Electrocardiography Flashcards
ECG (EKG)
measures the electrical activity of the heart and is used to determine heart rate and conduction disturbances. It may also give information on the size of the heart chambers, myocardial hypoxia, and electrolyte imbalances.
What is the normal pacemaker of the heart?
Sinus node
What are the artifacts seen on an EKG?
60Hz electrical interference
Movement: Panting, trembling, respiration, or purring
If the P wave is too wide
Left Atrial Enlargment
IF the P wave is too high
Right Atrial Enlargement
If the P waves is too tall and too wide
Biatrial Enlargement
If the R wave is too tall and the P wave is too wide
Left Ventricular enlargement
Deep S wave
Right ventricular enlargement
Right Bundle Branch Block
a delay in conduction in the right bundle branch results in delayed activation of the right ventricle causing the QRS complex to widen the large wide S waves
What causes Right Bundle Branch Block?
Cardiac Trauma Infections Neoplasia Infarction Fibrosis
Left Bundle Branch Block
the left ventricle is activated later than normal and the QRS complexes are prolonged
Wide QRS complex, Deep S wave, and normal R wave
Left Bundle Branch Block
What causes Low voltage QRS complexes?
obesity pleural or pericardial effusion hypothyroidism pneumothorax diffuse myocardial disease
Electrical Alterans
if the heart is rotating in a sac of fluid due to pericardial effusion this causes the electrical current to change directions and the R wave changes heights
What can causes changes in the Q-T Interval?
Calcium
Potassium
Drugs (Digoxin, antiarrhythmic drugs, antibiotics, drugs used to modifiy behavior)
What causes the T wave to become tall and spiked?
Hyperkalemia
Arrhythmia
abnormality in the rate, rhythm or flow depolarization through the heart
Sinus rhythm
Normal cardiac rhythm
Sinus arrhythmia
normal P wave for every normal QRS complex but the R-R interval varies. Commonly associated with Respiration. the heart rate increased with inspiration and decreases with expiration
What breeds do sinus arrhythmias occur in?
brachycephalic breeds
What will exaggerate a sinus arrhythmia?
Ocular pressure or manipulation of the viscera during surgery
Wandering Atrial Pacemaker
P waves are not initiated by the SA node
The P-R interval is decreased and the amplitude/morphology of the P waves are variable. Conduction spreads from the left atria to the right atria
What is the treatment for a Wandering Atrial Pacemaker?
No treatment
Atropine needed for surgery
Sinus Bradycardia
ventricular rate is too slow
What is Sinus Bradycardia seen with?
exaggerated parasympathetic (vagal) tone conditions in the heart drugs electrolyte abnormalities hypothyroidism
Treatment of Sinus Bradycardia
Stop or correct drug dosage
check electrolytes and thyroid
Atropine response test
Insert a pacemaker
Sinus Arrest
sinus rhythm is disrupted by occasional, prolonged failure of the SA node to initiate one or more impulses If the sinus arrest is prolonged the AV junctional or Purkinje or ventricular tissues may temporarily assume pacemaker function
Escape Beats
If the sinus arrest is prolonged the AV junctional or Purkinje or ventricular tissues may temporarily assume pacemaker function
Ventricular escape beats
originate from the ventricles
the QRS Complex is wide and bizzare
Diagnosis of Sinus Arrest
Holter monitoring/ cardiac event monitoring
Treatment of Sinus Arrest
Terbutaline isopropamide isoproterenol Probanthine Insert a pacemaker
What causes Hyperkalemia?
Renal Failure
Muscle Damage
hypoadrenocorticism
Diabetic ketoacidosis
T waves become tall and spiked, P waves become smaller and then disappear, QRS complex are prolonged and sinusoidal
Hyperkalemia
Treatment for Hyperkalemia
Sodium bicarbonate
glucose/insulin
calcium gluconate
How does calcium gluconate treat hyperkalemia?
lowers the resting membrane potential away from the threshold potential and thereby prevents fibrillation/asystole
A-V Block
delay or failure in impulse transmission from the atria to the ventricles
What causes A-V block?
ischemia myocarditis neoplasia trauma hereditary
First degree A-V Block
prolonged conduction through the AV node
Normal QRS complex after each P wave but increased P-R Interval
First Degree A-V Block
Second Degree AV Block
only intermittent conduction of impulses from the atria to the ventricles
What are the three types of Second Degree AV Blocks?
Mobitz Type I
Mobitz Type II
High grade second degree
Mobitz type I Second Degree AV Block
the P-R Interval becomes progressively longer with each beat until eventually there is a P wave but no QRS Complex
Mobitz Type II Second Degree AV Block
Dropped beat without any progressive changes in P-R Interval.
There may be one or multiple P waves that are not followed by QRS complexes
High Grade second degree AV Block
block occurs with 2:1, 3:1 blocks where it is not possible to determine if there is progressive lengthening of the P-R Interval
What causes high grade second degree AV Block?
conduction system disease
Treatment of second degree AV Block?
