Marie Willemet's PhD Thesis
Blood Flow Modeling for Patient-Specific Bypass Surgery in Lower-Limb Arteries
By Marie Willemet (Public Defense: February 17th, 2012, 16h15, Auditorium BARB94)
Every day in Belgium, at least one or two people will undergo a bypass surgery in the lower-limb arteries. This medical procedure consists of replacing an occluded section of the leg arteries with an artificial vessel, in order to allow blood to flow downwards of this blockage. Even though this intervention is very common, failure of this treatment within five years reaches up to 60%. In order to improve our understanding of the causes of bypass failure, one approach is to study the local hemodynamics (i.e. the blood flow circulation) in these vessels, as this factor strongly influences the initiation and progression of arterial diseases.
This thesis addresses this objective by modeling the patient-specific arterial hemodynamics. As each patient is characterized by his own physiology (e.g. morphology, severity of the disease) and is treated by a bypass graft of fixed characteristics (e.g. material, length, location of the anastomoses), each clinical case needs to be considered individually.
In the first part of our work, blood pressure, velocity and flow rate in the network of arteries are modeled with a one-dimensional model of the arteries and lumped windkessel models of the secondary and distal vessels. The 18 parameters of this coupled model are then computed in order to reflect the pathological condition of the patient. Thanks to the set-up of an experimental protocol of data acquisition, we have been able to acquire in-vivo measurements of hemodynamics in 25 patients operated with bypass surgery. The comparison of these in-vivo signals with numerical simulations enabled us to improve and validate our patient-specific numerical model.
In the second part of this thesis, the dynamic of blood is considered as impulses of waves which are generated by the contractions of the heart, and which propagate throughout the arterial network. By using the wave intensity analysis method, we analyzed and characterized these waves in the pathological arteries of the leg, and emphasized the effects of the bypass.
| contact : Marie Willemet | 17/02/2012 |