Diagnostic criteria

  Depolarization of the ventricles occurs by an impulse originating from an ectopic ventricular focus.

  There is no causally related preceding P wave since the impulse originates from the ventricles.

  Since the impulse originates from an ectopic ventricular focus, depolarization wave does not propagate over fast Purkinje fibers but by cardiac myocytes which results in slow conduction and hence a wide QRS complex (>120ms).



Compensatory Pause

  Definition: The sum of the pre-VPC and the post-VPC intervals equals to 2 times of the interval between two sinus beats.

  For a full compensatory pause to occur, there are 2 necessities:

1. There must be a stable sinus rhythm. Sinus arrhythmia must not be seen.

2. There must be ventriculoatrial block (the VPC must not interrupt the sinus rhythmicity) or ventriculoatrial conduction occurs but fails to reset the sinus node.

  Rarely a VPC may not have a compensatory pause.

  During sinus rhythm, compensatory pause after a VPC is NOT seen

      1. IF there is sinus arrhythmia.

      2. IF there is ventriculoatrial conduction resetting the sinus node.

  Compensatory pause is not possible in irregularly irregular rhythms such as atrial fibrillation or multifocal atrial tachycardia.

  By definition, interpolated VPCs also do not have compensatory pauses.

  After a VPC, a compensatory pause is usually observed. Usually, compensatory pause is not observed after an atrial premature beat (APB). Compensatory pause after an APB is very rare. Compensatory pause after an APB suggests that the APB failed to reset the sinus node.

  When a VPC occurs during aberration due to increased heart rate (acceleration-dependent aberration), its compensatory pause may result in temporary disappearance of the aberration.



Clinical significance

  Observation of VPS in a subject without organic heart disease is not significant.

  VPS is the most common type of arrhythmia.

  VPS is not specific for a certain disease.

  Not all wide QRS complexes are due to VPC:

- Ventricular pacemeker stimulation results in wide QRS (His bundle pacing is an exception).

- Aberrant conduction of a supraventricular impulse to the ventricles (aberrancy) causes wide QRS.

- WPW syndrome causes wide QRS complexes.

  Sometimes, artifacts may look like VPCs.



Click on the links below to see various types of VPCs:

Bidirectional VPC

End-diastolic VPC

Interpolated VPC

Interpolated ventricular couplet

R-on-T VPC

Rule of bigeminy

VPC-like artifact




ECG 1. A VPC during stable sinus rhythm usually shows compensatory pause.
Interval between a VPC and its preceding sinus beat is called coupling interval.
The RR interval that contains the VPC (coupling interval + compensatory pause) is exactly twice the duration of
the RR interval of the adjacent sinus complex.
X + Y = Z




ECG 2. For a compensatory pause to occur during stable sinus rhythm,
the sinus rhythmicity must not be interrupted by the VPC.




ECG 3. Do not expect to see compensatory pause after a VPC during atrial fibrillation.
Above is an ECG from a 63 years-old man with left heart failure and atrial fibrillation.

Click here for a more detailed ECG




ECG 4. Compensatory pause after an atrial premature beat is seen very rarely.
Failure to reset the sinus node results in a compensatory pause.

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ECG 5. In the presence of sinus arrhythmia, VPCs do not show compensatory pause.
Above ECG is from a 35 years-old woman with normal ECHOcardiogram.

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ECG 6. The above ECG belongs to a 65 years-old man with a normal ECHOcardiogram (no structural heart disease).
Fully interpolated VPC is seen. By definition, an interpolated VPC does not have compensatory pause.

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ECG 7. The above ECG is from a 67 years-old woman with gastric cancer.
Sinus tachycardia (138/min.) and an atrial premature beat is seen. This atrial premature beat has a compensatory pause.
Failure to reset the sinus node results in a compensatory pause.
Compensatory pause is seen very rarely after an atrial premature beat.
The P wave of the atrial premature beat is deforming the preceding T wave.

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ECG 8. Ventricular couplet and compensatory pause from a 3-channel Holter recording.




ECG 9a. The ECG above belongs to a middle-aged woman. She was diagnosed as normal coronary arteries and dilated
cardiomyopathy. The basic rhythm is sinus rhythm with aberrant conduction as left bundle branch block (LBBB) .
The Ventricular Premature Systole (VPS) is followed by compensatory pause. As the instantaneous heart rate during the
compensatory pause was slow enough, aberration disappeared and the sinus beat was conducted normally to the ventricles as
a narrow QRS complex.

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ECG 9b. The ECG was recorded again. VPS was observed among sinus beats conducted with LBBB type aberration .
When heart rate was slow enough during the compensatory pause, the aberration disappeared and the sinus beat was normally
conducted to the ventricles as a narrow QRS complex .

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ECG 9c. The 3-lead Holter recording of the same patient showed VPS and normal conduction of the sinus beat following the
compensatory pause. This Holter recording showed that the normal conduction (without aberration) was related to the
instantaneous heart rate . When the instantaneous heart rate was 69/minute or below the aberration disappeared and
the sinus beat was conducted normally to the ventricles.

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ECG 9d. Another instance from the 3-lead Holter recording of the same patient shows how important the instantaneous
heart rate is for aberration. When instantaneous heart rate is 69/minute or below the sinus beat following the compensatory
pause of the VPS is conducted normally (without aberration) . When instantaneous heart rate is above 69/minute aberration
reappears.

Click here for a more detailed ECG