ECG with extrasystole of the heart
The terms “ectopic complex”, “extrasystole” and “premature contraction” are synonymous from a practical point of view. They denote the premature impulse that occurs during the cardiac cycle in the atria, the AV connection, or the ventricles.
Atrial ectopic impulse is usually conducted to the ventricles through the AV-junction and along the legs of the bundle of His in the usual way, as a result of which a narrow QRS complex is formed. With a certain degree of prematurity of the atrial ectopic impulse, the P wave may overlap the T wave of the preceding complex.
Ventricular ectopic impulse is not carried out through the ventricles through the His-Purkinye fast-conducting system. As a result, the forming complexes are wide (> 0.12 s) and have an odd shape, and the P wave does not precede them. Ventricular premature beats are often idiopathic, but if it is caused by heart disease, this is associated with an increased risk of cardiovascular death, which does not decrease when antiarrhythmic drugs are prescribed.
By definition, an extrasystole should occur earlier than the next complex in the cardiac cycle is expected. Thus, the interval between the ectopic and anterior complex, i.e. adhesion interval, always shorter than the length of the cycle of the main rhythm. If this fact is ignored, then other complexes of a modified configuration, such as slipping complexes and complexes with an intermittent blockade of the bundle of the bundle of His, can be mistakenly interpreted as an extrasystole.
The location of the source of beats can be established by careful analysis of the ECG. ECG recordings in one lead are not enough for this. Identification of diagnostically important signs requires careful consideration of ECG recordings performed simultaneously in several leads.