Effets de la dénudation endothéliale et de la tétrahydrobioptérine sur la fonction endothéliale des artères coronaires épicardiques porcines après transplantation cardiaque

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

Investigation on the Regional Loss Factor and Its Anisotropy for Aortic Aneurysms

An aortic aneurysm is a lethal arterial disease that mainly occurs in the thoracic and abdominal regions of the aorta. Thoracic aortic aneurysms are prevalent in the root/ascending parts of the aorta and can lead to aortic rupture resulting in the sudden death of patients. Understanding the biomechanical and histopathological changes associated with ascending thoracic aortic aneurysms (ATAAs), this study investigates the mechanical properties of the aorta during strip-biaxial tensile cycles. The loss factor—defined as the ratio of dissipated energy to the energy absorbed during a tensile cycle—the incremental modulus, and their anisotropy indexes were compared with the media fiber compositions for aneurysmal (n = 26) and control (n = 4) human ascending aortas. The aneurysmal aortas were categorized into the aortas with bicuspid aortic valves (BAV) and tricuspid aortic valves (TAV). The strip-biaxial loss factor correlates well with the diameter of the aortas with BAV and TAV (for the axial direction, respectively, R2 = 0.71, p = 0.0022 and R2 = 0.54, p = 0.0096). The loss factor increases significantly with patients’ age in the BAV group (for the axial direction: R2 = 0.45, p = 0.0164). The loss factor is isotropic for all TAV quadrants, whereas it is on average only isotropic in the anterior and outer curvature regions of the BAV group. The results suggest that loss factor may be a useful surrogate measure to describe the histopathology of aneurysmal tissue and to demonstrate the differences between ATAAs with the BAV and TAV

Effect of Aortic Valve Replacement for Aortic Stenosis on Severity of Mitral Regurgitation

Background: Surgically addressing moderate mitral regurgitation (MR) at the time of aortic valve replacement (AVR) for aortic stenosis remains uncertain. The purpose of this study was to examine the change in moderate (2+) or moderate-severe (3+) MR after isolated AVR for aortic stenosis to determine preoperative factors predictive of improvement in MR. Methods: Using an institutional databank of prospectively collected data, all patients undergoing isolated AVR for aortic stenosis with moderate (2+) to moderate-severe (3+) MR between 1994 and 1996 at the Montreal Heart Institute were evaluated. Results: Eighty patients with preoperative and postoperative transthoracic echocardiographic follow-up were identified. Preoperative MR was moderate (2+) in 78 patients (97.5%) and moderate-severe (3+) in 2 patients (2.5%). Mitral regurgitation was classified as rheumatic (32%), ischemic (32%), functional (21%), and myxomatous (15%). At 1-year follow-up transthoracic echocardiography, MR improved by 1 or 2 grades in 29 patients (35%), was unchanged in 44 (55%), and worsened in 7 (10%). On multivariate analysis, isolated ischemic and functional MR were the only preoperative factors predictive of MR improvement after AVR (p = 0.01): 54% of ischemic and 44% of functional MR patients showed improvement in MR after AVR compared with 23% of rheumatic and 17% of myxomatous MR patients. Conclusions: Etiology of MR was a significant prognostic factor for improvement in MR grade. Since there was little improvement in the rheumatoid and myxomatous group, replacement or repair should strongly be considered. For functional and ischemic mitral regurgitation, a surgical correction should be performed on an individual basis. © 2007 The Society of Thoracic Surgeons.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Changes in patient characteristics following cardiac transplantation: the Montreal Heart Institute experience

Background Heart transplantation is no longer considered an experimental operation, but rather a standard treatment; nevertheless the context has changed substantially in recent years owing to donor shortage. The aim of this study was to review the heart transplant experience focusing on very long-term survival (≥ 20 years) and to compare the initial results with the current era. Methods From April 1983 through April 1995, 156 consecutive patients underwent heart transplantation. Patients who survived 20 years or longer (group 1) were compared with patients who died within 20 years after surgery (group 2). To compare patient characteristics with the current era, we evaluated our recent 5-year experience (group 3; patients who underwent transplantation between 2010 and 2015), focusing on differences in terms of donor and recipient characteristics. Results Group 1 (n = 46, 30%) included younger patients (38 ± 11 v. 48 ± 8 yr, p = 0.001), a higher proportion of female recipients (28% v. 8%, p = 0.001) and a lower prevalence of ischemic heart disease (42% v. 65%, p = 0.001) than group 2 (n = 110, 70%). Patients in group 3 (n = 54) were older (52 ± 12 v. 38 ± 11 yr, p = 0.001), sicker (rate of hospital admission at transplantation 48% v. 20%, p = 0.001) and transplanted with organs from older donors (42 ± 15 v. 29 ± 11 yr, p = 0.001) than those in group 1. Conclusion Very long-term survival (≥ 20 yr) was observed in 30% of patients transplanted during the first decade of our experience. This outcome will be difficult to duplicate in the current era considering our present population of older and sicker patients transplanted with organs from older donors