Bonometti C, Hwang C, Hough D, Lee J J, Fishbein M C, Karagueuzian H S, Chen P S
Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.
Circ Res. 1995 Aug;77(2):407-16. doi: 10.1161/01.res.77.2.407.
This study was designed to test the hypothesis that the effects of a strong electrical stimulus on reentrant wavefronts in ventricular fibrillation (VF) are dependent on the timing of the stimulus. We studied six open-chest dogs by computerized mapping techniques. A plaque electrode array with up to 509 bipolar electrodes was placed on the right ventricular epicardium. The interelectrode distance was 1.6 mm, and the interpolar distance was 0.5 mm. After eight baseline pacing stimuli (S1) with cycle lengths of 300 ms, a strong premature stimulus (S2) (73 +/- 10 mA) was given to induce VF. In subsequent episodes, a second strong premature stimulus (S3) was given at progressively longer S2-S3 intervals in 20-ms increments. The results showed that, at baseline, the S2 consistently induced figure-eight reentry and VF. The VF cycle length immediately after the S2 averaged 108 +/- 17 ms. The S3 resulted in one of the following responses: (1) termination of reentry and VF; (2) induction of different reentrant wavefronts or a focal pattern of repetitive activation; or (3) persistence of the same figure-eight reentry. The intervals between the S3 and the immediately preceding activation at the site of the S3 (the recovery intervals) were 39 +/- 12 ms (range, 20 to 60 ms) and 61 +/- 20 ms (range, 30 to 90 ms) for response patterns 1 and 2, respectively. The recovery intervals associated with response pattern 3 were either < or = 30 ms (22 +/- 8 ms) or > or = 80 ms (94 +/- 15 ms). The differences among these four intervals were significant (P < .001). We conclude that the effects of strong electrical stimulation on the reentrant wavefronts in VF are dependent on the recovery interval since the previous local activation. A protective zone occurred between 20 and 60 ms, during which time a strong electrical stimulus could terminate reentry and abort VF. This zone was followed by a vulnerable period during which new activation wavefronts could be induced. If a strong electrical stimulus was given shortly after or sufficiently long after the previous local activation, the same figure-eight reentrant pattern continued.
强电刺激对心室颤动（VF）折返波前的影响取决于刺激的时机。我们通过计算机映射技术对6只开胸犬进行了研究。将一个带有多达509个双极电极的片状电极阵列置于右心室心外膜。电极间距为1.6毫米，极间距为0.5毫米。在给予8次周期长度为300毫秒的基线起搏刺激（S1）后，给予一次强早搏刺激（S2）（73±10毫安）以诱发VF。在随后的发作中，以20毫秒的增量逐渐延长S2 - S3间隔，再给予第二次强早搏刺激（S3）。结果显示，在基线时，S2始终诱发8字形折返和VF。S2后立即出现的VF周期长度平均为108±17毫秒。S3导致以下反应之一：（1）折返和VF终止；（2）诱发不同的折返波前或重复激活的局灶模式；或（3）相同的8字形折返持续存在。对于反应模式1和2，S3与其在S3部位紧邻的前一次激活之间的间隔（恢复间隔）分别为39±12毫秒（范围为20至60毫秒）和61±20毫秒（范围为30至90毫秒）。与反应模式3相关的恢复间隔要么≤30毫秒（22±8毫秒），要么≥80毫秒（94±15毫秒）。这四个间隔之间的差异具有显著性（P <.001）。我们得出结论，强电刺激对VF折返波前的影响取决于自前一次局部激活后的恢复间隔。在20至60毫秒之间出现一个保护区，在此期间强电刺激可终止折返并中止VF。该区域之后是一个易损期，在此期间可诱发新的激活波前。如果在前一次局部激活后不久或足够长的时间后给予强电刺激，相同的8字形折返模式会持续。