Atropine/glycopyrrolate
Beta-agonists or anticholinergics
Insert a pacemaker
Third degree AV Block
no conduction from the atria to the ventricles and each beat independently.
QRS Complex occur as escape beats originating from the AV junctional or ventricular pacemakers
Treatments of 3rd degree AV Block
Isoproterenol
Insert a pacemaker
Sinus Sick Syndrome
impaired function of the SA node and AV conduction system. There is usually sinus bradycardia, intermittent period of sinus arrest or AV block, long periods of asystole and escape beats. Between the periods of bradycardia and asystole there may be paraoxysms of tachycardia.
Clinical signs of Sinus Sick Syndrome
weakness and syncope during prolonged ventricular standstill
Treatment of Sinus Sick Syndrome
Insertion of a permanent pacemaker
Sinus Tachycardia
abnormally high heart rate with normal P wave and QRS-T Complexes
What is the cause of sinus Tachycardia?
Increased sympathetic tone
Hyperthyroidism
drugs
Treatment of sinus tachycardia
treat the underlying cause
Supraventricular premature depolarization
beats that occur earlier than expected (premature) and arise from outside the SA node. There is a P’ wave and QRS complexes are normal. Sometimes the P’ waves are buried in the proceeding QRS-T complex
Clinical signs of Supraventricular premature depolarization
Syncope
exercise intolerance
cough
dyspnea
Treatment of Supraventricular premature depolarization
correct the underlying disease
Sotalol
Diltiazem
Ventricular premature depolarization
arise from an ectopic focus in the ventricles.
What are Ventricular premature depolarization associated with?
ventricular hypertrophy myocarditis cardiac trauma hypoxemia use of drugs methyxanthine derivatives
Premature QRS complex that are wide and bizarre
Ventricular premature depolarization
What kind of deflection do Ventricular premature depolarizations arising from the right ventricle have?
positive deflection
What kind of deflection do Ventricular premature depolarizations arising from the left ventricle have?
negative depolarization
Bigeminy
every second beat is a Ventricular premature depolarization
Trigeminy
every third beat is a Ventricular premature depolarization
Quatrogeminy
every fourth beat is a Ventricular premature depolarization
Clinical signs of Ventricular premature depolarization
weakness
syncope
Fusion Beat
P wave has happened but no time for the AV node to be activated so the ectopic focus generates a beat at the same time of the AV node causing a fusion of beats
Treatment of Ventricular premature depolarization
Treat underlying disease Lidocaine procainamide Beta Blocker esmolol sotalol mexiletine and a beta blocker sotalol and a beta blocker
What disease is associated with Ventricular premature depolarization?
Cardiomyopathy
Dilated Cardiomyopathy
Ventricular tachycardia
runs (at >160-180bpm) of more than 3 Ventricular tachycardia
What are the types of Ventricular tachycardia?
sustained
non-sustained
Sustained Ventricular tachycardia
the runs are prolonged (>30s)
Nonsustained Ventricular tachycardia
the runs are short and terminated spontaneously
Capture beat
P wave activates the AV node and ventricles when they are not refractory and a normal QRS complex develops
Fusion beat
If the ventricles are activated by the normal QRS complex is fused with a VPC complex
Treatment of Ventricular tachycardia
Treat underlying disease Lidocaine procainamide Beta Blocker esmolol sotalol mexiletine and a beta blocker sotalol and a beta blocker
Accelerated idioventricular rhythm/ idioventricular tachycardia
Rate = 70-100bpm
P waves are seen before or superimposed on the QRS complex which maybe normal or wide or bizarre. P waves occur early to cause a capture beat or fusion beat.
Treatment of Accelerated idioventricular rhythm/ idioventricular tachycardia
Treatment is unnecessary
Closely monitor the arrhythmia
Ventricular fibrillation
life threatening and usually terminal arrhythmia with irregular and disorganized ventricular activity.
“R-on-T phenomenon”
a premature beat arriving during the vulnerable period of the cardiac cycle
Treatment of Ventricular fibrillation
electrical cardioversion
Electrical cardioversion
external countershock/defibrillation with DC current
Common disease associated with Atrial fibrillation
dilated cardiomyopathy
Atrial fibrillation
many foci in the atria which all fire independently. There is rapid and chaotic electrical activity in the atria with an absence of P waves
QRS complexes are normal but the R-R interval is variable
Atrial fibrillation
What does Atrial Fibrillation sound like?
a 5 year old playing the drums
How do you treat a dog with normal ventricular function and normal ventricular rate
do not require treatment
Monitor for regular development of dilated cardiomyopathy
How do you treat a dog with normal ventricular function and high ventricular rates
Diltiazem - calcium channel blocker
Beta Blocker
How do you treat a dog with decreased ventricular function and high ventricular response rate?
Diltiazem and Digoxin
What does an Atrial Flutter look like on EKG?
“saw tooth” pattern on EKG
Atrial Flutter
rapid rotary depolarization of the atria
Treatment of Atrial Flutter
Diltiazem
Beta Blockers