Rhythm, QT Prolongation. NCBI Bookshelf.
Schamroth L. Basic principles. In: Schamroth C, editor. An introduction to Electrocardiography.
Delhi: Wiley India; J Cardiovasc Electrophysiol ; Inaccurate electrocardiographic interpretation of long QT: The majority of physicians cannot recognize a long QT when they see one. Heart Rhythm ; QT interval and drug therapy Clinical review from drug and therapeutics bulletin. BMJ ;i Assessment of prolonged QT and JT intervals in ventricular conduction defects.
Am J Cardiol ; A new experimentally validated formula to calculate the QT interval in the presence of left bundle branch block holds true in the clinical setting. Ann Noninvasive Electrocardiol ; doi Cutting off half of QRS duration can cause overcorrection of QT interval in left bundle branch block.
Ann Noninvasive Electrocardiol ; J Electrocardiol ;37 Suppl: Bazett HC.
An analysis of the time relations of electrocardiogram. Heart ; Fridericia LS. The systole duration in the electrocardiogram in normal people and in people with heart disease. Acta Med Scand ; Rautaharju PM. QT and dispersion of ventricular repolarization: The greatest fallacy in electrocardiography in the s. QJM ; QT-RR relationship in healthy subjects exhibits substantial intersubject variability and high intrasubject stability.
Mechanisms, risk factors, and management of acquired long QT syndrome: A comprehensive review. ScientificWorldJournal ; Correlation of QT interval correction methods during atrial fibrillation and sinus rhythm. Prevention of torsade de pointes in hospital settings: A scientific statement from the American Heart Association and the American College of Cardiology Foundation. Eur Heart J ; Roden DM. Predicting drug-induced QT prolongation and torsades de pointes. J Physiol ; Variability of the QT measurement in healthy men, with implications for selection of an abnormal QT value to predict drug toxicity and proarrhythmia.
Diurnal pattern of QTc interval: How long is prolonged? Possible relation to circadian triggers of cardiovascular events. QT dispersion: An indication of arrhythmia risk in patients with long QT intervals. Br Heart J ; QT dispersion and mortality after myocardial infarction.
Lancet ; Malik M, Batchvarov VN. Measurement, interpretation and clinical potential of QT dispersion.
The Assessment of Tp-e Interval and Tp-e/QT Ratio in Patients With Systemic Sclerosis
Repolarization heterogeneity: Beyond the QT interval. J Am Heart Assoc ;5. Molnar J, Somberg JC. The dynamics of QT dispersion. Diagnosis of cardiac arrhythmias. Libby P, Bonow RO, editors. Electrophysiological mechanisms of long and short QT syndromes. Int J Cardiol Heart Vasc ; Genetics of cardiac arrhythmias.
Risk for life-threatening cardiac events in patients with genotype-confirmed long-QT syndrome and normal-range corrected QT intervals.
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Heart Rhythm ;e Images in cardiovascular medicine. Drug-induced long-QT syndrome with macroscopic T-wave alternans. Circulation ;e The response of the QT interval to the brief tachycardia provoked by standing: A bedside test for diagnosing long QT syndrome. Schwartz PJ, Crotti L. QTc behavior during exercise and genetic testing for the long-QT syndrome. Derivation and validation of a simple exercise-based algorithm for prediction of genetic testing in relatives of LQTS probands. J Electrocardiol ; Therapy for cardiac arrhythmias.
Pre-clinical and clinical predictors of arrhythmic risk: the need for new indices
Prevalence and prognostic significance of long QT interval in patients with acute coronary syndrome: Review of the literature. J Cardiovasc Nurs ; Drug induced QT prolongation and torsades de pointes. Predicting the unpredictable: Drug-induced QT prolongation and torsades de pointes. Safety of oral dofetilide for rhythm control of atrial fibrillation and atrial flutter. Circ Arrhythm Electrophysiol ; Clinical safety profile of sotalol in patients with arrhythmias.
Am J Cardiol ;AA. The FDA extended warning for intravenous haloperidol and torsades de pointes: How should institutions respond? J Hosp Med ;5:E The genetics underlying acquired long QT syndrome: Impact for genetic screening.
