Summary
Observations were made on mural thrombi in experimental venous pouch aneurysms in
sheep. Thrombi associated with mural tears and dissection consisted predominantly
of laminated fibrin masking the earlier platelet deposition and infiltrating the wall
to some extent. Thrombus growth was associated with platelet masses of Zahn and secondary
fibrin deposition. Intervening spaces contained a variable quantity of coagulated
plasma, fibrin mesh, leucocytes, disintegrating red cells and platelets rather than
red thrombus as often suggested. Periodic deposition of platelet masses with surface
rippling, the whorling patterns of laminated fibrin and mechanical disruption of red
cells indicated the importance of haemodynamics. Coarse macroscopic lamination of
mural thrombi was attributed in part to recurrent dissections between the wall and
the mural thrombus and of the thrombus itself. These accounted for growth of thrombus
with expansion of the wall and interference with organization of the thrombus. The
model has proved suitable for the study of thrombogenesis and thrombus behaviour in
aneurysms.
