Fibrilacion Atrial (1)

8/6/2019 Fibrilacion Atrial (1)

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Atrial Fibrillation

BASIC INFORMATIONDEFINITION

Atrial fibrillation (AF) is chaotic atrial activity caused by simultaneous discharge of multiple

atrial foci because of multiple reentrant circuits.

SYNONYMS

AF

A-fib

ICD-9CM CODES

427.31 Atrial fibrillation

EPIDEMIOLOGY & DEMOGRAPHICS

The prevalence of AF increases with age, from 0.1% in adults


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Structural cardiac disease: pericarditis, myocarditis, cardiomyopathy, congestive

heart failure, coronary artery disease, myocardial infarction, congenital heartdisease (especially those that lead to atrial enlargement such as atrial septal

defect), tachycardia-bradycardia syndrome

Arrhythmias: atrial tachycardia, Wolff-Parkinson-White syndrome

Endocrine: thyrotoxicosis, hyperthyroidism or subclinical hyperthyroidism,

pheochromocytoma

Surgery: both cardiac and noncardiac

Electrolytes: hypokalemia, hypomagnesemia

Systemic stress: fever, anemia, hypoxia, sepsis, infections (e.g., pneumonia)

Medications/toxins: digitalis, adenosine, theophylline, amphetamines, cocaine,antihistamines, alcohol abuse and/or withdrawal, caffeine

DIAGNOSISDIFFERENTIAL DIAGNOSIS

Multifocal atrial tachycardia

Atrial flutter

Frequent atrial premature beats

WORKUP

New-onset AF: ECG, echocardiogram, Holter monitor (selected patients), and laboratory

evaluation

LABORATORY TESTS

Thyroid-stimulating hormone, free T4

Serum electrolytes

Toxicity screen

IMAGING STUDIES

ECG (see Fig. 1-33 for atrial flutter and fibrillation)

Absence of P waves

Fibrillatory or f waves at the isoelectric baseline with varying amplitude,

morphology, and intervals

Irregular ventricular rate

Echocardiography to rule out structural heart disease (evaluate ventricular size,

thickness, and function, atrial size, and valve function)

Holter monitor: useful only in selected patients to evaluate paroxysmal AF

TREATMENT


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NONPHARMACOLOGIC THERAPY

Avoidance of alcohol in patients with suspected excessive alcohol use

Avoidance of caffeine and nicotine

Treatment of underlying source/cause, if any found

The Maze surgical procedure, with its recent modifications creating electricalbarriers to the macroreentrant circuits that are believed to underlie AF, is being

performed with good results in several medical centers (preservation of sinusrhythm in >95% of patients without the use of long-term antiarrhythmic

medication). Clear indications for its use remain undefined. In general, surgery isreserved for patients with rapid heart rate refractory to pharmacologic therapy or

those who cannot tolerate pharmacologic therapy.

Pulmonary vein ablation for chronic AF: Sinus rhythm can be maintained longterm in the majority of patients with chronic AF by circumferential pulmonary

vein ablation, independently of the effects of antiarrhythmic drug therapy,cardioversion, or both. The American College of Cardiology/American Heart

Association/European Society of Cardiology (ACC/AHA/ESC) guidelines statethat catheter ablation is a reasonable alternative to medical therapy to prevent

recurrent AF in symptomatic patients in the absence of significant left atrialenlargement (class 2A recommendation).

ACUTE GENERAL Rx

New-onset AF:

If the patient is hemodynamically unstable (hypotension, congestive heart failure

or angina), perform synchronized cardioversion after immediate conscioussedation with a rapid short-acting sedative (e.g., midazolam). The likelihood of

cardioversion-related clinical thromboembolism is low in patients with AF lasting2 days have a 5% to 7% risk for clinical

thromboembolism if cardioversion is not preceded by several weeks of warfarintherapy. However, if transesophageal echocardiography reveals no atrial

thrombus, cardioversion may be performed safely after anticoagulation has beenachieved. Anticoagulant therapy should be continued for at least 1 mo after

cardioversion to minimize the incidence of adverse thromboembolic events. It canbe stopped as long as AF has not recurred.

