Arrhythmias Flashcards
What 2 heart conditions are typically caused by medication?
- heart block
- torsades de pointes
What does the p wave correspond to?
- first depolarization
What does the QRS complex correspond to?
- larger ventricle depolarizing
What does the T wave correspond to?
- ventricle is repolarizing
What are the main pathological reasons for a tachyarrhythmia?
- automaticity: abnormality in impulse generation
- often starts the arrhythmia - re-entry: abnormality in pulse conduction
- often maintains the arrhythmia
What are considered to be escape pacemakers of the heart?
- AV node
- bundle of His
- bundle branches
- Purkinje network
What is the role of the AV node?
- the AV node is the gatekeeper
- other cells are between the ventricles and the atria do not have enough capacity to conduct an electrical current
If the AV node or the bundle of His become the main pacemakers, what will the heart rate be?
40-50 bpm
If the bundle branches or the purkinje network become the main pacemakers, what will the heart rate be?
20-40 bpm
What is the pathology of a re-entry arrhythmia?
- if side of the heart (or the SA node) is still refractory when an electrical current is trying to pass through, then the electrical current will back up and loop through the heart the other way (the AV node or bundle of His will become the pacemaker) and when it gets back to the refractory section it can pass through now since it is non-refractory. The heartbeat will continue on to be the same this way
What is a class 1 AAD?
Na channel blocker
What is a class 2 AAD?
beta blockers
What is a class 3 AAD?
K channel blockers (these are the most common in terms of rhythm control)
What is a class 4 AAD?
calcium channel blockers
What does reducing automaticity do?
- prevents and slows arrhythmias
What is the effect of beta blockers on the heart during an arrhythmia?
- reduced adrenergic stimulation of the SA/AV nodes
- decreased stimulation of myocardial contractility
What is the effect of non-DBP Calcium channel blockers on an arrhythmia?
- reduced calcium current and recover in the SA/AV nodes
decreased calcium influx in myocytes, decreased myocardial contractility
What is the effect of digoxin on an arrhythmia?
- increased myocyte Na/Ca, decreased K, increased AV node refractory period
- increased vagal tone, decreased SA/AV node activity
(increased intracellular Na, exchanged for Ca, increased contractility)
What ion channels do digoxin block?
Na/K ATPase
What do sodium channel blockers do to the heart?
- decrease in conduction velocity
- re-entry loop loses “steam”, SA node takes over
What do potassium channel blockers do to the heart in an arrhythmia case?
- they cause a prolonged refractory period
- re-entry loop “catches its tail”, SA node takes over
Are more agent pure rhythm control agents or have multiple activity on the heart?
- few are pure rhythm control agents
What is quinidine?
- class 1a and K blocker
What is sotalol?
- class 3 and beta blocker
What is amiodarone?
- class 3 and Na, Ca, and beta blocker
What is propafenone?
class 1c and beta blockers
What is flecainide?
- pure class 1c, but high risk for VT in CAD
What is ibutilide/dofetilide?
- pure class 3, but high risk here for tornadoes de points
Heart rates of what are considered tachyarrythmic?
> 100 bpm
Heart rates under what are considered bradyarrhythmic?
<60 bpm
What is atrial fibrillation?
- very fast atrial rate and a disorganized atrial rhythm that is irregularly irregular
What happens when there is a loss of the atrial kick?
- the heart is not filled up as efficiently
What does an extremely fast atrial rhythm result in?
- a fast ventricular rate
How much of the pumping to the heart do you lose upon atrial fibrillation?
10-20% of the extra flow that fills the heart comes from the atria
What action does a rate controlling agent have?
- slows doen the rate of the ventricles
What action does a rhythm controlling agent have?
- tries to normalize the rhythm of the atria
What are the categories of atrial fibrillation?
- acute
- paroxysmal
- persistent
- permanent
What is acute atrial fibrillation?
atrial fibrillation that lasts 48 hours
What is paroxysmal atrial fibrillation?
this terminates spontaneously within 7 days - can come back multiple times