Detection and Imaging of Cardiac Allograft Vasculopathy

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.

Ten-year outcomes post percutaneous coronary intervention in cardiac transplant recipients

BACKGROUND

Cardiac allograft vasculopathy (CAV) is one of the major late causes of mortality in cardiac transplant recipients beyond the first year. Given the lack of longer term data for PCI in cardiac transplant recipients, we report ten year follow up of such cardiac transplant recipients who underwent PCI at Mayo Clinic.

METHODS

A retrospective observational study was conducted that included cardiac transplant recipients who underwent PCI at the Mayo Clinic. Continuous variables were presented as mean (SD) or median (IQR) and discrete variables were presented as frequency (percentage).

RESULTS

Thirty-eight consecutive cardiac transplant recipients underwent PCI from January 1, 1995, to June 30, 2023, at the Mayo Clinic. The median age of the cohort was 61.00 years (IQR:51.00-70.00) comprised predominantly of men (65.80%), and 47.40% of the cohort presented with an acute coronary syndrome. The antirejection therapy prior to the PCI included steroids (47.30%), cyclosporine (26.30%), tacrolimus (15.80%), mycophenolate (42.10%), azathioprine (13.10%), & sirolimus (31.57%). Intravascular ultrasound during PCI was utilized in 10.50% of the cases. The median time duration between heart transplant and PCI was 9.00 years (IQR:6.00-13.00 years). Two individuals needed repeat heart transplant for severe CAV. In hospital mortality was 5.20% and the long-term median survival was 7.20 years with a 10-year mortality rate of 65.70%.

CONCLUSIONS

This is the first publication reporting ten-year outcomes for PCI in cardiac transplant patients. The salient features for our cohort were a 65.70% mortality rate at 10 years and a median survival of 7.20 years.

Cardiac magnetic resonance haemodynamics in paediatric heart transplant patients: fick oximetry versus cardiac magnetic resonance phase contrast

BACKGROUND

Lifetime radiation exposure for paediatric orthotopic heart transplant (OHT) patients is significant with cardiac catheterisation as the dominant source. Interventional cardiac magnetic resonance is utilised to obtain simultaneous, radiation-free haemodynamics and flow/function measurements. We sought to compare invasive haemodynamic measurements and radiation exposure in traditional cardiac catheterisation, to comprehensive interventional cardiac magnetic resonance.

METHODS

Twenty-eight OHT patients who underwent 67 interventional cardiac magnetic resonance procedures at Children's National Hospital were identified. Both invasive oximetry with peripheral oxygen saturation (Fick) and cardiac magnetic resonance phase contrast measurements of pulmonary and systemic blood flow were performed. Systemic and pulmonary blood flow from the two modalities was compared using Bland-Altman, concordance analysis, and inter-reader correlation. A mixed model was implemented to account for confounding variables and repeat encounters. Radiation dosage data were collected for a contemporaneous cohort of orthotopic heart transplant patients undergoing standard, X-ray-guided catheterisation.

RESULTS

Simultaneous cardiac magnetic resonance and Fick have poor agreement in our study based on Lin's correlation coefficient of 0.68 and 0.73 for pulmonary and systemic blood flow, respectively. Bland-Altman analysis demonstrated a consistent over estimation of cardiac magnetic resonance cardiac output by Fick. The average indexed dose area product for patients undergoing haemodynamics with endomyocardial biopsy was 0.73 (SD ±0.6) Gy*m2/kg. With coronary angiography added, the indexed dose area product was 14.6 (SD ± 7.8) Gy*m2/kg.

CONCLUSIONS

Cardiac magnetic resonancemeasurements of cardiac output/index in paediatric orthotopic heart transplant patients have poor concordance with Fick estimates; however, cardiac magnetic resonance has good internal validity and inter-reader reliability. Radiation doses are small for haemodynamics with biopsy and increase exponentially with angiography, identifying a new target for cardiac magnetic resonance imaging.

Quantitative flow ratio computed from invasive coronary angiography as a predictor for cardiac allograft vasculopathy after cardiac transplant

Cardiac allograft vasculopathy (CAV) is a significant determinant of long-term survival in heart transplant recipients. Standard CAV screening typically utilizes invasive coronary angiography (ICA). Quantitative flow ratio (QFR) is a computational method for functional testing of coronary stenosis, and may add diagnostic value to ICA in assessing CAV. Consecutive subjects who received heart transplantation and underwent two separate routine coronary angiograms between January 2013 and April 2016 were enrolled. Coronary angiograms and IVUS were performed per local protocol at 1, 2, 3 and 5 years post-transplant. QFR was calculated offline. CAV was assessed semi-quantitively based on coronary angiogram results. Twenty-two patients were enrolled. Mean time from transplant to first included ICA was 2.1 years. QFR in at least 1 coronary vessel was interpretable in 19/22 (86%) of initial ICA (QFR1). QFR1 correlated well with the CAV score derived from the second ICA (CAV2) with a clustering of CAV at lower QFR values. In a receiver-operating characteristic (ROC) analysis, an optimal QFR threshold of 0.88 yielded 0.94 sensitivity and 0.67 specificity (AUC of 0.79) for at least non-obstructive subsequent CAV. Initial angiographically and intravascular ultrasound derived CAV severity poorly predicted subsequent CAV severity. QFR derived from invasive coronary angiography predicts subsequent development of CAV more accurately than angiography and intravascular ultrasound. This novel method of coronary flow assessment in recipients of heart transplantation may be useful to diagnose and predict subsequent CAV development.

