Apical aortic blood pump preclinical assessment for long-term use: Durability test and stator topology to reduce wear in the bearing system.

This study presents an assessment for long-term use of the apical aortic blood pump (AABP), focusing on wear reduction in the bearing system. AABP is a centrifugal left ventricle assist device initially developed for bridge to transplant application. To analyze AABP performance in long-term applications, a durability test was performed. This test indicated that wear in the lower bearing pivot causes device failure in long-term. A wear test in the bearing system was conducted to demonstrate the correlation of the load in the bearing system with wear. Results from the wear test showed a direct correlation between load and wear at the lower bearing pivot. In order to reduce load, thus reducing wear, a new stator topology has been proposed. In this topology, a radial stator would replace the axial stator previously used. Another durability test with the new stator has accounted twice the time without failure when compared with the original model.

Mock circulatory system for the evaluation of left ventricular assist devices, endoluminal prostheses, and vascular diseases.

A new digital computer mock circulatory system has been developed in order to replicate the physiologic and pathophysiologic characteristics of the human cardiovascular system. The computer performs the acquisition of pressure, flow, and temperature in an open loop system. A computer program has been developed in Labview programming environment to evaluate all these physical parameters. The acquisition system was composed of pressure, flow, and temperature sensors and also signal conditioning modules. In this study, some results of flow, cardiac frequencies, pressures, and temperature were evaluated according to physiologic ventricular states. The results were compared with literature data. In further works, performance investigations will be conducted on a ventricular assist device and endoprosthesis. Also, this device should allow for evaluation of several kinds of vascular diseases.

Clinical evaluation of the Spiral Pump® after improvements to the original project in patients submitted to cardiac surgeries with cardiopulmonary bypass.

OBJECTIVE: The objective of this paper is to present the results from Spiral Pump clinical trial after design modifications performed at its previous project. This pump applies axial end centrifugal hydraulic effects for blood pumping during cardiopulmonary bypass for patients under cardiac surgery. METHODS: This study was performed in 52 patients (51% males), between 20 to 80 (67±14.4) years old weighing 53 to 102 (71.7±12.6) kg, mostly under myocardial revascularization surgery (34.6%) and valvular surgery (32.8%). Besides the routine evaluation of the data observed in these cases, we monitored pump rotational speed, blood flow, cardiopulmonary bypass duration, urine free hemoglobin for blood cell trauma analysis (+ to 4+), lactate desidrogenase (UI/L), fibrinogen level (mg/dL) and platelet count (nº/mm3). RESULTS: Besides maintaining appropriate blood pressure and metabolic parameters it was also observed that the Free Hemoglobin levels remained normal, with a slight increase after 90 minutes of cardiopulmonary bypass. The Lactate Dehydrogenase showed an increase, with medians varying between 550-770 IU/L, whereas the decrease in Fibrinogen showed medians of 130-100 mg/dl. The number of platelets showed a slight decrease with the medians ranging from 240,000 to 200,000/mm3. No difficulty was observed during perfusion terminations, nor were there any immediate deaths, and all patients except one, were discharged in good condition. CONCLUSION: The Spiral Pump, as blood propeller during cardiopulmonary bypass, demonstrated to be reliable and safe, comprising in a good option as original and national product for this kind of application.

Respiraçäo artificial com oxigenador de membrana extracorpóreo em posiçäo artério-venosa sem bomba: estudo experimental / Respiratory Support with Arteriovenous Pumpless Extracorporeal Membrane Oxygenation. An Experimental Study

