Final answer:
Difficulty swallowing after a carotid endarterectomy is the most concerning finding, as it may indicate severe complications requiring immediate attention.
Step-by-step explanation:
The nurse caring for a patient who has had a carotid endarterectomy to reduce carotid stenosis and prevent transient ischemic attacks (TIAs) would be most concerned with the patient experiencing difficulty swallowing postoperatively. This symptom can signal potential complications such as cranial nerve damage or formation of a hematoma, which could compromise the airway or indicate other serious issues. The other postoperative findings listed, such as mild neck edema and neck pain, while important to monitor, generally do not present the same immediate concern as difficulty swallowing.