If the patient is hemodynamically stable, a rate-control strategy is typically

pursued initially. Treatment options include the following:

1. Diltiazem 0.25 mg/kg (maximum of 25 mg) given intravenously (IV)over 2 min followed by a second dose of 0.35 mg/kg (maximum of 25mg) 15 min later if the rate is not slowed to


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can be changed to oral diltiazem 60 to 90 mg q4-6h.

2. Verapamil 2.5 to 5 mg IV initially, then 5 to 10 mg IV 10 min later if the

rate is still not slowed to


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undergo anticoagulation, low-dose aspirin is an appropriate alternative in these

patients.

For patients in whom anticoagulation with warfarin is contraindicated, aspirin plusclopidogrel has been shown to be of similar benefit in reducing thromboembolic

events as warfarin (Coumadin) with a similar bleeding risk.

DISPOSITION

Factors associated with maintenance of sinus rhythm after cardioversion include:

Left atrium diameter


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Both transesophageal echocardiography with short-term prior anticoagulation

followed by early acute cardioversion (in absence of intracardiac thrombus) withpostcardioversion anticoagulation vs. delayed cardioversion with

preanticoagulation and postanticoagulation are appropriate management strategiesfor patients who elect to undergo cardioversion.

EVIDENCE

There is evidence for similar mortality and cardiovascular morbidity in olderasymptomatic patients with chronic AF treated with either a rate-controlling therapy

or rhythm-controlling therapy.

Five randomized controlled trials have found similar mortality rates between

asymptomatic patients with rate-controlled vs. rhythm control chronic AF.[[1]]

Warfarin is effective for both the primary and secondary prevention of ischemicstroke and TIA in patients with chronic AF. General recommendations are as

follows:

In people with persistent or intermittent AF with a CHADS2 score of 2,

anticoagulation with an oral vitamin K antagonist, such as warfarin, isrecommended (target international normalized ratio, 2.5; range, 2.0 to 3.0).

[[2]]

In people with persistent or intermittent AF with a CHADS2 score of 1,

anticoagulation with either an oral vitamin K antagonist, such as warfarin, oraspirin therapy is recommended.

[[2]]

Primary prevention of stroke in patients at high risk:

Adjusted-dose warfarin is significantly more effective than placebo in reducingthe risk for stroke in people at high risk for stroke.

[[3]]

Adjusted-dose warfarin is significantly more effective than aspirin in reducingthe risk for ischemic stroke or systemic embolism in patients at high risk for

stroke.[[3]]

Primary prevention of stroke in patients at lower risk:

Adjusted-dose oral anticoagulation is significantly more effective than placebo

in reducing overall stroke, disabling or fatal stroke, and death in patients withnonvalvular AF and no prior history of strokes or TIA. The combined end

point of all stroke, myocardial infarction, or vascular death was also reduced.The observed rates of intracranial and extracranial hemorrhage were not

significantly increased, but confidence intervals were wide.[[4]]


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Secondary prevention of stroke:

Anticoagulants are significantly more effective than antiplatelet therapy in

reducing all vascular events and also recurrent stroke in patients with

nonrheumatic AF and a history of minor ischemic stroke or TIA. The risk formajor extracranial bleeds, but not intracranial bleeds, appears to be increasedin patients on anticoagulants.

[[5]]

Dronedarone is a newer, recently approved agent that is pharmacologicallysimilar to amiodarone with less toxicity. A recent multicenter, double blind

trial showed that dronedarone was more effective than placebo in maintainingnormal sinus rhythm

[[6]]and in reducing cardiovascular events.

[[7]]However,

dronedarone is not indicated in patients with severe heart failure and leftventricular systolic dysfunction (ejection fraction

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