CARMO GALLO NETTO

ACardiac diseases can occur in varying degrees. The most serious ones require transplantation and many others resolve with recovery of the myocardium, as they mainly affect the left ventricle. In these two situations, blood pumps for cardiac assistance can play a fundamental role. In the first case, by keeping the patient alive while he waits for the transplant – in Brazil, the average waiting time is six months. In the second, because, when installed in the left ventricle, they can contribute to the recovery of the heart muscle.

These two main applications, called by experts “bridge to transplantation” and “bridge to recovery”, motivated mechanical engineer Eduardo Guy Perpétuo Bock, supervised by professor Antonio Celso Fonseca de Arruda, from the Department of Materials Engineering at the Faculty of Mechanical Engineering (FEM) at Unicamp, developing an implantable centrifugal pump with a simpler design, longer duration and significantly lower cost than conventional imported pumps. The research supported his master's thesis.

The project was developed in cooperation with the Instituto Dante Pazzanese de Cardiologia in São Paulo, with the co-guidance of professor Aron José Pazin de Andrade, and the Baylor College of Medicine in Houston – USA –, where it had the collaboration of professor Yukihiko Nosé, one of the pioneers in the development of mechanical equipment for cardiac purposes. The work was funded by Capes, CNPq, Fapesp and Funcamp.

Artificial ventricle – Bock explains that to treat heart disease, there are three types of pumps: pulsatile, axial and centrifugal. As the Instituto Dante Pazzanese is already developing a pulsatile pump and the Instituto do Coração, the axial one, the idea of ​​developing a centrifugal pump, more appropriately called a ventricular assist device, arose. It does not replace the natural organ, but, connected to the left ventricle, works in parallel with it as an artificial ventricle, helping to pump blood to the aorta, relieving the work of the myocardium.

Although the three types have their applications, centrifugal pumps – which make up the third generation – constitute a global trend. Bock clarifies the concepts that guided the work: “We developed a simpler model than the existing ones, and we used more resistant materials so that the equipment would have greater durability. Furthermore, we aim to master a technology developed only in a few central countries and at a very high cost. This ends up making its use unfeasible in Brazil.”

Greater durability – For Bock, what distinguishes his proposal from American, Australian and Japanese bombs is the fact that the team opted for a simplified design. “We use high-resistance materials in the bearings, such as alumina and polyethylene. Instead of using bearings, which are susceptible to extensive wear, or electromagnetic suspension, like those on the Japanese bullet train, which makes the device very expensive, we opted for a polymeric-ceramic system to support the rotor. This is one of the great innovations.” As a result, explains the researcher, the device's durability reaches more than five years, while pumps that work in the conventional mechanical system do not last more than two years.

According to Bock, the project was not based on copying a technology, but focused on developing a more suitable and accessible device that reached the same quality as existing ones, in addition to not causing hemolysis, which is the destruction of red cells. of blood, which required an adequate design of the rotor.

Although he notes that some of the pumps available on the international market cost more than 300 thousand dollars, the researcher considers that, more than reducing the cost, a national project includes the development of an infrastructure that will allow the device to be used. “Today, there is no possibility of importing these pumps because their implementation would require a patient support structure that does not exist in the country. Furthermore, its installation would be very expensive and complex. The development of a national technology naturally leads to the creation of ventricular assistance necessary for patient care.”

Tests were carried out in the USA

The selection of the most suitable materials for the bearings, the study of the most suitable design for the rotor and the construction of the prototype were carried out in Brazil. However, tests for acceptance of this type of device remained. They allow checking the occurrence of hemolysis and are carried out in vitro, according to current technical standards. Encouraged by professor Celso Arruda, Bock went to perform them at Baylor College of Medicine, in Houston, where he stayed for seven months. He considered the experience “unique”, mainly due to his interaction with professor Yukihiko Nosé, who suggested and paid for the construction of another prototype.

The tests were carried out with human blood. Based on the results, Bock considers that the implantable centrifugal pump designed and developed showed excellent performance in in vitro tests, revealing itself to be a promising possibility for use in cardiac patients with indications for ventricular assistance. “The device proved to be cheap, reliable and showed results in relation to hemolysis that were as good or better than others that do not have such a simple internal solution”, assesses the researcher.

In bench tests, the prototypes were built in acrylic to facilitate observation. Having completed his master's work, Eduardo Bock intends to begin, now in his doctorate, the manufacture of a new pump, without dimensional changes, but in biocompatible material, such as titanium.

Future tests with this new pump must be carried out on animals and will serve to improve the various subsystems that must make up a device implantable in humans. Once these steps have been completed, the device can be implanted in patients at the Dante Pazzanese Institute, which will allow for a thorough clinical evaluation.

Bock emphasizes that the results obtained must be credited to a team made up of professors and researchers from Unicamp and institutions in which they worked in cooperation. He makes a point of highlighting that Brazil, despite being a developing country, is a leader in cardiological technology and has institutions that are on par with those in first world countries. Bock also highlights the social reach of the work carried out by the institutions involved: “Many patients die on the transplant waiting list or live tied to a bed because they do not have adequate equipment available. Furthermore, this type of centrifugal pump, which enables myocardial recovery, increasingly reduces the need for transplantation.”

How works

Implanted in the thoracic cavity, a cannula installed in the left ventricle is connected to the pump inlet. At the exit, another cannula takes the pumped blood to the aorta. The pump works in parallel with the heart, reducing the pressure that the left ventricle would have to overcome to take blood to the aorta. The reduction in the work carried out by the myocardium leads in many situations to the recovery of the heart muscle. The illustrations show the implantable centrifugal pump. The device is no bigger than a tennis ball, but conical in shape.