Department of Applied Science, College of William and Mary, Williamsburg, Virginia, USA.
Heart Rhythm. 2013 May;10(5):740-8. doi: 10.1016/j.hrthm.2013.01.016. Epub 2013 Jan 23.
We recently demonstrated that high frequency alternating current (HFAC) electric fields can reversibly block propagation in the heart by inducing an oscillating, elevated transmembrane potential (Vm) that maintains myocytes in a refractory state for the field duration and can terminate arrhythmias, including ventricular fibrillation (VF).
To quantify and characterize conduction block (CB) induced by HFAC fields and to determine whether the degree of CB can be used to predict defibrillation success.
Optical mapping was performed in adult guinea pig hearts (n = 14), and simulations were performed in an anatomically accurate rabbit ventricular model. HFAC fields (50-500 Hz) were applied to the ventricles. A novel power spectrum metric of CB-the loss of spectral power in the 1-30 Hz range, termed loss of conduction power (LCP)-was assessed during the HFAC field and compared with defibrillation success and VF vulnerability.
LCP increased with field strength and decreased with frequency. Optical mapping experiments conducted on the epicardial surface showed that LCP and the size of CB regions were significantly correlated with VF initiation and termination. In simulations, subsurface myocardial LCP and CB sizes were more closely correlated with VF termination than surface values. Multilinear regression analysis of simulation results revealed that while CB on both the surface and the subsurface myocardium was predictive, subsurface myocardial CB was the better predictor of defibrillation success.
HFAC fields induce a field-dependent state of CB, and defibrillation success is related to the degree and location of the CB.
我们最近证明，高频交流（HFAC）电场可以通过诱导振荡、升高的跨膜电位（Vm）来可逆地阻断心脏中的传播，从而使心肌细胞在电场持续时间内处于不应期，并终止心律失常，包括心室颤动（VF）。
量化和描述 HFAC 场诱导的传导阻滞（CB），并确定 CB 的程度是否可用于预测除颤成功。
在成年豚鼠心脏（n = 14）中进行光学映射，并在解剖准确的兔心室模型中进行模拟。将 HFAC 场（50-500 Hz）施加到心室。评估了一种新的 CB 功率谱度量-称为传导功率损失（LCP）的 1-30 Hz 范围内的光谱功率损失-在 HFAC 场期间，并与除颤成功和 VF 易感性进行了比较。
LCP 随场强增加而增加，随频率降低而降低。在心脏表面进行的光学映射实验表明，LCP 和 CB 区域的大小与 VF 的起始和终止显著相关。在模拟中，与表面值相比，亚表面心肌 LCP 和 CB 大小与 VF 终止的相关性更强。模拟结果的多元线性回归分析表明，虽然表面和亚表面心肌的 CB 均具有预测性，但亚表面心肌的 CB 是除颤成功的更好预测因子。
HFAC 场诱导出一种与场相关的 CB 状态，除颤成功与 CB 的程度和位置有关。
