End of Part 2 + part 3 arrhythmias Flashcards
ECG criteria for 3rd degree AV block
- P waves with no QRS
- Inconsistent PR intervals (AV dissociation)
- Ventricular or Junctional escape beats
- Low HR
Ventricular escape beat = wide QRS
Junctional escape beat = narrow QRS
Main cause of Mobitz Type I 2nd degree AV block?
High vagal tone (PNS)
Main cause of Mobitz Type II 2nd degree AV block?
- Structural heart disease of the AV node
Ex: Hyperkalemia, myocarditis, fibrosis
Main cause of 3rd degree AV block?
- Structural heart disease of the AV node
Ex: Hyperkalemia, myocarditis, fibrosis
ECG criteria for BBB (bundle branch blocks)?
- Wide QRS
- Every P has a QRS (sinus rhythm)
(Looks like AIVR and V-TACH, difference is these exhibit AV dissociation and BBB do not)
Main cause of left sided BBB?
Cardiomyopathy / structural heart disease
ECG criteria for Atrial standstill?
- No P waves at all (straight line before QRS)
- Normal QRS
- Usually bradycardia
Causes of atrial standstill?
- Hyperkalemia (urinary obstruction, Addisons)
- Neuromyopathy in springer spaniels
What breeds are predisposed to sick sinus syndrome?
- Mini schnauzer
- West highland terrier
- Dachshund
- Cocker spaniel
What is Sick sinus syndrome?
Complex disturbance of impulse conduction resulting in sinus bradycardia and/or sinus arrest (prolonged sinus pause)
- SA node cells become fibrotic
- Can cause SVPCs or VPCs
- Can cause 1st or 2nd degree AV block
Effects of hypokalemia?
- Prolongs repolarization
- Causes excitability due to K+ imbalance, resulting in ectopic complexes like SVPCs and VPCs
Mild, Moderate, and Severe effects of hyperkalemia?
Mild: Shortened repol and Tented T waves (tall and pointy)
Mod: Wide QRS complexes (ventricles messed up)
Severe: Prolonged PR intervals or absent P waves, v-fib, death
Hyperkalemia ___________ the time of repolarization, while hypokalemia _________ the time of repolarization
shortens, prolongs
What arrhythmias can be seen with hypokalemia?
- Ectopic complexes like SVPCs and VPCs
What electrolyte imbalance can result in atrial standstill?
Hyperkalemia
What device records ECG continuously for 24-48 hours?
Holter monitor
When is an arrhythmia considered hemodynamically significant?
If it results in low CO, low BP, and hypoperfusion
4 indications for anti-arrhythmic therapy:
- Hemodynamically significant
- Causing CS
- Potential to deteriorate into fatal arrhythmia (Ex: VPC or VT turning into V-fib)
- Negatively impacting cardiac function
List the drugs belonging to Class I anti-arrhythmics and their MOA
MOA: Na+ channel blocker
- Lidocaine
- Mexiletine (PO)
- Procainamide
- Quinidine
List the drugs belonging to Class II anti-arrhythmics and their MOA
MOA: Beta blockers
- Atenolol
- Esmolol
- Propanolol
- Metoprolol
List the drugs belonging to Class III anti-arrhythmics and their MOA
MOA: K+ channel blocker
- Sotalol
- Amiodarone
List the drugs belonging to Class IV anti-arrhythmics and their MOA
MOA: Ca+ channel blocker
- Diltiazem
- Verapamil
Effects of digoxin on the heart?
Increases vagal tone (PNS) in the SA and AV nodes
(Neg chronotropy, slows down HR)
Treatment for sinus tachycardia?
- No antiarrhythmic therapy needed (physiological response, treat underlying cause)
Exception: ST due to toxicity/drugs - Use Esmolol (slows down HR)
Drug treatment protocol for supraventricular tachycardia?
Goal: Slow down HR
- Diltiazem is first choice for SVT
- Second choices: Beta blockers, Digoxin, Sotalol
________ is the first line DOC for treatment of supraventricular tachycardia
Diltiazem
- Ca+ channel blocker, Class IV anti-arrhythmic
Drug treatment protocol for atrial fibrillation?
Goal: control rate and rhythm
Rate:
- Diltiazem is first choice for A fib, slows down AV conduction
- +/- Digoxin
Rhythm:
- Electrical cardioversion (defibrillation shock), restores AV synchrony
Drug treatment protocol for SVPCs?
- Not necessary unless frequent or sustained bigeminy, in that case use Diltiazem
When is anti-arrhythmic therapy for VPCs indicated?
- > 1000 single VPCs/24 hrs
- Frequent or sustained ventricular bi or trigeminy
OR - R or T phenomenon (T wave goes into QRS complex without finishing repol)
Any frequency or duration of _________ warrants anti-arrhythmic treatment
Ventricular tachycardia
Drug treatment protocol for V-tach?
Lidocaine!!! - first choice
Second choices: Procainamide, amiodorone, magnesium
If VT is not sustained and patient is not hemodynamically unstable start with PO Mexiletine or Sotalol
Positive atropine response test
- Bradycardia turns into tachycardia, meaning bradyarrhythmia was due to high vagal tone
Negatice atropine response test
- HR stays the same after inj
- Bradyarrhythmia likely due to structural heart disease and not high vagal tone (Ex: SSS vs sinus bradycardia due to PNS)
Which arrhythmias require a pacemaker?
- High grade Mobitz type II 2nd degree AVB (Ps without QRSs)
- 3rd degree AV block/ Complete AV block (Ps with no normal QRS, only escape beats)
- Sick sinus syndrome (sinus bradycardia or sinus arrest) - only if symptomatic
- Atrial standstill (must rule out hyperkalemia first)
Drug treatment protocol for 1st, 2nd, and 3rd degree AV block
Only High grade Mobitz type II 2nd degree AVB and 3rd degree AV block require anti-arrhythmic therapy
- Requires pacemaker, high risk of sudden death if not
- Dopamine, dobutamine, atropine while waiting
No tx needed, look for underlying cause of high vagal tone
1. 1st degree AVB
2. Mobitz type I 2nd degree AVB
3. Low grade Mobitz type II 2nd degree AVB
True or False: Sick sinus syndrome is associated with high risk or sudden death
False
What drugs can be given in an emergency setting while awaiting pacemaker implantation?
- Dopamine, dobutamine, isoproteronol (sympathomimetics)
Sinus tachycardia vs supraventricular tachycardia?
Sinus tachycardia
- every P has a QRS, normal rhythm, consistent RR intervals
- Everything normal just high HR
- Due to high sympathetic tone
Supraventricular tachycardia
- > 3 SVPCs
- pre-mature QRS complexes close together
- Regular irregular rhythm
- Due to atrial dilation
