Module 3: Other Cs Flashcards
Definition:
Disorders of rate, rhythm, and/or conduction
Arrhythmias
- Rate: tachyarrhythmias, bradyarrhythmias
- Location of foci: sinus, atrial, junctional (AV junction), ventricular
List the consequences of arrhythmias:
- Hemodynamic compromise
- Cardiac compromise
- Electrical instability
List the causes of arrhythmias:
- Structural Heart Disease
- Metabolic & Endocrine disorders
- Autonomic imbalance (stress in class)
- Drugs & Toxins
-
Usual Suspects
- non-cardiac diseases that cause transient arrhythmias
- A pause that is > 2 P-P intervals
- Associated conditions:
- High vagal tone (Brachycephalic dogs with upper airway obstruction)
- Pathology affecting the sinus node (Neoplastic infiltration, electrolyte imbalances, drug toxicities)
- Sinus node dysfunction (When symptomatic = Sick Sinus Syndrome)
Sinus arrest
- Sinus node dysfunction that has resulted in clinical signs (syncope)
- Fibrotic changes to the SA node
- Older terrier breeds most common
- Miniature Schnauzers and Westies
- Females over-represented
Sick Sinus Syndrome (Fainting)
- Bradycardia with sinus arrest
- “Tachycardia-Bradycardia Syndrome”
- Periods of supraventricular tachycardia (atrial tachycardia) with periods of sinus arrest (this is usually when they faint)
- May also have some atrioventricular (AV) block
- conduction system can be diffusely affected
Treatment of choice for Sick Sinus Syndrome?
Artificial pacemaker
Management of sinus rhythm disturbances:
- Find cause & treat accordingly
- Pain, stress, hypovolemia, hypotension
Sinus tachycardia
Management of sinus rhythm disturbances:
- Find cause (high vagal tone, drug related) & treat accordingly
- Atropine/glycopyrrolate
Sinus bradycardia
Management of sinus rhythm disturbances:
- Atropine/glycopyrrolate
- SSS- pacemaker
Symptomatic sinus arrest
Vaughan-Williams:
Class 1:
Class 2:
Class 3:
Class 4:
Class 1: Na+ channel blockers
Class 2: Beta-adrenergic blockers
Class 3: K+ channel blockers
Class 4: Ca2+ channel blockers
(no beta kids in the car)
(T/F) All antiarrhythmic drugs can potentially be pro-arrhythmic
True
** Filler Card **
C9
- Sinus rhythms
- Sinus arrhythmias
- 2degree AV block (some species)
These are …
Normal Rhythms
- Supraventricular (atrial arrhythmias)
- Junctional rhythms
- Ventricular arrhythmias
These are …
Tachyarrhythmias
- High-grade 2nd-degree AV block
- 3rd-degree AV block
- Atrial standstill
- Sinus arrest
These are …
Bradyarrhythmias
(T/F) AV nodal conduction influences the ventricular rate but not the origin of the SVT
True
- Atrioventricular (AV) node = Gatekeeper
With any supraventricular rhythm, the rate is determined by the _____________
AV node
When the supraventricular signal doesn’t pass down to ventricles = AV node is ______
Blocked
- is considered a “physiological block” (AV node is healthy, the signals are just coming in too fast)
- Normal (or consistent with sinus) QRS morphology
- P’ waves vary and are usually different than sinus P waves
- Can be buried in preceding T wave - Often seen with structural heart disease (atrial enlargement)
- But can see with the other “causes of arrhythmias”
APC
(T/F) Treatment is necessary for APCs
False, No treatment necessary for APCs
- no clinical signs
- Ectopic rhythm originating from an atrial focus outside of the SA node
– “A Run of APCs” - May see some physiological AV block (P waves without QRS complexes)
- Start and stop abruptly
- Often rapid and the P wave is buried in the preceding T wave
- Look for P’ waves
Focal atrial tachycardia = FAT
- Large, rapid, organized circuit traveling around the atria
- Rapid, regular “saw-tooth” flutter waves
- Rate may be regular or irregular
- Variable conduction through the AV node - AV nodal conduction = determines the HR
Atrial flutter= A-Flutter
- Much more common
- Irregular, no P waves, the ventricular rate is usually rapid (can be normal), may have undulating baseline (but not always present)
- AV conduction determines the ventricular rate
Atrial fibrillation = A-Fib = AF
Treatment of Atrial Arrhythmias:
(Persistent/frequent atrial tachycardias, Atrial flutter, Atrial fibrillation)
Atrial Arrhythmias: Heart Control
Arrhythmia is sustained, but HR is slower (more physiologic) to improve CO
Heart RATE Control
Atrial Arrhythmias: Heart RATE Control
- sensitizes baroreceptors -> increases vagal tone
Digoxin
Atrial Arrhythmias: Heart RATE Control
Blocks Ca2+channels in the AV node
Diltiazem
- Class 4
- Most used/safer
Atrial Arrhythmias: Heart RATE Control
Decreases sympathetic tone; indirectly blocks Ca2+entry
- Each has pros and cons
- Digoxin is the only one that is not a negative inotrope (actually digoxin is a positive inotrope) therefore it is the drug of choice with CHF
- Often have to use multiple drugs together
Beta-blockers
- Safe to use, sometimes
Atrial Arrhythmias: Heart Control
Arrhythmia is converted to a normal sinus rhythm
Heart RHYTHM Control
Drugs that suppress automaticity or modify
conduction:
- Quinidine
What is the most common example of rhythm control?
