The Experts below are selected from a list of 3474 Experts worldwide ranked by ideXlab platform
David S Rosenbaum - One of the best experts on this subject based on the ideXlab platform.
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mechanism linking t wave alternans to the genesis of cardiac fibrillation
Circulation, 1999Co-Authors: Joseph M Pastore, Fadi G Akar, Steven D Girouard, Kenneth R Laurita, David S RosenbaumAbstract:Background—Although T-wave alternans has been closely associated with vulnerability to ventricular arrhythmias, the cellular processes underlying T-wave alternans and their role, if any, in the mechanism of reentry remain unclear. Methods and Results—T-wave alternans on the Surface ECG was elicited in 8 Langendorff-perfused guinea pig hearts during fixed-rate pacing while action potentials were recorded simultaneously from 128 Epicardial sites with voltage-sensitive dyes. Alternans of the repolarization phase of the action potential was observed above a critical threshold heart rate (HR) (209±46 bpm) that was significantly lower (by 57±36 bpm) than the HR threshold for alternation of action potential depolarization. The magnitude (range, 2.7 to 47.0 mV) and HR threshold (range, 171 to 272 bpm) of repolarization alternans varied substantially between cells across the Epicardial Surface. T-wave alternans on the Surface ECG was explained primarily by beat-to-beat alternation in the time course of cellular re...
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implications of ion channel diversity to ventricular repolarization and arrhythmogenesis insights from high resolution optical mapping
Canadian Journal of Cardiology, 1997Co-Authors: Kenneth R Laurita, David S RosenbaumAbstract:Recent evidence from experiments in isolated cells suggests that substantial ion channel diversity exists throughout the heart. However, due to limitations of conventional electrophysiological recording techniques, the influence of ion channel diversity on ventricular repolarization and arrhythmia vulnerability at the level of the intact heart are poorly understood. High resolution optical mapping with voltage-sensitive dye was used to measure significant heterogeneity in the kinetics of cellular repolarization between cells across the Epicardial Surface (1 x 1 cm) of the intact guinea-pig heart. Such diversity of repolarization kinetics modulates dispersion of repolarization in a biphasic fashion as premature coupling interval is shortened. Moreover, evidence is provided that modulation of repolarization by a premature stimulus in a coupling interval-dependent manner also modulates arrhythmia vulnerability in parallel, ie, 'modulated dispersion' hypothesis. Therefore, due to diversity of repolarization kinetics between Epicardial cells, a premature stimulus serves not only as a 'trigger' of arrhythmias, but also importantly modulates spatial dispersion of repolarization and the arrhythmogenic substrate for reentry.
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modulation of ventricular repolarization by a premature stimulus role of Epicardial dispersion of repolarization kinetics demonstrated by optical mapping of the intact guinea pig heart
Circulation Research, 1996Co-Authors: Kenneth R Laurita, Steven D Girouard, David S RosenbaumAbstract:Recent evidence suggests that ion channels governing the response of action potential duration (APD) to a premature stimulus (ie, APD restitution) are heterogeneously dispersed throughout the heart. However, because of limitations of conventional electrophysiological recording techniques, the effects of restitution in single cells on ventricular repolarization at the level of the intact heart are poorly understood. Using high-resolution optical mapping with voltage-sensitive dyes, we measured APD restitution kinetics at 128 simultaneous sites on the Epicardial Surface (1 cm2) of intact guinea pig hearts (n=15). During steady state baseline pacing, APD gradients that produced a spatial dispersion of repolarization were observed. Mean APD was shortened monotonically from 186±19 ms during baseline pacing (S1-S1 cycle length, 393±19 ms) to 120±4 ms as single premature stimuli were introduced at progressively shorter coupling intervals (shortest S1-S2, 190±15 ms). In contrast, premature stimuli caused biphasic modulation of APD dispersion (defined as the variance of APD measured throughout the mapping field). Over a broad range of increasingly premature coupling intervals, APD dispersion decreased from 70±29 ms2 to a minimum of 10±7 ms2 at a critical S1-S2 interval (216±18 ms), and then, at shorter premature coupling intervals, APD dispersion increased sharply to 66±25 ms2. Modulation of APD dispersion by premature stimuli was attributed to coupling interval–dependent changes in the magnitude and direction of ventricular APD gradients, which, in turn, were explained by systematic heterogeneities of APD restitution across the Epicardial Surface. There was a characteristic pattern in the spatial distribution of cellular restitution such that faster restitution kinetics were closely associated with longer baseline APD. This relationship explained the reversal of APD between single cells, inversion of APD gradients across the heart, and ECG T-wave inversion during closely coupled premature stimulation. Therefore, because of the heterogeneous distribution of cellular restitution kinetics across the Epicardial Surface, a single premature stimulus profoundly altered the pattern and synchronization of ventricular repolarization in the intact ventricle. This response has important mechanistic implications in the initiation of arrhythmias that are dependent on dispersion of repolarization.
