The French artificial heart

Cardiology – one of the fastest developing specializations, again takes a major step forward. After percutaneous interventions of stenting, valve replacements, atrial septal defect occlusion, atrial appendage occlusion, time has come for even greater interference in human heart’s structure. Now the scientists get closer to the total replacement of insufficient ventricles with artificial heart. Although, the mankind has dreamt of placing a machine inside the chest for generations, the mechanism of similar size, weight, and functioning as a human heart has not been created until now. The task has been accomplished by a French research group that developed a prototype named CARMAT. This artificial heart model has been recently launched into the first phase of clinical testing and this year it is to be implanted into several patients.

In Western Europe ca. 12 million people suffer from heart failure, 0,5-5% of whom are in advanced stage and resistant to pharmacological treatment. Those patients’ only hope is heart transplantation. However, due to an insufficient number of donors, only 3200-3400 procedures are performed yearly. For transplantation-awaiting or–disqualified patients, ventricular assist devices (VADs), both left- and biventricular are have been used since 1994. Currently used devices are powered externally (electrically or pneumatically) and contain a rotor which assures perpetual blood flow. Pneumatic mechanism is an element of currently applied artificial hearts, which substitute both ventricles.

Research on artificial heart dates back to 1949, when for the first time ever Sewell and Glenn implanted an artificial heart in a dog’s body. First transplants performed on human beings took place in 1966 (left-ventricular assist device) and 1969 (total artificial heart). TAH was implanted in the transplantation waiting period of 64 hours. First successful heart substitution took place in 1982. Patient lived for another 112 days with Jarvik-7 implant. At present, FDA accredited artificial hearts are CardioWest (in use since 2004, implanted in 900 patients) and AbioCor (in use since 2006, implanted in 14 patients).

Short living expectancy of patients with artificial heart is a result of serious infections due to the presence of foreign materials in the body, haemorrhagic and thromboembolic complications. Furthermore, large size of the prosthesis, external power source and low adaptability to unstable human body requirements significantly limit patients easiness.

The latest achievement is CARMAT TAH. This artificial heart is the outcome of cooperation between professor Alain Carpentier and Jean-Luc Lagardère. Between 1995 and 2003, 3 prototypes of CARMAT heart were created. Gradually, prostheses were designed smaller, lighter and more energy efficient. The final version released at the end of 2010 weighs 900 grams, has 750 milliliter capacity and 27 watt energy consumption. This heart consists of 2 ventricles each made of 2 compartments – one filled with blood, other with silicone liquid. These compartments are separated by a membrane, which allows pulsating movements. Electro-hydraulic pumps force the silicone liquid in and out which in turn puts the membrane into a rhythmic bulging imitating systoles. Cardiac output ranges from 30 to 65 ml and the heart rate from 35 to 150 beats per minute. These variables change automatically as a response to signals from baroreceptors that are implemented in the prosthesis in order to detect preloads. As a result, the blood flow may vary between 2 to 9 ml/min depending on organism’s needs. A percutaneous driveline is used for power delivery as well as communication.

Another advantage of CARMAT TAH are materials used for its manufacture. Alain Carpentier is known as a creator of up-to-date haemocompatiblemitral and aortal valves Carpentier-Edwards PERIMOUNT. They were first introduced to clinical use over 20 years ago. Their innovative material is based on employing glutaraldehyde-processed and expanded polytetrafluorethylene (ePTFE) bovine pericardial tissue. These materials have been researched for their performance and recently published results [1] prove high similarity to heparin-coated surfaces as far as thrombogenic properties are concerned. All valves and ventricle surfaces that stay in contact with blood are lined with ePTEE and bovine pericardial tissue. This may possibly allow for a reduction in anticoagulation treatment after prosthesis implantation. The creators hope for significant decrease in haemorrhagic as well as thromboembolic complications.

CARMAT TAH testing has reached a next phase. This year the French artificial heart is to be implanted in 4, 5 or even 6 patients. Further extension of clinical research is planned for 2013. In race for priority in creating the first totally artificial heart we also find an American team with their prototype 2005 MagScrew TAH and the Foundation for the Development of Cardio-surgery from Zabrze with Polish Artificial Heart POLTAH. It seams that only one step separates us from the milestone and the only unknown is which heart will reach the goal first by beating in patient’s chest.

Written by: Agata Durdzińska

Source:
1. Jansen P., van Oeveren W., Capel A., Carpentier A.: In vitro haemocopatibility of a novel bioprosthetic total artificial heart. Eur J Cardiothorac Surg. 2012 Apr 4. [Epub ahead of print]
2. Braly J.-P.: Le coeurartificiel: l’exploittechnologiqued’une start-up française. La Recherche, 2012 Janv, No 459, s. 38-45
3. Choroby wewnętrzne. Przyczyny, rozpoznanie i leczenie. Andrzej Szczeklik (red.). T. I. Kraków: Wydawnictwo Medycyna Praktyczna, 2005, s. 331. ISBN 8374300310. 
4.http://carmatsa.com/index.php?option=com_phocagallery&view=category&id=4&Itemid=54&lang=fr
5. http://en.wikipedia.org/wiki/Artificial_heart

Want to know more about heart? Watch on medtube.net “Normal Cardiac Anatomy and Physiology”

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