Abstract 4370155: Comparison of baseline EKG parameters between the first and second Heart xenotransplant

Background: The 1 st and 2 nd genetically modified porcine-to-human cardiac xenotransplantations were performed at the University of Maryland in January 2022 and September 2023, respectively. The recipients survived for 60 and 41 days, respectively. Methods: Daily 12-lead EKGs were obtained during the postoperative days (POD). Standard baseline parameters were analyzed from non-paced EKGs. Results: The average heart rate (HR) was similar between the 1 st and 2 nd xenotransplant with a HR difference of 1.9±3.0 (75.0±10.0bpm vs 73.1±16.7bpm, P=0.13) with no significant differences in HR over POD 1-20 (79.0±12.0bpm vs 78.15±8.5bpm, P=0.33) or POD 21-40 (70.0±7.0bpm vs 69.9±19.8bpm, P=0.34; Figure 1A). The average PR interval was significantly longer in the 1 st xenotransplant compared to the 2 nd, with a difference of 55.2±6.2ms (212.0±20.0ms vs 156.8±32.5ms, P<0.001). This was consistent during POD 1-20 (200.0±15.0ms vs 145.0±28.4.0ms, P<0.001) and POD 21-40 (228.0±18.0ms vs 171.7±32.0ms, P<0.001; Figure 1B). QRS width (ventricular depolarization) was significantly longer in the 1 st xenotransplant compared to the 2 nd, with a difference of 64.6±3.6ms (145.0±16.0ms vs 80.4±17.7ms, P<0.001). This was seen during POD 1-20 (154.0±19.0ms vs 82.5±15.5ms, P<0.001) as well as POD 21-40 (151.0±14.0ms vs 78.6±20.4, P<0.001; Figure 1C). Similarly, the QT interval (ventricular repolarization) was significantly longer in the 1 st xenotransplant compared to the 2 nd, with a difference of 132.1±9.7 (509.0±51.0ms vs 376.9±42.4ms, P<0.001). The longer QT interval was seen during POD 1-20 (504.0±57.0ms vs 377.75±43.0ms, P<0.001) and POD 21-40 (502.0±56.0ms vs 373.1±42.8ms, P<0.001; Figure 1D). Accordingly, the QTc interval was longer in the 1 st xenotransplant with a difference of 158.2 ± 11.7ms (568.0±55.0ms vs 409.8±55.6ms, P<0.001), which was consistent during POD 1- 20 (591.0±52.0ms vs 429.8±53.0ms, P<0.001) and POD 21-40 (141.5±16.2 (535.0±51.0ms vs 393.4±45.9ms, P<0.001; Figure 1E). Conclusion: Significant differences in AV nodal conduction, ventricular depolarization and repolarization timings were seen between the 1 st and 2 nd xenotransplanted patient with the latter more closely approximating the average ECG intervals seen in porcine hearts. Further studies are needed to better characterize those disparities and elucidate the role of denervation, immunosuppressive regimens, and inter-species molecule/receptor interactions.