scholarly journals Effects of local activation times on the tension development of human cardiomyocytes in a computational model

2018 ◽  
Vol 4 (1) ◽  
pp. 247-250
Author(s):  
Armin Müller ◽  
Ekaterina Kovacheva ◽  
Steffen Schuler ◽  
Olaf Dössel ◽  
Lukas Baron
Keyword(s):  
Human Heart ◽  
Maximum Pressure ◽  
Simulation Framework ◽  
Activation Time ◽  
Tension Development ◽  
Human Cardiomyocytes ◽  
Local Activation ◽  
Activation Times ◽  
The Right ◽  
Simulation Time

AbstractThe human heart is an organ of high complexity and hence, very challenging to simulate. To calculate the force developed by the human heart and therefore the tension of the muscle fibers, accurate models are necessary. The force generated by the cardiac muscle has physiologically imposed limits and depends on various characteristics such as the length, strain and the contraction velocity of the cardiomyocytes. Another characteristic is the activation time of each cardiomyocyte, which is a wave and not a static value for all cardiomyocytes. To simulate a physiologically correct excitation, the functionality of the cardiac simulation framework CardioMechanics was extended to incorporate inhomogeneous activation times. The functionality was then used to evaluate the effects of local activation times with two different tension models. The active stress generated by the cardiomyocytes was calculated by (i) an explicit function and (ii) an ode-based model. The results of the simulations showed that the maximum pressure in the left ventricle dropped by 2.3% for the DoubleHill model and by 5.3% for the Lumens model. In the right ventricle the simulations showed similar results. The maximum pressure in both the left and the right atrium increased using both models. Given that the simulation of the inhomogeneously activated cardiomyocytes increases the simulation time when used with the more precise Lumens model, the small drop in maximum pressure seems to be negligible in favor of a simpler simulation model

scholarly journals Effects of local activation times on the tension development of human cardiomyocytes in a computational model

2018 ◽  
Vol 4 (1) ◽  
pp. 101-104
Author(s):  
Armin Müller ◽  
Ekaterina Kovacheva ◽  
Steffen Schuler ◽  
Olaf Dössel ◽  
Lukas Baron
Keyword(s):  
Human Heart ◽  
Maximum Pressure ◽  
Simulation Framework ◽  
Activation Time ◽  
Tension Development ◽  
Human Cardiomyocytes ◽  
Local Activation ◽  
Activation Times ◽  
The Right ◽  
Simulation Time

AbstractThe human heart is an organ of high complexity and hence, very challenging to simulate. To calculate the force developed by the human heart and therefore the tension of the muscle fibers, accurate models are necessary. The force generated by the cardiac muscle has physiologically imposed limits and depends on various characteristics such as the length, strain and the contraction velocity of the cardiomyocytes. Another characteristic is the activation time of each cardiomyocyte, which is a wave and not a static value for all cardiomyocytes. To simulate a physiologically correct excitation, the functionality of the cardiac simulation framework CardioMechanics was extended to incorporate inhomogeneous activation times. The functionality was then used to evaluate the effects of local activation times with two different tension models. The active stress generated by the cardiomyocytes was calculated by (i) an explicit function and (ii) an ode-based model. The results of the simulations showed that the maximum pressure in the left ventricle dropped by 2.3% for the DoubleHill model and by 5.3% for the Lumens model. In the right ventricle the simulations showed similar results. The maximum pressure in both the left and the right atrium increased using both models. Given that the simulation of the inhomogeneously activated cardiomyocytes increases the simulation time when used with the more precise Lumens model, the small drop in maximum pressure seems to be negligible in favor of a simpler simulation model.

Abstract 18650: Activation Mapping of Ventricular Ectopy: Characterization of a Threshold Value Predicting Successful Catheter Ablation

Circulation ◽  
2015 ◽  
Vol 132 (suppl_3) ◽  
Author(s):  
Will Camnitz ◽  
Kenneth Bilchick ◽  
John Dimarco ◽  
Kevin Driver ◽  
John Ferguson ◽  
...  
Keyword(s):  
Catheter Ablation ◽  
Threshold Value ◽  
Accurate Method ◽  
Ventricular Ectopy ◽  
Activation Time ◽  
Local Activation ◽  
Successful Ablation ◽  
Activation Times ◽  
Local Activation Time ◽  
Activation Mapping

