The purpose of this observational study is to investigate whether blood tests related to blood clotting are associated with established clinical stroke risk scores, the total amount of device-detected atrial fibrillation recorded by an implanted cardiac device, and ultrasound measurements of the heart in people with device-detected atrial fibrillation. The study will also evaluate whether these baseline measurements are associated with future clinical outcomes and may improve future stroke risk assessment. Device-detected atrial fibrillation is an irregular heart rhythm detected by implanted cardiac devices such as pacemakers, implantable cardiac monitors, and implantable defibrillators. It is often brief and does not cause symptoms. Although it increases the risk of stroke and systemic embolism, the risk is lower than in people with clinically diagnosed atrial fibrillation. As a result, it remains difficult to identify which patients are most likely to benefit from blood-thinning medication, which reduces the risk of stroke but also increases the risk of bleeding. The study will include 222 participants with implanted cardiac devices, including 111 participants with device-detected atrial fibrillation and 111 age-, sex-, and cardiac device indication-matched control participants without device-detected atrial fibrillation. At baseline, participants will undergo blood sampling, ultrasound examination of the heart, and routine device interrogation. Information on medical history and established clinical stroke risk factors will also be collected. The implanted cardiac device will be used to determine the total amount of device-detected atrial fibrillation recorded during the year before study inclusion. The baseline analyses will investigate whether established clinical stroke risk scores, the total amount of device-detected atrial fibrillation, and heart ultrasound findings are associated with changes in blood clotting that may indicate an increased tendency to form blood clots. The study will evaluate both primary and additional blood clotting markers to improve the understanding of the biological mechanisms underlying thromboembolic risk in device-detected atrial fibrillation. Participants will subsequently be followed for 10 years to determine whether baseline blood clotting markers, the total amount of device-detected atrial fibrillation, heart ultrasound findings, and clinical stroke risk scores are associated with future clinical outcomes, including stroke, systemic embolism, hospitalization, death, progression to clinically diagnosed atrial fibrillation, and initiation of oral anticoagulant therapy. The findings may improve the understanding of thromboembolic risk in people with device-detected atrial fibrillation and support the development of more individualized approaches to future stroke risk assessment and treatment.
Scientific Rationale Device-detected atrial fibrillation (DDAF) is associated with an increased risk of stroke and systemic embolism, although the risk is lower than in patients with clinically diagnosed atrial fibrillation. Consequently, it remains challenging to identify which patients are most likely to benefit from oral anticoagulant therapy while minimizing the risk of bleeding. Current stroke risk assessment in patients with device-detected atrial fibrillation relies primarily on clinical risk scores and does not incorporate haemostatic biomarkers, the burden of device-detected atrial fibrillation, or echocardiographic markers of atrial remodeling that may contribute to thromboembolic risk. This study aims to improve the understanding of thromboembolic risk in patients with DDAF and to evaluate whether integrating clinical stroke risk scores, DDAF burden, advanced echocardiographic variables, and haemostatic biomarkers may improve future stroke risk assessment. Study Design This is a prospective, single-center observational cohort study conducted at the Department of Cardiology, Esbjerg and Grindsted Hospital, University Hospital of Southern Denmark, in collaboration with the Unit for Thrombosis Research, Department of Clinical Diagnostics. The study consists of a single prospective observational cohort with three prespecified baseline analyses followed by a prospective 10-year longitudinal follow-up. A total of 222 participants will be enrolled, including 111 participants with device-detected atrial fibrillation and 111 control participants matched for age, sex, and indication for cardiac device implantation. Baseline Assessments At baseline, all participants will undergo standardized blood sampling, comprehensive transthoracic echocardiography, and collection of demographic and clinical information. Device interrogation will be performed to quantify the burden of device-detected atrial fibrillation. Clinical thromboembolic risk will be assessed using the CHA₂DS₂-VASc score. In addition, the ABC-stroke score will be calculated to evaluate its associations with haemostatic biomarkers and subsequent clinical outcomes in participants with device-detected atrial fibrillation. Independent variables in the prespecified baseline analyses include the CHA₂DS₂-VASc score, the ABC-stroke score, burden of device-detected atrial fibrillation, and advanced echocardiographic variables. The baseline analyses are designed to address three prespecified objectives. Together, these analyses are intended to determine whether established clinical stroke risk scores, burden of device-detected atrial fibrillation, and cardiac structural and functional abnormalities are associated with a more prothrombotic haemostatic profile. 