1
|
Pascual-Sánchez L, Goya-Esteban R, Cruz-Roldán F, Hernández-Madrid A, Blanco-Velasco M. Machine learning based detection of T-wave alternans in real ambulatory conditions. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2024; 249:108157. [PMID: 38582037 DOI: 10.1016/j.cmpb.2024.108157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2024] [Revised: 03/20/2024] [Accepted: 03/28/2024] [Indexed: 04/08/2024]
Abstract
BACKGROUND AND OBJECTIVE T-wave alternans (TWA) is a fluctuation in the repolarization morphology of the ECG. It is associated with cardiac instability and sudden cardiac death risk. Diverse methods have been proposed for TWA analysis. However, TWA detection in ambulatory settings remains a challenge due to the absence of standardized evaluation metrics and detection thresholds. METHODS In this work we use traditional TWA analysis signal processing-based methods for feature extraction, and two machine learning (ML) methods, namely, K-nearest-neighbor (KNN) and random forest (RF), for TWA detection, addressing hyper-parameter tuning and feature selection. The final goal is the detection in ambulatory recordings of short, non-sustained and sparse TWA events. RESULTS We train ML methods to detect a wide variety of alternant voltage from 20 to 100 μV, i.e., ranging from non-visible micro-alternans to TWA of higher amplitudes, to recognize a wide range in concordance to risk stratification. In classification, RF outperforms significantly the recall in comparison with the signal processing methods, at the expense of a small lost in precision. Despite ambulatory detection stands for an imbalanced category context, the trained ML systems always outperform signal processing methods. CONCLUSIONS We propose a comprehensive integration of multiple variables inspired by TWA signal processing methods to fed learning-based methods. ML models consistently outperform the best signal processing methods, yielding superior recall scores.
Collapse
Affiliation(s)
- Lidia Pascual-Sánchez
- Department of Teoría de la Señal y Comunicaciones, Universidad de Alcalá, Madrid, Spain.
| | - Rebeca Goya-Esteban
- Department of Teoría de la Señal y Comunicaciones, Universidad Rey Juan Carlos, Madrid, Spain.
| | - Fernando Cruz-Roldán
- Department of Teoría de la Señal y Comunicaciones, Universidad de Alcalá, Madrid, Spain.
| | | | - Manuel Blanco-Velasco
- Department of Teoría de la Señal y Comunicaciones, Universidad de Alcalá, Madrid, Spain.
| |
Collapse
|
2
|
Fernández–Calvillo MG, Goya–Esteban R, Cruz–Roldán F, Hernández–Madrid A, Blanco–Velasco M. Machine Learning approach for TWA detection relying on ensemble data design. Heliyon 2023; 9:e12947. [PMID: 36699267 PMCID: PMC9868537 DOI: 10.1016/j.heliyon.2023.e12947] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 12/23/2022] [Accepted: 01/10/2023] [Indexed: 01/17/2023] Open
Abstract
Background and objective T-wave alternans (TWA) is a fluctuation of the ST-T complex of the surface electrocardiogram (ECG) on an every-other-beat basis. It has been shown to be clinically helpful for sudden cardiac death stratification, though the lack of a gold standard to benchmark detection methods limits its application and impairs the development of alternative techniques. In this work, a novel approach based on machine learning for TWA detection is proposed. Additionally, a complete experimental setup is presented for TWA detection methods benchmarking. Methods The proposed experimental setup is based on the use of open-source databases to enable experiment replication and the use of real ECG signals with added TWA episodes. Also, intra-patient overfitting and class imbalance have been carefully avoided. The Spectral Method (SM), the Modified Moving Average Method (MMA), and the Time Domain Method (TM) are used to obtain input features to the Machine Learning (ML) algorithms, namely, K Nearest Neighbor, Decision Trees, Random Forest, Support Vector Machine and Multi-Layer Perceptron. Results There were not found large differences in the performance of the different ML algorithms. Decision Trees showed the best overall performance (accuracy 0.88 ± 0.04 , precision 0.89 ± 0.05 , Recall 0.90 ± 0.05 , F1 score 0.89 ± 0.03 ). Compared to the SM (accuracy 0.79, precision 0.93, Recall 0.64, F1 score 0.76) there was an improvement in every metric except for the precision. Conclusions In this work, a realistic database to test the presence of TWA using ML algorithms was assembled. The ML algorithms overall outperformed the SM used as a gold standard. Learning from data to identify alternans elicits a substantial detection growth at the expense of a small increment of the false alarm.
Collapse
Affiliation(s)
| | - Rebeca Goya–Esteban
- Department of Teoría de la Señal y Comunicaciones, Universidad Rey Juan Carlos, Madrid, Spain
| | - Fernando Cruz–Roldán
- Department of Teoría de la Señal y Comunicaciones, Universidad de Alcalá, Madrid, Spain
| | | | - Manuel Blanco–Velasco
- Department of Teoría de la Señal y Comunicaciones, Universidad de Alcalá, Madrid, Spain,Corresponding author.
| |
Collapse
|
3
|
Liżewska-Springer A, Królak T, Dorniak K, Kempa M, Dąbrowska-Kugacka A, Sławiński G, Lewicka E. Right Ventricular Endocardial Mapping and a Potential Arrhythmogenic Substrate in Cardiac Amyloidosis-Role of ICD. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:ijerph182111631. [PMID: 34770146 PMCID: PMC8583432 DOI: 10.3390/ijerph182111631] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/25/2021] [Revised: 10/28/2021] [Accepted: 11/03/2021] [Indexed: 11/16/2022]
Abstract
Patients with cardiac amyloidosis (CA) have an increased risk of sudden cardiac death. (SCD). However, the role of an implantable cardioverter-defibrillator in the primary prevention of SCD in this group of patients is still controversial. We present a case with CA with recurrent syncope and non-sustained ventricular tachycardia. In order to further stratify the risk of SCD, an electrophysiological study with endocardial electroanatomic voltage mapping was performed prior to the ICD placement.
