A quick review of common conditions, using the best global evidence

Dr. Alper is research assistant professor of family and community medicine at University of Missouri-Columbia and editor-in-chief of DynaMed (www.dynamicmedical.com), a database of comprehensive updated summaries covering more than 1,800 clinical topics.  Dr. Garvin is associate clinical professor of family medicine at University of Washington-Family Medicine Spokane and a reviewer
for DynaMed.

From the August 2005 issue of Cortlandt Forum


Prevalence
• 1% of U.S. population
• Prevalence increases with age from 0.1% at age 20-55 years to 9% after age 80.

ICD-9 codes
• 427.31 atrial fibrillation (AF)

Etiology
• Cardiac abnormalities
     — Structural, e.g., left atrial enlargement, valvular heart disease, cardiomyopathy,
         atrial septal defect, atrial tumors
     — Conduction, e.g., Wolff-Parkinson-White syndrome, sick sinus syndrome
     — Functional abnormalities, e.g., rheumatic heart disease, pericarditis,
         myocarditis, MI
     — Conditions that stress cardiac function, e.g., hypertension, coronary heart
         disease, pulmonary embolism
• Metabolic causes, e.g., hypoxemia, hypokalemia, hypomagnesemia, hypercalcemia, carbon monoxide poisoning
• Drugs, e.g., theophylline, albuterol, tricyclic antidepressants, digoxin, atropine, sympathomimetics, adenosine, nicotine, alcohol, caffeine, heroin
• Transient hyperadrenergic state, e.g., post surgery, anemia, infection, fever, stress, hyperthyroidism, volume depletion
• Idiopathic

Making the diagnosis
• ECG showing no ordered atrial contraction (no P waves), typically irregularly irregular ventricular rate

Rule out
• Sinus tachycardia
• Other irregular narrow-complex tachyarrhythmias
• Computer error: computers incorrect in 35% of patients, often due to electrical artifacts or atrial premature beats

Tests to order
• ECG
• Echocardiography
     — To evaluate left atrial size, valvular heart disease, presence of thrombi
     — Transesophageal echocardiography (TEE) may be used to determine if
         immediate cardioversion is safe.
• Thyroid function tests

Complications
• Systemic embolization (from atrial thrombus)
• Congestive heart failure
• Coronary ischemia (if there is CAD)
• Stroke (4.5% annual incidence in untreated patients)
     — Risk of embolic stroke dependent on many factors
     — Most accurate risk score: CHADS2 [Congestive heart failure, Hypertension,
         Age >75 years, Diabetes = 1 point each; Stroke or transient ischemic attack =
         2 points]
     — Risk of stroke (per 100 patient-years)
     ▪ 1.9 if CHADS2 score = 0
     ▪ 2.8 if CHADS2 score = 1
     ▪ 4 if CHADS2 score = 2
     ▪ 5.9 if CHADS2 score = 3
     ▪ 8.5 if CHADS2 score = 4
     ▪ 12.5 if CHADS2 score = 5
     ▪ 18.2 if CHADS2 score = 6
     — Other risk factors: vascular disease, smoking, female sex

Treatment
• Specific goals of individualized treatment may include:
     — Thromboembolic prophylaxis (anticoagulation or antiplatelet therapy)
     — Symptom control
     — Conversion to sinus rhythm (cardioversion)
     — Heart-rate control
     — Rhythm control (maintenance of normal sinus rhythm)
• Hospital admission may not be necessary for all patients.
• Thromboembolic prophylaxis
     — Use of warfarin should be based on risk of stroke, risk of bleeding, and
         patient’s values and preferences.
     — Warfarin more effective than aspirin for stroke prophylaxis but associated with
        greater risk for bleeding; warfarin clearly preferred for patients with high risk for
        stroke and no contraindications
     — Choice of warfarin vs. aspirin vs. no treatment with low stroke risk is
         controversial; aspirin efficacy controversial
• Cardioversion
     — Spontaneous cardioversion likely in cases due to hyperadrenergic state when
         underlying condition eliminated
     — Interventional cardioversion may not be warranted in patients with enlarged left
         atrium (>5 cm) because of lower success rates and higher recurrence rates.
     — Electrical (synchronous direct current) cardioversion safest and most effective
         approach
     — Drug-induced cardioversion
     ▪ In general, use medications only if patient is symptomatic, because of risks with
      therapy.
     ▪ Most effective: ibutilide, dofetilide, flecainide
     ▪ Other effective agents: propafenone, amiodarone
     ▪ Ineffective: digoxin, beta blockers, calcium channel blockers
     ▪ Agents with inadequate study data: disopyramide, procainamide
     — Standard of care for AF of >48-72 hours’ duration
     ▪ Anticoagulation for three weeks before cardioversion
     ▪ Cardioversion
     ▪ Continued anticoagulation for four weeks following cardioversion
     — Alternative approach using TEE allows immediate heparin and cardioversion for
     patients with no active thrombus on TEE 12-24 hours later.
     — Need for anticoagulation with AF <48 hours’ duration controversial
• Rate-control strategies
     — Verapamil, diltiazem, or beta blocker is first choice to slow ventricular
     response.
     — Digoxin is an alternative choice but does not control rate during exercise.
     — Amiodarone also slows rate in AF.
• Rhythm-control strategies
     — No more effective than rate-control strategies and associated with increased
     morbidity and cost
     — Rhythm control should be considered for patients who return to AF after
     cardioversion and whose symptoms persist despite rate control.
     — Prior reasoning for rhythm control was avoidance of anticoagulation, but recent
     evidence shows that intermittent atrial fibrillation (and risk of stroke) still occurs on
      antiarrhythmic agents.
• Radiofrequency catheter ablation associated with improved survival and quality of life compared with anti-arrhythmic therapy, based on limited evidence

Prevention
• Interventions shown to prevent postoperative AF after heart surgery include amiodarone, beta blockers, sotalol and pacing.

See www.dynamicmedical.com for references.