Using point-of-care ultrasound (POCUS) to improve carotid massage effectiveness
- Hocuspocus
- 9 hours ago
- 2 min read
It has long been known that carotid sinus massage can terminate supraventricular tachycardia (SVT). This is due to the fact that the carotid sinus, which sits at the bifurcation of the common carotid artery into the internal and external carotid arteries, contains stretch-sensitive baroreceptors. When they are externally compressed during carotid massage, they send signals to the brain, which increases vagal outflow to the heart. The vagus nerve releases acetylcholine at the cardiac tissue, which slows conduction through the atrioventricular node. Therefore, for AV node-dependent SVTs, such as Atrioventricular nodal reentrant tachycardia (AVNRT), carotid sinus massage should slow AV node conduction and potentially terminate the SVT.
In one study of ED patients, physicians performed a 10-second compression just below the angle of the mandible. The carotid sinus massage converted about 25% of patients with SVT. However, pinpointing the exact location of the carotid sinus without ultrasound is difficult. The point of maximal impulse may not necessarily be at the site of the carotid sinus.
A small study examined the utility of locating the carotid bifurcation with point-of-care ultrasound (POCUS), then applying pressure there, and comparing this with another group that chose the location by palpating the maximal impulse of the carotid pulse. They found that when the POCUS was used, the R-R interval was longer and the heart rate was lower than in those who used the blind technique. This suggests that better localization of the carotid body using POCUS results in increased vagal tone, which makes sense.
They also found that the carotid bifurcation was more superior and lateral than suspected by palpation alone.
This was a small study, but it clearly shows that using point-of-care ultrasound to localize the carotid bifurcation and applying pressure there makes more sense than doing it blindly.
To learn more about point-of-care ultrasound of the carotid artery and how to use it to diagnose various diseases, consider getting a copy of The POCUS Textbook in hardcover or Kindle.