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Introduction
The primary disease target for our innovation is thromboembolic stroke from AF. This disease is addressed by removing the LAA from the systemic circulation using a novel percutaneous epicardial transcatheter based solution. In addition to avoiding the morbidity of open heart surgery, this solution does not necessitate entering a cardiac chamber. Thus, no device or hardware is exposed to the systemic circulation obviating the need for either procedural or even temporary post-procedural anticoagulation. Specific unique features of the innovation include a hollow suture, closure of the suture via a percutaneous approach, and the use of electrical signal-based navigation.
Atrial fibrillation (AF) is the most common arrhythmia encountered in clinical practice, and it poses a growing health hazard . It affects 2.2 million Americans and is expected to afflict up to 16 million by the year 2050 . Atrial fibrillation has been associated with an increased risk of thromboembolism . Due to its complex anatomy and diminished blood flow during AF, the left atrial appendage (LAA) has been a common site of left atrial thrombi, accounting for 98% of such thrombi in transesophageal echocardiography (TEE)-based studies .
Currently, oral anticoagulation is the best established prophylactic therapy for stroke prevention in AF . Unfortunately, due to numerous drug and dietary interactions, the narrow therapeutic window and need for frequent blood tests to ensure safe anticoagulation, as well as the inherent risk of major bleeding, warfarin is frequently underutilized in individuals at risk of thromboembolism . Dabigatran, apixaban, and rivaroxaban are new oral agents that have been shown to be non-inferior or superior to warfarin in large prospective randomized trials . However, these new agents still retain a risk of potential bleeding complications. Furthermore, the high cost of these agents adversely affects drug adherence. Even in the controlled environment of prospective randomized trials, over 20% of patients discontinue these agents within two years.
To address this vexing clinical problem, several nonpharmacologic approaches have been explored to exclude the LAA from the systemic circulation and thus avoid the need for systemic anticoagulation. Traditionally open surgical ligation was performed in select cases and more recently, less invasive transcatheter based solutions have been developed. A percutaneous strategy for LAA exclusion may include placement of an endocardial device such as the WATCHMAN device to exclude the appendage from the circulation or external ligation. The WATCHMAN device is non-inferior to warfarin in preventing embolic stroke in AF patients but is associated with serious complications including device embolization, infection, tamponade, and peri-procedural stroke . Furthermore, even though these patients are “intolerant” to systemic anticoagulation, they still require a period of systemic anticoagulation until device endothelialization has occurred. Recently, a strategy utilizing an epicardial suture as well as an endocardial guide placed using a transseptal approach has been introduced into practice . While early results are promising, limitations still include the need for transseptal puncture (since intracardiac access to the left atrium is required) as well as the need for procedural anticoagulation, both of which increase the risk of the procedure.
Thus, an entirely epicardial strategy would avoid any contact of the central circulation with a foreign body, thus limiting the potential for development of intra-procedural thrombus and thromboembolism. Such an approach would eliminate the need for procedural anticoagulation and transseptal puncture, possibly rendering the procedure safer and shortening the procedure duration .
The strength of the invention is its simplicity (see Video 1 and Fig. 1 ). The invention integrates two materials with disparate physical properties, a pliable and durable hollow suture with a semi-rigid pre-formed wire to permit easy encircling and ligation of the appendage. The hollow suture is composed of PTFE, which has a long-term safety record of durability, limited or absent inflammatory response, and a promotion of endothelialization with its use in cardiac surgery.
The Aegis Sentinel System (Vancouver, Canada) has three major components. There are a deflectable sheath, a deflectable grabber and the hollow suture stiffened with a preloaded 0.25 mm wire. The sheath is used to establish access and tool delivery as well as facilitate detection of the LAA. It is introduced into the pericardial space using a well described pericardial access technique . Fluoroscopy is used to ensure an anterior approach to facilitate LAA capture. The grabber is used to capture and control the LAA (see Video 2 ). It has an articulating atraumatic jaw with specially mounted electrodes between the jaws as well as on the grabber shaft. These electrodes are designed to facilitate navigation and identification of the LAA. The closely-spaced bipolar electrodes between the grabber’s jaws capture the electrical properties of the tissue distinguishing LAA (atrial electrogram, see Fig. 2 ) from epicardial fat and ventricular tissue. Additional recordings between each jaw and the shaft and bipolar recordings along the shaft permit identification of the grasper’s position relative to electrically active cardiac tissues. Once the system is positioned near the LAA, an injection of angiographic contrast in close proximity outlines the LAA to facilitate and confirm its capture.
