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This video shows a modified Valsalva maneuver being used in the emergency treatment of stable SVT supraventricular tachycardia.

This is a beautiful example of how manipulating the nervous system & leveraging physiology can be used as a simple, cost-free treatment. So, let's talk about why & how it works:

The modified Valsalva can be divided into 3 phases:

Phase 1: Increasing intrathoracic pressure: At the beginning of this video, you'll see the patient perform a standardized 'strain' blowing into a 10mL syringe for about 15 seconds while sitting up or in a semirecumbent position. Bearing down like this contracts the thoracic & abdominal muscles & causes a drop in blood flow back to the heart decreased preload & brain. This drop stimulates the baroreceptor reflex & compensates by triggering the sympathetic nervous system stress response in an attempt to raise the blood pressure, cardiac output & peripheral vascular resistance.

Phase 2: Causing a sudden drop in the intrathoracic pressure:

After the 15 second strain, just prior to being laid flat or simultaneously, the patient will stop blowing into the syringe, this causes the pressure in the thorax to suddenly decrease, subsequently increasing blood flow back to the heart & increasing the preload leading to the opposite of phase 1: a compensatory increase in parasympathetic vagalactivity aimed at decreasing heart rate + increasing the relaxation response.
Phase 3: Laying flat & raising the legs to 45 degrees:

This postural modification causes even more blood flow back to the heart, leading to an increase in stroke volume & cardiac output. This causes further vagal - parasympathetic - stimulation, which compensates for these changes by telling the body to decrease the heart rate via the SA node THIS can convert the patient back into sinus rhythm! A phenomenon beautifully depicted in this video!

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