Thomas H Mcelderry - One of the best experts on this subject based on the ideXlab platform.
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challenging radiofrequency catheter ablation of idiopathic ventricular arrhythmias originating from the left ventricular summit near the left main coronary artery
Circulation-arrhythmia and Electrophysiology, 2016Co-Authors: Takumi Yamada, Harish Doppalapudi, Silvio H Litovsky, Thomas H McelderryAbstract:Background— Radiofrequency catheter ablation (RFCA) of idiopathic ventricular arrhythmias (VAs) originating from the basal portion of the left ventricular (LV) summit, which is divided from the apical LV (A-LV) summit by the great cardiac vein (GCV), is challenging. This study investigated the efficacy of RFCA and electrocardiographic and electrophysiological characteristics of these VAs. Methods and Results— Forty-five consecutive patients with symptomatic idiopathic LV summit VAs were studied. RFCA was successful within the main trunk of the GCV in 16 patients and within a branch of the GCV traversing the basal LV (B-LV) summit in 7. Transpericardial RFCA was successful on the Epicardial Surface in the A-LV summit in 6 patients and was abandoned in 14 with the B-LV summit VAs because of the close proximity to the coronary arteries and thick fat pads. RFCA was successful at the aortomitral continuity in 3 patients (2 with a failed transpericardial RFCA), and left coronary cusp in 1. The RFCA success rate of the A-LV summit VAs including the GCV VAs was 100% (22/22), whereas that of the B-LV summit VAs was 48% (11/23). The B-LV summit VAs could be differentiated from the A-LV summit VAs by left bundle branch block pattern, QRS duration ≤175 ms, precordial transition ≥V1, and maximum deflection index of ≥0.55. Conclusions— This study revealed that ≈50% of the B-LV summit VAs could be eliminated by a direct approach through a GCV branch running below the proximal left coronary arteries and a remote approach from the adjacent endocardial sites.
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ventricular tachycardia with a myocardial fibre travelling from the origin in the right aortic sinus cusp to the Epicardial breakout site of the right ventricular outflow tract
Europace, 2008Co-Authors: Takumi Yamada, Thomas H Mcelderry, Harish Doppalapudi, Neal G KayAbstract:A 74-year-old man with idiopathic ventricular tachycardia (VT) with a QRS morphology with a left bundle branch block and right inferior axis underwent electrophysiologic testing. Successful ablation was achieved at the right coronary cusp (RCC) where an excellent pace map with long stimulus-to-QRS interval (St-QRS) (85 ms) was obtained. An excellent pace map was also obtained on the Epicardial Surface ∼1 cm away from the successful ablation site and the St-QRS was shorter (40 ms). These findings suggested that a myocardial fibre travelling from the origin in the RCC to the epicardium of the right ventricular outflow tract might exist.
Takumi Yamada - One of the best experts on this subject based on the ideXlab platform.
