Atrial fibrillation is characterized by a disturbance in the rhythm of cardiac activity caused by an increase in the excitability of the myocardium of the atria and a decrease in the conductivity of impulses through the conduction system. These changes are observed with stretching of the walls of the atria and the resulting dystrophic changes in the myocardium, which occurs with stenosis (narrowing) of the left venous opening, atherosclerotic cardiosclerosis, myocardial infarction, thyrotoxicosis.
Many impulses occur in different parts of the atrial muscle, which are not transmitted at a distance, fade out in place, giving only individual contractions of muscle fibrils in the form of flickers.
Only individual pulses reach the Ashof-Tavar node and cause irregular contractions of the ventricles of the heart.
There are three forms of atrial fibrillation:
- atrial flutter with the number of pulses occurring in the atrial muscle up to 350 in minute;
- atrial fibrillation with the number of pulses from 300 to 600 per minute;
- paroxysmal form of atrial fibrillation.
During atrial flutter, the pulses rhythmically reach the Ashof-Tavar node, however, not all of them reach the ventricles and, therefore, do not cause their contractions, since the atrioventricular node allows no more than 180 to pass to the ventricles -200 pulses per minute.
With atrial fibrillation, when the number of atrial pulses reaches 600, there are no full-fledged contractions of the atria, only individual fibrils are reduced, and only some contractions that are irregular in size reach the ventricles, in this regard daughters contract arrhythmically.
In terms of the number of heart contractions, atrial fibrillation occurs:
- bradysystolic, with the number of contractions up to 80 per minute;
- tachysystolic, with the number heart contractions of more than 100 per minute.
A paroxysmal form of atrial fibrillation is observed in disorders of the nervous system and occurs periodically in the form of attacks of paroxysmal tachycardia, which soon passes.
When established atrial fibrillation can not be guided by the number of heart contractions, so ka some impulses that occurred at the beginning of diastole cause a so weak heart contraction that the lunate valves do not open and blood does not enter the aorta. In these cases, when calculating the contractions of the heart and pulse, you can make sure that their numbers do not match, that is, there is a pulse defect. A decrease in pulse deficiency indicates an improvement in the patient’s condition and vice versa.
Atrial fibrillation is not a reason to self-medicate. This disease requires constant monitoring by a therapist and cardiologist.