Collapse
Affiliation(s)
- Aleksandra Liżewska-Springer
- Department of Cardiology and Electrotherapy, Medical University of Gdansk, 80-952 Gdansk, Poland; (T.K.); (M.K.); (A.D.-K.); (G.S.); (E.L.)
- Correspondence:
| | - Tomasz Królak
- Department of Cardiology and Electrotherapy, Medical University of Gdansk, 80-952 Gdansk, Poland; (T.K.); (M.K.); (A.D.-K.); (G.S.); (E.L.)
| | - Karolina Dorniak
- Department of Nonivasive Cardiac Diagnostics, Medical University of Gdansk, 80-952 Gdansk, Poland;
| | - Maciej Kempa
- Department of Cardiology and Electrotherapy, Medical University of Gdansk, 80-952 Gdansk, Poland; (T.K.); (M.K.); (A.D.-K.); (G.S.); (E.L.)
| | - Alicja Dąbrowska-Kugacka
- Department of Cardiology and Electrotherapy, Medical University of Gdansk, 80-952 Gdansk, Poland; (T.K.); (M.K.); (A.D.-K.); (G.S.); (E.L.)
| | - Grzegorz Sławiński
- Department of Cardiology and Electrotherapy, Medical University of Gdansk, 80-952 Gdansk, Poland; (T.K.); (M.K.); (A.D.-K.); (G.S.); (E.L.)
| | - Ewa Lewicka
- Department of Cardiology and Electrotherapy, Medical University of Gdansk, 80-952 Gdansk, Poland; (T.K.); (M.K.); (A.D.-K.); (G.S.); (E.L.)
| |
Collapse
|
4
|
Abstract
The ambulatory ECG (AECG) is an important diagnostic tool for many heart electrophysiology-related cases. AECG covers a wide spectrum of devices and applications. At the core of these devices and applications are the algorithms responsible for signal conditioning, ECG beat detection and classification, and event detections. Over the years, there has been huge progress for algorithm development and implementation thanks to great efforts by researchers, engineers, and physicians, alongside the rapid development of electronics and signal processing, especially machine learning (ML). The current efforts and progress in machine learning fields are unprecedented, and many of these ML algorithms have also been successfully applied to AECG applications. This review covers some key AECG applications of ML algorithms. However, instead of doing a general review of ML algorithms, we are focusing on the central tasks of AECG and discussing what ML can bring to solve the key challenges AECG is facing. The center tasks of AECG signal processing listed in the review include signal preprocessing, beat detection and classification, event detection, and event prediction. Each AECG device/system might have different portions and forms of those signal components depending on its application and the target, but these are the topics most relevant and of greatest concern to the people working in this area.
Collapse
|
5
|
Kulkarni K, Stavrakis S, Elkholey K, Singh JP, Parks KA, Armoundas AA. Microvolt T-Wave Alternans Is Modulated by Acute Low-Level Tragus Stimulation in Patients With Ischemic Cardiomyopathy and Heart Failure. Front Physiol 2021; 12:707724. [PMID: 34366894 PMCID: PMC8343129 DOI: 10.3389/fphys.2021.707724] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 06/30/2021] [Indexed: 12/15/2022] Open
Abstract
Aims: Microvolt T-wave alternans (TWA), an oscillation in T-wave morphology of the electrocardiogram (ECG), has been associated with increased susceptibility to ventricular tachy-arrhythmias, while vagus nerve stimulation has shown promising anti-arrhythmic effects in in vivo and ex vivo animal studies. We aimed to examine the effect of non-invasive, acute low-level tragus stimulation (LLTS) on TWA in patients with ischemic cardiomyopathy and heart failure. Methods: 26 patients with ischemic cardiomyopathy (left ventricular ejection fraction <35%) and chronic stable heart failure, previously implanted with an automatic implantable cardioverter defibrillator (ICD) device with an atrial lead (dual chamber ICD or cardiac resynchronization therapy defibrillator), were enrolled in the study. Each patient sequentially received, (1) Sham LLTS (electrode on tragus, but no stimulation delivered) for 5 min; (2) Active LLTS at two different frequencies (5 and 20 Hz, 15 min each); and (3) Active LLTS, during concomitant atrial pacing at 100 bpm at two different frequencies (5 and 20 Hz, 15 min each). LLTS was delivered through a transcutaneous electrical nerve stimulation device (pulse width 200 μs, frequency 5/20 Hz, amplitude 1 mA lower than the discomfort threshold). TWA burden was assessed using continuous ECG monitoring during sham and active LLTS in sinus rhythm, as well as during atrial pacing. Results: Right atrial pacing at 100 bpm led to significantly heightened TWA burden compared to sinus rhythm, with or without LLTS. Acute LLTS at both 5 and 20 Hz, during sinus rhythm led to a significant rise in TWA burden in the precordial leads (p < 0.05). Conclusion: Acute LLTS results in a heart-rate dependent increase in TWA burden.
