Altered clot microstructure detected in obstructive sleep apnoea hypopnoea syndrome

Abnormal clot microstructure plays a pivotal role in the pathophysiology of thromboembolic diseases. Assessing the viscoelastic properties of clot microstructure using novel parameters, Time to Gel Point (T(GP)), Fractal Dimension (d(f)) and clot elasticity (G׳(GP)) could explain the increased cardiovascular and thromboembolic events in patients with Obstructive Sleep Apnoea Hypopnea Syndrome (OSAHS). We wanted to compare T(GP), d(f), and G׳(GP) and their diurnal variation in OSAHS and symptomatic comparators. thirty six patients attending a sleep disturbed breathing clinic with symptoms of OSAHS were recruited. T(GP), d(f) and G׳(GP) were measured alongside standard coagulation screening, thrombin generation assays, and platelet aggregometry at 16:00 h and immediately after an in-patient sleep study at 07:30 h. OSAHS group had significantly lower afternoon d(f) than comparators (1.705±0.033 vs. 1.731±0.031, p<0.05). d(f) showed diurnal variation and only in the OSAHS group, being significantly lower in the afternoon than morning (p<0.05). Diurnal changes in d(f) correlated with 4% DR, even after controlling for BMI (r=0.37, p=0.02). The lower d(f) in the afternoon in OSAHS suggests a partial compensatory change that may make up for other pro-clotting abnormalities/hypertension during the night. The change to the thrombotic tendency in the afternoon is biggest in severe OSAHS. d(f) Shows promise as a new microstructural indicator for abnormal haemostasis in OSAHS.