T Wave Alternans And Arrhythmogenesis In Cardiac Diseases Pdf


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Optimizing Ambulatory ECG Monitoring of T-Wave Alternans for Arrhythmia Risk Assessment

More important seems to be the selection of individuals with relatively low risk of SCD in whom ICD implantation can be safely postponed.

The aim of the study was to determine whether well-known, non-invasive parameters, such as microvolt T-wave alternans MTWA , baroreflex sensitivity BRS and short-term heart rate variability HRV , can be helpful in the identification of low-arrhythmic risk patients with ischemic left ventricular systolic dysfunction.

Well-known, non-invasive parameters, such as MTWA, BRS and short-term HRV indices may be helpful in the identification of individuals with a relatively low risk of malignant ventricular arrhythmias among patients with ischemic left ventricular systolic dysfunction; in such persons, implantation of ICD could be safely postponed.

This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: All relevant data are within the paper and its Supporting Information files. Competing interests: The authors have declared that no competing interests exist.

Sudden cardiac death SCD constitutes a significant problem in contemporary cardiology, and implementation of implantable cardioverters-defibrillators ICD to clinical practice was a breakthrough in the prevention of this condition [ 1 ]. While the necessity for ICD implantation in persons with a history of cardiac arrest due to malignant ventricular arrhythmia ventricular tachycardia [VT] or ventricular fibrillation [VF] raises no controversies, the role of these devices in the primary prevention of SCD in patients with left ventricular systolic dysfunction, i.

Furthermore, it needs to be stressed that in everyday clinical practice, the ICDs are frequently implanted in older patients who typically present with more comorbidities than the participants of clinical trials; consequently, the actual proportion of patients who do not benefit from this type of intervention may be even higher. Such approach seems to be helpful in optimization waiting lines for ICD implantation, by postponing the procedure in patients with relatively low likelihood of SCD and prioritization those at increased risk.

This might contribute to a decrease SCD numbers among patients awaiting ICD implantation, which seems to be particularly important in the case of countries with tight healthcare budgets. The aim of the study was to determine whether well-known, non-invasive parameters, such as microvolt T-wave alternans MTWA , baroreflex sensitivity BRS and short-term heart rate variability HRV , can be helpful in the identification of low-arrhythmic risk patients with ischemic left ventricular systolic dysfunction, in whom the primary prevention of SCD with ICD therapy can be safely postponed.

The protocol of the study was approved by the Local Ethics Committee at the Medical University of Gdansk, and written informed consent was obtained from all the participants. The protocol of the baseline visit included medical history, taking medications, physical examination and a lead electrocardiogram.

The study was conducted as a part of the larger research project on the risk stratification in life-threatening ventricular arrhythmias. All patients were instructed to continue their current pharmacotherapy, including beta-blockers.

Aside from the computer-guided analysis, the results were also evaluated by the physician who supervised the test. The ANS tests were performed between am and pm. Patients were instructed to continue their current pharmacotherapy, but refrain from eating for at least 4 hours, and from smoking cigarettes and drinking coffee for at least 12 hours prior to the examination.

After a minute stabilization in the supine position, resting ECG Mingograf C and beat-to-beat non-invasive arterial blood pressure Finapres , Ohmeda were recorded continuously for 10 minutes.

The signals were acquired with a PC workstation, processed with a dedicated software [ 13 ] and analysed according to the protocol described elsewhere [ 14 , 15 ]. The data on RR interval 1-ms resolution and systolic arterial pressure SAP were acquired automatically.

This method is clearly described by Pinna et al. Finally, mean heart period HP, ms value was recorded and subjected to the analysis. The patients were followed-up at the university outpatient clinic. The first visit was scheduled within 3 months of enrolment; subsequently, the patients were followed-up every 6 months, or earlier if clinically required. Due to proper programming of the ICDs, described above, we were able to exclude all potential non-persistent episodes from the analysis.

