February 4, 2022 Author : Rui Campante Teles Cardiovascular diseases are the leading cause of death today. Heart failure - that is, the inability of the heart to pump enough blood to meet the body needs - has different possible therapies . Among these are, for example, drugs and heart valves minimally invasive procedures performed through catheterization. These were, in fact, the great revolution for patients and cardiologists in the last two decades. However, at some point many patients enter at the so-called stage of terminal heart failure . In these cases, the only solution is a heart transplant . These patients are temporarily connected to a device called ventricular assist device (VAD) . Through cannulas – as ECMO (extracorporeal membrane oxygenation), which has been much talked about related to use in some patients COVID-19 – or through a surgical connection (as in the Berlin Heart), the VAD performs the pump functions and allows keeping patients alive until they receive a transplant or until they place a long-term VAD device such as the HeartMate as their final destination, which is complex and limited by complications such infections, bleeding and associated thrombosis. The problem is that there is a lack of hearts for transplantation . The current reality, in the US and across Europe, is that many patients die on the waiting list – and that is why alternative solutions such as the one recently announced by the University Maryland Heart Center have been investigated for many years. The case of David Bennett On January 10, 2022, the University Maryland Heart Center announced that it had carried out, for the first time in the world, the transplant of a heart from a genetically manipulated pig to a 57-year-old heart failure patient, who since November 2021 had been connected to a VAD that performed the functions of his heart. He could not be given a mechanical heart pump because he had an irregular heartbeat. Nor was he eligible to receive a human heart transplant because he had a history of failing to comply with medical orientations. This patient therefore decided to enter the compassionate experience of being transplanted with a genetically manipulated pig heart. And it was because of his voluntarism that the doctors had the approval by the US regulator, the FDA, which until then had insisted on the experiment with baboons. The heart transplanted on January 7 was from a pig genetically modified before the transplant, so that the organ would not be rejected after transplantation . In particular, three genes responsible for producing antibodies that could cause rejection were removed and six human genes were implanted to help the patient body accept the organ and ensure that the heart would maintain the proper size. The information about the procedure was given nine days after it was performed, when the patient had already passed the most critical phase. Why was the pig chosen? The pig heart has an anatomy close to that of humans . In addition, it has a quick growth and can be used in different age groups and weights. In 2021, other medical teams had transplanted genetically modified pig kidneys into two brain-dead patients: the organs worked and there was no rejection. This type of experiment has made great progress thanks to the development of a new genome editing tool (CRISPR–Cas9) that has facilitated the creation of pigs with organs that are less likely to be attacked by the human immune system. Why are these experiences important? This pioneering intervention by the University Maryland Heart Center was the first in which an organ from a pig was transplanted into a human with chance of survival. Innovations like this could, in fact, come to fill the serious shortages of human hearts for transplantation . The main problem in a transplant is the possibility that the recipient organism will reject the new organ . Previously, there have been experiments in transplanting hearts from pigs to humans, but the organs have not been genetically modified, and survival has not even reached one month. In this transplant performed by the University Maryland Heart Center team, at least that goal is expected to be achieved. When can this technique be commonly used? Normally, it takes five to 10 years between the first experiences and the applicability of the tested solutions. For example, the heart valve replacement by catheterization was launched in 2002 in patients with heart failure and saves thousands of lives. Since 2012, the heart valve replacement by catheterization is a routine technique at Hospital da Luz, where the first national procedure outside the Serviço Nacional de Saúde (SNS) was performed. Meet the cardiology clinical team from Hospital da Luz network. The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item.
