Sandbox/07

Criteria and Definitions of Ventricular Rhythms

1. Ventricular premature complex, uniform, fixed coupling
2. Ventricular premature complex, uniform, nonfixed coupling
3. Ventricular premature complex, multiform
4. Ventricular premature complexes, in pairs (2 consecutive)
5. Ventricular parasystole
6. Ventricular tachycardia (≥3 consecutive beats)
7. Accelerated idioventricular rhythm
8. Ventricular escape complexes or rhythm
9. Ventricular fibrillation

Ventricular premature complex, uniform, fixed coupling

All of the folowing are required:

■ Premature in relation to normal cycles, not preceded by P wave (or shorter than expected PR interval or “collapsing PR”)
■ Coupling interval usually the same for each site or focus (variation usually <0.08 second)
■ Abnormal QRS configuration that is almost always >0.12 second in duration
■ Retrograde capture of atria may occur
■ Initial direction of QRS complex is often different from that observed during sinus rhythm
■ Usually full compensatory pause is noted
■ Compensatory pause requires an undisturbed sinus depolarization due to one of the following:

- Ventriculoatrial block

- Sinoatrial entrance block if atrial capture occurs

- Sinoatrial node discharged before arrival of retrograde wavefront, and thus refractory

Ventricular premature complex, uniform, nonfixed coupling

■ Ventricular premature complexes with variable temporal relationship to regular sinus beats

Ventricular premature complex, multiform

■ Two or more morphologic patterns of ventricular premature complexes present

Ventricular premature complexes, in pairs (2 consecutive)

Two consecutive ventricular premature complexes of not necessarily the same morphology

All of the folowing are required:

■ Premature in relation to normal cycles, not preceded by P wave (or shorter than expected PR interval or “collapsing PR”)
■ Coupling interval usually the same for each site or focus (variation usually <0.08 second)
■ Abnormal QRS configuration that is almost always >0.12 second in duration
■ Retrograde capture of atria may occur
■ Initial direction of QRS complex is often different from that observed during sinus rhythm
■ Usually full compensatory pause is noted
■ Compensatory pause requires an undisturbed sinus depolarization due to one of the following:

- Ventriculoatrial block

- Sinoatrial entrance block if atrial capture occurs

- Sinoatrial node discharged before arrival of retrograde wavefront, and thus refractory

Ventricular parasystole

An automatic ventricular focus with entrance block and all of the following:

■ Rates usually 30-56 beats/min
■ Varying relationship with the preceding sinus beats
■ All interectopic intervals are a multiple of a constant shortest interval
■ When fusion beats and lack of fixed coupling are noted, consider parasystole

Ventricular tachycardia (≥3 consecutive beats)

Rapid succession of ≥3 beats of ventricular origin

■ Abnormal and wide QRS complexes with secondary ST-T changes (ventricular tachycardia originating in the septum near the normal conduction system may have a narrow QRS complex)
■ Rate >100 beats/min
■ Regular or slightly irregular
■ Abrupt onset and termination
■ AV dissociation is common. On occasion, retrograde conduction and capture of the atria may occur
■ Look for ventricular capture and fusion beats as a marker for ventricular tachycardia

Ventricular origin

■ QRS complexes like those of ventricular premature complexes
■ Tachyarrhythmia initiated by ventricular premature complexes
■ AV dissociation
■ Capture or fusion beats
■ QRS ≥0.14 second if RBBB morphology and ≥0.16 second if LBBB morphology when QRS during sinus rhythm <0.12 second
■ Left or northwest axis deviation
■ All positive or all negative complexes in precordial leads
■ In V1, R > r′ (left rabbit ear taller than right)

Supraventricular origin

■ QRS complex like aberrantly conducted atrial premature complexes or QRS in sinus rhythm
■ Tachyarrhythmia initiated by atrial premature complexes
■ RBBB configuration with rSR′ in V1

Accelerated idioventricular rhythm

Requires all of the following:
■ Regular rhythm, rate 60-110 beats/min
■ QRS complexes are abnormal and wide
■ Usually AV dissociation
■ Capture and fusion beats are common because of slower rate

Ventricular escape complexes or rhythm

Requires all of the following:
■ Rate is usually 30-40 beats/min (can be 20-50 beats/min)
■ QRS complexes are abnormal and wide
■ Occurs when the rate of supraventricular impulse arriving at the ventricle is slower than the inherent rate of the ectopic ventricular pacemaker

Ventricular fibrillation

■ Chaotic and irregular deflections of varying amplitude and contour
■ No P waves, QRS complexes, or T waves