Recovery Time Dispersion Research Articles

Electrocardiographic evaluation of depolarization and repolarization abnormalities in breast cancer patients with HER2-inhibitor related cardiac dysfunction

Abstract Background The arrhythmic substrates of the myocardium such as depolarization and repolarization abnormalities are thought to reflect cardiac dysfunction prior to the morphologic left ventricular dysfunction. Activation time (AT), recovery time (RT) and T wave peek-end interval dispersion (Tpe-dispersion) are useful indicators of the arrhythmic substrate. We examined the appearance of depolarization and repolarization abnormalities in patients with cancer therapeutics-related cardiac dysfunction (CTRCD) using AT, RT and Tpe-dispersion. Methods We conducted a standardized case-control study of CTRCD with 40 patients who developed breast cancer and treated with trastuzumab (13 cases and 27 controls). We assessed the relation between electrocardiographic indexes, including AT, RT and corrected Tpe-dispersion, and CTRCD. QT intervals were measured by Fridericia method, and QT observer 3 software were used for the measurement of all electrocardiographic indexes. Results LVEF in case and control group were 45.7±8% and 69.2±6%, respectively. AT in aVR lead was significantly higher in case group compared with control (28.8±7ms vs 22.8±5ms, P=0.02). corrected Tpe-dispersion tended to be higher in case group than that of control group (43.2±19ms vs 31.9±10ms, P=0.06). QT dispersion and RT dispersion were not different between case and control group. Conclusions Our study demonstrated that AT in aVR may predict cardiac dysfunction in breast cancer patients with HER2-inhibitor related cardiac dysfunction. More detailed studies using other modalities which can detect depolarization and repolarization abnormalities, including ventricular late potentials and T wave alternans, are needed. Funding Acknowledgement Type of funding source: None

Non-invasive electrocardiographic imaging in patients with idiopathic premature ventricular contractions from the right ventricular outflow tract: New insights into arrhythmia substrate

AimsThe aim of this study was to use non-invasive electrocardiographic imaging (ECGI) to study the electrophysiological properties of right ventricular outflow tract (RVOT) in patients with frequent premature ventricular contractions (PVCs) from the RVOT and in controls. MethodsECGI is a combined application of body surface electrocardiograms and computed tomography or magnetic resonance imaging data. Unipolar electrograms are reconstructed on the epicardial and endocardial surfaces. Activation time (AT) was defined as the time of maximal negative slope of the electrogram (EGM) during QRS, recovery time (RT) as the time of maximal positive slope of the EGM during T wave, Activation recovery interval (ARI) was defined as the difference between RT and AT. ARI dispersion (Δ ARI) and RT dispersion (Δ RT) were calculated as the difference between maximal and minimal ARI and RT respectively. We evaluated those parameters in patients with frequent PVCs from the RVOT, defined as >10.000 per 24 h, and in a control group. ResultsWe studied 7 patients with frequent RVOT PVCs and 17 controls. Patients with PVCs from the RVOT had shorter median RT than controls, in the endocardium and in the epicardium, respectively 380 (239–397) vs 414 (372–448) ms, p = 0.047 and 275 (236–301) vs 330 (263–418) ms, p = 0.047. The dispersion of ARI and of RT in the epicardium was higher than in controls, Δ ARI of 145 (68–216) vs 17 (3–48) ms, p = 0.001 and Δ RT of 201 (160–235) vs 115 (65–177), p = 0.019. ConclusionIn this group of patients we found a shorter median RT in the endocardium and in the epicardium of the RVOT and a higher dispersion of the ARI and RT across the epicardium in patients with PVCs from the RVOT when comparing to controls.

Global Electrical Heterogeneity: Mechanisms and Clinical Significance.

