In this case report, we rendered a 22 year old woman with the diagnosis of neurogenic thoracic outlet syndrome. We have evaluated her symptoms of palpitation with Holter monitorization during Roos test before and after surgery where transaxillary first rib resection and scalenectomy were performed. Postoperatively she improved and the tachycardia resolved. We propose that stellate ganglion or postganglionic efferent sympathetic fibers forming the cardiac plexus are exposed to compression while Roos test is being performed. Due to this irritation, there can be an increase in the cardiac sympathetic activity.