A Transesophageal Echocardiogram (TEE) is necessary before electrical cardioversion to ensure patient safety. Cardioversion delivers a controlled electrical shock to reset an irregular rhythm, most commonly Atrial Fibrillation (AFib), back to a normal sinus rhythm. While effective, this procedure carries a risk of causing a stroke. The primary goal of the TEE is to confirm the heart is clear of pre-existing blood clots, minimizing the potential for complications.
Why Cardioversion Poses a Stroke Risk
The risk of stroke is directly related to Atrial Fibrillation (AFib). In AFib, the heart’s upper chambers, the atria, quiver rapidly and irregularly instead of beating in a coordinated manner. This disorganized movement causes blood within the atria to stagnate.
Blood pooling, especially in the left atrial appendage (LAA)—a small pouch attached to the left atrium—creates an ideal environment for blood clots (thrombi) to form. The LAA is a common site for clot development because blood flow is naturally slow, and AFib eliminates the proper “atrial kick.” The risk of a clot is significantly higher if the AFib has lasted more than 48 hours or if the duration is unknown.
The danger arises when cardioversion restores a normal, forceful heartbeat. The newly contracting atria can forcefully squeeze and dislodge any pre-existing clot from the LAA. This dislodged clot travels through the bloodstream to the brain, causing an ischemic stroke.
What a Transesophageal Echocardiogram Is
A Transesophageal Echocardiogram (TEE) is an imaging test specifically designed to look for dangerous blood clots within the heart chambers. It is a specialized ultrasound that uses a transducer to create detailed images of the heart’s structure. Unlike a standard echocardiogram, the TEE is performed “transesophageally,” meaning the probe is passed down the patient’s esophagus.
The patient receives a sedative and a local anesthetic spray to numb the throat. The flexible probe is carefully guided through the mouth and down the throat into the esophagus. Because the esophagus runs directly behind the heart, this positioning provides a clear, close-up view of the heart’s posterior structures.
This superior viewing capability is why the TEE is required before cardioversion. It allows clear visualization of the left atrial appendage (LAA), which is often difficult to see with a standard ultrasound. By inspecting the LAA, physicians look for clots or “sludge,” which indicates a high risk of clot formation.
Finding Clots and Determining the Next Steps
The results of the Transesophageal Echocardiogram directly determine the patient’s immediate treatment plan. The TEE functions as a gatekeeper, allowing physicians to proceed with cardioversion only if the heart is deemed safe. The most favorable outcome is a negative TEE, meaning no blood clots are visualized in the left atrium or the LAA.
Negative TEE Result
If the TEE is clear, electrical cardioversion can typically proceed immediately during the same visit. Even with a negative TEE, the patient must start or continue anticoagulation therapy for at least four weeks after the procedure. This is necessary because the atria can suffer from “stunning” after the shock. This temporary impairment of contraction can create a new environment for clot formation in the days following cardioversion.
Positive TEE Result
If a clot is identified in the LAA, cardioversion must be postponed to prevent an immediate stroke. The patient is placed on therapeutic anticoagulation (blood-thinning medication) for a specified period, typically three to four weeks. This treatment allows the medication time to stabilize and potentially dissolve the pre-existing clot. The medical team will only consider attempting cardioversion after this period, often requiring another TEE to confirm the clot has resolved.