This review summarizes recent findings and discusses a clinical significance of a vectorcardiographic (VCG) Global electrical heterogeneity (GEH). GEH concept is based on the concept of the spatial ventricular gradient (SVG), which is a global measure of the dispersion of total recovery time. We quantify GEH by measuring five features of the SVG vector (SVG magnitude, direction (azimuth and elevation), a scalar value, and spatial QRS-T angle) on orthogonal XYZ ECG. In analysis of more than 20,000 adults we showed that GEH is independently associated with sudden cardiac death (SCD) after adjustment for demographics, cardiovascular disease (time-updated incident non-fatal cardiovascular events [coronary heart disease, heart failure, stroke, atrial fibrillation, use of beta-blockers], and known risk factors [cholesterol, triglycerides, physical activity index, smoking, diabetes, obesity, hypertension, anti-hypertensive medications, creatinine, alcohol intake, left ventricular ejection fraction, and time-updated ECG metrics (heart rate, QTc, QRS duration, ECG-left ventricular hypertrophy, bundle branch block or interventricular conduction delay)]. This finding suggests that GEH represents an independent electrophysiological substrate of SCD.

Simulation-Based Method of Capacity Utilization Evaluation to Account for Uncertainty in Recovery Time

A typical objective of a railway agency is to design an efficient and reliable service plan. Although enhancing the level of capacity utilization may increase efficiency, the stability of the service plan may also decrease due to stochastic railway disruptions. Past studies used recovery time to evaluate the stability of a service plan; however, the variation of recovery time was not fully examined. Therefore, we developed a Monte Carlo simulation framework to address this issue and proposed four capacity-based indices for the evaluation of service efficiency and stability. These indices are capacity utilization efficiency, mean recovery time, dispersion of recovery time, and probability of unacceptable recovery time. The latter two new indices explored the variation of recovery time and probability of unacceptable long recovery time, which is undesired for railway operation. We conducted a real-world case study on the Taiwan Railways Administration before and after the service plan revision. Consequently, the northbound service plan needed a deliberate review and revision before implementation, whereas the southbound plan successfully increased capacity usage while not necessarily worsening stability. This result demonstrated that our study introduced uncertainty analysis into the evaluation framework and provided flexible information on the service plan. These developments can provide improved support in the decision-making of railway agencies to strike a balance between service level and asset usage.

Diagnostic Value of Electrocardiogram in Predicting Exaggerated Blood Pressure Response to Exercise Stress Testing.

IntroductionIt is believed that an exaggerated blood pressure response (EBPR) to exercise stress test is associated with a higher risk of cardiovascular events. It is also assumed that QT dispersion (QT-d), which was originally proposed to measure the spatial dispersion of ventricular recovery times, may have a relationship to cardiovascular events. The objective of this study was to examine the difference of changes in QT-d, Maxi-QT, Mini-QT, and QT-c (corrected QT interval) of the electrocardiogram in two groups of patients with exaggerated blood pressure responses (EBPR group) and normal responses (control group) to exercise testing. Also, the diagnostic value of each of these criteria in the prediction of EBPR was studied.MethodsThis cross-sectional study was conducted from May 2015 to February 2016 on patients suspected of coronary artery disease (CAD) undergoing exercise testing who had been referred to Ghaem and Imam Reza hospitals in Mashhad (Iran). All patients underwent a treadmill exercise test with the 12-lead ECG, which was optically scanned and digitized for analysis of QT-d, QT max, and QT min. Patients were divided into two groups of normal and EBPR to exercise testing. QT changes of ECG were compared between the two groups, and the diagnostic accuracy of QT variables for prediction of EBPR to exercise testing was studied. A multiple linear regression analysis (MLR), Pearson Chi-qquare, independent samples t-test, and receiver operating characteristic (ROC) curve were used as statistical methods in IBM SPSS version 19.ResultsSixty patients (55% male) with a mean age of 50.48 ± 10.89 years were studied in two groups of normal (n=30) and exaggerated blood pressure response (n=30) to exercise testing. Maximum QT and QT dispersion were statistically different in individuals’ exaggerated blood pressure response to exercise stress test (p < 0.05). The logistic regression analysis revealed that none of our parameters predicted the EBPR. The ROC curve showed that 50 and 345 milliseconds for QT dispersion and Maxi-QT were the optimal cut-off points for the prediction of EBPR.ConclusionIt seems that Maxi-QT and QT-d may be predictors of EBPR during exercise testing. Also, a significant difference in maxi-QT and QT-d was observed between two groups of patients with normal and EBPR during the exercise testing.

