Stroke Risk Assessment and Markers of Blood Clotting in Patients With Newly Diagnosed Non-valvular Atrial Fibrillation (NVAF), Who Have Not Received Oral Anticoagulation Therapy (OAC-therapy) Prior to Inclusion

Background:

Non-valvular atrial fibrillation (NVAF) is the most prevalent cardiac arrhythmia worldwide, and it is associated with a five-fold increased risk of ischemic stroke compared to a healthy population. Patients with stroke due to atrial fibrillation (AF) have a higher mortality and greater disability compared to stroke patients without AF.

Oral anticoagulants (OACs), either vitamin K antagonists (VKAs) or direct oral anticoagulants (DOACs), are the cornerstones for the prevention of ischemic strokes in patients with AF. Different stroke risk stratification schemes have been developed to guide OAC therapy decision-making in AF patients. The most commonly used scheme is the CHA2DS2-VASc score, including the clinical risk factors congestive heart failure, hypertension, age, diabetes, prior stroke, vascular disease, and female gender. One point is assigned for every risk factor encompassed by the CHA2DS2-VASc score, except age ≥75 years and prior stroke, which account for two points each. The score ranges from 0-9 points, with higher scores representing a higher risk of stroke. The annual risk of ischemic stroke for CHA2DS2-VASc score of 0, 1, and 2 is approximately 0-0.68 %, 1.3-1.61 %, and 2.2-2.49 %, respectively. Novel stroke risk stratification schemes, also incorporating biomarkers, have been developed, e.g., the ABC-stroke score (Age, Biomarkers, and Clinical history). The components of the ABC-stroke score include age, plasma levels of N-terminal pro-B-type Natriuretic Peptide (NT-proBNP) and high-sensitivity troponin T (hs-TNT), and prior stroke/transient ischemic attack (TIA). ABC-stroke risk categories are defined as low-risk (\<1 % predicted one-year risk of stroke), medium-risk (1-2 % predicted one-year risk of stroke), and high-risk (\>2 % predicted one-year risk of stroke). Studies have shown that the ABC-stroke score outperforms the CHA2DS2-VASc score in terms of stroke risk prediction and stratification of AF patients. However, the CHA2DS2-VASc score is still recommended as the primary stroke risk stratification scheme for AF patients in current guidelines. Despite the broad use of stroke risk stratification schemes in clinical practice, stroke risk assessment remains particularly challenging in AF patients with intermediate stroke risk, i.e., men with a CHA2DS2-VASc score of 1 and women with a CHA2DS2-VASc score of 2, where current guidelines recommend considering OAC therapy. OAC therapy is generally recommended for AF patients at high risk of stroke, i.e., men with CHA2DS2-VASc score of ≥ 2 and women with CHA2DS2-VASc score of ≥ 3. OAC therapy is generally not recommended for AF patients at low risk of stroke, i.e., men with a CHA2DS2-VASc score of 0 and women with a CHA2DS2-VASc score of 1.

The CHA2DS2-VASc score is broadly used in clinical practice due to its simplicity and low cost, however, the score has limitations. It exclusively includes clinical stroke-related risk factors, but not AF burden and left atrial size/function, which are proven independent markers of a hypercoagulable state. Treatment and stroke risk assessment in AF patients is moving towards a more individualized patient care, in which biomarkers play an essential role in improving risk stratification and personalizing treatment, as proposed in the ABC-stroke score. In recent years, measurements of hemostatic biomarkers in AF patients have been investigated in several studies, illustrating a hypercoagulable state. Of note, the CHA2DS2-VASc score also predicts stroke risk in patients without AF. Hence, there are concerns about the specificity for predicting AF-related stroke versus non-AF related stroke. Furthermore, the CHA2DS2-VASc score does not consider whether the modifiable components are well-controlled or not, which could lead to OAC overtreatment. For these reasons, there is still a need for refining stroke risk prediction using more AF-sensitive factors (i.e., AF-burden and left atrial size/function), in addition to the clinical factors, and for more exhaustive assessment of the modifiable components, to optimize stroke risk stratification in the future. It remains to be established whether the abovementioned AF-sensitive factors can be used to improve OAC decision-making, particularly in NVAF patients with intermediate stroke risk, where the balance between benefit and harm is less clear. When doubt persists, the presence of one or more non-CHA2DS2-VASc stroke risk factors could possibly strengthen the decision to initiate OAC therapy.

