First-Ever Pig-to-Human Heart Transplant Shows 'Unexpected Differences'

Based on the most recent early studies to be proffered at the American Heart Association's Scientific Sessions 2022, heart rhythm metrics in the electrocardiograms of the first pig-to-human heart transplant showed unexpected differences in the electrical transport system of the genetically modified pig heart particularly in comparison to an unmodified pig heart. The meeting, which will be conducted in person and electronically in Chicago from November 5-7, 2022, is a major global exposition of the most recent scientific discoveries, research, and scientific proof clinical research updates in cardiovascular science.

In January 2022, the first-ever transplantation of a genetically engineered pig heart, was performed on a 57-year-old man with a fatal heart disease. The man remained alive for 61 days, as per the study published in PubMed Central.

For more than 30 years, scientists have been collaborating on this breakthrough pig-to-human transplantation procedure. Extracting hearts from genetically engineered pigs whose genes have been tweaked so that they may be safely transplanted into people could become a reality one day.

Pig-to-Human Heart Transplant Risk

Following a statement from Timm Dickfeld, M.D., Ph.D., in a Study Finds report, he pointed out that there are various possible hurdles to transplanting a pig heart into a person. With any transplant, such as this one, there always exist the danger of rejection, the risk of infection, and the third risk is irregular heart rhythms, which is where the electrocardiogram (ECG) comes in, as added by the professor of medicine and director of electrophysiology research at the University of Maryland School of Medicine in Baltimore. The reality that the ECG characteristics of the pig heart following transplantation into a human has been so different from the usually discovered Rating scales for native pig hearts is certainly a remarkable result.

Assessing the heart using an ECG after transplantation is one method of assessing the electrical transport process based on a heart transplant. A 12-lead ECG analyzes electrical conduction at 12 distinct electrical orientations of the heart.

The scientists focused on two ECG measurements in particular: the PR interval/QRS complex and the QT interval. The PR interval and QRS complex quantify the time it necessitates for electricity to move from either the top to the bottom chamber and then across the bottom chambers, therefore pumping blood through the heart.

The QT interval refers to how long it takes the bottom of the heart's chambers to complete a whole electrical cycle linked with a heartbeat. The ECG data of the transplanted individual were gathered once a day following the transplant for this investigation. A prior study found that ECG characteristics of the pig heart in a pig body used to have a brief PR interval (50 to 120 milliseconds), a quick QRS (70 up to 90 milliseconds), and a little short of QT (260 up to 380 milliseconds).

In comparison, the first-ever ECG of a genetically engineered heart xenotransplant observed a larger PR interval of 190 milliseconds, QRS length of 138 milliseconds, and QT of 538 milliseconds, which would be longer than what would be predicted from a pig heart in a pig body, as added by Dickfeld.

The Pig's Heart Capabilities

Dickfield also explained that in a human heart, when those characteristics lengthen, this might signal indicators of electrical or myocardial illness. The pig heart ECG parameters were expanded to what we see in a human heart, and often the measurements went beyond what we consider typical in a human heart. Furthermore, the continuous ECG measurements show that the longer PR intervals remained consistent following the transplant, averaging around 210 milliseconds. QRS length remained protracted at around 145 milliseconds, however, this was reduced later in the 61-day post-transplant time frame.

The QRS length may extend when, for instance, the muscular and the electrical system itself are unhealthy, and this is why electricity takes a long time to go from cell to cell and from one part of the heart to the other, as Dickfeld continued. In general, it would prefer that this QRS measurement not be overly prolonged. Finally, the study discovered an enhanced QT length average of around 509 milliseconds exhibiting dynamic fluctuations. The shortest QT duration was recorded on day 14. In the human heart, QT length is linked to a greater likelihood of irregular cardiac rhythms, Dickfeld added.

These findings, according to the researchers, provide the groundwork for future studies to better understand the consequences of xenotransplantation on the heart's electrical system and to better prepare for forthcoming xenotransplant cases.

According to the American Heart Association's 2022 Heart Disease and Stroke Statistical Update, the United States had the highest number of heart transplants in 2020 (the most current statistics available), with 3,658 transplants completed. According to the report, 3,515 people were on the waiting list for a heart transplant as of February 2021, while 49 patients were on the waiting list for a heart and lung transplant.

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