Effect of Smoking on Tp-e Interval, Tp-e/QT and Tp-e/QTc Ratios as Indices of Ventricular Arrhythmogenesis

Smoking may lead to ventricular arrhythmias and sudden cardiac death via altering ventricular recovery time dispersion indices such as QT interval and QT dispersion (QTd). The Tp-e/QT and Tp-e/QTc ratios are also known as predictors of ventricular arrhythmogenesis. The aim of this study was to evaluate the relationship between cigarette smoking and ventricular repolarisation dispersion using these novel electrocardiographic parameters. One hundred and twenty-one chronic smokers and 70 age- and sex-matched non-smoker controls were included in our study. The Tp-e interval and Tp-e/QT ratio were measured by 12-lead electrocardiogram, and corrected for heart rate. QTd (34.2 ± 8.4, 27.2 ± 10.4, P<0.001) and corrected QTd (37.3 ± 8.9, 29.8 ± 11.2, P<0.001) were significantly increased in the smokers compared to the non-smoker control group. The Tp-e interval (76.5 ± 6.3, 70.3 ± 6.8, P<0.001), cTp-e interval (83.5 ± 8.0, 77.1 ± 8.7, P<0.001), Tp-e/QT (0.20 ± 0.03, 0.19 ± 0.02, P<0.001) and Tp-e/QTc ratios (0.19 ± 0.02, 0.17 ± 0.02, P<0.001) were increased in the patient group when compared to the controls. Significant positive correlations were also found between the level of smoking with the cTp-e interval (r=0.836, P<0.001), and Tp-e/QT (r=0.714, P<0.001) and Tp-e/QTc ratios (r=0.448, P<0.001). We found in our study that cTp-e interval, Tp-e/QT and Tp-e/QTc ratios were increased in smokers and significantly correlated to the amount of smoking.

Spatial and transmural repolarization, and dispersion of repolarization and late potentials evaluated using signal-averaged vector-projected 187-channel high-resolution electrocardiogram in Brugada syndrome

BackgroundVector-projected 187-channel electrocardiograms (ECGs) were recorded in 45 patients with a Brugada-type ECG to evaluate spatial and transmural repolarization and dispersion of action potential duration in Brugada syndrome (BS). MethodsCorrected recovery time (RT-c, R wave peak to the first positive maximum derivative of the T wave with Bazett correction) and RT-c dispersion were calculated. The corrected T peak-end interval (T(p-e)-c, T wave peak to the end of the T wave with Bazett correction) and T(p-e)-c dispersion were calculated. ResultsRT-c dispersion and T(p-e)-c interval were longer in patients with a type 1 ECG, but there was no significant difference in Tp-e dispersion between patients with a type 1 and those with a type 2/3 ECG. No significant correlation was noted between RT-c dispersion, T(p-e)-c dispersion, and symptoms. Late potentials (P=0.023) and a family history of sudden cardiac death (P=0.0017) were correlated with symptoms. ConclusionsSpatial dispersion of repolarization may constitute the electrocardiographic pattern of the Brugada type ECG and conduction disturbance in addition to repolarization abnormality may contribute to the development of malignant ventricular tachyarrhythmias.

Electrical storm after cardiac resynchronization therapy in a patient with nonischemic cardiomyopathy: Signal-averaged vector-projected 187-channel electrocardiogram-based risk stratification for lethal arrhythmia

We describe treatment of atrial flutter and electrical storm presenting as incessant ventricular tachycardia (VT) after implantation of a cardiac resynchronization therapy defibrillator (CRT-D) in a patient with dilated cardiomyopathy. No prior arrhythmic event had occurred. Our treatment strategy, including amiodarone administration, was guided in part by signal-averaged vector-projected 187-channel electrocardiogram (SAVP-ECG)-based risk stratification for ventricular arrhythmia. Corrected recovery time (RTc) dispersion and Tpeak-end dispersion were used to evaluate transmural dispersion of repolarization. RTc and Tpeak-end dispersion increased during the period of electrical storm. Values were improved 2 years after CRT-D implantation, and the amiodarone was discontinued. The VT has not recurred despite discontinuation of the antiarrhythmic agent. SAVP-ECG-based risk stratification for ventricular arrhythmia proved useful for the management of antiarrhythmic therapy.

