Cardiac Biomechanics Research
Cardiac Biomechanics Research
Aortic Disease and Intervention
Ascending Thoracic Aortic Aneurysm and Dissection Approximately 30,000 people in the US are diagnosed with thoracic aortic aneurysms every year. Patients that experience the devastating event of rupture or dissection face up to 60% mortality.Currently, aTAA elective surgical repair is based primarily on aneurysm diameter or growth rate, with a ≥ 5.5cm diameter threshold for surgery in patients without connective tissue disorders or family history of dissection, rupture, or aneurysms. However, studies have demonstrated that a majority of aTAA rupture/dissection
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Computational Simulation of Transcatheter Aortic Valve Replacement (TAVR) Aortic stenosis (AS) is the most common heart valve disease encountered in the elderly. The aortic valve leaflets become restricted due to excessive calcium buildup. In the past, surgical aortic valve replacement (SAVR) was the gold standard to treat patients with severe AS, which entailed opening the chest and placing the patient on cardiopulmonary bypass. Today, many patients are eligible for a minimally invasive alternative therapy called transcatheter aortic valve replacement (TAVR)
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Passive Constraint The Acorn CorCap TM Cardiac Support Device (CSD) (Acorn Cardiovascular, Inc., St.Paul, MN) is a bidirectional woven polyester yarn jacket placed over the left (LV) and right ventricles (RV) in patients with dilated cardiomyopathy and heart failure. The underlying hypothesis is that the CSD will reduce strain and stress associated with progressive ventricular dilation. As a consequence, LV remodeling will halt or reverse cardiac remodeling, and systolic LV function will be chronically improved. Pre-clinical studies showed that the
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The Ross Procedure and Pulmonary Autograft Biomechanics For the pediatric and adolescent patients diagnosed with aortic valve disease, a major challenge is determining the optimal surgical treatment. Bioprosthetic tissue valves degenerate over several years, while mechanical valves necessitate anticoagulation. Both of these also pose additional dilemma for the growing patient, and require repeated surgery to implant a larger valve. The Ross procedure is the only procedure that transplants a living valve to the aortic valve position, using the patient’s own
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Transcatheter Aortic Valves Aortic stenosis (AS), due to accumulation of calcium in the valve leaflets, is a major heart valve disease encountered in the elderly. Surgical aortic valve replacement (AVR) is still the gold standard to treat patients with severe AI or AS. AVR is performed with excellent results, including low mortality and good long-term survival. Recently, percutaneous aortic stent valves have been implanted clinically in select patients. However, they have not been rigorously evaluated with respect to their biomechanical
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Left Ventricular and Mitral Valve Disease
Borderzone Dysfunction It has been known since the mid 1980s that systolic performance (systolic shortening and wall thickening) is depressed in the non-ischemic borderzone (BZ) after antero-apical myocardial infarction (MI). It was initially thought that the reduced BZ function was due to mechanical tethering by the infarct. However, finite element based inverse calculations of regional contractility (i.e., active force/stress development), in which optimization routines attempt to match computed and experimentally measured LV volume and strain, suggest that BZ contractility is
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Ischemic Mitral Regurgitation Ischemic mitral regurgitation (MR) affects 1.2 to 2.1 million patients in the United States, with more than 400,000 patients having moderate-to-severe MR. Chronic ischemic MR of 2+ severity discovered at cardiac catheterization for symptomatic coronary artery disease has a 1-year mortality of approximately 17% and the one year mortality for 3+ and 4+ ischemic MR is approximately 40%. Ischemmic MR is usually managed with mitral annuloplasty alone. However, the need for surgical therapy and the type of
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Surgical Ventricular Remodeling Initially described by Dor in 1989, endoventricular patch plasty (Dor procedure) is used to reduce left ventricular (LV) volume after myocardial infarction (MI) and subsequent LV remodeling. Briefly, the infarct is incised and a purse-string suture (Fontan Stitch) is used to reduce the circumference of the aneurysm "neck". A patch of either autologous or synthetic material is then sewn to the edge of the aneurysms neck thereby reducing LV volume. The Dor procedure can be performed safely
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Research Tools
Bi-axial Stretching Apparatus We utilize a custom made biaxial stretcher to determine the biaxial stiffness of certain biologic [Gundiah et al, J Mech Behav Biomed Mater, 2: 288, 2009] and device related materials [Gundiah et al, Ann Thorac Surg, 85, 1631, 2008].
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Finite Element Models a. Left Ventricular (LV) Model FE models of the LV that incorporate myocardial contractility have been described and used to determine the effect of myocardial infarction on structure and function. We believe that large deformation finite element models of the LV are extremely powerful because of their ability to accurately calculate stress in the myofiber direction [Zhang et al, Ann Thorac Surg, In Press]. More important finite element models of this sort can simulate the effect of
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Magnetic Resonance Imaging (MRI) Our experimental method is cardiac MR imaging with tags. MR images are contoured and used as the basis for finite element models. In addition, 3D strain is calculated from the tag lines. 3D myocardial strain before and after surgical remodeling has inherent value [Zhang, et al, J Thorac Cardiovasc Surg, 134: 1017, 2007] but we also use the calculated strain as the 'gold standard' when optimizing material properties.
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