Pathophysiology of arrhythmias Flashcards
How are disturbances in cardiac rhythm diagnosed?
ECG
What causes sinus bradycardia?
- Drugs; beta-blockers, dilitiazem
- Vagal activity
- Hypothyrodism
- sinus node disease
- Electrolyte abnormalities
What causes AV block?
- Vagal activity
- myocardial infarction
- electrolyte abnormalities
What is 1st degree AV block?
lengthening of the PR interval
What is Mobitz type 1 AV block?
Progressive lengtheing of the PR interval until the P was is blocked at the PR is short again
What is Mobitz type 2 AV block?
Block after 2 or 3 conducted beats in regular pattern
What is 3rd degree AV block?
complete AV dissociation
What are the treatments for bradycardias?
- Pacemakers
- temporary
- permanent
- Only if needed
- treat symptoms of syncope/dizziness
- prophylatic at time of operations
- post AMI
Types of narrow comples/supraventricular tachycardias
- Atrial tachycardia
- Junctional tachycardias (nodal tachycardia)
- AVNRT and AVRT
- Atrial flutter
- Atrial fibrillation
What are the indications a dysrhytmia is a narrow complex tachycardia
QRS duration is less than 120ms
What is the origin of narrow complex tachycardias?
Above the AV node
What are the characteristics of broach complex tachycardias?
QRS complex is wider than 120ms
What are the types of broad complex tachycardia
- Ventricular tachycardias
- Monomorphic and polymorphic VT
- Fasicular (RBBB and LAD are not very wide)
- RVOT (LBBB and RAD)
- SVT with aberration (=aquired, rate dependent bundle branch block)
- SVT with pre-exisitng BBB morphology on ECG
- SVT of antidromic tachycardia on WPW
What are the basic mechanisms of tachycardias?
- Ectopic focus
- Re-entry/circus movement
- Fibrillation - independent wavelets of activity
What describes a regular, narrow complex tachycardia without P waves activity?
AVNRT or AVRT
What is AVNRT?
AV nodal re-entrant tachycardia
Tachycardia where re-etry circuit is through juxa-nodal material
What is AVRT?
AV re-entrant tachycardia
Tachycardia where re-entry is through an accessory pathway
What terminates AVNRT and AVRT?
IV adneosine
What is Wolff-Parkinson-White syndrome?
- Pre-excitation of ventricles
- Anatomical atria-ventricular bypass tract with non-decremental conducting properties
Characteristics of WPW syndrome on an ECG
Shortened PR interval (less than 3 boxes)
Slurred upstroke of ORS and widened QRS complex (more than 3 boxes)
What does WPW syndrome form the basis for?
Circus movement and AVRT
Over a concealed accessory pathway; doesnt conduct atria to ventricle
What can be seen if accessory material is very lateral?
retrograde P waves
What occurs when adenosine is administered in atrial fibrillation or atria tachycardia?
transient slowing of the heart without revealed P waves
What occurs when adenosine is administered in AVNRT or AVRT?
restoration of sinus rhythm
What is atrial fibrillation
irregular narrow complex tachycardia with no P waves
Symptoms of atrial fibrillation
faster ventrciular response rate, SOB and hypotension
What are the causes of atrial fibrillation?
- ischaemic heart disease
- hypertensive heart disease
- mitral valve disease
- thyrotoxicosis
- Alcohol
- post bypass
- myocarditis
- accessory pathways
Mechanism of atrial fibrillation
Size of LA
Foci of wavelet generation around the insertion of the pulmonary veins (must be more than 5 independent wavelets of activity)
