NONLINEAR DYNAMICS OF PROPAGATION IN ISOLATED HEART TISSUE

可能导致室性心动过速(VT)和室颤(VF) 来自于心肌的涡流状折返性兴奋。我们的将军 假设是，在结构正常的心脏中，这些心律失常是 三维(3-D)电涡旋波激活 心脏肌肉的频率很高。为了检验这一假设，我们将 结合使用高分辨率光学标测、心电图仪和 心电向量图，连同孤立的数学模型 哈特兔子。我们的研究将致力于确定 持续性单态折返性室速是静止(锚定)的结果 滚动波；多态VT是否是非静止滚动波的结果 波；以及VF是否是少数几个 不稳定的滚动波。为此，我们将首先描述 朗宁多夫灌流心脏的电活动 特定参数的变化，如温度、动作电位 持续时间(Ad)、传导速度(Cv)和基本周期长度，其可以 确定我们启动涡状折返式激励的能力。我们 然后，我将研究空间不均匀(即，梯度)在 时程和速度在涡状再入过程中的作用 以及在确定心律失常的类型(例如，单形性或 多态的VT；VF)可能发生的。此外，我们还将量化 脑室全心外膜表面螺旋波的动力学研究 要确定这样的动力学是否与 易激动的媒体。此外，我们将使用分析工具来研究学位 波在地球上传播的时空组织 心外膜表面t=窦性心律、室性心动过速、室性心动过速。 为了研究这些区域中波传播的三维方面 研究中，我们将记录三个正交心电导联，用于构建 同时获得光学图的三维心电向量环 整个脑室表面。最后，我们将使用一个3-D“立方体” 模型，以及完整的右室和左室模型 基于Fitzhugh-Nagumo动力学和现实磁场的心脏 心脏几何结构的共振成像数据，作为研究非线性的指南 我们准备中的涡旋波的动力学。我们将特别注意 心外膜表面表现、心电图及三维重建 一种或多种折返性活动的心电向量图环模式 更多的可在右或左心室建立的滚动波， 甚至在室间隔。此外，还将关注 卷曲细丝相对于心肌的形状和位置 墙。总体而言，这里提出的研究承诺的答案与 对于了解波在心脏中的传播很重要。 此外，实现我们的目标可能有助于提高我们识别 疾病心脏中危及生命的快速性心律失常的机制。

Ventricular tachycardia (VT) and ventricular fibrillation (VF) may result from vortex-like reentrant excitation of the myocardium. Our general hypothesis is that, in the structurally normal heart, these arrhythmias are the result of 3-dimensional (3-D) electrical scroll waves activating the heart muscle at very high frequencies. To test this hypothesis, we will combine the use of high-resolution optical mapping, electrocardiography and vectorcardiography, together with mathematical modelling of the isolated rabbit hart. Our studies will be directed toward determining whether sustained monomorphic reentrant VT is the result of a stationary (anchored) scroll wave; whether polymorphic VT is the result of a nonstationary scroll wave; and whether VF is the result of the coexistence of a small n umber of nonstationary scroll waves. To this aim we will first characterize the electrical activity of the Langendorff-perfused heart in response to changes in specific parameters, such as temperature, action potential duration (APD), conduction velocity (CV) and basic cycle length, which may determine our ability to initiate vortex-like reentrant excitation. We will then study the role of spatial nonuniformities (i.e., gradients) in APD and CV in the genesis and subsequent evolution of vortex-like reentry, as well as in determining the type of arrhythmias (e.g., monomorphic or polymorphic VT; VF) that may occur. in addition, we will quantify the dynamics of spiral waves on the entire epicardial surface of the ventricles to establish whether such dynamics are consistent with 3-D scroll waves in excitable media. Further, we will use analytical tools to study the degree of spatial and temporal organization of wave propagation on the epicardial surface during t=sinus rhythm, ventricular pacing, VT and VF. To investigate three-dimensional aspects of wave propagation in these studies we will record three orthogonal ECG leads for the construction of 3-D vectorcardiographic loops while simultaneously obtaining optical maps of the entire ventricular surface. Finally, we will use a 3-D "cube" model, as well as a model of the intact right and left ventricles of the heart based on FitzHugh-Nagumo kinetics, and on realistic Magnetic Resonance Imaging data of heart geometry, as guides to study the nonlinear dynamics of scroll waves in our preparations. Particular attention will be given to the epicardial surface manifestation, ECG and 3-D vectorcardiographic loop pattern of reentrant activity generated by one or more scroll waves which may be established at the right or left ventricles, or even at the ventricular septum. Attention will also be given to the shape and location of the scroll filament in relation to the myocardial wall. Overall, the studies proposed here promise answers that relate importantly to the understanding of wave propagation in the heart. Moreover, achieving our goals may help to improve our ability to identify the mechanisms of life-threatening tachyarrhythmias in the diseased heart.