Effect of Obstructive Sleep Apnea on Heart Rate, Heart Rate Recovery and QTc and P-wave Dispersion in Newly Diagnosed Untreated Patients

IntroductionObstructive sleep apnea syndrome (OSAS) is associated with autonomic dysfunction, whereas increased heart rate (HR), HR recovery time (HRR-1), QT-corrected interval (QTc) and P-wave dispersion (Pd) are associated with cardiovascular events. The aim of the current investigation was to clarify the influence of OSAS severity on these cardiac parameters. MethodsNinety newly diagnosed and untreated patients with OSAS underwent overnight polysomnography and cardiopulmonary exercise testing, including HRR-1, echocardiography, 24-hour Holter electrocardiography, surface electrocardiogram (ECG) and measurement of several metabolic parameters. The patients were divided into the following 4 groups: 26 with apnea-hypopnea index (AHI) <5, 20 with 5 ≤ AHI <15, 20 with 15 ≤ AHI <30 and 24 with AHI ≥30. QTc and Pd were calculated in all leads of the surface ECG. Mean HR was measured using 24-hour Holter ECG, and HRR-1 was measured using cardiopulmonary exercise testing. ResultsQTc was increased in patients with moderate-to-severe OSAS. Pd was significantly increased in patients with OSAS compared with those without OSAS. In addition, Pd was correlated with AHI and associated with the severity of disease. Mean HRs over a period of 24hours during wakefulness and sleep correlated significantly with AHI and the lowest SpO2 in patients with OSAS, whereas HRR-1 was inversely correlated with the severity of OSAS, as expressed by AHI. ConclusionWe showed that HR, Pd, HRR-1 and QT-corrected time are correlated with OSAS severity. Further studies are required in order to investigate the prognostic effect of HRR-1, Pd, HR and QTc in OSAS.

The peak-to-end of the T wave in the limb ECG leads reflects total spatial rather than transmural dispersion of ventricular repolarization in an anthopleurin-A model of prolonged QT interval

Previous studies have showed that the interval between the peak and the end of the T wave (Tp-e) is a marker of transmural dispersion of ventricular repolarization. We studied the relationship between (a) the Tp-e on local pseudo transmural electrograms (pseudo transmural Tp-e) or limb leads of body surface electrocardiogram (surface Tp-e) and (b) the intracardiac left ventricular (LV) repolarization during a drug-induced QT-interval prolongation. Using open-chested canine intact hearts treated by anthopleurin-A, transmural LV electrograms were recorded via needle electrodes placed in the basoanterior, midanterior, apicoanterior, basolateral, midlateral, and apicolateral LV wall. Recovery time (RT) was calculated as an index of local repolarization at each transmural unipolar electrode. This model showed slower heart rate-dependent heterogeneous distribution of ventricular repolarization both along the basal to apical axis and along the transmural axis. RT was longer at the LV apex than at the base and longer in the lateral than in the anterior wall during the slower heart rate. A high correlation was found between surface Tp-e and total LV dispersion. In contrast, pseudo transmural Tp-e correlated with transmural RT dispersion. The shortest RT in the heart roughly corresponded to the peak, as did the longest RT with the end of the T wave on the surface electrocardiogram. During drug-induced QT-interval prolongation with a large apicobasal and anterolateral dispersion of ventricular repolarization, the Tp-e in the limb leads expresses spatial (total) distribution of repolarization in the whole left ventricle.

