Pig-to-human heart transplant: unexpected conduction characteristics

By Dr. Jonathan Shurlock

Xenotransplantation of a pig heart into a 57-year-old man with end stage heart failure made headlines globally earlier in the year, with the patient living for 61 days post-transplantation. Data from this prominent case is to be presented at the American Heart Association Scientific Sessions on November 5th-7th, focussing on the electrical conduction characteristics of the implanted heart.

The author group describes how the usual ECG measures and intervals in pig hearts are generally shorter than those seen in humans, but that these were prolonged in ECGs performed on the pig heart implanted in the above case. The authors focussed on the difference in the PR interval, QRS complex and QT interval, with once daily ECGs performed post-transplantation.

Previous data show pig hearts have shorter PR intervals (50 to 120 milliseconds), shorter QRS durations (70 to 90 milliseconds) and short QT intervals (260 to 380 milliseconds). In this study the authors found “a longer PR interval of 190 milliseconds, QRS duration of 138 milliseconds and QT of 538 milliseconds” from the implanted heart. They further found that PR prolongation remained constant, while QRS duration steadily reduced over the 61 day follow up period. Interestingly while the QT interval remained prolonged throughout follow up, there was high fluctuation in length, with an average of 509 milliseconds.

While clinicians not involved in the work have commented on the relevance of these findings, with regards to risk of arrhythmia post-xenotransplantation, more analysis is likely forthcoming following presentation at the AHA scientific sessions November 5th-7th.

The described findings are significant as clinicians and researchers continue to search for innovative ways to provide life-saving intervention to individuals on transplant lists.

Further information via press release can be found here: https://newsroom.heart.org/news/modified-pig-to-human-heart-transplant-had-unexpected-changes-in-heart-s-conduction-system