Carotid sinus massage (CSM) is commonly performed as a bedside test for determining the type and sometimes also the mechanism of different rhythm disturbances, or for routine investigation of older patients who experience syncope, dizziness, or unexplained falls.1 Recently, it has been reported that the response to CSM is affected by the patient's position, and in patients with unexplained syncope or drop attacks, upright CSM is recommended if initial supine CSM is not diagnostic.2 ,3 On the other hand, time of day at which massage is performed is usually not taken into consideration.

Circadian rhythm, which is the variability of physiology and biochemistry of humans in a predictable fashion during a 24 hour period, may also have an effect on response to CSM as well as the patient's position. There has been no study, to our knowledge, that has prospectively evaluated the relation between circadian rhythm and response to CSM. For this reason, we conducted such a study.

A total of 120 consecutive patients (mean (SD) age 56.9 (12.4) years, 76 men and 44 women) who were in sinus rhythm were included in the study. Patients with a history or clinical findings consistent with cerebrovascular disease and who had murmurs on carotid arteries were …