Virtual implantations to transition from porcine to bovine animal models for a total artificial heart.

Realheart total artificial heart (TAH) is a novel, pulsatile, four-chamber total artificial heart which had been successfully tested acutely in a porcine animal model. However, the bovine model is better suited for long-term testing and thus an evaluation of how the design would fit the bovine anatomy was required. Virtual implantation is a method that enables a computer simulated implantation based on anatomical 3D-models created from computer tomography images. This method is used clinically, but not yet adopted for animal studies. Herein, we evaluated its suitability in the redesign of the outer dimensions and vessel connections of Realheart TAH to transition from the porcine to the bovine animal model. Virtual implantations in combination with bovine cadaver studies enabled a series of successful acute bovine implantations. Virtual implantations are a useful tool to replace the use of animals in early device development and refine subsequent necessary in vivo experiments. The next steps are to carry out human virtual implantations and cadaver studies to ensure the design is optimized for all stages of testing as well as the final recipient.

Gastrointestinal microcirculation and cardiopulmonary function during experimentally increased intra-abdominal pressure.

OBJECTIVES: The aim of this study was to assess gastric, intestinal, and renal cortex microcirculation parallel with central hemodynamics and respiratory function during stepwise increase of intra-abdominal pressure (IAP). DESIGN: Prospective, controlled animal study. SETTING: Research laboratory, University Hospital. SUBJECTS: Twenty-six anesthetized and mechanically ventilated pigs. INTERVENTIONS: Following baseline registrations, CO2 peritoneum was inflated (n = 20) and IAP increased stepwise by 10 mm Hg at 10 mins intervals up to 50 mm Hg and subsequently exsufflated. Control animals (n = 6) were not insufflated with CO2. MEASUREMENTS AND MAIN RESULTS: The microcirculation of gastric mucosa, small bowel mucosa, small bowel seromuscular layer, colon mucosa, colon seromuscular layer, and renal cortex were selectively studied at all pressure levels and after exsufflation using a four-channel laser Doppler flowmeter (Periflex 5000, Perimed). Central hemodynamic and respiratory function data were registered at each level and after exsufflation. Cardiac output decreased significantly at IAP levels above 10 mm Hg. The microcirculation of gastric mucosa, renal cortex and the seromuscular layer of small bowel and colon was significantly reduced with each increase of IAP. The microcirculation of the small bowel mucosa and colon mucosa was significantly less affected compared with the serosa (p < 0.01). CONCLUSIONS: Our animal model of low and high IAP by intraperitoneal CO2-insufflation worked well for studies of microcirculation, hemodynamics, and pulmonary function. During stepwise increases of pressure there were marked effects on global hemodynamics, respiratory function, and microcirculation. The results indicate that intestinal mucosal flow, especially small bowel mucosal flow, although reduced, seems better preserved in response to intra-abdominal hypertension caused by CO2-insufflation than other intra-abdominal microvascular beds.

Risk factor analysis of Swedish Left Ventricular Assist Device (LVAD) patients.

BACKGROUND: The use of left ventricular assist devices (LVADs) is established as a bridge to heart transplantation. METHODS: All Swedish patients on the waiting list for heart transplantation, treated with LVAD since 1993 were retrospectively collected into a database and analyzed in regards to risk factors for mortality and morbidity. RESULTS: Fifty-nine patients (46 men) with a median age of 49 years (range, 14 to 69 years), Higgins score median of 9 (range, 3 to 15), EuroScore median of 10 (range, 5 to 17) were investigated. Dominating diagnoses were dilated cardiomyopathy in 61% (n = 36) and ischemic cardiomyopathy in 18.6% (n = 11). The patients were supported with LVAD for a median time of 99.5 days (range, 1 to 873 days). Forty-five (76%) patients received transplants, and 3 (5.1%) patients were weaned from the device. Eleven patients (18.6%) died during LVAD treatment. Risk factor analysis for mortality before heart transplantation showed significance for a high total amount of autologous blood transfusions (p < 0.001), days on mechanical ventilation postoperatively (p < 0.001), prolonged postoperative intensive care unit stay (p = 0.007), and high central venous pressure 24 hours postoperatively and at the final measurement (p = 0.03 and 0.01, respectively). Mortality with LVAD treatment was 18.6% (n = 11). High C-reactive protein (p = 0.001), low mean arterial pressure (p = 0.03), and high cardiac index (p = 0.03) preoperatively were risk factors for development of right ventricular failure during LVAD treatment. CONCLUSIONS: The Swedish experience with LVAD as a bridge to heart transplantation was retrospectively collected into a database. This included data from transplant and nontransplant centers. Figures of mortality and morbidity in the database were comparable to international experience. Specific risk factors were difficult to define retrospectively as a result of different protocols for follow-up among participating centers.