Axon profiles and terminals showing various degrees of degeneration were present in the vicinity of the nodal cells throughout the period of study. It is concluded that right cervical sympathectomy resulted in a rapid degeneration in some of the cells in the sinuatrial and atrioventricular nodes.
S S Tay, W C Wong, and E A Ling
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1165060