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• A characteristic VPB is not preceded by a premature P waves and is represented by a wide and bizzare QRS complex. It is followed by a compensatory pause because of its inability to conduct retrogradely through the AV node to reset SA node.

Exceptions

• A VPB, may be preceded by a premature P wave if both an APB & VPB are present.

• When marked sinus arrythmia is present ; it cannot be determined whether or not a pause is compensatory.

• VPB typically is >0.12 sec , but may appear to have a normal duration in any single lead because its initial or terminal component is isoelectric.

Etiology

• Stress, caffeine, sympathomimetic drugs

• Electrolyte abnormality esp. hypokalemia or hypomagnesemia

• Drug toxicity like digoxin

• MI

Bigeminy

• A bigeminal pattern occurs with every normal beat followed by a VPB and with constant coupling intervals between each pair of normal sinus and VPB.

Clinical significance of Ventricular Ectopic

• Ventricular extrasytoles in the presence of transient myocardial ischemia, left ventricular dysfunction and cardiomegaly may trigger runs of ventricular tachycardia that may degenerate into pulseless tachycardia and ventricular fibrillation.

Right versus Left Ventricular Premature Beats

• If VPB in lead V1 is predominantly positive , the impulse originates from left ventricle (impulse travels anteriorly and rightwards froms its origin in the posteriorly located left ventricle).

• If VPB in lead V1 is predominantly negative, the impulse originates from right ventricle.

• Morphology of left VPB (Resembles RBBB)

  • Usually a monophasic (R )or diphasic (qR) complex in lead V1 and diphasic (rS) or monophasic (QS) complex in lead V6.

  • First peak has greater amplitude (Rabbit ear Pattern).

     

• Morphology of right VPB (Resembles LBBB)

  • Positive morphology in lead V6 but a right axis deviation in the frontal plane and a wide initial R wave in lead V1.

  • A deeper rS or qS complex in lead V4 than in lead V1.

Clinical importance of Right v/s Left VPB

• Left VPB are more often associated with heart disease, whereas right VPB are commonly seen in individuals with normal hearts.

• Left VPB are more likely than right VPBs to precipitate VF.

What is R on T phenomenon ?

• When VPB occurs early that they interrupt the peak of the preceding T wave they may be considered dangerous.

• The impulse may repetitively reenter, thereby producing a tachyaarhythmia ; which may terminate spontaneously or progress to typical VF.

• Studies have shown that R on T - VPB's pose a risk of inducing VF only in early stages of MI, in hypokalemia and in presence of QT interval.

BenignVPB

• Benign VPB may be seen in healthy individuals.

• They commonly disappear when sinus rate increases such as during excersie.

• VPB's increasing during exercise is concerning and requires further evaluation.

• There is increased risk as the numerical grade advances from 0 to 5.

What is multifocal VPB'S?

• VPB's originating from two or more different ventricular locations.

What is multiform VPB's ?

• VPB's with two or more different morphologies in a single ECG lead.

Management

• ECHO, Holter monitoring

• Stop the offending agents

• Correct electrolyte

• Symptomatic patient may be treated with Beta blocker.

Updated on 10/8/2014

Reference

• Marriot's Practical Echocardiography

• Goldberge