PURPOSE--To test the hypothesis of respiratory support and to study the consequent hemodynamic alterations, we performed pumpless A-V ECMO using a 1.2m2 polipropylene hollow fiber membrane oxygenator, specially adapted from conventional model utilized in routine cardiac surgery. METHODS--Two canine groups of six dogs each were studied. Group 1 had normal lungs and group 2 acute respiratory failure induced by 0.035ml/kg intravenous oleic acid. The dogs were anesthetized and maintained in apnea with curare. Heparin was given in a single dose of 400U/kg. Gasimetric and hemodynamic parameters were monitored each 30 minutes during a 3 hour period. Then the oxygenator was discontinued and after 15 minutes a final arterial blood gas sample was taken for analysis. RESULTS--Blood samples at 3 hours have shown a mean PaO2 of 260.6mmHg in group 1 and 114.4mmHg in group 2 and PaCO2 of 54.3 and 56.2mmHg, respectively. After the oxygenator was discontinued PaCO2 levels increased to 161.6 and 193.7mmHg, respectively. The hemodynamic parameters shown few alterations. CONCLUSION--In both groups pumpless A-V ECMO was able to maintain gasimetric parameters within acceptable patterns and compatible with life, with few hemodynamic alterations. However, an adequate mean arterial blood pressure is needed to provide flow through membrane oxygenator

Objetivo - Testar a hipótese de manutenção do suporte respiratório e observar as alterações hemodinâmicas provocadas pelo emprego da assistência respiratória extracorpórea por via artério-venosa sem bomba, usando um oxigenador de fibra oca capilar de polipropileno de 1,2m2, especialmente adaptado do modelo utilizado em cirurgia cardíaca de rotina. Métodos - Foram estudados dois grupos de 6 cães cada, sendo o grupo 1 com pulmões normais e o grupo 2 onde se induziu insuficiência respiratória aguda com ácido oléico (0,035ml/kg). Os cães foram mantidos apnéicos durante o experimento com administração continuada de curare. Heparina foi injetada em dose única (400U/kg) e parâmetros gasimétricos e hemodinâmicos foram monitorados cada 30min por 3h. A seguir, foi desligado o oxigenador e 15min depois colhida amostra sangüínea arterial para gasimetria final. Resultados - Amostras sangüíneas coletadas ao final de 3h mostraram média de PaO2 de 260,65mmHg no grupo 1 e 114,4mmHg no grupo 2 e PaCO2 de 54,3 e 56,2mmHg, respectivamente. Quando se desligou o oxigenador, após 15min PaCO2 elevou-se para 161,6 e 193, 7mmHg, respectivamente. Os parâmetros hemodinâmicos mostraram-se estáveis durante o experimento. Conclusão - Em ambos os grupos o método foi capaz de manter os parâmetros gasimétricos dentro de padrões aceitáveis e compatíveis com a vida, com paucas alterações hemodinômicas. Entretanto, necessita pressão arterial média adequada para prover fluxo através do oxigenador de membrana

Aneurismectomia de ventrículo esquerdo. Reconstrução geométrica com utilização de prótese semi-rígida de teflon / Aneurysmectomy of the left ventricle. Geometric reconstruction using a semi-rigid teflon prosthesis

Os autores analisam a experiencia global do servico em 97 pacientes consecutivos e nao selecionados submetidos a 98 aneurismectomias nos ultimos 10 anos. Nao foram incluidos nesta serie pacientes nos quais a aneurismectomia foi procedimento cirurgico coadjuvante da revascularizacao miocardica, mas tao somente aqueles em que o aneurisma ventricular isoladamente se constituia em objeto da indicacao cirurgica. Na experiencia inicial ate 1978, o procedimento cirurgico realizado foi a aneurismectomia classica com sutura direta de seus bordos. A partir de agosto de 1978, para os aneurismas de colo largo passamos a utilizar a tecnica da reconstrucao geometrica proposta por Jatene, com utilizacao de retalho eliptico de dacron para a restauracao da parede ventricular.A finalidade do presente trabalho e apresentar uma protese semi-rigida de teflon que foi desenvolvida visando simplificar a utilizacao tatica deste principio e comparar os resultados obtidos entre os 21 pacientes operados com a tecnica da reconstrucao geometrica, cotejando-os com os 77 procedimentos da reconstrucao classica. Os autores apresentam ainda no trabalho os resultados imediatos e tardios das duas tecnicas assim como discutem os achados angiograficos da ventriculografia esquerda pos-operatoria realizada em 14 dos 77 pacientes em observacao