Vagal tests - Causes, symptoms and treatment. MF.

The ability of the heart to continuously decline throughout the life of a person is supported by subtle mechanisms of neurohumoral regulation. The heart, like any internal organ, is braided by a network of capillaries and nerve fibers originating from the nerves of the autonomic nervous system. It includes sympathetic and parasympathetic nerves. Sympathetic fibers cause an increase in the frequency and strength of the heart, parasympathetic, on the contrary, a decrease in these indicators. The parasympathetic department is provided by the branches of the vagus nerve( nervus vagus, vagus).

Sometimes there is an accelerated transfer of electrical impulses inside the heart, and then tachycardia develops, manifested by rapid heartbeat, and sometimes a violation of blood circulation in the brain with loss of consciousness. There are several types of tachycardia, some can be dangerous and eliminated only by medications, and some do not cause severe circulatory disturbances and can be stopped with vagal techniques.

Vagal assays are methods of reflex action on the vagus nerve from the nerve endings of other organs, which can lead to a significant decrease in heart rate. These methods are used by the doctor to teach the patient if he has a tachycardia with a favorable course that is not life-threatening, and the samples are performed independently to eliminate unpleasant symptoms caused by an accelerated heart rhythm.

For vagal tests are:

1. carotid sinus massage. Carotid sinus is a division of the common carotid artery into the internal and external carotid arteries. It is the site of the vessel most abundantly provided with receptors that capture the slightest fluctuation in the pressure and gas composition of the blood.
2. Ashner's test - pressing on the closed eyeballs
3. reflex of the "diving" dog( holding the breath and immersing the face in a basin with cold water) and covering the face with ice pieces
4. Valsalva test - straining at the height of a deep inspiration
5.knee squatting with straining
6. Invoking a vomiting reflex by pressing on the root of the tongue
7. causing a cough reflex. What are the basis for vagal tests?

These techniques are based on mechanical stimulation of the nerve fibers of those nerves whose nuclei in the brain can transmit signals to the nucleus of the vagus nerve, as a result of which its branches innervating the heart will be activated. For example, a mechanical increase in pressure in the carotid sinus is picked up by pressoreceptors, signals from them through the carotid branch of the glossopharyngeal nerve enter the brain( nuclei in the medulla oblongata), switch to the nucleus of the vagus nerve. Through the influence of the vagus on the heart, there is a slowing of the heart rate and a decrease in the discharge of blood into the aorta. If you act on the sine from the outside, which happens when you massage, this reflex chain is performed. Reception Ashner caused by the eye-cardiac reflex. Mechanical irritation from the branches of the trigeminal nerve is also transmitted to the brain, where the nuclei of the vagus nerve are activated. Cold exposure to the skin causes bradycardia( uregged heartbeat) due to vagal reflexes from the skin of the face due to activation of the nuclei of the vagus nerve.

Other methods( cough, vomiting, straining) are based not only on reflexes, but also on increasing pressure in the thoracic and abdominal cavities, which leads to the collapse of large veins, slowing the flow of blood in them and reducing the venous influx to the heart. As a result, the force of contractions and heart rate decreases.

Indications for vagal samples

Techniques for the activation of the vagus nerve are mainly used in the following situations:

1. Elimination of unpleasant symptoms of sinus or supraventricular( atrial, atrioventricular) tachycardia independently by the patient or under the supervision of the examining physician.
2. Differential diagnosis of the type of tachycardia( in conjunction with ECG recording)
3. Carotid sinus massage can be used to diagnose the syndrome of carotid sinus failure that occurs in people over 60 years of age and manifests as a short-term loss of consciousness or severe dizziness when turning the head, wearing clotheswith a narrow collar, head inclinations. It is caused by atherosclerotic lesions of the branches of the aorta, inflammatory or tumor processes in the neck. In this case, fainting is not a consequence of neurological diseases or organic damage to the heart.

Contraindications to vaginal samples

You can not carry out tests to restore the normal rhythm on an individual heartbeat, which is accompanied by the following symptoms:

- severe chest pain
- shortness of breath, cough with frothy sputum
- severe weakness, pressure decrease
- loss of consciousness
- pallor or bluenessskin
- convulsions, violation of sensitivity and movements in the limbs.

These symptoms can be signs of life-threatening rhythm disturbances and developed complications( heart attack, stroke, pulmonary edema), so any impact on cardiac activity is dangerous. As soon as possible, call an ambulance.

The doctor should not perform tests if the following conditions are suspected:

- thromboembolism of pulmonary arteries
- acute disorder of the cerebral circulation
- acute coronary syndrome
- pronounced atherosclerosis of the aorta

Vagal sampling procedure

Vagal receptions are performed at home on their own or in the hospital. Massage of the carotid sinus, especially in the elderly, is best done under the supervision of a doctor. The patient on the couch is laid on his back, turning his head to the left and massaging the right side of the neck at the angle of the lower jaw. In parallel, ECG recording and blood pressure measurement are performed. Pressing the sine in a circular motion is carried out for 5 to 10 minutes, after which, if necessary, the doctor can proceed to the massage on the left. At the same time, both sinuses should not be massaged, as this can lead to impoverishment of blood flow in the brain.

Other samples can be taken at home, if the doctor has already taught the patient these techniques. For reflexes from the skin, it is enough to wash with cold water, wipe the skin with an ice cube or immerse your face in a basin of iced water for a few seconds, after holding your breath.

Actually, it is not necessary to induce vomiting, it is enough to apply pressure on the root of the tongue several times with interruptions, by analogy with examination of the tonsils and pharynx by the doctor. You can simulate a cough or stiff, as in the act of defecation.

What best helps to cope with the onset of rapid heart beat, each patient determines by his own experience. The duration of each reception can be from 30 seconds to several minutes, to subjective improvement of the condition, you can repeat several times.

Interpretation of the result

Samples are considered positive if:
- the subjective symptoms of the tachycardia
have occurred - when the sample is performed by an ambulance or in the hospital, the ECG registers the recovery of the correct rhythm

The differences between the different types of tachycardia recorded on the ECG during sampling:
-rhythm with sinus tachycardia becomes less frequent during reflex action, then again accelerates
- with supraventricular tachycardias, the rhythm is either restored, or there is no change( "all or nothing")
- with rhythmic arrhythmia, the rhythm may be slightly slowed down
- with ventricular tachycardia there is no influence on the heart rhythm

Of course, only by the result, the correct rhythm is restored or not, it is impossible to judge whether or notother form of tachycardia, since the final diagnosis is established according to ECG data.

A sample with carotid sinus massage is considered positive if an absence of cardiac contractions( asystole) is recorded on the ECG for more than 3 seconds, or the blood pressure decreases by more than 50 mm Hg. Such a result may indicate a carotid sinus syndrome, but additional examination( duplex neck vessels, MRI of the head and neck) is necessary.

Doctor therapist Sazykina O.Yu.