Ch. 9 Notes: Ventricular Dysrhythmias Flashcards
Where are the ventricular pacemaker cells?
In the Purkinje fibers
The Purkinje fibers are the ______ ___________ pacemaker cells in the heart
last inherent
What is the rate of automaticity of the Purkinje fibers?
20-40 bpm
Why does the current travel through the ventricles through cell-by-cell conduction?
Because there are no conductive pathways beyond the Purkinje fibers
What occurs as a result of the current traveling through cell-by-cell conduction?
The ventricles take longer to depolarize so there is a wide QRS complex
What are the reasons for ventricular rhythms?
- Higher pacemaker sites in the heart fail
- Increased automaticity
- Third degree block prevents supraventricular impulses from reaching the ventricles
Why does increased automaticity lead to a ventricular rhythm?
Purkinje fibers is faster than other pacemakers so it takes over as the primary pacemaker
What causes the Purkinje fibers to become the primary pacemaker?
- Ischemia (most common)
- Electrolyte disturbances (involving potassium or magnesium)
What are characteristics of all ventricular rhythms?
- Missing P waves
- Wide and bizarre QRS complex (>120 ms)
- Inverted T waves
Why are P waves missing from ventricular rhythms?
The impulse is coming from the ventricular fibers, not the SA node
What are premature ventricular complexes (PVCs)?
Ectopic impulses that occur early in the cycle and originate from the ventricles
What causes PVCs?
Ischemic region in the ventricles which increased irritability of ventricular myocardium
What are unifocal PVCs?
PVCs coming from one ectopic focus; all have same shape since they all take the same path
What are multifocal PVCs?
PVCs coming from more than one ectopic impulse; all have different shapes
What can multifocal PVCs indicate?
More than one area of ischemia
Why is there a “pause” on the ECG strip containing unifocal or multifocal PVCs?
The PVC interrupts the rhythm, so it has to wait for next normal impulse to come
What are interpolated PVCs?
PVC comes right between normal impulses without interrupting rhythm; not common
What are occasional PVCs?
Less than 6 PVCs per minute on the ECG strip
What are frequent PVCs?
6 or more PVCs per minute on the ECG strip
What are bigeminal PVCs?
Every other impulse is a PVC
What are trigeminal PVCs?
Every third impulse is a PVC
What are quadrigeminal PVCs?
Every fourth impulse is a PVC
What are R-on-T PVCs?
When the PVCs begin on the downslope of the T wave; stimulating heart on T wave could lead to cardiac arrest/ventricular fibrillation
What are coupling PVCs?
Back-to-back PVCs
What is run of ventricular tachycardia aka Salvo of PVCs?
3 or more PVCs in a row
What is paroxysmal event?
Sudden change in cardiac rhythm; cardiac arrest occurs, needs defib
What is the characteristic of the atrial and ventricular rhythms of an ECG strip with PVCs?
Regular for underlying rhythm; PVCs interrupts underlying rhythm w/ early QRS complexes and causes a pause until underlying rhythm returns (irregular)
How do you find the atrial and ventricular rate of an ECG strip with PVCs?
Same as underlying rhythm; PVCs make ventricular rhythm faster than atrial rate
What is the characteristic of P waves in an ECG strip with PVCs?
U+R in underlying rhythm; absent in PVCs
What is the characteristic of the PR interval in an ECG strip with PVCs?
Follows underlying rhythm; not measurable in PVCs
What is the characteristic of the QRS complex in an ECG strip with PVCs?
Underlying is usually 60-100 ms; complex in PVC is wide and bizarre (120 ms or more)
How does the patient tolerate PVCs?
Can be normal depending on PVC frequency; frequent or grouped PVCs can cause dizziness or other s/s of low CO
When does agonal rhythm occur?
All of the pacemakers in the heart have failed; aka dying heart rhythm
What are the characteristics of the atrial rhythm and rate of agonal rhythm?
Cannot be determined
What is the characteristic of the ventricular rhythm and rate of agonal rhythm?
May or may not be regular and rate is less than 20 bpm
What is the P wave morphology for agonal rhythm?
Absent
What is the characteristic of the PR interval for agonal rhythm?
Cannot be determined
What is the characteristic of the QRS complex for agonal rhythm?
Greater than 120 ms, wide, bizarre
How does the patient tolerate agonal rhythm?
Profound loss of CO, unconscious
What occurs during an idioventricular rhythm?
Impulse is created by the ventricular pacemaker
What is idioventricular rhythm also referred to as?
The ventricular version of escape rhythm
What is the characteristic of the atrial rhythm and rate for idioventricular rhythm?
P-P interval and atrial rate cannot be determined
What is the characteristic of the ventricular rhythm and rate for idioventricular rhythm?
R-R interval is regular and 20-40 bpm
What is the P wave morphology for idioventricular rhythm?
Absent
What is the characteristic of the PR interval for idioventricular rhythm?
Cannot be measured
What is the characteristic of the QRS complex for idioventricular rhythm?
Greater than 120 ms, wide, bizarre
How does the patient tolerate idioventricular rhythm?
Profound loss of CO, unconscious
Why is there a profound loss of CO in idioventricular rhythm?
Because of the low rate of 20-40 bpm
What extra measures should be taken if a patient has agonal or idioventricular rhythm?
- BLS and ACLS interventions if patient is unconscious
- Medication and/or pacing as treatment (for idiovent.)
What is the main identifier for accelerated idioventricular rhythm?
Faster HR than idiovent.
What is the characteristic for the atrial rhythm and rate for accelerated idioventricular rhythm?
P-P interval rhythm and rate cannot be determined
What is the characteristic of the ventricular rhythm and rate
