Pathophysiological aspects of carotid sinus massage Cardioinhibition and vasodepression occur independent, respond differently to massage duration, and evoke corrective blood pressure responses

We studied the blood pressure (BP) decrease after carotid sinus massage to study cardioinhibition (CI) and arterial vasodepression (aVD), whether CI and aVD occur independent of one another, and how the BP decrease ends.

We measured BP, heart rate (HR), stroke volume, and total peripheral resistance (TPR) retrospectively in carotid sinus massage cohorts in two Dutch syncope centres. Cardioinhibition and aVD were defined as HR and TPR decreasing below 3 SD under pre-massage baseline means. We used the logratio method to analyse changes relative to baseline and tested whether CI and aVD occurred together more often than through chance and whether the responses depended on massage duration and on corrective BP increases. Cardioinhibition occurred in 48% and aVD in 30% of 244 massages of 90 persons. Cardioinhibition and aVD did not occur together more often than randomly. Compared with aVD, CI occurred more often, earlier, faster, and shorter with a larger maximal but similar overall BP-decreasing effect. Longer massage duration yielded a larger BP decrease through stronger aVD. The BP decrease evoked corrective increases of HR and TPR.

Cardioinhibition appears as a phasic response to the onset of massage, independent of aVD, which is a more latent response sensitive to ongoing massage. Blood pressure corrections probably depend on the contralateral carotid sinus and aortic baroreceptors. The BP decrease after sinus massage may in part depend on the efficacy of corrective responses.