Vagal Maneuvers: How to Stop your Patient’s SVT
Vagal maneuvers are used in the clinical setting to slow down fast heart rates – primarily for supraventricular tachycardia (SVT) and sometimes rapid atrial fibrillation (AF RVR).
There are numerous physical maneuvers that can slow down the heart rate – and there is an important modified technique which can almost triple your chances of success!
Svt and Vagal Maneuvers
Supraventricular Tachycardia (SVT) is a very rapid regularly arrhythmia caused by a reentrant loop within the heart.
Essentially – the signal goes around and around in a circuit, producing very fast heart rates.
While SVT is an umbrella term for any tachycardia originating above the ventricles of the heart, it usually is used in reference to AV Nodal Reentrant Tachycardia (AVNRT). This arrhythmia is due to a reentrant loop within/near the AV node itself.
Some patients have abnormal conduction tissue in this area, and if a premature beat comes at the wrong time – it can throw them into this very fast heart rhythm.
This condition occurs more often in younger patients, females, and can be secondary to certain triggers like exercise, stimulants, or even alcohol.
Patients will usually be symptomatic and feel palpitations, fatigue, or dizziness. They can also have chest pain, SOB, or syncope.
Remember when the heart is beating this fast, the cardiac chamber’s ability to fill is decreased, and cardiac output can suffer – leading to symptoms.
When a patient comes in with SVT, their heart rate is usually very fast, with rates often between 150-200 bpm.
We want to stop or “break” this rhythm as soon as possible, so the patient does not decompensate.
If we look at the Adult tachycardia ACLS algorithm, we can see that the first thing we do to attempt to stop the SVT in a stable patient is vagal maneuvers.
The Vagus nerve and the Heart
In order to understand vagal maneuvers, you first need to understand how the vagus nerve works.
The vagus nerve is the primary method that the parasympathetic nervous system affects the body.
This is the 10th cranial nerve which travels from your brain throughout the body. This is how the brain controls certain automatic functions.
When the vagus nerve is activated, the following effects on the body occur:
- Bronchial constriction
- Pupillary constriction
- Increased blood flow to the stomach’
- Increased digestion
Remember – “rest and digest”
Regarding the heart, the vagus nerve also has important physiological effects on the cardiac system. These include:
- Slowing of the heart rate
- Slowing of the conduction velocity of the AV node
- Decreases the strength of contractions
As you can see, stimulation of the vagal nerve can be utilized to slow the conduction and increase the refractory period of the AV node which hopefully breaks the SVT reentrant loop, leading to conversion back to normal sinus rhythm (NSR).
There are various physical maneuvers that can stimulate the vagus nerve – and many you may do without trying. These include:
- Cold water immersion
Then there are certain physical maneuvers termed “vagal maneuvers” that we can perform in the hospital to intentionally cause vagal response and hopefully slow down a tachyarrhythmia such as with SVT.
These maneuvers include the Valsalva maneuver and the carotid sinus massage.
But did you know that by modifying the Valsalva maneuver – you can almost triple your chances of success?
The Modified Valsalva Maneuver
The Valsalva maneuver is the classic vagal maneuver used to stimulate the vagus nerve and stop SVT.
This is used on patients who are stable (stable vital signs) and can follow commands.
To perform the Valsalva maneuver, the patient intentionally “bears down” or strains for 10-15 seconds.
This has a 17% success rate in converting SVT. However, by modifying the Valsalva maneuver we can almost triple this success rate!
The Modified valsalva or the positional valsalva maneuver has a significantly higher success rate of 43%!
That’s almost half of your patients with SVT who this can convert back to NSR without any additional medications or interventions.
To perform the modified Valsalva maneuver:
- Have a Physician or APP at the bedside
- Place the patient in a semi-recumbent position (45° Semi-fowlers)
- Have the patient take a normal breath in
- Have them forcefully exhale with a closed glottis (bearing down) for 15 seconds
- Immediately place them supine and raise their legs to 45 degrees for 15 seconds
- Return to semi-fowlers position and watch for up to 1 minute for resolution of the SVT
Clinical Tip: If the patient has trouble bearing down, you can place an empty 10-mL syringe in their mouth and have them blow hard enough to see the plunger move.
As you can see, this technique requires a few assistants, but it is clearly the better option when attempting to convert SVT with vagal maneuvers.
The Carotid Sinus Massage
The carotid sinus massage is a vagal maneuver that you can perform on someone who cannot follow commands.
The carotid sinus is an area located just below the internal carotid artery at the level of the thyroid cartilage, near the pulse.
This area is very sensitive to mechanical pressure, and mechanical pressure to this area can stimulate the vagus nerve.
To perform the carotid sinus massage:
- Place the patient supine with their neck extended toward the opposite side
- Ensure there is no carotid bruit with your stethoscope
- Locate the carotid sinus. This is inferior to the angle of the mandible at the level of the thyroid cartilage near the pulse
- Apply firm pressure for 5-10 seconds
- You can repeat on the other side if needed
The carotid sinus should never be performed in the following circumstances:
- Without a physician / APP at the bedside
- On both sides simultaneously
- In someone with TIA or stroke within the last 3 months
- In someone with known carotid stenosis or active carotid bruit
Complications of Vagal Maneuvers
Any side effects from vagal maneuvers are usually short-lived and an “over-exaggeration” of expected effects.
These include sinus pauses, brief asystole, bradycardia, AV blocks and hypotension.
These will usually fix themselves within seconds to minutes.
Strokes are a major concern with the carotid sinus massage and can happen in <1% of patients.
This is why those with potential carotid stenosis or recent history of strokes should not have the carotid sinus massage.
Aehlert, B. J. (2017). ECGs made easy (6th ed.). Elsevier Health Sciences.
Burns, E. (2019). Supraventricular tachycardia. In ECG Library. Retrieved from https://litfl.com/supraventricular-tachycardia-svt-ecg-library/
Frisch, D. R., Zimetbaum, P. J. (2020). Vagal maneuvers. In UpToDate. Retrieved from https://www.uptodate.com/contents/vagal-maneuvers
Grauer, K., MD. (2014). ECG Pocket Brain: Expanded Version (6th ed., pp. 65-68). Gainesville, FL: KG/EKG Press.
Knight, B. P. (2020). Atrioventricular nodal reentrant tachycardia. In UpToDate. Retrieved from https://www.uptodate.com/contents/atrioventricular-nodal-reentrant-tachycardia
Tintinalli, J. E., Brady, W. J., Laughrey, T. S., & Ghaemmaghami, C. A. (2016). Cardiac Rhythm Disturbances. In Tintinalli’s emergency medicine: A comprehensive study guide (8th ed., pp. 126). McGraw-Hill Education.
Want to Learn More?
If you want to learn more about vagal maneuvers, SVT, and every other cardiac arrhythmia – check out my ECG Rhythm online video course out now!
It’s specifically designed for nurses, and not only teaches you how to identify each arrhythmia, but also why and how they occur, and what to do about it!
If you’re not ready to take that leap yet but still want to learn more about ECG rhythms – be sure to download my free ECG Cheat Sheet below!
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