Department of Cardiology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China.
Chin Med J (Engl). 2012 Aug;125(15):2701-7.
Ibutilide has been commonly used for pharmacologic cardioversion of atrial fibrillation and flutter in clinical settings. The objective of this study was to investigate the effects of ibutilide on the defibrillation threshold (DFT), restitution properties, dispersion of refractoriness and activation patterns during ventricular fibrillation (VF).
Ibutilide was administrated intravenously in six open-chest beagles. Before and after the drug administration, 20-second episodes of VF were electrically induced and recorded with a 10×10 unipolar electrode plaque sutured on the lateral epicardium of the left ventricle. DFT and VF activation patterns, including type of epicardial activation maps, VF cycle length (VF-CL), conduction velocity, wavelength (WL) and reentry incidence, were measured. Restitution properties and dispersion of refractoriness were estimated from activation recovery intervals (ARI) during pacing.
Compared to baseline, ibutilide markedly decreased the DFT by 31% ((491 ± 14) V vs. (337 ± 59) V, P < 0.01). The drug significantly reduced the maximal slope of the restitution curve (1.34 ± 0.08 vs. 0.76 ± 0.06, P < 0.01) and its epicardial dispersion (0.36 ± 0.09 vs. 0.21 ± 0.06, coefficient of variation, P = 0.03). The dispersion of refractoriness was enhanced at the pacing cycle length of 300 ms to 160 ms by ibutilide. The drug significantly increased the VF-CL ((96 ± 19) ms vs. (112 ± 20) ms, P < 0.01) and the WL ((41 ± 9) mm vs. (52 ± 14) mm, P = 0.02) during VF, and reduced the reentry incidence by 25% (0.08 ± 0.02 vs. 0.06 ± 0.02, P < 0.01). In the epicardial activation maps, ibutilide significantly reduced the percentage of more complex activation maps during VF.
Intravenous ibutilide significantly decreased the DFT. It might be due to reduction of activation pattern complexity during VF.
伊布利特在临床环境中常用于房颤和房扑的药物复律。本研究的目的是研究伊布利特对室颤（VF）时除颤阈值（DFT）、复极 restitution 特性、不应期离散度和激活模式的影响。
6 只开胸比格犬静脉给予伊布利特。给药前后，用电极片（10×10 个单极电极片，缝合在左心室外侧心外膜）记录 20 秒的 VF 。测量 DFT 和 VF 激活模式，包括心外膜激活图的类型、VF 周长（VF-CL）、传导速度、波长（WL）和折返发生率。通过起搏时的激活恢复间期（ARI）来估计 restitution 特性和不应期离散度。
与基线相比，伊布利特显著降低了 31%的 DFT（（491±14）V 比（337±59）V，P<0.01）。药物显著降低了 restitution 曲线的最大斜率（1.34±0.08 比 0.76±0.06，P<0.01）及其心外膜离散度（0.36±0.09 比 0.21±0.06，变异系数，P=0.03）。伊布利特增加了 300 到 160ms 起搏周长时的不应期离散度。药物显著增加了 VF 时的 VF-CL（（96±19）ms 比（112±20）ms，P<0.01）和 WL（（41±9）mm 比（52±14）mm，P=0.02），并降低了 25%的折返发生率（0.08±0.02 比 0.06±0.02，P<0.01）。在心外膜激活图中，伊布利特显著降低了 VF 时更复杂的激活图的百分比。
静脉内给予伊布利特可显著降低 DFT。这可能是由于 VF 时激活模式复杂性的降低。
