Bursac Nenad, Tung Leslie
Department of Biomedical Engineering, Duke University, 3000 Science Drive, Durham, NC 27708, USA.
Cardiovasc Res. 2006 Feb 1;69(2):381-90. doi: 10.1016/j.cardiores.2005.09.014. Epub 2005 Nov 7.
Attempts to cardiovert tachycardia by rapid point pacing can sometimes result in transient or stable increase of the heart rate (acceleration), changed ECG morphology, and/or fibrillation. The goal of this study was to investigate the effect of rapid pacing on the dynamics of functional reentry in monolayer cultures of cardiac cells.
Fully confluent, uniformly anisotropic monolayers of neonatal rat ventricular myocytes were prepared using methods of microabrasion. Cells were paced by a point electrode at rest and during functional reentry, and membrane voltages were optically mapped.
Point pacing readily induced single loop anisotropic functional reentry with monomorphic optical pseudo-ECG (pECG) and average rotation period of 193+/-52 ms (n=71 monolayers). Attempts to cardiovert reentry by rapid pacing at rates 10-50% faster than the reentry rate were successful in 57/71 monolayers. In 14/71 monolayers, the number of rotating waves was stably increased by 1 to 4, yielding a 10-70% acceleration of pECG rate and change to a different monomorphic or polymorphic pECG. The resulting multi-wave functional reentries were classified based on the number and direction of their rotating waves. The higher the number of waves in the multi-wave reentry, the more accelerated was the rate of cell firing in the monolayer. Importantly, stable acceleration was only inducible in monolayers with relatively deep and broad conduction velocity restitution relationships. Reapplication of point pacing further accelerated, decelerated, or eventually terminated the reentrant activity.
These results suggest that stable multiplication of rotating waves in conjunction with a deep and broad conduction velocity restitution relationship is a possible mechanism for stable acceleration of functional reentry by rapid pacing.
通过快速点刺激来复律心动过速有时会导致心率短暂或稳定升高（加速）、心电图形态改变和/或颤动。本研究的目的是探讨快速刺激对心肌细胞单层培养物中功能性折返动力学的影响。
采用微磨损方法制备完全汇合、各向异性均匀的新生大鼠心室肌细胞单层。在静息状态和功能性折返期间，用点电极刺激细胞，并对膜电压进行光学标测。
点刺激很容易诱发单环各向异性功能性折返，伴有单形性光学伪心电图（pECG），平均旋转周期为193±52毫秒（n=71个单层）。以比折返率快10%-50%的速率进行快速刺激来复律折返，在71个单层中有57个成功。在71个单层中的14个中，旋转波的数量稳定增加1至4个，导致pECG速率加速10%-70%，并转变为不同的单形性或多形性pECG。根据其旋转波的数量和方向对产生的多波功能性折返进行分类。多波折返中的波数越高，单层中细胞放电的速率就越快。重要的是，稳定加速仅在具有相对深且宽的传导速度恢复关系的单层中可诱导。再次应用点刺激可进一步加速、减慢或最终终止折返活动。
这些结果表明，旋转波的稳定增殖以及深且宽的传导速度恢复关系是通过快速刺激使功能性折返稳定加速的一种可能机制。
