Sandbox/07

# Criteria and Definitions of Ventricular Rhythms
- Ventricular premature complex, uniform, fixed coupling
- Ventricular premature complex, uniform, nonfixed coupling
- Ventricular premature complex, multiform
- Ventricular premature complexes, in pairs (2 consecutive)
- Ventricular parasystole
- Ventricular tachycardia (3 consecutive beats)
- Accelerated idioventricular rhythm
- Ventricular escape complexes or rhythm
- 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:

## 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:

## 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
 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)
 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