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Annals of Noninvasive Electrocardiology... Jul 2019The aim of study was to investigate effects of beta-blockade on microvolt T-wave alternans (TWA), a precursor of lethal arrhythmia, in patients with long QT syndrome...
BACKGROUND
The aim of study was to investigate effects of beta-blockade on microvolt T-wave alternans (TWA), a precursor of lethal arrhythmia, in patients with long QT syndrome (LQTS).
METHODS
Eleven consecutive LQTS patients, types 1 (n = 6), 3 (n = 2), and "non-1, non-2, non-3" (n = 3) were enrolled. All patients underwent 24-hr continuous 12-lead ECG monitoring before and after initiation of beta-blockade therapy. TWA was measured using the modified moving average method.
RESULTS
Seven (63.6%) of the 11 patients studied were symptomatic, with history of cardiac arrest or documented Torsade de Pointes (TdP) in 4 and syncope in three patients. After a median follow-up of 34 months, beta-blockade reduced the number of symptomatic patients to 1 with TdP (p < 0.02), in whom TdP frequency decreased from 25 events/60 months (0.42 event/month) to seven events/69 months (0.1 event/month). In association with this reduction in symptoms, peak TWA decreased by 47% in the cohort after a median of eight months of beta-blockade therapy [from 95 (74-130) to 50 (39.5-64.5) µV, p = 0.01]. All patients exhibited TWA ≥42 µV before beta-blockade therapy, which eliminated these episodes in four patients. Daily frequency of TWA ≥42 µV episodes decreased by 87% [from 15 (6-26) to 2 (0-5) episodes/day, p = 0.009].
CONCLUSIONS
This study is limited by the small sample size and is mainly hypothesis generating. TWA monitoring deserves further evaluation as a risk marker and a guide to therapy in LQTS patients in future large-scale studies.
Topics: Adolescent; Adrenergic beta-Antagonists; Adult; Arrhythmias, Cardiac; Child; Child, Preschool; Electrocardiography, Ambulatory; Female; Follow-Up Studies; Humans; Infant; Long QT Syndrome; Male; Middle Aged; Young Adult
PubMed: 30729628
DOI: 10.1111/anec.12640 -
Anatolian Journal of Cardiology Jan 2019
Topics: Arrhythmias, Cardiac; Cardiomyopathy, Hypertrophic; Death, Sudden, Cardiac; Electrocardiography, Ambulatory; Humans
PubMed: 30587708
DOI: 10.14744/AnatolJCardiol.2018.92160 -
PloS One 2018This paper presents an open-source package developed in Python that controls and drives a programmable Josephson array to synthesize dc and ac quantum-accurate voltages....
This paper presents an open-source package developed in Python that controls and drives a programmable Josephson array to synthesize dc and ac quantum-accurate voltages. Programmable arrays are devices subdivided into independent subsections, each counting a number of series connected Josephson junctions that follows a binary sequence (1, 2, 4, 8, …) to control the output voltage. Our software allows to independently measure the current-voltage characteristics of each subsection by means of a set of arbitrary waveform generators and a nanovoltmeter that measures the voltage across the whole array with high sensitivity. A quantization test tool is also provided to check with sub-microvolt resolution whether the array is operating on its quantum margins. The code is modular and easily expandable with the support of many libraries, allowing prompt reconfiguration for different calibration and testing purposes. It is aimed at being a starting point for cooperation between National Metrology Institutes towards the realization of a shared quantum voltage calibration infrastructure.
Topics: Access to Information; Calibration; Computer Simulation; Electrical Equipment and Supplies; Electricity; Quantum Theory; Software
PubMed: 30557380
DOI: 10.1371/journal.pone.0209246 -
Annals of Noninvasive Electrocardiology... Mar 2019Microvolt T-wave alternans (MTWA) testing is a beat-to-beat fluctuation in the amplitude of T wave. We investigated whether: (a) MTWA can be new non-invasive tool for...
TWARMI pilot trial: The value and optimal criteria of microvolt T-wave alternans in the diagnosis of reversible myocardial ischemia in patients without structural cardiac disease.
