Atrial Fibrillation

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Contents 1 More Specific Terms 2 Introduction 3 Etiology 4 Epidemiology 5 Pathology 6 Genetics 7 Clinical-manifestations 8 Laboratory 9 Diagnostic-procedures 10 Complications 11 Differential-diagnosis 12 Management 13 More General Terms 14 Additional Terms 15 Internet Database 16 References

More Specific Terms

• paroxysmal atrial fibrillation (PAF)

Introduction

• AF may be paroxysmal (intermittent) or persistent.

Etiology

• hypertension
• acute alcohol ingestion (holiday heart syndrome)
• ischemic heart disease
• myocardial infarction
• congestive heart failure
• valvular heart disease
• pericarditis
• sick sinus syndrome [6]
• pulmonary disease

• pulmonary embolus
• pneumonia
• chronic obstructive pulmonary disease ( COPD)

• s/p open heart surgery
• theophylline intoxication
• endocrinopathies

• hypothyroidism
• hyperthyroidism
• pheochromocytoma

• infections
• cardiac tumors: atrial myxoma [6]
• risk factors - [23]

• obesity
• diabetes mellitus
• high pulse pressure
• advanced age
• long-term endurance exercise (2-10 fold risk) [30] due to left atrial enlargement
• long-term glucocorticoids, as little as 7.5 mg of prednisone/day [33]
• chronic renal failure (HR=3.2 GFR <30 ml/min/1.73 m2)

• albuminuria [39]

• NSAID & COX2 inhibitors (HR=1.2-1.3; HR=1.5-1.7 for new users) [40]

Epidemiology

• most common sustained arrhythmia
• affects 10-19% of Americans over age 75
• > 98% of patients have comorbidity

Pathology

• multiple simultaneous wandering wave fronts of activation with simultaneously occurring reentrant circuits within the atria
• any disease process that increases atrial size ( left atrial enlargement) &/or decreases atrial conduction or refractory period may result in AF
• the pulmonary veins have been implicated in generating the electrical current of AF [19]
• atrial fibrillation may induce atrial cardiomyopathy [6]
• resultant atrial cardiomyopathy promotes further atrial fibrillation

Genetics

• familial atrial fibrillation associated with defect in: LMNA, KCNQ1, KCNE2

Clinical-manifestations

• may be asymptomatic
• palpitations
• irregular heart rate
• dizziness
• dyspnea
• angina
• syncope
• heart failure
• systemic embolism
• no A wave in jugular venous pulse
• pulse deficit ( auscultated pulse > palpated pulse, especially radial artery)
• variable S1 heart sound

Laboratory

• thyroid function tests
• theophylline level if indicated
• urinary metanephrines if indicated
• pulse oximetry
• digoxin level if possible exposure

Diagnostic-procedures

• electrocardiogram

• irregularly fluctuating baseline: atrial rate 350-600 bpm
• no P waves

• deformed T waves or ST segment may hide P waves

• irregular spacing of R waves

• echocardiogram

• rule out valvular heart disease, i.e. mitral stenosis
• assess left atrial size: an enlarged left atrium is unlikely to maintain sinus rhythm if cardioverted

Complications

• rapid ventricular response
• thromboembolism (see risk factors for thromboembolism)

• the majority of thromboembolic strokes occur in association with AF
• stroke risk is 4%/year for untreated patients
• stroke risk for patients on aspirin alone

• 2%/year for low risk patients
• 4%/year with for any risk factor
• as high as 18%/year for high risk patients

• > 90% of atrial thrombi in patients with non-valvular atrial fibrillation are believed to originate in the left atrial appendage

• potentially serious complications with

• Wolf-Parkinson-White syndrome
• aortic stenosis or mitral stenosis

• need for atrial kick to maintain cardiac output

• diastolic dysfunction

• non compliant ventricle, impaired ventricular filling
• cardiovascular collapse with rapid ventricular response
  

• disease interaction(s) of atrial fibrillation with mitral stenosis
• disease interaction(s) of heart failure with urinary incontinence
• disease interaction(s) of obstructive sleep apnea (OSA) with heart failure

Differential-diagnosis

• multifocal atrial tachycardia in COPD
• digitalis toxicity - atrial tachycardia with AV block
• preexitation tachycardia
• ventricular tachycardia

• AF may appear as wide-complex tachycardia if intraventricular conduction delay ( RBBB)

Management

• general [5,12]

• hospitalize for

• hemodynamically unstable, prepare for cardioversion
• high risk for thromboembolism

• immediate anticoagulation with heparin & warfarin [5]

• correct precipitating causes

• correct hyperthyroidism prior to cardioversion [7]

• cardioversion & maintenance of sinus rhythym

• DC cardioversion (50, 100, 200, 300, 360 joules)

• more effective than chemical cardioversion [44]

• chemical cardioversion

• pharmacologic agents

• class 1A, 1C or 3 antiarrhythmic agents

• conversion & maintenance of sinus rhythm

• indications

• patient is unstable
• mitral stenosis
• mitral regurgitation
• new onset of atrial fibrillation within 48 hours