Background: Catheter ablation of ventricular ectopy is performed with increasing frequency. Activation mapping to determine the site with the earliest presystolic electrogram (EGM) is the most accurate method to locate the optimal ablation site. Despite this, activation mapping of ventricular ectopy has not been systematically reviewed in a large series, and the optimal activation time predicting successful ablation has not previously been determined. The goal of this study is to determine the local presystolic activation time most predictive of successful ablation. Methods and Results: We retrospectively reviewed 100 consecutive successful endocardial PVC ablations and analyzed the local activation time at each successful and unsuccessful ablation site. A total of 561 ablation lesions were reviewed. Activation time was calculated as the difference between the peak of the local bipolar EGM and the onset of the reference surface QRS complex. Acute success was defined as complete elimination of the target PVC during the procedure with no recurrence at 30 days by ECG and follow-up Holter. A local activation time 27 msec presystolic best predicted success with a sensitivity of 88%, specificity 85%, and an area under the ROC curve of 0.936 (95% CI 0.91 - 0.95; figure 1). The 27 msec presystolic activation time remained most predictive of success after sub-stratifying activation times by location (RVOT v LVOT, outflow v intracavitary). The odds ratio for success with each 1 msec increase in activation time (becomes more negative by 1 msec) is 1.24 (95% CI 1.19 - 1.29). Conclusion: In our experience, a local presystolic activation time of 27 msec is the threshold value most predictive of successful PVC ablation. Our review is the first to systematically characterize an activation time predicting success with PVC ablation in a large cohort. Figure 1

Surface Activation of Guinea Pig Ventricle Determined by Intracellular Electrodes

1958 ◽  
Vol 195 (2) ◽  
pp. 396-402 ◽  
Author(s):  
Gordon E. Dower ◽  
John A. Osborne
Keyword(s):  
Guinea Pig ◽  
General Pattern ◽  
Activation Process ◽  
Activation Time ◽  
Different Types ◽  
Relative Activation ◽  
Myocardial Fibers ◽  
The Times ◽  
Activation Times ◽  
The Right

Intracellular micro-electrodes have been used to detect the arrival of the activation process in myocardial fibers lying near the epicardial surface of the intact guinea pig ventricle. Arrival of excitation was indicated by the steepest part of the upstroke of the transmembrane action-potential curve obtained. The times of arrival of the activation process at various points on the surface of the ventricles were measured with respect to selected points on the simultaneous ECG, which served as a standard of reference. The scale on the time axis was greatly magnified (paper speed = 75 cm/sec.) in order to determine these times with precision. The ‘relative activation times’ thus obtained indicated that the right ventricle tended to be activated earlier than the left, except on their dorsal aspects, where there was little difference. There were, however, many exceptions to this general pattern, and rather large differences in relative activation times were frequently observed between contiguous regions. The high paper speeds used revealed three different types of upstroke in the monophasic records. An association was observed between the relative activation time of a region and the type of upstroke. An explanation of these findings is offered and a supporting experiment described.

P984Proof of endo-epicardial asynchrony of the left atrial wall in humans

EP Europace ◽  
2020 ◽  
Vol 22 (Supplement_1) ◽  
Author(s):  
R Kharbanda ◽  
C Kik ◽  
P Knops ◽  
A J J C Bogers ◽  
N M S De Groot
Keyword(s):  
Left Atrium ◽  
Conduction Block ◽  
Conduction Delay ◽  
Maximal Degree ◽  
Electrode Arrays ◽  
Epicardial Mapping ◽  
Activation Time ◽  
Opposite Electrode ◽  
Activation Times ◽  
The Right