AIMS
Microvolt T-wave alternans (MTWA) testing is a beat-to-beat fluctuation in the amplitude of T wave. We investigated whether: (a) MTWA can be new non-invasive tool for detection of reversible ischemia in patients with suspected CAD without structural heart disease, (b) MTWA can detect ischemia earlier and with greater test accuracy compared with exercise ECG ST-segment testing, and (c) threshold value of MTWA and heart rate at which the alternans is estimated can be different compared to standard values.
METHODS
A total of 101 patients with suspected stable coronary disease, but without structural heart disease, were included. Echocardiography, exercise ECG test, MTWA with classical and modified threshold alternans values, and coronary angiography were performed.
RESULTS
About 33.3% patients had a false-positive result on exercise ECG test. The sensitivity of exercise ECG ST-segment test in the detection of coronary artery disease was 97.8%, and the specificity was 42.5% (DOR 33.89). In a group of angiographically positive patients, standard MTWA accurately identified 60% of patients, while 40% had a false-negative result. About 91.8% patients with negative angiography result were accurately identified with 8.2% false positives. The sensitivity of MTWA was 59.61% and specificity 91.83%. Best ratio of sensitivity and specificity (86.53% and 95.91%, DOR 151.06) had modified criteria for positive MTWA (MTWA >1.5 µV at heart rate 115-125/min).
CONCLUSIONS
This study showed that MTWA can be the new non-invasive tool for the detection of reversible ischemia in patients with suspected CAD without structural heart disease. Also, MTWA can detect ischemia earlier and with greater accuracy compared with exercise ECG testing.
Topics: Aged; Cohort Studies; Coronary Angiography; Echocardiography, Doppler; Electrocardiography; Exercise Test; Female; Heart Rate; Humans; Male; Middle Aged; Myocardial Ischemia; Pilot Projects; Prospective Studies; Sensitivity and Specificity; Severity of Illness Index
PubMed: 30383318
DOI: 10.1111/anec.12610 -
Scientific Reports Oct 2018Weak electric currents are induced in moving seawater by cutting the geomagnetic fields. These electric currents can produce measurable electromagnetic fields that may...
Weak electric currents are induced in moving seawater by cutting the geomagnetic fields. These electric currents can produce measurable electromagnetic fields that may be used for some purposes such as monitoring of ocean internal waves. This article is aimed at presenting the procedure to calculate the electromagnetic fields owing to the wake raised by an undersea moving slender body. A pair of Havelock point sources are introduced to model the moving body, which generate the similar wake at places far from the body. The ocean is taken to be of finite-depth with density stratification due to thermocline. Three distinct forms of water-flow wake can be identified, the free-surface Kelvin wake, the internal interfacial wake, and the localized volume wake. The electric currents evoked by the motional wake may produce observable electromagnetic fields, which may be solved using rigorous electromagnetic field theory. At the sea level, the magnitudes of the induced electric field and magnetic field are on the order of a few microvolts per meter and one nano-Tesla, respectively, which are appreciable in terms of nowadays marine electric and magnetic sensors.
PubMed: 30279424
DOI: 10.1038/s41598-018-32789-1 -
Sensors (Basel, Switzerland) Jul 2018The increased popularity of brain-computer interfaces (BCIs) has created a new demand for miniaturized and low-cost electroencephalogram (EEG) acquisition devices for...
The increased popularity of brain-computer interfaces (BCIs) has created a new demand for miniaturized and low-cost electroencephalogram (EEG) acquisition devices for entertainment, rehabilitation, and scientific needs. The lack of scientific analysis for such system design, modularity, and unified validation tends to suppress progress in this field and limit supply for new low-cost device availability. To eliminate this problem, this paper presents the design and evaluation of a compact, modular, battery powered, conventional EEG signal acquisition board based on an ADS1298 analog front-end chip. The introduction of this novel, vertically stackable board allows the EEG scaling problem to be solved by effectively reconfiguring hardware for small or more demanding applications. The ability to capture 16 to 64 EEG channels at sample rates from 250 Hz to 1000 Hz and to transfer raw EEG signal over a Bluetooth or Wi-Fi interface was implemented. Furthermore, simple but effective assessment techniques were used for system evaluation. While conducted tests confirm the validity of the system against official datasheet specifications and for real-world applications, the proposed quality verification methods can be further employed for analyzing other similar EEG devices in the future. With 6.59 microvolts peak-to-peak input referred noise and a −97 dB common mode rejection ratio in 0⁻70 Hz band, the proposed design can be qualified as a low-cost precision cEEG research device.
