Standalone Thoracoscopic Left Atrial Appendage Closure Versus Medical Therapy in Atrial Fibrillation (STELLA-AF)

Atrial fibrillation (AF) is the most common sustained arrhythmia worldwide and is associated with a markedly increased risk of ischemic stroke, heart failure, cognitive decline, systemic embolism, hospitalization, and mortality. AF-related strokes are often severe, disabling, and recurrent. Based on extrapolation of published regional Swedish data, 350-400 000 individuals in Sweden have atrial fibrillation, of whom 81% are treated with OAC:s. Despite major advances in anticoagulation, AF continues to represent one of the most important cardiovascular contributors to long-term disability and healthcare expenditure.

For decades, oral anticoagulation with vitamin K antagonists represented the cornerstone of stroke prevention. The introduction of direct anticoagulant (DOAC) treatment fundamentally altered the therapeutic landscape. Trials including RE-LY, ROCKET-AF and ARISTOTLE demonstrated that DOAC therapy provides excellent protection against stroke/systemic embolism while reducing intracranial hemorrhage compared with warfarin. Consequently, DOACs became the standard of care for most patients with nonvalvular AF and are supported as first line treatment for most patients with nonvalvular AF.

However, anticoagulation is not without its downsides. Despite modern OACs, treatment poses a significant bleeding risk and a lifelong treatment burden. Clinical decision making is complicated by patient frailty, renal dysfunction, liver disease and by patients with previous history of intracranial or gastrointestinal bleeding. Furthermore, long-term adherence is imperfect in real-world practice. In above mentioned trials, the annual bleeding risk ranged from 2.1-3.6% in patients treated with OAC, corresponding to 8400-14400 Swedish patients having major bleeding events from AF-related OAC treatment each year.

Long-term anticoagulation may be associated with treatment burden, fear of bleeding, reduced treatment satisfaction, and impaired quality of life in some patients. Thus, the concept of a nonpharmacological strategy to prevent stroke remains highly attractive.

Left atrial appendage closure While initial trials showed promising results of catheter based endocardial LAAC in the Warfarin era, the CLOSURE-AF trial recently showed that that endocardial devices, including the WATCHMAN™ and the Amplatzer™ Amulet™, do not achieve results making them a feasible replacement for modern OAC therapy in AF patients with elevated bleeding risk. The limitations of endocardial LAAC have several explanations. Implantation of a foreign body within the left atrium creates a potential substrate for thrombus formation. Device-related thrombi have been associated with increased risk of ischemic stroke and remain a recognized complication of endocardial LAAC. Incomplete sealing may allow persistent blood flow into the appendage, potentially preserving thromboembolic risk. In addition, many patients require OAC or dual antiplatelet therapy during the endothelialisation period. Procedure related risks include vascular complications, procedure-related stroke, device embolization and pericardial tamponade .

The mechanistic rationale for left atrial appendage (LAA) exclusion originates from transoesophageal echocardiographic and autopsy studies demonstrating that the majority of intracardiac thrombi in nonvalvular AF arise from the LAA. The LAA is anatomically predisposed to thrombus formation because of reduced contractility, blood stasis, complex trabeculations, and impaired endothelial function during AF. This has led to the belief that mechanical elimination of the LAA may be a feasible alternative to systemic anticoagulation.

Therefore, epicardial LAAC may be a feasible option to endocardial devices in AF patients with increased bleeding risk. The LAAOS III trial demonstrated that surgical LAAC was associated with a 33% risk reduction of stroke in patients undergoing cardiac surgery, and current guidelines recommend LAAC in patients with AF undergoing cardiac procedures.

Thoracoscopic epicardial LAAC using devices including the AtriClip™ and Penditure™ may overcome several limitations of endocardial approaches. Firstly, no intracardiac foreign body is implanted, which reduces the risk of device-related thrombi. TLAAC requires no septal puncture and provides more complete anatomical exclusion of the appendage, with lower risk of residual leak. Cartledge and colleagues reported a series of 175 patients who underwent standalone TLAAC and demonstrated a 99.4% procedural success rate (defined as residual stump <10mm) with low risk of procedural complications. One patient (0.6%) required conversion to sternotomy due to LAA bleeding. The cohort had a predicted annual stroke rate of 4.8% but no ischemic strokes were observed in study participants at a median follow up of 12.5 months, despite OACs being discontinued in 90.3% of patients at discharge.

Furthermore, evidence suggests that the AF triggers located in the LAA may contribute to maintenance of AF itself. As the epicardial devices also create an electrical isolation, epicardial exclusion may therefore provide both thromboembolic and electrophysiological benefits.