ECGs Flashcards
A wider P wave indicates what?
LA enlargement
A higher P wave amplitude indicates what?
RA enlargement
Increased amplitude of the R wave indicates what?
LV enlargement
A deep and wide S wave indicates what?
RV enlargement
What electrolyte abnormality would you suspect with increased amplitude of T waves?
Hyperkalemia
What electrolyte abnormality would you suspect with decreased T wave amplitudes that were biphasic?
Hypokalemia
What are some reasons you might see a depressed ST segment?
- Ischemia
- Electrolye abnormalities
- Digitalis toxicity
- Myocardial trauma
What might you suspect if you saw elevated ST segments?
ischemia
You should anticipate an increased risk of arrythmias in which patients?
- GDVs
- Pheos
- Hypovolemic
- GI FB
- DCM
- ARVC (Boxers)
What does this ECG indicate?

Sinus bradycardia (HR <60 in dogs or <100 in cats)
- note the consistent P and QRS complexes that are always related
What are some causes of sinus bradycardia?
- Opioids/alpha 2s
- Vagal reflex
- Hypertension (+++ sudden onset, due to baroreceptor reflex)
- Hypothermia
- Cushing’s response
- Hypoglycemia
- Hypoxia
- Hypothyroidism
- Hyperkalemia
What does this ECG indicate?

Sinus tachycardia
- HR >160 bpm in dogs, >240 bpm in cats
What are some causes of sinus tachycardia?
- Increased adrenergic tone (exercise, fear, anxiety, insufficient analgesia, “light” anesthetic plane)
- Hypovolemia
- Accidental bolus of beta agonist
- Anticholinergic
- Hyperthyroidism
- Pheo
- Hyperthermia
- Anemia
What are the hemodynamics consequences of sinus tachycardia?
- Hypertension
- Hypotension (decreased diastole—> reduced end-diastolic volume)
- Increased myocardial oxygen consumption = myocardial ischemia = arrhythmias
How do you treat sinus tachycardia?
Depends on the cause!
- analgesics, sedatives
- hypnotics
- discontinue beta agonist administration
- beta blocker (esmolol)
What does this ECG indicate?

Respiratory sinus arrhythmia
- patterned irregularity to QRS complexes
- Regularly irregular
- Shortening of the RR interval during inspiration and lengthening during expiration
What are some causes for respiratory sinus arrhythmias?
- May be associated with high vagal tone or opioid administration
- Normal at low HR in dogs
- Uncommon in cats - often associated with upper resp tract obstruction
What does this ECG indicate?

Wandering pacemaker
- variable P wave morphology
- Often seen alongside respiratory sinus arrhythmia
When should you treat wandering pacemakers or respiratory sinus arrhythmias?
If hypotension is present, then anitcholinergics should be used
What does this ECG indicate?

Atrial premature complexes
- P wave can be biphasic
- Common with LA enlargement
What is a hemodynamic consequence of APCs?
Smaller pulse wave due to insufficient fill time
What drug might you consider avoiding if your patient’s ECG is demonstrating APCs?
Opioids, since high doses of them may increase the frequency of APCs
What does this ECG indicate?

1st degree AV block
- prolonged PQ interval
- normal QRS
- caused by high vagal tone
- Treatment = none vs. anticholinergics
What does this ECG indicate?

2nd degree AV block Mobitz type I (Wenkenbach)
- progressively prolonged PQ followed by a non conducted P wave
What are the causes of a 2nd degree AV block Mobitz type I?
- High vagal tone
- opioids
- alpha 2s
- Cushing’s response
How do you treat a Mobitz I 2nd degree AV block?
- None if occasional and in absence of hemodynamic consequences
- anticholinergics can be administered if BP is low
- mannitol or HSS to decrease ICP if Cushing’s response suspected
What does this ECG indicate?

2nd degree AV block Mobitz type II
- PQ is constant before P is not conducted
What are the causes of Mobitz type II 2nd degree AV blocks?
- Fibrosis
- Cardiomyopathy
- Trauma
- Infections (ie. Lyme)
- Alpha 2’s
Less likely to be vagally mediated
May progress into 3rd degree AV block!!
What does this ECG indicate?

2nd degree AV block Mobitz type II - High grade
- 2 consecutive P waves are never conducted one after the other (always one blocked P wave in between them)
- NOT drug induced —> typically unresponsive to anticholinergics and require pacemaker implantation!
What does this ECG indicate?

Junctional escape rhythm - 3rd degree AV block
- complete dissociation b/t atria and ventricles (two independent rates)
- Narrow QRS complex, higher rate (40-60 bpm) than ventricular escape rhythm
- severe hemodynamic consequences
What does this ECG indicate?

Ventricular escape rhythm - 3rd degree AV block
- wide QRS complex, lower rate than junctional escape rhythm (20-40 bpm)
- severe hemodynamic consequences
What are the causes of 3rd degree AV blocks?
- Usually due to a damaged AV node
- Idiopathic (most frequent)
- Neoplastic
- Infiltrative
- Inflammatory
- Drug toxicity (Digitalis)
- Hyperkalemia
Very rarely vagally mediated
How do you treat a 3rd degree AV block?
- Pacemaker
- May or may not respond to anticholinergics
- Isoproterenol (beta agonist)
What does this ECG indicate?