Abstract Funding Acknowledgements Prof. Dr. NMS de Groot is supported by funding grants from CVON-AFFIP (914728), NWO-Vidi (91717339), Biosense Webster USA (ICD 783454) and Medical Del Introduction Treatment of atrial fibrillation (AF) is still suboptimal as mechanisms underlying AF initiation and persistence are incompletely understood. Endo-Epicardial asynchrony (EEA) plays an important role in AF persistence and has so far only been demonstrated in the right atrium (RA). Purpose To investigate whether EEA also exists in the thin walled left atrium (LA) and to measure the maximal degree of EEA between the endo- and epicardial layers during sinus rhythm (SR). Methods Simultaneous endo-epicardial mapping of the LA was performed during SR in 3 male patients (73 ± 1.5 years) with history of paroxysmal AF undergoing cardiac surgery including rhythm surgery and LA appendage amputation. Simultaneous endo-epicardial mapping was performed with a mapping clamp containing two electrode arrays of 8x16 electrodes (diameters: 0.4mm, interelectrode distance: 2mm) positioned exactly opposite to each other. The mapping clamp was introduced through the LA appendage with its tip towards the superior pulmonary vein. Local endo-epicardial activation time differences were determined by selecting the median time delay within the exact opposite electrode and its 8 surrounding electrodes. The asynchrony map consisted of the maximum of 2 medians from direct opposite electrodes. EEA was defined as time differences ≥15ms. Conduction delay (CD) and conduction block (CB) were defined as differences in local activation times between neighboring electrodes of respectively ≥7 and ≥12ms. Results A total of 35 SR beats were analyzed. Mean total activation time of the whole endo-epicardial LA tissue was 42.4 ± 9.5ms and did not differ between both layers (epicardium: 31.2 ± 9.9ms; endocardium: 37.8 ± 10.3ms; P= 0.62). CD and CB were observed in respectively 3.2% and 6.3% at the epicardium and 3.3% and 3.0% at the endocardium. The lowest amount of CD (5.2%) and CB (0.3%) was observed in the patient who had his first AF episode only 11 days prior to surgery. Also, no EEA was present in this patient. In two patients with paroxysmal AF >6 months, the prevalence of EEA was respectively 2.7% and 41.4% and the degree of EEA ranged from 15 to 44ms. Interestingly, the patient with the highest degree of EEA was diagnosed with paroxysmal AF for almost 5 years (Figure 1). Conclusion Our data provides evidence for the existence of EEA in the human left atrium which appears to be already present during SR. Knowledge of EEA and the ability to stage AF based on the degree of EEA is essential for individualized and staged future therapy for AF. Abstract Figure 1. The maximal degree of endo-epi

scholarly journals Polarity reversal lowers activation time during diastolic field stimulation of the rabbit ventricles: insights into mechanisms

2008 ◽  
Vol 295 (4) ◽  
pp. H1626-H1633 ◽  
Author(s):  
M. M. Maleckar ◽  
M. C. Woods ◽  
V. Y. Sidorov ◽  
M. R. Holcomb ◽  
D. N. Mashburn ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Left Ventricular ◽  
Uniform Field ◽  
Activation Time ◽  
Activation Patterns ◽  
Reversed Polarity ◽  
3D Volume ◽  
Activation Times ◽  
The Right ◽  
Activation Delay

To fully characterize the mechanisms of defibrillation, it is necessary to understand the response, within the three-dimensional (3D) volume of the ventricles, to shocks given in diastole. Studies that have examined diastolic responses conducted measurements on the epicardium or on a transmural surface of the left ventricular (LV) wall only. The goal of this study was to use optical imaging experiments and 3D bidomain simulations, including a model of optical mapping, to ascertain the shock-induced virtual electrode and activation patterns throughout the rabbit ventricles following diastolic shocks. We tested the hypothesis that the locations of shock-induced regions of hyperpolarization govern the different diastolic activation patterns for shocks of reversed polarity. In model and experiment, uniform-field monophasic shocks of reversed polarities (cathode over the right ventricle is RV−, reverse polarity is LV−) were applied to the ventricles in diastole. Experiments and simulations revealed that RV− shocks resulted in longer activation times compared with LV− shocks of the same strength. 3D simulations demonstrated that RV− shocks induced a greater volume of hyperpolarization at shock end compared with LV− shocks; most of these hyperpolarized regions were located in the LV. The results of this study indicate that ventricular geometry plays an important role in both the location and size of the shock-induced virtual anodes that determine activation delay during the shock and subsequently affect shock-induced propagation. If regions of hyperpolarization that develop during the shock are sufficiently large, activation delay may persist until shock end.

scholarly journals Comparing Ventricular Synchrony in Left Bundle Branch and Left Ventricular Septal Pacing in Pacemaker Patients

