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Arquivos Brasileiros de Cardiologia May 2018
Topics: Arrhythmias, Cardiac; Chagas Disease; Death, Sudden, Cardiac; Electrocardiography; Humans
PubMed: 29898040
DOI: 10.5935/abc.20180081 -
Indian Pacing and Electrophysiology... 2021This study was conducted to assess the incidence of sudden cardiac death (SCD) in post myocardial infarction patients and to determine the predictive value of various...
OBJECTIVE
This study was conducted to assess the incidence of sudden cardiac death (SCD) in post myocardial infarction patients and to determine the predictive value of various risk markers in identifying cardiac mortality and SCD.
METHODS
Left ventricular function, arrhythmias on Holter and microvolt T wave alternans (MTWA) were assessed in patients with prior myocardial infarction and ejection fraction ≤ 40%. The primary outcome was a composite of cardiac death and resuscitated cardiac arrest during follow up. Secondary outcomes included total mortality and SCD.
RESULTS
Fifty-eight patients were included in the study. Eight patients (15.5%) died during a mean follow-up of 22.3 ± 6.6 months. Seven of them (12.1%) had SCD. Among the various risk markers studied, left ventricular ejection fraction (LVEF) ≤ 30% (Hazard ratio 5.6, 95% CI 1.39 to 23) and non-sustained ventricular tachycardia (NSVT) in holter (5.7, 95% CI 1.14 to 29) were significantly associated with the primary outcome in multivariate analysis. Other measures, including QRS width, heart rate variability, heart rate turbulence and MTWA showed no association.
CONCLUSIONS
Among patients with prior myocardial infarction and reduced left ventricular function, the rate of cardiac death was substantial, with most of these being sudden cardiac death. Both LVEF ≤30% and NSVT were associated with cardiac death whereas only LVEF predicted SCD. Other parameters did not appear useful for prediction of events in these patients. These findings have implications for decision making for the use of implantable cardioverter defibrillators for primary prevention in these patients.
PubMed: 33352202
DOI: 10.1016/j.ipej.2020.12.002 -
The American Journal of Forensic... Jun 2015Electromuscular incapacitating devices (EMDs) are high-voltage, low-current stimulators causing involuntary muscle contractions and sensory response. Existing evidence...
Electromuscular incapacitating devices (EMDs) are high-voltage, low-current stimulators causing involuntary muscle contractions and sensory response. Existing evidence about cardiac effects of EMD remains inconclusive. The aim of our study was to analyze electrocardiographic, echocardiographic, and microvolt T-wave alternans (MTWA) changes induced by EMD discharge.We examined 26 volunteers (22 men; median age 30 years) who underwent single standard 5-second duration exposure to TASER X26 under continuous echocardiographic and electrocardiographic monitoring. Microvolt T-wave alternans testing was performed at baseline (MTWA-1), as well as immediately and 60 minutes after EMD exposure (MTWA-2 and MTWA-3, respectively).Mean heart rate (HR) increased significantly from 88 ± 17 beats per minute before to 129 ± 17 beats per minute after exposure (P < 0.001). However, in 2 individuals, an abrupt decrease in HR was observed. In one of them, interval between two consecutive beats increased up to 1.7 seconds during the discharge. New onset of supraventricular premature beats was observed after discharge in 1 patient. Results of MTWA-1, MTWA-2, and MTWA-3 tests were positive in one of the subjects, each time in a different case.Standard EMD exposure can be associated with a nonuniform reaction of HR and followed by heart rhythm disturbances. New MTWA positivity can reflect either the effect of EMD exposure or a potential false positivity of MTWA assessments.
