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The blood compatibility of the jellyfish valve was studied. Artificial heart (AH) blood pumps incorporating jellyfish valves were connected to 18 goats as total artificial hearts (TAHs) and pumped for 1 to 125 days without anticoagulant or antiplatelet drugs. No thrombus was formed on the valve membrane or around the valve seat. Scanning electron microscopy showed almost no platelet deposition or microfibrin clot formation on the valve membrane, including its central region; the spokes of the valve seat were also free from platelet and microfibrin clots. No calcification was observed during these tests, and plasma free hemoglobin was between 2 and 7 mg/dl. The jellyfish valve revealed good blood compatibility, even without anticoagulant use.

A completely implantable, one piece electromechanical total artificial heart (TAH) intended for permanent human use was developed. It consisted of left and right conically shaped pusher-plate blood pumps sandwiching a thin centerpiece with a compact, efficient electromechanical actuator. The actuator consisted of a direct current brushless motor; a planetary roller screw fit the space between the two conically shaped pusher-plates. The rotational motion of the motor was converted to the rectilinear motion of the rollerscrew to displace the left and right pusher-plates in the left master alternate mode. The diameter of the assembled TAH was 97 mm, with a central thickness of 82 mm. The overall weight was 620 g, with a displaced volume of 510 ml. The pump provided flows of 3-8 L/min with a preload of 1-15 mmHg against an afterload of 100 mmHg. The net efficiency ranged from 15% to 18%. This model showed good fit in the pericardial space of heart transplant recipients (body weight, 77 kg).

Peripheral circulation (PC) during nonpulsatile (NP) perfusion is not satisfactorily understood, although it is known that animals can survive with chronic NP flow. In awake goats, PC was analyzed by hemodynamic and hormonal parameters, tissue blood flow of the ear measured by a noninvasive laser Doppler flowmeter, and distribution of the body surface temperature monitored by thermography. An NP systemic circulation was established in five 40-64 kg goats with a centrifugal pump (MD-10, Iwaki Pump, Japan) that replaced a pulsatile ventricular assist device 2 weeks postoperatively; this was done without anesthesia. Nonpulsatile total left heart bypass was obtained, with flow rates of 78-165 ml/kg/min. Systemic vascular resistance and blood adrenalin and noradrenalin levels were not affected by the depulsation. Tissue blood flow during NP perfusion was well maintained and showed comparable values to those during pulsatile systemic circulation. Vasomotion of 10-20 cycles/min was obvious in the tissue blood flow pattern, indicating adequate PC at each sampling point. Thermography before and after depulsation indicated no change of temperature distribution, and displayed warm peripheral areas. In conclusion, PC of animals on chronic NP systemic perfusion is adequately maintained.

We studied the effect of endothelial cell (EC) senescence on proliferation, migration, and endothelialization in vitro using a culture model. Two generations of cultured bovine aortic ECs were used. The results showed that 1) the senescent ECs had much reduced rates of proliferation, migration, and endothelialization in vitro, and 2) that the young ECs at the leading edge gradually developed morphology similar to that of the senescent ECs as endothelialization proceeded. Computerized videomicroscopic observation revealed that the ECs at the leading edge had higher motile activity than the ECs at the back. This suggests that the ECs at the leading edge, and circumvented from contact inhibition, may proliferate much more frequently than the ECs at the back. Localized cellular aging may result in decelerated or incomplete endothelialization, as found clinically.

Resistance to urea diffusion among body fluid compartments diminishes the therapeutic effectiveness of hemodialysis. Cell membrane or capillary wall resistance is thought to be responsible for hemodialysis-induced urea disequilibrium. The authors examined the possibility that reduced blood flow might contribute to urea disequilibrium in the arm opposite the blood access site. Blood samples were taken simultaneously from a vein in the arm opposite the access site and from the arterial port after occluding the access graft between the needle sites for 1 min. Venous urea nitrogen levels from the opposite arm averaged 10% higher after 5 min, 26% higher after 60 min, and 36% higher after 120 min of dialysis. A three-compartment model of urea kinetics that includes a blood flow term accurately predicted all measured urea nitrogen concentrations in both arms. These data suggest that the opposite arm often behaves as a compartment with high resistance to urea diffusion. Slow diffusion from this compartment is partially due to reduced blood flow/compartment volume, and results in a delayed fall in venous blood urea nitrogen (BUN).