2021 ◽  
Vol 10 (4) ◽  
pp. 822
Author(s):  
Luuk I.B. Heckman ◽  
Justin G.L.M. Luermans ◽  
Karol Curila ◽  
Antonius M.W. Van Stipdonk ◽  
Sjoerd Westra ◽  
...  
Keyword(s):  
Left Ventricular ◽  
Activation Time ◽  
Ventricular Synchrony ◽  
Septal Pacing ◽  
Ventricular Activation ◽  
Qrs Morphology ◽  
Conversion Matrix ◽  
Qrs Duration ◽  
The Right ◽  
Electrophysiological Effects

Background: Left bundle branch area pacing (LBBAP) has recently been introduced as a novel physiological pacing strategy. Within LBBAP, distinction is made between left bundle branch pacing (LBBP) and left ventricular septal pacing (LVSP, no left bundle capture). Objective: To investigate acute electrophysiological effects of LBBP and LVSP as compared to intrinsic ventricular conduction. Methods: Fifty patients with normal cardiac function and pacemaker indication for bradycardia underwent LBBAP. Electrocardiography (ECG) characteristics were evaluated during pacing at various depths within the septum: starting at the right ventricular (RV) side of the septum: the last position with QS morphology, the first position with r’ morphology, LVSP and—in patients where left bundle branch (LBB) capture was achieved—LBBP. From the ECG’s QRS duration and QRS morphology in lead V1, the stimulus- left ventricular activation time left ventricular activation time (LVAT) interval were measured. After conversion of the ECG into vectorcardiogram (VCG) (Kors conversion matrix), QRS area and QRS vector in transverse plane (Azimuth) were determined. Results: QRS area significantly decreased from 82 ± 29 µVs during RV septal pacing (RVSP) to 46 ± 12 µVs during LVSP. In the subgroup where LBB capture was achieved (n = 31), QRS area significantly decreased from 46 ± 17 µVs during LVSP to 38 ± 15 µVs during LBBP, while LVAT was not significantly different between LVSP and LBBP. In patients with normal ventricular activation and narrow QRS, QRS area during LBBP was not significantly different from that during intrinsic activation (37 ± 16 vs. 35 ± 19 µVs, respectively). The Azimuth significantly changed from RVSP (−46 ± 33°) to LVSP (19 ± 16°) and LBBP (−22 ± 14°). The Azimuth during both LVSP and LBBP were not significantly different from normal ventricular activation. QRS area and LVAT correlated moderately (Spearman’s R = 0.58). Conclusions: ECG and VCG indices demonstrate that both LVSP and LBBP improve ventricular dyssynchrony considerably as compared to RVSP, to values close to normal ventricular activation. LBBP seems to result in a small, but significant, improvement in ventricular synchrony as compared to LVSP.

scholarly journals STUDIES WITH THE ELECTROCARDIOGRAPH ON THE ACTION OF THE VAGUS NERVE ON THE HUMAN HEART

1911 ◽  
Vol 14 (3) ◽  
pp. 217-234 ◽  
Author(s):  
G. Canby Robinson ◽  
George Draper
Keyword(s):  
Vagus Nerve ◽  
Mechanical Stimulation ◽  
Human Heart ◽  
Appreciable Effect ◽  
Vagus Stimulation ◽  
Ventricular Systole ◽  
Constant Change ◽  
The Right ◽  
Stimulation Of

In hearts showing auricular fibrillation mechanical stimulation of the right vagus nerve causes, as a rule, marked slowing or stoppage of ventricular rhythm, without producing any appreciable effect in the electrocardiographic record of the auricular fibrillation. The ventricular pauses are apparently due to the blocking of stimuli from the auricles. The force of ventricular systole is distinctly weakened for several beats after vagus stimulation, and ectopic ventricular systoles have been seen in several instances, apparently the result of the vagus action. There may, in some cases, be lowered excitability of the ventricles, while no constant change is seen in the size of the electrical complexes representing ventricular systole.

scholarly journals 1224A hybrid local activation time mapping model as for the ablation of premature ventricular contractions

EP Europace ◽  
2017 ◽  
Vol 19 (suppl_3) ◽  
pp. iii254-iii255
Author(s):  
T J R De Potter ◽  
E. Silva Garcia ◽  
T. Strisciuglio ◽  
T. Bar-On ◽  
S. Chatzikyriakou ◽  
...  
Keyword(s):  
Activation Time ◽  
Premature Ventricular Contractions ◽  
Mapping Model ◽  
Local Activation ◽  
Local Activation Time

