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Inflammation, Oxidative Stress, Metabolic Inefficiency, And Related Functional Decline of the Heart During Ex-situ Perfusion
- Author / Creator
- Sanaz Hatami
Normothermic ex-situ heart perfusion (ESHP) is an emergent technique that allows for continued perfusion of the beating heart, supplying required oxygen and nutrients. Also, this technique offers a venue to assess the metabolic and functional viability of the donated heart during the period of preservation. However, myocardial function declines gradually during ESHP. In this thesis, we have studied the opportunities, challenges and reliability of the assessment methods for the donor heart in ESHP.
The first chapter is the introduction and provides some background about the preservation methods for the donor heart, limitations of the current standard of care for organ preservation, technology of ESHP, its potentials and limitations, and the need for optimizing devices and protocols.
In chapter two, we have introduced the ESHP apparatus including the operational software both designed in our lab. Using this apparatus, the heart can be perfused with minimal supervision in either empty-beating, non-working mode (NWM), or loaded left ventricle, working mode (WM). The custom-designed software system calculated and records the functional parameters interpreting the data collected from the pressure and flow sensors.
In most, if not all of experimental ESHP studies, and in the clinical setting, the heart has been perfused suspended from the aorta (hanging), in a position considerably different from the in-vivo position in the mediastinum. In chapter three, we showed that while the cardiac function preservation and recovery were both significantly better in the hearts perfused in a semi-anatomical supported position compared to the hearts that were perfused in a suspended position, the perfusate marker of cardiac damage (cardiac troponin-I) was significantly lower in the supported-perfused hearts compared to hanging-perfused hearts.
In chapter four, we demonstrated that the percentage of apoptotic cells only increases very slightly during ESHP, thus it is not explaining the significant decline of the cardiac function occurring during ESHP. However, we showed significant alterations of the metabolic metrics in the ex situ-perfused hearts, suggesting that the energy-yielding metabolism is impaired during perfusion. The alterations in energy-yielding metabolites/metabolism may play a key role in the functional decline of the heart during ESHP.
In chapter five, we demonstrated that the markers of inflammation are considerably elevated in the perfusate during ESHP, which occurred regardless of the left ventricular workload. Also, in general, the endoplasmic reticulum stress responses (ERS, one of the important stress-sensing organelles) were induced during ESHP, however, both ERS and inflammation were significantly higher in the left ventricular tissue of the hearts perfused in WM compared to NWM.
In the setting of extracorporeal circulation, oxidative stress may occur in a persistent fashion, going beyond the ischemia-reperfusion injury-related oxidative stress, and may significantly alter energy metabolism in the cell, especially if the cellular protective systems are impaired. In chapter six, we showed that various markers of oxidative stress were induced in both perfusate and left ventricular tissue of the perfused hearts, while the natural antioxidative defences of the cell decline. The hearts perfused in WM showed better functional preservation, and similar values of some of the enzymes that play important roles in maintaining the metabolic reserve and/or exert protective effects against oxidative stress when compared to in vivo. However, the NWM hearts showed significantly lower activity of those enzymes and poor functional preservation. On the other hand, leukocyte depletion of the perfusate did not attenuate inflammation, oxidative stress, or functional decline of the heart during ESHP.
While the ESHP technique and the related protocols for the protection of the donor heart in this setting has significantly improved during the last decade or so, there are still limitations for this method. This work introduces some areas that can be targeted for improving preservation of myocardial viability during ESHP.
- Graduation date
- Spring 2021
- Type of Item
- Doctor of Philosophy
- This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.