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challenging radiofrequency catheter ablation of idiopathic ventricular arrhythmias originating from the left ventricular summit near the left main coronary artery
Circulation-arrhythmia and Electrophysiology, 2016Co-Authors: Takumi Yamada, Harish Doppalapudi, Silvio H Litovsky, Thomas H McelderryAbstract:Background— Radiofrequency catheter ablation (RFCA) of idiopathic ventricular arrhythmias (VAs) originating from the basal portion of the left ventricular (LV) summit, which is divided from the apical LV (A-LV) summit by the great cardiac vein (GCV), is challenging. This study investigated the efficacy of RFCA and electrocardiographic and electrophysiological characteristics of these VAs. Methods and Results— Forty-five consecutive patients with symptomatic idiopathic LV summit VAs were studied. RFCA was successful within the main trunk of the GCV in 16 patients and within a branch of the GCV traversing the basal LV (B-LV) summit in 7. Transpericardial RFCA was successful on the Epicardial Surface in the A-LV summit in 6 patients and was abandoned in 14 with the B-LV summit VAs because of the close proximity to the coronary arteries and thick fat pads. RFCA was successful at the aortomitral continuity in 3 patients (2 with a failed transpericardial RFCA), and left coronary cusp in 1. The RFCA success rate of the A-LV summit VAs including the GCV VAs was 100% (22/22), whereas that of the B-LV summit VAs was 48% (11/23). The B-LV summit VAs could be differentiated from the A-LV summit VAs by left bundle branch block pattern, QRS duration ≤175 ms, precordial transition ≥V1, and maximum deflection index of ≥0.55. Conclusions— This study revealed that ≈50% of the B-LV summit VAs could be eliminated by a direct approach through a GCV branch running below the proximal left coronary arteries and a remote approach from the adjacent endocardial sites.
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ventricular tachycardia with a myocardial fibre travelling from the origin in the right aortic sinus cusp to the Epicardial breakout site of the right ventricular outflow tract
Europace, 2008Co-Authors: Takumi Yamada, Thomas H Mcelderry, Harish Doppalapudi, Neal G KayAbstract:A 74-year-old man with idiopathic ventricular tachycardia (VT) with a QRS morphology with a left bundle branch block and right inferior axis underwent electrophysiologic testing. Successful ablation was achieved at the right coronary cusp (RCC) where an excellent pace map with long stimulus-to-QRS interval (St-QRS) (85 ms) was obtained. An excellent pace map was also obtained on the Epicardial Surface ∼1 cm away from the successful ablation site and the St-QRS was shorter (40 ms). These findings suggested that a myocardial fibre travelling from the origin in the RCC to the epicardium of the right ventricular outflow tract might exist.
Kenneth R Laurita - One of the best experts on this subject based on the ideXlab platform.
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mechanism linking t wave alternans to the genesis of cardiac fibrillation
Circulation, 1999Co-Authors: Joseph M Pastore, Fadi G Akar, Steven D Girouard, Kenneth R Laurita, David S RosenbaumAbstract:Background—Although T-wave alternans has been closely associated with vulnerability to ventricular arrhythmias, the cellular processes underlying T-wave alternans and their role, if any, in the mechanism of reentry remain unclear. Methods and Results—T-wave alternans on the Surface ECG was elicited in 8 Langendorff-perfused guinea pig hearts during fixed-rate pacing while action potentials were recorded simultaneously from 128 Epicardial sites with voltage-sensitive dyes. Alternans of the repolarization phase of the action potential was observed above a critical threshold heart rate (HR) (209±46 bpm) that was significantly lower (by 57±36 bpm) than the HR threshold for alternation of action potential depolarization. The magnitude (range, 2.7 to 47.0 mV) and HR threshold (range, 171 to 272 bpm) of repolarization alternans varied substantially between cells across the Epicardial Surface. T-wave alternans on the Surface ECG was explained primarily by beat-to-beat alternation in the time course of cellular re...
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implications of ion channel diversity to ventricular repolarization and arrhythmogenesis insights from high resolution optical mapping
Canadian Journal of Cardiology, 1997Co-Authors: Kenneth R Laurita, David S RosenbaumAbstract:Recent evidence from experiments in isolated cells suggests that substantial ion channel diversity exists throughout the heart. However, due to limitations of conventional electrophysiological recording techniques, the influence of ion channel diversity on ventricular repolarization and arrhythmia vulnerability at the level of the intact heart are poorly understood. High resolution optical mapping with voltage-sensitive dye was used to measure significant heterogeneity in the kinetics of cellular repolarization between cells across the Epicardial Surface (1 x 1 cm) of the intact guinea-pig heart. Such diversity of repolarization kinetics modulates dispersion of repolarization in a biphasic fashion as premature coupling interval is shortened. Moreover, evidence is provided that modulation of repolarization by a premature stimulus in a coupling interval-dependent manner also modulates arrhythmia vulnerability in parallel, ie, 'modulated dispersion' hypothesis. Therefore, due to diversity of repolarization kinetics between Epicardial cells, a premature stimulus serves not only as a 'trigger' of arrhythmias, but also importantly modulates spatial dispersion of repolarization and the arrhythmogenic substrate for reentry.
