Arrhythmias are usually divided into those that occur in the ventricles and those that occur in the atrium, above the ventricles, also called “supra-ventricular”.
The major supra-ventricular arrhythmias are:
The major ventricular arrhythmias are:
There are a few arrhythmias that do not fit into one of these two groups. The most famous one is the WPW syndrome (=Wolf-Parkinson-White).
Also the duration of the arrhythmia is important.
6. There are three types:
paroxysmal: lasts for seconds to a few hours
persistent: lasts for days to weeks
chronic: lasts months to years.
Atrial extra-systole is when an “extra” beat occurs. In other words, an extra beat is “inserted” between the regular beats.
Because the origin of this extra-systole could occur anywhere in the atria, right or left, the P wave and the PQ-interval may be different from the normal P wave.
In this example, the focus was located in the left atrium. Therefore the major direction of propagation is now opposite from the normal direction; hence the P-wave becomes opposite to the normal polarity (i.e. negative).
If the circuit is located high in the AV-node, then the PQ-time will be very short or the P-wave may even be hidden in the QRS complex (top tracing in the figure).
If, however, the circuit is located low in the AV-node and close to the bundle of His, then propagation back to the atria will take a long time and the P-wave will occur well after the QRS complex (bottom tracing in the figure).
In atrial fibrillation, there are multiple re-entrant propagations simultaneously present, in the right and in the left atrium.
Therefore, some parts of the atria are constantly excited while others are recovering. All these excited and recovering areas shift all the time throughout the muscle.
As there is no longer one single propagating impulse, but many impulses, there is no longer a significant signal on the ECG and therefore no P wave.