Abstract 635: The Proximal AV Bundle in the Human Heart and Related Morbidity

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Darlene K Racker
Keyword(s):  
Human Heart ◽  
Lucifer Yellow ◽  
Ventricular Outflow Tract ◽  
Left Ventricular ◽  
Canine Heart ◽  
Sa Node ◽  
Electrode Potentials ◽  
The Right ◽  
Av Bundle

INTRODUCTION: The proximal AV bundle (PAVB) has been shown to be the only input to the AV node (AVN) in the canine heart in anatomoelectrical reports over the past 20 years. The anatomic studies utilized photographic correlations of epi- and endocardial aspects of whole hearts through blocking, and serial histologic parallel, perpendicular and transverse plane Goldner Trichrome stained sections of the flattened heart; Karnovsky’s fixative at pH 7.2 and sucrose buffer rinses; direct 3D and stereotaxic analysis. Electrical studies, under direct observation of in-vitro superfused hearts, delineated unique wire, catheter, and micropipet electrode potentials via high K, transections, Lucifer Yellow iontophoresis and photoablations during spontaneous and paced SA node rhythms and with simultaneous SA node, atrionodal bundles, PAVB, AVN and distal AV bundle recordings. HYPOTHESIS: The PAVB exists in the human heart. METHODS AND RESULTS: Explanted normal human hearts, deemed unsuitable for transplantation, processed as above with transverse sections, revealed that the AVN (Figs. A–C ) is joined by the PAVB at a 90-degree angle (Figs. B, C ). These “normal” hearts from older patients (57– 80 yr) had atrophic or absent atrial myocardium. In Figure C , most of the right medial atrial wall myocardium, but not the left atrium (LA), had been replaced by fat. CONCLUSIONS: PAVB is the only AVN input in the human heart. As in the canine heart, PAVB also runs away from the annulus and is apposed to LA. Knowledge of the PAVB should be helpful in decreasing morbidity associated with clinical procedures. Care must be taken in ablating the fast superior atrionodal bundle pathway input to the PAVB. Figures A and B are from the same 60 yr and C is from a 71 yr old heart. AVN (A) is apposed to the left ventricular outflow tract (LVOFT and dotted line) along with the PAVB ( B and C ). But as seen in C , PAVB assumes a position apposed to LA, And, as in the dog heart, thereafter (not shown here) PAVB is completely apposed to LA.

scholarly journals Bachmann bundle impairment following linear ablation of left anterior wall: impact on left atrial function

2020 ◽  
Author(s):  
Yanjuan Zhang ◽  
Fengming Wu ◽  
Yu Gao ◽  
Nan Wu ◽  
Gang Yang ◽  
...  
Keyword(s):  
Contractile Function ◽  
Anterior Wall ◽  
Activation Time ◽  
Linear Ablation ◽  
Measured Activation ◽  
Mechanical Remodeling ◽  
Activation Times ◽  
And Function ◽  
Bachmann Bundle

Background: We aimed to evaluate the effect of Bachmann bundle (BB) impairment on electrical and mechanical function of the left atrium (LA), as well as the long-term clinical impact of such impairment. Design: We measured activation time in the five LA walls in 56 patients with atrial fibrillation. LA reservoir, conduit, and contractile function were also evaluated. Patients were divided into two groups based on ablation strategy: the circumferential pulmonary vein isolation (CPVI) group and CPVI with anterior wall linear ablation (LAWA) group. Patients in the CPVI+LAWA group were divided into two sub-groups based on ECG differences following ablation: the BB impairment group and intact BB group. LA activation time and function were then compared between the ablation strategy groups and the CPVI+LAWA subgroups. Results: Patients in the CPVI+LAWA group exhibited longer activation times in the anterior and lateral walls of the LA, poorer LA synchrony, and reduced LA contractile and reservoir function when compared with those in the CPVI group. In the BB impairment subgroup, we observed a discrepancy between electrical/mechanical remodeling. Among five walls, activation time was longest in this region. BB impairment was also associated with reduced LA function. Conclusion: Significant changes in LA function and conductibility were observed in patients with anterior wall ablation, especially those with iatrogenic BB impairment.

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