[Anticoagulation of valvular prostheses]

Shear accumulation as a means for evaluating risk of thromboembolic events in novel endovascular stent graft designs

OBJECTIVE

This study proposes to establish a simulation-based technique for evaluating shear accumulation in stent grafts and to use the technique to assess the performance of a novel branched stent graft system.

METHODS

Computational fluid dynamics models, with transient boundary conditions, particle injection, and rigid walls, simplifying assumptions were developed and used to evaluate the shear accumulation in various stent graft configurations with a healthy aorta as comparison.

RESULTS

Shear streamlines are presented for the various configurations. Shear accumulation was also calculated for each configuration. The number of particles with shear accumulations >3.5 Pa-s for each configuration was compared with the shear accumulation values of commercially available mechanical aortic valves from the literature.

CONCLUSIONS

The stent graft configuration with the diaphragm does have particles with shear accumulation >3.5 Pa-s. However, the percentage of particles with shear accumulation above 3.5 Pa-s is less than the two commercially available mechanical aortic valves, and more surprisingly, is smaller than in the healthy aorta.

[Splenic rupture and anticoagulant therapy]

Splenic rupture associated with anticoagulant therapy is a rare entity. We report a case of spontaneous splenic rupture in a 62-year-old man who was treated by acenocoumarol orally after an aortic-valve replacement. Unrecognised, minor trauma may lead to splenic haemorrhage in patients receiving anticoagulant therapy. The symptoms and signs may mimic those of acute myocardial infarction and cardiogenic shock. Early diagnosis is essential. Reversal of the anticoagulant and emergent splenectomy are the treatments of choice.