Intravascular ultrasound-guided selection for early noninvasive cardiac allograft vasculopathy screening in heart transplant recipients

Transplant Vasculopathy Versus Native Atherosclerosis: Similarities and Differences

Cardiac allograft vasculopathy (CAV) is one of the leading causes of graft failure and death after heart transplantation. Alloimmune-dependent and -independent factors trigger the pathogenesis of CAV through activation of the recipients' (and to a lesser extent donor-derived) immune system. Early diagnosis of CAV is complicated by the lack of clinical symptoms for ischemia in the denervated heart, by the impact of early functional coronary alterations, by the insensitivity of coronary angiography, and by the involvement of small intramyocardial vessels. CAV in general is a panarterial disease confined to the allograft and characterized by diffuse concentric longitudinal intimal hyperplasia in the epicardial coronary arteries and concentric medial disease in the microvasculature. Plaque composition in CAV may include early fibrous and fibrofatty tissue and late atheromatous calcification. In contrast, native coronary atherosclerosis usually develops over decades, is focal, noncircumferential, and typically diminishes proximal parts of the epicardial vessels. The rapid and early development of CAV has an adverse prognostic impact, and current prevention and treatment strategies are of limited efficacy compared with established strategies in native atherosclerosis. Following acute coronary syndromes, patients after heart transplantation were more likely to have accompanying cardiogenic shock and higher mortality compared with acute coronary syndromes patients with native hearts.

Role of Radiology in Assessment of Postoperative Complications of Heart Transplantation

Heart transplantation is a pivotal treatment of end-stage heart failure, and recent advancements have extended median posttransplant life expectancy. However, despite the progress in surgical techniques and medical treatment, heart transplant patients still face complications such as rejection, infections, and drug toxicity. CT is a reliable tool for detecting most of these complications, whereas MR imaging is particularly adept at identifying pericardial pathologies and signs of rejection. Awareness of these nuances by radiologists, cardiologists, and surgeons is desired to optimize care, reduce morbidities, and enhance survival.

Paediatric heart transplantation recipients ≥7 years of age receiving donors with pre-existing coronary atherosclerosis showed progressive coronary artery disease

BACKGROUND

This study aimed to determine the effect of donor-transmitted atherosclerosis on the late aggravation of cardiac allograft vasculopathy in paediatric heart recipients aged ≥7 years.

METHODS

In total, 48 patients were included and 23 had donor-transmitted atherosclerosis (baseline maximal intimal thickness of >0.5 mm on intravascular ultrasonography). Logistic regression analyses were performed to identify risk factors for donor-transmitted atherosclerosis. Rates of survival free from the late aggravation of cardiac allograft vasculopathy (new or worsening cardiac allograft vasculopathy on following angiograms, starting 1 year after transplantation) in each patient group were estimated using the Kaplan-Meier method and compared using the log-rank test. The effect of the results of intravascular ultrasonography at 1 year after transplantation on the late aggravation of cardiac allograft vasculopathy, correcting for possible covariates including donor-transmitted atherosclerosis, was examined using the Cox proportional hazards model.

RESULTS

The mean follow-up duration after transplantation was 5.97 ± 3.58 years. The log-rank test showed that patients with donor-transmitted atherosclerosis had worse survival outcomes than those without (p = 0.008). Per the multivariate model considering the difference of maximal intimal thickness between baseline and 1 year following transplantation (hazard ratio, 22.985; 95% confidence interval, 1.948-271.250; p = 0.013), donor-transmitted atherosclerosis was a significant covariate (hazard ratio, 4.013; 95% confidence interval, 1.047-15.376; p = 0.043).

CONCLUSION

Paediatric heart transplantation recipients with donor-transmitted atherosclerosis aged ≥7 years had worse late cardiac allograft vasculopathy aggravation-free survival outcomes.

Non-Invasive Imaging in the Evaluation of Cardiac Allograft Vasculopathy in Heart Transplantation: A Systematic Review

Cardiac allograft vasculopathy (CAV) is the leading cause of long-term graft dysfunction in patients with heart transplantation and is linked with significant morbidity and mortality. Currently, the gold standard for diagnosing CAV is coronary imaging with intravascular ultrasound (IVUS) during traditional invasive coronary angiography (ICA). Invasive imaging, however, carries increased procedural risk and expense to patients in addition to requiring an experienced interventionalist. With the improvements in non-invasive cardiac imaging modalities such as transthoracic echocardiography (TTE), computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET), an alternative non-invasive imaging approach for the early detection of CAV may be feasible. In this systematic review, we explored the literature to investigate the utility of non-invasive imaging in diagnosis of CAV in >3000 patients across 49 studies. We also discuss the strengths and weaknesses for each imaging modality. Overall, all four imaging modalities show good to excellent accuracy for identifying CAV with significant variations across studies. Majority of the studies compared non-invasive imaging with ICA without intravascular imaging. In summary, non-invasive imaging modalities offer an alternative approach to invasive coronary imaging for CAV. Future studies should investigate longitudinal non-invasive protocols in low-risk patients after heart transplantation.

Cardiac Allograft Injuries: A Review of Approaches to a Common Dilemma, With Emphasis on Emerging Techniques

Clinical features of allograft injury are often unreliable, and context within the transplant journey is key. In the setting of post-transplant allograft dysfunction, the choice of initial investigation depends on clinical assessment and history. One of the major considerations is the time post transplantation in helping to decide a likely cause for allograft injury. Immediately post transplantation, it is important to consider donor factors (including donor demographics as well as immunological match), ischaemic times, surgical issues as well as early rejection. Clinical suspicion needs to remain high with variable presentations, including haemodynamic instability, arrhythmia, as well as left ventricular dysfunction. Symptoms of allograft dysfunction may include dyspnoea, exertional intolerance, dizziness / lightheadedness, palpitations, as well as right or left heart failure. In the coming weeks and months, endomyocardial biopsy and blood-based biomarkers may be helpful including high sensitivity troponin and donor-derived cell-free DNA. Molecular markers for rejection are hopeful, and may also be useful in non-ischaemic causes of allograft dysfunction. Screening remains important late post heart transplant due to variety of signs associated with rejection (early) and lack of typical anginal symptoms (later). New imaging modalities - especially cardiac magnetic resonance imaging, have been shown to be useful for assessing cause of allograft dysfunction including ischemia, infarction and rejection.