Topics: Adult; Bradycardia; Conducted Energy Weapon Injuries; Echocardiography, Doppler; Electrocardiography; Female; Healthy Volunteers; Humans; Male; Middle Aged; Severity of Illness Index; Young Adult
PubMed: 25710795
DOI: 10.1097/PAF.0000000000000143 -
Heart Rhythm Mar 2009Detection of microvolt levels of T-wave alternans (TWA) has been shown to be useful in identifying individuals at heightened risk for sudden cardiac death. The... (Review)
Review
Detection of microvolt levels of T-wave alternans (TWA) has been shown to be useful in identifying individuals at heightened risk for sudden cardiac death. The mechanistic bases for TWA are complex, at the cellular level involving multiple mechanisms, particularly instabilities in membrane voltage (i.e., steep action potential duration restitution slope) and disruptions in intracellular calcium cycling dynamics. The integrative factors influencing TWA at the systemic level are also multifold. We focus on three main variables: heart rate, autonomic nervous system activity, and myocardial ischemia. Clinically, there is growing interest in extending TWA testing to include ambulatory ECG monitoring as well as exercise. The former modality permits assessment of the influence of diverse provocative stimuli of daily life, including physical activity, circadian factors, mental stress, and sleep-state related disturbances in respiratory and cardiovascular function. Two major emerging concepts in clinical TWA testing are discussed: quantitative analysis of TWA level to complement the current binary classification scheme, and risk stratification of patients with preserved left ventricular function, the population with the largest absolute number of sudden cardiac deaths.
Topics: Animals; Autonomic Nervous System; Death, Sudden, Cardiac; Electrocardiography; Electrocardiography, Ambulatory; Electrophysiologic Techniques, Cardiac; Exercise Test; Heart Rate; Humans; Risk Assessment; Stroke Volume
PubMed: 19251221
DOI: 10.1016/j.hrthm.2008.11.019 -
American Journal of Physiology. Heart... May 2016One of the main constraints associated with recording sympathetic nerve activity (SNA) in both humans and experimental animals is that microvolt values reflect... (Comparative Study)
Comparative Study
One of the main constraints associated with recording sympathetic nerve activity (SNA) in both humans and experimental animals is that microvolt values reflect characteristics of the recording conditions and limit comparisons between different experimental groups. The nasopharyngeal response has been validated for normalizing renal SNA (RSNA) in conscious rabbits, and in humans muscle SNA is normalized to the maximum burst in the resting period. We compared these two methods of normalization to determine whether either could detect elevated RSNA in hypertensive rabbits compared with normotensive controls. We also tested whether either method eliminated differences based only on different recording conditions by separating RSNA of control (sham) rabbits into two groups with low or high microvolts. Hypertension was induced by 5 wk of renal clipping (2K1C), 3 wk of high-fat diet (HFD), or 3 mo infusion of a low dose of angiotensin (ANG II). Normalization to the nasopharyngeal response revealed RSNA that was 88, 51, and 34% greater in 2K1C, HFD, and ANG II rabbits, respectively, than shams (P < 0.05), but normalization to the maximum burst showed no differences. The RSNA baroreflex followed a similar pattern whether RSNA was expressed in microvolts or normalized. Both methods abolished the difference between low and high microvolt RSNA. These results suggest that maximum burst amplitude is a useful technique for minimizing differences between recording conditions but is unable to detect real differences between groups. We conclude that the nasopharyngeal reflex is the superior method for normalizing sympathetic recordings in conscious rabbits.
Topics: Action Potentials; Angiotensin II; Animals; Arterial Pressure; Baroreflex; Blood Pressure Determination; Calibration; Consciousness; Constriction; Diet, High-Fat; Disease Models, Animal; Electrodiagnosis; Heart Rate; Hypertension; Kidney; Male; Models, Animal; Muscle, Skeletal; Nasopharynx; Rabbits; Renal Artery; Reproducibility of Results; Signal Processing, Computer-Assisted; Sympathetic Nervous System; Telemetry; Time Factors
PubMed: 26921439
DOI: 10.1152/ajpheart.00866.2015 -
Frontiers in Neurology 2017Mandibular movements (MM) are considered as reliable reporters of respiratory effort (RE) during sleep and sleep disordered breathing (SDB), but MM accuracy has never...
