Sequential Electro-Anatomical Mapping Methodology and Preliminary Results for Reentry Vulnerability Index Estimation

Ventricular tachycardia (VT) recurrence after catheter ablation remains frequent and improved ablation strategies are needed. The re-entry vulnerability index (RVI) is an activation-repolarization marker to localize critical sites for VT initiation. Its use is limited since current electro-anatomical mapping systems (EAMS) cannot provide global measurement of activation and repolarization times within a single beat. We carried out a simulation study to assess a simple method to measure RVI using data collected by sequential EAMS and we investigated the effect of background noise, RT variability (σRT ) and ectopics on RVI estimation. The mean correlation coefficient between single ECG beats and a representative template is used as inclusion/exclusion criterion. Localization of the vulnerable region associated with 5% bottom RVI was accurate (sensitivity80±8%, specificity> 99±1%) for moderate to large repolarization variability (5 ≤ σRT ≤ 20 ms) and moderate level of noise (SNR ≥ 10 dB) but it deteriorated for σRT ≥ 25 ms and SNR ≤ 5 dB. Sensitivity remained high even when RVI estimates were only moderately accurate (cc > 0.67 ± 0.05, MAE < 25 ± 1 ms). The number of ectopic beats did not affect the results. In the in-vivo case analyzed, the sites of low RVI and VT exit was close (5.1 mm

A Method to Minimise the Impact of ECG Marker Inaccuracies on the Spatial QRS-T angle: Evaluation on 1,512 Manually Annotated ECGs

© 2020 The Author(s) The spatial QRS-T angle (QRS-Ta) derived from the vectorcardiogram (VCG) is a strong risk predictor for ventricular arrhythmia and sudden cardiac death with potential use for mass screening. Accurate QRS-Ta estimation in the presence of ECG delineation errors is crucial for its deployment as a prognostic test. Our study assessed the effect of inaccurate QRS and T-wave marker placement on QRS-Ta estimation and proposes a robust method for its calculation. Reference QRS-Ta measurements were derived from 1,512 VCGs manually annotated by three expert reviewers. We systematically changed onset and offset timings of QRS and T-wave markers to simulate inaccurate placement. The QRS-Ta was recalculated using a standard approach and our proposed algorithm, which limits the impact of VCG marker inaccuracies by defining the vector origin as an interval preceding QRS-onset and redefines the beginning and end of QRS and T-wave loops. Using the standard approach, mean absolute errors (MAE) in peak QRS-Ta were >40% and sensitivity and precision in the detection of abnormality (>105°) were 15 ms. Using our proposed algorithm, MAE for peak QRS-Ta were reduced to 94% for inaccuracies up to ±15 ms. Similar results were obtained for mean QRS-Ta. In conclusion, inaccuracies of QRS and T-wave markers can significantly influence the QRS-Ta. Our proposed algorithm provides robust QRS-Ta measurements in the presence of inaccurate VCG annotation, enabling its use in large datasets

The Effect of Emotional Valence on Ventricular Repolarization Dynamics Is Mediated by Heart Rate Variability: A Study of QT Variability and Music-Induced Emotions

Background: Emotions can affect cardiac activity, but their impact on ventricular repolarization variability, an important parameter providing information about cardiac risk and autonomic nervous system activity, is unknown. The beat-to-beat variability of the QT interval (QTV) from the body surface ECG is a non-invasive marker of repolarization variability, which can be decomposed into QTV related to RR variability (QTVrRRV) and QTV unrelated to RRV (QTVuRRV), with the latter thought to be a marker of intrinsic repolarization variability. Aim: To determine the effect of emotional valence (pleasant and unpleasant) on repolarization variability in healthy volunteers by means of QTV analysis. Methods: 75 individuals (24.5 ± 3.2 years, 36 females) without a history of cardiovascular disease listened to music-excerpts that were either felt as pleasant (n = 6) or unpleasant (n = 6). Excerpts lasted about 90 s and were presented in a random order along with silent intervals (n = 6). QTV and RRV were derived from the ECG and the time-frequency spectrum of RRV, QTV, QTVuRRV and QTVrRRV as well as time-frequency coherence between QTV and RRV were estimated. Analysis was performed in low-frequency (LF), high frequency (HF) and total spectral bands. Results: The heart rate-corrected QTV showed a small but significant increase from silence (median 347/interquartile range 31 ms) to listening to music felt as unpleasant (351/30 ms) and pleasant (355/32 ms). The dynamic response of QTV to emotional valence showed a transient phase lasting about 20 s after the onset of each musical excerpt. QTV and RRV were highly correlated in both HF and LF (mean coherence ranging 0.76–0.85). QTV and QTVrRRV decreased during listening to music felt as pleasant and unpleasant with respect to silence and further decreased during listening to music felt as pleasant. QTVuRRV was small and not affected by emotional valence. Conclusion: Emotional valence, as evoked by music, has a small but significant effect on QTV and QTVrRRV, but not on QTVuRRV. This suggests that the interaction between emotional valence and ventricular repolarization variability is mediated by cycle length dynamics and not due to intrinsic repolarization variability

A comparative study of ECG-derived respiration in ambulatory monitoring using the single-lead ECG

