The waiting time for a donor heart is long, often too long for patients with severe heart disease who urgently need the new organ: on average, it is six months for patients who are classified as the most urgent. In order to bridge the waiting time until the life-saving transplant, the team at the Department of Cardiac Surgery at Heidelberg University Hospital (UKHD) has provided two patients with the most modern artificial hearts currently available (Carmat Aeson). The hydraulic pump, slightly larger than a natural heart, is inserted into the chest as in a heart transplant and sutured to the large blood vessels and atria, after which the chest is closed again. Only the cable for the power supply protrudes. It connects the artificial heart to the batteries, which the patients always carry with them in a shoulder bag that can be converted into a rucksack. The two highly complex operations, which took place in quick succession in June and July 2024, were a first for the heart surgeons in Heidelberg and went extremely well: Both patients are currently recovering well from the surgery and the physical consequences of their serious heart condition.
The ‘Carmat Aeson’ is approved as a fully implantable replacement system for complete cardiac function in Germany. Fully implantable support systems for the left ventricle, which bypass the left side of the heart like a bypass, have been available for some time, but not for the right side of the heart. In the support systems available for the right ventricle and the entire heart, the blood pump is located outside the body. ‘These systems have a pneumatic drive and are very loud. In addition, the patients pull the drive behind them on a caddy. This was one of the reasons why our patients opted for the Carmat Aeson,’ says Professor Dr Anna Meyer, Senior Consultant and Head of the Cardiac Support Programme at the Department of Cardiac Surgery at the UKHD, who was responsible for both procedures. Both patients' entire hearts were severely damaged and they were therefore on the waiting list for a donor heart. When their condition deteriorated further, a quick solution had to be found.
Hydraulic pump with biomembrane and bovine heart valves generates a pulsating blood flow
Lifesaver is a high-tech hydraulic pump that generates a pulsating blood flow just like a real heart. Built-in sensors detect the blood pressure and automatically adjust the pumping capacity. Heart valves and an inner lining made of bovine heart tissue prevent the formation of clots. Patients will therefore not need strong anticoagulants. However, patients are now dependent on a power source until a donor heart is transplanted: The batteries supply the heart robot with energy for six to seven hours, after which they have to be replaced. At night, the system is connected to the mains using a mains plug. And in the event of a prolonged power cut? Then you need to quickly find a clinic with an emergency power supply.
Implantation of an artificial heart challenges surgeons and technicians alike
In the early days of the new artificial heart, which was developed in Paris in 2013, there were isolated cases of pump failure, prompting Carmat to completely revise and extensively test the system. The revised version, which has also been approved for Germany, has been on the market since the end of 2022. The study results convinced the team from Heidelberg and in March 2023, a ten-strong interdisciplinary multi-professional team from the UKHD, consisting of four cardiac surgeons, an anaesthetist, a cardiotechnician, a cardiologist, an intensive care nurse and two artificial heart coordinators, received training from the manufacturer in Paris. Not only is the implantation surgically highly demanding, the artificial heart must be connected absolutely tightly to the natural vessels, the system also needs to be started correctly, the displays on the control console analysed and the effects of the artificial heartbeat on the rest of the organism considered.
‘We were naturally tense during the operation more than a year later,’ recalls Professor Meyer. A team from the manufacturer travelled to the site to provide support. Everyone was very satisfied with the result of the operation, which lasted several hours: there were no complications or post-operative haemorrhaging, the two men, aged 51 and 58, were able to breathe independently again from the following day and were transferred to the normal ward after a certain follow-up period. Such a rapid recovery and mobilisation is rather unusual for these seriously ill patients. The first patient has already started his follow-up treatment in a rehabilitation clinic. It is particularly pleasing that the damage to the liver and kidneys caused by the lack of blood flow due to the massive heart failure is gradually receding. ‘It is fascinating to observe how the body is gradually recovering and resuming its work, especially in our second patient, whose liver, kidneys and intestines were barely functioning. I am optimistic that we will soon be able to reduce the support of organ functions such as dialysis,’ says Anna Meyer.
What does an artificial heart feel like?
What does it feel like to have an artificial heart beating in your chest? ‘I don't notice that the heart feels any different. I just had to get used to the sound and didn't sleep the first few nights,’ says the patient, whose heart was so badly damaged by an autoimmune disease that it was only able to produce 15 per cent of its normal cardiac output. He had therefore been fitted with a pacemaker and implantable defibrillator for several years. When his cardiac output suddenly deteriorated rapidly, he was connected to a device at the clinic that oxygenated his blood outside the body. He was confined to bed for more than four weeks. A few days ago, he was able to walk to the cafeteria again with the help of a walking frame. ‘I feel much better now. I wouldn't have been able to go on like before,’ says the 58-year-old.
At the UKHD's Department of Cardiac Surgery, the team led by Medical Director Professor Dr Matthias Karck performs more than 1,600 major heart operations every year. In 2023, 22 donor hearts were transplanted and 135 patients were treated with mechanical heart support systems. Across Europe, 30 people are living with Carmat artificial hearts, some of them for more than six months. Eleven other patients who have been treated with the Aeson in the meantime have now received a donor heart. Whether more of these artificial hearts will be transplanted in future to bridge the waiting period depends on how the health of the two men develops. The heart surgeons are optimistic.
Source: press release Heidelberg University Hospital (in German only)
More on the history of the artifical heart: Hintergrund: Die Geschichte des Kunstherzens (Heidelberg University Hospital, in German only)
