Bufkin B L, Puskas J D, Vinten-Johansen J, Shearer S T, Guyton R A
Department of Surgery, Emory University School of Medicine, Carlyle Fraser Heart Center, Crawford Long Hospital, Atlanta, Georgia 30365-2225, USA.
Ann Thorac Surg. 1998 Oct;66(4):1185-90. doi: 10.1016/s0003-4975(98)00840-6.
Minimally invasive direct coronary artery bypass graft operations have, to date, displayed a higher rate of early graft failure than conventional coronary artery bypass procedures using extracorporeal technology. Construction of the coronary artery anastomosis on a beating heart versus a quiescent heart is likely an important factor in this difference between the two approaches. Controlled intermittent asystole induced by vagal stimulation to give transient nonchemically induced asystole for brief intervals sufficient for placement of coronary artery sutures might improve the precision of minimally invasive direct coronary artery bypass graft anastomoses and reduce graft failure while increasing the technical ease of operation.
The feasibility of producing transient, reversible asystole with combined vagus nerve stimulation and treatment with a pharmacologic regimen of (1) an acetylcholinesterase inhibitor (pyridostigmine, 0.5 mg/kg), (2) a beta-adrenergic receptor blocker (propranolol, 80 microg/kg), and (3) a calcium-channel blocker (verapamil, 50 microg/kg) was studied in a sheep model. Seven animals underwent right vagus nerve stimulation in two modes: (1) a single continuous 60-second impulse and (2) multiple sequential 15-second impulses.
Vagal stimulation alone achieved bradycardia without consistent and reproducible cardiac arrest. After drug administration 6 animals displayed significant potentiation of vagal-induced asystole in the 60-second stimulation protocol (1.6+/-0.9 seconds non-drug-treated versus 52.0+/-5.6 seconds drug-treated; p < 0.05). In the sequential 15-second impulse protocol after drug treatment, 6 animals achieved consistent, escape-free asystole during five to six sequential 15-second stimulations versus a brief pause and bradycardia produced without drug treatment.
Increased acetylcholine activity by acetylcholinesterase inhibition and prevention of electromechanical escape activity by beta-adrenergic receptor and calcium-channel blockade during vagal stimulation produced a marked potentiation of vagal-induced asystole and a means of achieving controlled intermittent asystole. Controlled intermittent asystole achieved by pharmacologic potentiation of vagal-induced asystole may be a useful technique for enhancing technical ease in minimally invasive direct coronary artery bypass graft operations.
迄今为止，微创直接冠状动脉旁路移植手术与使用体外循环技术的传统冠状动脉旁路移植手术相比，早期移植失败率更高。在跳动心脏与静止心脏上进行冠状动脉吻合术的构建可能是这两种手术方法存在差异的一个重要因素。通过迷走神经刺激诱导可控的间歇性心脏停搏，以产生短暂的非化学诱导心脏停搏，持续时间足以放置冠状动脉缝线，这可能会提高微创直接冠状动脉旁路移植吻合术的精度，减少移植失败，同时提高手术操作的技术简便性。
在绵羊模型中研究了联合迷走神经刺激和药物治疗方案（1）乙酰胆碱酯酶抑制剂（新斯的明，0.5mg/kg）、（2）β-肾上腺素能受体阻滞剂（普萘洛尔，80μg/kg）和（3）钙通道阻滞剂（维拉帕米，50μg/kg）产生短暂、可逆性心脏停搏的可行性。7只动物以两种模式接受右侧迷走神经刺激：（1）单次持续60秒冲动；（2）多次连续15秒冲动。
单独迷走神经刺激可导致心动过缓，但无一致且可重复的心脏停搏。给药后，6只动物在60秒刺激方案中迷走神经诱导的心脏停搏有显著增强（未用药治疗时为1.6±0.9秒，用药治疗时为52.0±5.6秒；p<0.05）。在药物治疗后的连续15秒冲动方案中，6只动物在五到六次连续15秒刺激期间实现了持续、无逸搏的心脏停搏，而未用药治疗时仅产生短暂的停顿和心动过缓。
在迷走神经刺激期间，通过抑制乙酰胆碱酯酶增加乙酰胆碱活性，并通过β-肾上腺素能受体和钙通道阻滞防止电机械逸搏活动，可显著增强迷走神经诱导的心脏停搏，并实现可控的间歇性心脏停搏。通过药物增强迷走神经诱导的心脏停搏实现的可控间歇性心脏停搏，可能是提高微创直接冠状动脉旁路移植手术技术简便性的一种有用技术。
