8 - Arrhythmias Flashcards
Although there are pure forms, most common arrhythmias are combinations of both _________ and ________.
automaticity
re-entry
Describe an arrhythmia of automaticity
- Abnormality in impulse generation
- Often starts the arrhythmia
Describe an arrhythmia of re-entry
- Abnormality in impulse conduction
- Often maintains the arrhythmia
What is the primary pacemaker?
SA node
What is the escape pacemaker(s)?
-AV node then -bundle of His then -Bundle branches then -Purkinje network
What is the rate of the SA node?
60 - 100 beats/min
What is the rate of the AV node?
40 - 60 beats/min
What is the rate of the ventricles (bundle branches & purkinje network) ?
20 - 40 beats/min
Describe what is happening in a re-entry arrhythmia
- Different conduction velocity
- Different refractoriness
Type 1a AAD (anti-arrhythmic drug):
Sodium channel blockers (med)
Give examples
Quindine
Procainamide
Type 1b AAD (anti-arrhythmic drug):
Sodium channel blockers (fast)
Give examples
Lidocaine
Mexilintine
Type 1c AAD (anti-arrhythmic drug):
Sodium channel blockers (slow)
Give examples
Flecainide
Propafenone
Type 2 AAD (anti-arrhythmic drug):
Beta blockers
Give examples
Metoprolol
Atenolol
Type 3 AAD (anti-arrhythmic drug):
K+ channel blockers
Give examples
Amiodarone
Sotalol
Ibutilide
Type 4 AAD (anti-arrhythmic drug):
Calcium Channel blockers
Give examples
Diltiazem
Verapamil
Type __ = Sodium channel blockers
1
Type __ = K+ channel blockers
3
Type __ = calcium channel blockers
4
Type __ = beta blockers
2
AAD (anti-arrhythmic drugs) either control the _______ or the _______
rate or the rhythm
How do rate control agents work?
Reduce automaticity: prevent or slow arrhythmias
How do rhythm control agents work?
Reduce re-entry: prevent or stop arrhythmias
Which types of AADs control rate?
Type 2 - Beta blockers
Type 4 - Non-DBP Calcium channel blockers
Digoxin (Na+/K+ ATPase Blocker)
Which types of AADs control rhythm ?
Type 1 - Sodium channel blockers
Type 3 - K+ channel blockers
MOA of Type 2 (Beta Blockers)
- Reduced adrenergic stimulation of SA/AV nodes
- Decreased adrenergic stimulation of myocardial contractility
MOA of Type 4 (Non-DBP Calcium Channel Blockers)
- Reduced calcium current and recovery in SA/AV nodes
- Decreased calcium influx in myocytes, decreased myocardial contractility
- Relaxation of arterial smooth muscles
MOA of Digoxin (Na+/K+ ATPase Blocker)
-Increased myocyte Na+/Ca2+ causing decreased K+, increasing AV node refractory period
- Increased vagal tone, decreased SA/AV activity
- Increased intracellular Na, exchanged for Ca2+, increased contractility
MOA of Class 1 (sodium channel blockers)
- Decrease in conduction velocity
- Re-entry loop loses “steam”, SA node takes over
MOA of Class 2 (K+ channel blockers)
- Prolonged refractory period
- Re-entry loop “catches its tail”, SA node takes over
What is the idea behind anti-arrhythmic therapy?
to slow down the AV node and allow SA node to take over again
List the few pure rhythm control agents
Quinidine Sotalol Amiodarone Propafenone Flecainide Ibutilide/Dofetilide
What type is Quinidine?
Class 1a and K+ blocker
What type is Sotalol?
Class 3 and BB
What type is Amiodarone?
Class 3 and Na-channel blocker, CCB, BB
What type is Propafenone?
Class 1c and BB
What type is Flecainaide?
Pure Class 1c
What type of patients is Class 1c contraindicated in?
patients with previous heart issues?
What type is Ibutilide/Dofetilide?
Pure class 3
What does Ibutilide/Dofetilide have a high risk of?
Torsades de Pointes
> ____ bpm = tachycardic
100
< ____ bpm = bradycardic
60
Normal respiratory rate (RR) ?
12 - 20
What is atrial fibrillation?
- Atria beat really fast (400-600 atrial beats per minute) and disorganized rhythm (irregularly irregular)
- Loss of atrial kick = heart is not filled as efficiently
- Extremely fast atrial rhythm results in fast ventricular rate
Categories of atrial fib:
Acute = ?
48 hours
Categories of atrial fib:
Paroxysmal = ?
terminates spontaneously within 7 days
Categories of atrial fib:
Persistent = ?
continues for greater than 7 days
Categories of atrial fib:
Permanent = ?
does not terminate even with cardioversion attempts
What are some temporary factors that may precipitate atrial fibrillation?
Things that cause high adrenergic tone:
- alcohol withdrawl
- sepsis
- post surgery
- more on slide 18
What are some permanent factors that may precipitate atrial fibrillation?
Things that cause atrial distension:
- ischemia
- hypertension
- obesity
- more on slide 18
Signs of A fib?
-Irregular pulse
-HR > 100 bpm
-Hypotension
EKG
Symptoms of A fib?
- Asymptomatic
- Palpitations
- Dizziness
- Syncope
- Angina
- Heart Failure
Serious complications of A fib?
- Tachycardia induced HF
- Severe hypotension/HF
- Embolic stroke
What are the 3 major goals of therapy for arrhythmias ?
1) Control of rapid ventricular response = ventricular rate control
2) Restoration of normal sinus rhythm = atrial rhythm control
3) Prevention of thromboembolic complications
Once A Fib is detected, must assess patients for their risk of having a ______
stroke
If no risk of stroke, pick either ______ or ______ control
rate or rhythm
If risk of stroke, add _____ or _____
ASA or OAC (oral anticoagulant)
If a patient has no heart failure or CAD:
What rate control options are there?
- BB
- CCB (non-DHP)
- Digoxin
- Combination Rx
If a patient has CAD:
What rate control options do we have?
- BB
- CCB
- Combination Rx