Clinical Research Directory

Cardiac Assessment for Recurrent Stroke Risk Evaluation in Atrial Fibrillation

Background Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting up to 10% of the elderly. Ischemic stroke is the main complication of AF and cardioembolism is one of the leading causes of ischemic stroke, accounting for approximately one third of cases. Oral anticoagulant therapy (OAC) is a cornerstone in stroke prevention in patients with AF. According to randomized controlled trials of direct oral anticoagulants, a residual risk of ischemic stroke of 1-2% per year for so-called "breakthrough stroke" remains, despite adequate intake of OAC. The majority (\>70%) of these breakthrough strokes are cardioembolic in nature and only a minority are related to medication issues (e.g. non-compliance) or other, non-AF related etiologies. Stroke recurrence risk after such a breakthrough stroke markedly increases to 8-9% per year indicating a particularly high-risk situation. Why OAC fails in certain patients, but not in others remains as poorly understood, as does the reason why the subsequent risk of stroke is so high. Current risk stratification tools, such as the widely used CHA2DS2-VA(Sc)-score, fail to predict stroke risk in such a high-risk cohort, as they were intended to guide the initiation of OAC in low to moderate risk patients. In light of new therapeutic strategies currently being investigated, such as percutaneous left atrial appendage occlusion in patients with breakthrough strokes (ELAPSE - NCT05976685) or in AF-patients deemed high-risk (LAAOS IV - NCT05963698), improved risk stratification and characterization of high-risk AF patients is highly warranted. Several clinical factors, such as those reflected in the CHA2DS2-VA(Sc)-score, and especially a high AF-burden are associated with increased risk of cardioembolic stroke. Several cardiac serum biomarkers are thought to be surrogates not only of cardiac function, but also of cardioembolic risk. Reflecting ventricular and atrial wall tension, myocardial injury, oxidative stress and thrombogenicity, elevated NT-proBNP, MR-proANP, high-sensitive Troponin T and D-Dimers have all been associated with cardioembolic stroke in different AF and non-AF populations. As the main location of thrombus formation, the left atrium (LA) and more specifically its appendage (LAA) are of particular interest in the pathogenesis of cardioembolism. Pronounced LA-enlargement, compared to a normal-sized LA, correlates with an increased risk of cardioembolism in AF-patients. As over 80% of thrombi form within the LAA, several LAA-characteristics, such as slower LAA-flow velocity and larger LAA-orifice area have also been demonstrated to be associated with higher stroke risk. Although there is data on each one of these factors, they have only been investigated in low to moderate risk populations, such as AF-patients without prior stroke, OAC-naïve patients, or even within the general population as a whole. Their role in high-risk AF-patients and in breakthrough stroke is unknown. Hypothesis The investigators hypothesize that specific clinical factors, serum cardiac biomarkers and markers of LA- and LAA-morphology and function are associated with breakthrough stroke / OAC-failure and may improve risk stratification. Methods CARE-AF is a single-center, prospective cohort study conducted at the Stroke Center of the Inselspital, University Hospital Bern, Switzerland. Patients with an index ischemic stroke and AF (breakthrough and non-breakthrough cases) will be enrolled. The investigators will collect clinical data, serum cardiac biomarkers and echocardiographic indices of the LA and LAA. All patients will receive standardized annual follow-ups until the end of the study, defined as 12 months after the inclusion of the last participant. The primary endpoint is ischemic stroke or systemic embolism during follow-up. First, in a cross-sectional design, the study will assess the association between serum cardiac biomarkers and echocardiographic indices among patients with breakthrough vs. non-breakthrough stroke as index event, applying multivariate regression models. Second, the investigators will perform a longitudinal analysis assessing the association between the variables mentioned above and breakthrough stroke as index event with the primary endpoint, using multivariate Cox regression models. The study aims to enroll a minimum of 500 patients, which provides sufficient power to detect a clinically meaningful adjusted hazard ratio for recurrent stroke of 1.5 with 80% power at an alpha level of 5%. Conclusion The results of this project will enhance understanding of the role of specific clinical factors, cardiac serum biomarkers and echocardiographic indices in the residual risk of stroke in patients with AF on anticoagulation therapy. They may improve current risk stratification and have the potential to help guide therapeutic decisions in high-risk situations considering evolving therapeutic possibilities.

Chronic Remote Ischemic Conditioning in Small Infarctions Associated with Stent-assisted Coiling of Unruptured Intracranial Aneurysms

1. Disease Description Stent-assisted coiling has become an effective treatment modality for intracranial aneurysms. With continuous advancements in periprocedural antiplatelet regimens, the incidence of symptomatic thromboembolic events has significantly decreased. However, the rate of procedure-related microembolic infarctions, which are characterized by punctate hyperintense signals on DWI, remains high (10%-76.5%). The underlying causes of these microembolic infarctions remain controversial and may be associated with factors such as different stent types, sheath types, antiplatelet regimens, intraoperative adverse events (e.g., vascular dissection or spasm), patient age, and procedure duration. While most patients with microembolic infarctions exhibit no overt clinical symptoms, the presence of these infarctions reflects underlying tissue damage, posing potential risks that cannot be ignored. Furthermore, their occurrence highlights insufficient preoperative preparation or intraoperative technical issues, which may increase the likelihood of symptomatic embolism. Therefore, investigating the causes of microembolic infarctions and exploring preventive strategies is of great clinical significance. 2. Intervention Description Remote ischemic conditioning (RIC) involves inducing temporary ischemia in distal vessels to protect target vessels from ischemic and reperfusion injuries. RIC can be performed before, during, or after ischemic events and is widely used in the context of coronary artery ischemia. Some studies have shown that RIC can mitigate ischemia-related injuries in the myocardium, kidneys, and lower limbs following cardiovascular surgeries. Previous research has also demonstrated the neuroprotective effects of RIC in ischemia-reperfusion injuries of the nervous system. For instance, RIC significantly improves outcomes in cerebral small vessel disease (CSVD)-related acute stroke events and ameliorates cognitive impairments associated with CSVD. Moreover, the safety and efficacy of RIC have been validated in other conditions or procedures, such as aneurysmal subarachnoid hemorrhage (aSAH), intracranial atherosclerotic stenosis, and carotid artery stenting. 3. Research Hypothesis Current clinical studies on RIC have primarily focused on acute ischemic stroke (including large artery atherosclerosis and CSVD), spontaneous intracerebral hemorrhage, and subarachnoid hemorrhage. The Remote Ischemic Conditioning for Acute Stroke Trial (RESIST) indicated that RIC effectively improves outcomes in acute strokes related to CSVD, including reducing white matter hyperintensities, infarct volume, and modified Rankin Scale (mRS) scores. A clinical study conducted at the Mayo Clinic demonstrated the safety of remote ischemic preconditioning (RIPC) during intracranial aneurysm coiling. Our center's previous study on "Tirofiban and Procedure-Related Microemboli in Stent-Assisted Aneurysm Coiling" revealed that the incidence of procedure-related microembolic infarctions was 61.1% in the non-tirofiban group and 19.4% in the tirofiban-treated group. However, there is currently a lack of research on the use of RIC for procedure-related microembolic infarctions in stent-assisted aneurysm coiling. This study aims to explore the efficacy of ischemic conditioning treatment, performed preoperatively and postoperatively, in reducing procedure-related microembolic infarctions during standard stent-assisted aneurysm coiling. The primary outcomes include the incidence of acute microembolic infarctions postoperatively and the incidence of symptomatic microembolic infarctions at one month following RIC.