Patients with more than one VT or ICD discharge were classified as reaching the primary endpoint after the first such episode. SCD was diagnosed according to the widely accepted definition, as an unexpected death due to cardiac causes occurring within 60 minutes of symptom onset and preceded by a loss of consciousness, or as an unexpected death without witnesses occurring in a person who did not report any ailments within the last 24 hours. For safety, the sample size was set at the accuracy was improved and the error value was 8.

Since ROC curve is based on the sensitivity and specificity of a given predictor, we first determined these two parameters, then PPV and NPV, and finally, the cut-off value that most accurately distinguished between the study groups. Then, prognostic value of dichotomous variables identified based on the cut-off values was verified using univariate and multivariate Cox proportional hazard models, with the study endpoint as the outcome variable.

The probabilities of reaching the primary endpoint over time, stratified according to the MTWA result and the cut-off values for ANS parameters, were estimated using Kaplan-Meier method and compared with log-rank test. All participants of the study were recruited as outpatients S1 Table. However, the persons who reached the primary endpoint significantly more often presented with a non-negative result of MTWA test and had significantly lower LVEF Table 1. The numbers under the figure represent the number of patients subject ed to an incident risk assessment by the specified time.

While this criterion was satisfied by BRS equal to 6. The likelihood of reaching the primary endpoint during the follow-up period, stratified according to the prespecified cut-off values, is presented on Fig 2. This study included patients with ischaemic left ventricular systolic dysfunction, the most common type of heart failure [ 18 — 20 ], associated with the highest risk of arrhythmic events [ 6 , 21 ].

Patients with ischemic left ventricular systolic dysfunction are also the largest group among persons scheduled for ICD implantation within the framework of the primary prevention of SCD. Consequently, the observation that the result of MTWA test and simple non-invasive ANS parameters may be helpful in the identification of patients with the lowest risk of life-threatening ventricular arrhythmias, should be considered the principal finding of our study.

The prognostic value of MTWA was studied previously by many authors. Those discrepancies might be caused by a number of factors. One of them is continuation or discontinuation of beta-adrenolytic therapy at the time of the test.

Furthermore, the result of MTWA test lacked prognostic value in the studies in which beta-blocker was withdrawn 24 hours prior to the examination [ 30 ], as well as in the trials including only a small proportion of patients receiving beta-blockers [ 31 ].

Follow-up time is another factor that may influence the prognostic value of MTWA. This implies that if the decision to postpone ICD implantation is to be based solely on MTWA, this test should be periodically repeated whenever it yielded a negative result. According to many authors, the prognostic value of MTWA may also be influenced by the selection criteria for the study group. For example, a meta-analysis of studies involving individuals with a history of life-threatening ventricular arrhythmias demonstrated that the NPV for MTWA in this group was significantly lower than in other patient populations [ 32 , 33 ].

Likewise for MTWA, most previous studies dealing with the prognostic role of ANS indices centred around the identification of patients with the highest risk of cardiac events [ 34 — 42 ]. To the best of our knowledge, this is the first published study of this type. Due to complex pathomechanism of malignant ventricular arrhythmias, patients with these conditions require comprehensive evaluation based on multiple parameters. Published evidence suggests that the multivariate predictive models may provide more accurate estimates of long-term arrhythmic risk than any single parameter [ 34 , 41 — 45 ].

Such approach seems to be particularly justified taking into account the primary objective of this study, i. This study has a few potential limitations.

A major limitation of this work is that ICDs were implanted at the discretion of the treating physician. The only way to really eliminate this potential source of bias would randomization to ICD implantation which is difficult to perform in the light of the current guidelines or implantation all patients with ICDs in order to reduce this limitation we performed additional sub-analyzes in the ICDs group which is in supporting information S1 File which confirm the results from the whole group.

However, searching for the possibility of identifying patients with minimal risk of arrhythmia, the Authors found that caution and repetitive tests every 12 months may be considered as helpful to postpone MTWA implantation especially in the patients with present temporary contraindications or in countries with poor economical situation.

Additionally, our study is singe-centre study, with small sample size and variety endpoints, therefore the presented findings should be considered only as preliminary results.

Well-known, non-invasive parameters, such as MTWA, BRS and short-term HRV indices may be helpful in the identification of individuals with a relatively low risk of malignant ventricular arrhythmia among patients with ischemic left ventricular systolic dysfunction; in such persons, implantation of ICD could be safely postponed.

Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field. Conclusion Well-known, non-invasive parameters, such as MTWA, BRS and short-term HRV indices may be helpful in the identification of individuals with a relatively low risk of malignant ventricular arrhythmias among patients with ischemic left ventricular systolic dysfunction; in such persons, implantation of ICD could be safely postponed.

Funding: The authors received no specific funding for this work. Introduction Sudden cardiac death SCD constitutes a significant problem in contemporary cardiology, and implementation of implantable cardioverters-defibrillators ICD to clinical practice was a breakthrough in the prevention of this condition [ 1 ].

Materials and methods The protocol of the study was approved by the Local Ethics Committee at the Medical University of Gdansk, and written informed consent was obtained from all the participants. MTWA testing All patients were instructed to continue their current pharmacotherapy, including beta-blockers. Follow-up The patients were followed-up at the university outpatient clinic.

Results Clinical characteristics of the studied patients All participants of the study were recruited as outpatients S1 Table. Download: PPT. Table 1. Table 2. Distribution of clinical events contributing to the primary end points. Table 3. Fig 1. Table 4. Negative predictive value of the study parameters. Fig 2. Table 5. Prognostic accuracy of the study parameters prespecified cut-off values as the predictors of the EVENT during the follow-up. Table 6. Prognostic accuracy of the composite measures including prespecified cut-off values as the predictors of the EVENT during the follow-up.

Discussion This study included patients with ischaemic left ventricular systolic dysfunction, the most common type of heart failure [ 18 — 20 ], associated with the highest risk of arrhythmic events [ 6 , 21 ]. Prognostic value of ANS indices in the identification of low-arrhythmic risk patients Likewise for MTWA, most previous studies dealing with the prognostic role of ANS indices centred around the identification of patients with the highest risk of cardiac events [ 34 — 42 ].

Prognostic value of MTWA analysed jointly with ANS parameters in the identification of low-arrhythmic risk patients Due to complex pathomechanism of malignant ventricular arrhythmias, patients with these conditions require comprehensive evaluation based on multiple parameters. Study limitations This study has a few potential limitations. Conclusion Well-known, non-invasive parameters, such as MTWA, BRS and short-term HRV indices may be helpful in the identification of individuals with a relatively low risk of malignant ventricular arrhythmia among patients with ischemic left ventricular systolic dysfunction; in such persons, implantation of ICD could be safely postponed.

Supporting information. S1 Table. Data sets. S1 File. Additional sub-analyzes in the ICDs group. References 1. Eur H J. View Article Google Scholar 2. The need to modify patient selection to improve the benefits of implantable cardioverter-defibrillator for primary prevention of sudden death in non-ischaemic dilated cardiomyopathy.

Long-term benefit of primary prevention with an implantable cardioverter-defibrillator: an extended 8-year follow-up study of the Multicenter Automatic Defibrillator Implantation Trial II. N Engl J Med. Utility of current risk stratification tests for predicting major arrhythmic events after myocardial infarction.

T-Wave Alternans and Arrhythmogenesis in Cardiac Diseases

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Microvolt T-wave alternans MTWA , which reflects electrical dispersion of repolarization, is known to be associated with arrhythmia or sudden cardiac death in high risk patients. In this study we investigated the relationship between MTWA and postoperative mortality in cardiac surgery patients. Electrocardiogram, official national data and electric chart were analysed to provide in-hospital and mid-term outcome.

This open-access and indexed, peer-reviewed journal publishes review articles ideal for the busy physician. Microvolt T-wave alternans TWA , characterised as beat-to-beat fluctuation of T-wave amplitude and morphology, is an electrophysiological phenomenon associated clinically with impending ventricular arrhythmias and is an important marker of arrhythmia risk. Currently, two main methods for the detection of TWA exist, namely, the spectral method and the time-domain modified moving average method; both are discussed in this review. Although TWA appears to be a useful marker of susceptibility for lethal ventricular arrhythmias and cardiovascular death, so far there is no sufficient evidence from randomised clinical trials to support its use in guiding therapy. However, several ongoing trials are expected to provide more information about the clinical use of TWA testing.

