Monday, February 8, 2010

Carotid sinus massage

Carotid sinus massage (CSM)

It is a vagal maneuver with diagnostic and therapeutic values.

How to do CSM?

- The patient is placed in supine position with neck extended by a pillow under his shoulders. The head is turned away from the side to be massages.

- Palpate the carotid artery pulsation at the angle of the mandible.

- Auscualtate the artery to be massaged looking for bruit.

- While monitoring ECG, apply gentle pressure with rolling from side to side for no more than 5 seconds. The artery is pressed aganist the transverse process of the opposite cervical vertebra.

- The test can be repeated on the opposite side but never do the test on both sides simultaneously.

Effects of CSM:

- cardioinhibitory response: decreasing both sinus rate, atrial rate and AV-nodal conduction.

- Vasodepressor response.

Value of CSM:

A) Diagnostic:

- In arrhythmias: Termination of arrhythmia indicates that in involves the AV node as a part of its reentry circuit (i.e. AV node dependent tachycardia) such as AVNRT and AVRT. In other supraventricular tachycardias, the heart rate will slow down temporarily due to the increase of the AV nodal block. This slowing of ventricular response may reveal hidden flutter waves or abnormal P waves in cases of atrial tachycardias. Gradual and temporary decrease of heart rate occurs with sinus tachycardia. Abrupt and temporary decrease of the heart rate occurs with atrial tachycardias. There will be no effect in ventricular tachycardias. In ventricular tachycardia with retrograde atrial activation, the CSM will cause the retro grade P waves to disappear or to decrease in frequency (due to increased V-A block). (Thanks to my dear colleague, Dr. Mohammed Saber for adding the last sentence).

- In syncope: inducibility of the syncope by CSM is very important unless there is another clear cause. Blood pressure should be monitored during the test. The protocol is different from the above mentioned. A sinus pause of 3 seconds or more, or a drop in blood pressure of 50 mmHg or more are diagnostic of cardotid sinus hypersensitivity.

- In ACS: relieve of chest pain by CSM is diagnostic for angina pectoris (Levine's test). This can be applied also for several minutes. Also, in the presence of LBBB, CSM may cause disappearance of the LBBB and reveal underlying ST elevation.

B) Therapeutic:

- CSM can be used for termination of AVNRT and AVRT.

- CSM may be applied for several minutes to treat acute pulmonary edema with hypertension and myocardial ischemia.

When not to do CSM?

- In patients with know or highly suspected carotid artery disease such as patients with history of stroke or TIA's or carotid artery bruit.

- Patients with previous unfavorable outcome with CSM.

- Be very cautious with elderly patients.

N.B.: The CSM may provoke exaggerated response in cases of digitalis toxicity, even before any other sign of toxicity.

1 comment: