Spontaneous or intended conversion of atrial fibrillation (AF) to sinus rhythm is associated with a short-term increase from baseline risk of clinical thromboembolism. This topic will discuss strategies that attempt to decrease this risk for patients who are not receiving long-term antithrombotic therapy.
The modalities used to perform cardioversion, long-term anticoagulation in patients with AF, and an overview of the management of AF are presented separately. (See "Atrial fibrillation: Cardioversion to sinus rhythm" and "Atrial fibrillation: Anticoagulant therapy to prevent embolization" and "Overview of atrial fibrillation".)
EXTREMELY HIGH-RISK PATIENTS
Patients with atrial fibrillation and valvular heart disease, especially rheumatic heart disease/mitral stenosis and prosthetic heart valves, are at extremely high risk of thromboembolization at all times, not just at the time of cardioversion. The approach to anticoagulation in such patients is discussed in other UpToDate topics. (See "Overview of the management of chronic mitral regurgitation", section on 'Anticoagulation' and "Medical management and indications for intervention in mitral stenosis", section on 'Prevention of thromboembolism' and "Antithrombotic therapy in patients with prosthetic heart valves".)
RATIONALE FOR ANTICOAGULATION
All patients with atrial fibrillation (AF) have an increased risk of embolization compared to those without. (See "Risk of embolization in nonvalvular atrial fibrillation", section on 'Incidence of embolism'.)
There is an incremental increase from the baseline risk in the immediate post-cardioversion period, whether planned or spontaneous. Most embolic events occur within 10 days of cardioversion . Patients undergoing cardioversion of AF of more than 48 hours duration represent a particularly high-risk group (compared to AF of shorter duration), with an embolic risk from as low as 1 to as high as 5 percent in the first month in the absence of anticoagulation [2-4]. This rate is substantially higher than the rate that would be calculated for the general population of patients with AF, in whom the yearly rate is between 1.3 and 5.1 (or higher) percent, depending on age and additional comorbidities. (See "Risk of embolization in nonvalvular atrial fibrillation", section on 'Incidence of embolism'.)