Clinical characteristics of vasodepressor, cardioinhibitory, and mixed carotid sinus syndrome in the elderly.

PURPOSE: Carotid sinus syndrome (CSS) is frequently overlooked as a cause of syncope in the elderly. It is diagnosed when carotid sinus massage (CSM) produces asystole exceeding 3 seconds (cardioinhibitory CSS), a reduction in systolic blood pressure exceeding 50 mm Hg independent of heart rate slowing (vasodepressor CSS), or a combination of the two (mixed CSS). Most published data pertain to the cardioinhibitory subtype. The recent availability of noninvasive phasic blood pressure monitoring has allowed accurate routine assessment of the vasodepressor response to CSM. The aim of this study was to assess the clinical characteristics of vasodepressor, cardioinhibitory, and mixed CSS. PATIENTS AND METHODS: CSM was carried out on 132 consecutive patients over 65 years referred for investigation of dizziness, falls, or syncope. Massage was performed both supine and upright with continuous electrocardiographic and phasic blood pressure monitoring. Patients exhibiting greater than 1.5-second asystole were given 600 micrograms of intravenous atropine to abolish heart rate slowing and allow assessment of the pure vasodepressor response.
RESULTS: Carotid sinus hypersensitivity was documented in 64 patients (mean age 81 +/- 7 years, 31 male). The response was vasodepressor in 37%, cardioinhibitory in 29%, and mixed in 34%. Thirty-six patients had recurrent syncope, 17 presented with unexplained falls, and the remainder had dizziness alone. Symptoms had been present for a median of 24 months, and the median number of syncopal episodes was four. Twenty-five percent had sustained a fracture and, of these, 93% had not experienced a prodrome. Head movement precipitated symptoms in 47% and vagal stimuli in 73%. Episodes were unwitnessed in two thirds of patients. Twelve patients who presented with falls denied syncope but had witnessed loss of consciousness during CSM. Mean cardioinhibition was 5 +/- 2 seconds and mean vasodepression 61 +/- 9 mm Hg. The blood pressure nadir occurred rapidly at 18 +/- 3 seconds after massage, and baseline values were regained at 30 +/- 6 seconds. The clinical characteristics of patients with vasodepressor, cardioinhibitory, and mixed responses were similar.
CONCLUSION: CSS is an underdiagnosed cause of dizziness, falls, and syncope in the elderly. The vasodepressor form occurs more frequently than previously reported and has clinical characteristics similar to those of the cardioinhibitory and mixed subtypes. Elderly patients with this condition may deny syncope and present with recurrent unexplained falls. CSM, ideally with noninvasive phasic blood pressure monitoring, should be routinely performed in elderly patients with unexplained bradycardic or hypotensive symptoms.