BasicsPhysiology of the heart | Cardiac arrhythmia

BasicsPhysiology of the heart

The heart rhythm is the temporal sequence of contractions of the “pumping organ” heart. A regular rhythm of the heart‘s actions ensures the heart’s efficiency. A “heartbeat” actually consists of two contractions in quick succession (contraction of the heart muscle), that of the atrium and the subsequent contraction of the ventricle.

A cardiac dysrhythmia can therefore basically be classified according to two criteria: There are many other ways of classifying cardiac dysrhythmia in particular, but some of them are very complicated, as they require a great deal of basic knowledge of physiology (function of the organ systems). The classification chosen here is one of the most common in everyday clinical practice. What makes the heart beat?

The special feature of the heart is its own generation of electrical stimuli, which cause the muscle cells to contract (contract). A distinction is made between the actual working musculature and the stimulus conduction or stimulus formation system. Different areas of the heart therefore have cells that can independently generate electrical potentials.

These potentials are then conducted through the conduction system to the actual working muscles. It converts the electrical stimuli into a contraction. The sinus node, the AV node and subordinate excitation centers belong to the stimulation system.

The sinus node can best be imagined as the large clock generator. In healthy people, the frequency of the sinus node determines how often the heart beats per minute (approx. 60-90 times).

Its beat is passed on by the conduction system to the other stimulation centers, which then adjust their frequency, this is called sinus rhythm. If the sinus node fails, however, the other excitation formation centers can partially take over its task. The sinus node is located in the right atrial musculature, its stimuli are directly transmitted to the working muscles of the atria and passed on to the AV node.

It is also the instance that permanently adapts the heart rate to the requirements of the organism, e.g. it accelerates the heartbeat during sports activities and slows it down during sleep. The AV node is located in the musculature between the atria and the ventricles; it transmits the sinus impulses to the His bundle with a delay. However, if the sinus node fails or the stimulus conduction is blocked, it can also become a clock generator itself.

However, at 40-50 beats per minute, its frequency is significantly lower than that of the sinus node. The stimulation conduction system connects the sinus node and the AV node and leads from there to the working muscles of the chambers.After the AV knot is the so-called His bundle, which is divided into a right and left tawara leg according to the discoverer. These finally conduct the electrical stimuli to the Purkinje fibers, which end in the heart muscle layer of the chambers. This results in a further classification possibility for the cardiac arrhythmias:

  • Place of origin = where the disorder originates, in the atrium or chamber
  • Type of rhythm change = the heart beats faster (tachycardia) or slower (bradycardia)
  • Irritation disorder (here the problem lies in the sinus or AV node) or
  • Irritation line disturbance (here the problem lies in the transmission of the impulses)