Collapse
Affiliation(s)
- Kanchan Kulkarni
- Cardiovascular Research Center, Massachusetts General Hospital, Boston, MA, United States
| | - Stavros Stavrakis
- Heart Rhythm Institute, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Khaled Elkholey
- Heart Rhythm Institute, The University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Jagmeet P Singh
- Cardiology Division, Cardiac Arrhythmia Service, Massachusetts General Hospital, Boston, MA, United States
| | - Kimberly A Parks
- Cardiology Division, Brigham and Women's Hospital, Boston, MA, United States
| | - Antonis A Armoundas
- Cardiovascular Research Center, Massachusetts General Hospital, Boston, MA, United States.,Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, United States
| |
Collapse
|
6
|
Liżewska-Springer A, Sławiński G, Lewicka E. Arrhythmic Sudden Cardiac Death and the Role of Implantable Cardioverter-Defibrillator in Patients with Cardiac Amyloidosis-A Narrative Literature Review. J Clin Med 2021; 10:1858. [PMID: 33922892 PMCID: PMC8123220 DOI: 10.3390/jcm10091858] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 04/07/2021] [Accepted: 04/20/2021] [Indexed: 11/16/2022] Open
Abstract
Cardiac amyloidosis (CA) is considered to be associated with an increased risk of sudden cardiac death (SCD) due to ventricular tachyarrhythmias and electromechanical dissociation. However, current arrhythmic risk stratification and the role of an implantable cardioverter-defibrillator (ICD) for primary prevention of SCD remains unclear. This article provides a narrative review of the literature on electrophysiological abnormalities in the context of ventricular arrhythmias in patients with CA and the role of ICD in terms of survival benefit in this group of patients.
Collapse
Affiliation(s)
- Aleksandra Liżewska-Springer
- Department of Cardiology and Electrotherapy, Medical University of Gdańsk, 80-210 Gdańsk, Poland; (G.S.); (E.L.)
| | | | | |
Collapse
|
7
|
You T, Luo C, Zhang K, Zhang H. Electrophysiological Mechanisms Underlying T-Wave Alternans and Their Role in Arrhythmogenesis. Front Physiol 2021; 12:614946. [PMID: 33746768 PMCID: PMC7969788 DOI: 10.3389/fphys.2021.614946] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Accepted: 02/10/2021] [Indexed: 12/18/2022] Open
Abstract
T-wave alternans (TWA) reflects every-other-beat alterations in the morphology of the electrocardiogram ST segment or T wave in the setting of a constant heart rate, hence, in the absence of heart rate variability. It is believed to be associated with the dispersion of repolarization and has been used as a non-invasive marker for predicting the risk of malignant cardiac arrhythmias and sudden cardiac death as numerous studies have shown. This review aims to provide up-to-date review on both experimental and simulation studies in elucidating possible mechanisms underlying the genesis of TWA at the cellular level, as well as the genesis of spatially concordant/discordant alternans at the tissue level, and their transition to cardiac arrhythmia. Recent progress and future perspectives in antiarrhythmic therapies associated with TWA are also discussed.
Collapse
Affiliation(s)
- Tingting You
- Key Lab of Medical Electrophysiology, Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Cunjin Luo
- School of Computer Science and Electronic Engineering, University of Essex, Colchester, United Kingdom
| | - Kevin Zhang
- School of Medicine, Imperial College of London, London, United Kingdom
| | - Henggui Zhang
- Key Lab of Medical Electrophysiology, Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China.,Department of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
| |
Collapse
|
8
|
Blatter LA, Kanaporis G, Martinez-Hernandez E, Oropeza-Almazan Y, Banach K. Excitation-contraction coupling and calcium release in atrial muscle. Pflugers Arch 2021; 473:317-329. [PMID: 33398498 DOI: 10.1007/s00424-020-02506-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 12/03/2020] [Accepted: 12/16/2020] [Indexed: 01/02/2023]
Abstract
In cardiac muscle, the process of excitation-contraction coupling (ECC) describes the chain of events that links action potential induced myocyte membrane depolarization, surface membrane ion channel activation, triggering of Ca2+ induced Ca2+ release from the sarcoplasmic reticulum (SR) Ca2+ store to activation of the contractile machinery that is ultimately responsible for the pump function of the heart. Here we review similarities and differences of structural and functional attributes of ECC between atrial and ventricular tissue. We explore a novel "fire-diffuse-uptake-fire" paradigm of atrial ECC and Ca2+ release that assigns a novel role to the SR SERCA pump and involves a concerted "tandem" activation of the ryanodine receptor Ca2+ release channel by cytosolic and luminal Ca2+. We discuss the contribution of the inositol 1,4,5-trisphosphate (IP3) receptor Ca2+ release channel as an auxiliary pathway to Ca2+ signaling, and we review IP3 receptor-induced Ca2+ release involvement in beat-to-beat ECC, nuclear Ca2+ signaling, and arrhythmogenesis. Finally, we explore the topic of electromechanical and Ca2+ alternans and its ramifications for atrial arrhythmia.
Collapse
Affiliation(s)
- L A Blatter
- Department of Physiology & Biophysics, Rush University Medical Center, 1750 W. Harrison Street, Chicago, IL, 60612, USA.