Sick sinus syndrome
- idiopathic disease of the sinus node, most commonly seen in older female WHWT, Schnauzers, Cockers, Dachshunds
- Periods of extreme tachycardia and bradycardia, long pauses in sinus rhythm (sinus arrest) often followed by escape rhythm
What drugs should be used with care when anesthetizing a risk breed for SSS?
High doses of opioids and alpha 2’s
How do you treat sick sinus syndrome?
- Pacemaker implantation
- May or may not respond to anticholinergics
-
When anesthetized, pauses may become severely prolonged!
- When undergoing pacemaker implantation, a temporary pacemaker or external patches should be placed while animal is awake or under light sedation
Describe the 2 types of temporary pacemakers you can place
- External (trans-thoracic) patches: positioned in awake animals, pain is elicited during stimulation
-
Trans-venous temporary pacemaker:
- inserted in lateral saphenous or femoral vein and advanced into RV
- fluoroscopic guidance
- usually done under sedation or local anesthesia
- risk of vascular or cardiac perforation
- No pain during stimulation
Describe permanent pacemaker implantation
- Usually done under GA
- Protocols aimed at maintaining the intrinsic HR until pacemaker can be activated
- Inserted thru jugular and advanced in the RV
- Pulse generator fits in a pocket in the neck
- Minimally painful
Describe pericardial pacemaker implantation
- Cats, very small dogs
- In case of pacemaker revision
- Transdiaphragmatic approach
- Added difficulty: laparotomy!
- Analgesia must be provided
What does this ECG indicate?

These are the characteristic pacemaker spikes

Why do bundle branch blocks occur?
occur when electrical activity within the myocardium is re-routed from the rapid-conducting fibers of the bundle branches and travels more slowly thru the myocardial cells
- may be intermittent or persistent
- wide QRS complexes
- P wave is present and associated with the wide QRS complex
What does this ECG indicate?

Left BBB
- Positive QRS in lead II
-
Associated with severe myocardial disease (left BB is thicker than R, so damage to this branch reflects more severe dz)
- Dogs = DCM; Cats = HCM
- May be associated with impaired systolic and diastolic function
What does this ECG indicate?

Right BBB
- Deep S wave in lead I, II (negative QRS)
- May be incidental
-
R sided heart disease
- Fibrosis
- Heartworm infection
- After balloon valvuloplasty for pulmonic stenosis (usually transient)
- Often no hemodynamic consequences
What does this ECG indicate?

Atrial fibrillation
- discernible P waves are absent
- +/- F waves = oscillation of the isoelectric line of varying amplitude (low HR)
- ventricular rate is usually rapid and irregularly irregular
commonly seen in giant dogs, horses
seen in small dogs and cats ONLY with atrial enlargement
What is the hemodynamic consequence of atrial fibrillation?
The atrial kick is lost, therefore stroke volume is reduced by 20-30%
What does this ECG indicate?

Atrial flutter ‘saw tooth pattern’
- similar hemodynamic consequences as Afib
- commonly seen in giant dogs, horses
- seen in small dogs and cats ONLY with atrial enlargement
What does the term supra-ventricular tachycardia mean?
Tachycardia that originates above the ventricle (atria or AV node), characterized by elevated heart rate and narrow QRS complex
Describe ventricular arrhythmias
- QRS is wide and bizare
- No P wave
- T is opposite polarity to the QRS complex f
- can occur before the next sinus complex - VPC or after a pause ventricular escape
What does this ECG indicate?

Ventricular premature complexes
- may be isolated or couplets, triplets
- 4 or more = run of Vtach
- may be associated with cardiac or non-cardiac dz (cats = almost always cardiomyopathy)
- treatment is rarely necessary, unless they become frequent —> Lidocaine
What does this ECG indicate?

Bigeminy = one VPC every other sinus beat
What does this ECG indicate?

Trigeminy = one VPC every third sinus beat
What are some causes of VPCs?
- Primary cardiac dz
- Trauma
- Shock
- Hypoxemia/ischemia
- Electrolyte/acid-base imbalance
- GDV
- HSA
- Major abdominal surgery
When should you consider treating VPCs?
- Frequent
- Multifocal (they are present in different shapes)
- Impact on cardiac output
- Frequent runs
- R on T phenomenon - R wave is very close to previous beat T wave

What is a ventricular escape rhythm?
- The ventricle compensates for a pause = this is a compensatory rhythm
- the pause in anesthetized animals may be induced by anesthetic drugs that incr PS tone
- Lidocaine administration could suppress this compensatory rhythm!!!
- May be treated with atropine
What does this ECG indicate?

Ventricular escape rhythm
What does this ECG indicate?

Idioventricular rhythm
- looks the same as accelerated idioventricular rhythm and Vtach, only difference is rate!
- HR < 100 bpm
- Acclerated: HR > 100 bpm
- Vtac: HR >180 bpm
What are the causes of idioventricular rhythms?
- GI FB, sepsis, GDV, hemoabdomen
- Hypovolemia
- Hypoxia
- Alterations of ANS during anesthesia
When should you consider treating idioventricular rhythms?
- Idioventricular (accelerated) rhythms should not be treated with lidocaine —> both are compensatory rhythms, lidocaine may cause asystole!
- may consider using atropine if there’s a low HR
- Vtach may be treated with lidocaine if it is sustained or polymorphine or if causes hemodynamic stability
What does this ECG indicate?

Monomorphic ventricular tachycardia
- All complexes look the same
- Often minimal hemodynamic impact
What does this ECG indicate?

Polymorphism ventricular tachycardia
- complexes look different from one another
- may become torsade de pointes or Vfib
- call for help!
- get a defibrillator
What electrolyte abnormalities may cause Vtach?
hypokalemia or hypomagnesemia
What does this ECG indicate?

Ventricular fibrillation
- Shockable rhythm
What two rhythms are considered a defibrillation success?
sinus rhythm or asystole
What does this ECG indicate?

Asystole
- Non-shockable rhythm
What does this ECG indicate?

Pulseless electrical activity
- non-shockable rhythm
- may look very similar to a normal sinus complex or be associated to a wide and bizarre complex