Carotid Sinus Massage: Factors Influencing Response Magnitude and Repeatability

The arterial baroreflex is crucial for short-term blood pressure control – impaired baroreflex function predisposes affected individuals to orthostatic hypotension, fainting and falling. Elderly in-patients who faint display a 79% four-year mortality rate¹. Baroreceptors in the carotid arteries are central to the maintenance of blood pressure during changes in body position. In elderly patients with syncope, 26-60% display a hypersensitive response during carotid sinus massage (CSM)² that is considered pathological. However, up to 35% of healthy older adults also display a hypersensitive response², which questions the use of this test clinically. We hypothesize that CSM exhibits poor repeatability that is impacted by variable methodology. We measured cardiac and vascular responses to CSM in 22 healthy control participants at both the clinically recommended level of the cricoid cartilage² and the ultrasound-guided location of the carotid sinus, on both sides of the neck. CSM was performed both in supine and upright postures. Sham massages were also performed. Each massage was conducted twice to measure repeatability. The locations of the thyroid cartilage, cricoid cartilage, and maximal carotid arterial pulsation were recorded, as well as the location of the carotid sinus. Participants were instructed to breathhold during CSM to eliminate respiratory sinus arrhythmia. The standardized protocol improved repeatability of cardiac responses to CSM threefold compared to previously published data³. The location of maximal pulsation of the carotid artery provided the best anatomical landmark for the location of the carotid baroreceptors. Standardization of CSM protocol improves repeatability and proximity of the massage to the carotid baroreceptors.