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NCT Number: NCT07002450

Left Atrial Imaging Prior to Cardioversion: Leveraging Computed Tomography to Rule Out Thrombus in The Emergency Department (LA CLOTTED)

The goal of this randomized clinical trial is to learn whether patients with symptomatic atrial fibrillation or atrial flutter (AF) who require heart imaging to rule out a blood clot before cardioversion would benefit from cardiac computed tomography angiography (CCT) in the emergency department (ED) compared to current standard of care management.

This will be a multicenter trial evaluating whether CCT-facilitated cardioversion in the ED reduces hospital admission, reduces repeat presentations to hospital and improves patient quality of life compared to the current standard of care.

Participants will undergo CCT-facilitated cardioversion or be treated according to current standard of care while in the ED and complete quality of life questionnaires in the ED and follow-up at 30 days.

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Key information

Conditions

Atrial Fibrillation (AF) Arrhythmias, Cardiac Atrial Fibrillation Atrial Flutter Cardiovascular Diseases Heart Diseases Pathologic Processes Pathological Conditions, Signs and Symptoms

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

The Ottawa Hospital Civic Campus, Ottawa, Ontario, Canada

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About this study

Atrial fibrillation and atrial flutter (AF) are the most common cardiac arrhythmias worldwide resulting in frequent visits to the emergency department (ED). Some patients can undergo chemical or electrical cardioversion to restore their heart back to a sinus rhythm. However, if a patient is not on blood thinners and the duration of AF is prolonged then blood clots may form in the heart increasing the risk of stroke after cardioversion. Therefore, some patients must undergo heart imaging to rule out any blood clots before cardioversion is considered safe. Transesophageal echocardiography (TEE) is commonly used to rule out blood clots, but it is not readily available in all EDs often resulting in hospital admission to facilitate this test or deferring cardioversion until 3 weeks of blood thinners have been completed.

Cardiac computed tomography angiography (CCT) is a more readily available alternative to TEE that can be done rapidly in the ED. CCT has excellent sensitivity and specificity compared to TEE for identifying cardiac thrombus. If there is no thrombus detected on the CCT then patients could be immediately cardioverted to sinus rhythm thus avoiding an unnecessary hospital admission and reducing the symptom burden associated with remaining in AF.

This study is a multicenter randomized trial that will evaluate the effectiveness of using CCT facilitated cardioversion in the ED compared to current standard of care management.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Age ≥18 years old; and
  • Primary symptomatic AF without a reversible underlying cause (e.g. sepsis, pneumonia, pulmonary embolism, hyperthyroidism)
  • LA imaging required before cardioversion according to local clinical practice guidelines

Exclusion criteria

  • Patients with an indication for emergency cardioversion (e.g. hemodynamic instability (systolic blood pressure<90mmHg or signs of shock), cardiac ischemia (ongoing severe chest pain or marked ST depression on ECG >2mm), or pulmonary edema (significant dyspnea, crackles, or hypoxia)); or
  • Contraindication to CCT (renal insufficiency (eGFR< 45ml/min/1.73m2), allergy to intravenous contrast agents, pregnancy (contraindications to radiation exposure), or inability to perform 20-second breath-hold)

Treatment and study plan

Cardiac Computed Tomography Angiography

Diagnostic Test

Patients will undergo CCT according to the following protocol. A non-contrast enhanced prospective ECG-triggered image will be acquired followed by a contrast-enhanced prospective ECG-triggered image using a tri-phasic contrast protocol. Delayed CT images 60 seconds after the initial contrast-enhanced CT scan will be obtained. Cardiac CT image interpretation will be performed according to routine clinical practices in a pragmatic fashion. The LA will be assessed for filling defects and characterized based upon attenuation values. If LA thrombus cannot be excluded, filling defects will be assessed on the delay images. Increases in attenuation would be consistent with pseudo-thrombus from 'slow flow' and 'incomplete opacification'. Areas where attenuation does not change significantly (persistent filling defect) will be diagnosed as thrombus. If the CCT shows no LA thrombus then the ED physician will be able to perform electrical and/or chemical cardioversion at their discretion.

Standard of care management

Other

Patients in the standard of care arm may undergo any combination of the following management strategies in the emergency department (ED) at the discretion of their treating physician:

  • Transesophageal echocardiogram (TEE) facilitated cardioversion; 2. Rate control; 3. Consultation with inpatient cardiac specialist for assessment/management and consideration of hospital admission; 4. cardioversion after 3 weeks of anticoagulation; and/or 5. Outpatient referral to cardiac specialist or general practitioner for further management.

