ECG T-Wave Morphologic Variations Predict Ventricular Arrhythmic Risk in Low- and Moderate-Risk Populations

Prognostic significance of beat-to-beat variability of spatial heterogeneity of repolarization analyzed from a 5-minute resting electrocardiogram in coronary artery disease

BACKGROUND

Data on the prognostic significance of temporal variability of spatial heterogeneity of electrocardiographic repolarization in coronary artery disease (CAD) are limited.

OBJECTIVE

The purpose of this study was to evaluate the prognostic value of temporal variability of T-wave morphology analyzed from a 5-minute resting electrocardiogram in CAD.

METHODS

The standard deviation (SD) of T-wave morphology dispersion (TMD-SD) and the SD of total cosine R-to-T were analyzed on a beat-to-beat basis from a 5-minute period of the standard resting 12-lead electrocardiogram obtained before the clinical stress test in 1702 patients with angiographically verified CAD and well-preserved left ventricular function.

RESULTS

During an average of 8.7 ± 2.2 years of follow-up, 60 patients experienced sudden cardiac death/arrest (SCD/SCA) (3.5%), 69 patients nonsudden cardiac death (NSCD) (4.1%), and 161 patients noncardiac death (9.5%). TMD-SD was significantly higher in patients who experienced SCD/SCA than in other patients (1.72 ± 2.00 vs 1.12 ± 1.75; P = .01) and higher in patients who succumbed to NSCD than in other patients (1.57 ± 1.74 vs 1.12 ± 1.76; P = .04), but it did not differ significantly between patients who experienced noncardiac death and those without such an event (1.16 ± 1.42 vs 1.14 ± 1.79; P = .86). In the Cox multivariable hazards model, TMD-SD retained its significant association with the risk of SCD/SCA (hazard ratio 1.119; 95% confidence interval 1.015-1.233; P = .024) but not with the risk of NSCD (hazard ratio 1.089; 95% confidence interval 0.983-1.206; P = .103).

CONCLUSION

TMD-SD is independently associated with the long-term risk of SCD/SCA in patients with CAD.

T-wave morphology abnormalities in the STREAM stage 1 trial

BACKGROUND

Shorter regimens for drug-resistant tuberculosis (DR-TB) have non-inferior efficacy compared with longer regimens, but QT prolongation is a concern. T-wave morphology abnormalities may be a predictor of QT prolongation.

RESEARCH DESIGN AND METHODS

STREAM Stage 1 was a randomized controlled trial in rifampicin-resistant TB, comparing short and long regimens. All participants had regular ECGs. QT/QTcF prolongation (≥500 ms or increase in ≥60 ms from baseline) was more common on the short regimen which contained high-dose moxifloxacin and clofazimine. Blinded ECGs were selected from the baseline, early (weeks 1-4), and late (weeks 12-36) time points. T-wave morphology was categorized as normal or abnormal (notched, asymmetric, flat-wave, flat peak, or broad). Differences between groups were assessed using Chi-Square tests (paired/unpaired, as appropriate).

RESULTS

Two-hundred participants with available ECGs at relevant times were analyzed (QT prolongation group n = 82; non-prolongation group n = 118). At baseline, 23% (45/200) of participants displayed abnormal T-waves, increasing to 45% (90/200, p < 0.001) at the late time point. Abnormalities were more common in participants allocated the Short regimen (75/117, 64%) than the Long (14/38, 36.8%, p = 0.003); these occurred prior to QT/QTcF ≥500 ms in 53% of the participants (Long 2/5; Short 14/25).

CONCLUSIONS

T-wave abnormalities may help identify patients at risk of QT prolongation on DR-TB treatment.

TRIAL REGISTRATION

The trial is registered at ClinicalTrials.gov (CT.gov identifier: NCT02409290). Current Controlled Trial number, ISRCTN78372190.

Early exposure to mercury and cardiovascular function of seven-year old children in Guadeloupe (French West Indies)

BACKGROUND

The cardiotoxicity of prenatal exposure to mercury has been suggested in populations having regular contaminated seafood intake, though replications in the literature are inconsistent.