CONTEXT
Mandibular movements (MM) are considered as reliable reporters of respiratory effort (RE) during sleep and sleep disordered breathing (SDB), but MM accuracy has never been validated against the gold standard diaphragmatic electromyography (EMG-d).
OBJECTIVES
To assess the degree of agreement between MM and EMG-d signals during different sleep stages and abnormal respiratory events.
METHODS
Twenty-five consecutive adult patients with SDB were studied by polysomnography (PSG) that also included multipair esophageal diaphragm electromyography and a magnetometer to record MM. EMG-d activity (microvolt) and MM (millimeter) amplitudes were extracted by envelope processing. Agreement between signals amplitudes was evaluated by mixed linear regression and cross-correlation function and in segments of PSG including event-free and SDB periods.
RESULTS
The average total sleep time was 370 ± 18 min and the apnea hypopnea index was 24.8 ± 5.2 events/h. MM and EMG-d amplitudes were significantly cross-correlated: median (95% CI): 0.67 (0.23-0.96). A mixed linear model showed that for each 10 µV of increase in EMG-d activity, MM amplitude increased by 0.28 mm. The variations in MM amplitudes (median range: 0.11-0.84 mm) between normal breathing, respiratory effort-related arousal, obstructive, mixed, and central apnea periods closely corresponded to those observed with EMG-d activity (median range: 2.11-8.23 µV).
CONCLUSION
MM amplitudes change proportionally to diaphragmatic EMG activity and accurately identify variations of RE during normal sleep and SDB.
PubMed: 28785240
DOI: 10.3389/fneur.2017.00353 -
Sovremennye Tekhnologii V Meditsine 2021was to develop an ECG hardware and software system for monitoring electrical instability of the myocardium and to assess the diagnostic and prognostic capabilities of...
UNLABELLED
was to develop an ECG hardware and software system for monitoring electrical instability of the myocardium and to assess the diagnostic and prognostic capabilities of this setup in a cardiology clinic.
MATERIALS AND METHODS
The Intecard 7.3 software and hardware system developed in this study makes it possible to measure fluctuations of the ECG amplitude-time parameters using the beat-to-beat mode. Intecard 7.3 evaluates a number of ECG markers that reflect electrical instability of the myocardium. Among them are the fragmented QRS complex, the spatial QRS-T angle, the T-wave alternans, the duration, and dispersion of the QT interval, the turbulence and acceleration/deceleration of the heart rhythm.Clinical trials of Intecard 7.3 were carried out with 734 patients with ischemic heart disease or cardiomyopathy and 112 healthy individuals.
RESULTS
Intecard 7.3 reliably identifies fragmented QRS complexes by detecting short spikes of <25 ms in the ascending parts of the Q, R, and S waves. The QRS-T angle is determined from the reference amplitudes of the R and T waves in leads avF, V, V, and V. Digital precision processing of the ECG signal improves its accuracy to microvolts and microseconds.The software was designed to measure the T-wave amplitude in each of 300-500 cardiobeats; T-wave alternans was estimated by the moving average method. In a typical cardiobeat, the QT dispersion was calculated based on 12 ECG leads. From the sequence of RR intervals, turbulence, and deceleration of the heart rhythm were determined.During the observation period of 5.0 [2.1; 5.9] years, 90 out of 734 patients (12.3%) experienced adverse cardiovascular events (ACVE). In this period, the myocardial electrical instability was recorded in patients with ACVE more frequently than in those without ACVE. Thus, the frequency of fragmented QRS was 72.2±4.7 vs 16.8±1.5% (p<0.01), the values of the QRS-T angle were 128 [55; 101] vs 80 [53; 121]° (p<0.001), the T-wave alternans - 36.9 [15.5; 62.1] vs 21.9 [10.2; 30.7] μV (p<0.005), the QT interval - 408 [383; 438] vs 376 [351; 400] ms (p<0.001), the QT dispersion - 76 [57; 96] vs 64 [50; 92] ms (p<0.005), respectively. In patients with ACVE, the threshold that triggers pathological rhythm turbulence was higher (>0%) than that in healthy controls (p<0.001); the deceleration of the heart rhythm was reduced from 19.2 [2.2; 38.0] to 8.8 [4.0; 16.8] ms (p<0.05).A personalized model for ACVE risk stratification has been developed. In this model, the area under the ROC curve was 0.856; sensitivity - 75%; specificity - 78%; predictive accuracy - 77%.
