Gang E S, Peter T, Karagueuzian H S, Mandel W J, Meesmann M
Division of Cardiology, Cedars-Sinai Medical Center, Los Angeles, California 90048.
Cardiovasc Res. 1987 Nov;21(11):790-5. doi: 10.1093/cvr/21.11.790.
To examine the relation between the ventricular fibrillation threshold and the number of premature extrastimuli delivered to the right ventricle during programmed ventricular stimulation, a clinical stimulation protocol was performed in nine normal, anaesthetised, closed chest dogs. In addition, the ventricular fibrillation threshold was measured in each dog after a train of eight paced (S1) beats (VFT-S2), after a single premature extrastimulus (VFT-S3), and after two extrastimuli (VFT-S4). The VFT-V3 was 32% lower than the VFT-S2 (16(7) mA vs 24(9) mA, p less than 0.001). The VFT-S4, or the current required by the S4 extrastimulus to induce ventricular fibrillation, was 25% lower than the VFT-S3 (12(8) mA vs 16(7) mA, p less than 0.05). The cumulative reduction in the ventricular fibrillation threshold measured by the S1S2S3S4 stimulation protocol was approximately 50%. Although in most dogs the VFT-S4 was still considerably higher than twice threshold current intensity, the results of the study suggest that a possible mechanism for the induction of non-clinical ventricular fibrillation in the clinical electrophysiology laboratory may be the progressive lowering of the ventricular fibrillation threshold caused by the addition of multiple extrastimuli. This may be particularly relevant in patients with an already reduced fibrillation threshold.
为研究程序性心室刺激期间心室颤动阈值与传递至右心室的过早额外刺激数量之间的关系，对9只正常、麻醉、开胸的犬进行了一项临床刺激方案。此外，在每只犬进行8次起搏（S1）搏动（VFT-S2）、单个过早额外刺激（VFT-S3）和两个额外刺激（VFT-S4）后测量心室颤动阈值。VFT-V3比VFT-S2低32%（16(7) mA对24(9) mA，p<0.001）。VFT-S4，即S4额外刺激诱发心室颤动所需的电流，比VFT-S3低25%（12(8) mA对16(7) mA，p<0.05）。通过S1S2S3S4刺激方案测量的心室颤动阈值累计降低约50%。虽然在大多数犬中VFT-S4仍远高于两倍阈值电流强度，但研究结果表明，临床电生理实验室中诱发非临床性心室颤动的一种可能机制可能是多个额外刺激的添加导致心室颤动阈值逐渐降低。这在已经降低颤动阈值的患者中可能尤为重要。
