Pathophysiological aspects of carotid sinus massage

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Regulation

Background:

• Carotid sinus massage (CSM) is used to assess autonomic function.
• Understanding the distinct mechanisms of blood pressure (BP) decrease during CSM is crucial for diagnosing syncope.

Purpose of the Study:

• To investigate the characteristics of cardioinhibition (CI) and arterial vasodepression (aVD) following CSM.
• To determine if CI and aVD occur independently.
• To elucidate the factors influencing the termination of BP decrease during CSM.

Main Methods:

• Retrospective analysis of BP, heart rate (HR), stroke volume, and total peripheral resistance (TPR) in 244 CSMs from two Dutch syncope centers.
• Defining CI and aVD based on HR and TPR deviations from baseline.
• Utilizing the logratio method to analyze relative changes and assess the co-occurrence and dependencies of CI and aVD.

Main Results:

• CI occurred in 48% and aVD in 30% of CSMs.
• CI and aVD did not co-occur more frequently than by chance.
• CI was an earlier, faster, and shorter response compared to aVD, with a similar overall BP-lowering effect.
• Longer massage duration enhanced aVD and the overall BP decrease.
• BP decrease triggered corrective increases in HR and TPR.

Conclusions:

• CI is a phasic response to CSM onset, independent of aVD.
• aVD is a more latent response, sensitive to ongoing massage.
• BP correction mechanisms likely involve contralateral carotid sinus and aortic baroreceptors.
• The efficacy of corrective responses may influence the overall BP decrease post-CSM.