Cardiorespiratory fitness and left ventricular recovery after kidney transplantation: evidence, gaps, and future directions

BACKGROUND: Despite improved survival following kidney transplantation, cardiovascular disease (CVD) remains a leading cause of mortality in kidney transplant recipients (KTRs). This risk is driven by complex traditional and nontraditional mechanisms contributing to uremic cardiomyopathy. Cardiorespiratory fitness (CRF) is consistently reduced in KTRs and strongly associated with cardiovascular outcomes. However, while cardiac structure and function may partially improve post-transplant, recovery of CRF often remains incomplete compared to healthy individuals, suggesting that structural reverse remodeling does not necessarily equate to restored cardiovascular reserve. METHODS: This review synthesises current evidence on post-transplant changes in left ventricular structure and function and trajectories of CRF recovery. We highlight persistent discrepancies between echocardiography-based and cardiac magnetic resonance (CMR)-based findings, together with the limited use of cardiopulmonary exercise testing (CPET) in longitudinal studies. KEY FINDINGS: We discuss the concept of a 'transplant cardio-recovery gap', reflecting the dissociation between structural normalisation and functional capacity restoration. FUTURE DIRECTIONS: We outline future directions for research including phenotype-specific monitoring using CMR-derived strain, native T1 mapping, and CPET parameters, integrated through AI-enabled predictive analytics, to enable digital twin models capable of forecasting individualised recovery trajectories. We discuss CMR-CRF coupling models, and adaptive rehabilitation trials stratified by functional cardiovascular reserve rather than structural metrics alone. CONCLUSION: While kidney transplantation offers partial cardiovascular recovery, restoration of cardiopulmonary resilience remains an unmet therapeutic target. Precision, AI-guided CRF evaluation and rehabilitation may redefine cardiovascular risk management in KTRs and inform the next generation of transplant optimisation strategies.