Browsing by Author "Boscan, Pedro, committee member"

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Open Access
Development of an ex vivo pulsatile heart model of functional mitral regurgitation to facilitate posterior papillary muscle geometric studies and subvalvular surgical strategy
(Colorado State University. Libraries, 2018) Kradangnga, Krishaporn, author; Monnet, Eric, advisor; Orton, Christopher, committee member; Boscan, Pedro, committee member; Dasi, Lakshmi P., committee member
Surgical method of choice for functional ischemic mitral regurgitation (FIMR) is debatable, since recurrence of FIMR post-annuloplasty has been reported in significant number of cases. Developing an ex vivo pulsatile functional mitral regurgitation (FMR) heart model by left ventricular (LV) dilatation can be a favorable option for usage in the primary stages of developing new surgical techniques that adjunctively targets the posterior papillary muscle (PPM) geometry. Posterior papillary muscle of ex vivo ovine hearts was displaced by 3 different sizes of patches to induce LV dilatation and FMR. Mitral regurgitation (MR) flow, LV and annular geometry were measured from the dynamic pulsatile flow system before and after patch placement. Applying the large patch produced the highest proportion of FMR heart models (87.5%, P=0.031). In conclusion, the large patch ex vivo pulsatile heart model demonstrated outward displacement of the PPM and significantly produced MR flow. This ex vivo pulsatile heart model can be used to facilitate surgical techniques that targets the PPM displacement in FMR patients. The following phase of our research was aimed to utilize this ex vivo pulsatile heart model for PPM geometric studies in FMR with PPM displacement despite normal mitral annulus. This scenario mimics post-annuloplasty cases when the annular dilatation was corrected by ring annuloplasty but the underlying LV remodeling was not treated. Sonomicrometry was used to evaluate the three-dimensional tethered distances and tethered angles of the PPM due to regional LV dilatation. The findings of this study implied that although annular dilatation was normalized, the increased PPM displacement outside and away from the mitral ring could deteriorate mitral leaflet tethering. The decreased tethering angle of the PPM from the annular fibrosa, reflecting the overall anterior mitral leaflet (AML) tethering and AML bending, could be used for MR prediction. Lastly, the ex vivo pulsatile heart model with PPM lateral displacement and septo-lateral annular dilatation was used to facilitate additional subvalvular surgical strategy. Reduction annuloplasty was used as the standard FIMR treatment but showed suboptimal results with recurrent MR. Post-annuloplasty progression of LV remodeling and papillary muscles displacement could increase leaflet tethering. Annuloplasty alone did not correct submitral problems, therefore, adjunct procedures should be used to address the LV remodeling, prevent recurrent FIMR and insure durability of the balanced mitral complex mechanisms after surgery. In addition to septo-lateral mitral annular reduction, the PPM repositioning was done by using the epicardial apparatus to baso-medially relocate the PPM base toward the mitral fibrosa. The concept of this technique was to reduce the tethering distance of the PPM from the mitral annulus and the interpapillary muscle distance. In conclusion, this study demonstrates the feasibility of an epicardial correction to study geometric changes after mitral annular reduction alone compared to PPM repositioning adjunct with mitral annulus reduction in a pulsatile ex vivo heart model of FMR. This study was aimed to fulfill the gap of the complex FIMR mechanisms and provides preliminary data of the mitral geometry from PPM repositioning outside the LV chamber.
Open Access
Inflammation and apoptosis within the colon from horses with black walnut extract-induced laminitis: prognostic factors after esophageal obstruction in horses
(Colorado State University. Libraries, 2010) Chiavaccini, Ludovica, author; Hassel, Diana M., advisor; Boscan, Pedro, committee member; Bamburg, James R., committee member
To view the abstract, please see the full text of the document.
Open Access
Real-time 2D and 3D electrical impedance tomography and applications
(Colorado State University. Libraries, 2025) Barbosa da Rosa, Nilton, Jr., author; Mueller, Jennifer, advisor; Wilson, Jesse, committee member; Boscan, Pedro, committee member; Simske, Steve, committee member
Electrical impedance tomography (EIT) is a non-invasive and non-ionizing real-time bedside imaging modality for functional pulmonary imaging. The EIT systems produce images of impedance distributions within the body by injecting electric currents and measuring voltages on electrodes applied to the skin. Regional EIT images of ventilation and pulsatile perfusion have the potential to provide information about the lung structure and function of patients with pulmonary diseases. The Adaptive Current Tomograph 5 (ACT5) system is a novel EIT system that can provide 2D and 3D EIT measurements from ventilation and pulsatile perfusion sequences, and simultaneously monitor heart activity by measuring and recording the electrocardiogram (ECG) at all active electrodes while measuring EIT data. This dissertation describes all the components present in the software side of the ACT5 system, which include 2D and 3D EIT reconstruction algorithms, digital filters, a graphical user interface, and the EIT reconstructions on healthy controls and patients with cardiac and pulmonary diseases. To evaluate the potential of EIT on reconstructing pulmonary ventilation and pulsatile perfusion images, EIT reconstructions were performed from data collected on premature babies and patients with cystic fibrosis, acute respiratory distress syndrome, pulmonary vein stenosis, and healthy control subjects. The EIT reconstructions from patients show different ventilation and perfusion distributions when compared to healthy subjects. Lung regions affected by cardiopulmonary diseases can also be identified in the EIT reconstructions.