atrial fibrillation

Question 1

Answer 1

Atrial fibrillation

Question 2

describe the classification of atrial fibrillation

Answer 2

• Paroxysmal AF

–> Recurrent (two or more episodes)

• Persistent AF

–> Not self-limited; lasts for longer than 7 days

• Long standing persistent AF

–> lasts over a year

• “Long” AF

–> used less often; young, low risk, CHADS2=0 (no risk factors

Question 3

describe pathophysiology of atrial fibrillation

Answer 3

• Causes:
• Atrial enlargement (wall stretch) via mitral valve disease or rheumatic heart disease
• Ischemia
• Toxins (alcohol) = direct toxin on cardiac conduction system
• metabolic disease = hyperthyroid (one of the treatable causes)
• Hemodynamic impairment = Loss of atrial addition to SV or tachyarrhythmia

Question 4

What are some consequences of atrial fibrillation

Answer 4

• ThomboEmbolism**

–> thrombi can be present in left atrium

–> risk of stroke low in lone Afib

• Diminished cardiac output (less diastolic filling)
• Ischemic events (uncontrolled rate increases MVO2)
• Exercise capacity to demand (HR does not respond to demand)

–> loss of vagal and adrenergic chronotropic influences

Question 5

name some nonvalvular causes of atrial fibrillation

Answer 5

• age >65
• Hypertension
• Rheumatic heart disease (also valvular)
• prior stroke or transient ischemic attack
• Diabetes mellitus
• Congestive heart failure

Question 6

Describe tx goals of AFib

Answer 6

• Rhythm control: restore/maintain sinus rhythm

–> improve symptoms, hemodynamics, reduce stroke risk, avoid anticoagulation

• Rate control: maintain acceptable ventricular rate in chronic AFib (used in elderly)
• goal to avoid embolic events

Question 7

describe Rhythm control

Answer 7

• DC conversion to NSR usually preferred (versus drug tx)
• Urgent Drug Control cardioversion needed if:

–> current myocardial ischemia

–> evidence of hypoperfusion

–> severe heart failure symptoms

–> pre-excitation present

• infrequent episodes that don’t convert spontaneously
• Pharmacologic Tx less successful, not primary choice

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Question 8

describe Rate control

Answer 8

• 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 (develops hypertrophy)
• PREFERRED UNLESS: symtpoms persist despite good HR, unable to control HR

* beta blockers (metoprolol) and Ca channel blockers

Question 9

Hospitalize vs sending home

Answer 9

• Hospitalize

–> to initiate heparin or other anticoag

–> if ablation being considered

–> to treat associated medical problems

–> elderly

–> acute coronary syndromes

• send home from ER:

–> no clear indication to admit (above)

–> successful cardioversion

• no evidence of significant comorbidities

–> lone AF

Question 10

antithrombotic therapy

Answer 10

• Heparin
• Warfarin

–> reduces stroke risk

–> higher risk of hemorrhage

–> keep INR 2.0-3.0

• Aspirin (used in elderly who are falling)

–> reduces stroke risk by 45%

–> easy to use

–> indicated if warfarin cannot be used

Question 11

points to ponder

Answer 11

• atrial fibrillation is a defect of cardiac rhythm control; static electricity (random) governs
• Consequences are clot formation in the atra and 30% drop in stroke volume (drives symptoms)
• symptoms are from decreased cardiac output and embolic vascular catastrophes
• treatment focuses on rate and rhythm control and prevention of clot formation (generally rate controlled, rhythm in younger patients)