21 - Atrial Fibrillation Flashcards
What are the different classifications of atrial fibrillation?
- Paroxysmal AF
- Persistent AF
- Long standing persistent AF
- Lone AF
What is paroxysmal AF?
- episodes may last 1-7 days
What is persistent AF?
not self-limited; lasts for longer than 7 days
What is long standing persistent AF?
lasts over a year
What is lone AF?
Used less often; young, low risk, CHADS2=0 (qv)
Don’t know why they have it and they’re young
What pathophysiological elements will you see in atrial fibrillation patients?
- Atrial enlargement (wall stretch)
- Ischemia
- Toxins
- Metabolic disease
- Hemodynamic impairment
Describe the atrial wall enlargement
- Can be due to mitral valve disease or rheumatic heart disease
- Wall stretch – start to break apart the conduction fibers in the atria due to increased pressure
Describe toxins that can cause atrial fibrillation
ALCOHOL = classic example
- Holiday heart symptoms because they went on a “bender” over the holidays and it is causing heart symptoms
- Direct cardiac toxin
What type of metabolic disease can send a patient into AF?
- Hyperthyroid
What type of hemotynamic impairment results from AF?
- Loss of atrial addition to the systolic volume
- Tachyarrhythmia
Describe the cardiomyopathy seen in AF
- Dilated cardiomyopathy
- Will see dilation in the left atrium and left ventricle
- The size of LA and LV will be increased in size
What types of things will you ask in the history for an AF workup?
- hypertension
- rheumatic heart disease
- valvular heart disease
- myocardial ischemia/ infarction (CAD)
- alcoholism
- palpitations
- symptoms of heart failure (SOB, PND, etc.)
- thyroid disease
- stroke
What types of things will you look for in the physical exam?
- “irregularly irregular” pulse
- variable intensity S1 (softer with long cycles)
- heart murmur (e.g. MR/MS)
- pulmonary rales/rhonchi
- hepatic edema (enlarged liver)
- peripheral edema
Why will S1 vary in intensity? Why will the mitral valve closure sound different?
Why will S1 vary? Why will mitral valve closure sound different?
- Varying levels of blood
- Varying stroke volume
- Some have more time to fill, some have less
- Mitral regurgitation – the base of the valve (circle) widens but the valves themselves do not get larger, so they pull apart
What will you do for lab tests?
Chest x-ray
- may suggest heart failure:
- pulmonary congestion
- cardiac enlargement
Lab tests
- may relate to myocardial ischemia (e.g. troponin)
- may relate to toxic/metabolic disease (e.g. thyroid fnx)
- no findings in “lone” Afib
Echocardiography
What are you looking for in echocardiography?
This is CRUCIAL
Looking for…
- Valvular disease
- Chamber enlargement
- Intracardiac thrombi
What is the main consequence of AF?
Thromboembolism
What are other consequences of AF?
- Thrombi can be present in Left Atrium
- Nonvalvular AF most common (~50%)
- Stroke (low risk in lone AF)
- Diminished cardiac output
- Ischemic events
- Exercise capacity diminished (HR does not respond to demand)
Why does the heart not respond to increased demand in cases of AF?
Loss of vagal and adrenergic chronotropic influences
What are causes of AF that are not due to pathology in the heart valves?
- Age >65
- Hypertension
- Rheumatic heart disease(also valvular)
- Prior stroke or transient ischemic attack
- Diabetes mellitus
- Congestive heart failure
What are the treatment goals in atrial fibrillation?
Rhythm and rate control
You can either try to control the rhythm (get them back in to normal sinus rhythm) or you can try to get control over the rate
Describe the goal of rhythm control
Rhythm control: restore/maintain sinus rhythm, may
- improve symptoms
- improve hemodynamics
- reduce stroke risk
- avoid anticoagulation
Describe the goal of rate control
maintain acceptable ventricular rate in chronic AFib
Describe the treatment of AF in terms of what is better - rate or rhythm control?
- No survival advantage with either strategy
- Rhythm control patients hospitalized more for adverse drug problems
- Stroke risk similar between groups
According to AFFIRM study
What did a different test say about mortality rates?
Rhythm control may be lightly more effective than rate control, but it is not a significant difference, can be due to chance
In which patients would you try to first control the rhythm?
Rhythm control: restore/maintain NSR
- Most common to try on your patient who wants great quality of life and minimal risk – younger patients
In which patients would you try to first control the rate?
Rate control: maintain acceptable ventricular rate in chronic AF
- Most common overall
- Most common in elderly procedure
What is the main goal in all patients?
Avoid embolic events!!!
