Scientists in Brazil develop an artificial implantable heart

The prototype, built at Universidade de São Paulo and the Dante Pazzanese Cardiology Institute, attempts to help patients with heart problems who are awaiting transplants.

By Karina Toledo

Agência FAPESP – Researchers at the Universidade de São Paulo (USP) and the Dante Pazzanese Cardiology Institute have developed the first Brazilian prototype of a totally implantable artificial heart. The device is recommended for patients with heart failure, a condition that affects 6.5 million people in Brazil and kills approximately 25,000 annually, according to data from the Brazilian Cardiology Society (SBC).

The objective of the implant, which has not yet been tested in humans, is not to replace the heart but rather to help it pump blood while the patient is awaiting a heart for transplant. The first experiments conducted with calves have shown good results.

“In developed countries, there are models of artificial hearts that are totally implantable, but the cost of importing them is high—more than R$ 200,000—leaving few with access. Our idea was to develop a domestic version that costs around R$ 10,000,” explained José Roberto Cardoso, director of USP’s Polytechnic School and coordinator of the FAPESP-funded study.

According to Cardoso, other models of artificial hearts have been developed in Brazil at the USP’s Heart Institute (Incor) and even at Dante Pazzanese. However, all of those devices are extracorporeal. Tubes extending from the patient’s body are connected to a suitcase containing the pump and the battery.

“The patient must carry the suitcase everywhere, and the equipment is in contact with the environment. In addition to the inconvenience, the major problem is the risk of infection,” said Cardoso.

Development of the new implantable prototype began in 2006. The pump was designed in the Poli’s Department of Mechatronics, and the electric motors and circuits that control its operation were created in the Applied Electromagnetism Laboratory, coordinated by Cardoso. The medical aspects and the animal trials were the responsibility of the team at Dante Pazzanese, an institute linked to the State Health Secretariat.

“The majority of the existing models abroad use axial-type pumps, in which the blood enters one end of a tube and exits from the other. We opted for a radial-type pump, in which the blood enters a cylindrical center and exits on the side,” explained Cardoso.

The advantage, according to the researcher, is that the radial pump works at a lower rotation speed. In addition to reducing the noise—an important consideration given that the device is inside the body—the impact on the blood is also lower.

Two types of problems are more worrisome when blood is pressurized in an exaggerated manner: excessive release of hemoglobin by the red blood cells, which can be toxic to the kidneys and the liver, and activation of platelets, which raises the risk of thrombosis.

“For this reason, one of the major challenges is predicting the behavior of blood due to the pump’s pressure,” explained Cardoso. “Blood is a very difficult fluid to model because it is composed of liquid and solid parts, and when your apply pressure, the volume diminishes,” he added. “It is different from water, which always maintains a constant volume. We do simulations through computational tools and experiments in the laboratory to verify whether distribution is occurring at the predicted speed and there are no bottlenecks.”

How it works

The pump was designed to be implanted in a cavity near the heart. It is conical and the size of an orange. Researchers intend to perfect the device and make it smaller.

The team consulted Adib Jatene, director of Incor, to define the ideal shape of the pump and the most appropriate implantation site.

The pump includes a box that holds the electronic circuits located near the pump and a coil that is close to the skin and serves to recharge the device.

“Another major challenge to making an implantable device is finding a good way to charge it. We developed a method that works by induction, or, rather, a coil is placed on top of the skin and a current runs through it. This produces a magnetic field that induces a current in an internal coil and charges the battery,” explained Cardoso.

Scientists estimate that the battery would need to be charged daily, but the process would take only 40 minutes. The patient would carry a small charger, connect it to an outlet and place the coil underneath the clothing.

The method worked well in laboratory tests in which the scientists used a layer of water to simulate the characteristics of the skin. However, Cardoso warns that new experiments must be conducted in vivo to be sure that the electric current used will not harm the tissue.

The pump has been tested in calves, the researcher noted, “but we left the device outside the animal’s body to evaluate whether the volume of blood pumped was adequate and if the pressure was correct. Now we want to do new experiments with implanted devices, and we will have to leave some wires outside to do the measurements.”

In this second stage of the study, explained Cardoso, the target is to transform the prototype into a product to compete with the existing models on the foreign market.

“In addition to how it works, we must evaluate other parameters like heating, noise and adjusting the circuit to reduce the size even further. There is a series of problems that are mechanical and electrical in nature that must be addressed to reach a minimal size,” he commented.

The experiments conducted to date have resulted in the publication of 50 articles in scientific journals and presentations at scientific meetings. Among the main articles are the following:

Implantable Centrifugal Blood Pump With Dual Impeller and Double Pivot Bearing System: Electromechanical Actuator, Prototyping, and Anatomical Studies (doi: 10.1111/j.1525-1594.2011.01260.x), which can be read at onlinelibrary.wiley.com/doi/10.1111/j.1525-1594.2011.01260.x/abstract;jsessionid=44D65CAF0028C0E2546814DE6BEB6A30.d02t04.

Specification of Supervisory Control Systems for Ventricular Assist Devices (doi: 10.1111/j.1525-1594.2011.01267.x), which can be read at onlinelibrary.wiley.com/doi/10.1111/j.1525-1594.2011.01267.x/abstract.

Single Axis Controlled Hybrid Magnetic Bearing for Left Ventricular Assist Device: Hybrid Core and Closed Magnetic Circuit (doi: 10.1111/j.1525-1594.2011.01265.x), which can be read at onlinelibrary.wiley.com/doi/10.1111/j.1525-1594.2011.01265.x/abstract.