| | - G Kanaporis
- Department of Physiology & Biophysics, Rush University Medical Center, 1750 W. Harrison Street, Chicago, IL, 60612, USA
| | - E Martinez-Hernandez
- Department of Physiology & Biophysics, Rush University Medical Center, 1750 W. Harrison Street, Chicago, IL, 60612, USA
| | - Y Oropeza-Almazan
- Department of Physiology & Biophysics, Rush University Medical Center, 1750 W. Harrison Street, Chicago, IL, 60612, USA
| | - K Banach
- Department of Internal Medicine/Cardiology, Rush University Medical Center, Chicago, IL, 60612, USA
| |
Collapse
|
9
|
Merchant FM, Sayadi O, Sohn K, Weiss EH, Puppala D, Doddamani R, Singh JP, Heist EK, Owen C, Kulkarni K, Armoundas AA. Real-Time Closed-Loop Suppression of Repolarization Alternans Reduces Arrhythmia Susceptibility In Vivo. Circ Arrhythm Electrophysiol 2020; 13:e008186. [PMID: 32434448 DOI: 10.1161/circep.119.008186] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Repolarization alternans (RA) has been implicated in the pathogenesis of ventricular arrhythmias and sudden cardiac death. METHODS We have developed a real-time, closed-loop system to record and analyze RA from multiple intracardiac leads, and deliver dynamically R-wave triggered pacing stimuli during the absolute refractory period. We have evaluated the ability of this system to control RA and reduce arrhythmia susceptibility, in vivo. RESULTS R-wave triggered pacing can induce RA, the magnitude of which can be modulated by varying the amplitude, pulse width, and size of the pacing vector. Using a swine model (n=9), we demonstrate that to induce a 1 µV change in the alternans voltage on the body surface, coronary sinus and left ventricle leads, requires a delivered charge of 0.04±0.02, 0.05±0.025, and 0.06±0.033 µC, respectively, while to induce a one unit change of the Kscore, requires a delivered charge of 0.93±0.73, 0.32±0.29, and 0.33±0.37 µC, respectively. For all body surface and intracardiac leads, both Δ(alternans voltage) and ΔKscore between baseline and R-wave triggered paced beats increases consistently with an increase in the pacing pulse amplitude, pulse width, and vector spacing. Additionally, we show that the proposed method can be used to suppress spontaneously occurring alternans (n=7), in the presence of myocardial ischemia. Suppression of RA by pacing during the absolute refractory period results in a significant reduction in arrhythmia susceptibility, evidenced by a lower Srank score during programmed ventricular stimulation compared with baseline before ischemia. CONCLUSIONS We have developed and evaluated a novel closed-loop method to dynamically modulate RA in a swine model. Our data suggest that suppression of RA directly reduces arrhythmia susceptibility and reinforces the concept that RA plays a critical role in the pathophysiology of arrhythmogenesis.
Collapse
Affiliation(s)
- Faisal M Merchant
- Cardiology Division, Emory University School of Medicine, Atlanta, GA (F.M.M.).,Cardiovascular Research Center (F.M.M., O.S., K.S., E.H.W., D.P., R.D., K.K., A.A.A.), Massachusetts General Hospital, Boston
| | - Omid Sayadi
- Cardiovascular Research Center (F.M.M., O.S., K.S., E.H.W., D.P., R.D., K.K., A.A.A.), Massachusetts General Hospital, Boston
| | - Kwanghyun Sohn
- Cardiovascular Research Center (F.M.M., O.S., K.S., E.H.W., D.P., R.D., K.K., A.A.A.), Massachusetts General Hospital, Boston
| | - Eric H Weiss
- Cardiovascular Research Center (F.M.M., O.S., K.S., E.H.W., D.P., R.D., K.K., A.A.A.), Massachusetts General Hospital, Boston.,Institute for Medical Engineering and Science, Massachusetts Institute of Technology Cambridge (E.H.W., A.A.A.)
| | - Dheeraj Puppala
- Cardiovascular Research Center (F.M.M., O.S., K.S., E.H.W., D.P., R.D., K.K., A.A.A.), Massachusetts General Hospital, Boston
| | - Rajiv Doddamani
- Cardiovascular Research Center (F.M.M., O.S., K.S., E.H.W., D.P., R.D., K.K., A.A.A.), Massachusetts General Hospital, Boston
| | - Jagmeet P Singh
- Cardiology Division, Cardiac Arrhythmia Service (J.P.S., E.K.H.), Massachusetts General Hospital, Boston
| | - E Kevin Heist
- Cardiology Division, Cardiac Arrhythmia Service (J.P.S., E.K.H.), Massachusetts General Hospital, Boston
| | - Chris Owen
- Neurosurgery Division (C.O.), Massachusetts General Hospital, Boston
| | - Kanchan Kulkarni
- Cardiovascular Research Center (F.M.M., O.S., K.S., E.H.W., D.P., R.D., K.K., A.A.A.), Massachusetts General Hospital, Boston
| | - Antonis A Armoundas
- Cardiovascular Research Center (F.M.M., O.S., K.S., E.H.W., D.P., R.D., K.K., A.A.A.), Massachusetts General Hospital, Boston.,Institute for Medical Engineering and Science, Massachusetts Institute of Technology Cambridge (E.H.W., A.A.A.)
| |
Collapse
|
10
|
Sohn K, Dalvin SP, Merchant FM, Kulkarni K, Sana F, Abohashem S, Singh JP, Heist EK, Owen C, Isselbacher EM, Armoundas AA. Utility of a Smartphone Based System (cvrPhone) to Predict Short-term Arrhythmia Susceptibility. Sci Rep 2019; 9:14497. [PMID: 31601824 PMCID: PMC6787075 DOI: 10.1038/s41598-019-50487-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2019] [Accepted: 09/10/2019] [Indexed: 01/27/2023] Open
Abstract
Repolarization alternans (RA) has been implicated in the pathogenesis of ventricular arrhythmias and sudden cardiac death. We developed a 12-lead, blue-tooth/Smart-Phone (Android) based electrocardiogram (ECG) acquisition and monitoring system (cvrPhone), and an application to estimate RA, in real-time. In in-vivo swine studies (N = 17), 12-lead ECG signals were recorded at baseline and following coronary artery occlusion. RA was estimated using the Fast Fourier Transform (FFT) method using a custom developed algorithm in JAVA. Underlying ischemia was detected using a custom developed ischemic index. RA from each lead showed a significant (p < 0.05) increase within 1 min of occlusion compared to baseline (n = 29). Following myocardial infarction, spontaneous ventricular tachycardia episodes (n = 4) were preceded by significant (p < 0.05) increase of RA prior to the onset of the tachy-arrhythmias. Similarly, the ischemic index exhibited a significant increase following myocardial infarction (p < 0.05) and preceding a tachy-arrhythmic event. In conclusion, RA can be effectively estimated using surface lead electrocardiograms by analyzing beat-to-beat variability in ECG morphology using a smartphone based platform. cvrPhone can be used to detect myocardial ischemia and arrhythmia susceptibility using a user-friendly, clinically acceptable, mobile platform.
