The propeller in the heart
With a myocardial infarction, every second is precious. Doctors should act as quickly as possible in order to stabilize the patient's condition and prevent further heart damage. In many cases, this requires complex and traumatic surgical intervention – implantation of a left ventricular circulatory support device that helps the weakened myocardium to pump blood through the vessels.
Researchers at Pennsylvania State University have developed a new device that will allow some patients to avoid such operations. A tiny percutaneous heart pump Heartmat, which is 6 mm wide, is inserted into the femoral artery, along which it is moved to the left ventricle, where it maintains blood flow, giving the heart the opportunity to recover quickly. This device has recently received approval for clinical use in Europe and is currently undergoing clinical trials in the United States for approval by the U.S. Food and Drug Administration (FDA).
The head of the developers, Robert Kunz, is not related to surgery, but is a specialist in the field of aerospace engineering, which at first glance has nothing to do with biomedical developments. However, in fact, the blood pump is essentially a miniature propeller, in the development of which the authors were guided by the principles by which propellers for submarines and torpedoes are developed.
A multidisciplinary group of researchers, which includes engineers, as well as specialists in hydrodynamics, materials science and structural mechanics, began work on a prototype pump and a model of the heart, necessary to assess the productivity of sediment, back in 2004.
The pump consists of a tiny rapidly rotating screw, the blades of which have the consistency of an eraser and can be folded in such a way that they fit inside a compressible catheter, whose diameter is 3 mm. At the same time, they are so strong that they can pump more than 4 liters of blood per minute with an increase in pressure of one tenth of the atmosphere, which corresponds to the heart power of a healthy man. Kunz explains that after the pump inserted into the femoral artery enters the heart, the doctor pulls the control cable, as a result of which the pump exits the catheter, unfolds, increasing to 6 mm in diameter, and begins to rotate.
Due to its small diameter, it can rotate at a very high speed, reaching almost 20,000 revolutions per minute. This is a potential problem, since placing a rapidly rotating screw in relatively slow–flowing blood can lead to the destruction of fragile red blood cells - cells that transport oxygen and carbon dioxide through the body. This problem was solved using the "trial and error" method, and as a result, the authors managed to obtain an optimal combination of the shape of the blades and their rotation speed, ensuring the safety of red blood cells.
Gallery: propeller in the heart
A heart pump for percutaneous injection with a model of the left ventricle of the human heart.
The blades of the "propeller", painted in blue, rotate inside a mesh tube or catheter, the diameter of which narrows to 3 mm to move through the blood vessels. When the device enters the heart, the tube and blades expand and the propeller begins to rotate, ensuring the movement of blood through the system, which reduces the load on the damaged myocardium.
The new heart pump resembles a submarine propeller. Its blades are designed in such a way that when rotating at a speed of about 20,000 revolutions per minute, they do not damage red blood cells.
Chest X-ray of a patient with an implanted heart pump. The dark curved structure is the device's power cable.
The researchers believe that the final product of their work will save a huge number of people who have suffered a myocardial infarction. He will be able to temporarily take over the function of the heart muscle, giving patients the opportunity to wait for surgery or, in the most mild cases, providing the opportunity to independently restore heart function.
Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of Pennsylvania State University: In a Heartbeat.
26.09.2016