1. To investigate whether the primary haemostatic biomarkers, endogenous thrombin potential (ETP) and von Willebrand factor antigen, differ between participants with device-detected atrial fibrillation and matched controls and whether they are associated with the CHA₂DS₂-VASc and ABC-stroke risk scores. Secondary analyses will evaluate associations between additional haemostatic biomarkers and the clinical stroke risk scores. 2. To investigate whether the primary haemostatic biomarkers are associated with the burden of device-detected atrial fibrillation. Secondary analyses will evaluate associations between DDAF burden and additional haemostatic biomarkers. 3. To investigate whether the primary haemostatic biomarkers are associated with advanced echocardiographic variables, including left atrial size and function. Secondary analyses will evaluate associations between echocardiographic variables and additional haemostatic biomarkers. The primary cross-sectional outcome measures are endogenous thrombin potential (ETP) and von Willebrand factor antigen. Secondary cross-sectional outcome measures comprise additional biomarkers of coagulation and fibrinolysis. Longitudinal Follow-up Participants will subsequently be followed for 10 years through electronic health records, routine device interrogation reports, and Danish national health registries. Follow-up data will be collected every second year to evaluate whether baseline primary and secondary haemostatic biomarkers, DDAF burden, clinical stroke risk scores, and echocardiographic findings are associated with subsequent stroke, systemic embolism, hospitalization, death, progression to clinically diagnosed atrial fibrillation, and initiation of oral anticoagulant therapy. Statistical Analysis The sample size was calculated to provide 80% statistical power at a two-sided significance level of 5% to detect the expected differences in endogenous thrombin potential and von Willebrand factor antigen between predefined CHA₂DS₂-VASc stroke risk groups, based on previously published effect sizes. Continuous variables will be assessed for normality using histograms and Q-Q plots. Variables with skewed distributions will be logarithmically transformed where appropriate. Homogeneity of variances will be assessed before parametric analyses. Continuous variables will be summarized as mean ± standard deviation or median with interquartile range according to data distribution, whereas categorical variables will be summarized as frequencies and percentages. Baseline comparisons between participants with device-detected atrial fibrillation and matched controls will be performed using appropriate parametric or non-parametric statistical methods according to data distribution. Multivariable regression models will be adjusted for predefined confounding variables as appropriate. The prespecified baseline analyses will primarily be performed using multivariable linear regression models with endogenous thrombin potential and von Willebrand factor antigen as the primary dependent variables. Secondary analyses will evaluate associations with additional haemostatic biomarkers. Regression models will be adjusted for prespecified confounding variables. Continuous predictors will be assessed for approximate linearity, and the assumptions underlying the linear regression models will be evaluated before interpretation of the results. Sensitivity analyses will be performed to evaluate the robustness of the primary findings. Adjustment for multiple testing will be performed using the Holm-Bonferroni procedure. Longitudinal analyses will evaluate whether baseline haemostatic biomarkers, burden of device-detected atrial fibrillation, clinical stroke risk scores, and echocardiographic findings are associated with subsequent clinical outcomes. Time-to-event analyses will be performed using Cox proportional hazards regression models when appropriate. Hazard ratios with 95% confidence intervals will be reported. Statistical significance will be defined as a two-sided p-value \<0.05.
Study Type
OBSERVATIONAL
Enrollment
222
Department of Cardiology, Esbjerg and Grindsted Hospital, Southwest Denmark
Esbjerg, Denmark
RECRUITINGThrombin generation assessed by endogenous thrombin potential
Thrombin generation plays a pivotal role in blood clotting and thus serve as primary outcome measure. Thrombin generation will be assessed through measurement of endogenous thrombin potential (nmol/L x min), using the calibrated automated thrombography (CAT) method.
Time frame: Baseline
Levels of von Willebrand factor (vWF) antigen
von Willebrand factor plays an important role in platelet plug formation. von Willebrand factor antigen (%) will be measured using an in-house immunoassay.
Time frame: Baseline
Plasma P-selectin Concentration
Plasma concentration of soluble P-selectin antigen (ng/ml) measured using an enzyme-linked immunosorbent assay (ELISA). P-selectin will only be measured in participants with elevated von Willebrand factor antigen concentrations.
Time frame: Baseline
Thrombin generation assessed by lag time
Thrombin generation plays a pivotal role in blood clotting. Thrombin generation will be assessed through measurement of lag time (min), using the calibrated automated thrombography (CAT) method.
Time frame: Baseline.
Thrombin generation assessed by peak thrombin concentration
Thrombin generation plays a pivotal role in blood clotting. Thrombin generation will be assessed through measurement of peak thrombin concentration (nmol/L), using the calibrated automated thrombography (CAT) method.
Time frame: Baseline
Thrombin generation assessed by time to peak
Thrombin generation plays a pivotal role in blood clotting. Thrombin generation will be assessed through measurement of time to peak (min), using the calibrated automated thrombography (CAT) method.
