SIGNIFICANCE OF SPINAL AUTONOMIC LOCI IN POST CORONARY LIGATION ARRHYTHMIA

Two-stage coronary artery ligation in dogs consistently induced ventricular ectopics and raised plasma catecholamine and free fatty acid levels. Ether or pentobarbitone anesthesia completely abolished the cardiac irregularities and lowered the plasma catecholamine and free fatty acid levels. Chloralose anesthesia did not affect the ventricular ectopics, plasma catecholamines or free fatty acids. Hemorrhagic hypotension did not alter the incidence of ventricular ectopics following coronary artery ligation. In chloralose anesthetized dogs the neural factors concerned in the genesis of cardiac arrhythmias following coronary artery ligation were analyzed by surgical and pharmacological procedures. Bilateral vagotomy, mid-collicular or spinal (C1) transection did not significantly influence the incidence of ventricular ectopics. Spinal (C4-T6) cord destruction completely abolished ventricular ectopics, restored normal rhythm and lowered plasma catecholamine and free fatty acid levels. Spinal anesthesia with xylocaine was also found to completely abolish ventricular ectopics. Cardiac sympathectomy or bilateral adrenalectomy significantly inhibited the ventricular ectopics and lowered plasma catecholamines and free fatty acids. Ganglionic blockade, adrenergic neuron blockade or .beta.-adrenoceptor blockade restored normal sinus rhythm. The results implicate the prime importance of spinal autonomic loci in the integration of reflex cardiac arrhythmia arising from myocardial ischemia. The afferent and efferent pathways of the reflex seem to be in the sympathetics.