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BACKGROUND:
Carotid baroreceptors are innervated by vagal nerve fibers coursing in the carotid body. Care must be taken while dissecting at the carotid bulb during carotid endarterectomy to avoid hemodynamic instability. Aberrant carotid body receptors innervations with abnormal pathways have been described. METHODS:
We describe a case of intraoperative asystole occurred during left carotid endarterectomy. Asystole occurred during the division of the posterior belly of the digastric muscle using the Bovie. We describe an aberrant pathway through vagal nerve branches that run through the posterior belly of digastric.
RESULTS:
66 year-old male patient sustained left hemispheric TIA’s due to high grade left carotid stenosis. Preoperative cardiac evaluation was normal. Left CEA was carried on as usual. Carotid branches were dissected without any sequelae or hemodynamic instability. To obtain more distal control on the ICA we elected to divide the posterior belly of the digastric muscle using the Bovie electrocautery. Upon cauterizing the muscle fibers the patient went into asystole. CPR was initiated and patient regained vital signs in less than one minute of CPR. Atropine was given as well. we carried on the rest of the dissection. Any attempt made to divide the digastric using cautery resulted into bradycardia. Muscle was devided between clamps and ties. No further hemodynamic instability was encountered during the rest of the procedure. At the completion patient was neurologically intact. He was seen by cardiology postoperatively and his cardiac workup was negative for any adverse cardiac event. Patient postoperatively sustained some brief episodes of junctional bradycardia. This was treated briefly with isoproterenol drip. Patient was discharged home on no cardiac medications. Postoperative clinic visit was uneventful.
CONCLUSIONS:
We describe an abnormal pathway of carotid baroreceptors vagal innervation through the posterior belly of the digastric. This has not been previously described. We conclude that aberrant vagal nerve fibers may abnormally course through the posterior belly of the digastric muscle. The proximity of the vagal pharyngeal and the superior laryngeal branches to the digastric muscle may have had a role in the hemodynamic instability in our patient.
We recommend a very careful and thoughtful dissection during open carotid procedures. Abnormal vagal fibers innervation to the carotid baroreceptors can lead into disastrous hemodynamic instability in rare patients like ours.