Time frame: Baseline
Kallikrein generation assessed by lag time
Kallikrein generation plays an important role in the contact activation system of the secondary hemostasis. Kallikrein generation will be assessed through measurement of lag time (min), using the calibrated automated thrombography (CAT) method.
Time frame: Baseline
High-sensitivity Cardiac Troponin T (hs-cTnT) Concentration
Plasma concentration of high-sensitivity cardiac troponin T (hs-cTnT) in ng/L measured at baseline
Time frame: Baseline
Kallikrein generation assessed by peak kallikrein concentration
Kallikrein generation plays an important role in the contact activation system of the secondary hemostasis. Kallikrein generation will be assessed through measurement of peak kallikrein concentration (nmol/L), using the calibrated automated thrombography (CAT) method.
Time frame: Baseline
Kallikrein generation assessed by time to peak
Kallikrein generation plays an important role in the contact activation system of the secondary hemostasis. Kallikrein generation will be assessed through measurement of time to peak (min), using the calibrated automated thrombography (CAT) method.
Time frame: Baseline
Kallikrein generation assessed by endogenous kallikrein potential
Kallikrein generation plays an important role in the contact activation system of the secondary hemostasis. Kallikrein generation will be assessed through measurement of endogenous kallikrein potential (nmol/L\*min), using the calibrated automated thrombography (CAT) method.
Time frame: Baseline
Concentrations of prothrombin fragment 1 + 2
Activation of the inactive prothrombin to the active thrombin will be estimated from concentrations of prothrombin fragment 1 + 2 (pmol/L), using a commercial enzyme-linked immunosorbent assay (ELISA).
Time frame: Baseline
Concentration of cleaved high-molecular weight kininogen (cHK)
cHK is an essential component of the contact activation system of the coagulation cascade. cHK (µg/ml) will be measured with the help of enzyme-linked immunosorbent assay (ELISA).
Time frame: Baseline
Concentration of coagulation factor XII (FXII)
FXII is an essential component of the contact activation system of the coagulation cascade. FXII (µg/ml) will be measured with the help of enzyme-linked immunosorbent assay (ELISA).
Time frame: Baseline
Concentration of prekallikrein
Prekallikrein is an essential component of the contact activation system of the coagulation cascade. Prekallikrein (µg/ml) will be measured with the help of enzyme-linked immunosorbent assay (ELISA).
Time frame: Baseline
Concentration of high-molecular weight kininogen (HK)
HK plays a key role in the contact activation system of the coagulation cascade. HK (%) will be measured using enzyme-linked immunosorbent assay (ELISA).
Time frame: Baseline
Concentration of C1-inhibitor
C1-inhibitor is the main regulator of the contact activation system. Concentration of C1-inhibitor (g/L) will be measured using nephelometry.
Time frame: Baseline
Concentration of coagulation factor VII (FVII)
FVII plays an important role in the secondary hemostasis. Concentration of FVII (%) will be measured using clot assay.
Time frame: Baseline
Concentration of coagulation factor X (FX)
FX plays an important role in the secondary hemostasis. Concentration of FX (%) will be measured using clot assay.
Time frame: Baseline
Concentration of coagulation factor II (FII)
FII plays an important role in the secondary hemostasis. Concentration of FII (%) will be measured using clot assay.
Time frame: Baseline
Concentration of protein C
Protein C is essential for the regulation of the blood coagulation cascade. Concentration of protein C (%) will be measured using chromogenic assay.
Time frame: Baseline
Concentration of protein S
Protein S is essential for the regulation of the blood coagulation cascade. Concentration of protein S (%) will be measured using turbidity.
Time frame: Baseline
Concentration of antithrombin (AT)
Antithrombin is essential for the regulation of the blood coagulation cascade. Concentration of antithrombin (%) will be measured using chromogenic assay.
Time frame: Baseline
Concentration of tissue factor pathway inhibitor (TFPI)
TFPI is important in the regulation of the blood coagulation system. TFPI (pg/ml) will be measured using enzyme-linked immunosorbent assay (ELISA).
Time frame: Baseline
Fibrin turnover assessed by maximum lysis velocity (Vmax)
Fibrin turnover will be assessed through fibrin clot lysis, where measurement of Vmax (optical density (OD)/min) will be conducted.
Time frame: Baseline
Fibrin turnover assessed by peak optical density (OD)
Fibrin turnover will be assessed through fibrin clot lysis, where measurement of peak OD (OD) will be conducted.
Time frame: Baseline
Fibrin turnover assessed by clot lysis
Fibrin turnover will be assessed through fibrin clot lysis, where measurement of clot lysis (%) will be conducted.
