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Spiral Wave Breakup in Excitable Media Induced by Inhomogeneity of Anisotropic Conduction
S8
Abstracts
Heart, Lung and Circulation 2008;17S:S1–S209
ABSTRACTS
(DY ). Both coefficients were functions of position: DX (x, y) = 2(1 − |x|/L) and DY (x, y) = 2(1 − |y|/L) where L is the sample length. In such system, spiral wave was initiated and trajectory of the wave tip recorded. Results: Spiral wave initiated in the sample was attracted to its geometrical centre. The attraction strength was assessed by application of resonant forcing with a varying amplitude and frequency equal to that of spiral wave. The spiral wave drifted until attraction force and resonant forcing balanced each other. Attraction force was linearly dependent on distance from centre of the sample. Conclusions: Specific spatial distribution of the level of the anisotropic conduction may act as trap for spiral waves binding them with a force dependent on distance from the trap. Such areas in structurally remodelled heart may be responsible for anchoring of the reentry, hence becoming potentially important targets for ablation. doi:10.1016/j.hlc.2008.05.013 13 Spiral Wave Breakup in Excitable Media Induced by Inhomogeneity of Anisotropic Conduction Pawel Kuklik 1,∗ , Jan Jacek Zebrowski 1 , Szumowski 2 , Prashanthan Sanders 3
Lukasz
1 Faculty
of Physics, Warsaw University of Technology, Warsaw, Poland; 2 Institute of Cardiology, Warsaw, Poland; 3 Cardiovascular Research Center, Department of Cardiology, Royal Adelaide Hospital, and the Disciplines of Medicine and Physiology, University of Adelaide, Adelaide, Australia Background: Many conditions can result in remodelling of heart muscle and perturbation of local orientation of muscle fibres. Influence of this perturbation on the stability of the spiral wave was not investigated. Methods: The FitzHugh–Nagumo model of an excitable medium was used to model the conduction of activation waves in a two-dimensional, rectangular area with fully anisotropic conduction as initial condition. Inhomogeneity of the anisotropy level was modelled by adding Gaussian noise to diffusion coefficients keeping the absolute value constant. Next, spiral wave was initiated. Number of distinct wavelets found after time equal to 50 rotations was used as a measure of arrythmogeneity level for the given case. For each value of standard deviation 20 iterations were conducted and results averaged. Results: A low magnitude of the anisotropy noise resulted in termination of the spiral wave: the wave was unable to rotate due to the high anisotropy level. A large magnitude of the anisotropy noise caused stable propagation: the system was effectively homogeneous. For intermediate noise intensity, the initial wave broke up into several independent spiral waves or waves circulating around conduction obstacles. At an optimal noise intensity (σ = 0.07) the number of wavelets (10.8 ± 2.1) was maximized. Conclusions: Local perturbation of fibre orientation promotes spiral wave breakup. There is an optimal perturbation level, which maximizes the number of distinct wavelets in system. This mechanism of spiral wave
breakup may be one of the causes of arrythmogeneity of electrically remodelled heart muscle. doi:10.1016/j.hlc.2008.05.014 14 Restoration of Sinus Rhythm by Cardioversion is Associated With Increased Arterial Stiffness: Implications for Thrombogenesis Anisha Prabhu 1 , Christopher Wong 2 , Ross RobertsThomson 2 , Matthew Worthley 2 , Lorraine Mackenzie 1 , Dennis Lau 2 , Bobby John 2 , Martin Stiles 2 , Anthony Brooks 2 , Glenn Young 2 , Prashanthan Sanders 2 , Scott Willoughby 2,∗ 1 Discipline
of Physiology, University of Adelaide, Adelaide, South Australia, Australia; 2 Cardiovascular Research Centre, University of Adelaide, Adelaide, South Australia, Australia Introduction: Atrial fibrillation (AF) is the most common cardiac arrhythmia and is associated with an increased risk of stroke. While atrial mechanical dysfunction is postulated to be a mechanism leading to stroke there are likely other factors contributing to this pro-thrombotic state. Endothelial dysfunction and decreased arterial elasticity (arterial stiffness) are common in patients with coronary artery disease and are known predictors of cardiovascular mortality. Whether such endothelial dysfunction contributes to the heightened risk of stroke after cardioversion is not known. Methods: Fourteen consecutive patients (mean age 58 ± 11 years) with AF scheduled for elective cardioversion were enrolled in this study. Arterial stiffness was measured before and 2 h after cardioversion. Augmentation index (a measure of arterial stiffness) was derived from peripheral arterial tonometry measurements using a previously validated system (EndoPAT 2000). Results: All patients were successfully reverted to sinus rhythm under sedation. Compared to baseline values cardioversion was associated with a significant increased in arterial stiffness (p = 0.01; see Figure).
