied between 0.08 ± 0.33 for lead III and lead V₁ and 0.88 ± 0.09 for lead II and lead aVR. QTV was negatively correlated with the T‐wave amplitude (r =–0.62, P < 0.0001). There was no significant affect of mean heart rate, age or gender on QT variability (ANOVA: P > 0.05). Conclusions: QTV varies considerably between leads in magnitude as well as temporal patterns. QTV is increased when the T wave is small.     

Fetal Atrioventricular Block and Postpartum Augmentative QT Prolongation in a Patient With Long‐QT Syndrome With KCNQ1 Mutation

2:1 AV Block in KCNQ1. The case of a 32‐year‐old pregnant woman, who had had several syncopal episodes during swimming and running at 9 and 10 years of age and whose fetus had 2:1 AV block, is presented. The mother and baby had the same heterozygous single nucleotide substitution in KCNQ1 at T587M. After 27 weeks of gestation, the fetal 2:1 AV block disappeared, and 1:1 AV conduction resumed, with a fetal heart rate of 110–120 beats/min. The maternal electrocardiogram revealed a normal QTc interval (433 ms) without ST‐T abnormalities at gestational week 23, but the QTc was 490 and 531 ms at 1 and 2 months postpartum, with biphasic T waves in leads V2 and V3. This case is the first report of fetal 2:1 AV block with KCNQ1 mutation (T587M) and unmasked maternal QT prolongation in the postpartum period. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1170‐1173)     

Electrocardiographic Differentiation between Acute Pulmonary Embolism and Non‐ST Elevation Acute Coronary Syndromes at the Bedside

Background: Clinical picture of acute pulmonary embolism (APE), with wide range of electrocardiographic (ECG) abnormalities can mimic acute coronary syndromes. Objectives: Assessment of standard 12‐lead ECG usefulness in differentiation at the bedside between APE and non‐ST elevation acute coronary syndrome (NSTE‐ACS). Methods: Retrospective analysis of 143 patients: 98 consecutive patients (mean age 63.4 ± 19.4 year, 45 M) with APE and 45 consecutive patients (mean age 72.8 ± 10.8 year, 44 M) with NSTE‐ACS. Standard ECGs recorded on admission were compared in separated groups. Results: Right bundle branch block (RBBB) and S₁S₂S₃ or S₁Q₃T₃ pattern were found in similar frequency in both groups (10 [11%] APE patients vs 6 [14%] NSTE‐ACS patients, 27 [28%] patients vs 7 [16%] patients, respectively, NS). Negative T waves in leads V_1‐3 together with negative T waves in inferior wall leads II, III, aVF (OR 1.3 [1.14–1.68]) significantly indicated APE with a positive predictive value of 85% and specificity of 87%. However, counterclockwise axis rotation (OR 4.57 [2.74–7.61]), ventricular premature beats (OR 2.60 [1.60–4.19]), ST depression in leads V_1‐3 (OR 2.25 [1.43–3.56]), and negative T waves in leads V_5‐6 (OR 2.08 [1.31–3.29]) significantly predicted NSTE‐ACS. Conclusions: RBBB, S₁S₂S₃, or S₁Q₃T₃ pattern described as characteristic for APE were not helpful in the differentiation between APE and NSTE‐ACS in studied group. Coexistence of negative T waves in precordial leads V_1‐3 and inferior wall leads may suggest APE diagnosis. Ann Noninvasive Electrocardiol 2010;15(2):145–150