| Left atrial appendage occlusion | |
|---|---|
 A left atrial appendage occlusion method similar to the WATCHMAN device. | |
| ICD-9-CM | 37.36 |
Left atrial appendage occlusion (LAAO), also referred to as left atrial appendage closure (LAAC), is a procedure used to reduce the risk of blood clots from the left atrial appendage entering the bloodstream and causing a stroke in those with non-valvular atrial fibrillation.
The left atrial appendage is a pouch-like structure located in the upper part of the left atrium. [1] Left atrial appendage occlusion (LAAO) is an alternative therapy to oral anticoagulation in a certain subset of patients with atrial fibrillation. Atrial fibrillation is characterized by an irregular and uncoordinated pumping function of the atria. This chaotic pattern of contraction can lead to reduced pumping efficiency and subsequent formation of blood clots, most notably in the left atrial appendage. [1] Over 90% of stroke-causing clots that originate in the heart in patients with non-valvular AF are formed in the left atrial appendage. [2] LAAO does not completely eliminate the risk of stroke in patients with AF but it does reduce the risk of stroke from emboli that originate in the left atrial appendage. [3] The left atrial appendage can be purposefully occluded (i.e. closed) to help prevent the formation of clots in one of two ways.
The most common treatment aimed at alleviating the burden of stroke in the setting of AF includes anticoagulation (blood-thinners), which are used to reduce the chance of blood clot formation. These medications, specifically direct oral anticoagulants (i.e. dabigatran, apixaban, rivaroxaban, edoxaban) and vitamin K antagonists (i.e. warfarin), are very effective in lowering the risk of stroke in AF patients. Most patients can tolerate anticoagulation for years (and even decades) without serious side effects. However, there are certain subsets of individuals who are unable to tolerate anticoagulation, and may be subject to increased bleeding or hematological risks. These patients may be good candidates for LAAO: [4]
Occlusion of the left atrial appendage can be achieved from outside the heart (the Lariat device) or from inside the heart (endovascular) with a blood-exposed implant (the Watchman and Amulet devices). The first method is a form of ligation that eliminates perfusion of the LAA. While effective in preventing many embolic strokes, it also negates the endocrine contribution (atrial natriuretic peptide) of the LAA. The second approach has many hazards as well but preserves the cardiac endocrine properties of the LAA. Further evaluation of both approaches is merited.
The LAA can also be surgically removed simultaneously with other cardiac procedures such as the maze procedure or during mitral valve surgery; specifically, it can be occluded or excluded by over-sewing, excision and resection, ligation, stapling with or without amputation of the LAA or application of a clip system [6] [7] [8] Finally, the left atrial appendage has been closed in a limited number of patients using a chest keyhole surgery approach. [9] [10]
LAA can also be occluded by the placement of clips such as the AtriClip or Penditure devices.
Watchman device
On March 13, 2015, the U.S. Food and Drug Administration approved the Watchman LAAC Implant, from Boston Scientific, to reduce the risk of thromboembolism from the left atrial appendage in patients with non-valvular AF who are at increased risk of stroke have an appropriate reason to seek a non-drug alternative to blood thinning medications. The Watchman implant was studied in two randomized clinical trials and several clinical registries. [11] The implant was approved in Europe in 2009. [12]
The Watchman is a one-time implant typically performed under general anesthesia with transesophageal echo guidance (TEE). Similar to a stent procedure, the device is guided into the heart through a flexible tube (catheter) inserted through the femoral vein in the upper leg. The implant is introduced into the right atrium and is then passed into the left atrium through a hole in the septum that divides the two atria of the heart. [13] This small hole in the septum usually disappear within six months. [14] [15] Once the position is confirmed, the implant is released and is left permanently fixed in the heart. The implant does not require open heart surgery and does not need to be replaced. Recovery typically takes twenty-four hours. [13]
The patient continues taking warfarin with aspirin for 45 days post implantation at which point in time they return for a transesophageal echocardiography to judge completeness of the closure and the presence of blood clots. If the LAA is completely occluded, then the patient can stop taking warfarin and start clopidogrel and aspirin for six months after implant. At six months post implantation, it is recommended for the patient to continue taking aspirin indefinitely. [13] In the PREVAIL clinical trial, 92% of patients stopped taking warfarin after 45 days and 99% discontinued warfarin at one year. [16]
Another device termed PLAATO (percutaneous left atrial appendage transcatheter occlusion) was the first LAA occlusion device, [17] [18] although it is no longer being developed by its manufacturer (Appriva Medical, Inc. from Sunnyvale, California). In 210 patients receiving the PLAATO device, there was an estimated 61% reduction in the calculated stroke risk. [19]
Amplatzer Amulet device
The Amplatzer device from St. Jude Medical, used to close atrial septal defects, has also been used to occlude the left atrial appendage. [20] [21] This can be performed without general anaesthesia and without echocardiographic guidance. Transcatheter patch obliteration of the LAA has also been reported. [14] The Amulet device is inserted very similarly to the Watchman LAAC implant. A catheter is introduced into the groin and travels up to the heart where it crosses from the right atrium into the left atrium via a hole in the septum. The device is then discharged into the LAA. Eventually tissue grows over the Amulet device and completely occludes the LAA. [22]
The ULTRASEAL LAA device, from Cardia, is a percutaneous, transcatheter device intended to prevent thrombus embolization from the left atrial appendage in patients who have non-valvular atrial fibrillation. As with all Cardia devices (such as: Atrial Septal Defect Closure Device or Patent Foramen Ovale Closure Device), the Ultraseal is fully retrievable and repositionable in the Cardia Delivery System used for deployment. The device can be retrieved and redeployed multiple times in a single procedure without replacing the device or delivery sheath.