Conclusions: Cardioversion is associated with an acute increase in arterial stiffness. This data therefore suggests that arterial stiffness (a marker of endothelial dysfunction) may contribute to the pro-thrombotic state after cardioversion of AF. doi:10.1016/j.hlc.2008.05.015
Abstracts
Heart, Lung and Circulation 2008;17S:S1–S209
ABSTRACTS
(DY ). Both coefficients were functions of position: DX (x, y) = 2(1 − |x|/L) and DY (x, y) = 2(1 − |y|/L) where L is the sample length. In such system, spiral wave was initiated and trajectory of the wave tip recorded. Results: Spiral wave initiated in the sample was attracted to its geometrical centre. The attraction strength was assessed by application of resonant forcing with a varying amplitude and frequency equal to that of spiral wave. The spiral wave drifted until attraction force and resonant forcing balanced each other. Attraction force was linearly dependent on distance from centre of the sample. Conclusions: Specific spatial distribution of the level of the anisotropic conduction may act as trap for spiral waves binding them with a force dependent on distance from the trap. Such areas in structurally remodelled heart may be responsible for anchoring of the reentry, hence becoming potentially important targets for ablation. doi:10.1016/j.hlc.2008.05.013 13 Spiral Wave Breakup in Excitable Media Induced by Inhomogeneity of Anisotropic Conduction Pawel Kuklik 1,∗ , Jan Jacek Zebrowski 1 , Szumowski 2 , Prashanthan Sanders 3
Lukasz
1 Faculty
of Physics, Warsaw University of Technology, Warsaw, Poland; 2 Institute of Cardiology, Warsaw, Poland; 3 Cardiovascular Research Center, Department of Cardiology, Royal Adelaide Hospital, and the Disciplines of Medicine and Physiology, University of Adelaide, Adelaide, Australia Background: Many conditions can result in remodelling of heart muscle and perturbation of local orientation of muscle fibres. Influence of this perturbation on the stability of the spiral wave was not investigated. Methods: The FitzHugh–Nagumo model of an excitable medium was used to model the conduction of activation waves in a two-dimensional, rectangular area with fully anisotropic conduction as initial condition. Inhomogeneity of the anisotropy level was modelled by adding Gaussian noise to diffusion coefficients keeping the absolute value constant. Next, spiral wave was initiated. Number of distinct wavelets found after time equal to 50 rotations was used as a measure of arrythmogeneity level for the given case. For each value of standard deviation 20 iterations were conducted and results averaged. Results: A low magnitude of the anisotropy noise resulted in termination of the spiral wave: the wave was unable to rotate due to the high anisotropy level. A large magnitude of the anisotropy noise caused stable propagation: the system was effectively homogeneous. For intermediate noise intensity, the initial wave broke up into several independent spiral waves or waves circulating around conduction obstacles. At an optimal noise intensity (σ = 0.07) the number of wavelets (10.8 ± 2.1) was maximized. Conclusions: Local perturbation of fibre orientation promotes spiral wave breakup. There is an optimal perturbation level, which maximizes the number of distinct wavelets in system. This mechanism of spiral wave
breakup may be one of the causes of arrythmogeneity of electrically remodelled heart muscle. doi:10.1016/j.hlc.2008.05.014 14 Restoration of Sinus Rhythm by Cardioversion is Associated With Increased Arterial Stiffness: Implications for Thrombogenesis Anisha Prabhu 1 , Christopher Wong 2 , Ross RobertsThomson 2 , Matthew Worthley 2 , Lorraine Mackenzie 1 , Dennis Lau 2 , Bobby John 2 , Martin Stiles 2 , Anthony Brooks 2 , Glenn Young 2 , Prashanthan Sanders 2 , Scott Willoughby 2,∗ 1 Discipline
of Physiology, University of Adelaide, Adelaide, South Australia, Australia; 2 Cardiovascular Research Centre, University of Adelaide, Adelaide, South Australia, Australia Introduction: Atrial fibrillation (AF) is the most common cardiac arrhythmia and is associated with an increased risk of stroke. While atrial mechanical dysfunction is postulated to be a mechanism leading to stroke there are likely other factors contributing to this pro-thrombotic state. Endothelial dysfunction and decreased arterial elasticity (arterial stiffness) are common in patients with coronary artery disease and are known predictors of cardiovascular mortality. Whether such endothelial dysfunction contributes to the heightened risk of stroke after cardioversion is not known. Methods: Fourteen consecutive patients (mean age 58 ± 11 years) with AF scheduled for elective cardioversion were enrolled in this study. Arterial stiffness was measured before and 2 h after cardioversion. Augmentation index (a measure of arterial stiffness) was derived from peripheral arterial tonometry measurements using a previously validated system (EndoPAT 2000). Results: All patients were successfully reverted to sinus rhythm under sedation. Compared to baseline values cardioversion was associated with a significant increased in arterial stiffness (p = 0.01; see Figure).
Conclusions: Cardioversion is associated with an acute increase in arterial stiffness. This data therefore suggests that arterial stiffness (a marker of endothelial dysfunction) may contribute to the pro-thrombotic state after cardioversion of AF. doi:10.1016/j.hlc.2008.05.015