What are the 4 major supraventricular tachyarrhythmias?
Atrial tachycardia, atrial flutter, atrial fibrillation, junctional tachycardia
What are three causes of supraventricular tachyarrythmias?
Re-entry within atria, hypoxia, sick sinus syndrome
If the tachycardia has an AV nodal origin, it is referred to as__:
Junctional tachycardia
What is the clinical significance of supraventricular tachyarrhythmias?
1. decrease in filling time of ventricles leading to a decrease in cardiac output
2. Loss of atrial kick
3. Increased myocardium oxygen demand associated with decreased filling
What are two ways of managing supraventricular tachyarrhythmias?
If it is stable: through drugs
If it is unstable: electricity (cardioversion) or surgery
What is a beta blocker?
A drug which prevents stimulation of the beta adrenergic receptors, thus decreasing the heart’s activity
What is a commonly used beta blocker?
Propranolol (Generic name) Inderal (Trade name)
What does ‘generic‘ name mean?
Technical name of drug.
What does ‘trade‘ name mean?
Marketing name of drug.
What does a calcium channel blocker do?
It is a drug that inhibits the influx of calcium into cardiac muscle cells. Therefore it reduces the heart muscles’ contraction strength (and heart rate) and the conduction of impulses through the AV Node.
What is digitalis?
A powerful cardiac drug used with atrial fibrillation and flutter to decrease the ventricular response.
Unusual Beat Review
The SA node is inherently leaky to what ion?
Sodium
What is the cause of an escape beat and/or rhythm?
Sinus pause, sinus arrest, sinus block
If the SA Node pacing ceases entirely, an automaticity focus will escape to pace at its inherent rate, thereby producing an __?
Escape rhythm
If the pause in pacing is brief (one cycle missed), an automaticity focus may escape to emit a single__?
Escape beat
If the SA node stops firing or the impulse is blocked, what are 5 things that could happen?
1. SA Node restarts and fires again
2. Atrial focus fires
3. AV node fires
4. Bundle branches or purkinje system fires
5. Prolonged asystole
Often times the escape mechanisms to some type of sinus abnormality are referred to as a__?
Safety net
What is an escape beat?
The automaticity focus momentarily escapes the overdrive suppression to emit one beat.
What is the escape rhythm?
When the heart continues in the rhythm of the escape beat.
What is a premature atrial contraction (PAC)?
An impulse originating in the atria earlier than expected
Do PACs have similar shaped P waves as sinus rhythms?
No
On EKG paper a PAC may be difficult to detect when it is hiding on the peak of a T wave. What is a good thing to look for?
Look for taller than other T waves
What is a non-conducted PAC?
This is a P wave with no associated QRS complex
Does a non-conducted PAC depolarize the atria but not depolarize the ventricles?
Correct
What is it called if there is a PAC following each normal cycle, repeating in this coupling process?
Atrial bigeminy
What is it called if a there is a PAC after two normal cycles, repeating in this process?
Atrial trigeminy
With atrial bigeminy and atrial trigeminy, what is the PAC doing?
Resetting the SA Node
What is a premature junctional contraction (PJC)?
An impulse originating in the AV node. The P wave may be before or after the QRS complex or sometimes absent.
What is a premature ventricular contraction (PVC)?
An impulse originating in the ventricles. The QRS complex is often bizarre; wider, taller and deeper
What are two characteristics of premature beats?
The are usually followed by a compensatory (momentary) pause.
They are characterized by a pattern: single, bigeminy, trigeminy
How many PVC’s per minute would be considered significant?
6 or more PVCs
What are unifocal PVC’s?
PVCs that all look alike
What are multi-focal PVC’s?
Originate from different foci and do not all look alike
What is a PVC couplet?
Two PVCs occurring as a pair
Which is more serious, a unifocal PVC or a multi-focal PVC?
Multi-focal PVC
When does a PVC become of greater concern?
1. When they start occurring with great frequency (6 or more per minute)
2. If they start to group together; 3 or more is considered ventricular tachycardia
3. When they are multi-focal as this indicates increased heart irritability
Do patients with CAD have frequent PVC’s?
Yes, 50% of patients with CAD will have frequent PVC’s.
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