Cardiac Arrythmias Flashcards
5 Causes of Arrhythmias
1-Abnormal rhythmicity of the pacemake
2-Shift of pacemaker activity
3-Conduction of blocks
4-Abnormal pathways of impulse transmission
5-Spontaneous generation of abnormal impulses
3 Normal Cardiac Rhythmns
1-Normal sinus rhythm: impulses originate at SA node at normal rate
2-Sinus arrhythmia: impulses originate at SA node at varying rates
3-Wandering atrial pacemaker: impulses originate from varying points in atria
In ALL: PQRST waves are normal. Spacing may just vary.
Primary cause of sinus arrythmia
Breathing
Normal HR for cats and dogs
Cats=140-220
Dogs=70-160
Abnormally fast or slow heart rate originating at SA node
Fast-sinus tachycardia (maybe due to fever or hyperthroidism or in shock)
Slow-Sinus bradycardia
Sinus Arrest
When SA node stops firing
Describe ECG for sinus arrest
Normal PQRST waves then there’s nothing for ~5 seconds because SA node didn’t fire.
First-degree atrioventricular block
There’s a fixed by prolonged PR interval. P-R interval is greater than 0.14 seconds n dog.
No dropped beats
Second degree AV block: Mobitz type I
There’s progressive lengthening of PR interval with intermittent dropped beats.
Dropped beat.
Second degree AV block: Mobitz type II
AV block at bundle of His lvl
There’s a sudden dropped QRS without prior PR lengthening.
Often see P:QRS in ratios
Third degree AV block
Impulses originate at SA node but there’s no coordination with perkinje fibers.
Atria and ventricles are on different pages
P:QRS does not have a relationship.
Depending on if L or R perkinje fibers pick up impulse will give S or R wave.
L=S
R=R
Supraventricular and Ventriculr Abnormalities (3)
Premature contraction
tachycardia
Fibrillation
Reasons for premature contractions
- Contractions occur before they are supposed to
- Pulse deficit:ventricles don’t fill with blood properly and stroke volume is decreased
- Bigeminal pulse: every other beat may be premature
Tachycardia definition
At least 3 or more premature contractions
Paroxysmal:lasts for varying amount off time and can stop whenever
What are fibrillations
Many separate and small waves spreading at the same time in different directions over cardiac muscle.
Difference between sinus tachycardia and supraventricular tachycardia
Sinus tach=physiological. SA node just firing faster
SupVen Tach= pathological: premature contractions
Supraventricular premature contraction (3)
- Premature beats
- Looks similar to sinus beats
- Duration of QRS complexes are usually normal
Atrial/Supraventricular paroxysmal tachycardia
There’s sudden burst (of at least 3) QRS complexes. Ventricles may not be properly filling with blood. HR is really high
Atrial flutter
Impulses travel in circular course in atria setting up regular rapid flutter waves without QRS.
Irregular ventricular rate.
Atrial fibrillation
Impulses take chaotic/random pathway to atria
No distinct P waves and no coordinated atrial contraction
QRS looks normal but irregular spaced
Ventricular premature contraction
QRS are wide and bizarre due to ectopic focus in ventricular myocardium
Ventricular bigeminy
Every other QRS wave is wide and bizarre.
May be due to stretched tissue in heart in ventricles
Ventricular paroxysmal tachycardia
Random run of at least 3 QRS that are wide and bizzare.
Ventricular fibrillation
No coordination in ventricular depolarization. No really defined QRS wave.
