Abstract

Fibrin deposition and platelet thrombus dimensions on subendothelium were studied in four groups of patients with coagulation factor deficiencies. Five patients with factor VIII deficiency (APTT 120 +/- 8 sec) and three patients with factor IX deficiency (APTT 125 +/- 11 sec) were severe bleeders, whereas four patients with factor XII deficiency and seven with factor XI deficiency were either asymptomatic or only mild bleeders despite APTT values of 439 +/- 49 and 153 +/- 13 sec, respectively. Everted segments of deendothelialized rabbit aorta were exposed at a shear rate of 650 sec(-1) for 5 and 10 min to directly sampled venous blood in an annular chamber. Blood coagulation was evaluated by measuring fibrin deposition (percent surface coverage) on the subendothelium and post-chamber fibrinopeptide A levels; platelet thrombus dimensions on the subendothelium were evaluated by determining the total thrombus volume per surface area (using an optical scanning technique) and the average height of the three tallest thrombi. Consistent differences were observed among the patient groups for both the 5-min and 10-min exposure times. The larger of the 5- and 10-min exposure-time values was used to calculate group averages. Fibrin deposition in normal subjects was 81% +/- 5% surface coverage, and post- chamber fibrinopeptide A values were 712 +/- 64 ng/ml. Markedly decreased fibrin deposition and fibrinopeptide A levels were observed in factor VIII deficiency (2% +/- 1% and 102 +/- 19 ng/ml) and factor IX deficiency (11% +/- 7% and 69 +/- 11 ng/ml). In contrast, significantly higher values were obtained in patients deficient in factor XI (33% +/- 5% and 201 +/- 57 ng/ml) and factor XII (66% +/- 12% and 306 +/- 72 ng/ml). Differences in thrombus dimensions were also observed. In normal subjects, the value for thrombus volume and average height of the tallest thrombi were 8.3 +/- 1.3 cu micron/sq micron and 145 +/- 11 micron, respectively, and in patients were as follows: FVIII, 2.7 +/- 0.6 and 71 +/- 7; FIX, 4.5 +/- 1.8 and 88 +/- 14; FXI, 11.8 +/- 1.9 and 125 +/- 10; and FXII, 7.9 +/- 3.1 and 130 +/- 25. Platelet thrombus dimensions were normal in a patient with fibrinogen deficiency, indicating that the smaller thrombi in factor VIII and factor IX deficiencies were probably due to impaired evolution of thrombin rather than diminished fibrin formation.(ABSTRACT TRUNCATED AT 400 WORDS)

This content is only available as a PDF.