Effect of vascular geometry on haemodynamic changes in a carotid artery bifurcation using numerical simulation.

OBJECTIVES: The geometry of carotid bifurcation is a crucial contributing factor to the localization of atherosclerotic lesions. Currently, studies on carotid bifurcation geometry are limited to the region near to bifurcation. This study aimed to determine the influence of carotid bifurcation geometry on the blood flow using numerical simulations considering magnitude of haemodynamic parameters in the extended regions of carotid artery. METHODS: In the present study, haemodynamic analysis is carried out using the non-Newtonian viscosity model for patient-specific geometries consisting of both Left and Right carotid arteries. A 3D patient-specific geometric model is generated using MIMICS, and a numerical model is created using ANSYS. RESULTS: The results obtained from patient-specific cases are compared. The influence of geometric features such as lumen diameter, bifurcation angle, and tortuosity on the haemodynamics parameters such as velocity, WSS, pressure, Oscillatory Shear Index (OSI), and Time-Averaged Wall Shear Stress (TAWSS) are compared. CONCLUSION: The results demonstrate significant changes in the flow regime due to the geometric shape of the carotid artery. It is observed that the lower value of TAWSS occurs near the bifurcation region and carotid bulb region. In addition, the higher value of the (OSI) is observed in the Internal Carotid Artery (ICA) and the tortuous carotid artery region. However, it is also observed that apart from the bifurcation angle, other factors, such as tortuosity and area ratio, play a significant role in the flow dynamics of the carotid artery.

Branchial Cyst with Branchial Fistula: A Rare Association.

Branchial arch anomalies are the most common congenital neck masses. The second branchial arch anomalies followed by first arch anomalies are seen commonly in the descending order. They originate from remnants of branchial arches and clefts. They may present as cysts, sinus tracts, fistulae or cartilaginous remnants. They are mostly located in the lateral aspect of the neck anterior to the sternocleidomastoid, anterior to the hyoid bone, preauricular region or at the angle of the mandible. A complete fistula communicating with a branchial arch cyst is a very rare congenital anomaly of the branchial apparatus. These patients are generally asymptomatic but may present with mucoid discharge from the tract. Here we present a case of branchial fistula associated with a branchial cyst in a 11 year old child.

Effect of postural changes on normal and stenosed common carotid artery using FSI.

Gravity associated with postural changes has a strong bearing on haemodynamics of blood flow in arteries. Its effect on stenosed cases has not been widely investigated. In the present study, variation observed in blood flow during postural changes is investigated for different conditions like standing, sleeping and head-down position. A fluid structure interaction study is carried out for idealized normal and 75% eccentric and concentric stenosed common carotid normal artery. The results clearly indicate the effects of altered gravity on flow conditions. It was found to be very significant during head-down position and demonstrated very high arterial blood pressure in stenosed common carotid when compared with normal carotid.

Pediatric aneurysms and vein of Galen malformations.

Pediatric aneurysms are different from adult aneurysms - they are more rare, are giant and in the posterior circulation more frequently than in adults and may be associated with congenital disorders. Infectious and traumatic aneursyms are also seen more frequently. Vein of Galen malformations are even rarer entities. They may be of choroidal or mural type. Based on the degree of AV shunting they may present with failure to thrive, with hydrocephalus or in severe cases with heart failure. The only possible treatment is by endovascular techniques - both transarterial and transvenous routes are employed. Rarely transtorcular approach is needed. These cases should be managed by an experienced neurointerventionist.