Cardiorespiratory monitoring is crucial for the diagnosis and management of multiple conditions such as stress and sleep disorders. Therefore, the development of ambulatory systems providing continuous, comfortable, and inexpensive means for monitoring represents an important research topic. Several techniques have been proposed in the literature to derive respiratory information from the ECG signal. Ten methods to compute single-lead ECG-derived respiration (EDR) were compared under multiple conditions, including different recording systems, baseline wander, normal and abnormal breathing patterns, changes in breathing rate, noise, and artifacts. Respiratory rates, wave morphology, and cardiorespiratory information were derived from the ECG and compared to those extracted from a reference respiratory signal. Three datasets were considered for analysis, involving a total 59 482 one-min, single-lead ECG segments recorded from 156 subjects. The results indicate that the methods based on QRS slopes outperform the other methods. This result is particularly interesting since simplicity is crucial for the development of ECG-based ambulatory systems

Common Genetic Variants Modulate the Electrocardiographic Tpeak-to-Tend Interval.

Sudden cardiac death is responsible for half of all deaths from cardiovascular disease. The analysis of the electrophysiological substrate for arrhythmias is crucial for optimal risk stratification. A prolonged T-peak-to-Tend (Tpe) interval on the electrocardiogram is an independent predictor of increased arrhythmic risk, and Tpe changes with heart rate are even stronger predictors. However, our understanding of the electrophysiological mechanisms supporting these risk factors is limited. We conducted genome-wide association studies (GWASs) for resting Tpe and Tpe response to exercise and recovery in ∼30,000 individuals, followed by replication in independent samples (∼42,000 for resting Tpe and ∼22,000 for Tpe response to exercise and recovery), all from UK Biobank. Fifteen and one single-nucleotide variants for resting Tpe and Tpe response to exercise, respectively, were formally replicated. In a full dataset GWAS, 13 further loci for resting Tpe, 1 for Tpe response to exercise and 1 for Tpe response to exercise were genome-wide significant (p ≤ 5 × 10-8). Sex-specific analyses indicated seven additional loci. In total, we identify 32 loci for resting Tpe, 3 for Tpe response to exercise and 3 for Tpe response to recovery modulating ventricular repolarization, as well as cardiac conduction and contraction. Our findings shed light on the genetic basis of resting Tpe and Tpe response to exercise and recovery, unveiling plausible candidate genes and biological mechanisms underlying ventricular excitability

Estudio de la variabilidad del intervalo QT no relacionada con la variabilidad del ritmo cardiaco durante prueba de esfuerzo para la identificación de enfermedades en las arterias coronarias

Las enfermedades cardiovasculares representan la principal causa de muerte en países industrializados, siendo la cardiopatía isquémica la causa más frecuente de entre todas ellas. Una detección precoz de estas enfermedades proporciona beneficios al disminuir la morbilidad y mortalidad a las que estas se vinculan, pues el tratamiento temprano se asocia a una mejor respuesta terapéutica y curso de la enfermedad. Un procedimiento común por el que se identifican algunas de estas enfermedades, en particular la cardiopatía isquémica, es el estudio de la actividad eléctrica del corazón a través de electrocardiogramas (ECGs) registrados durante prueba de esfuerzo. Los ECGs facilitan el conocimiento de la existencia y gravedad de una enfermedad cardiaca. Estudios recientes señalan una relación entre las variaciones de la fase cardiaca de repolarización ventricular y la existencia de una cardiopatía isquémica. Siguiendo estas líneas de investigación, el objetivo de este trabajo fin de grado es evaluar la capacidad de un índice de variabilidad de la repolarización ventricular durante prueba de esfuerzo extraído del ECG.Específicamente, el nuevo índice cuantifica la repolarización ventricular a través de la variabilidad del intervalo QT no relacionado con el intervalo RR.Las señales ECG analizadas pertenecen a la base de datos FINCAVAS (Finlandia), que contiene los registros durante prueba de esfuerzo de pacientes de los cuales se conoce si sufren o no enfermedades de las arterias coronarias. Se parte de la hipótesis de que el análisis de la repolarización ventricular a través de la variabilidad de QT no relacionada con el RR puede permitir una mejor identificación de los pacientes con cardiopatía isquémica que los índices derivados del ECG utilizados en la actualidad. Esta variabilidad reflejaría la modulación directa de la repolarización ventricular por parte del sistema nervioso autónomo, excluyendo los efectos indirectos que generan las variaciones en el RR.Uno de los retos de este trabajo es conseguir una delineación robusta de los inicios y finales de las ondas del electrocardiograma, en particular, de las ondas Q y T, ya que los ECGs registrados durante prueba de esfuerzo se ven altamente contaminados por ruido muscular y artefactos de movimiento. Posteriormente, se obtiene la variabilidad de estos intervalos y la descomposición de la variabilidad de QT relacionada y no relacionada con el ritmo cardiaco utilizando un análisis tiempo-frecuencia.Los resultados muestran una relación entre la variabilidad del intervalo QT no relacionada con RR y la presencia de cardiopatía isquémica, mostrando una tendencia a una mayor variabilidad de QT no relacionada con RR en sujetos sin CAD.<br /