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A Journal on Cardiac, Vascular and Thoracic Surgery

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The Journal of Cardiovascular Surgery 1998 August;39(4):469-71

language: English

Right ­vagal ­nerve stim­u­la­tion dur­ing min­i­mal­ly inva­sive ­direct cor­o­nary ­artery ­bypass graft­ing in dogs. A pre­lim­i­nary ­study

Hayashi I., Yamamoto T., Hosoda Y.

From the Department of Thoracic and Cardiovascular Surgery, Juntendo University, Tokyo, Japan


Background. Minimal ­access cor­o­nary ­artery ­bypass graft­ing with­out car­di­o­pul­mo­nary ­bypass has ­been ­used ­with increas­ing fre­quen­cy. However, ­some sur­geons are ­still unwill­ing to per­form MID­CAB ­because the anas­tom­o­sis is tech­ni­cal­ly demand­ing. The aim of ­this ­study was to ­assess wheth­er auto­nom­ic acti­va­tion via ­right ­vagal ­nerve stim­u­la­tion ­will be an effec­tive sup­port tech­nique on ­heart ­rate dur­ing MID­CAB in ­dogs.
Experimental ­design. Preliminary ­study.
Setting. Cardiotho­rac­ic Surgery Unit, University Clin­ic.
Methods. The ­right cer­vi­cal ­vagal ­nerve was stim­u­lat­ed in ­five ­dogs. In one dog, ­right thor­a­cot­o­my was per­formed to iso­late the ­vagal ­nerve. Bipolar ­hook elec­trodes ­were ­attached to the ­vagal ­nerve. The ­vagal ­nerve was stim­u­lat­ed (3~5 mA, 40 Hz) for a few sec­onds ­while sutur­ing the cor­o­nary ­artery. Experiments ­were con­duct­ed in two ­groups. In ­Group I, two ­dogs ­received ­vagal stim­u­la­tion via the ­right ­neck, and one dog ­received ­vagal stim­u­la­tion via the ­right tho­rac­ic cav­ity ­approach. In ­Group II, all ­vagal stim­u­la­tions ­were per­formed via the ­neck dur­ing intra­ve­nous infu­sion of dil­tia­zem (10 mg/hrs) or verap­a­mil (5 mg/hrs).
Results. In ­Group I, ­when the cer­vi­cal ­nerve stim­u­la­tion start­ed the ­heart ­rate ­decreased ­from 190 to 45 ­beats/min in one dog , and ­from 180 to 42 ­beats/min in ­another dog. During tho­rac­ic ­nerve stim­u­la­tion, the ­heart ­rate ­decreased ­from 205 to 70 ­beats/min. In ­Group II, ­vagal stim­u­la­tion of one dog (10 mg/hr dil­tia­zem) ­caused ven­tric­u­lar ­arrest, and in the oth­er ­dogs (5 mg/hr verap­a­mil) ­vagal stim­u­la­tion ­caused ­marked brad­y­car­dia ­with atri­o­ven­tric­u­lar ­block. After the ces­sa­tion of ­nerve stim­u­la­tion, the ­heart ­rate ­returned to nor­mal ­sinus ­rhythm imme­di­ate­ly in ­each dog.
Conclusions. Based on our find­ings, ­this ­type of auto­nom­ic stim­u­la­tion (espe­cial­ly ­with IV admin­is­tra­tion of dil­tia­zem or verap­a­mil) can be an effec­tive tech­nique in reduc­ing ­heart ­beats, ­thus obtain­ing rel­a­tive­ly ­quiet sur­gi­cal ­field for cor­o­nary anas­tom­o­sis in ­CABG with­out car­di­o­pul­mo­nary ­bypass.

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