METHODS

The Timoun Mother-Child Cohort Study was set up in Guadeloupe, an island in the Caribbean Sea where seafood consumption is regular. At seven years of age, 592 children underwent a medical examination, including cardiac function assessment. Blood pressure (BP) was taken using an automated blood pressure monitor, heart rate variability (HRV, 9 parameters) and electrocardiogram (ECG) characteristics (QT, T-wave parameters) were measured using Holter cardiac monitoring during the examination. Total mercury concentrations were measured in cord blood at birth (median = 6.6 μg/L, N = 399) and in the children's blood at age 7 (median = 1.7 μg/L, N = 310). Adjusted linear and non-linear modelling was used to study the association of each cardiac parameter with prenatal and childhood exposures. Sensitivity analyses included co-exposures to lead and cadmium, adjustment for maternal seafood consumption, selenium and polyunsaturated fatty acids (n3-PUFAs), and for sporting activity.

RESULTS

Higher prenatal mercury was associated with higher systolic BP at 7 years of age (βlog2 = 1.02; 95% Confidence Interval (CI) = 0.10, 1.19). In boys, intermediate prenatal exposure was associated with reduced overall HRV and parasympathetic activity, and longer QT was observed with increasing prenatal mercury (βlog2 = 4.02; CI = 0.48, 7.56). In girls, HRV tended to increase linearly with prenatal exposure, and no association was observed with QT-wave related parameters. Mercury exposure at 7 years was associated with decreased BP in girls (βlog2 = -1.13; CI = -2.22, -0.004 for diastolic BP). In boys, the low/high-frequency (LF/HF) ratio increased for intermediate levels of exposure.

CONCLUSION

Our study suggests sex-specific and non-monotonic modifications in some cardiac health parameters following prenatal exposure to mercury in pre-pubertal children from an insular fish-consuming population.

Synchronous recording of magnetocardiographic and electrocardiographic signals

We present a system for simultaneous recording of the electrocardiogram and the magnetocardiogram. The measurement system contained of printed carbon electrodes and SERF magnetometer. The use of this system confirms that the position of the end of the magnetic T wave extends further than the electric T wave, which is an important indicator for the diagnosis of cardiological patients and for drug arrhythmogenicity. We analyze this phenomenon in depth, and demonstrate, that it originates from the fundamental difference between electric and magnetic measurements. The measured value is always bipolar since the electric measurements require two electrodes. We demonstrate how the dual electric and magnetic measuring system adds a new information to the commonly used electrocardiographic diagnosis. The ECG should be interpreted as the spatial asymmetry of the electric cardiac potential, and not as the potential itself. The results seem to prove, that the relation between the magnetic and the electric imaging of neural activities may be broadly applied for the benefit of medical diagnosis in cardiology and many other fields, where the neural activity is measured. This is a pilot study which requires further confirmation at the clinical level.

Time-Warping Analysis of the T-Wave Peak-to-End Interval to Quantify Ventricular Repolarization Dispersion During Ischemia

Variations in the dispersion of ventricular repolarization can be quantified by T-wave time-warping based index, dw. However, the early phase of the T-wave can be affected by ST-segment changes during ischemia. We hypothesized that restricting dw to the T-wave peak-to-end ( Tpe) would circumvent this limitation while still quantifying variations in repolarization dispersion. A total of 101 ECG recordings from patients undergoing coronary occlusion, together with their control recordings, were analyzed. A series of dw values was calculated by quantifying the Tpe morphological variations between the T-waves at different occlusion stages and a baseline T-wave. We introduced a normalized version of dw, Rd, reflecting variations of dw during occlusion relative to control recordings ( Rd = 1 corresponds to the same level of variation). The dw series followed a gradually increasing trend with occlusion time, reaching median [range] Rd values of 9.44 [1.01, 80.74] at the occlusion end. Rd at occlusion end was significantly higher than threshold values of 1, 2, 5, and 10 in 94.1%, 85.11%, 64.4% and 48.5% of patients, respectively. The spatial lead-wise analysis of dw showed distinct distributions depending on the occluded artery, suggesting a relation with the ischemia location. The relative variation R with ischemia of index dw (9.4) is greater than that of the T-wave amplitude (7.7), Tpe interval (2.7) and T-wave width (3.0). In conclusion, dw tracks ischemic-induced variations in repolarization dispersion in a more robust manner than classical indexes, avoiding the impact of ST segment elevation/depression or early T-wave distortions, thus warranting further clinical studies.

