A 32-year-old man undergoes evaluation for episodes of paroxysmal supraventricular tachycardia. An electrophysiology study reveals focal atrial tachycardia that originates in the crista terminalis of the right atrium. Radiofrequency ablation is planned to destroy the ectopic focus and treat the arrhythmia. Which of the following nerves is in close proximity to the treatment site and is at risk for injury during the ablation?

Question

A 32-year-old man undergoes evaluation for episodes of paroxysmal supraventricular tachycardia.  An electrophysiology study reveals focal atrial tachycardia that originates in the crista terminalis of the right atrium.  Radiofrequency ablation is planned to destroy the ectopic focus and treat the arrhythmia.  Which of the following nerves is in close proximity to the treatment site and is at risk for injury during the ablation?

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11ec160b_35a9_1f1c_9249_cf2304cf5c17_MD0001_00 Paroxysmal supraventricular tachycardias (PSVTs) are arrhythmias that occur intermittently and have abrupt onset and offset. They arise from regions of abnormal electrical activity that occur in the atrioventricular node, an accessory pathway, or the atria. Radiofrequency ablation can be used to destroy the inciting cardiomyocytes and cure the arrhythmia. The crista terminalis, located in the right atrium, is a common site of origination for atrial PSVT. However, the right phrenic nerve, which innervates to the right hemidiaphragm, courses along the pericardium that overlies the right atrium and is at risk of injury during procedures that target structures in or near the right atrium (eg, crista terminalis, cavotricuspid isthmus, right-sided pulmonary veins). Such injury is typically recognized by elevation of the right hemidiaphragm on chest x-ray. (Choice A) The spinal root of the accessory nerve (cranial nerve XI) courses superiorly from the upper spinal cord through the foramen magnum to join with the cranial root. The combined roots then exit the cranium through the jugular foramen to provide motor innervation to the sternocleidomastoid and trapezius muscles. There is risk of injury during biopsy or lymph node dissection in the neck, but not during procedures involving the right atrium. (Choice B) The long thoracic nerve arises from the lower cervical spinal cord and courses laterally and inferiorly to provide motor innervation to the serratus anterior muscle. Injury can occur during breast surgery or chest-tube placement (resulting in a "winged" scapula); however, due to its lateral location, the nerve is not at risk of injury during procedures involving the right atrium. (Choice D) The recurrent laryngeal nerve is a branch of the vagus nerve (cranial nerve X) that courses underneath the aortic arch on the left and the brachiocephalic trunk on the right to provide motor, sensory, and parasympathetic innervation to the upper esophagus, trachea, and portions of the larynx. It is at risk of injury during thyroid surgery but not during procedures involving the right atrium. (Choice E) The sympathetic trunk parallels the length of the spinal column on both sides and provides sympathetic innervation throughout the body. Injury leads to Horner syndrome (ie, miosis, ptosis, anhydrosis) and can occur during spinal surgery, but not during procedures involving the right atrium. Educational objective: The right phrenic nerve courses along the pericardium overlying the right side of the heart and is at risk for injury during procedures in or near the right atrium (eg, radiofrequency ablation). Right phrenic nerve injury is typically recognized by elevation of the right hemidiaphragm.

A 32-Year-Old Man Undergoes Evaluation for Episodes of Paroxysmal Supraventricular