Collapse
Affiliation(s)
- Kwanghyun Sohn
- Cardiovascular Research Center, Massachusetts General Hospital, Boston, MA, USA
| | - Steven P Dalvin
- Cardiovascular Research Center, Massachusetts General Hospital, Boston, MA, USA
| | - Faisal M Merchant
- Cardiology Division, Emory, University School of Medicine, Atlanta, GA, USA
| | - Kanchan Kulkarni
- Cardiovascular Research Center, Massachusetts General Hospital, Boston, MA, USA
| | - Furrukh Sana
- Cardiovascular Research Center, Massachusetts General Hospital, Boston, MA, USA
| | - Shady Abohashem
- Cardiovascular Research Center, Massachusetts General Hospital, Boston, MA, USA
| | - Jagmeet P Singh
- Cardiology Division, Cardiac Arrhythmia Service, Massachusetts General Hospital, Boston, MA, USA
| | - E Kevin Heist
- Cardiology Division, Cardiac Arrhythmia Service, Massachusetts General Hospital, Boston, MA, USA
| | - Chris Owen
- Neurosurgery Division, Massachusetts General Hospital, Boston, MA, USA
| | - Eric M Isselbacher
- Healthcare Transformation Lab, Massachusetts General Hospital, Boston, MA, USA
| | - Antonis A Armoundas
- Cardiovascular Research Center, Massachusetts General Hospital, Boston, MA, USA. .,Institute for Medical Engineering and Science, Massachusetts Institute of Technology Cambridge, MA, USA.
| |
Collapse
|
11
|
Kanaporis G, Kalik ZM, Blatter LA. Action potential shortening rescues atrial calcium alternans. J Physiol 2018; 597:723-740. [PMID: 30412286 DOI: 10.1113/jp277188] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Accepted: 11/08/2018] [Indexed: 01/08/2023] Open
Abstract
KEY POINTS Cardiac alternans refers to a beat-to-beat alternation in contraction, action potential (AP) morphology and Ca2+ transient (CaT) amplitude, and represents a risk factor for cardiac arrhythmia, including atrial fibrillation. We developed strategies to pharmacologically manipulate the AP waveform with the goal to reduce or eliminate the occurrence of CaT and contraction alternans in atrial tissue. With combined patch-clamp and intracellular Ca2+ measurements we investigated the effect of specific ion channel inhibitors and activators on alternans. In single rabbit atrial myocytes, suppression of Ca2+ -activated Cl- channels eliminated AP duration alternans, but prolonged the AP and failed to eliminate CaT alternans. In contrast, activation of K+ currents (IKs and IKr ) shortened the AP and eliminated both AP duration and CaT alternans. As demonstrated also at the whole heart level, activation of K+ conductances represents a promising strategy to suppress alternans, and thus reducing a risk factor for atrial fibrillation. ABSTRACT At the cellular level alternans is observed as beat-to-beat alternations in contraction, action potential (AP) morphology and magnitude of the Ca2+ transient (CaT). Alternans is a well-established risk factor for cardiac arrhythmia, including atrial fibrillation. This study investigates whether pharmacological manipulation of AP morphology is a viable strategy to reduce the risk of arrhythmogenic CaT alternans. Pacing-induced AP and CaT alternans were studied in rabbit atrial myocytes using combined Ca2+ imaging and electrophysiological measurements. Increased AP duration (APD) and beat-to-beat alternations in AP morphology lowered the pacing frequency threshold and increased the degree of CaT alternans. Inhibition of Ca2+ -activated Cl- channels reduced beat-to-beat AP alternations, but prolonged APD and failed to suppress CaT alternans. In contrast, AP shortening induced by activators of two K+ channels (ML277 for Kv7.1 and NS1643 for Kv11.1) abolished both APD and CaT alternans in field-stimulated and current-clamped myocytes. K+ channel activators had no effect on the degree of Ca2+ alternans in AP voltage-clamped cells, confirming that suppression of Ca2+ alternans was caused by the changes in AP morphology. Finally, activation of Kv11.1 channel significantly attenuated or even abolished atrial T-wave alternans in isolated Langendorff perfused hearts. In summary, AP shortening suppressed or completely eliminated both CaT and APD alternans in single atrial myocytes and atrial T-wave alternans at the whole heart level. Therefore, we suggest that AP shortening is a potential intervention to avert development of alternans with important ramifications for arrhythmia prevention and therapy.
Collapse
Affiliation(s)
- Giedrius Kanaporis
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, IL, 60612, USA
| | - Zane M Kalik
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, IL, 60612, USA
| | - Lothar A Blatter
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, IL, 60612, USA
| |
Collapse
|
12
|
Coll-Font J, Erem B, Brooks DH. A Potential-Based Inverse Spectral Method to Noninvasively Localize Discordant Distributions of Alternans on the Heart From the ECG. IEEE Trans Biomed Eng 2017; 65:1554-1563. [PMID: 28749343 DOI: 10.1109/tbme.2017.2732159] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
T-wave alternans (TWA), defined as the beat-to-beat alternation in amplitude of the T-waves, has been shown to be linked to ventricular fibrillation (VF). However, current TWA tests have high sensitivity but low specificity in determining who is at risk. To overcome this limitation, it might be helpful to determine the spatial distribution of any regions on the heart that alternate in opposite phase. Understanding these spatial distributions in relation to the regular activation of the heart could help explain the mechanism for the genesis of VF and thus disambiguate the low specificity of TWA. GOAL Image the spatial distribution of TWA on the heart surface from ECG measurements. METHODS We introduced the inverse spectral method (ISM), a tailored inverse (or ElectroCardioGraphic Imaging) solution designed specifically to noninvasively image cases of TWA on the heart. RESULTS We evaluate the ISM on its capacity to reliably detect the spatial distributions of TWA compared against a standard TWA detection method applied directly to the electrograms on the heart surface. We report on results from both a series of synthetic simulations of TWA generated using the ECGSIM software and a set of continuous epicardial surface voltage recordings from a canine experiment. ISM detected TWA distributions that matched the phase of the true underlying out-of-phase regions over and of the heart surface, respectively. CONCLUSION Our results suggest that ISM is capable of reliably detecting the different regions present in a TWA distribution across a wide variety of TWA locations on the heart in simulation and in the face of transients and nonidealities in the canine recordings.