Practical Use of T Wave Morphology Assessment | SpringerLink
Pharmacogenetics of drug-induced QT interval prolongation: An update. Drug Saf ; It has been postulated that in the presence of cardiac abnormalities the complexity of the vectorocardiographic loops increases and their spatial orientation is less clearly determined. Therefore, the TCRT technology, by integrating all possible directions of the vectrocardiographic loops as average cosine of all angles, is likely to reflect more accurately the repolarization heterogeneity aberration and improve the risk assessment.
Future prospective studies should examine the potential utility of serial assessments of TCRT to characterize the evolution of uremic cardiomyopathy and identify the transition to high risk profiles. In contrast to the two previous studies in HD patients de Bie et al. However the aforementioned studies de Bie et al. The third study Poulikakos et al. We previously reported that patients recruited to our study had longer survival compared to non-participants Chiu et al.
Furthermore, our prevalent dialysis patients were followed up annually with detailed cardiovascular and clinical assessment and it is possible that such close cardiovascular monitoring enabled early identification and management of cardiovascular disease. Two previous studies have explored the association between echocardiographic abnormalities and QRS-T angle in dialysis patients.
In the study by Tereshchenko et al. In another study of 94 HD patients de Bie et al. Speckle tracking echocardiography was not included in either study. The association between repolarization heterogeneity and cardiac function that we observe in HD patients may represent the epiphenomenon of underlying myocardial fibrosis leading to both electrical and functional aberrations or it may reflect the effect of repolarization heterogeneity on cardiac function via inducing heterogeneity and dysynchrony in mechanical contraction within the different myocardial layers.
An association between repolarization heterogeneity and mechanical contraction assessed by GLS, in the absence of underlying myocardial fibrosis, has been shown in observational studies in subjects with long QT syndrome Haugaa et al. Interestingly, although selected markers of myocardial fibrosis, such as mRNA of TGF-b and micro RNA 21, were upregulated in CKD-rats compared to control rats there was no statistically significant difference in myocardial fibrosis between the two groups.
In this animal model the increased vulnerability to arrhythmias preceded the development of fibrosis and this finding supports a causative link between altered electrophysiological properties and malignant arrhythmias independent of myocardial fibrosis. However, the effects of electrophysiological aberrations upon the myocardial mechanics were not assessed in this study. The potential relative contribution of repolarization heterogeneity on cardiac function and its relationship with underlying myocardial fibrosis cannot be established from our observational study.
Future research to elucidate the link between repolarization heterogeneity and mechanical dysfunction may have important implications in understanding the pathophysiology of uremic cardiomyopathy and in optimizing risk assessment in HD patients. The limitations of this study including the relatively small sized population and recruitment selection bias leading to lower mortality have previously been described Chiu et al.
Due to the small number of arrhythmic deaths, we did not have the statistical power to investigate associations of TCRT with sudden cardiac death and cardiac arrest separately. Also, we did not manage to investigate follow up ECGs in a large number of patients for the longitudinal ECG analysis thus limiting the scope of the statistical analysis for the longitudinal changes. In conclusion, our study has demonstrated that QRS-T angle calculated by TCRT, an electrocardiographic marker of repolarization heterogeneity that can be derived from standard 10 s ECGs, carries independent prognostic significance for cardiac mortality risk in our HD cohort and it is correlated with GLS.
Further prospective studies with longitudinal cardiovascular monitoring including a combination of electrophysiologic and cardiac structural and functional assessment from patients with earlier stages of chronic kidney disease are required to characterize the determinants of the progression of uremic cardiomyopathy and identify potential opportunities for interventions. In light of the consistently strong risk prediction signal of the QRS-T angle in the renal population we suggest that standardization of the assessment of QRS-T angle is important to enable identification of cut-off points indicating high risk to be used in routine clinical practice.
SS and DG collected, analyzed, and interpreted the data, drafted the article, and contributed to statistical expertise. KH processed ECG signal and drafted the article. MM conceived and designed the study, processed the ECG signal, interpreted the data, and critically revised the article. PK conceived and designed the study, interpreted the data, and critically revised the article. DP conceived and designed the work, analyzed and interpreted the data, contributed to statistical expertise, and critically revised the article. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Acar, B. Spatial, temporal and wavefront direction characteristics of lead T-wave morphology. Al-Khatib, S. Heart Rhythm 15, e—e Global ECG measures and cardiac structure and function: the aric study atherosclerosis risk in communities. Arrhythm Electrophysiol.
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