Optimizing patient selection for primary prevention implantable cardioverter-defibrillator implantation: utilizing multimodal machine learning to assess risk of implantable cardioverter-defibrillator non-benefit

AIMS

Left ventricular ejection fraction (LVEF) is suboptimal as a sole marker for predicting sudden cardiac death (SCD). Machine learning (ML) provides new opportunities for personalized predictions using complex, multimodal data. This study aimed to determine if risk stratification for implantable cardioverter-defibrillator (ICD) implantation can be improved by ML models that combine clinical variables with 12-lead electrocardiograms (ECG) time-series features.

METHODS AND RESULTS

A multicentre study of 1010 patients (64.9 ± 10.8 years, 26.8% female) with ischaemic, dilated, or non-ischaemic cardiomyopathy, and LVEF ≤ 35% implanted with an ICD between 2007 and 2021 for primary prevention of SCD in two academic hospitals was performed. For each patient, a raw 12-lead, 10-s ECG was obtained within 90 days before ICD implantation, and clinical details were collected. Supervised ML models were trained and validated on a development cohort (n = 550) from Hospital A to predict ICD non-arrhythmic mortality at three-year follow-up (i.e. mortality without prior appropriate ICD-therapy). Model performance was evaluated on an external patient cohort from Hospital B (n = 460). At three-year follow-up, 16.0% of patients had died, with 72.8% meeting criteria for non-arrhythmic mortality. Extreme gradient boosting models identified patients with non-arrhythmic mortality with an area under the receiver operating characteristic curve (AUROC) of 0.90 [95% confidence intervals (CI) 0.80-1.00] during internal validation. In the external cohort, the AUROC was 0.79 (95% CI 0.75-0.84).

CONCLUSIONS

ML models combining ECG time-series features and clinical variables were able to predict non-arrhythmic mortality within three years after device implantation in a primary prevention population, with robust performance in an independent cohort.

Strain Imaging and Ventricular Arrhythmia

Ventricular arrhythmia is one of the main causes of sudden cardiac death. Hence, identifying patients at risk of ventricular arrhythmias and sudden cardiac death is important but can be challenging. The indication for an implantable cardioverter defibrillator as a primary preventive strategy relies on the left ventricular ejection fraction as a measure of systolic function. However, ejection fraction is flawed by technical constraints and is an indirect measure of systolic function. There has, therefore, been an incentive to identify other markers to optimize the risk prediction of malignant arrhythmias to select proper candidates who could benefit from an implantable cardioverter defibrillator. Speckle-tracking echocardiography allows for a detailed assessment of cardiac mechanics, and strain imaging has repeatedly been shown to be a sensitive technique to identify systolic dysfunction unrecognized by ejection fraction. Several strain measures, including global longitudinal strain, regional strain, and mechanical dispersion, have consequently been proposed as potential markers of ventricular arrhythmias. In this review, we will provide an overview of the potential use of different strain measures in the context of ventricular arrhythmias.

T-Wave Analysis on the 24 h Holter ECG Monitoring as a Predictive Assessment of Major Adverse Cardiovascular Events in Patients with Myocardial Infarction: A Literature Review and Future Perspectives

Myocardial ischemia is a pathophysiological state characterized by inadequate perfusion of the myocardium, resulting in an imbalance between myocardial oxygen demand and supply. It is most commonly caused by coronary artery disease, in which atherosclerotic plaques lead to luminal narrowing and reduced blood flow to the heart. Myocardial ischemia can manifest as angina pectoris or silent myocardial ischemia and can progress to myocardial infarction or heart failure if left untreated. Diagnosis of myocardial ischemia typically involves a combination of clinical evaluation, electrocardiography and imaging studies. Electrocardiographic parameters, as assessed by 24 h Holter ECG monitoring, can predict the occurrence of major adverse cardiovascular events in patients with myocardial ischemia, independent of other risk factors. The T-waves in patients with myocardial ischemia have prognostic value for predicting major adverse cardiovascular events, and their electrophysiological heterogeneity can be visualized using various techniques. Combining the electrocardiographic findings with the assessment of myocardial substrate may offer a better picture of the factors that can contribute to cardiovascular death.