Topics: Brain-Computer Interfaces; Electric Power Supplies; Electroencephalography; Equipment Design; Humans; Signal Processing, Computer-Assisted
PubMed: 29970846
DOI: 10.3390/s18072140 -
Arquivos Brasileiros de Cardiologia May 2018
Topics: Arrhythmias, Cardiac; Chagas Disease; Death, Sudden, Cardiac; Electrocardiography; Humans
PubMed: 29898040
DOI: 10.5935/abc.20180081 -
PloS One 2018The role of implantable cardioverter-defibrillator (ICD) placement in the primary prevention of sudden cardiac death (SCD) in all consecutive patients with left... (Clinical Trial)
Clinical Trial
Microvolt T-wave alternans and autonomic nervous system parameters can be helpful in the identification of low-arrhythmic risk patients with ischemic left ventricular systolic dysfunction.
INTRODUCTION
The role of implantable cardioverter-defibrillator (ICD) placement in the primary prevention of sudden cardiac death (SCD) in all consecutive patients with left ventricular ejection fraction (LVEF) ≤ 35% is still a matter of hot debate due to the fact that the population of these patients is highly heterogeneous in terms of the SCD risk. Nevertheless, reduced LVEF is still the only established criterion during qualification of patients for ICD implantation in the primary prevention of SCD, therefore identification of persons with particularly high risk among patients with LVEF ≤35% is currently of lesser importance. 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.
METHODS
In 141 patients with coronary artery disease and LVEF ≤ 35%, MTWA testing, as well as BRS and short-term HRV parameters, were analysed. During 34 ± 13 months of follow-up 37 patients had arrhythmic episode (EVENT): SCD, non-fatal sustained ventricular arrhythmia (ventricular tachycardia [VT] or ventricular fibrillation [VF]), or adequate high-voltage ICD intervention (shock) due to a rapid ventricular arrhythmia ≥200/min. LVEF, non-negative MTWA (MTWA_non-neg), BRS and low frequency power in normalized units (LFnu) turned out to be associated with the incidence of EVENT in univariate Cox analysis. The cut-off values for BRS and LFnu that most accurately distinguished between patients with and without EVENT were 3 ms/mmHg and 23, respectively. The only variable that provided 100% negative predictive value (NPV) for EVENT was negative MTWA result (MTWA_neg), but solely for initial 12 months of the follow-up; the NPVs for other potential predictors of the EVENT were lower. The cut-off values for BRS and LFnu that provide 100% NPV for EVENT during 12 and 24 months were higher: 6.0 ms/mmHg and 73 respectively, but the gain in the NPV occurred at an expense of the number of identified patients. However, the number of identified non-risk patients turned out to be higher when the predictive model included MTWA_neg and the lower cut-off values for ANS parameters: 100% NPV for 12 and 24 months of follow-up was obtained for combination MTWA_neg and BRS ≥ 3 ms/mmHg, for combination MTWA_neg and LFnu ≥ 23 100% NPV was obtained for 12 months.
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.
Topics: Aged; Baroreflex; Cardiovascular Agents; Death, Sudden, Cardiac; Defibrillators, Implantable; Electrocardiography; Female; Follow-Up Studies; Heart Rate; Humans; Male; Middle Aged; Myocardial Ischemia; Predictive Value of Tests; Prognosis; Proportional Hazards Models; Prospective Studies; Reflex, Abnormal; Risk Assessment; Systole; Tachycardia, Ventricular; Ventricular Dysfunction, Left; Ventricular Fibrillation
PubMed: 29723261
DOI: 10.1371/journal.pone.0196812 -
PloS One 2018Pulmonary arterial hypertension (PAH) is a rare disorder with unfavorable prognosis despite implementation of specific PAH-oriented therapy. The aim of the study was to... (Observational Study)
Observational Study
OBJECTIVES
Pulmonary arterial hypertension (PAH) is a rare disorder with unfavorable prognosis despite implementation of specific PAH-oriented therapy. The aim of the study was to define predictors of poor prognosis in patients from one center treated according to the Polish National Health Fund program.
