Atrial fibrillation

Atrial fibrillation

Atrial fibrillation (AF) is the most common arrhythmia. Indeed, due to the increase in life expectancy in the population as a whole, and among patients with heart disease, its prevalence is constantly increasing.

It is important to know the various causes and clinical manifestations of arrhythmia and to understand that the tactics of treatment should be individualized depending on the etiology associated with the risk of arrhythmia and the symptoms present.

When atrial fibrillation (AF), the atria are activated with a frequency of 350 to 600 imp./min. Arrhythmia is caused by the existence of numerous excitation waves circulating in random directions within the atrial myocardium. A very high frequency of electrical activity leads to the loss of effective mechanical atrial systole.

1) Atrial activity in atrial fibrillation. High-frequency and chaotic electrical activity of the atria during AF leads to the appearance of very frequent, low-amplitude and irregular waves f. The amplitude of these waves varies in different patients and in different ECG leads: in some leads, the f waves may be imperceptible, whereas in other leads (especially in lead V1) they can be so pronounced that it is possible to assume the presence of TP, although atrial activity has more high frequency, than it usually happens when trembling. Teeth P, of course, absent.

2) Atrioventricular conduction during atrial fibrillation. Fortunately, the AV-node is not able to conduct all the atrial impulses on the ventricles: if this were possible, the VF would develop as a result! Some impulses are completely blocked, others only partially penetrate the AV node and therefore do not excite the ventricles, but can block or delay the passage of subsequent impulses. This process of “latent holding” is responsible for the irregular rhythm of the ventricles, which is the hallmark of this arrhythmia.

The absence of P-waves (even in the absence of noticeable f waves) and an irregular ventricular rhythm indicate the presence of AF. AF with a high frequency of ventricular contractions is often not diagnosed. Errors can be avoided by remembering that an irregularity of ventricular rhythm is a characteristic feature of arrhythmia. However, if against the background of AF, complete AV block develops, then the ventricular rhythm, of course, becomes slow and regular. The frequency of ventricular contractions in AF depends on the conductive ability of the AV node, which, in turn, is affected by the autonomic nervous system.