Sinus Arrhythmias Flashcards
(43 cards)
What is an arrhythmia?
abnormality in the rate, regularity, or site of origin of the cardiac impulse
- normal sequence of activation of the atria and ventricles is altered
What are the 3 possible origins of arrhythmic beats?
- atrial: positive deflection of P waves with constant PR interval and normal QRS duration
- junctional: negative deflection of P waves or no P waves with a normally conducted short QRS (unless BBB)
- ventricular: no P waves, wide/bizarre QRS that can be negative or positive
What are the 4 major deviations for normal rate of automaticity?
- too fast = tachycardia
- too slow = bradycardia
- too irritable = premature
- absent = block
What is the expected rate of automaticity of the SA node/atrial conduction tissue, AV junction/His bundle, and bundle branches/Purkinje fibers?
70-160 bpm
40-60 bpm
20-40 bpm
(whatever site fires fastest will drive the HR)
What allows ideal interpretation of ECGs?
right lateral recumbency with proper leads
- read lead II!
What are 4 possible artifacts that may look like arrhythmias on ECGs?
- 60 cycle electrical interference
- shivering or motion
- panting
- petting or tapping head
What is likely happening on this ECG?
panting artifact
What is likely happening on this ECG?
electrical interference
What is likely happening on this ECG?
breathing artifact
What is likely happening on this ECG?
purring artifact
What are the 5 general steps to reviewing ECGs?
- calculate HR
- assess rhythm - do all complexes look the same, are intervals regular?
- identify P waves - are they positive, in normal shape and location?
- assess QRS shape and duration
- assess relationship between P and QRS complexes - should be one P for every QRS
Reviewing ECGs:
What to evaluate on an ECG:
What is normal sinus rhythm?
beat initiated by the SA node, resulting in normal rhythm, and an upright P wave
What are 4 ECG features of sinus rhythm?
- regular rhythm
- very similar RR intervals
- positive P waves on lead II
- P-QRS complexes normal with constant PR
What is occurring in this ECG?
normal sinus rhythm
What is sinus arrhythmia?
an irregular heartbeat originating from an irregular rate in the SA node, commonly associated with respiration due to vagal tone
How does sinus arrhythmia appear on ECGs? In what 3 patients is this most commonly seen?
- HR increases with inspiration
- HR decreases with expiration
- there is a normal P with every QRS, but PP and RR intervals vary (regularly irregular)
- dogs that are fit
- brachycephalics
- patients with respiratory disease
Is treatment necessary for sinus arrhythmias?
NO —> helps rule out lung disease over cardiac disease (more likely lung disease if this is present)
- Atropine can reverse it, but it is not commonly necessary
What is occurring in these ECGs?
sinus arrhythmia
- HR increases with inspiration
- HR decreases with expiration
What is occurring in this ECG?
sinus arrhythmia
- HR increases with inspiration
- HR decreases with expiration
What is a wandering atrial pacemaker?
mixed sinus and atrial rhythm —> P waves come from outside the SA node, but still within the atria, resulting in different shapes of the P waves closer to the QRS complex
- high vagal tone is common, so it is often seen with sinus arrhythmia
What are the 2 major signs of wandering atrial pacemakers on ECG? Is treatment necessary?
- variable morphology/amplitude of P waves (negative = junctional)
- variable PR interval (often decreased)
NO —> typically no hemodynamic consequences
What is occurring in this ECG?
wandering atrial pacemaker
- abnormal P wave morphology
- rest of waves are normal
