Pulmonary edema occurs when fluid leaks from the pulmonary capillary network into the lung interstitium and alveoli. When the heart is not able to pump blood to the body efficiently, fluid can back up into the veins that take blood through the lungs to the left atrium. This then builds up the pressure in the blood vessels and fluid is pushed into the alveoli in the lungs. The fluid reduces normal oxygen movement through the lungs and can cause impaired gas exchange and respiratory failure. There are many causes of congestive heart failure that may lead to pulmonary edema such as heart attack, any diseases of the heart that weaken or stiffen the heart muscle, a leaking or narrowed heart valve, and sudden, severe high blood pressure. Pulmonary edema is a strong indicator of congestive heart failure in patients and therefore can be used as a gauge for congestive heart failure. One way to diagnose cardiogenic pulmonary edema constantly is through the continuous monitoring of the transthoracic impedance throughout the day. One method to achieve this constant monitoring is through the use of a cardiac pacemaker or an implantable cardioverter defibrillator (ICD). Many patients who are at risk of heart failure have these medical devices implanted already. In these implantable cardiac devices, the connected cardiac leads can be utilized to continually screen several impedance vectors for decreases in impedance in the thoracic cavity. A pacemaker or ICD that implements Pulmonary Edema Monitoring is designed to continuously monitor these impedance vectors and alert the patient to seek medical attention. This thesis will discuss the implementation of Pulmonary Edema Monitoring via screening of multiple impedance vectors in a pacemaker or implantable cardioverter defibrillator and the effectiveness of this monitoring method. Furthermore, the design, implementation, and testing of this feature will be explored in greater detail.

Leaflet replacement in aortic valve repair (AVr) is associated with increased long-term repair failure. Hemodynamic performance and mechanical stress levels were investigated after porcine AVr with 5 types of clinically relevant replacement materials to ascertain which material(s) would be best suited for repair. Porcine aortic roots with intact aortic valves were placed in a left-heart simulator mounted with a high-speed camera for baseline valve assessment. Then, the non-coronary leaflet was excised and replaced with autologous porcine pericardium (APP), glutaraldehyde-fixed bovine pericardial patch (BPP; Synovis™), extracellular matrix scaffold (CorMatrix™), or collagen-impregnated Dacron (HEMASHIELD™). Hemodynamic parameters were measured over a range of cardiac outputs (2.5–6.5L/min) post-repair. Material properties of the above materials along with St. Jude Medical™ Pericardial Patch with EnCapTM Technology (SJM) were determined using pressurization experiments. Finite element models of the aortic valve and root complex were then constructed to verify the hemodynamic characteristics and determine leaflet stress levels. This study demonstrates that APP and SJM have the closest profiles to normal aortic valves; therefore, use of either replacement material may be best suited. Increased stresses found in BPP, HEMASHIELD™, and CorMatrix™ groups may be associated with late repair failure.

Leaflet replacement in aortic valve repair (AVr) is associated with increased long-term repair failure. Hemodynamic performance and mechanical stress levels were investigated after porcine AVr with 5 types of clinically relevant replacement materials to ascertain which material(s) would be best suited for repair. Porcine aortic roots with intact aortic valves were placed in a left-heart simulator mounted with a high-speed camera for baseline valve assessment. Then, the non-coronary leaflet was excised and replaced with autologous porcine pericardium (APP), glutaraldehyde-fixed bovine pericardial patch (BPP; Synovis™), extracellular matrix scaffold (CorMatrix™), or collagen-impregnated Dacron (HEMASHIELD™). Hemodynamic parameters were measured over a range of cardiac outputs (2.5–6.5L/min) post-repair. Material properties of the above materials along with St. Jude Medical™ Pericardial Patch with EnCapTM Technology (SJM) were determined using pressurization experiments. Finite element models of the aortic valve and root complex were then constructed to verify the hemodynamic characteristics and determine leaflet stress levels. This study demonstrates that APP and SJM have the closest profiles to normal aortic valves; therefore, use of either replacement material may be best suited. Increased stresses found in BPP, HEMASHIELD™, and CorMatrix™ groups may be associated with late repair failure.