Evaluation of coagulation and fibrinolysis in horses with atrial fibrillation.

This study investigated whether horses with atrial fibrillation, a heart condition, have an increased tendency for blood clotting (hypercoagulability). The research found that while these horses did not show overt signs of hypercoagulation, a higher proportion of them showed signs of subtle blood clotting activity compared to healthy horses.

Research Methodology

The researchers conducted a case-control study, a type of observational study where two existing groups differing in outcome are identified and compared based on some supposed causal attribute.

• They took plasma samples from 42 horses, with 25 of these horses having atrial fibrillation and the remaining 17 serving as the control group with no cardiovascular or systemic diseases.
• Using these samples, they performed a range of hematologic tests, including evaluating plasma fibrinogen and D-dimer concentrations, prothrombin and activated partial thromboplastin times, and antithrombin activity. These tests helped to assess the state of coagulation and fibrinolysis (blood clot breakdown) in the horses.
• The researchers also gathered historical and clinical variables known to be associated with a hypercoagulable state in other species.

Findings

The test results indicated that horses with atrial fibrillation didn’t show overt signs of hypercoagulation, a state characterized by excessive blood clotting, or thromboembolism, which involves blockage of a blood vessel by a clot.

• However, these horses did have significantly lower antithrombin activity. Antithrombin is a protein that helps prevent blood clots from forming, so a lower activity suggests an increased risk of clotting.
• No significant differences were witnessed in plasma fibrinogen and D-dimer concentrations, as well as prothrombin and activated partial thromboplastin times, between the atrial fibrillation and control groups. This suggests that overall coagulation parameters were relatively similar between the two groups.
• Despite these similarities, there was a significantly larger proportion of horses with atrial fibrillation that had abnormal plasma D-dimer concentration and test results indicative of subclinical activated coagulation or abnormal coagulation test results. This implies that while not overtly hypercoagulated, the atrial fibrillation group tended to have more subtle activation of the coagulation system.

Conclusion

While horses with atrial fibrillation did not show obvious signs of a hypercoagulable state, a higher proportion of them demonstrated subclinical activated coagulation compared to the control horses. This discovery is crucial, as it could guide future treatment approaches for horses with atrilinear fibrillation to manage the potential risk of blood clotting.