Describe the process of rhythm control (younger, healthy)
- DC conversion to NSR usually preferred (v. drug tx) - shock the patient into normal sinus rhythm
Urgent DC cardioversion needed if:
- current myocardial ischemia
- evidence of hypoperfusion
- severe heart failure symptoms
- pre-excitation present
Infrequent episodes that don’t convert spontaneously
What do you do if shocking the patient into NSR doesn’t work?
Pharmacologic treatment
- Not as successful
- Not primary choice
What drugs can be used to get gain rhythm control for up to 1 week?
dofetilide (Class III) flecainide (Class IIC) ibutilide (Class III) propafenone (Class IIC) amiodarone (Class III) – most common
What drugs can be used to gain rhythm control for longer than 1 week?
dofetilide, amiodarone, ibutilide
Describe the goal of rate control
- only ~30-35% remain in NSR after conversion
- goal HR ~80 - ~110 (“lenient” rate control)*
- control of rapid rate may improve hemodynamics
- long-term, may avoid cardiomyopathy mediated by high HR
What are today’s standards for rhythm vs rate control?
rate control is currently preferred unless:
- symptoms persist despite good HR
- unable to control HR
What are common agents for ACUTE rate control?
Beta blockers (metoprolol) Ca++ channel blockers (verapamil, diltiazem)
When would you admit an AF patient from the ER?
Hospitalize:
- to initiate heparin or other anticoag
- if ablation being considered
- to treat associated medical problem
- elderly
- acute coronary syndromes
When would you send home from ER?
Send home from ER:
- no clear indication to admit (above)
- successful cardioversion
- no evidence of significant comorbidities
- “lone” AF
What other drugs would you prescribe in AF?
ANTITHROMBOLYTICS***
- In both rate and rhythm control
- If you’re cardioverting over a period of more than 48 hours, need to give antithrombolytics for at least three weeks before, during and at least four weeks after
KNOW THIS ***
When would you not give antithrombolytics?
- under 60yr
- “lone AF”
What are some antithrombolytic drugs that are used?
These are actually anticoagulants… I think what he is trying to say is that these are the agents we would use in order to PREVENT THROMOEMBOLISM!!! (main goal)
- Heparin
- Warfarin
- Aspirin
What are the benefits of warfarin?
- Reduce stroke risk by 60%
- Higher risk of hemorrhage
- Need to keep INR between 2.0-3.0
What are the benefits of aspirin?
- Reduces stroke risk by 45%
- Easy to use
- Indicated if warfarin cannot be used
What is the protocol when a patient cannot tolerate warfarin?
Aspirin alone or aspirin with clopidogrel
Does the addition of clopidogrel to an aspirin regimen alter the stroke incidence?
Yes
Aspirin alone: 3.4%/year
With clopidogrel: 2.4%/year
Does the addition of clopidogrelto an aspirin regiment alter the incidence of major bleeding?
Yes
Aspirin alone: 1.3%/year
With clopidogrel: 2.0%/year
What are NOACs?
Non-vitamin K antagonis
Oral
Anti-
Coagulants
They are a newer treatment option for atrial fibrillation and other conditions requiring blood thinners
What are some examples of NOACs?
- Dabigatran
- Rivaroxaban
- Abaxiban
What are the pros and cons of NOACs?
- No diet restrictions
- Rapid onset and offset
- Costly ($400/month) which is 100x more expensive than warfarin
- No testing available to monitor
- No reversal agent
- Limited data is available for comorbidities (restricted use in kidney disease)
What is DC cardioversion?
Shocking the patient to get them to snap out of the atrial fibrillation
When would you elect for DC cardioversion as the treatment of choice?
It is required emergently in cases of hemodynamic collapse
What are the pros and cons of DC cardioversion?
- Effective in more than 90% but does not provide a permanent solution - 30-50% revert back into AF
- May be better than pharmacological treatment
- Requires pre-cardioversion anticoagulation to decrease the risk of thromboembolism (heparin or warfarin)
What are some other treatment options for AF?
- Ablation of AV node plus VVI-R pacer
- Dual chamber (DDD-R) pacemaker (which is more effective in stroke prevention)
- Maze procedure
- Atrial defibrillator
Main point: what is AF?
AF is a defect of cardiac rhythm control which is governed by random static electricity
Main point: what are the consequences of AF?
- Clot formation in the atria
- 30% decrease in stroke volume
Main point: what are the symptoms of AF due to?
Symptoms are from decreased cardiac output and embolic vascular catastrophes
Main point: what are the treatments for AF focused on?
Treatment focuses on rate and rhythm control and prevention of clot formation