Schley G, Meesmann W, Mescher H, Wilde A, Wild U
Z Kardiol. 1975 Mar;64(3):202-11.
Fibrillation threshold (FS) were determined in 27 mongrel dogs by direct electrical stimulation of the myocardium by 50 Hz AC impulses of 0.20-0.28 sec during the vulnerable period. The FS is the current which just suffices to produce ventricular fibrillation. Sinus rhythm was restored 10 sec after onset of ventricular fibrillation by defibrillation. Determinations of FS were carried out for each animal repeatedly before and 3 min after acute ligation of the circumflex ramus respectively the descendens ramus of the left coronary artery. Post mortem selective coronary angiography was performed in all cases and the extent of spontaneous collateral vessels was estimated by the rate of retrograde contrast radiography of the ligated coronary artery. The FS fell appreciably following acute ligation of both the circumflex ramus and the sescendens ramus. Beside the size of the ligated area (the circumflex ramus supplies a larger area of the myocardium in the dog than the ramus descendens) the extent of collateral supply was the determining factor for the reductions of the FS: Following coronary ligation of the circumflex ramus the FS fell on the average from 24.0 mA to 4.1 mA if no collateral vessels were detectable; in the animals with well developed collaterals the FS was reduced from 24.8 to only 14.1 mA. After acute occlusion of the descendens ramus the FS fell from 27.9 mA to 11.5 mA in the group with not sufficient collateral supply and from 31.2 mA to only 21.5 mA in the group with well developed collaterals. The comparison of the different decreases of the FS after coronary occlusion clearly shows that the influence of the in size differing ischemic areas on the decrease of the FS is particularly evident if no collateral vessels are existent. If collateral vessels are well developed this difference is not significant. These results demonstrate that the influence of well developed collaterals on the decrease of the FS after coronary occlusion exceeds the dependence on the size of the ischemic area.
在27只杂种狗中，于易损期通过0.20 - 0.28秒的50赫兹交流电脉冲直接刺激心肌来测定颤动阈值（FS）。FS是刚好足以引发心室颤动的电流。心室颤动发作10秒后通过除颤恢复窦性心律。分别在急性结扎左冠状动脉回旋支和降支之前及之后3分钟，对每只动物反复进行FS测定。所有病例均进行了死后选择性冠状动脉造影，并通过结扎冠状动脉的逆行造影率来估计自发侧支血管的程度。急性结扎回旋支和降支后，FS明显下降。除了结扎区域的大小（在狗中，回旋支供应的心肌面积比降支大），侧支供应的程度是FS降低的决定因素：结扎回旋支后，如果未检测到侧支血管，FS平均从24.0毫安降至4.1毫安；在侧支血管发育良好的动物中，FS从24.8毫安降至仅14.1毫安。急性闭塞降支后，侧支供应不足组的FS从27.9毫安降至11.5毫安，侧支血管发育良好组的FS从31.2毫安降至仅21.5毫安。冠状动脉闭塞后FS不同程度下降的比较清楚地表明，如果不存在侧支血管，大小不同的缺血区域对FS下降的影响尤为明显。如果侧支血管发育良好，这种差异并不显著。这些结果表明，冠状动脉闭塞后侧支血管发育良好对FS下降的影响超过了对缺血区域大小的依赖。
