Atrial Fibrillation, You’re a Heart Breaker, Dream Maker, Love Taker:

But At Least There is Low Risk for Thromboembolic Events With Speedy Conversion to Sinus Rhythm…

This post reviews the article from Weigner, Marilyn et al. “Risk for Clinical Thromboembolism Associated with Conversion to Sinus Rhythm in Patients with Atrial Fibrillation Lasting Less Than 48 Hours,” from the Annals of Internal Medicine in 1997 as part of the ongoing 52 article series.

Main Points:

  1. This article reveals only a 0.8% risk of clinical thromboembolic event for patients who were clinically estimated to be in atrial fibrillation for less than 48 hours.
  1. This trial data supports the recommendation for early cardioversion, either pharmacologic or through electric cardioversion, in patients with recent onset of symptoms without the need for prior diagnostic imaging to evaluate for clot burden.


Atrial fibrillation is a common arrhythmia and responsible for over 250,000 hospital admissions annually. Patients often feel the effects of depressed cardiac output from the loss of atrial systole and seek medical attention in hopes of improved quality of life. Patients may describe a range of symptoms including palpitations, dyspnea, dizziness, angina and fatigue. Studies have demonstrated that patients with atrial fibrillation for more than two days may have a greater than five percent risk of clinical thromboembolism and often require weeks of anticoagulation or screening with transesophageal echocardiography prior to cardioversion. This study sought to answer the question of whether or not patients who experienced only a short duration of symptoms were low risk for thromboembolic disease.


This was a prospective study of consecutive patients at two academic medical centers, Beth Israel Deaconess Medical Center in Boston, MA and the John Dempsey Hospital and University of Connecticut Health Center in Farmington, CT. 1822 adult patients with a diagnosis of atrial fibrillation were screened and 375 patients who were clinically estimated to have symptoms for less than 48 hours were enrolled. Those patients whose duration of symptoms were unclear or had already initiated long term anticoagulation with warfarin were excluded. Patients with a previous history of thromboembolic events were not excluded, but one patient who had an acute thromboembolism was not enrolled in the trial. Clinical and transthoracic echocardiography data and outcomes were collected from review of the medical records. Clinical embolic events were considered if they occurred during the index hospitalization or within one month after conversion to sinus rhythm. Conditions that may have predisposed patients to atrial fibrillation included: previous history of atrial fibrillation (181 patients, 48.3%), hypertension (156, 41.7%), coronary artery disease (114, 30.4%), infection (25, 6.7%), history of thromboembolism (23, 6.1%), excessive alcohol use (22, 5.9%), rheumatic heart disease (7, 1.9%). Patients were noted to have left atrial dimensions of 4.2 +/- 0.7cm (normal ≤ 4.0cm) and a left atrial length of 5.7 +/- 0.7cm (normal ≤ 5.2cm) based on transthoracic echocardiogram data. 218 out of 280 patients who had echocardiograms performed were noted to have at least some evidence of mitral valve regurgitation with 61 patients noted to have either moderate or severe regurgitation.

Patients converted back to a normal sinus rhythm either spontaneously or through pharmacologic or electric cardioversion methods. Conversion was considered spontaneous if it occurred without the use of medications or electricity or in the setting of use of ventricular rate-controlling agents (digoxin, beta-blockers, and calcium channel blockers).

Three patients (0.8%, 95% CI 0.2-2.4) were noted to have a clinically significant thromboembolism and surprisingly all converted spontaneously. The cases included a left parietal embolic stroked in an 86 year old female with history of hypertension; a right proximal brachial artery embolus in an 83 year old female with coronary artery disease; and a transient ischemic attack in an 89 year old female with a recent diagnosis of pneumonia.

This study was a consecutive series that relied on both real time data gathering as well as retrospective chart review.

Level of Evidence:

This study was graded a level II based on the ACEP Clinical Policy Grading Scheme for prognostic questions and had only minimal methodological flaws.


The three patients in this trial were identified as having increased risk for thromboembolism based of the Stroke Prevention and Atrial Fibrillation Study I and II, however, how best to achieve post conversion anticoagulation in the era of direct oral anticoagulants remains a hot topic for further study and debate.

Relevant articles:

Mookadam, M. Shamoun FE. Mookadam, F. “Novel Anticoagulants in Atrial Fibrillation: A Primer for the Primary Physician.” J Am Board Fam Med, 2015, 28(4):510-22

Source Articles:

Weigner, M. Caulfield, T. Danias, P. et al. “Risk for Clinical Thromboembolism Associated with Conversion to Sinus Rhythm in Patients with Atrial Fibrillation Lasting Less Than 48 Hours.” Annals of Internal Medicine, 1997, (126):615-20.

Faculty Reviewer: Dr. Siket

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