What is the recommended heparin regimen for unstable patients with atrial fibrillation or rapid atrial response undergoing cardioversion?

From the Guidelines

For unstable patients with atrial fibrillation or rapid atrial response undergoing cardioversion, heparin should be administered concurrently by an initial intravenous bolus injection followed by a continuous infusion in a dose adjusted to prolong the activated partial thromboplastin time to 1.5 to 2 times the reference control value, as recommended by the American College of Cardiology/American Heart Association Task Force on Practice Guidelines 1. The goal of heparin administration in this context is to reduce the risk of thromboembolism during and after cardioversion.

• The dose of heparin should be adjusted to achieve and maintain an activated partial thromboplastin time (aPTT) of 1.5 to 2 times the reference control value.
• Thereafter, oral anticoagulation (INR 2.0 to 3.0) should be provided for at least 4 weeks, as for patients undergoing elective cardioversion.
• Limited data support subcutaneous administration of low-molecular-weight heparin in this indication. The use of heparin in unstable patients undergoing cardioversion is supported by guidelines from the American College of Cardiology/American Heart Association Task Force on Practice Guidelines 1, which emphasize the importance of anticoagulation in preventing thromboembolic events in patients with atrial fibrillation. Additionally, the 2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation also recommends anticoagulation with heparin or other agents for patients undergoing cardioversion 1.
• For patients with AF of more than 48-h duration requiring immediate cardioversion because of hemodynamic instability, heparin should be administered concurrently.
• For patients with AF of less than 48-h duration associated with hemodynamic instability, cardioversion should be performed immediately without delay for prior initiation of anticoagulation.

From the Research

Heparin Regimen for Unstable Patients with Atrial Fibrillation or Rapid Atrial Response Undergoing Cardioversion

• The recommended heparin regimen for unstable patients with atrial fibrillation or rapid atrial response undergoing cardioversion depends on the cardioembolic risk 2, 3.
• For patients with atrial fibrillation of > or = 48 h or of unknown duration undergoing pharmacological or electrical cardioversion, immediate anticoagulation with unfractionated IV heparin, or low-molecular-weight heparin (LMWH), or at least 5 days of warfarin by the time of cardioversion (achieving an INR of 2.0-3.0) is recommended, as well as a screening multiplane transesophageal echocardiography (TEE) 2.
• If no thrombus is seen on TEE, cardioversion is successful, and sinus rhythm is maintained, anticoagulation for at least 4 weeks is recommended 2.
• For patients with atrial fibrillation of known duration <48 h, cardioversion without prolonged anticoagulation may be considered, but in patients without contraindications to anticoagulation, beginning IV heparin or LMWH at presentation is suggested 2.
• The use of an expedited heparin anticoagulation regimen in patients with atrial fibrillation or atrial flutter undergoing transesophageal echocardiography-guided cardioversion appears to be safe, with cardioversion possible as early as a few hours after initiation of intravenous unfractionated heparin, and bridging therapy with a low-molecular-weight heparin can be used after cardioversion until the international normalized ratio is therapeutic 4.
• Direct oral anticoagulants are the first-line medication class for anticoagulation in patients with atrial fibrillation, and several tools (e.g., CHA2DS2-VASc) are available to assist with this decision 5.