• contraindications:

• atrial thrombus: delay cardioversion until completion of 4-6 weeks of anticoagulation warfarin

• anticoagulation

• IV heparin prior to emergent cardioversion if duration of AF not known [5]
• 3 weeks prior to elective cardioversion

• if atrial fibrillation < 48 hours, then may proceed with cardioversion without prior anticoagulation [6]
• trans-esophageal echocardiography ( TEE) may be use to determine presence of atrial thrombosis; if none then may proceed with cardioversion without prior anticoagulation [6]

• continue for 4 weeks after successful cardioversion

• antiarrhythmic therapy for maintenance of sinus rhythm

• may or may not be needed
• class III agents

• amiodarone (most commonly used)

• 400 mg for 30 days, then 200 mg QD
• especially useful with structural heart disease
• 1st line agent for AF if ischemic heart disease & LV dysfunction [5]

• sotalol in patients with CAD
• dronedarone ( Multaq) [31]

• class 1C agents, if no structural heart disease

• flecainide 100 mg BID, or
• propafenone 150-225 mg TID

• 30-50% of patients will maintain sinus rhythm after 1-2 years
• PRN flecainide or sotalol for paroxysmal atrial fibrillation

• control ventricular rate via AV nodal blocking agents is generally the preferred strategy (excluding WPW)# [11,13]

• Ca+2-channel antagonists (NOT dihydropyridines)

• diltiazem, verapamil

• beta-blocker

• metoprolol, atenolol

• digoxin

• not very effective in controlling ventricular response during exercise
• add calcium channel antagonist or beta-blocker in patients controlled at rest, but with tachycardia during exercise
• do not use as single agent for rate control [5]

• lenient rate control (< 110/min) with outcomes similar to standard control (< 80/min) [36]

• anticoagulation [16] (see CHADS score)

• aspirin 325 mg PO QD

• patients < 60-75* years of age without risk factors (see Complications) [6]
• patients unable or unwilling to take warfarin

• chronic ( warfarin) - INR of 2.0-3.0 is therapeutic%

• see risk factors for thromboembolism
• reduces risk 50% [10] & lessens severity of stroke [9]

• 50% of patients benefit from anticoagulation [32]; patients with < 2 risk factors for stroke will not benefit
• risk of stroke on warfarin - 1.6%/year mean age 71 [10] - 2.6%/year mean age 81 [17]

• in elderly (> 75 years of age), stroke scores with poor predictive value [41]
• in elderly (> 75 years of age), risk of hemorrhage is high

• risk of major hemorrhage 10%/year
• risk of life-threatening hemorrhage 5%/year,
• risk of fatal hemorrhage 1%/year [17]

• increased risk of intracranial hemorrhage associated with INR > 3.5, age > 85
• reduces overall mortality 4.5 vs 5.3 per 100 person years [10]
• low risk of bleeding (2%), in elderly [25] <same as aspirin>
• risk scheme to predict warfarin-associated hemorrhage described in [43]

• thrombin inhibitor ( dabigatran) [8]

• FDA approved (2010) & included in guidelines for treatment of atrial fibrillation [38]
• no need for therapeutic monitoring ( INR)

• factor Xa inhibitor rivaroxaban not inferior to wafarin in preventing embolic stroke [42]
• clopidogrel no better than aspirin [19]
• clopidogrel + aspirin inferior to warfarin [24]
• clopidogrel + aspirin better than aspirin alone but associated with increased risk of GI bleed (see ACTIVE A trial) [29]

• left atrial appendage closure is an investigational procedure with promise for prevention of left atrial thromboembolism
• AV node ablation with permanent ventricular pacing

• refractory ventricular rate [27]

• radiofrequency ablation of focal atrial fibrillation in younger patients [35]
• radiofrequency ablation in connection with pulmonary vein isolation may become 1st line therapy [18,20,21,22,27]
• maze procedure may be useful for patients undergoing cardiac surgery for other reasons [5]
• cardiac pacemaker

• sick sinus syndrome accompanying AF
• symptomatic patients with paroxysmal AF

• * aspirin may not be effective in patients > 75 years of age
• # in patients with WPW, rhythm control is indicated; procainamide is the drug of choice (see Wolf-Parkinson-White syndrome)
•  % exception is rheumatic heart disease, INR=2.5-3.5 [5]

More General Terms

• supraventricular arrhythmia
• chronic cardiac arrhythmia

Additional Terms

• Atrial Fibrillation Follow-up Investigator of Rhythm Management (AFFIRM)
• Atrial Fibrillation Suppression Trial (AFIST)
• atrial flutter
• cardiac conduction system
• cardioversion
• pharmaceutical agents for treatment of atrial fibrillation
• risk factors for thromboembolism associated with atrial fibrillation
• Wolff-Parkinson-White (WPW) syndrome

Internet Database

OMIM: 607554

References

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atrial fibrillation (AF)