Section 2 Ventricular rhythms

Ventricular premature beat (VPB)

Ventricular bigeminy

Accelerated idioventricular rhythm

Ventricular tachycardia – atrioventricular dissociation

Ventricular tachycardia – capture and fusion beats

Ventricular tachycardia – morphology of VPB

Ventricular tachycardia – myocardial infarction

Polymorphic ventricular tachycardia

Polymorphic ventricular tachycardia – ‘torsade de pointes’

Ventricular flutter

Ventricular fibrillation (VF)

Case 24 A 64-year-old man with irregular thumping sensations in the chest

Ventricular premature beat (VPB)

• An abnormally wide beat occurring earlier than expected.

• There is no preceding P wave; AV dissociation is present.

• The premature beat is followed by a full compensatory pause, i.e. the R-R interval between the beats directly preceding and following the VPB is exactly twice that of the regular R-R interval.

P waves may often be identified in the T wave following a VPB, either as a result of retrograde conduction (P wave early and negative), or as dissociated sinus events (same P-P interval and morphology as the usual P wave).

When VPBs have different morphologies they are called multifocal.

Features of this ECG

• Sinus tachycardia, rate 105 b.p.m., normal QRS axis

• Ventricular premature beats (Fig. 24.1):

– occur earlier than expected, no preceding P wave

– abnormal shape, wider than sinus beats

– followed by a full compensatory pause

• Abnormal Q waves in leads II, III, aVF suggesting an old inferior myocardial infarction

• Poor R wave progression in the anterior chest leads, consistent with an old anterior infarction

Fig. 24.1 Rhythm strip.

Clinical Note

It is the normal beat following a VPB that is the more forceful and may cause a thumping sensation, not the VPB itself.

Common causes of ventricular premature beats

→ Occur in normal individuals

→ Ischaemic heart disease

→ Digoxin toxicity

→ Left ventricular dysfunction

Case 25 A 73-year-old lady with diabetes

Ventricular bigeminy

• Each sinus beat is followed by a ventricular premature beat.

• The coupling interval is usually constant.

P waves may often be identified in the T wave of the ventricular ectopic beat, either as a result of retrograde conduction, or as dissociated sinus events.

Features of this ECG

• Sinus rhythm with ventricular bigeminy

• Atrial rate, 60 b.p.m. (every second P wave buried in the T wave of a VPB)

• Mean ventricular rate 60 b.p.m., normal QRS axis

• Ventricular bigeminy (Fig. 25.1):

– each sinus beat is followed by a ventricular premature beat (VPB)

• Non-specific intraventricular conduction delay:

– there is notching of the QRS complex in the sinus beats

• An artifact is present in leads II and III (Fig. 25.2):

– such high frequency spikes should not be confused with pacing impulses

Fig. 25.1 Rhythm strip.

Fig. 25.2 Artifact.

Common causes of ventricular bigeminy

→ May occur in normal individuals

→ Ischaemic heart disease

→ Digoxin toxicity

→ Left ventricular dysfunction

Case 26 A 78-year-old man 2 days following an episode of prolonged chest pain

Accelerated idioventricular rhythm

• Wide complex regular rhythm, 60-100 b.p.m. (faster than sinus rate).

• Usually seen in association with an acute MI.

• It is thought to be a reperfusion arrhythmia.

P waves may often be identified in the T wave, either as a result of retrograde conduction, or as dissociated sinus events.

Features of this ECG

• Sinus rhythm, 60 b.p.m., normal QRS axis

• Accelerated idioventricular rhythm starts in the rhythm strip (Fig. 26.1):

– wide complex, regular rhythm, 70 b.p.m.

– P waves buried in the T wave (Fig. 26.1)

• Recent inferolateral myocardial infarction (Fig. 26.2):

– abnormal q waves

– ST elevation in leads II, III, aVF and V3-6

• A ventricular premature beat is recorded in leads V4-6

Fig. 26.1 Accelerated idioventricular rhythm.

Fig. 26.2 Recent myocardial infarction.

Electrical origin of ventricular rhythms

→ Enhanced automaticity:

– AIVR (shown here)

– ventricular premature beats

→ Re-entry circuits:

– ventricular tachycardia

– ventricular flutter

– ventricular fibrillation

Case 27 A 55-year-old man, 2 weeks after a myocardial infarction, BP 130/80

Ventricular tachycardia – atrioventricular dissociation

A wide complex tachycardia is VT until proven otherwise and no diagnostic algorithm can reliably differentiate all wide complex tachycardias.¹

No diagnostic criteria can differentiate all wide complex tachycardias.

• Factors favouring ventricular tachycardia:

– AV dissociation, fusion beats, capture beats

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