Background: Falls and syncope in the elderly may be caused by hypersensitivity in the high-pressure baroreflex
control - carotid sinus syndrome (CSS). The pathophysiological process causing CSS remains poorly
understood.
Methods: We studied the hemodynamic response to carotid sinus massage (CSM) and compared this to other
measurements of autonomic cardiovascular control in patients suspected of syncope-related falls. One hundred
patients (≥80 years-old) referred to our syncope unit due to recurrent falls or possible syncope participated. CSM
was performed in the supine and head-up tilted (HUT) positions. A hypersensitive response was defined by
current guidelines.
Results: In the supine position, heart rate (HR) and systolic blood pressure (SBP) decreased during CSM on the
right side by 17.0 +/- 15.2 min-1 and 32.5 +/- 25.5 mmHg, and on the left side by 12.8 +/- 14.3 min-1 and 22.7 +/-
20.7 mmHg, respectively. Changes in SBP were greater in the head-up tilted position (right side; p=0.029, left
side; p=0.007). Hypersensitive responses were elicited in 45 patients. We found orthostatic hypotension (OH)
(r=-0.275, p=0.015), not CSS, to be inversely correlated to low frequency HR variability during HUT.
Conclusions: The hemodynamic response to CSM has a well-defined pattern and differs both with respect to the
stimulus site and patient position. We suggest that CSS is not a distinct pathophysiological process or disease
entity but rather an acquired cardiovascular instability due to age-related degeneration and following mismatch
between different components of cardiovascular regulation.