Modeling of Coronary Arteries in Kawasaki Disease

Background

Problem and Need Description

Kawasaki disease (KD) is the world’s leading cause of heart disease in children [1]. Children with KD suffer from acute autoimmune attacks on the mucus membranes, lymph nodes, myocardium, and systemic and coronary arteries [2]. The pathological mechanisms that lead to KD remain unknown, but known pathophysiological triggers include inflammation and genetic makeup. 

 

 

One of the critical symptoms of KD is the formation of aneurysms in the coronary arteries [5]. The walls of coronary arteries in KD become inflamed, and attract an autoimmune, inflammatory response that damages the vessel wall. Inflammation creates an aneurysm, whose dilated geometry makes blood swirl and recirculate. Recirculation forms blood clots, which accumulate and block the vessel completely, leading to MI, ischemia, heart failure, and sudden death [5, 6].

Such complications must be treated by anticoagulants or surgical interventions, like angioplasty, stenting, or coronary artery bypass graft [7]. However, it is difficult to use medical imaging alone to assess whether a coronary aneurysm rupture would lead to complete thrombosis and heart failure. Angiography and intravascular ultrasound can determine useful properties of a blood vessel, such as arterial diameter and flow rate. However, these parameters are not directly linked to thrombogenesis [8]. Choosing certain surgical treatments, based on these indecisive parameters, can put a patient at unnecessary risk of pain, infection, stroke, cardiac arrest, and death.

Therefore, clinicians require a new method of diagnosis, to accurately determine the type of surgery to pursue and when to pursue it. Such a method would be based on risk of stenosis or heart failure, and will reduce exposure of a patient to the side risks associated with surgery. Recent research indicates more aneurysm-specific parameters besides morphology, which are specific to both KD and mechanical engineering. Examples include recirculation (fluid vorticity), [9], platelet aggregation, [10, 11] shear stress, and shear stress gradients [12] acting on the aneurysm endothelium. Because these parameters of fluid mechanics are less understood by clinicians, they have not been implemented in clinical practice. But an efficient strategy for diagnosing and treating KD must be based on the most recent findings about the pathology.

   

Current Technology and Improvements by Design

Current risk assessment focuses almost exclusively on children with KD. Coronary artery internal diameter and morphology is imaged using transthoracic echocardiography. Using these parameters, American Heart Association guidelines stratify patients into five groups based upon risk level. Those in the highest risk levels become patients for continual assessment and/or cardiac surgery [13].

The current method by which KD is treated is based on variables that loosely justify specific treatments. This leads to arbitrary choices of surgical techniques that may not be specific to the patient. If more hemodynamic-specific data was present, clinicians could for example decide better on stent sizes for aneurysms with low recirculation and high curvature of tapering. Hospitals need a hemodynamics-based method to determine the type of treatment a specific patient needs, which can help surgeons decide on what surgical method to use and how.

            Hemodynamic variables such as recirculation time of platelets and aneurysm wall shear stress [9-12] are much more specific than the morphological data currently used. Use of such engineering-oriented parameters would prevent unsatisfactory medical outcomes, and help assess patients’ specific needs with much more speed and accuracy. This will also prevent unnecessary calls for surgery, and justify necessity of surgery when not prescribed. The ultimate benefit of a new methodology of treatment is the conservation of time and effort and prevention of patient suffering.

 

Users and Beneficiaries of the Design

Both clinicians and KD patients will benefit from an engineering-based strategy for diagnosis and treatment of KD. Clinicians will be better equipped to make proper decisions about treating KD patients. KD patients will receive treatment specifically targeted for their coronary arteries, breaking the “one-treatment-fits-all” paradigm in medicine.