Collapse
|
13
|
Blanco-Velasco M, Goya-Esteban R, Cruz-Roldán F, García-Alberola A, Rojo-Álvarez JL. Benchmarking of a T-wave alternans detection method based on empirical mode decomposition. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2017; 145:147-155. [PMID: 28552120 DOI: 10.1016/j.cmpb.2017.04.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 03/22/2017] [Accepted: 04/11/2017] [Indexed: 06/07/2023]
Abstract
BACKGROUND AND OBJECTIVE T-wave alternans (TWA) is a fluctuation of the ST-T complex occurring on an every-other-beat basis of the surface electrocardiogram (ECG). It has been shown to be an informative risk stratifier for sudden cardiac death, though the lack of gold standard to benchmark detection methods has promoted the use of synthetic signals. This work proposes a novel signal model to study the performance of a TWA detection. Additionally, the methodological validation of a denoising technique based on empirical mode decomposition (EMD), which is used here along with the spectral method, is also tackled. METHODS The proposed test bed system is based on the following guidelines: (1) use of open source databases to enable experimental replication; (2) use of real ECG signals and physiological noise; (3) inclusion of randomized TWA episodes. Both sensitivity (Se) and specificity (Sp) are separately analyzed. Also a nonparametric hypothesis test, based on Bootstrap resampling, is used to determine whether the presence of the EMD block actually improves the performance. RESULTS The results show an outstanding specificity when the EMD block is used, even in very noisy conditions (0.96 compared to 0.72 for SNR = 8 dB), being always superior than that of the conventional SM alone. Regarding the sensitivity, using the EMD method also outperforms in noisy conditions (0.57 compared to 0.46 for SNR=8 dB), while it decreases in noiseless conditions. CONCLUSIONS The proposed test setting designed to analyze the performance guarantees that the actual physiological variability of the cardiac system is reproduced. The use of the EMD-based block in noisy environment enables the identification of most patients with fatal arrhythmias.
Collapse
Affiliation(s)
- Manuel Blanco-Velasco
- Department of Teoría de la Señal y Comunicaciones, Universidad de Alcalá, Alcalá de Henares 28805, Madrid, Spain.
| | - Rebeca Goya-Esteban
- Department of Teoría de la Señal y Comunicaciones, Universidad Rey Juan Carlos, Fuenlabrada 28943, Madrid, Spain.
| | - Fernando Cruz-Roldán
- Department of Teoría de la Señal y Comunicaciones, Universidad de Alcalá, Alcalá de Henares 28805, Madrid, Spain.
| | - Arcadi García-Alberola
- Arrhythmia Unit, Hospital Universitario Virgen de la Arrixaca, El Palmar, Murcia, Spain.
| | - José Luis Rojo-Álvarez
- Department of Teoría de la Señal y Comunicaciones, Universidad Rey Juan Carlos, Fuenlabrada 28943, Madrid, Spain.
| |
Collapse
|
14
|
Kanaporis G, Blatter LA. Alternans in atria: Mechanisms and clinical relevance. MEDICINA-LITHUANIA 2017; 53:139-149. [PMID: 28666575 DOI: 10.1016/j.medici.2017.04.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Accepted: 04/25/2017] [Indexed: 12/29/2022]
Abstract
Atrial fibrillation is the most common sustained arrhythmia and its prevalence is rapidly rising with the aging of the population. Cardiac alternans, defined as cyclic beat-to-beat alternations in contraction force, action potential (AP) duration and intracellular Ca2+ release at constant stimulation rate, has been associated with the development of ventricular arrhythmias. Recent clinical data also provide strong evidence that alternans plays a central role in arrhythmogenesis in atria. The aim of this article is to review the mechanisms that are responsible for repolarization alternans and contribute to the transition from spatially concordant alternans to the more arrhythmogenic spatially discordant alternans in atria.
Collapse
Affiliation(s)
- Giedrius Kanaporis
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, USA.
| | - Lothar A Blatter
- Department of Physiology & Biophysics, Rush University Medical Center, Chicago, USA
| |
Collapse
|
15
|
Lohrmann GM, Peters F, Srivathsan K, Essop MR, Mookadam F. Electrocardiographic Abnormalities in Disease-Free Black South Africans and Correlations With Echocardiographic Indexes and Early Repolarization. Am J Cardiol 2016; 118:765-70. [PMID: 27381667 DOI: 10.1016/j.amjcard.2016.06.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2016] [Revised: 06/03/2016] [Accepted: 06/03/2016] [Indexed: 02/08/2023]
Abstract
Electrocardiographic abnormalities, and specifically early repolarization (ER) patterns, are increasingly found to be common variants in healthy populations free of heart disease or risk factors. Data are sparse in subjects of African descent, for which no increase in adverse cardiovascular outcomes have been demonstrated. A database of healthy disease-free adult volunteers of sub-Saharan African descent had 12 lead electrocardiograms (ECGs) and transthoracic echocardiograms performed. Statistical tests were then performed on the data to elicit associations; 396 volunteers (63.1% women) with a mean age of 37.4 years met the inclusion and exclusion criteria. An abnormal ECG was identified in 50.5% of volunteers, largely because of underlying ST elevation at the J point (ER), left ventricular hypertrophy (LVH) by voltage criteria, and T-wave inversion. Men were more likely to have abnormal ECGs (odds ratio [OR] 1.75; p <0.001), axes (OR 2.05; p = 0.023), display LVH by Sokolow-Lyon voltage criteria (OR 5.45; p <0.001), and have ER patterns (OR 11.61; p <0.001). Additionally, younger adults were also more likely to display LVH by voltage criteria and ER patterns. Volunteers with LVH by ECG had 5.7% higher LV mass indexes (p = 0.047). An abnormal ECG was not associated with a reduced left ventricular ejection fraction or diastolic dysfunction. ECG abnormalities, especially ER patterns, in black adults of Sub-Saharan descent are common, occurring in half of the normal adults.