It is with Atrial Fibrillation
- Medical Conversion
- Electrical Conversion
What is the drug of choice for acute, life-threatening ventricular arrhythmias?
Lidocaine
Use for:
- Lidocaine
- Procainamide
- Mexiletine
ventricular arrhythmias
Use for:
Quinidine
Atrial Fibrillation in horses
A 12 YO dog presents a 3-day history of diarrhea,
vomiting, and anorexia. An ECG was recorded. What is the treatment for the following rhythm?
Fluid Bolus
(T/F) Digoxin is the only one that is not a negative inotrope (actually digoxin is a positive inotrope) therefore it is the drug of choice with CHF
True
** FILLER CARD **
C10
Ventricular Arrhythmias:
- Beats coming in prematurely
- Morphology wide and bizarre (unlike the sinus beats)
- P waves present (but not associated with VPCs)
Ventricular premature complexes= VPCs = PVCs
Ventricular Arrhythmias:
- Life-saving beats originating from the ventricle, therefore still wide & bizarre
- Unlike, VPCs, these are coming in late (after a pause)
Ventricular escape beats
Ventricular Arrhythmias:
- > 3 ventricular premature beats in a row
- Heart rate is fast (tachycardia)
Ventricular tachycardia = V-tach = VT
Ventricular Arrhythmias:
Considered a type of polymorphic Ventricular Tachycardia
Treatment: Magnesium Sulfate IV
Torsade de pointes
(Turning around a point)
Ventricular Arrhythmias:
- Irregular, chaotic, deformed deflections of varying amplitude, width, and shape
- No organized activity
- No cardiac output
- Treatment: Defibrillation STAT!!
Ventricular Fibrillation
Therapy for Ventricular Arrhythmias:
What is the drug of choice (intravenous) for acute therapy of ventricular arrhythmias?
Lidocaine (IV)
Therapy for Ventricular Arrhythmias:
What is the drug(s) of choice (oral) for chronic therapy of ventricular arrhythmias?
- Sotalol (go to)
- Procainamide (also can be used IV)
- Amiodarone (also can be used IV)
- Atenolol
-
Mexiletine (also a go-to)
(SPAAM)
- Rhythm coming from the ventricles
- Not fast (usually less than 170bpm in dogs)
- “Accelerated” as compared to an escape rhythm but not tachycardic
- Usually related to non-cardiac causes
-
Sick animals in the ICU
Treat underlying cause
Accelerated Idioventricular Rhythm= AIVR = “Slow V-Tach”
- QRS wide (More than just LV enlargement)
- Dog: > 80 ms
- Cat: > 60 ms - Normal MEA or left-axis deviation
Left Bundle Branch Block (LBBB)
- This is similar QRS morphology as a VPC originating from the right ventricle
- Sinus rhythm with “right-sided” VPC doesn’t have a “P wave” before it
- QRS wide:
- Dog: > 80 ms
- Cat: > 60 ms - Right axis deviation
- deep (negative) S wave in I & II
- Positive QRS in avR
Right Bundle Branch Block (RBBB)
- This is similar QRS morphology as a VPC originating from the left ventricle
What is the difference between RBBB vs RV enlargement?
Both have a right axis deviation, BUT the QRS with RBBB is wider than with RV enlargement alone (you can poke your finger with it)
- Slowed or blocked conduction through the AV node
- Varying degrees of AV block possible
Atrioventricular Block = AV block
What has a high vagal tone and is a common finding & normal rhythm in horses?
2nd degree AV Block (Type I)
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