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Posted on Monday October 14, 2024 in Naked Heart
An article by Dr Edward Leatham, Consultant Cardiologist and author of The Naked Heart, a series of simple blog and video explanations covering all of the main cardiovascular conditions that can affect us, as we age.
In many patient’s the heart can transition from atrial fibrillation, or flutter, back into its normal rhythm on its own. This is known as natural, or spontaneous, cardioversion. When the heart rhythm gets stuck in AFib, doctors can assist with restoring the heart’s normal rhythm by either using an electric direct current cardioversion (DC version) or by administering drugs, such as amiodarone or flecainide, which bring about ‘chemical cardioversion’. Regardless of how the heart rhythm is restored, the risk of clot formation and stroke remains the same.
There are two main reasons for this risk. The first is that during atrial fibrillation or flutter, a clot may develop in the left atrial appendage, an out-pouching of the left atrium where stagnant blood pools during AFib. The likelihood of a clot forming and detaching to pass into the circulation and cause a stroke is low, and the risk is linked to other risk factors. Doctors use a risk calculator tool called the CHA2DS2-VASc score to help with the decision on whether anticoagulants should be prescribed to prevent stroke.
An example of left atrial thrombus or clot in the heart is shown in the below video, taken from a TOE performed prior to a planned DC cardioversion, where the cardiologist wanted to check the left atrial appendage was clear from any clot before proceeding with a DC cardioversion.
A transoesophageal echocardiogram (TOE, or TEE in USA) is an ultrasound mounted on an endoscopic probe that the cardiologist passes down the patients gullet (after numbing it with a local anaesthetic spray). The patient can be fully awake, sedated or given a full anaesthetic first. It allows the cardiologist to check the left atrial appendage, part of the left atrium located at the back of the heart for clots. There is no other reliable way to check for clots, which can be important if cardioversion is being considered. TOE cardioversion is an extremely useful method (see Refs 1 and 2 below) for cardiologists to cardiovert AF in patients who have been in atrial fibrillation for more than 24 hours but not yet started anticoagulants. It’s safe to cardiovert providing i/ the TOE shows no thrombus in the left atrium and ii/ anticoagulants are given from the point of cardioversion for at least 3 weeks. The TOE images below show one such patient who DID have a large clot in his left atrial appendage. We did not proceed with the cardioversion which otherwise would have caused the clot to detach and pass into his circulation causing an embolic stroke. As a result of the TOE findings, cardioversion was delayed until he had received another 4 weeks of a more effective anticoagulant. A repeat TOE confirmed the clot had been dissolved so that cardioversion could be safely performed. A disaster was averted!
‘Atrial paresis’ is the paralysis of the atrium and the left atrial appendage that follows a period of atrial fibrillation. Even though P waves might appear on the ECG, indicating normal sinus rhythm, the left atrial muscles do not initially contract – termed ‘atrial paresis’. The duration of atrial paresis is related, amongst other things, to the length of time spent in atrial fibrillation. It can last several days in individuals who have been in atrial fibrillation for months. This is a critical time for clot formation, as the paretic atrium exhibits even less movement than atria in fibrillation.
This mechanism of clot formation is significant and not widely acknowledged. It occurs in patients who undergo chemical or natural cardioversion, possibly following an acute illness that leads to atrial fibrillation.
Physicians and general practitioners must be aware of this risk and understand that the CHA2DS2-VASc score alone cannot dictate the use of anticoagulants.
In any adult patient who has experienced atrial fibrillation for more than 24 hours, who is expected to return to normal rhythm, anticoagulation is essential, to prevent catastrophic stroke.
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When clots from the left atrial appendage dislodge, they can travel to various parts of the body, including the coronary artery, which receives about 5% of the blood from each heartbeat, or the cerebral arteries, accounting for approximately 20% of each cardiac cycle's output
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An article by Dr Edward Leatham, Consultant Cardiologist. As cardiologists, our primary focus is often on diagnosing, treating, and managing cardiovascular diseases, which is essential to healthcare. However, heart health involves more than just addressing immediate conditions—it also includes promoting […]