CONCLUSION
Using the ECG markers of myocardial electrical instability, the Intecard 7.3 system allows one to predict life-threatening ventricular tachyarrhythmias and sudden cardiac death with an accuracy of 77%. The non-invasiveness, high productivity, and reasonable cost ensure the availability of this predictive technology in all levels of healthcare.
Topics: Arrhythmias, Cardiac; Death, Sudden, Cardiac; Electrocardiography; Humans; Myocardium; Tachycardia, Ventricular
PubMed: 34796014
DOI: 10.17691/stm2020.12.6.02 -
European Journal of Heart Failure Apr 2012
Topics: Arrhythmias, Cardiac; Female; Heart Failure; Humans; Male
PubMed: 22431405
DOI: 10.1093/eurjhf/hfs032 -
Arrhythmia & Electrophysiology Review May 2016Microvolt T-wave alternans (TWA), characterised as beat-to-beat fluctuation of T-wave amplitude and morphology, is an electrophysiological phenomenon associated...
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. Microvolt TWA has been associated with cardiovascular mortality and sudden cardiac death in several clinical studies involving >14,000 subjects with reduced as well as preserved left ventricular function. 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.
PubMed: 27403292
DOI: 10.15420/aer.2015.28.1 -
American Heart Journal Oct 2013Although left ventricular ejection fraction (LVEF) is the primary determinant for sudden cardiac death (SCD) risk stratification, in isolation, LVEF is a sub-optimal... (Review)
Review
BACKGROUND
Although left ventricular ejection fraction (LVEF) is the primary determinant for sudden cardiac death (SCD) risk stratification, in isolation, LVEF is a sub-optimal risk stratifier. We assessed whether a multi-marker strategy would provide more robust SCD risk stratification than LVEF alone.
METHODS
We collected patient-level data (n = 3355) from 6 studies assessing the prognostic utility of microvolt T-wave alternans (MTWA) testing. Two thirds of the group was used for derivation (n = 2242) and one-third for validation (n = 1113). The discriminative capacity of the multivariable model was assessed using the area under the receiver-operating characteristic curve (c-index). The primary endpoint was SCD at 24 months.
RESULTS
In the derivation cohort, 59 patients experienced SCD by 24 months. Stepwise selection suggested that a model based on 3 parameters (LVEF, coronary artery disease and MTWA status) provided optimal SCD risk prediction. In the derivation cohort, the c-index of the model was 0.817, which was significantly better than LVEF used as a single variable (0.637, P < .001). In the validation cohort, 36 patients experienced SCD by 24 months. The c-index of the model for predicting the primary endpoint was again significantly better than LVEF alone (0.774 vs 0.671, P = .020).
CONCLUSIONS
A multivariable model based on presence of coronary artery disease, LVEF and MTWA status provides significantly more robust SCD risk prediction than LVEF as a single risk marker. These findings suggest that multi-marker strategies based on different aspects of the electro-anatomic substrate may be capable of improving primary prevention implantable cardioverter-defibrillator treatment algorithms.
Topics: Death, Sudden, Cardiac; Defibrillators, Implantable; Electrophysiologic Techniques, Cardiac; Humans; Primary Prevention; Risk Assessment; Tachycardia, Ventricular
PubMed: 24093856
DOI: 10.1016/j.ahj.2013.06.023