Time frame: Baseline
Fibrin turnover assessed by overall hemostatic potential (OHP)
Fibrin turnover will be assessed through fibrin clot lysis, where measurement of OHP (OD x min) will be conducted.
Time frame: Baseline
Fibrin turnover assessed by fiber diameter
Fibrin turnover will be assessed through fibrin clot lysis, where measurement of fiber diameter (µm) will be conducted.
Time frame: Baseline
Fibrin turnover assessed by fiber density
Fibrin turnover will be assessed through fibrin clot lysis, where measurement of fiber density (x 10\^6 Da/cm\^3) will be conducted.
Time frame: Baseline
Concentration of fibrinogen
Conversion of fibrinogen to fibrin, in which thrombin plays a key role, is essential for blood coagulation. Concentrations of fibrinogen (µmol/L) will be measured using nephelometry.
Time frame: Baseline
Concentration of D-dimer
D-dimer is a fibrin degradation product that reflects the fibrinolysis process (the breakdown of fibrin network), which plays a crucial role in preventing blood clots from causing complications. D-dimer (mg/L) will be measured using immunoassay.
Time frame: Baseline
Concentration of tissue-type plasminogen activator (t-PA)
t-PA is a protein that stimulates the breakdown of blood clots. It helps convert plasminogen into its active form, plasmin, the major enzyme responsible for the breakdown of blood clots. Concentration of t-PA (ng/ml) will be measured using enzyme-linked immunosorbent assay (ELISA).
Time frame: Baseline
Concentration of plasminogen activator inhibitor 1 (PAI-1)
PAI-1 functions as the inhibitor of t-PA, which will stimulate the formation of blood clots. Concentration of PAI-1 (ng/ml) will be measured using enzyme-linked immunosorbent assay (ELISA).
Time frame: Baseline
Levels of plasminogen
Plasminogen is the inactive form of plasmin, the major enzyme that breaks down blood clots. Levels of plasminogen (%) will be measured using chromogenic assay.
Time frame: Baseline
Levels of coagulation factor XIII (FXIII)
FXIII plays a key role in stabilizing the blood clots. Levels of FXIII will be measured using immunoassay.
Time frame: Baseline
Levels of plasmin inhibitor (PI)
PI is the major inhibitor of plasmin. Levels of PI (%) will be measured using chromogenic assay.
Time frame: Baseline
Levels of thrombin activatable fibrinolysis inhibitor (TAFI)
TAFI is an enzyme that is activated by thrombin, which downregulates fibrinolysis, stimulating blood clot formation. Levels TAFI will be measured using enzyme-linked immunosorbent assay (ELISA).
Time frame: Baseline
ADAMTS13 Antigen Concentration
Plasma concentration of ADAMTS13 antigen (ng/mL) measured using an enzyme-linked immunosorbent assay (ELISA). ADAMTS13 will only be measured in participants with elevated von Willebrand factor antigen concentrations.
Time frame: Baseline
N-terminal Pro-B-type Natriuretic Peptide (NT-proBNP) Concentration
Plasma concentration of N-terminal pro-B-type natriuretic peptide (NT-proBNP) in ng/L measured at baseline.
Time frame: Baseline
Stroke
Clinical stroke verified with imaging e.g. CT or MR.
Time frame: Up to 10 years.
Transient Ischemic Attack
Transient Ischemic Attack verified with imaging e.g. CT or MR
Time frame: Up to 10 years
Systemic embolism
Systemic embolism verified with imaging e.g. CT, MR or ultrasound
Time frame: Up to 10 years
Hospitalizations
All cause hospitalizations
Time frame: Up to 10 years
Heart failure hospitalizations
New onset or worsening of heart failure leading to hospitalization or urgent visit heart failure clinic
Time frame: Up to 10 years
All-cause mortality
All-cause mortality
Time frame: Up to 10 years
Cardiovascular death
Cardiovascular death
Time frame: Up to 10 years
Progression to clinically diagnosed atrial fibrillation or atrial flutter
Atrial fibrillation or flutter verified by a 12-lead ECG or ambulatory ECG monitoring
Time frame: Up to 10 years
Progression to >24 hours device-detected atrial fibrillation
Progression to \>24 hours device-detected atrial fibrillation at a scheduled out-of hospital or acute cardiac device interrogation
Time frame: Up to 10 years.
Initiation of oral anticoagulant therapy
Initiation of oral anticoagulant therapy with minimum 3 months treatment duration.
Time frame: Up to 10 years
Pulmonary embolism
Pulmonary embolism verified with imaging e.g. CT or V/Q scan
Time frame: Up to 10 years
Deep venous thrombosis
Deep venous thrombosis verified with radiology e.g. ultrasound or CT
Time frame: Up to 10 years
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