Abstract 743: Acute Onset Human Atrial Fibrillation is Associated with Platelet Activation: Insights Into the Hypercoagulable State
Introduction: While several risk factors predispose to the hypercoagulable state in atrial fibrillation (AF), it remains unclear whether human AF alone is prothrombotic. We sought to determine whether the onset of AF itself, independent of other risk factors, leads to the development of a prothrombotic state. We compared systemic and local cardiac platelet activation before and after the onset of acute AF.
Methods: Patients (n=14, 13 males, age 55 ± 13 yrs) with paroxysmal AF underwent radiofrequency circumferential AF ablation with pulmonary vein isolation. All patients presented in sinus rhythm. Baseline blood samples were obtained during sinus rhythm simultaneously from sheaths placed in the femoral vein (systemic venous sample) and the coronary sinus (local cardiac sample). AF was induced by burst atrial pacing. Following 15 mins of AF, systemic and local blood samples were collected again. Using two-color whole blood flow cytometry, all samples were immediately analyzed for platelet P-selectin expression (CD62) as a marker of platelet activation.
Results: During sinus rhythm, platelet activation (expressed as % P-selectin (+) platelets) was 2.2 ± 1.1% in the coronary sinus (local cardiac) samples and 2.7 ± 2.3% in the systemic venous samples (p=NS). After 15 mins of AF, local platelet activation increased to 2.8 ± 1.8% (p<0.01 vs. pre-AF) while systemic platelet activation did not change (2.9 ± 3.1%, p=NS).
Conclusions: This study demonstrates that human atrial fibrillation can cause platelet activation within minutes of onset. This acute effect was observed in local cardiac blood return from the coronary sinus and not in the systemic circulation. The results indicate that AF alone, independent of other risk factors, may contribute to the hypercoagulable state. The degree to which AF increases other prothrombotic factors needs to be determined.