Other devices exist to occlude the left atrial appendage from the inside of the heart such as the Wavecrest device [23] and the Lariat device. [24] The latter technique entails closing a strangling noose around the LAA, which is advanced from the chest wall with a special sheath, after introducing a balloon in the LAA from the inside surface of the heart (endocardium).
The main adverse events related to these procedures include pericardial effusion, incomplete LAA closure, dislodgement of the device, blood clot formation on the device requiring prolonged oral anticoagulation, and the general risks of catheter-based techniques (such as air embolism). [25] The left atrium anatomy can also preclude use of the device in some patients. [26]
Theoretical concerns surround the role of the LAA in thirst regulation and water retention because it is an important source of atrial natriuretic factor. [27] [28] Preserving the right atrial appendage might attenuate this effect. [29]
An anticoagulant, commonly known as a blood thinner, is a chemical substance that prevents or reduces coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where they help keep the bite area unclotted long enough for the animal to obtain some blood.
Atrial septal defect (ASD) is a congenital heart defect in which blood flows between the atria of the heart. Some flow is a normal condition both pre-birth and immediately post-birth via the foramen ovale; however, when this does not naturally close after birth it is referred to as a patent (open) foramen ovale (PFO). It is common in patients with a congenital atrial septal aneurysm (ASA).
Ximelagatran is an anticoagulant that has been investigated extensively as a replacement for warfarin that would overcome the problematic dietary, drug interaction, and monitoring issues associated with warfarin therapy. In 2006, its manufacturer AstraZeneca announced that it would withdraw pending applications for marketing approval after reports of hepatotoxicity during trials, and discontinue its distribution in countries where the drug had been approved.
The mini-maze procedures are cardiac surgery procedures intended to cure atrial fibrillation (AF), a common disturbance of heart rhythm. They are procedures derived from the original maze procedure developed by James Cox, MD.
Dabigatran, sold under the brand name Pradaxa among others, is an anticoagulant used to treat and prevent blood clots and to prevent stroke in people with atrial fibrillation. Specifically it is used to prevent blood clots following hip or knee replacement and in those with a history of prior clots. It is used as an alternative to warfarin and does not require monitoring by blood tests. In a meta analysis of 7 different studies, there was no benefit of dabigatran over warfarin in preventing ischemic stroke; however, dabigatran were associated with a lower hazard for intracranial bleeding compared with warfarin, but also had a higher risk of gastrointestinal bleeding relative to warfarin. It is taken by mouth.
Mitral valve replacement is a procedure whereby the diseased mitral valve of a patient's heart is replaced by either a mechanical or tissue (bioprosthetic) valve.
Lutembacher's syndrome is a very rare form of congenital heart disease that affects one of the chambers of the heart as well as a valve. It is commonly known as both congenital atrial septal defect (ASD) and acquired mitral stenosis (MS). Congenital atrial septal defect refers to a hole being in the septum or wall that separates the two atria; this condition is usually seen in fetuses and infants. Mitral stenosis refers to mitral valve leaflets sticking to each other making the opening for blood to pass from the atrium to the ventricles very small. With the valve being so small, blood has difficulty passing from the left atrium into the left ventricle. Septal defects that may occur with Lutembacher's syndrome include: Ostium primum atrial septal defect or ostium secundum which is more prevalent.
The CHADS2 score and its updated version, the CHA2DS2-VASc score, are clinical prediction rules for estimating the risk of stroke in people with non-rheumatic atrial fibrillation (AF), a common and serious heart arrhythmia associated with thromboembolic stroke. Such a score is used to determine whether or not treatment is required with anticoagulation therapy or antiplatelet therapy, since AF can cause stasis of blood in the upper heart chambers, leading to the formation of a mural thrombus that can dislodge into the blood flow, reach the brain, cut off supply to the brain, and cause a stroke.
Direct factor Xa inhibitors (xabans) are anticoagulants, used to both treat and prevent blood clots in veins, and prevent stroke and embolism in people with atrial fibrillation (AF).