Metrics details. The occurrence of T-wave alternans in electrocardiographic signals was recently linked to susceptibility to ventricular arrhythmias and sudden cardiac death. Thus, by detecting and comprehending the origins of T-wave alternans, it might be possible to prevent such events. Here, we simulated T-wave alternans in a computer-generated human heart model by modulating the action potential duration and amplitude during the first part of the repolarization phase. We hypothesized that changes in the intracardiac alternans patterns of action potential properties would differentially influence T-wave alternans measurements at the body surface. Body surface potential maps and lead electrocardiographic signals were then computed.


PDF | T-wave alternans, a manifestation of repolarization alternans at the cellular level, is associated with lethal cardiac arrhythmias and.


Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. DOI: Qu and Y.

T-wave alternans, a manifestation of repolarization alternans at the cellular level, is associated with lethal cardiac arrhythmias and sudden cardiac death.

Introduction

Click on image for details. Long QT syndrome LQTS is a congenital disorder characterized by prolongation of QT interval in the electrocardiogram ECG and a propensity to develop ventricular arrhythmias, which may lead to syncope, cardiac arrest or sudden death. T-wave alternans TWA , a phenomenon of beat-to-beat variability in the repolarization phase of the ventricles, has been closely associated with an increased risk of ventricular tachyarrhythmic events VTE and sudden cardiac death SCD. Correspondence Address : Dr. Video-assisted thoracoscopic left cardiac sympathetic denervation: A reliable minimally invasive approach for congenital long-QT syndrome. Ann Thorac Surg ; Schwartz PJ, Malliani A.

ГЛАВА 123 Техник с бледным лицом подбежал к подиуму. - Туннельный блок сейчас рухнет. Джабба повернул голову к экрану ВР. Атакующие линии рвались вперед, они находились уже на волосок от пятой, и последней, стены, Последние минуты существования банка данных истекали. Сьюзан отгородилась от царившего вокруг хаоса, снова и снова перечитывая послание Танкадо. PRIME DIFFERENCE BETWEEN ELEMENTS RESPONSIBLE FOR HIROSHIMA AND NAGASAKI ГЛАВНАЯ РАЗНИЦА МЕЖДУ ЭЛЕМЕНТАМИ, ОТВЕТСТВЕННЫМИ ЗА ХИРОСИМУ И НАГАСАКИ - Это даже не вопрос! - крикнул Бринкерхофф.  - Какой же может быть ответ.

Звуки шли сверху. Он поднял глаза на видеомониторы, и у него закружилась голова. Одна и та же картинка смотрела на него со всех двенадцати мониторов наподобие какого-то извращенного балета. Вцепившись руками в спинку стула, Бринкерхофф в ужасе смотрел на экраны. - Чед? - услышал он голос у себя за спиной. Обернувшись, Бринкерхофф начал всматриваться в темноту. Мидж как ни чем не бывало стояла в приемной возле двойной двери директорского кабинета и протягивала к нему руку ладонью вверх.

Внешний щит, исчезающий на наших глазах, - открытый главный компьютер. Этот щит практически взломан.

Если он использует адрес университета или корпорации, времени уйдет немного.  - Она через силу улыбнулась.  - Остальное будет зависеть от. Сьюзан знала, что остальное - это штурмовая группа АНБ, которая, перерезав электрические провода, ворвется в дом с автоматами, заряженными резиновыми пулями.

 - Ему не стоило напоминать о поразительной способности Мидж Милкен предчувствовать беду.  - Мидж, - взмолился он, - я знаю, что ты терпеть не можешь Стратмора, но… - Это не имеет никакого значения! - вспылила.  - Первым делом нам нужно убедиться, что Стратмор действительно обошел систему Сквозь строй.

2 Comments

Heather C.
20.04.2021 at 09:24 - Reply

More important seems to be the selection of individuals with relatively low risk of SCD in whom ICD implantation can be safely postponed.

Emiliano V.
26.04.2021 at 19:41 - Reply

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