Association between arterial stiffness and heart rate variability in heart transplant recipients

Abstract Introduction Heart transplantation (HT) is the gold standard treatment for refractory heart failure, offering a life-saving intervention for patients with end-stage cardiac dysfunction. However, this procedure is associated with significant haemodynamic alterations, which may impact both vascular function and autonomic regulation. Arterial stiffness, represented by the augmentation index (AI), and heart rate variability (HRV) are well-established cardiovascular risk markers in HT recipients. However, the interaction between these two parameters remains poorly understood, particularly considering that post-transplant duration may modulate both indices. Objective To investigate the relationship between arterial stiffness and HRV in heart transplant recipients, with the aim of elucidating potential interactions between vascular function and autonomic cardiac modulation. Methods This cross-sectional study was conducted between August 2018 and December 2023. Participants were 18–65 years old, of both sexes, had undergone HT at least six months prior, were clinically stable, and were on regular immunosuppressive therapy. Arterial stiffness was assessed via the augmentation index (AI), while HRV was evaluated using frequency-domain components. These parameters were measured through pulse wave amplitude variation using peripheral arterial tonometry. Results A total of 33 participants were included, with a mean age of 48.85 ± 12.29 years, 82% male, and a mean post-transplant duration of 34.39 ± 25.43 months. The recorded values were as follows: Augmentation Index (AI): -3.95 ± 13.71 (%); Low-frequency to high-frequency ratio (LF/HF): 0.66 ± 0.73 ms²; Low-frequency (LF): 76.35 ± 58.81 ms²; High-frequency (HF): 161.02 ± 75.46 ms². A positive correlation was observed between AI and HF (r = 0.434, p = 0.012) and between AI and the LF/HF ratio (r = 0.579, p 0.001), suggesting a direct association between arterial stiffness and parasympathetic autonomic modulation. However, no significant correlation was found with LF. Conclusion These findings indicate that greater arterial stiffness is associated with increased parasympathetic autonomic modulation, as evidenced by the positive correlation between AI and HF. Furthermore, the correlation between AI and the LF/HF ratio suggests a potential autonomic imbalance linked to vascular function in heart transplant recipients. The lack of correlation with LF underscores the need for further investigation to elucidate the underlying mechanisms governing these associations and their prognostic implications for post-transplant follow-up.