Galappaththige Suran K, Gray Richard A, Roth Bradley J
Department of Physics, Oakland University, Rochester, Michigan 48309, USA.
Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, Maryland 20993, USA.
Chaos. 2017 Sep;27(9):093920. doi: 10.1063/1.5000163.
Unipolar stimulation of cardiac tissue is often used in the design of cardiac pacemakers because of the low current required to depolarize the surrounding tissue at rest. However, the advantages of unipolar over bipolar stimulation are not obvious at shorter coupling intervals when the tissue near the pacing electrode is relatively refractory. Therefore, this paper analyzes bipolar stimulation of cardiac tissue. The strength-interval relationship for bipolar stimulation is calculated using the bidomain model and a recently developed parsimonious ionic current model. The strength-interval curves obtained using different electrode separations and arrangements (electrodes placed parallel to the fibers versus perpendicular to the fibers) indicate that bipolar stimulation results in more complex activation patterns compared to unipolar stimulation. An unusually low threshold stimulus current is observed when the electrodes are close to each other (a separation of 1 mm) because of break excitation. Unlike for unipolar stimulation, anode make excitation is not present during bipolar stimulation, and an abrupt switch from anode break to cathode make excitation can cause dramatic changes in threshold with very small changes in the interval. These results could impact the design of implantable pacemakers and defibrillators.
由于在静息状态下使周围组织去极化所需的电流较低，心脏组织的单极刺激常用于心脏起搏器的设计中。然而，当起搏电极附近的组织相对不应期较短时，单极刺激相对于双极刺激的优势并不明显。因此，本文分析了心脏组织的双极刺激。使用双域模型和最近开发的简约离子电流模型计算双极刺激的强度-间期关系。使用不同电极间距和排列方式（电极与纤维平行放置与垂直放置）获得的强度-间期曲线表明，与单极刺激相比，双极刺激会导致更复杂的激活模式。当电极彼此靠近（间距为1毫米）时，由于间断兴奋会观察到异常低的阈值刺激电流。与单极刺激不同，双极刺激期间不存在阳极接通兴奋，并且从阳极断开到阴极接通兴奋的突然转变会导致阈值随间期的非常小的变化而发生显著变化。这些结果可能会影响植入式起搏器和除颤器的设计。
