Abstract
Orthostatic hypotension has been linked with increased mortality and cardiovascular morbidity; however, the underlying mechanisms are still unknown. The aim of the study was to assess markers of coagulability in patients with and without orthostatic hypotension who suffered transient loss of consciousness. A total of 233 consecutive patients more than 15 years old, with unexplained transient loss of consciousness, underwent head-up tilt test (HUT, Italian protocol). Blood samples were collected during supine rest before and at 3 min of 70° HUT for determination of fibrinogen, von Willebrand factor antigen (vWF:Ag) and activity (vWF:GP1bA), factor VIII (FVIII:C), lupus anticoagulant, and functional activated protein C-resistance. Orthostatic hypotension was defined as persistent decrease in SBP and/or DBP of more than 20/10 mmHg or SBP lower than 90 mmHg during passive HUT. One hundred and seventy-eight patients (81 men, 45.5%) not treated with vitamin-K antagonists were analyzed. Those with orthostatic hypotension (n = 49) were older [61 ± 18 vs. 47 ± 21 years (mean ± SD), P < 0.001], had increased C-supine (1.2 ± 0.39 vs. 1.0 ± 0.35, P = 0.001), FVIII:C-standing (1.2 ± 0.36 vs. 1.0 ± 0.34, P = 0.001), vWF:Ag-supine (1.5 ± 0.66 vs. 1.1 ± 0.44, P < 0.001), vWF:Ag-standing (1.5 ± 0.67 vs. 1.1 ± 0.46, P < 0.001), vWF:GP1bA-supine (1.5 ± 0.73 vs. 1.1 ± 0.42, P < 0.001), vWF:GP1bA-standing (1.5 ± 0.75 vs. 1.1 ± 0.42 P < 0.001), fibrinogen-standing (2.9 ± 0.53 vs. 2.7 ± 0.61, P = 0.03) but not fibrinogen-supine (2.8 ± 0.54 vs. 2.7 ± 0.61, P = 0.078) compared with patients without orthostatic hypotension. However, after adjustment for age, sex, and comorbidity, only vWF:Ag and vWF:GP1bA levels remained significantly increased in orthostatic hypotension patients. Concentration of vWF is elevated in patients with orthostatic hypotension who suffered a syncopal event. This observation may be helpful in understanding the increased risk of cardiovascular events in orthostatic hypotension.
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