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modulation of ventricular repolarization by a premature stimulus role of Epicardial dispersion of repolarization kinetics demonstrated by optical mapping of the intact guinea pig heart
Circulation Research, 1996Co-Authors: Kenneth R Laurita, Steven D Girouard, David S RosenbaumAbstract:Recent evidence suggests that ion channels governing the response of action potential duration (APD) to a premature stimulus (ie, APD restitution) are heterogeneously dispersed throughout the heart. However, because of limitations of conventional electrophysiological recording techniques, the effects of restitution in single cells on ventricular repolarization at the level of the intact heart are poorly understood. Using high-resolution optical mapping with voltage-sensitive dyes, we measured APD restitution kinetics at 128 simultaneous sites on the Epicardial Surface (1 cm2) of intact guinea pig hearts (n=15). During steady state baseline pacing, APD gradients that produced a spatial dispersion of repolarization were observed. Mean APD was shortened monotonically from 186±19 ms during baseline pacing (S1-S1 cycle length, 393±19 ms) to 120±4 ms as single premature stimuli were introduced at progressively shorter coupling intervals (shortest S1-S2, 190±15 ms). In contrast, premature stimuli caused biphasic modulation of APD dispersion (defined as the variance of APD measured throughout the mapping field). Over a broad range of increasingly premature coupling intervals, APD dispersion decreased from 70±29 ms2 to a minimum of 10±7 ms2 at a critical S1-S2 interval (216±18 ms), and then, at shorter premature coupling intervals, APD dispersion increased sharply to 66±25 ms2. Modulation of APD dispersion by premature stimuli was attributed to coupling interval–dependent changes in the magnitude and direction of ventricular APD gradients, which, in turn, were explained by systematic heterogeneities of APD restitution across the Epicardial Surface. There was a characteristic pattern in the spatial distribution of cellular restitution such that faster restitution kinetics were closely associated with longer baseline APD. This relationship explained the reversal of APD between single cells, inversion of APD gradients across the heart, and ECG T-wave inversion during closely coupled premature stimulation. Therefore, because of the heterogeneous distribution of cellular restitution kinetics across the Epicardial Surface, a single premature stimulus profoundly altered the pattern and synchronization of ventricular repolarization in the intact ventricle. This response has important mechanistic implications in the initiation of arrhythmias that are dependent on dispersion of repolarization.
Jeremy N. Ruskin - One of the best experts on this subject based on the ideXlab platform.
