The effects of apixaban on clot characteristics in atrial fibrillation: A novel pharmacodynamic biomarker

The impact of physical activity and intensity on clot mechanical microstructure and contraction in middle-aged/older habitual runners

BACKGROUND

Exercise in healthy individuals is associated with a hypercoagulable phase, leading to a temporary increase in clot mass and strength, which are controlled by an effective fibrinolytic system. Conversely, people with cardiovascular diseases often have a reduced fibrinolytic pathway, increased clot mass and abnormal clot contraction, resulting in poorer outcomes. We assessed clot microstructure, particularly the contractile forces of clot formation, in response to two exercise intensities in middle-aged/older runners.

METHODS

Twenty-eight habitual male and female runners aged over 40 years completed a 10 km moderate-intensity run; 14 of them performed a 3 km high-intensity run. Blood samples were collected at baseline, immediately postexercise and after 1 h of rest. Clot structural biomarkers df, gel time, and measurements of mature clot mechanical properties (gel time, G'Max and CFmax) were analysed alongside conventional plasma markers.

RESULTS

Both exercise intensities altered markers of coagulant activity (PT, APTT and FVIII) and fibrinolysis (D-dimer), indicating hypercoagulability. Compared with longer-duration lower-intensity exercise, df was greater after short-duration intensified exercise bouts. Following an hour of rest, df dropped to baseline levels. Additionally, CFmax decreased across timepoints at both exercise intensities. This effect was noted after one hour of rest compared with baseline, suggesting continuous fibrinolytic activity postexercise.

CONCLUSION

Exercise transiently induces an intensity-dependent hypercoagulable state, resulting in denser clot formation and a reduced clot contractile force due to fibrinolysis. These findings can help guide the safe commencement of rehabilitation exercise programs for cerebrovascular patients.

CHA2DS2-VASc score and prior oral anticoagulant use on endovascular treatment for acute ischemic stroke

OBJECTIVE

We evaluated the effect of CHA2DS2-VASc score and prior use of oral anticoagulants (OACs) on endovascular treatment (EVT) in patients with acute ischemic stroke and atrial fibrillation (AF).

METHODS

Patients with AF who received EVT in 353 centers in Japan (2018-2020) were included. The outcomes were symptomatic intracerebral hemorrhage (sICH), in-hospital mortality, functional independence, and successful and complete reperfusion. The effects of CHA2DS2-VASc score, its components, and prior use of OACs were assessed via a multiple logistic regression model.

RESULTS

Of the 6984 patients, 780 (11.2%) used warfarin and 1168 (16.7%) used direct oral anticoagulants (DOACs) before EVT. Based on the CHA2DS2-VASc score, 6046 (86.6%) presented a high risk (≥2 for males and ≥3 for females) while 938 (13.4%) had intermediate to low risks. Higher CHA2DS2-VASc scores were associated with increased sICH, in-hospital mortality, and decreased functional independence, regardless of prior OACs. For patients with a high-risk category, prior DOACs increased the odds of successful and complete reperfusion (adjusted odds ratio [95% confidence interval (CI)], 1.27 [1.00-1.61] and 1.30 [1.10-1.53]). For those with integrated intermediate to low risks, neither prior warfarin nor DOAC affected the outcomes. Regardless of total CHA2DS2-VASc scores, patients with congestive heart failure or left ventricular dysfunction, hypertension, age >75 years, or female benefited similarly from prior DOAC use.

INTERPRETATION

Prior DOAC use for patients with high- and selected intermediate-risk CHA2DS2-VASc scores increased prevalence of successful and complete reperfusion. These findings may provide supplemental evidence to introduce preventive DOAC for patients with AF.

The effects of apixaban on clot characteristics in atrial fibrillation: A novel pharmacodynamic biomarker

Atrial fibrillation (AF) is a major risk factor for stroke. We aim to characterize AF patients and the effects of apixaban therapy in terms of clot microstructure using gel point analysis, a novel biomarker. Seventy-eight patients were included in the study, 50 Stroke with AF (AF-S), and 28 AF without stroke (AF). Pre- and post-anticoagulation samples were collected: gel point (GP) analysis was performed to obtain (i) TGP (the time taken to reach the GP or the clot formation time) and (ii) d_{f ,} the fractal dimension of the clot, a quantification of clot fibrin microstructure at the GP. At baseline, the AF-S group had a d_f  = 1.70 (±0.05) and TGP = 306 (±73 s). The AF group had a df = 1.70 ± 0.05 and TGP = 346 ± 78 s, showing a significantly shortened TGP in the stroke group (p = .008). For both groups, apixaban significantly prolonged TGP, p = .005, but resulted in no change in df. Apixaban prolonged clotting time while having no significant impact on the blood's ability to form stable clots (no change in d_f ). This indicates that apixaban provides protection from the formation of thrombi by reducing clotting kinetics.