A vagal maneuver may be used to halt an episode of superventricular tachycardia (SVT). In order to understand how a vagal maneuver works to slow or terminate a rapid heart rate, it’s helpful to understand the pathophysiology underlying SVT.
SVT is a rapid heartbeat which originates in the chambers above the ventricles. It can occur due to a large variety of reasons, such as structural abnormalities and heart failure. There are a few different classifications of SVT based on the electrical pathway which is taken from the atria. For example, SVT in which the electrical signal travels from the AV node to the ventricles and back again to the atria is called AV reentry tachycardia (AVRT). When the electrical signal travels in a circle through the fibers in and around the AV node, the rhythm is referred to as AV nodal reentry tachycardia (AVNRT).
The vagus nerve supplies parasympathetic motor fibers to the myocardium. Vagal maneuvers involve different techniques used to stimulate the receptors in the internal carotid arteries. This stimulation causes a reflex stimulation of the vagus nerve which results in the release of acetylcholine, which may in turn slow the electrical impulse through the atrioventricular node and slow the heart rate. Depending on the patient’s condition, a vagal maneuver may be advised before trying medication or other more invasive procedures to terminate SVT.
Vagal Maneuver Techniques
There are different types of vagal maneuvers that can be used to slow a person’s heart rate. There is not one maneuver which will work for all patients. In some instances, it may take a little trial and error to determine what technique works best for an individual patient. All of the procedures or techniques below may stimulate the vagal nerve.
Bearing Down: Bearing down, which medically is referred to as the Valsalva maneuver, is one of the most common ways to stimulate the vagus nerve. The patient is instructed to bear down as if they were having a bowel movement. In effect, the patient is expiring against a closed glottis. An alternative way to perform a Valsalva maneuver is to tell the patient to blow through an occluded straw for several seconds. These maneuvers increase intrathoracic pressure and stimulate the vagus nerve.
Coughing: Coughing creates the same physiological response as bearing down, but some people may find it easier to perform. The cough must be forceful and sustained i.e. a single cough will likely not be effective in terminating an arrhythmia
Cold Stimulus to the Face: This technique involves emerging the face in ice cold water. Alternative methods include placing on icepack on the face or a washcloth soaked in ice water. The cold stimuli to the face should last about 10 seconds. This type of vagal maneuver creates a physiological response similar to that which occurs if a person is submerged in cold water (diver’s reflex).
Gagging: Although it may not sound pleasant, gagging also stimulates the vagus nerve and can stop an episode of SVT. A tongue depressor is briefly inserted into the mouth, touching the back of the throat, which causes the person to reflexively gag. The gag reflex stimulates the vagus nerve.
Carotid Massage: Another type of vagal maneuver is carotid massage. This technique is performed with the patient’s neck in an extended position, with the head turned away from the side being massaged. Only one side should be massaged at a time. Pressure is applied underneath the angle of the jaw in a gentle circular motion for about 10 seconds. The patient should be monitored throughout. This technique may not be recommended for everyone. For example, patients who have carotid artery stenosis and a history of smoking may not be good candidates for the procedure.
Patients should be instructed on how to perform vagal maneuvers properly before attempting one. In addition, carotid massage is only recommended for select patients and may only performed by a physician.
It is essential to understand that it is not always appropriate to have a patient attempt a vagal maneuver. For instance, if the patient has SVT and is unstable, vagal maneuvers may delay definitive treatment such as cardioversion. Some potential complications to be aware of during or after a vagal maneuver include dizziness and an arrhythmia originating in the ventricles.
Most patients can easily be taught how to perform vagal maneuvers and they can be done anywhere. If a physician ensures a patient is an appropriate candidate for a vagal maneuver, the patient can be instructed to perform maneuvers at home in some situations.
Wake Forest Baptist Health. Vagal Maneuvers for a Fast Heart Rate. http://www.wakehealth.edu/Health-Encyclopedia/Health-Topics/Vagal-Maneuvers-For-A-Fast-Heart-Rate.htm#ps1283-sec Accessed August 2014.
Wang, P. MD, Estes, M. MD. Superventricular Tachycardia. Circulation. http://circ.ahajournals.org/content/106/25/e206.full Accessed August 2014.