Prognostic Value of Early Cardiac Magnetic Resonance First-pass Perfusion Assessment of Microcirculatory Dysfunction for Acute Rejection After Heart Transplantation

Background: Acute rejection (AR) remains a major obstacle to success after heart transplantation (HT). Impaired microcirculatory function is linked to a higher risk of AR. The value of cardiac magnetic resonance (CMR) resting first‑pass perfusion imaging for evaluating microcirculatory function to predict subsequent AR after HT remains unclear. We aimed to evaluate the prognostic value of CMR resting first‑pass perfusion parameters measured early after HT for AR.

Methods: This single center retrospective study analyzed data from 79 HT recipients, including 21 with AR (HT [AR+]) and 58 without AR (HT [AR-]), and 32 healthy volunteers. CMR examination was performed at 3 months after HT to assess myocardial perfusion. Resting first-pass perfusion parameters, including time to peak myocardial signal intensity (TTM), Upslope, and maximum signal intensity (MaxSI) were analyzed. Univariable and multivariable Cox regression analyses were performed to identify predictors of AR within 2 years after HT. Incremental prognostic value was evaluated using C-index, continuous net reclassification index (NRI), and integrated discrim- ination improvement (IDI). P value < 0.05 was considered statistically significant.

Results: During a median follow‑up of 24 months, 21 HT recipients (26.6%) experienced AR. Patients with AR showed significantly longer TTM, lower Upslope and MaxSI at 3 months after HT compared with non‑AR patients and controls (all P < 0.001). TTM (aHR: 1.07 [1.04, 1.10], P < 0.001), Upslope (aHR: 0.78 [0.71, 0.86], P < 0.001), and MaxSI (aHR: 0.97 [0.95, 0.98], P < 0.001) were independent predictors of AR after adjusting for age and body mass index (BMI). Adding TTM, Upslope, and MaxSI individually to the clinical model (age + BMI) significantly improved discriminant and reclassification ability for risk of AR (C‑index: 0.803, 0.889, 0.869 vs. 0.707; continuous NRI: 0.755, 1.049, 1.025; IDI: 0.139, 0.343, 0.340; all P < 0.05), with Upslope demonstrating the highest incremental value.

Conclusions: CMR resting first‑pass perfusion parameters acquired early after HT that reflect microcirculatory dysfunction are independent prognostic markers AR within 2 years and provide incremental prognostic value over clinical variables to guide personalized post‑transplant management.