The annual risk of ischemic stroke in NVAF patients depends on the overall CHA2DS2-VASc score. However, the annual risk of ischemic stroke in patients with NVAF may differ depending on the individual components of the CHA2DS2-VASc score that determine the score, despite the overall score being the same, as well as whether the modifiable components are well-controlled or not. Glowicki et al. conducted a study comparing the hemostatic profiles of AF patients with low stroke risk to those with intermediate stroke risk, as determined by the CHA2DS2-VASc score. As opposed to the study by Glowicki et al., this study will compare all three stroke risk groups, i.e., low, intermediate, and high risk, as determined by the CHA2DS2-VASc score and ABC-stroke score, and will incorporate a broader panel of hemostatic biomarkers, including the contact activation system. Furthermore, this study will investigate AF-burden and left atrial size/function, and their association with the hemostatic profile. Patients included in this study will be genuinely OAC-naïve, as opposed to the study by Glowicki et al. Comparison of hemostatic profiles between different stroke risk groups could be essential for the future improvement of OAC therapy decision-making, especially in NVAF patients with intermediate stroke risk.

Objectives:

* To evaluate how the individual components of the CHA2DS2-VASc score and ABC-stroke score are associated with hemostatic biomarkers, including an assessment of whether the modifiable components are well-controlled or not, and how the hemostatic profile differs among stroke risk groups in OAC-naïve NVAF patients. * To compare the hemostatic profiles of the different CHA2DS2-VASc scores and ABC-stroke scores in OAC-naïve NVAF patients. * To evaluate how AF-burden is associated with hemostatic biomarkers in OAC-naïve NVAF patients. * To evaluate how left atrial size/function is associated with hemostatic biomarkers in OAC-naïve NVAF patients. * To evaluate how underlying heart failure with preserved ejection fraction (HFpEF) is associated with hemostatic biomarkers in OAC-naïve NVAF patients.

Materials and methods:

Study Design: The study consists of five substudies. The first substudy will investigate the association of the different CHA2DS2-VASc score and ABC-stroke score components with the hemostatic profile in OAC-naïve NVAF patients. Furthermore, assessment of whether the modifiable components of the CHA2DS2-VASc score (i.e., diabetes and hypertension) are well-controlled or not, and its impact on the hemostatic profile will be investigated. Likewise, the hemostatic profile of OAC-naïve NVAF patients with intermediate stroke risk will be compared to that of OAC-naïve NVAF patients with low and high stroke risks, respectively, to determine which of the two groups most closely resembles patients with intermediate stroke risk in terms of their hemostatic profile. The second substudy will compare the hemostatic profile between the CHA2DS2-VASc score and ABC-stroke score in OAC-naïve NVAF patients. The third substudy will investigate how AF-burden is associated with hemostatic biomarkers in OAC-naïve NVAF patients. AF-burden will be determined as a percentage based on the total number of AF-events during seven days heart rhythm monitoring. In the fourth substudy, investigators will evaluate how left atrial size/function is associated with hemostatic biomarkers in OAC-naïve NVAF patients. In the fifth substudy, investigators will investigate how underlying HFpEF is associated with hemostatic biomarkers in OAC-naïve NVAF patients. HFpEF will be evaluated using the HFA-PEFF and H2FPEF scores. The study is a cross-sectional, single-center observational study and will take place at Esbjerg Hospital - University Hospital of Southern Denmark, involving collaboration between the Unit for Thrombosis Research, Department of Clinical Diagnostics and the Department of Cardiology.

