Multimodal Cardiac Imaging of Immune‐Mediated Complications Post Heart Transplantation: A Contemporary Review

Heart transplantation significantly enhances survival and quality of life for patients with end-stage heart failure. Despite advances in surgical and postoperative care, immune-mediated complications, acute graft rejection and cardiac allograft vasculopathy (CAV), remain major barriers to long-term success. Acute rejection predominantly affects early posttransplant survival, whereas CAV becomes a leading cause of mortality in later years. The gold standards for diagnosis, endomyocardial biopsy for rejection and coronary angiography for CAV, are invasive and imperfect. Noninvasive multimodality imaging is increasingly used to complement or, in selected scenarios, defer invasive testing. Echocardiography with strain detects early myocardial dysfunction when ejection fraction is preserved; stress echocardiography provides prognostic information for CAV. Quantitative techniques, positron emission tomography myocardial blood flow/myocardial flow reserve and quantitative cardiac magnetic resonance perfusion, improve detection of diffuse, stage-dependent CAV compared with qualitative assessments. Cardiac magnetic resonance tissue mapping characterizes edema and fibrosis relevant to rejection surveillance; fluorodeoxyglucose-positron emission tomography for inflammation is emerging but remains investigational in most centers. Cardiac computed tomography angiography defines coronary anatomy and plaque with excellent negative predictive value and offers physiologic assessment with computed tomography-myocardial perfusion imaging/computed tomography-derived fractional flow reserve; it is best used strategically rather than as an annually repeated test. This contemporary review synthesizes the strengths, limitations, and practical roles of echocardiography, nuclear imaging, cardiac magnetic resonance, and cardiac computed tomography angiography across adult and pediatric populations; highlights areas where quantitative methods add incremental value; and provides pragmatic, stage-aware surveillance frameworks. Integrating modalities can reduce reliance on invasive procedures, lower procedural risk, and refine therapeutic decision-making benefits that are particularly relevant for children and other patients for whom repeated invasive testing is undesirable.