A new aortic prosthesis (SAP, shape memory aortic prosthesis) was developed with its transfemoral placement system to treat aortic dissection with minimal invasion. The SAP consists of a Nitinol stent and polyurethane tube, and it is designed in such a configuration that it can be compressed inside a 14 Fr catheter when cold. It regains its original shape when warmed to 30 degrees C. From the results of intra-aortic sutureless placement of SAP in 10 mongrel dogs, we concluded that a SAP of proper diameter could be implanted safely for more than 3 months. The transfemoral placement system is composed of a delivery catheter, pushing rod, catching catheter, and pulling wire. Using these devices, transfemoral placement of SAP was demonstrated successfully in three dogs and one sheep. The original SAP and delivery system can be used as an emergency procedure for aortic dissections, such as Stanford type B. The advantages of the procedure are minimal invasion of acutely ill patients and prompt application in the catheter laboratory.

A retrospective analysis was performed to assess the effects of univentricular support on the transpulmonary gradient (TPG), pulmonary vascular resistance (PVR), total pulmonary resistance (TPR), and right ventricular ejection fraction (RVEF) in 16 patients who spent from 2 to 144 days (mean, 61) on the Novacor left ventricular assist system ([LVAS] Novacor Corp., Baxter Healthcare, Oakland, CA) as a bridge to cardiac transplantation. Results revealed a significant reduction in the TPR, and improvement in RVEF while patients were on the LVAS. After orthotopic heart transplantation (OHTx), TPG and PVR were significantly lower than when calculated before support. It was concluded, therefore, that the reduction in the TPR and the improvement in the RVEF, seen in patients who were provided univentricular support with the Novacor LVAS, are associated with a significant reduction in the TPG and the PVR, which are persistent after OHTx. Four patients who otherwise would have been considered at higher risk for OHTx because of elevated pulmonary resistance before veniventricular support underwent successful OHTx after LVAS support.

Monthly urea kinetic modeling is performed [service Kt/V (urea)] to ensure that dialysis prescriptions provide patients a Kt/V greater than or equal to 1 and yield a protein catabolic rate (PCR) greater than or equal to 0.8. The frequency with which the dialysis prescription (physician's order +/- 5%, p +/- 5%) was achieved was calculated by three methods: 1) CompuMod (3 ureas; computer derived), 2) Jindal-Goldstein, and 3) Daugirdas, (2 and 3% reduction of urea). Ten patients were followed serially over 1 month for a total of 120 dialyses. Mean Kt/V values for each method were: prescription, 1.54 +/- 0.36; service, 1.40 +/- t0.63; CompuMod, 1.33 +/- 0.27; Jindal-Goldstein, 1.55 +/- 0.24; and Daugirdas, 1.33 +/- 0.23. The percentages of dialyses within the p +/- 5% were 12.4%, CompuMod; 12.8%, Jindal-Goldstein and 14.3%, Daugirdas. The percentages above p +/- 5% were 20.4%, CompuMod; 47%, Jindal-Goldstein; and 21.4%, Daugirdas. The percentages below p +/- 5% were 67.3%, CompuMod; 40.2%, Jindal-Goldstein; and 64.3%, Daugirdas. The CompuMod and Daugirdas methods of assessment of Kt/V were significantly lower (p less than 0.001) than the prescribed Kt/V, whereas the Jindal-Goldstein estimate was not. The authors conclude that dialysis patients rarely achieve their prescribed Kt/V. The service Kt/V, therefore, is not a useful parameter for prescribing dialysis therapy. The CompuMod and Daugirdas methods are the best estimates of the Kt/V, while the Jindal-Goldstein equation overestimates the Kt/V. The need for frequent urea kinetic modelling is stressed. An online urea monitor for each dialysis would be the ideal solution.

Thrombin generation measured after LVAS (4 patients) and TAH (1 patient) implantation was found to be elevated (3 times normal) in the first postoperative week and declined to normal levels when anticoagulation was begun. Thrombin generation was not elevated at the times of thromboembolic events (TIAs; N = 4 episodes).

The use of permanent double lumen hemodialysis catheters (PermCath, Quinton, Seattle, WA) was surveyed in 17 dialysis units with a total of 1,372 patients. During the period of study, 210 patients received or already had such catheters. Their use varied widely, being highest in units dialyzing many older patients with associated diseases and difficulties with vascular access. Flow problems occurred in 46% and clotting in 24%; 27% required urokinase (at least once), and 10% received some form of anticoagulation. Local infections occurred in 15% and septicemia (at least once) in 15%. Some older patients elected to continue with this form of "painless" dialysis.