Development of a disposable magnetically levitated centrifugal blood pump (MedTech Dispo) intended for bridge-to-bridge applications--two-week in vivo evaluation.

Last year, we reported in vitro pump performance, low hemolytic characteristics, and initial in vivo evaluation of a disposable, magnetically levitated centrifugal blood pump, MedTech Dispo. As the first phase of the two-stage in vivo studies, in this study we have carried out a 2-week in vivo evaluation in calves. Male Holstein calves with body weight of 62.4­92.2 kg were used. Under general anesthesia, a left heart bypass with a MedTech Dispo pump was instituted between the left atrium and the descending aorta via left thoracotomy. Blood-contacting surface of the pump was coated with a 2-methacryloyloxyethyl phosphorylcholine polymer. Post-operatively, with activated clotting time controlled at 180­220 s using heparin and bypass flow rate maintained at 50 mL/kg/min, plasma-free hemoglobin (Hb), coagulation, and major organ functions were analyzed for evaluation of biocompatibility. The animals were electively sacrificed at the completion of the 2-week study to evaluate presence of thrombus inside the pump,together with an examination of major organs. To date, we have done 13 MedTech Dispo implantations, of which three went successfully for a 2-week duration. In these three cases, the pump produced a fairly constant flow of 50 mL/Kg/min. Neurological disorders and any symptoms of thromboembolism were not seen. Levels of plasma-free Hb were maintained very low. Major organ functions remained within normal ranges. Autopsy results revealed no thrombus formation inside the pump. In the last six cases, calves suffered from severe pneumonia and they were excluded from the analysis. The MedTech Dispo pump demonstrated sufficient pump performance and biocompatibility to meet requirements for 1-week circulatory support. The second phase (2-month in vivo study) is under way to prove the safety and efficacy of MedTech Dispo for 1-month applications.

Pravastatin treatment before coronary artery bypass grafting for reduction of postoperative atrial fibrillation.

PURPOSE: The aim of this observational study was to determine the incidence of atrial fibrillation (AF) after coronary artery bypass grafting (CABG) in patients with or without preoperative pravastatin treatment. METHODS: Between January 2005 and December 2007, a total of 195 patients (39 women, mean age 66.5 +/- 10.2 years) who underwent CABG only were enrolled in this study. Patients were divided into three groups: nonstatin group (n = 111), atorvastatin group (n = 63), pravastatin group (n = 21). The endpoint of the study was the occurrence of new-onset AF during the first 14 days after CABG. RESULTS: Postoperative AF was less frequent in the pravastatin group (9.5%, 2/21 patients) than in the nonstatin group (34.2%, 38/111 patients; P = 0.0025) and the atorvastatin group (34.9%, 22/63 patients; P = 0.0257). C-reactive protein levels were lower in the pravastatin group 72 h after surgery (nonstatin vs. pravastatin, P = 0.0180; atorvastatin vs. pravastatin, P = 0.0383). The Kaplan-Meier analysis showed the protective effect of pravastatin against the risk of developing AF (nonstatin vs. pravastatin, P = 0.0369; atorvastatin vs. pravastatin, P = 0.0378). Multivariable analysis showed that pravastatin treatment conferred a reduced risk of AF (odds ratio 0.22, 95% confidence interval 0.05-0.92, P = 0.0172). CONCLUSION: Pravastatin treatment before CABG may decrease the incidence of postoperative AF.

Development of a disposable maglev centrifugal blood pump intended for one-month support in bridge-to-bridge applications: in vitro and initial in vivo evaluation.

MedTech Dispo, a disposable maglev centrifugal blood pump with two degrees of freedom magnetic suspension and radial magnetic coupling rotation, has been developed for 1-month extracorporeal circulatory support. As the first stage of a two-stage in vivo evaluation, 2-week evaluation of a prototype MedTech Dispo was conducted. In in vitro study, the pump could produce 5 L/min against 800 mm Hg and the normalized index of hemolysis was 0.0054 +/- 0.0008 g/100 L. In in vivo study, the pump, with its blood-contacting surface coated with biocompatible 2-methacryloyloxyethyl phosphorylcholine polymer, was implanted in seven calves in left heart bypass. Pump performance was stable with a mean flow of 4.49 +/- 0.38 L/min at a mean speed of 2072.1 +/- 64.5 rpm. The maglev control revealed its stability in rotor position during normal activity by the calves. During 2 weeks of operation in two calves which survived the intended study period, no thrombus formation was seen inside the pump and levels of plasma free hemoglobin were maintained below 4 mg/dL. Although further experiments are required, the pump demonstrated the potential for sufficient and reliable performance and biocompatibility in meeting the requirements for cardiopulmonary bypass and 1-week circulatory support.