PATIENTS AND METHODS
Forty-seven consecutive patients (30 women; aged 39±17 years) with PAH diagnosis were enrolled to the study. Clinical assessment, laboratory measurements, electrocardiogram, echocardiography, 6-minute walk test, 24-hour Holter monitoring, cardiopulmonary exercise test and microvolt T-wave alternans test were performed during routine visits. Eight patients died during 2.6±1.7 years follow-up.
RESULTS
Parametrs which differentiated patients who died were brain natriuretic peptide (BNP) concentration ≥330 pg/mL (sensitivity 88%, specificity 92%, area under the ROC curve [AUC] 0.92); bilirubin concentration ≥1.2 mg/dL (sensitivity 88%, specificity 81%, AUC 0.85); right atrial area ≥21 cm2 (sensitivity 86%, specificity 69%, AUC 0.84), right ventricular (RV) dimension in the apical 4-chamber view ≥47 mm (sensitivity 86%, specificity 86%, AUC 0.85) and RV to left ventricular diastolic diameter ratio ≥1.5 (sensitivity 83%, specificity 84%; AUC 0.85). In multivariate analysis, independent predictors of mortality were higher BNP (p = 0.04) and bilirubin level (p = 0.03), higher right atrial area (p = 0.02) and lower tricuspid annular plane systolic excursion (p = 0.03).
CONCLUSIONS
In PAH patients treated with specific PAH-oriented therapy right atrial enlargement, impaired right ventricular systolic function, as well as increased BNP and bilirubin concentration was associated with an increased mortality risk.
Topics: Adult; Echocardiography; Exercise Test; Female; Heart; Humans; Hypertension, Pulmonary; Male; Middle Aged; Prospective Studies; ROC Curve
PubMed: 29684090
DOI: 10.1371/journal.pone.0193245 -
Arquivos Brasileiros de Cardiologia May 2018Sudden cardiac death is the most frequent death mechanism in Chagas disease, responsible for 55% to 65% of the deaths of patients with chronic Chagas cardiomyopathy... (Observational Study)
Observational Study
BACKGROUND
Sudden cardiac death is the most frequent death mechanism in Chagas disease, responsible for 55% to 65% of the deaths of patients with chronic Chagas cardiomyopathy (CCC). The most often involved electrophysiological mechanisms are ventricular tachycardia and ventricular fibrillation. The implantable cardioverter defibrillator (ICD) has a beneficial role in preventing sudden death due to malignant ventricular arrhythmias, and, thus the correct identification of patients at risk is required. The association of microvolt T-wave alternans (MTWA) with the appearance of ventricular arrhythmias has been assessed in different heart diseases. The role of MTWA is mostly unknown in patients with CCC.
OBJECTIVES
To evaluate the association between MTWA and the occurrence of malignant ventricular arrhythmias in patients with CCC.
METHOD
This is a case-control study including patients with CCC and ICD, with history of malignant ventricular arrhythmias (case group), and patients with CCC and no history of those arrhythmias (control group). The MTWA test results were classified as negative and non-negative (positive and indeterminate). The significance level adopted was a = 0.05.
RESULTS
We recruited 96 patients, 45 cases (46.8%) and 51 controls (53.1%). The MTWA test was non-negative in 36/45 cases (80%) and 15/51 controls (29.4%) [OR = 9.60 (95%CI: 3.41 - 27.93)]. After adjustment for known confounding factors in a logistic regression model, the non-negative result continued to be associated with malignant ventricular arrhythmias [OR = 5.17 (95%CI: 1.05 - 25.51)].
CONCLUSION
Patients with CCC and history of malignant ventricular arrhythmias more often have a non-negative MTWA test as compared to patients with no history of arrhythmia.
Topics: Arrhythmias, Cardiac; Case-Control Studies; Chagas Disease; Death, Sudden, Cardiac; Defibrillators, Implantable; Electrocardiography; Female; Humans; Male; Middle Aged; Risk Factors; Survival Analysis; Tachycardia, Ventricular
PubMed: 29641645
DOI: 10.5935/abc.20180056