Vitamin K antagonists (VKA) are a group of substances that reduce blood clotting by reducing the action of vitamin K. The term "vitamin K antagonist" is technically a misnomer, as the drugs do not directly antagonize the action of vitamin K in the pharmacological sense, but rather the recycling of vitamin K. Vitamin K antagonists (VKAs) have been the mainstay of anticoagulation therapy for more than 50 years.
Atrial fibrillation is an abnormal heart rhythm (arrhythmia) characterized by rapid and irregular beating of the atrial chambers of the heart. It often begins as short periods of abnormal beating, which become longer or continuous over time. It may also start as other forms of arrhythmia such as atrial flutter that then transform into AF.
The management of atrial fibrillation (AF) is focused on preventing temporary circulatory instability, stroke and other ischemic events. Control of heart rate and rhythm are principally used to achieve the former, while anticoagulation may be employed to decrease the risk of stroke. Within the context of stroke, the discipline may be referred to as stroke prevention in atrial fibrillation (SPAF). In emergencies, when circulatory collapse is imminent due to uncontrolled rapid heart rate, immediate cardioversion may be indicated.
Jonathan L. Halperin is an American cardiologist and the author of Bypass (ISBN 0-89586-509-2), among the most comprehensive works on the subject of coronary artery bypass surgery. In addition, he is the Robert and Harriet Heilbrunn Professor of Medicine at The Mount Sinai School of Medicine as well as Director of Clinical Cardiology in the Zena and Michael A. Wierner Cardiovascular Institute at The Mount Sinai Medical Center, both in New York City. Halperin was the principal cardiologist responsible for both the design and execution of the multi-center Stroke Prevention in Atrial Fibrillation (SPAF) clinical trials, funded by the National Institutes of Health, which helped develop antithrombotic strategies to prevent stroke, and he subsequently directed the SPORTIF clinical trials, which evaluated the first oral direct thrombin inhibitor for prevention of stroke in patients with atrial fibrillation.
Direct thrombin inhibitors (DTIs) are a class of anticoagulant drugs that can be used to prevent and treat embolisms and blood clots caused by various diseases. They inhibit thrombin, a serine protease which affects the coagulation cascade in many ways. DTIs have undergone rapid development since the 90's. With technological advances in genetic engineering the production of recombinant hirudin was made possible which opened the door to this new group of drugs. Before the use of DTIs the therapy and prophylaxis for anticoagulation had stayed the same for over 50 years with the use of heparin derivatives and warfarin which have some well known disadvantages. DTIs are still under development, but the research focus has shifted towards factor Xa inhibitors, or even dual thrombin and fXa inhibitors that have a broader mechanism of action by both inhibiting factor IIa (thrombin) and Xa. A recent review of patents and literature on thrombin inhibitors has demonstrated that the development of allosteric and multi-mechanism inhibitors might lead the way to a safer anticoagulant.
An implantable loop recorder (ILR), also known as an insertable cardiac monitor (ICM), is a small device that is implanted under the skin of the chest for cardiac monitoring, to record the heart's electrical activity for an extended period.
The SAMe-TT2R2 score is a clinical prediction rule to predict the quality of vitamin K antagonist anticoagulation therapy as measured by time in therapeutic INR range (TTR) (VKA e.g. warfarin). It has been suggested that it can aid in the medical decision making between VKAs and new oral anticoagulant/non-VKA oral anticoagulant (NOAC e.g. dabigatran, rivaroxaban, apixaban or edoxaban) in patients with atrial fibrillation (AF). This score can be used with patients with ≥1 additional stroke risk factors using the CHA2DS2-VASc score, where oral anticoagulation is recommended or should be considered.
HAS-BLED is a scoring system developed to assess 1-year risk of major bleeding in people taking anticoagulants for atrial fibrillation (AF). It was developed in 2010 with data from 3,978 people in the Euro Heart Survey. Major bleeding is defined as being intracranial bleedings, hospitalization, hemoglobin decrease > 2 g/dL, and/or transfusion.
Richard Whitlock FRCSC is a Canadian cardiovascular surgeon and intensivist, the Canada Research Chair in Cardiovascular Surgery and a professor of surgery at McMaster University Medical School. He is most well known for being the principal investigator of the SIRS trial and the LAAOS III trial. On April 9, 2015, Whitlock and his team performed the first transcatheter aortic valve implantation on a pregnant woman in the world.
Ulf Landmesser is a German specialist for cardiology and internal medicine. He is professor at the Institute for Health Research in Berlin and Head of the Medical Clinic of Cardiology at the Charité in Berlin. Landmesser is known for his work on coronary interventions and modern methods of catheter-based heart valve therapy.
Transcatheter pulmonary valve replacement (TPVR), also known as percutaneous pulmonary valve implantation (PPVI), is the replacement of the pulmonary valve via catheterization through a vein. It is a significantly less invasive procedure in comparison to open heart surgery and is commonly used to treat conditions such as pulmonary atresia.
