Atrial Fibrillation
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Introduction
Atrial rate is so fast in fibrillation that discrete P waves are no longer discernible. Ventricular rate is irregularly irregular and tends to be 140-160 bpm. Rapid ventricular rates can decrease cardiac output, and atrial thrombi, particularly in the left atrial appendage. Cardioversion should not be done unless systemic anticoagulation has been given for at least three weeks.
It is extremely common; 1/5 over 40 will develop it. A fib affects 5% of people over 70, 10% of people over 80%.
doubles mortality in age-matched people
The Case of...
a simple case introducing clincial presentation and calling for a differential diagnosis to get students thinking.
Causes and Risk Factors
Aging, hypertension, and heart failure are the most common causes.
Other risk factors include:
- alcohol
- valvular HD
- cardiomyopathy
- sick sinus syndrome: ECG diagnosis (sinus bradycardia, sinus arrest, tachyarrhytmia)
- cardiac surgery
- pericarditis: vial, tumour infil
- WPW: Wolff-Parkinson-White syndrome: accessory bundle
- thyrotoxicosis
- lung cancer
- idiopathy
Very important to first assess for reversible causes
Reversible Causes
- alcohol
- caffeine
Intermittent: paroxysmal - stops on its own. ie lasts for one hour.
Persistent: won't go away on its own, unless you shock or give anti-arrhytmic drug
Non-Reversible Causes
Permanent
Fibrillation and flutter can coincide.
Pathophysiology
Atrial fibrosis
Atrial stretching:
- HTN
- HF
- mitral stenosis
cells around the atrial-pulmonary junction.
AV node will only allow so many beats through.
A fibrillation and heart failure are common co-presenting problems.
HF can predispose for AFib, while AFib can cause or worsen CHF.
very frequent atrial ectopy can trigger fribrillation, using triggered or automatic. An abnormal atrium, scarred and stretched, is easily put into fibrillation by triggers, due to easy reentry.
Signs and Symptoms
- history
- physical exam
History
some people can be asymptomatic. other people feel terrible. symptoms can include angina (if with CAD), CHF (if with valvular disease), fatigue, syncope/lightheadedness
Physical Exam
An irregularly irregular rapid pulse is often present. Assess heart rate at heart apex, not pulse, as some beats will not get through.
young folks ~200 bpm, deacreases with age.
Investigations
- lab investigations
- diagnostic imaging
Lab Investigations
Diagnostic Imaging
A stress test can be used to exacerbate abnormal rhythms.
A 24-hour Holter monitor can be used to assess response to medication.
A loop monitor can be useful for symptoms that occur a few times monthly.
Differential Diagnosis
Treatments
Treatment depends on
- diagnosis and underlying disease.
- Rhythm control vs rate control.
- risk of stroke.
- rate control
- rhyrthm control
- cardioversion
- electrical ablation
- anticoagulation
Rate Control
- metoprolol, nadalol 2nd line
- digoxin, though not useful on its own
- diltiazem
- amiodarone, more acute
AVN ablation and pacing.
For patients with AF and HF, rate control = rhythm control in terms of cardiovascular mortality. Rate control reduces cardioversion and hospitalization, and should be the primary approach
Rhythm control
Electrical cardioversion
pharmacological cardioversion - amiodorone.
drugs to maintain NSR. Antiarrhytmics can have adverse effects.
Cardioversion
Cardioversion
2 days of symptoms - check for clot
warfarin for 3 weeks
cardiovert
1 month post-cardioversion of treatment
emergent cardioversion
Heparin or LMWH bolus, cardiovert, treat with warfarin.
electrical ablation:
AIFFIRM 2002: rhythm control (cardioversion + antiarrhytmics) vs rate control (beta blocker plus digoxin). Very similar, but rate control appeared better.
Pulmonary vein ablation vs AV node ablation.
PVI: 6 months post, 80% AF-free.
Kahn et al. 2008. NEJM
AV-node ablaion and BVI:
- long-standing, persistent AF
- LA diameter 55-60
- bradycardia
- need for ICD
LA ablation
- absence of previous features
- paroxysmal AF
Anticoagulation
Everyone should be on anticoagulation, but medication depends on risk of stroke.
Low risk - ASA 81mg; med/high risk - warfarin INR 2-3; target 2.5.
CHADS2 score (low risk =0 med=1 high>2)
- congestive heart failure
- hypertension
- age >75 years
- diabetes
- stroke (2 points)
Other high risk factors: mitral stenosis, prosthetic valve.
Consequences and Course
The thromboemboli are bigger for A-Fib.
can cause atrial thrombus in appendage.
can also get tachycardia-induced cardiomopathy
The Case of...
Case #2 - a small story wrapping it all up and asking especially about management.
Additional Resources
Topic Development
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