Наджелудочковая тахикардия: причины, диагностика и лечение.

The cause is not known. Future episodes can be prevented by catheter ablation. Problems typically begin in those 12 to 45 years old. Episodes start and end suddenly. The AV node is the structure that controls how electrical signals travel between the upper chambers (atria) and lower chambers (ventricles). During normal sinus rhythm, these signals pass through only one pathway, known as the fast pathway. The fast pathway conducts signals quickly but has a longer rest period before it can send another signal. However, in people with PSVT caused by atrioventricular nodal reentry, both the fast and the slow pathways are activated. The slow pathway conducts signals more slowly but has a shorter rest period. During PSVT episodes, an irregular heartbeat is triggered by an early electrical signal from one of the atria. This premature signal enters both pathways simultaneously. It encounters no problem traveling along the slow pathway because its conduction speed matches up well with this specific arrhythmia type. However, it faces difficulty passing through effectively down the faster path since it takes slightly longer for that path to be ready following the conduction of a recent signal. At this point, if retrograde or backward flow overcomes the forward movement's pace in the fast pathway, then unwanted feedback further intensifies the rapid heartbeat until something intervenes to stop the episode. There is currently no solid understanding on what stops the episode in PSVT. AV nodal blocking can be achieved in at least three ways:

A number of physical maneuvers increase the resistance of the AV node to transmit impulses (AV nodal block), principally through activation of the parasympathetic nervous system, conducted to the heart by the vagus nerve. These manipulations are collectively referred to as vagal maneuvers. The Valsalva maneuver should be the first vagal maneuver tried and works by increasing intra thoracic pressure and affecting baroreceptors (pressure sensors) within the arch of the aorta. It is carried out by asking the patient to hold his/her breath while trying to exhale forcibly as if straining during a bowel movement. Holding the nose and exhaling against the obstruction has a similar effect. Pressing down gently on the top of closed eyes may also bring heartbeat back to normal rhythm for some people with atrial or supraventricular tachycardia (SVT). This is known as the oculocardiac reflex.

Adenosine, an ultra short acting AV nodal blocking agent, is indicated if vagal maneuvers are not effective. If unsuccessful or the PSVT recurs, calcium channel blockers, such as diltiazem or verapamil, are recommended. Adenosine can be administered together with nondihydropyridine calcium channel blockers. SVT that does not involve the AV node may respond to other anti arrhythmic drugs such as sotalol or amiodarone.

If the person is hemodynamically unstable or other treatments have not been effective, synchronized electrical cardioversion may be used. In children this is often done with a dose of 0.5 to 1 J/Kg.

Radiofrequency catheter ablation (RFCA) is a safe and effective treatment in both adults and children. RFCA is considered a minimally invasive procedure rather than surgery. It does not involve making large incisions or opening up the chest cavity. Instead, it is performed using thin catheters that are inserted through blood vessels and guided to the heart. The catheter delivers radiofrequency energy to specific areas of the heart to disrupt abnormal electrical pathways causing arrhythmias. While it may require mild sedation or local anesthesia, it doesn't typically involve extensive cutting or suturing of tissue associated with traditional surgical procedures. Over the decade of 2010s, there have been significant advancements in catheter ablation techniques for ventricular arrhythmias, including improved mapping methods like ultra high density mapping and innovative energy sources like electroporation. New types of catheters, such as lattice and saline enhanced radiofrequency catheters, provide more precise and longer lasting tissue damage. Additionally, cardiac imaging technologies like MRI can help identify abnormal areas causing arrhythmias and evaluate the success of the ablation procedure.