High-energy defibrillation increases the dispersion of regional ventricular repolarization

This study evaluated the effects of shock energy on the dispersion of regional ventricular repolarization (DRVR), post-shock rhythm and sinus recovery time (SRT), and the relationship between DRVR and post-shock ventricular arrhythmias. Ten open-chest dogs were anesthetized. Ventricular fibrillation (VF) was electrically induced and recorded from a 6 × 6 unipolar electrode plaque (4 mm spacing) sutured on the left ventricular epicardium. Defibrillation threshold (DFT) was determined after 20 s of VF. DRVR was measured before VF, during the earliest post-shock sinus rhythm, and during sinus rhythm 30 s following shocks. Post-shock rhythm and SRT were evaluated after energies of 100% DFT, 125% DFT, 175% DFT, and 250% DFT. In the100% DFT group, the DRVR of the earliest sinus rhythm and 30 s after successful defibrillation was not significantly different than that before VF. But the DRVRs were significantly increased in 125% DFT, 175% DFT, and 250% DFT group. DRVR after defibrillation in the 250% DFT group was higher than those in the 100% DFT and 125% DFT groups. SRT in the 250% DFT group was significantly longer than that in the other groups .The incidence of post-shock ventricular tachycardia was increased when a high-shock energy was applied (P = 0.041). DRVR was increased by application of high-energy defibrillation associated with SRT prolongation. The increased DRVR may play an important role in the onset of post-shock ventricular tachycardia.

Renal Dysfunction, Recovery Time Dispersion and Ventricular Arrhythmias in Heart Failure Patients Receiving Cardiac Resynchronization Therapy Defibrillator

Introduction: The aim of this study is to evaluate the influence of renal dysfunction and recovery time dispersion on the occurrence of arrhythmic events in HF patients receiving Cardiac resynchronization therapy (CRT)-implantable cardioverter defibrillator (ICD) devices (CRT-D) without a history of cardiac arrest or sustained ventricular tachycardia. Methods: We studied 80 HF patients who underwent CRT-D implantation from 2007 to 2010 and had indications for ICD for primary prevention of sudden cardiac death. Renal dysfunction was defined as eGFR<60 mL/min/1.73 m2. 187-ch repolarization interval-difference mapping electrocardiograph (187-ch RIDM-ECG) were performed after the implantation and the inter-lead difference between corrected T peak to T end intervals (Tp-e) were analyzed. Results: During mean follow-up time of 13±7 months, 16 patients (20%) experienced appropriate ICD therapy. There was a significantly higher incidence of appropriate ICD therapy in patients with renal dysfunction than without (35% vs. 12%, p<0.05). Among patients with renal dysfunction, there was a significantly higher inter-lead difference between Tp-e (82±30 vs 63±30 msec, p<0.05) in patients with appropriate ICD therapy than without. Conclusion: Both renal dysfunction and recovery time dispersion were associated with a higher incidence ICD therapy in HF patients receiving CRT-D.

Increased Spatial Dispersion of the Ventricular Recovery Time in Patients with Idiopathic Ventricular Fibrillation

Background: Diagnosis of idiopathic ventricular fibrillation (IVF) before its occurrence is challenging, because cardiac arrest could represent the first or the only sign of the disease. Heterogeneity of ventricular repolarization has been consistently reported to be linked to ventricular tachycardias. The purpose of this study was to test the hypothesis that IVF also might be associated with ventricular repolarization abnormalities. Methods and Results: Spatial dispersion of recovery time as an index of heterogeneity of ventricular repolarization was assessed by means of a 187-channel signal-averaged vector-projected high-resolution electrocardiograph (187-ch SAVP-ECG) in a group of 6 consecutive patients (6 male, 43±20 year-old) who were diagnosed with IVF and who received ICDs for secondary prevention after an episode of resuscitated sudden cardiac death. A control group consisting of 17 healthy persons (17 male, 29±5 year-old) was set for comparison. Recordings took a maximum of 10 minutes. Spatial dispersion of corrected recovery time (defined as the time between the R wave peak and the first positive maximum derivative of T wave corrected by Bazett’s formula) was significantly higher in the IVF group compared with controls (98±19 milliseconds versus 59±18 milliseconds p<0.001). Conclusions: 187-ch SAVP-ECG is a simple and reliable method for the evaluation of ventricular repolarization. It may be useful to reveal patients with latent IVF.

