Introduction
Atrial fibrillation is a very common cardiac arrhythmia associated with an uncoordinated electrical conduction function in the atria. Fibrillation describes the often non-functional and clearly too fast contractions (= contraction) of the atria. Therefore, atrial fibrillation is also called tachycardic (too fast) cardiac arrhythmia. In almost all cases, atrial fibrillation can be visualized on an ECG. Especially the P-wave, which is produced by a targeted and coordinated conduction of stimuli in the atria, is altered by atrial fibrillation.
Can atrial fibrillation be seen in the ECG?
Atrial fibrillation occurs when there is no directional stimulus conduction in the atria. Normally, electrical excitation is generated in the sinus node. This node is located in the right atrium.
From there the excitation is conducted to the AV node. AV node stands for atrioventricular node. This node is located, as the name suggests, between the atria and the ventricles and transmits the electrical excitation to the ventricles.
In atrial fibrillation, this conduction is disturbed in the atrium. This results in uncoordinated and non-targeted electrical stimulation conduction. Therefore, no P-wave can be detected in the ECG.
In most cases, this is replaced by so-called flicker waves, which are differently pronounced in the different ECG recordings. The AV node has a watchdog function for the ventricles during the transmission of stimuli. If it receives uncoordinated electrical stimuli (as is the case with atrial fibrillation), it does not transmit this excitation to the ventricles.
Instead, the AV node can step in as a second pacemaker and generate its own pulse for the ventricles only. Normally, the resulting heart rate is somewhat slower, which is reflected in the ECG by a greater distance between the R-spikes. It is extremely rare that atrial fibrillation cannot be shown in the ECG.
What does absolute arrhythmia look like in an ECG?
An absolute arrhythmia (also called “Tachyarrhythmia absoluta”) is an uncoordinated, clearly too fast contraction of the atria and ventricles. The reason is a disturbed conduction of stimuli in the atria together with a disturbed transfer of electrical excitation into the ventricles. The uncoordinated and disturbed function of the atria is characterized by the fact that there is no directional stimulus conduction in the atria.
Therefore, no P-wave can be found in the ECG. In most cases, this is replaced by so-called flicker waves, which are visible between the individual R-waves (contraction of the ventricles). Although the ventricles contract, they do so very irregularly, which is why the R-waves appear at irregular intervals in the ECG. If the stimulus conduction in the heart chambers functions in a targeted manner, almost normal QRS complexes can be detected, but they do not appear regularly. An uncoordinated stimulus conduction of the chambers leads to so-called ventricular fibrillation and is characterized by deformed QRS complexes.
