Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama.
Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama.
Heart Rhythm. 2021 Jun;18(6):995-1003. doi: 10.1016/j.hrthm.2021.01.022. Epub 2021 Jan 26.
Shocks near defibrillation threshold (nDFT) strength commonly extinguish all ventricular fibrillation (VF) wavefronts, but a train of rapid, well-organized postshock activations (PAs) typically appears before sinus rhythm ensues. If one of the PA waves undergoes partial propagation block (wavebreak), reentry may be induced, causing VF to reinitiate and the shock to fail.
The purpose of this study was to determine whether wavebreak leading to VF reinititation following nDFT shocks occurs preferentially at the right ventricular insertion (RVI), which previous studies have identified as a key site for wavebreak.
We used panoramic optical mapping to image the ventricular epicardium of 6 isolated swine hearts during nDFT defibrillation episodes. After each experiment, the hearts were fixed and their geometry scanned with magnetic resonance imaging (MRI). The MRI and mapping datasets were spatially coregistered. For failed shocks, we identified the site of the first wavebreak of a PA wave during VF reinitiation.
We recorded 59 nDFT failures. In 31 of these, the first wavebreak event occurred within 1 cm of the RVI centerline, most commonly on the anterior side of the right ventricular insertion (aRVI) (23/31). The aRVI region occupies 16.8% ± 2.5% of the epicardial surface and would be expected to account for only 10 wavebreaks if they were uniformly distributed. By χ analysis, aRVI wavebreaks were significantly overrepresented.
The anterior RVI is a key site in promoting nDFT failure. Targeting this site to prevent wavebreak could convert defibrillation failure to success and improve defibrillation efficacy.
接近除颤阈值（nDFT）强度的电击常会消除所有室颤（VF）波前，但电击后常会出现一连串快速、组织有序的后去极化激活（PA）。如果 PA 中的一个波前发生部分传导阻滞（波断裂），可能会引发折返，导致 VF 再次发生，电击失败。
本研究旨在确定 nDFT 电击后导致 VF 再次发生的波断裂是否更易发生在右心室插入部位（RVI），先前的研究已确定该部位是波断裂的关键部位。
我们使用全景光学标测在 6 个离体猪心的心室心外膜上进行 nDFT 除颤试验。每次实验后，将心脏固定并使用磁共振成像（MRI）扫描其几何形状。将 MRI 和标测数据集进行空间配准。对于失败的电击，我们确定在 VF 再次发生时 PA 中第一个波断裂的部位。
我们记录了 59 次 nDFT 失败。在其中的 31 次失败中，首次波断裂事件发生在 RVI 中心线的 1cm 内，最常见于右心室插入的前侧（aRVI）（23/31）。aRVI 区域占据心外膜表面的 16.8%±2.5%，如果均匀分布，预计只会发生 10 次波断裂。通过卡方检验，aRVI 波断裂明显过多。
前 RVI 是促进 nDFT 失败的关键部位。针对该部位以防止波断裂可能会使除颤失败转化为成功，并提高除颤效果。
