Left Atrial Appendage Occlusion (LAAO)
The Structural Heart Intervention Registries are within the National Cardiac Audit Programme (NCAP). There are four structural heart intervention registries including Left Atrial Appendage Occlusion (LAAO).
The left atrial appendage (LAA) is a normal structure in the heart which plays a role in blood volume regulation, particularly in children. It is a sack-like structure and consists of thick muscle-fibres, allow it to stretch and contract as blood volume changes. In the presence of low flow and/or reduced contractility, this muscular pouch can allow blood to stagnate and clot. If this clot should then escape the appendage, it can then travel in the arterial blood system (termed “embolisation”) and wedge into a vessel supplying a vital organ or tissue, depriving it of oxygen. When this happens in one of the blood vessels to the brain it is termed an “embolic stroke”. When the clots travel anywhere else it is referred to as an “embolus”.
The commonest cause for this low flow/stagnation of blood in the LAA is an abnormal heart rhythm called atrial fibrillation (AF), (although other atrial arrhythmias such as flutter and atrial tachycardia are also implicated, but less common).
AF is characterised by an irregular and often rapid beating of the heart. It is the commonest arrhythmia in the UK and affects around 1.5% of the whole population. It increases dramatically with age however and it is estimated that around 6.5% over those over 65 have AF, rising to 28.5% of those over the age of 85.
Standard treatment is to reduce the blood ‘s clotting time using anticoagulant drugs (direct oral anticoagulants or DOACs) – such as apixaban, Edoxaban, rivaroxaban and dabigatran, or older drugs like warfarin). These drugs inevitably increase the risk of bleeding, although this is usually highly outweighed in favour of the reducing the risk of stroke/embolisation.
Nevertheless, a minority of patients find themselves in the double-bind of being at risk of embolic stroke, but also at high risk from bleeds – such as chronic bleeds in the gut, or sudden, potentially catastrophic bleeds in the brain or gut.
As such, these patients are deemed at too high risk to use oral anticoagulation despite having a significant risk of stroke and embolus.
In this scenario a non-drug solution has been demonstrated to reduce stroke risk – closing off the LAA. This may be done using a small tube or catheter, inserted into a vein at the top of the leg, with a plug-like device deployed into the LAA, or by clipping the appendage at the time of any cardiac surgery.
The NICOR Left atrial appendage occlusion (LAAO) audit look solely at this catheter-based method. The LAAO device may come from several manufacturers, allow the most common by far are the Watchman (Boston Scientific) and Amulet (Abbott Medical) devices. Once inserted into the LAA, a short period of time is required for the body to grow over the device with a smooth, “non-stick” coating of cells. As around 95% of all AF related emboli are thought to originate from the LAA, then these devices, if well placed, can reduce the risk of stroke without the need for anticoagulant drugs in the long term.
The aim of the audit is to collect clinical and outcome data on structural heart intervention services carried out in the UK. This is a significant development and will enable identification of key metrics for benchmarking, improving care of patients undergoing these procedures and for the safe introduction of new technologies in this country. The audit is managed by NICOR, with clinical direction and strategy provided by national professional societies.
Current evidence suggests that percutaneous occlusion of the left atrial appendage (LAA) is efficacious in reducing the risk of thromboembolic complications associated with non-valvular atrial fibrillation (AF). With regard to safety, there is a risk of life-threatening complications from the procedure, but the incidence of these is low. Therefore, this procedure may be used provided that normal arrangements are in place for clinical governance, consent and audit.
Commissioning guidance mandates that centres and operators should review and benchmark their procedures and outcomes.