Collapse
|
16
|
Yaman M, Arslan U, Gümrükçüoğlu HA, Şahin M, Şimşek H, Akdağ S. Effects of Trimetazidine on T Wave Alternans in Stable Coronary Artery Disease. Korean Circ J 2016; 46:343-9. [PMID: 27275171 PMCID: PMC4891599 DOI: 10.4070/kcj.2016.46.3.343] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 07/31/2015] [Accepted: 08/27/2015] [Indexed: 11/24/2022] Open
Abstract
Background and Objectives Studies reveal that the microvolt T wave alternans (MTWA) test has a high negative predictive value for arrhythmic mortality among patients with ischemic or non-ischemic cardiomyopathy. In this study, we investigate the effects of trimetazidine treatment on MTWA and several echocardiographic parameters in patients with stable coronary artery disease. Subjects and Methods One hundred patients (23 females, mean age 55.6±9.2 years) with stable ischemic heart disease were included in the study group. Twenty-five age- and sex-matched patients with stable coronary artery disease formed the control group. All patients were stable with medical treatment, and had no active complaints. Trimetazidine, 60 mg/day, was added to their current treatment for a minimum three months in the study group and the control group received no additional treatment. Pre- and post-treatment MTWA values were measured by 24 hour Holter testing. Left ventricular systolic and diastolic functions were assessed by echocardiography. Results After trimetazidine treatment, several echocardiographic parameters related with diastolic dysfunction significantly improved. MTWA has been found to be significantly improved after trimethazidine treatment (63±8 μV vs. 53±7 μV, p<0.001). Abnormal MTWA was present in 29 and 11 patients pre- and post-treatment, respectively (p< 0.001). Conclusion Trimetazidine improves MTWA, a non-invasive determinant of electrical instability. Moreover, several echocardiographic parameters related with left ventricular functions also improved. Thus, we can conclude that trimetazidine may be an effective agent to prevent arrhythmic complications and improve myocardial functions in patients with stable coronary artery disease.
Collapse
Affiliation(s)
- Mehmet Yaman
- Department of Cardiology, Samsun Education and Research Hospital, Samsun, Turkey
| | - Uğur Arslan
- Department of Cardiology, Samsun Education and Research Hospital, Samsun, Turkey
| | | | - Musa Şahin
- Department of Cardiology,Van 100. Yıl University, Van, Turkey
| | - Hakkı Şimşek
- Department of Cardiology,Van 100. Yıl University, Van, Turkey
| | - Serkan Akdağ
- Department of Cardiology,Van 100. Yıl University, Van, Turkey
| |
Collapse
|
17
|
Nattel S, Andrade J, Macle L, Rivard L, Dyrda K, Mondesert B, Khairy P. New directions in cardiac arrhythmia management: present challenges and future solutions. Can J Cardiol 2014; 30:S420-30. [PMID: 25432137 DOI: 10.1016/j.cjca.2014.09.027] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Revised: 09/25/2014] [Accepted: 09/26/2014] [Indexed: 12/19/2022] Open
Abstract
Cardiac arrhythmias are a major contributor to population morbidity and mortality. Enormous advances in arrhythmia management have occurred over the 60 years since the founding of the Montreal Heart Institute, but important challenges remain. The purpose of this article is to identify the areas of cardiac arrhythmia therapy that need improvement and to discuss the evolving approaches that promise solutions. Challenges in diagnosis, detection, and risk-stratification include difficulties in separating benign from high-risk syncope and pinpointing the underlying causes, the detection of silent atrial fibrillation in patients at risk of stroke, and inadequate identification of sudden-death risk. Implantable devices are limited by the need for battery and device replacements, device complications like infection and dysfunction, and lead complications like fracture, infection, or displacement. Antiarrhythmic drug therapy, although widely used, is plagued by a very limited range of available agents, supply issues, insufficient efficacy, and significant adverse effect risk. Health economic concerns include the high cost of new technologies, challenges in establishing cost effectiveness, and restrictive practices of government or third-party payers. Major improvements in arrhythmia management can be expected from new discoveries and technological developments in genetics, innovative diagnostic tools for arrhythmia monitoring, imaging and analysis, new approaches to antiarrhythmic drug development, biological therapies, and continuing improvement in implantable device technology like further miniaturization, leadless technology, and use of novel energy sources. As exciting as the developments in arrhythmia management have been in the past, we can look forward to exponential improvement in our ability to manage arrhythmia patients in the near future.