Risk Stratification of Ventricular Fibrillation by Two-Dimensional Functional Image of Repolarization Dispersion and T-Wave Alternance Using Synthesized 187-Channel ECG

We developed synthesized 187 channel high-resolution ECG (187ch DREAM-ECG) that can evaluate simultaneously two-dimensional functional images of late potential (LP), RTpeak-end and T-wave current alternance (TWCA) using Mason-Likar lead system. We evaluated the significance of a risk stratification for ventricular fibrillation (VF). The subjects consisted of 20 healthy subject (CONT) and 10 patients with VF (1 idiopathic VF (IVF), 5 long QT syndrome, 2 Brugada syndrome, 1 sarcoidosis and 1 myocardial infarction). We recorded 10 min of 187ch DREAM-ECG. Two-dimensional functional images of recovery time (RTpeak-end; RTp-e) dispersion and LP were obtained by the signal-averaged 187ch VP-ECG. The TWCA value was determined from the relative changes in the averaged current density in the T-wave zone (Tpeak±50 ms) for two T-wave types. In the IVF and LQT with VF case, values of RTpeak-end dispersion and TWCA were higher than those in CONT (RTp-e dispersion; 63±12 ms vs. 26±16 ms, TWCA; 6.5±7.3% vs. 0.5±0.2%). For the Brugada syndrome with VF, positive LP and increased RTc dispersion was demonstrated. For the MI and sarcoidosis with VF, positive LP and increased RTp-e dispersion were associated. We conclude that a novel algorithm using 187ch DREAM-ECG might provide new insights on a risk stratification of VF.

Novel algorithm for identifying T-wave current density alternans using synthesized 187-channel vector-projected body surface mapping

The noninvasive evaluation of ventricular T-wave alternans (TWA) in patients with lethal ventricular arrhythmias is an important issue. In this study, we propose a novel algorithm to identify T-wave current density alternans (TWCA) using synthesized 187-channel vector-projected body surface mapping (187-ch SAVP-ECG). We recorded 10 min of 187-ch SAVP-ECG using a Mason-Likar lead system in the supine position. A recovery time (RT) dispersion map was obtained by averaging the 187-ch SAVP-ECG. The TWCA value was determined from the relative changes in the averaged current density in the T-wave zone (Tpeak ± 50 ms) for two T-wave types. We registered 20 ECG recordings from normal controls and 11 ECG recordings from nine subjects with long QT syndrome (LQT). We divided LQT syndrome subjects into two groups: group 1 provided 9 ECG recordings without visually apparent TWAs, and group 2 provided 2 ECG recordings with visually apparent TWAs. The QTc interval values in the LQT groups were higher than those in the control (515 ± 60 ms in LQT G-1, 600 ± 27 ms in LQT G-2 vs. 415 ± 19 ms in control, P < 0.001). The RTendc dispersion values among the LQT subjects were higher than those of the control subjects (48 ± 19 ms in LQT G-1, 65 ± 30 ms in LQT G-2 vs. 24 ± 10 ms in control, P < 0.01). The mean TWCA value was significantly higher in the LQT G-2 group with visually apparent TWCAs (0.5 ± 0.2% in control, 2.1 ± 1.2% in LQT G-1, and 32.3 ± 6.9% in LQT G-2). Interestingly, the two-dimensional distribution of TWCA in LQT was inhomogeneous and correlated with the distribution of increased RT dispersion. We conclude that a novel algorithm using 187-ch SAVP-ECG might provide new insights into body surface TWCA.

Ventricular electrophysiology in congestive heart failure and its correlation with heart rate variability and baroreflex sensitivity: a canine model study

