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Premature Ventricular Complex

Premature ventricular complex (PVC), Ventricular premature beat (VPB), Ventricular extrasystole (VES), Premature ventricular contraction, Ventricular premature depolarisation, Ventricular ectopic

Premature Ventricular Complex (PVC)

• Most commonly occurs during sinus rhythm
• Arises from an ectopic ventricular focus
• which depolarizes prematurely electrically
• Impulse activates the ventricles (Wide QRS complex)
• May retrogradely activate the atria
• Leads to asynchrony between the atria and ventricles
• Atria are activated from the SA node
• Ventricles are activated from the ventricular focus
• PVCs commonly occur with:
• Stress, coffee, alcohol, smoking, etc., approximately 10 times/hour
• PVCs are usually benign and do not require treatment
• More frequent in a structurally changed heart
  
  
• PVCs may trigger re-entry tachycardia:
• AVNRT (AV nodal re-entry tachycardia)
• AVRT (Atrioventricular re-entry tachycardia)
• Ventricular tachycardia
• Torsades de Pointes
  
  
• We recognize 3 types of extrasystoles:
• Supraventricular:
• Atrial extrasystole
• Junctional extrasystole
• Ventricular extrasystole

Discordance

Discordance and Ventricular Extrasystole

• Two leads are visible on the ECG (aVL, V2)
• Wide QRS (>0.12s)
• Ventricular Triplet
• 3 consecutive ventricular extrasystoles
• Discordance
• Opposite polarity between (QRS) and (ST-T segment)

Full Compensatory Pause and Ventricular Extrasystole

• The RR interval with extrasystole is exactly 2 times the RR interval without extrasystole
• With extrasystole, a full compensatory pause is more common than an incomplete pause

Incomplete Compensatory Pause and Ventricular Extrasystole

• The RR interval with VES is shorter than twice the RR interval without VES
• Retrograde (P´) P wave
• Incomplete compensatory pause occurs when the SA node is reset, especially in:
• Atrial extrasystole
• Junctional extrasystole
• With VES, it is rare because VES rarely retrogradely resets the SA node

Interpolated VES

Interpolated Ventricular Extrasystole

• (1) Interpolated Ventricular Extrasystole
• Occurs during sinus rhythm, most commonly with sinus bradycardia
• Is embedded between 2 sinus beats
• Sometimes referred to as a sandwich extrasystole
• Does not have a compensatory pause
• PQ (PR) interval after the interpolated VES is prolonged
• Because concealed conduction occurred in the AV node
• (2) Classic Ventricular Extrasystole
• Complete compensatory pause (SA node was not reset)
• Concealed Conduction
• Occurs with interpolated VES during sinus rhythm (bradycardia)
• VES does not cause retrograde activation of the atria
• Retrograde impulse only partially penetrates the AV node (not visible on ECG)
• Retrograde penetration of the AV node has altered electrical conduction such that:
• subsequent impulse (from the SA node) is conducted more slowly
• On the ECG, we see a prolonged PQ interval after the interpolated VES
• Concealed conduction occurs only with specific timing of VES
• which often occurs with interpolated extrasystole

End-Diastolic PVC

End-Diastolic PVC

• Occurs at the end of diastole
• After the P wave, just before the expected sinus QRS complex
• Has a complete compensatory pause
• Because the SA node is not retrogradely reset
• Shortened PQ interval
• VES follows immediately after the P wave
• Note that the P wave (sinus impulse) does not activate the ventricles
• The ventricles are activated by the ventricular extrasystole
• Impulse from VES and SA node meet and reset in the AV node
• Atria are fully activated from the SA node
• Ventricles are fully activated from the VES
  
  
• Fusion Beat
• Impulse from the SA node and VES meet in the ventricles (not in the AV node as in end-diastolic VES)
• Ventricles are activated by 2 impulses
• Most commonly occurs in ventricular tachycardia

R-on-T Phenomenon

• R-on-T Phenomenon
• It is a PVC occurring on the T wave
  
  
• Vulnerable Period
• This is the final phase of the action potential repolarization
• On the ECG, it appears as a T wave
• It extends with the QT interval
  
  
• The R-on-T phenomenon represents a risk
• During acute myocardial infarction
• In cases of extreme hypokalemia
• With prolonged QT interval
  
  
• 1/3 of ventricular tachycardias are triggered by the R-on-T Phenomenon:
• Ventricular fibrillation
• Torsades de Pointes

Localization of Ventricular Extrasystole

• One ECG lead is sufficient for diagnosing PVC
• According to the 12-lead ECG, the ectopic focus in the ventricles that generated the PVC can be localized
• Which has generated the ventricular extrasystole
• Using chest (V1-V6) and inferior leads (II, III, aVF), the focus can be localized into 4 quadrants
  
  
• A simple algorithm is used for localization
• 1. First, assess the chest leads
• 2. Then assess the inferior leads

• According to the chest leads, the focus is localized in the left or right ventricle
• Right bundle branch block pattern -> The focus is in the left ventricle
• Left bundle branch block pattern -> The focus is in the right ventricle

• Localizes the focus to the apex or base of the heart
• Positive QRS (II, III, aVF) -> The focus is at the base of the heart
• Negative QRS (II, III, aVF) -> The focus is at the apex of the heart

Unifocal Premature Ventricular Complex

• Based on the number of ectopic foci that generate PVCs, PVCs are classified as:
• Unifocal premature ventricular complex (PVC)
• 1 ectopic ventricular focus
• Multifocal premature ventricular complex (PVC)
• At least 2 ectopic ventricular foci

Unifocal PVC

• There is one ectopic focus in the ventricles
• which intermittently generates impulses
• It always has the same morphology
• Because each PVC originates from the same focus (has the same ventricular vector)
• It has the same coupling interval
• It is the distance in ms between the PVC and the preceding QRS complex

Ventricular Extrasystoles by Repetition

• Based on repetition, PVCs are classified as:
• Bigeminy
• Trigeminy
• Quadrigeminy
• Couplet
• Triplet (Salvo)

Trigeminy

• Every third beat is a ventricular extrasystole
• On the ECG, there are 3 trigeminically linked ventricular extrasystoles

Couplet

• Ventricular extrasystoles occur in pairs (2 extrasystoles together)
• Multifocal couplet
• The first couplet and the second couplet have different shapes
• Because they originate from different ectopic foci
• The first couplet is a fusion beat (ventricles are activated from both the SA node and the extrasystole)
• It mainly occurs in ventricular tachycardia

Ventricular Tachycardia

• Ventricular tachycardia is defined as a sequence of at least 4 consecutive ventricular extrasystoles (VES):
• Non-sustained ventricular tachycardia (lasting < 30 seconds)
• Sustained ventricular tachycardia (lasting > 30 seconds)

Non-Sustained Ventricular Tachycardia

• Non-sustained ventricular tachycardia
• Consists of at least 4 consecutive VES
• Terminates spontaneously within 30 seconds
• On ECG, 11 VES that terminate within 30 seconds indicate non-sustained ventricular tachycardia
• If it lasts more than 30 seconds, it is classified as sustained ventricular tachycardia

Lown Classification of PVCs

• The classification (Lown's Grading of PVCs) was developed for patients with acute coronary syndrome
• Therefore, its prognostic significance in other patient groups is inconclusive
• However, it provides information on the frequency of PVCs in the patient