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Development of Energy-Based Endpoints for diagnosis of Pulmonary Valve Insufficiency

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2013, PhD, University of Cincinnati, Engineering and Applied Science: Mechanical Engineering.
Introduction. Pulmonary insufficiency (PI) causes myocardial dysfunction and hypertrophy in the right ventricle; with fatal consequences in some cases. The only remedy is pulmonary valve (PV) replacement surgery, the timing of which is critical. Surgery performed earlier than neces-sary leads to a re-emergence of PI, whereas a delayed intervention can potentially render the re-placement futile. There are no physiological markers to determine the correct window for this surgery. Clinicians currently rely on subjective assessment of cardiac MRI scans and evaluation of a few ad-hoc measures, such as end-diastolic pressure, cardiac volume and regurgitant frac-tion. The use of these different measures often results in conflicting conclusions and error-prone decisions. Thus, a quantitative index is required to unambiguously assess the progression of PI to determine the correct window for the PV replacement surgery. In this research, a set of energy-based endpoint were investigated that combined the pressure and volumetric measures. Right ventricular (RV) stroke work, energy loss in the branch pulmonary artery (PA) and a new end-point, energy transfer ratio defined as the ratio of the total blood energy at the main PA and stroke work were developed and tested as a proof-of-concept. Methods. The energy based endpoints were obtained for a normal and a diseased subject. Pres-sure measurements obtained invasively from cardiac catheterization, and flow rate and ventricu-lar volume obtained non-invasively from MRI scans were utilized for the calculation. Subsequently, methodologies to obtain these endpoints in a completely non-invasive ap-proach, using patient-specific image-based hemodynamic models were developed to eliminate the requirement of invasive catheterization. Angiographic MRI was used for geometry recon-struction for image-based models. Actual time- and spatially- varying velocity profiles, directly obtained from phase-contrast MRI were used for patient-specific velocity boundary conditions. Flow rates from the numerical models were validated with ones obtained from a standard of care measurement. Finally, the arterial wall compliance was incorporated in the computational mod-els. The in-vivo wall pre-stress was calculated by developing a nonlinear least-square based in-verse elastostatics algorithm called the shrink-and-fit inverse method. Results. The RV stroke work for the normal subject (0.115 J) was 32% higher than that of the subject with PI (0.078 J). The energy transfer ratio for the normal subject (1.06) was nearly two times that of the subject with PI (0.56). Validation of non-invasive method: The maximum difference between the flow rate from com-putation with time- and spatially-varying velocity boundary conditions and the one from standard of care measurement was 7 ml/sec at the main PA of the diseased subject. The computed flow rates for the normal subject were within 3.4% (2 ml/sec) of the measured values at each of the inlet and outlets. For the compliant arterial wall model, the shrink-and-fit inverse algorithm matched the in-vivo and pre-stressed artery geometry within 0.0015 mm. Conclusions. The energy-based endpoints were able to delineate a normal physiology from a PI pathophysiology. These endpoints have the potential to improve the diagnosis of PI by eliminat-ing the ambiguity resulting from the use of either pressure-based or volume-based measures.
Rupak Banerjee, Ph.D, P.E. (Committee Chair)
Kan Hor, M.D. (Committee Member)
Michael Taylor, M.D., Ph.D. (Committee Member)
Teik Lim, Ph.D. (Committee Member)
Kumar Vemaganti, Ph.D. (Committee Member)
Janaka Wansapura, Ph.D. (Committee Member)
228 p.

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Citations

  • Das, A. (2013). Development of Energy-Based Endpoints for diagnosis of Pulmonary Valve Insufficiency [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1384864758

    APA Style (7th edition)

  • Das, Ashish. Development of Energy-Based Endpoints for diagnosis of Pulmonary Valve Insufficiency. 2013. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1384864758.

    MLA Style (8th edition)

  • Das, Ashish. "Development of Energy-Based Endpoints for diagnosis of Pulmonary Valve Insufficiency." Doctoral dissertation, University of Cincinnati, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1384864758

    Chicago Manual of Style (17th edition)