General information
Tachycardia, also known as paroxysmal tachycardia, is known to almost everyone. A tachycardia is defined by a heart rate of more than 100 beats per minute. Usually, the palpitations start very suddenly, then you can feel your heartbeat all the way down to your throat or in your entire chest (so-called palpitations). In case of anticipation, excitement or fear, tachycardia is usually completely harmless and slowly subsides again. However, tachycardia can also be an indication of an organic heart or thyroid disease and should be clarified by the family doctor if other symptoms besides tachycardia occur, such as heart stumbling, shortness of breath, nausea or dizziness.
How does tachycardia develop?
Every person experiences extra beats of the heart, so-called extrasystoles, throughout the day. An extrasystole is harmless, but it can trigger circular excitation. In this excitation cycle, the excitation wave returns again and again along the same path to the output of the electrical excitation.
Such a circulating excitation is also called reentry circulation and can occur in the heart chambers, for example at the edge of a scar in the heart muscle tissue after a heart attack. In addition, in some patients there are congenital pathways between the atria and the ventricles that can promote reentry circulation. A reentry circulation leads to a tachycardia with a regular rhythm.
If, instead of this regular tachycardia, many smaller, irregular excitation circuits occur, atrial fibrillation or ventricular fibrillation is the result. While ventricular fibrillation leads to immediate circulatory arrest and affected patients have to be resuscitated, atrial fibrillation is often not noticed because it does not or only slightly restrict the circulatory function. However, tachycardia can not only be triggered by the mechanism of circulating excitation, but also by the so-called “increased automatism”, which accelerates the frequency of the sinus node. The sinus node is the clock generator of the heart and can be stimulated to a faster frequency by the autonomic nervous system, various drugs and stimulants such as caffeine and other factors that affect the cardiovascular system, thus triggering tachycardia.