Collapse
Affiliation(s)
- Stanley Nattel
- Research Center and Department of Medicine, Montreal Heart Institute and Université de Montréal, Montreal, Quebec, Canada.
| | - Jason Andrade
- Research Center and Department of Medicine, Montreal Heart Institute and Université de Montréal, Montreal, Quebec, Canada
| | - Laurent Macle
- Research Center and Department of Medicine, Montreal Heart Institute and Université de Montréal, Montreal, Quebec, Canada
| | - Lena Rivard
- Research Center and Department of Medicine, Montreal Heart Institute and Université de Montréal, Montreal, Quebec, Canada
| | - Katia Dyrda
- Research Center and Department of Medicine, Montreal Heart Institute and Université de Montréal, Montreal, Quebec, Canada
| | - Blandine Mondesert
- Research Center and Department of Medicine, Montreal Heart Institute and Université de Montréal, Montreal, Quebec, Canada
| | - Paul Khairy
- Research Center and Department of Medicine, Montreal Heart Institute and Université de Montréal, Montreal, Quebec, Canada
| |
Collapse
|
18
|
Goya-Esteban R, Barquero-Pérez O, Blanco-Velasco M, Caamaño-Fernández AJ, García-Alberola A, Rojo-Álvarez JL. Nonparametric signal processing validation in T-wave alternans detection and estimation. IEEE Trans Biomed Eng 2014; 61:1328-38. [PMID: 24658256 DOI: 10.1109/tbme.2014.2304565] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Although a number of methods have been proposed for T-Wave Alternans (TWA) detection and estimation, their performance strongly depends on their signal processing stages and on their free parameters tuning. The dependence of the system quality with respect to the main signal processing stages in TWA algorithms has not yet been studied. This study seeks to optimize the final performance of the system by successive comparisons of pairs of TWA analysis systems, with one single processing difference between them. For this purpose, a set of decision statistics are proposed to evaluate the performance, and a nonparametric hypothesis test (from Bootstrap resampling) is used to make systematic decisions. Both the temporal method (TM) and the spectral method (SM) are analyzed in this study. The experiments were carried out in two datasets: first, in semisynthetic signals with artificial alternant waves and added noise; second, in two public Holter databases with different documented risk of sudden cardiac death. For semisynthetic signals (SNR = 15 dB), after the optimization procedure, a reduction of 34.0% (TM) and 5.2% (SM) of the power of TWA amplitude estimation errors was achieved, and the power of error probability was reduced by 74.7% (SM). For Holter databases, appropriate tuning of several processing blocks, led to a larger intergroup separation between the two populations for TWA amplitude estimation. Our proposal can be used as a systematic procedure for signal processing block optimization in TWA algorithmic implementations.
Collapse
|
19
|
Merchant FM, Sayadi O, Puppala D, Moazzami K, Heller V, Armoundas AA. A translational approach to probe the proarrhythmic potential of cardiac alternans: a reversible overture to arrhythmogenesis? Am J Physiol Heart Circ Physiol 2013; 306:H465-74. [PMID: 24322612 DOI: 10.1152/ajpheart.00639.2013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Electrocardiographic alternans, a phenomenon of beat-to-beat alternation in cardiac electrical waveforms, has been implicated in the pathogenesis of ventricular arrhythmias and sudden cardiac death (SCD). In the clinical setting, a positive microvolt T-wave alternans test has been associated with a heightened risk of arrhythmic mortality and SCD during medium- and long-term follow-up. However, rather than merely being associated with an increased risk for SCD, several lines of preclinical and clinical evidence suggest that cardiac alternans may play a causative role in generating the acute electrophysiological substrate necessary for the onset of ventricular arrhythmias. Deficiencies in Ca(2+) transport processes have been implicated in the genesis of alternans at the subcellular and cellular level and are hypothesized to contribute to the conditions necessary for dispersion of refractoriness, wave break, reentry, and onset of arrhythmia. As such, detecting acute surges in alternans may provide a mechanism for predicting the impending onset of arrhythmia and opens the door to delivering upstream antiarrhythmic therapies. In this review, we discuss the preclinical and clinical evidence to support a causative association between alternans and acute arrhythmogenesis and outline the potential clinical implications of such an association.
Collapse
Affiliation(s)
- Faisal M Merchant
- Cardiology Division, Emory University School of Medicine, Atlanta, Georgia; and
| | | | | | | | | | | |
Collapse
|
20
|
Sayadi O, Merchant FM, Puppala D, Mela T, Singh JP, Heist EK, Owen C, Armoundas AA. A novel method for determining the phase of T-wave alternans: diagnostic and therapeutic implications. Circ Arrhythm Electrophysiol 2013; 6:818-26. [PMID: 23884196 DOI: 10.1161/circep.113.000114] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND T-wave alternans (TWA) has been implicated in the pathogenesis of ventricular arrhythmias and sudden cardiac death. However, to estimate and suppress TWA effectively, the phase of TWA must be accurately determined. METHODS AND RESULTS We developed a method that computes the beat-by-beat integral of the T-wave morphology, over time points within the T-wave with positive alternans. Then, we estimated the signed derivative of the T-wave integral sequence, which allows the classification of each beat to a binary phase index. In animal studies, we found that this method was able to accurately identify the T-wave phase in artificially induced alternans (P<0.0001). The coherence of the phase increased consistently after acute ischemia induction in all body-surface and intracardiac leads (P<0.0001). Also, we developed a phase-resetting detection algorithm that enhances the diagnostic utility of TWA. We further established an algorithm that uses the phase of TWA to deliver appropriate polarity-pacing pulses (all interventions compared with baseline, P<0.0001 for alternans voltage; P<0.0001 for K(score)), to suppress TWA. Finally, we demonstrated that using the phase of TWA we can suppress spontaneous TWA during acute ischemia; 77.6% for alternans voltage (P<0.0001) and 92.5% for K(score) (P<0.0001). CONCLUSIONS We developed a method to quantify the temporal variability of the TWA phase. This method is expected to enhance the utility of TWA in predicting ventricular arrhythmias and sudden cardiac death and raises the possibility of using upstream therapies to abort a ventricular tachyarrhythmia before its onset.
Collapse
|