Apixaban versus Aspirin for Embolic Stroke of Undetermined Source

Embolic Stroke of Undetermined Source: New Data and New Controversies on Cardiac Monitoring and Anticoagulation

Embolic strokes of undetermined source (ESUS) represent 9%-25% of all ischemic strokes. Based on the suspicion that a large proportion of cardioembolic sources remain undetected among embolic stroke of undetermined source patients, it has been hypothesized that a universal approach of anticoagulation would be better than aspirin for preventing recurrent strokes. However, 4 randomized controlled trials (RCTs), with different degrees of patient selection, failed to confirm this hypothesis. In parallel, several RCTs consistently demonstrated that prolonged cardiac monitoring increased atrial fibrillation detection and anticoagulation initiation compared with usual care in patients with ESUS, and later in individuals with ischemic stroke of known cause (e.g., large or small vessel disease). However, none of these trials or subsequent meta-analyses of all available RCTs have shown a reduction in stroke recurrence associated with the use of prolonged cardiac monitoring. In this article, we review the clinical and research implications of recent RCTs of antithrombotic therapy in patients with ESUS and in high-risk populations with and without stroke, with device-detected asymptomatic atrial fibrillation.

Thromboembolic risk and oral anticoagulation in subclinical atrial fibrillation

Availability of devices capable of continuous rhythm monitoring such as smartwatches, implantable loop recorders, or pacemakers/defibrillators is continuously increasing. Importantly, device detected "subclinical" atrial fibrillation seems to convey a significantly lower risk of thromboembolism than "clinical" atrial fibrillation verified by a conventional ECG recording. While current guidelines indicate a possible role of oral anticoagulation in selected high-risk patients with subclinical AF, recent trials show an ambiguous risk/benefit relationship of anticoagulation in this setting. The present review therefore summarizes current data on the role of oral anticoagulation in subclinical AF, aims at aiding in the decision process of anticoagulation, and illustrates current gaps in evidence regarding subclinical AF.

3-D transesophageal echocardiography aids in assessment of embolic stroke due to aortic atherosclerotic plaque: A case series

Atherosclerosis is the most common cause of heart disease and stroke. Plaque thickness ≥4 mm in the ascending aorta or aortic arch is strongly correlated with cerebral embolic events and ischemic stroke. However, despite imaging workup, the cause of embolic stroke remains unidentified in many patients. Transesophageal echocardiography (TEE) is the preferred echocardiographic method for the evaluation of cardiac source of emboli. 2D TEE imaging evaluates aortic root and aortic arch in a single plane or two planes with biplane imaging. However, 2D TEE often fails to detect mobile or complex components in the ascending aorta and aortic arch plaques. The routine availability of 3D TEE in current ultrasound systems may significantly improve the assessment of aortic plaques as a potential embolic source. In this case series, we present four consecutive patients with stroke who underwent TEE by a single cardiologist for possible cardioembolic source. Some of these patients may have been labelled as "cryptogenic stroke" or "embolic stroke of undetermined source" (ESUS) due to the presence of insignificant or nonmobile ascending aortic or aortic arch plaques on 2D TEE imaging. In our four consecutive patients with ESUS who underwent TEE by a single operator, 3D TEE showed complex aortic arch plaques with ulceration with mobile components and established these plaques as the likely source of embolic stroke.

Power Considerations in Designing and Interpreting Adaptive Clinical Trials

Adaptive clinical trials allow researchers to make preplanned modifications based on accumulating data from an ongoing trial while preserving the trial's integrity and validity. These modifications may include early termination in cases of successes or lack of efficacy, refining the sample size, altering treatments or doses, or focusing recruitment efforts on individuals most likely to benefit. In this issue of NEJM Evidence, Geisler et al.1 report results from the Apixaban for Treatment of Embolic Stroke of Undetermined Source (ATTICUS) trial, a multicenter randomized trial of apixaban compared with aspirin in patients with cardioembolism risk factors.