Gaeta Stephen, Bahnson Tristram D, Henriquez Craig
Division of Cardiology, Duke University Medical Center, Durham, North Carolina; Inova Heart and Vascular Institute, Falls Church, Virginia.
Division of Cardiology, Duke University Medical Center, Durham, North Carolina.
Heart Rhythm. 2020 May;17(5 Pt A):777-785. doi: 10.1016/j.hrthm.2019.12.010. Epub 2019 Dec 13.
The amplitude of bipolar electrograms (EGMs) is directionally sensitive, decreasing when measured from electrode pairs oriented oblique to a propagating wavefront.
The purpose of this study was to use a computational model and clinical data to establish the mechanism and magnitude of directional sensitivity.
Simulated EGMs were created using a computational model with electrode pairs rotated relative to a passing wavefront. A clinical database of 18,740 EGMs with varying electrode separation and orientations was recorded from the left atrium of 10 patients with atrial fibrillation during pacing. For each EGM, the angle of incidence between the electrodes and the wavefront was measured using local conduction velocity (CV) mapping.
A theoretical model was derived describing the effect of the changing angle of incidence, electrode spacing, and CV on the local activation time difference between a pair of electrodes. Model predictions were validated using simulated and clinical EGMs. Bipolar amplitude measured by an electrode pair is decreased (directionally sensitive) at angles of incidence resulting in local activation time differences shorter than unipolar downstroke duration. Directional sensitivity increases with closer electrode spacing, faster CV, and longer unipolar EGM duration. For narrowly spaced electrode pairs (<5 mm), it is predicted at all orientations.
Directional sensitivity occurs because bipolar amplitude is reduced when the component unipolar EGMs overlap, such that neither electrode is "indifferent." At the electrode spacing of clinical catheters, this is predicted to occur regardless of catheter orientation. This suggests that bipolar directional sensitivity can be lessened but not overcome by recently introduced catheters with additional rotated electrode pairs.
双极电图（EGM）的幅度具有方向敏感性，当从与传播波阵面倾斜的电极对测量时会降低。
本研究的目的是使用计算模型和临床数据来确定方向敏感性的机制和程度。
使用一个计算模型创建模拟的EGM，其中电极对相对于通过的波阵面旋转。在10例房颤患者起搏期间，从左心房记录了一个包含18740个EGM的临床数据库，这些EGM具有不同的电极间距和方向。对于每个EGM，使用局部传导速度（CV）映射测量电极与波阵面之间的入射角。
推导了一个理论模型，描述入射角、电极间距和CV的变化对一对电极之间局部激活时间差的影响。使用模拟和临床EGM对模型预测进行了验证。当入射角导致局部激活时间差短于单极下降持续时间时，电极对测量的双极幅度会降低（具有方向敏感性）。方向敏感性随着电极间距减小、CV加快和单极EGM持续时间延长而增加。对于窄间距电极对（<5mm），在所有方向上都可预测到方向敏感性。
出现方向敏感性是因为当单极EGM分量重叠时双极幅度降低，使得两个电极都不是“中性的”。在临床导管的电极间距下，预计无论导管方向如何都会出现这种情况。这表明，最近推出的带有额外旋转电极对的导管可以减轻但不能克服双极方向敏感性。
