Atrial fibrillation (AF) is a heart condition that causes an irregular and often abnormally fast heartbeat.
Palpitations, dizziness and shortness of breath Department of Cardiothoracic Surgery are common symptoms of atrial fibrillation or irregular heart rhythms. Atrial fibrillation may occur even without any symptoms, and place patients at a high risk of stroke, especially if undiagnosed or untreated.
Atrial fibrillation (AF) is a heart condition that causes an irregular and often abnormally fast heartbeat. It is the most common heart rhythm disorder or arrhythmia. The risk of developing AF increases with age, lifestyle factors such as alcohol intake, as well as medical conditions such as diabetes mellitus.
AF causes the normal blood flow in the heart to be disrupted, leading to turbulent flow which leads to stasis in the upper chambers of the heart called the atria. This leads to the formation of blood clots which can be pumped along the circulatory system and end up in any part of the body including the brain, thus causing a stroke.
Studies have shown that AF carries an increased risk of the formation of blood clots in the blood stream and death. The main prevention of blood clot formation is to thin the blood with oral anticoagulants such as warfarin. However, anticoagulants can lead to complications from bleeding such as haemorrhagic stroke and bleeding in other areas such as the intestines. Several studies have been conducted to predict the risk of stroke and to determine if anticoagulation is necessary for individual patient using CHADS-VASc scores, a scoring system that calculates stroke risk for patients with AF1-2. Risk factors for stroke include age, history of stroke, hypertension, diabetes mellitus and heart failure. Patients with none of these risk factors and under the age of 65 carried an annual ischaemic stroke rate of less than 1%. However, in patients above the age of 75 with multiple risk factors, the annual stroke risk rose to 12% with an overall blood clot formation risk of 17%2.
Left Atrial Appendage Complications
Most often, further investigations through cardiac imaging show that the main origin of blood clots is from the stasis of blood in the left atrial appendage (LAA), a small blind outpouching in the wall of the atria. While the LAA plays a minor role in our body functions, compelling evidence has revealed that it has been increasingly implicated as the cause of stroke3. Hence there were studies done to evaluate the benefit of eradicating the LAA with exclusion or closure which can be performed through surgery or intervention procedure4-5.
Illustration of the heart with a close-up of percutaneous left atrial appendage closure.
AF is also more common amongst patients with valvular heart disease such as rheumatic heart disease (permanent damage to heart valves is caused by rheumatic fever), mitral valve or tricuspid valve dysfunction (valves between the upper and lower chambers of the heart on either the left or right side, not functioning properly) which can present as stenosis (valves do not open properly, causing impaired forward flow through the valve) or regurgitation (valves do not close properly, therefore allowing backward leakage of blood through the valve). Valvular heart disease can cause abnormal blood flow and enlargement of the atria leading to irregular conduction and eventually, persistent AF. Patients with AF who undergo cardiac surgery for valvular heart disease, may undergo ligation of the LAA at the same time, since it is accessible during surgery. As LAA is the main cause of abnormal blood clot formation, it has been theorised that occlusion would reduce the risk of stroke overall.
Recently, a large multicentre research trial was conducted (Left Atrial Appendage Occlusion Study LAAOS III) to evaluate the efficacy and safety of LAA occlusion in patients with AF undergoing cardiac surgery6. These patients had AF with risk of stroke (based on CHADS-VASc scores) and were randomly divided into two groups. One group would have LAA closure and the other group would not have LAA closure. Participants of the trial were followed up to assess for risk of ischaemic stroke, bleeding and heart attacks. This study proved the hypothesis that LAA closure in patients with AF reduced the risk of ischaemic stroke or blood clot formation in addition to anticoagulation of the blood.
The ligation of LAA procedure can be performed in various ways:
- Double layer suture closure from inside the atria
- Suture ligation/closure from external approach (with a purse string method)
- Amputation and closure of the LAA
- Application of a large titanium clip over the base of the appendage
- Stapler closure
As with any procedure, LAA procedure has its risks and benefits. The benefits of LAA include the lowering of overall risk of ischaemic stroke and blood clot formation by eliminating a potential and common area where blood clots originate. As the atrium wall is relatively thin, any manipulation or suturing may lead to intraoperative or post-operative bleeding, although this is not a common occurrence. If the ligation is not successful, there can occasionally still be flow into the atrial appendage and turbulent flow can still lead to blood clot formation.
1 Lip GY, Nieuwlaat R, Pisters R, Lane DA, Crijns HJ. Refining clinical risk stratification for predicting stroke and thromboembolism in atrial fibrillation using a novel risk factor-based approach: the Euro heart survey on atrial fibrillation.Chest. 2010; 137:263–272. doi: 10.1378/chest.09-1584
2 Yaghi S, Kamel H. Stratifying stroke risk in atrial fibrillation: beyond clinical risk scores. Stroke 2017;48:2665–2670
3 Yaghi S, Song C, Gray WA, Furie KL, Elkind MS, Kamel H. Left atrial appendage function and stroke risk. Stroke. 2015;46(12):3554–9
4 Reddy VY, Doshi SK, Sievert H, Buchbinder M, Neuzil P, Huber K, et al.; PROTECT AF Investigators. Percutaneous left atrial appendage closure for stroke prophylaxis in patients with atrial fibrillation: 2.3-year follow-up of the PROTECT AF (Watchman Left Atrial Appendage System for Embolic Protection in Patients with Atrial Fibrillation) Trial.Circulation. 2013; 127:720–729. doi: 10.1161/CIRCULATIONAHA.112.114389
5 Reddy VY, Sievert H, Halperin J, Doshi SK, Buchbinder M, Neuzil P, et al.; PROTECT AF Steering Committee and Investigators. Percutaneous left atrial appendage closure vs warfarin for atrial fibrillation: a randomized clinical trial.JAMA. 2014; 312:1988–1998. doi: 10.1001/jama.2014.15192
6 Whitlock RP, Belley-Cote EP, Paparella D, et al. Left atrial appendage occlusion during cardiac surgery to prevent stroke. N Engl J Med 2021;384:2081-2091
This article is from Murmurs Issue 39 (January – April 2021). Click here
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