Przezskórne zamknięcie uszka lewego przedsionka u pacjentów z migotaniem przedsionków
Transcatheter left atrial appendage occlusion in patients with atrial fibrillation
Atrial fibrillation is one the most common significant heart arrhythmias. It affects 1-2% of the total population, and the frequency of its incidence increases with age (1-4). A triple increase in the incidence of this disorder is projected by 2050 (5). There occurs particularly high risk of peripheral embolism and, in particular, ischemic stroke in patients with atrial fibrillation. The risk of stroke in patients with atrial fibrillation of non valvular origin is about 5% per year (6). In the research by Framigham, it has been shown, however, that the mortality rate of patients due to a stroke resulting from the atrial fibrillation is significantly higher in comparison to the strokes not connected with arrhythmia (7). This fact indicates the necessity of effective treatment and prevention in case of the occurrence of stroke in these patients. There are two main types of preventing the impact on the brain associated with occurrence of atrial fibrillation. The first is the use of chronic anticoagulant therapy, and the second is closing the left atrium appendage as a source of embolic material. The closure may be performed with surgical, thoracoscopic or percutaneous method. Randomized clinical studies show that the use of oral anticoagulant therapy is an effective method to reduce the risk of embolism and ischemic stroke. Sometimes, however, it is not fully exploited in patients with atrial fibrillation because of the risk of bleeding, contraindications or the lack of cooperation on the part of the patient (8-13). One of the most modern and dynamically developed methods used in the prevention of stroke in patients with atrial fibrillation is transcatheter atrial appendage occlusion. This method, however, is recommended only for patients unable to use chronic anticoagulant therapy.
The left atrial appendage is the remnant of the embryological left atrium. It is a tubular structure with various patches and very variable morphology. Its complicated structure is conducive to the blood retention. It is especially evident during atrial fibrillation. The appendage consists of a very soft and thin “paper wall” and its ostium of very variable size from 5-40 mm is located between the mitral ring and the left upper lung vein. Its morphology can be very diverse and may resemble a shape of: a cactus, hen comb, sleeve or a cauliflower (14, 15). Echocardiographic studies have shown that in patients with atrial fibrillation of non-valvular origin, in 90% of cases the thrombus locates in the left atrium appendage. It results from the decrease in the speed of the blood flow, its stagnation, enlargement of the cavity and the increased activity of the platelets adhesion molecules (16-18).
The concept of closing the left atrium appendage in patients with atrial fibrillation of non-valvular origin is based on the assumption that only 10% of the thrombi does not arise in the left atrium appendage. In conclusion, its exclusion as a potential source of embolic materials should greatly reduce the risk of ischemic stroke and pulmonary embolism. This is confirmed by the observations of patients with atrial fibrillation and congenital absence of the left atrial appendage, where the risk of embolic episodes is relatively small, though it has not been exactly estimated (19-27). Incidental occlusion treatments or resection of the left atrium appendage during the cardio surgery operations have been carried out for many years. In the literature the first of such cases was described by Madden already in 1949 (28). The effectiveness of the surgical resection of left atrium appendage methods in the prevention of stroke was described in patients undergoing coronary artery bypass surgery in a randomized study of LAAOS (LAA Occlusion Study) (29). However, this method is only additional, on the occasion of other cardio surgeries rather than as a standalone procedure. In recent times, occlusion systems have been developed using the electrocardiographic guided thoracoscopic technique (30), and special epicardial stitches led by the magnet (31). At different stages of the research there are other minimally invasive surgical and transcutaneous systems such as Aegis, AtriClip, Cardioablate.
The first transcatheter device for left atrial appendage occlusion was the PLAATO (Percutaneous Left Atrial Appendage Transcatheter Occlusion device). It was designed as a nitinol valve mask frame covered with a polytetrafluoroethylene membrane. The system was introduced to the left atrial appendage by venous system and interventricular septum through appropriately profiled interatrial vascular sheath of diameter of 12F. Settling in the appendage was enabled due to the hooks located on the wires of occluder and passing out through the membrane.
The first implantation of the PLAATO system in a man took place on 30 August 2001 and was conducted by Sievert and Lesh (32). The efficiency of the system has been confirmed in small clinical trials, however, due to the difficult technique of implantation and observed side effects of the system it has been withdrawn from the market in 2006. The second system which was used for the transcutaneous left atrium appendage occlusion was AMPLATZER, designed for atrial septal defect occlusion with two opposite disks. The first treatment with the use of this system was conducted on June 16, 2002 by Bernhard Meier. The treatment was carried out with a local anesthesia (33). In the following years, AMPLATZER was redesigned to match left atrium appendage. In 2008 a dedicated to the left atrial appendage occlusion Cardiac Amplatzer was introduced (ACP, St. Jude, USA) together with a specially developed bringing catheter. The system received CE mark in December 2008. The ACP system is built with nitinol meshwork covered with polyester material. It consists of three parts: central panel, carpal tunnel and disc. The disc has the task of ostium left atrium appendage occlusion. With the usage of the lobe, the position of the occluder stabilizes on the surface of small hooks. The system is available in sizes from 16 to 30 mm. In 2012, a new version of the occluder ACP called AMULET was introduced. The old platform remained the same but the lobe and isthmus was redesigned increasing the amount of catches so as to improve the fixation of the system and its effectiveness to reduce the risk of formation of thrombi. The AMULET system was, however, withdrawn from the market to successive improvements.
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