Chapter 9 Flashcards
Ventricular Dysrhythmias
Referred to as ventricular escape rhythms. Current is not traveling down the nol ventricular conduction pathway to activate both the R and L ventricles simultaneously, which causes delay to depolarize (contract) the ventricles. Indicated by a QRS measuring 0.12 seconds or longer.
Where are ventricle pacemaker cells found?
In the Purkinje fibers (the last natural pacemaker)
Nl rate in Purkinje fibers
20-40 bpm
Ventricular rhythms either occur as a result of:
- Failure of the higher pacemaker sites within the heart or
- The rate of automaticity from this portion of the heart is faster, and it takes over as the primary pacemaker within the heart
How to identify ventricular dysrhythmias
Missing P waves and “wide and bizarre” QRS complexes that measure 0.12 or greater
Premature Ventricle Complex (PVC)
Caused by an ectopic impulse that occurs early in the cycle and originates form the ventricles which causes excitability of the ventricular myocardium
What causes ectopic impulses?
By an ischemic region within the ventricles. Ischemia increases excitability of the ventricular myocardium.
Unifocal premature complex
Early complex (has similar shape, suggesting only one irritable focus present)
Multifocal premature complex
Varied shapes and forms of the PVCs
Interpolated PVC
PVC occurs during the normal R-R interval without interrupting the underlying rhythm
Occasional PVC
More than one to five PVCs per minute
Frequent PVC
Six or more PVCs per minute
Bigeminy PVC
Every other complex is a PVC
Trigeminy PVC
Every third complex is a PVC
Quadgeminy
Every fourth complex is PVC
R on T PVCs
PVC occurs on the downslope of the T wave or the vulnerable period of the ventricular refractory period
Coupling PVC
Two PVCs that occur back to back
PVC criteria for classification
Early QRS complex that measures 0.12 sec or greater and has a wide and bizarre appearance. There is no P wave