Atrial Fibrillation

Background

• Atrial fibrillation (AF) is a common supraventricular tachyarrhythmia caused by uncoordinated atrial activation and associated with an irregularly irregular ventricular response.
• Causes of atrial fibrillation include an underlying structural heart disease, metabolic disorders, endocrine diseases, and certain medications.
• The prevalence of AF is approximately 1%-2% in the general population of developed countries.
• Definitions of AF:
  • Paroxysmal AF is recurrent atrial fibrillation that terminates spontaneously, lasting possibly up to 7 days, but usually < 48 hours.
  • Persistent AF is atrial fibrillation that is sustained > 7 days, but < 1 year .
  • Longstanding persistent AF is atrial fibrillation that is persistent for > 1 year, and in which management of rhythm is being actively pursued.
  • Permanent AF refers to atrial fibrillation where the patient and physician agree to stop additional attempts to restore normal sinus rhythm because atrial fibrillation cannot be converted anymore.
  • Lone AF was used to describe paroxysmal, persistent, or permanenet atrial fibrillation in younger patients (such as patients < 65 years old) with no clinical history or echocardiographic evidence of cardiovascular disease, but the term has been abandoned due to its imprecision and lacking a standard definition.
• Patients with AF are at a significantly increased risk of heart failure and thromboembolism and, in particular, stroke.

Evaluation

• Suspect a diagnosis of atrial fibrillation (AF) on a physical exam when an irregularly irregular heart rhythm is detected by the palpation of a pulse or the auscultation of heart sounds.
• Obtain an electrocardiogram (ECG) to establish the diagnosis. Characteristic findings include:
  • rapid oscillatory ('fibrillatory') baseline waves varying in amplitude, shape, and timing
  • absence of P waves
  • irregularly irregular ventricular response
• An ambulatory electrocardiogram (Holter monitor, event monitor, loop monitor) may be needed to make the diagnosis.
• Obtain a transthoracic echocardiogram to assess cardiac chamber dimensions, left ventricular function, and to exclude valvular disease.
• Factors that contribute to the development of AF include the presence of chronic cardiac conditions such as hypertension, coronary heart disease, valvular heart disease, and other comorbid conditions such as sleep apnea, obesity, and diabetes mellitus.
• Assess the following factors in patients with AF to assist in the approach to management:
  • hemodynamic stability
  • concurrent cardiovascular symptoms such as shortness of breath or chest pain
  • identification of possible contributing factors
  • duration of atrial fibrillation

Management

• Immediate direct current (DC) electrical cardioversion of atrial fibrillation may be necessary for patients with hemodynamic instability and/or significant cardiovascular symptoms.
• Other specific treatment modalities include:
  • rate control of atrial fibrillation (AF)
  • rhythm control of AF
  • thromboembolic prophylaxis in AF
  • ablation therapy for AF

Prevention

• Offer beta blockers for patients undergoing cardiac surgery to prevent perioperative atrial fibrillation (Strong recommendation).
• Consider the following medications for the prevention of atrial fibrillation in patients with cardiovascular disease:
  • angiotensin-converting enzyme inhibitors or angiotensin receptor blockers (Weak recommendation)
  • statins, particularly in those with heart failure or who have had or are undergoing coronary artery bypass grafting surgery (Weak recommendation)