Combined
chemotherapy and
radiotherapy increase long-term survival in patients with head and neck
tumors. Late complications of treatment, however, are being recognized increasingly. Surgery or
radiotherapy of the carotid sinuses or brain stem can evoke labile
hypertension and
orthostatic intolerance from acute or subacute baroreflex failure. Here we report cases in which chronic baroreflex failure appeared to develop as a late sequela of neck irradiation. Three patients referred for autonomic nervous system function testing had labile blood pressure and chronic
orthostatic intolerance that developed years after neck irradiation for
cancer. In each patient, heart rate remained constant during performance of the Valsalva maneuver, suggesting baroreflex-cardiovagal failure. All 3 patients had virtually zero baroreflex-cardiovagal gain, quantified by interbeat interval-systolic blood pressure relationships after intravenous
phenylephrine or nitroglycerine. Ambulatory blood pressure monitoring revealed highly variable blood pressure, with sudden pressor and depressor episodes, a characteristic feature of baroreflex failure. Cardiovagal efferent function, assessed by power spectral analysis of heart rate variability during slow, deep respiration, was normal. Sympathetic noradrenergic efferent function, assessed by cold pressor testing and plasma
catecholamine levels during supine rest and
orthostasis, was also normal or increased. These findings indicated a primarily afferent lesion. Carotid ultrasonography revealed intimal thickening and
atheromatous plaques in all 3 patients. We propose that labile
hypertension and
orthostatic intolerance can develop as a late sequela of neck irradiation, due to chronic carotid baroreflex failure, which in turn is due to radiation-induced accelerated development of carotid
arteriosclerosis. Splinting of carotid sinus mechanoreceptors in rigidified arterial walls would impede detection of alterations in blood pressure and thereby disrupt baroreflex regulation of cardiovagal and sympathetic outflows.