Introduction to Cardiac Arrhythmias Flashcards
Name the 2 types of Electrical disfunction
Altered automaticity
Triggered activity
What happens in altered automaticity?
latent pacemaker subverts SA node function as normal pacemaker of the heart
When does Altered automaticity occur?
when SA node firing is pathologically low or impaired
Name the 2 types of triggered activity
EAD - early afterdepolarisation
DAD- delayed afterdepolarisation
Name 2 defects in Impulse conduction
re-entry
conduction block
Name the 2 types of conduction Block
Partial
Complete
What shows a partial block on ECG of 1st AV degree?
slower conduction=lower PR interval
Name the 2 types of 2nd degree AV block
Mobitz 1
Mobitz 2
Describe the PR interval in morbitz 1?
PR interval gradually increases from cycle to cycle until AV node fails completely and a ventricular beat is missed
Describe the PR interval in morbitz 2?
PR interval is constant but every nth. ventricular depolarization is missing
What is a 3rd degree AV block? A complete block aka?
atria and ventricles beat independent of one another
Name some accessory pathways
bundle of kent
WPW syndrome
What is an accessory pathway?
some individuals possess electrical pathways that bypass the AV node
What are anti-arrhythmic drugs put into for classification?
Vaughan Williams Classification
Name the 3 classes that target Na+ channels?
Class IA
IB
IC
Name a class IA drug and describe rate
disopyramide
intermediate
Name a class IB drug and describe rate
lignocaine
rapid
Name a class IC drug and describe rate
Flecainide
slow rate
Name the class of drugs that are B-receptor antagonists? Name a drug and effect/
Class II
Metoprolol
decrease the rate of depolarisation in SA and AV
Name the class of drugs that target voltage activated K+ channels? Name a drug and effect?
Class III
Amiodarone
prolong AP duration
Name the class of drugs that target voltage activated Ca+ channels? Name a drug and effect?
Class IV
Verapamil
Slows conduction in SA and AV nodes
What classes are rhythm control drugs?
I+III
What classes are rate control drugs?
II + IV
Name the 3 drugs used in Supraventricular Arrhythmias?
Adenosine
Digoxin
Verapamil
When is adenosine used and what does it do?
– hyperpolarises the AV node briefly, suppressing impulse conduction. Treats PSVT atrial firing rate 140-250 bpm
Use this in acute phase
When is Digoxin used and does it have a low therapeutic index?
stimulates vagal activity
stimulates vagal activity (slows conduction and prolongs refractory period in AV node and bundle of His). Used to treat AF (narrow therapeutic index )
Name some effects of the narrow therapeutic index of digoxin?
nausea, yellow vision, bradycardia, ventricular arrhythmias
What does Verapamil do and when is it used?
– type IV agent – blocks L type Ca+ channel. Slows conduction and prolongs refractory period in AV node and bundle of His. Treats atrial flutter and AF. (Mostly replaced by adenosine acutely) This is a cardio selective blocker.
Name the drug used to treat ventricular arrhythmias? what it does and when its used?
Lignocaine – type IB agent – rapid block of voltage activated Na+ channels. Primarily affects Na+ channels in areas of the myocardium that discharge action potentials at high rate (e.g. an ischaemic zone). Used to treat Ventricular arrhythmias following MI
Name some drugs used in atrial and ventricular arrhythmias?
Disopyramide + procainamide Flecainide Propranolol and atenolol amiodarone and sotolol Amiodarone
What type of agents are disopyramide and procainamide and what they do?
type Ia agents – moderate block of Na+ channels
What type of agent are flecainide and what they do?
type Ic agent – slow block of Na+ channels. Prophylaxis of paroxysmal AF
What type of agents are propanolol and atenolol and what they do?
type II agents – control SVT suppressing impulse conduction through AV node. Suppress excessive sympathetic drive that may trigger VT
What type of agents are Amiodarone and sotolol and what they do?
type III – slow repolarisation of the action potential by blocking K+ channel so increases action potential duration and refractory period
What type of agents are Amiodarone and what they do?
effective against SVT and VT (it has class IA, II and IV actions and blocks B adrenoceptors). Reduces mortality following MI and Congestive heart failure. Not recommended for long term can cause Pulmonary fibrosis, thyroid disorders, photosensitivity, peripheral neuropathy