Primary outcomes

  1. Primary composite outcome

    Time frame: Randomization to 30 days

    Using a hierarchical win ratio:

    • All-cause death
    • Stroke, transient ischemic attack, or systemic embolism
    • Admission to hospital for a cardiac or AF related reason
    • Repeat presentation to hospital for a cardiac or AF related reason
    • Improvement in AF Effect On Quality-Of-Life Questionnaire (AFEQT) quality of life greater than or equal to 5 points

Secondary outcomes

  1. Composite objective outcomes

    Time frame: Randomization to 30 days

    Using a hierarchical win ratio:

    • All-cause death
    • Stroke, transient ischemic attack, or systemic embolism
    • Admission to hospital for a cardiac or AF releated reason
    • Repeat presentation to hospital for a cardiac or AF related reason

  2. All-cause death

    Time frame: Randomization to 30 days

    Death from any cause

  3. Cardiovascular death

    Time frame: Randomization to 30 days

    Death due to a cardiovascular cause

  4. Stroke, transient ischemic attack, or systemic embolism

    Time frame: Randomization to 30 days

    Stroke is defined as a central nervous system infarction of the brain, spinal cord, or retina in a vascular distribution based on pathologic, imaging, or clinical evidence with symptoms persisting for ≥24 hours or until death.

    Transient ischemic attack is defined as a transient episode of neurologic dysfunction due to focal brain, spinal cord, or retinal ischemia without acute infarction or tissue injury.

    Systemic embolism is defined as an abrupt vascular insufficiency associated with clinical or radiologic evidence of arterial occlusion in the absence of other likely mechanisms.

  5. Hospital admission for a cardiac or AF related reason

    Time frame: Randomization to 30 days

    To count as a hospital admission for a cardiac or AF related reason it should meet the following criteria:

    • Duration of admission should exceed 24 hours; AND
    • Admission is due to the following reasons:
    • Admission at index hospital presentation:
    • Heart rate>100bpm at rest or >110bpm with ambulation despite a trial of rate control; or
    • Complication related to the treatment of AF (including significant incidental findings on CCT leading to admission)
    • Admission at subsequent hospital presentation:
    • Hospitalization due to a cardiac reason such as heart failure, syncope, palpitations/arrhythmia, angina or acute coronary syndrome

  6. Repeat presentation to the emergency department

    Time frame: Randomization to 30 days

    Repeat presentation to the emergency department due to a cardiac reason such as heart failure, syncope, palpitations/arrhythmia, angina or acute coronary syndrome

  7. AFEQT quality of life

    Time frame: Randomization to 30 days

    Change in AF Effect On Quality-Of-Life Questionnaire (AFEQT) quality of life The AFEQT is a 20-item, self-administered instrument that quantifies symptoms, daily activities, treatment concern, and treatment satisfaction. Scores are transformed to a range from 0-100, in which higher scores reflect better health status.

  8. SF-36 quality of life

    Time frame: Randomization to 30 days

    Change in 36-Item Short Form Health Survey (SF-36) quality of life. The SF-36 questionnaire consists of eight scales yielding two summary measures: physical and mental health. The mental health measure is composed of vitality (4 items), social functioning (2 items), role-emotional (3 items), and mental health (5 items). Scores are transformed to a range of 0-100, in which higher scores reflect better health status.

  9. Bleeding

    Time frame: Randomization to 30 days

    Bleeding events as defined by the Bleeding Academic Research Consortium

  10. Admission to hospital for acute kidney injury

    Time frame: Randomization to 30 days

    Definition of acute kidney injury according to the Kidney Disease Improving Global Outcomes:

    • Increase in SCr by ≥ 0.3 mg/dl (≥ 26.5 µmol/l) within 48 hours; or
    • Increase in SCr to ≥ 1.5 times baseline, which is known or presumed to have occurred within the prior 7 days; or
    • Urine volume <0.5 ml/kg/h for 6 hours

  11. Length of stay in the emergency department

    Time frame: From time of arrival until time of discharge or admission (approximately 3 hours)

    Length of stay in emergency department in minutes, from time of arrival to time of discharge or admission

  12. Normal sinus rhythm

    Time frame: Randomization to 30 days

    Being in normal sinus rhythm at the 30 day follow up. Heart rhythm will be determined by electrocardiography.

Other outcomes

  1. Cost effectiveness

    Time frame: Emergency department presentation to 30 days

    Cost effectiveness between CCT strategy and standard of care

Study contacts

Contact information is provided by the study sponsor or research team.

Farrah Ahmed

CONTACT

[email protected]

613-696-7000 ext. 12697

Yeung Yam

CONTACT

[email protected]

613-696-7000 ext. 19703

Sponsors and collaborators

Lead sponsor

Ottawa Heart Institute Research Corporation

Other

Registry information

Acronym: LA CLOTTED

Important dates

Study start
2025
Primary completion
2028
Study completion
2028
First posted
Jun 3, 2025
Registry last updated
Jun 9, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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