Study population: The study population will consist of patients with newly diagnosed NVAF. Patients will have to be naïve to oral and parenteral anticoagulants prior to inclusion. Investigators will check for this upon inclusion by systematic screening of an online medication database, called FMK, which is widely used among health care personnel in Denmark. According to the annual report (2023) from the AF database in Denmark (AFDK), there are about 800 patients with newly diagnosed AF in the catchment area of the University Hospital of Southern Denmark, Esbjerg, why investigators are confident that it will be possible to include the necessary number of patients. Collaboration with the general practitioners will be essential for patient inclusion. Investigators will provide comprehensive information to general practitioners about this study and the importance of withholding OAC treatment before subacute referral to the Department of Cardiology. Patients with newly diagnosed NVAF who are willing to participate in this study and sign the patient consent form will be scheduled for fast track outpatient clinic visit within four days of their consultation with the general practitioner for blood sampling, transthoracic echocardiography (TTE), and heart rhythm monitoring. OAC treatment will be initiated immediately after blood sampling, based on current guidelines for the management of AF, and investigators will also do a tailored comprehensive work-up of the AF patients as necessary. Demographic data will be collected, as well. Likewise, symptoms attributable to AF will be quantified according to the modified EHRA-score (European Heart Rhythm Association). To exclude other causes of coagulopathy and characterize the patients at baseline, investigators will measure the following variables in each participant: Full blood count, Activated Partial Thromboplastin Time (APTT), International Normalized Ratio (INR), renal function, Glycated Hemoglobin (HbA1c), C-reactive Protein (CRP), liver function, and lipid profiles. Furthermore, plasma levels of NT-proBNP and hs-TNT will be determined with high-sensitivity immunoassays to estimate the ABC-stroke score. The risk of thromboembolic events will be estimated using the CHA2DS2-VASc score and ABC-stroke score for all patients in this study population, and the patients will be grouped according to their overall individual score. Moreover, each group will be subdivided according to the individual components of the CHA2DS2-VASc score and ABC-stroke score that constitute the overall score. Investigators will determine whether hypertension and diabetes are effectively managed by conducting home blood pressure (BP) measurements and assessing HbA1c levels. BP will be measured at home three times in the morning and evening over three consecutive days, and mean BP will be calculated based on the measurements from days two and three. For simplicity, well-controlled hypertension will be defined as a BP ≤ 135/85 mmHg, and a systolic BP ≤ 145 mmHg for age groups \< 80 years and ≥ 80 years, respectively. The treatment goals for type 1 and 2 diabetes patients are HbA1c ≤ 53 and ≤ 48 mmol/mol, respectively, and will be used as thresholds for whether diabetes is well controlled or not.

Sample size estimation and statistical analyses: For sample size calculation, investigators utilized the median values and interquartile ranges of endogenous thrombin potential (ETP), as previously compared between AF patients with low and intermediate stroke risk

• Levels of von Willebrand factor (vWF) antigen [Срок оценки: von Willebrand factor antigen will be assessed at baseline (enrollment).]
• Concentration of cleaved high-molecular weight kininogen (cHK) [Срок оценки: cHK will be assessed at baseline (enrollment).]
• Concentration of coagulation factor XII (FXII) [Срок оценки: FXII will be assessed at baseline (enrollment).]
• Concentration of prekallikrein [Срок оценки: Prekallikrein will be assessed at baseline (enrollment).]
• Concentration of high-molecular weight kininogen (HK) [Срок оценки: HK will be assessed at basline (enrollment).]
• Concentration of C1-inhibitor [Срок оценки: C1-inhibitor will be assessed at baseline (enrollment).]
• Concentration of coagulation factor VII (FVII) [Срок оценки: FVII will be assessed at baseline (enrollment).]
• Concentration of coagulation factor X (FX) [Срок оценки: FX will be assessed at baseline (enrollment).]
• Concentration of coagulation factor II (FII) [Срок оценки: FII will be assessed at baseline (enrollment).]
• Concentration of protein C [Срок оценки: Protein C will be assessed at baseline (enrollment).]
• Concentration of protein S [Срок оценки: Protein S will be assessed at baseline (enrollment).]
• Concentration of antithrombin (AT). [Срок оценки: Antithrombin will be assessed at baseline (enrollment).]