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Endocardial, Intramural, and Epicardial Activation Patterns During Sustained Monomorphic Ventricular Tachycardia
2016Co-Authors: In Late, Hasan Garan, Canine Myocardial Infarction, John T. Fallon, Simon Rosenthal, Jeremy N. RuskinAbstract:Thirteen dogs in whom at least one morphologically distinct sustained ventricular tachycardia (VT) could be reproducibly initiated by programmed cardiac stimulation 18 ± 3 days following experimen-tal myocardial infarction were placed on total cardiopulmonary bypass for detailed study of the endocardial and Epicardial activation during VT under hemodynamically stable conditions. Thirteen morphologically distinct monomorphic VTs were investigated by simultaneous Epicardial, endocar-dial, and intramural bipolar recordings. Local electrograms were used to generate computer-assisted isochronous-activation sequence maps. A complete reentry circuit could be mapped on the Epicardial Surface in 4 animals and on the endocardial Surface in one other animal. In the remaining 8 animals, there was a gap period lasting 43-62 msec in the cardiac cycle during which no endocardial or Epicardial activity was observed. In 6 of the 8 animals, bipolar intramural recordings from sites closely associated with regions of endocardial and Epicardial conduction block showed intramural activity progressing slowly during the gap period. In these 6 animals, a reentry circuit could be completed by incorporating the local electrograms recorded from the intramural sites. VT could be reproducibly terminated by selectively rendering only these intramural sites refractory by critically timed extra-stimuli that failed to result in global ventricular capture. VT could be terminated by Epicardial coolin
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1A Novel Lead Configuration for Optimal Spatio-Temporal Detection of
2016Co-Authors: Intracardiac Repolarization Alternans, Jeremy N. Ruskin, Md Antonis, A. ArmoundasAbstract:Background- Electrical alternans is a pattern of variation in the shape of electrocardiographic waveform that occurs every other beat. In humans, alternation in ventricular repolarization, known as repolarization alternans (RA), has been associated with increased vulnerability to ventricular tachycardia/fibrillation and sudden cardiac death. Methods and Results- This study investigates the spatio-temporal variability of intracardiac RA and its relationship to body Surface RA in an acute myocardial ischemia model in swine. We developed a real-time multi-channel repolarization signal acquisition, display and analysis system to record electrocardiographic signals from catheters in the right ventricle, coronary sinus, left ventricle, and Epicardial Surface prior to and following circumflex coronary artery balloon occlusion. We found that RA is detectable within 4 minutes following the onset ischemia, and is most prominently seen during the first half of the repolarization interval. Ischemia-induced RA was detectable on unipolar and bipolar leads (both in near- and far-field configurations) and on body Surface leads. Far-field bipolar intracardiac leads were more sensitive for RA detection than body Surface leads, with the probability of body Surface RA detection increasing as the number of intracardiac leads detecting RA increased, approachin
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catheter ablation of ventricular Epicardial tissue a comparison of standard and cooled tip radiofrequency energy
Circulation, 2004Co-Authors: Andre Davila, Christopher Houghtaling, Jeremy N. Ruskin, Paulo Sampaio Gutierrez, Olivera Vragovic, Mark E Josephson, Vivek Y. ReddyAbstract:Background— Transthoracic Epicardial catheter ablation is an emerging catheter ablation strategy being used clinically at increasing frequency. However, the efficacy of standard RF ablation on the Epicardial Surface of the heart is hindered by (1) the lack of convective cooling of the ablation electrode and (2) the varying presence of Epicardial adipose tissue interposed between the ablation electrode and the target site. This experimental animal study examines the biophysical characteristics of radiofrequency (RF) ablation lesions generated by either standard or cooled-tip ablation of the ventricular epicardium. Methods and Results— Nonsurgical subxyphoid pericardial access was achieved in 10 normal goats and 7 pigs with healed myocardial infarctions. A 4-mm cooled-tip RF ablation catheter (continuous 0.9% saline circulation at 0.6 mL/s; goal temperature, 40°C; 60 seconds) was used to deliver Epicardial ventricular lesions: 47 in normal tissue and 22 in infarcted tissue. Standard RF ablation lesions (n=3...
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combined Epicardial and endocardial electroanatomic mapping in a porcine model of healed myocardial infarction
Circulation, 2003Co-Authors: Vivek Y. Reddy, Christopher Houghtaling, Mark E Josephson, David Wrobleski, Jeremy N. RuskinAbstract:Background— Substrate mapping of post–myocardial infarction ventricular tachycardia involves electroanatomic delineation of scarred tissue on the basis of electrogram characteristics during sinus rhythm. A percutaneous transthoracic technique was recently described that allows catheter mapping of the Epicardial Surface of the heart. This study sought to determine whether the Epicardial extent of a myocardial infarct could be defined during sinus rhythm. Methods and Results— In a porcine model of healed anterior wall myocardial infarction (n=13 animals), detailed in vivo left ventricular endocardial and ventricular Epicardial electroanatomic mapping was performed. Catheter access to the pericardial space was achieved by subxyphoid puncture under fluoroscopic guidance. Bipolar electrogram amplitude and duration characteristics of normal tissue were established on the basis of in vivo Epicardial mapping data in 8 additional normal animals. With the use of these criteria, radiofrequency lesions (4 to 11 per a...