Ectopic Complexes

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Ectopic beats

The pacemakercells in the sinusnode are not the only cells in the heart that can depolarize spontaneously. Actually all cardiomyoctyes have this capacity. The only reason why the sinusnode 'rules' is that it is the fastest pacemaker of the heart. From sinusnode to ventricle all healthy cardiomyocytes can function as a ectopic pacemaker. Ectopic pacemaker activity can originate from the atria (60-80 bpm), AV-node (40-60 bpm) and the ventricles (20-40 bpm). So, as the sinus rate drops (e.g. during atrial infarction), other cells can take over. The configuration of ectopic beats or extrasystoles, as seen on the ECG, reveals its origin, whether they are atrial, nodal or ventrical.

Ectopic pacemakers

  • Atrial ectopic pacemaker: frequency 50-60bpm
  • Nodal ectopic pacemaker frequency 50bpm
  • Ventricular ectopic pacemaker frequency 30-40bpm

Atrial rhythm

Atrial Rhythm
Atrial rate 50-100 bpm
Ventricular rate 1:1
Regularity regular
Origin atrial
P-wave present, but different from sinus rhythm
Effect of adenosine slows down
Example ECG: Atrial rhythm. In this example the sinus node stopped pacing due to ischemia during an atrial infarction. The p-wave is positive in I, negative in III and AVF. The atrial pacemaker is thus situated at the bottom of the right atrium, close to the AV node.
Example ECG2: {{{example2}}}

Atrial rhythm resembles sinusrhythm, but origins from a different atrial focus. It can be recognised by the abnormal configuration of the p-wave. Often the p-wave is negative in AVF, as is seen in the example.

Wandering Pacemaker

Wandering pacemaker. Every p-wave is different and thus has a different origin.

When several pacemakers are competing, p-waves with different origins and thus configurations occur. The rhythm is slightly different from beat to beat.

note If the heart rate increases to above 100bpm, it is called Multifocal Atrial Tachycardia. Possible causes are hypoxia, COPD and medication such as digoxin.

Premature atrial complex / atrial extrasystole

A premature atrial complex (PAC). (In this example the atrial p-wave is difficult to discern).
A premature atrial complex (PAC) with evident negative p-wave

Premature atrial complexes origin from an ectopic pacing region in the atria. The result is a p-wave with often a different morphology as the preceding ones.

AV-nodal complexes

Originate from the AV node. The AV node fires before the sinusnode. The ECG shows a QRS complex with a comparable morphology as during sinus rhythm as these extra beats are conducted further through the normal conduction system. When the extra follows very soon after the earlier one, aberrant conduction can occur. The extra beat does not have a p-wave in front of it. Sometimes an inverted p-wave can be seen in or at the end of the QRS complex.

Ventricular premature beat (VPB) / Ventricular extrasystole (VES)

The arrow indicates a ventricular extrasystole (VES).

A VPB is an ectopic beat that origins from the ventricles. VPBs are hardly conducted by the specialised conduction system and therefore are broad. The QRS width is at least > 0.12 seconds, but often very broad at around 0.16-0.20 seconds.

Causes: e.g. ischemia, hypoxia, old scar tissue, idiopathic. 50% of healthy men have sporadic VPBs. The origin of the VPB can be derived from its form. A LBTB-configured VPB originates in the right ventricle. A RBTB-configured VPB comes from the left ventricle. The QRS duration of a VPB is > 0.12 seconds and can be as wide as 0.16-0.20 seconds.

A sequence of three or more extrasystoles is called a non-sustained ventricular tachycardia.

If more than one VPB is present on the ECG, they can be:

  • monomorphic: all VPBs have the same configuration and thus have a mutual focus of origin.
  • multiformic: the complexes have different configurations.


Bigemini: every sinus beat is followed by a ventricular extrasystole

Every sinus beat is followed by a ventricular extrasystole.


Every second sinus beat is follow by a ventricular extrasystole.