This study investigated ventricular electrophysiological characteristics and the correlation between these parameters and heart rate variability (HRV) and baroreflex sensitivity (BRS) in a canine congestive heart failure (CHF) model. Haemodynamics, HRV, BRS, and ventricular electrophysiological variables were measured 4-5 weeks after sham operation (control dogs) and pacemaker implantation, and rapid right ventricular pacing at 240 bpm (CHF group). In the CHF group, significant differences from the control group in ventricular effective refractory period (VERP), monophasic action potential (MAP) duration (MAPD(90)), ventricular late repolarization duration (VLRD), the ratio of VERP to MAPD(90), dispersion of ventricular recovery time (VRT-D), and ventricular fibrillation threshold (VFT) were noted. Both BRS and the time and power domain parameters of HRV were significantly decreased in the CHF group compared with the control group, and a significant, positive correlation between HRV and BRS was identified in the CHF group. Heart rate variability and BRS were negatively and significantly correlated with VLRD and VRT-D, and were positively correlated with VERP/MAPD(90) and VFT in the CHF group. These results suggest that ventricular electrophysiological characteristics correlated with abnormal autonomic nerve function may have important effects on sudden cardiac death. Further research is warranted.

Newly Developed Signal-Averaged Vector-Projected 187-Channel Electrocardiogram Can Evaluate the Spatial Distribution of Repolarization Heterogeneity

The purpose of this study was to verify the spatial distribution of myocardial repolarization heterogeneity using a newly developed 187-channel signal-averaged vector-projected ECG (187-ch SAVP-ECG). We constructed corrected recovery time (RTc) and Tpeak-end (corrected Tp-e) dispersion maps using a 187-ch SAVP-ECG based on vector-projection theory using a Mason-Likar lead system. We compared the spatial distribution and quantitative values of dispersion maps by 187-ch SAVP-ECG with those by 64-ch magnetocardiography (MCG) in 27 normal controls (control) and 16 patients (12 myocardial infarction (MI), and 4 dilated cardiomyopathy (DCM)). The wave pattern of the 187-ch SAVP-ECG in the representative cases was similar to those in 64-ch MCG. Spatial distribution increased RTc and corrected Tp-e dispersion maps defined by 187-ch SAVP-ECG were in agreement with those by 64-ch MCG. The value of RTc dispersion in MI was higher than that in control (41 +/- 21 ms in MI versus 30 +/- 12 ms in control, P < 0.05). The value of corrected Tp-e dispersion in DCM was higher than that in control (58 +/- 12 ms in DCM versus 30 +/- 13 ms in control, P < 0.001). There was a good correlation between RTc and corrected Tp-e dispersion values determined by 187-ch SAVP-ECG and 64-ch MCG modalities (y = 0.46x + 18, r = 0.62, P = 0.02 for RTc dispersion; y = 0.52x + 15, r = 0.63, P = 0.01 for corrected Tp-e dispersion). RTc and corrected Tp-e dispersion maps by 187-ch SAVP-ECG based on vector-projection theory can evaluate the spatial distribution of myocardial repolarization heterogeneity.

Development of a Signal-Averaged Vector-Projected 187-Channel High-Resolution Electrocardiogram for the Evaluation of the Spatial Location of High-Frequency Potentials and Abnormal Ventricular Repolarization

Noninvasive risk stratification is important for screening for lethal arrhythmia. We developed a 187-channel signal-averaged vector-projected high-resolution electrocardiograph (187-ch SAVP-ECG) for detecting abnormalities in the spatial location of ventricular high-frequency late potentials (HFLPs) and ventricular repolarization. The subjects consisted of 30 normal controls (CONTROL) and 13 patients with HFLPs (6 with myocardial infarction [MI], 6 with cardiomyopathy, and 1 with Brugada syndrome). The modified X, Y, Z-lead ECG and the synthesized signals from vector-projected 187-channel ECGs were amplified and passed through a digital filter. We calculated the integration of the HFLPs area between QRS(end) and 30 ms before QRS(end). The integrated HFLPs map was superimposed on the corrected recovery time (RTc) and Tpeak-end dispersion maps composed by 187-ch SAVP-ECG. All patients received an examination by 64-channel magnetocardiography (64-ch MCG) on the same day. The spatial distribution of HFLPs by the 187-ch SAVP-ECG map was in agreement with the location of increased RT dispersion in MI. The spatial distribution of HFLPs in DCM demonstrated a wide variety of patterns. Interestingly, the spatial distribution of HFLPs in cases with ARVC was located at around a right ventricular outflow region. The spatial distribution of HFLPs by 187-ch SAVP-ECG was in agreement with those determined by 64-ch MCG. The 187-ch SAVP-ECG might be useful for evaluating the spatial distribution of nonuniform conduction and ventricular repolarization heterogeneity.

