Localized Myocardial Responses to Stimulation of Cardiac Sympathetic Nerves

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Abstract
Myocardial contractile force was recorded at three to five positions on the canine heart while progressively more distal portions of the cardiac sympathetic nerves were electrically stimulated. When the electrodes were applied directly to the stellate ganglion or to the ansa subclavia, positive inotropic responses were generally observed on all of the test regions of the heart. However, when more distal branches of the cardiac nerves were stimulated, individual test regions were successively deleted from the general response. By carefully removing narrow strips of epicardium (epicardial denervation) from different portions of the heart, similar deletions in response were observed. These observations indicate that the peripheral autonomic innervation of the heart is distributed to circumscribed regions of cardiac musculature. Contractile segments of a given region of the heart may be organized in series and each component of the chain influences the contraction of neighboring elements, normally innervated segments mechanically interacting with noninnervated regions. Individual units of cardiac muscle may be markedly influenced through local intervention by the sympathetic nerve supply.

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