What happens during an attack
Normally, an impulse is born in the sinus node and spreads through the conduction system from top to bottom. With supraventricular tachycardia, an additional circle appears in which the impulse begins to rotate, triggering contractions at a high frequency. Most often this is a circle within the atrioventricular node or an additional bundle between the atrium and ventricle, as in WPW syndrome. Due to the short diastole, the ventricles do not have time to fill, cardiac output falls - hence weakness and dizziness. An attack is often triggered by a single extraordinary extrasystole, so the onset is felt like a push.
- Sudden onset with a pounding sensation in the chest
- Rhythmic rapid heartbeat 150–220 per minute
- Weakness, sweating, lack of air
- Dizziness, darkening of the eyes
- Frequent urination after an attack
- An equally sudden ending
Causes and provoking factors
The basis of arrhythmia is an innate feature of the conduction system, so the first attacks often appear at a young age in people with a healthy heart. In itself, many people have this feature, and attacks are triggered by provoking factors: sudden changes in body position, physical activity, stress, lack of sleep, alcohol, strong coffee and energy drinks, some drops for the common cold and weight loss medications. Thyrotoxicosis, anemia, dehydration and deficiency of potassium and magnesium can increase the tendency to arrhythmia. In older people, attacks are more likely to occur due to heart disease.
- Additional pathways and features of the AV node
- WPW syndrome
- Stress, lack of sleep, physical overload
- Caffeine, energy drinks, alcohol, nicotine
- Thyrotoxicosis and anemia
- Potassium and magnesium deficiency, dehydration
- Stimulant medications and nasal drops
What to do during an attack
If an attack has already occurred and the doctor has allowed it, they begin with vagal techniques, which increase the tone of the vagus nerve and often stop the tachycardia: straining with holding the breath for 15 seconds, washing with cold water, coughing. It is better to do this lying down or sitting. Massage of the eyeballs cannot be used, and massage of the carotid artery area is performed only by a doctor. If the methods do not help, the attack lasts longer than 20–30 minutes, chest pain, shortness of breath, and fainting appear, you need to call 103. Taking antiarrhythmic drugs on your own without a prescription is dangerous.
- Sit or lie down, calm down, don’t panic
- Straining and holding your breath for 15 seconds
- Washing with cold water, cold towel on face
- Don't put pressure on your eyeballs
- Call 103 for chest pain, shortness of breath, fainting
- Do not take someone else's antiarrhythmic pills
Survey
The key to the diagnosis is an ECG taken during an attack: it is used to determine the type of tachycardia and choose treatment. Therefore, if possible, you should seek help while the heartbeat continues. If attacks are rare, daily or multi-day monitoring is prescribed, and for very rare episodes, long-term event recording is used. Outside of a seizure, an ECG may reveal signs of WPW syndrome. Echocardiography is needed to exclude structural heart disease. Additionally, thyroid hormones, hemoglobin and electrolytes are checked. The exact mechanism of arrhythmia is clarified by intracardiac electrophysiological study.
- ECG during an attack
- Resting ECG and assessment of WPW signs
- Daily ECG monitoring
- EchoCG
- TSH, hemoglobin, potassium and magnesium
- Electrophysiological study before ablation
Treatment and prevention of attacks
An attack in a hospital is terminated by the administration of drugs, and in severe cases, by electrical cardioversion. To prevent frequent attacks, medications are prescribed that slow down conduction in the AV node, but they must be taken constantly, and they do not eliminate the cause. A radical method is radiofrequency catheter ablation: a catheter is inserted through the vessel and the area of tissue through which the impulse circulates is destroyed. The intervention is low-traumatic and in most cases eliminates arrhythmia forever, so it is offered for frequent and poorly tolerated attacks, and is especially actively considered for WPW syndrome.
- Treating an attack with medications under medical supervision
- Electrical cardioversion for unstable conditions
- Ongoing preventive therapy as prescribed by a cardiologist
- Radiofrequency catheter ablation
- Limit caffeine, energy drinks and alcohol
- Normalize sleep, treat thyrotoxicosis and anemia
- Keep a diary of attacks with their duration and circumstances