Three-dimensional recovery time dispersion map by 64-channel magnetocardiography may demonstrate the location of a myocardial injury and heterogeneity of repolarization

QT dispersion reveals heterogeneities in the repolarization time in the three-dimensional (3D) structure of the ventricular myocardium. In this study, we report on a 3D function map of recovery time (RT) dispersions as measured by 64-channel magnetocardiography (MCG). MCG were simultaneously recorded in 29 controls and 21 patients with previous myocardial infarction (MI). The 3D current density was calculated from 64-channel MCG data in the Bz component using a space filter. The heart outline, reconstructed from the integrated the current density, revealed both the atrium and ventricle. The RT for the intervals between QRS onset and the time of the maximum dT/dt of T wave, and the peak to the end of the T wave (T(peak)-negative dT/dt) were automatically measured by means of a computer from 3D MCG data. The corrected RT (RTc) and corrected T(peak)-negative dT/dt were then calculated using Bazett's formula. The 3D RTc and the corrected T(peak)-negative dT/dt dispersion map were superimposed on the heart outline generated by MCG. The RTc was significantly longer for the MI group than in the control group (67+/-25 ms1/2 vs. 16+/-6 ms1/2) (p<0.0001). The corrected T(peak)-negative dT/dt dispersions in each patient was also significantly longer for the MI group than in the control group (35+/-27 ms1/2 vs. 10+/-5 ms1/2) (p<0.0001). Furthermore, the 3D RTc and T(peak)-negative dT/dt dispersion maps corresponded with the space location of MI, as defined by Tc-99m tetrofosmin myocardial imaging 3D RTc and T(peak)-negative dT/dt dispersion maps in the ST segment, obtained by 64-channel MCG may be used demonstrate the location of a myocardial injury and heterogeneities of repolarization.

Intramural activation and repolarization sequences in canine ventricles. Experimental and simulation studies

Background There are no published data showing the three-dimensional sequence of repolarization and the associated potential fields in the ventricles. Knowledge of the sequence of repolarization has medical relevance because high spatial dispersion of recovery times and action potential durations favors cardiac arrhythmias. In this study we describe measured and simulated 3-D excitation and recovery sequences and activation-recovery intervals (ARIs) (measured) or action potential durations (APDs) (simulated) in the ventricular walls. Methods We recorded from 600 to 1400 unipolar electrograms from canine ventricular walls during atrial and ventricular pacing at 350-450 ms cycle length. Measured excitation and recovery times and ARIs were displayed as 2-D maps in transmural planes or 3-D maps in the volume explored, using specially developed software. Excitation and recovery sequences and APD distributions were also simulated in parallelepipedal slabs using anisotropic monodomain or bidomain models based on the Lou-Rudy version 1 model with homogeneous membrane properties. Results Simulations showed that in the presence of homogeneous membrane properties, the sequence of repolarization was similar but not identical to the excitation sequence. In a transmural plane perpendicular to epicardial fiber direction, both activation and recovery pathways starting from an epicardial pacing site returned toward the epicardium at a few cm distance from the pacing site. However, APDs were not constant, but had a dispersion of ∼14 ms in the simulated domain. The maximum APD value was near the pacing site and two minima appeared along a line perpendicular to fiber directions, passing through the pacing site. Electrical measurements in dog ventricles showed that, for short cycle lengths, both excitation and recovery pathways, starting from an epicardial pacing site, returned toward the epicardium. For slower pacing rates, pathways of recovery departed from the pathway of excitation. Highest ARI values were observed near the pacing site in part of the experiments. In addition, maps of activation-recovery intervals showed mid-myocardial clusters with activation-recovery intervals that were slightly longer than ARIs closer to the epi- or endocardium, suggesting the presence of M cells in those areas. Transmural dispersion of measured ARIs was on the order of 20-25 ms. Potential distributions during recovery were less affected by myocardial anisotropy than were excitation potentials.