Effects of acute vagal nerve stimulation on the early passive electrical changes induced by myocardial ischaemia in dogs: heart rate‐mediated attenuation

摘要: Parasympathetic activity during acute coronary artery occlusion (CAO) can protect against ischaemia-induced malignant arrhythmias; nonetheless, the mechanism mediating this protection remains unclear. During CAO, myocardial electrotonic uncoupling is associated with autonomically mediated immediate (i.e. type 1A) arrhythmias and modulate pro-arrhythmic dispersion of repolarization. Therefore, effects acutely enhanced or decreased cardiac parasympathetic on early coupling as measured by electrical impedance (MEI), were investigated. Anaesthetized dogs instrumented for MEI measurements, left circumflex arterial occlusions performed in intact (CTRL) vagotomized (VAG) animals. The CAO was followed either vagotomy vagal nerve stimulation (VNS, 10 Hz, V) VAG dogs. Vagal studied two additional sets In one set heart rate (HR) maintained pacing (220 beats min−1), while other bilateral stellectomy preceded CAO. increased after all A larger increase observed animals (+85 ± 9 Ω, from 611 24 n= 16) when compared control (+43 5 620 20 7). Acute ischaemia abruptly HR (from 155 11 to 193 15 min−1) (+12 1.1 663 18 Ω). contrast, VNS (n= 11) reduced 206 6 73 (−16 2 700 44 These eliminated but not stellectomy. also attenuated ECG-derived indices (e.g. ST segment, 0.22 0.03 versus 0.15 mV) rate-corrected repolarization [terminal portion T wave (TPEc), 84.5 4.2 65.8 5.9 ms; QTc, 340 8 254 16 ms]. exerts negative chronotropic effects, limiting ischaemic repolarization, possibly via a metabolic demand.