Osswald S, Trouton T G, O'Nunain S S, Holden H B, Ruskin J N, Garan H
Cardiac Unit, Massachusetts General Hospital, Harvard Medical School, Boston 02114.
Circulation. 1994 Nov;90(5):2501-9. doi: 10.1161/01.cir.90.5.2501.
Certain biphasic waveforms with specific time ratios of positive and negative components require less energy for successful defibrillation of the fibrillating ventricles than monophasic waveforms. However, if more efficient waveforms were also to be associated with more injurious effects on myocardial function, they might not provide a true biological advantage. This study investigates the relation between defibrillation efficacy and potential toxicity of monophasic and asymmetric, single capacitor, biphasic waveforms with equal durations of positive and negative components.
The myocardial lactate extraction rate (LER) was used to measure the injurious effects on myocardial oxidative metabolism of two synchronized 35-J shocks in sinus rhythm. LER, mean arterial pressure (MAP) and, in a subset of experiments, cardiac output (CO) and coronary blood flow (CBF) were measured at baseline, 30 seconds, 60 seconds, 90 seconds, 150 seconds, 300 seconds, and 600 seconds after the shocks. In 12 dogs, three different waveforms (M 10: monophasic 10 milliseconds; BI 10: biphasic 10 milliseconds; BI 20: biphasic 20 milliseconds) were tested as series of two consecutive shocks (60 seconds apart) resulting in a total of 36 sets of data. At baseline, LER was 25 +/- 11%. After monophasic shocks, LER decreased significantly more than after biphasic shocks (LER at 150 seconds: M 10: -6 +/- 31% versus BI 10: 21 +/- 15% versus BI 20: 21 +/- 16%; M 10 versus BI 10 and M 10 versus BI 20, P < .05) and showed also a slower recovery (LER at 300 seconds: M 10: 1 +/- 24% versus BI 10: 20 +/- 11% versus BI 20: 20 +/- 15%; M 10 versus BI 10 and M 10 versus BI 20, P < .05). The maximal decrease in LER was 41 +/- 27% for M 10 compared with 18 +/- 15% for BI 10 and 15 +/- 11% for BI 20 (both, M 10 versus BI 10 and M 10 versus BI 20, P < .05). There was a similar decrease in CO and MAP, with the lowest MAP after monophasic shocks. The maximal decrease in MAP was significantly greater after M 10 compared with BI 20 (-29 +/- 15 mm Hg versus -13 +/- 11 mm Hg, P < .05). The defibrillation threshold was 18.6 +/- 8 J for M 10 compared with 11.5 +/- 4.0 J for BI 10 (P < .05) and 15.0 +/- 6.1 J for BI 20, respectively (P = NS).
Our results suggest that these specific biphasic waveforms are associated with less injurious effects on myocardial oxidative metabolism and hemodynamic performance. Given their higher defibrillation efficacy as well, biphasic waveforms may provide important long-term benefits in patients receiving frequent shocks from implantable cardioverter-defibrillators.
某些具有特定正负极性成分时间比例的双相波形，与单相波形相比，在使颤动的心室成功除颤时所需能量更少。然而，如果更高效的波形也会对心肌功能产生更大的损伤作用，那么它们可能并不能带来真正的生物学优势。本研究探讨了单相和不对称、单电容、正负极性成分持续时间相等的双相波形的除颤效果与潜在毒性之间的关系。
采用心肌乳酸摄取率（LER）来测量窦性心律下两次同步35J电击对心肌氧化代谢的损伤作用。在电击后基线、30秒、60秒、90秒、150秒、300秒和600秒时测量LER、平均动脉压（MAP），在部分实验中还测量心输出量（CO）和冠状动脉血流量（CBF）。在12只犬中，测试了三种不同波形（M 10：单相10毫秒；BI 10：双相10毫秒；BI 20：双相20毫秒），以连续两次电击（间隔60秒）的形式进行，共得到36组数据。基线时，LER为25±11%。单相电击后，LER的下降幅度明显大于双相电击后（150秒时的LER：M 10：-6±31%，BI 10：21±15%，BI 20：21±16%；M 10与BI 10以及M 10与BI 20相比，P<.05），且恢复也较慢（300秒时的LER：M 10：1±24%，BI 10：20±11%，BI 20：20±15%；M 10与BI 10以及M 10与BI 20相比，P<.05）。M 10的LER最大降幅为41±27%，而BI 10为18±15%，BI 20为15±11%（M 10与BI 10以及M 10与BI 20相比，均P<.05）。CO和MAP也有类似下降，单相电击后的MAP最低。M 10后的MAP最大降幅明显大于BI 20（-29±15 mmHg对-13±11 mmHg，P<.05）。M 10的除颤阈值为18.6±8 J，BI 10为11.5±4.0 J（P<.05），BI 20为15.0±6.1 J（P=无显著性差异）。
我们的结果表明，这些特定的双相波形对心肌氧化代谢和血流动力学性能的损伤作用较小。鉴于其较高的除颤效果，双相波形可能为接受植入式心脏复律除颤器频繁电击的患者带来重要的长期益处。
