Recurrent Syncope in a Case with Mediastinal Lymphoma.

An 83-year-old man suddenly lost consciousness, and his blood pressure dropped. Results of blood analysis were within normal range. A chest radiograph showed enlargement of the left mediastinum. Computed tomographic scan of the chest showed a large mass surrounding the left common carotid artery in the left upper mediastinum. Histology revealed a large B-cell lymphoma. A Holter ECG showed transient sinus bradycardia and atrioventricular block. The power spectrum revealed increase in power of high frequency, suggesting that general vagal activity might be related to bradycardia. Evaluation of autonomic system from high frequency and low frequency components may be useful in examining the mechanisms of sudden bradycardia and/or hypotension of unknown origin.