CT Coronary Angiography and Dynamic CT Myocardial Perfusion for Detection of Cardiac Allograft Vasculopathy

BACKGROUND

Cardiac allograft vasculopathy (CAV) is a major obstacle limiting long-term graft survival. Effective noninvasive surveillance modalities reflecting both coronary artery and microvascular components of CAV are needed.

OBJECTIVES

The authors evaluated the diagnostic performance of dynamic computed tomography-myocardial perfusion imaging (CT-MPI) and coronary computed tomography angiography (CCTA) for CAV.

METHODS

A total of 63 heart transplantation patients underwent combined CT-MPI and CCTA plus invasive coronary angiography (ICA) with intravascular ultrasonography (IVUS) between December 2018 and October 2021. The median interval between CT-MPI and heart transplantation was 4.3 years. Peak myocardial blood flow (MBF) of the whole myocardium (MBF_global) and minimum MBF (MBF_min) among the 16 segments according to the American Heart Association model, except the left ventricular apex, were calculated from CT-MPI. CCTA was assessed qualitatively, and the degree of coronary artery stenosis was recorded. CAV was diagnosed based on both ICA (ISHLT criteria) and IVUS. Patients were followed up for a median time of 2.3 years after CT-MPI and a median time of 5.7 years after transplantation.

RESULTS

Among the 63 recipients, 35 (55.6%) had diagnoses of CAV. The median MBF_global and MBF_min were significantly lower in patients with CAV (128.7 vs 150.4 mL/100 mL/min; P = 0.014; and 96.9 vs 122.8 mL/100 mL/min; P < 0.001, respectively). The combined use of coronary artery stenosis on CCTA and MBF_min showed the highest diagnostic performance with an area under the curve of 0.886 (sensitivity: 74.3%, specificity: 96.4%, positive predictive value: 96.3%, and negative predictive value: 75.0%).

CONCLUSIONS

The combination of CT-MPI and CCTA demonstrated excellent diagnostic performance for the detection of CAV. One-stop evaluation of the coronary artery and microvascular components involved in CAV using combined CCTA and CT-MPI may be a potent noninvasive screening method for early detection of CAV.

Near-Infrared Spectroscopy-Guided Percutaneous Coronary Intervention: Practical Applications and Available Evidence

Intracoronary near-infrared spectroscopy (NIRS) has been extensively validated against the gold standard of histopathology to identify lipid-rich plaque. NIRS is currently in clinical use as a combined multimodality imaging catheter with intravascular ultrasonography. When used before PCI, NIRS has clinical utility in determining the mechanism underlying acute coronary syndromes and can be used to guide stent length selection and identify the risk of periprocedural myocardial infarction. When used after PCI, NIRS can identify vulnerable patients at increased risk of future patient-level cardiovascular events and can detect vulnerable plaques at increased risk of future site-specific coronary events.

Early trends in cardiac allograft vasculopathy after implementation of the 2018 donor heart allocation policy in the United States

STUDY OBJECTIVE

To evaluate the impact of the new donor heart allocation system implemented in the United States in October 2018 on development of early cardiac allograft vasculopathy (CAV).

DESIGN

Retrospective cohort study.

PARTICIPANTS

Adult (≥ 18 years) heart transplant recipients registered in the United Network for Organ Sharing database between October 18, 2015 and October 17, 2018 (old system) and October 18, 2018 and May 31, 2020 (new system).

MAIN OUTCOME MEASURE

Incidence of angiographic CAV at 1 year (accelerated CAV) in the overall transplant population and among the highest acuity subgroup-Status 1A (old) and Status 1 or 2 (new). We included recipient and donor demographic, cardiovascular, and transplant factors in multivariable logistic regression models to identify predictors of accelerated CAV.

RESULTS

Of 10,375 transplant recipients, 6,660 (64%) and 3,715 (36%) were listed in the old and new allocation cohorts, respectively. The incidence of accelerated CAV was 521 (8%) in the old period compared with 272 (7%) in the new period (P = .36). Similar incidence rates were observed in the highest acuity subgroup-363 (8%) compared with 143 (7%), respectively (P = .13). In adjusted analyses of the high-acuity cohort, the new allocation system was not associated with a higher likelihood of accelerated CAV (odds ratio = 0.87, 95% confidence interval: 0.70-1.08, P = .20).

CONCLUSIONS

The new donor heart allocation system is not associated with development of accelerated angiographic CAV at 1 year, including among recipients requiring the most urgent transplants.

Optical coherence tomography in coronary atherosclerosis assessment and intervention

Since optical coherence tomography (OCT) was first performed in humans two decades ago, this imaging modality has been widely adopted in research on coronary atherosclerosis and adopted clinically for the optimization of percutaneous coronary intervention. In the past 10 years, substantial advances have been made in the understanding of in vivo vascular biology using OCT. Identification by OCT of culprit plaque pathology could potentially lead to a major shift in the management of patients with acute coronary syndromes. Detection by OCT of healed coronary plaque has been important in our understanding of the mechanisms involved in plaque destabilization and healing with the rapid progression of atherosclerosis. Accurate detection by OCT of sequelae from percutaneous coronary interventions that might be missed by angiography could improve clinical outcomes. In addition, OCT has become an essential diagnostic modality for myocardial infarction with non-obstructive coronary arteries. Insight into neoatherosclerosis from OCT could improve our understanding of the mechanisms of very late stent thrombosis. The appropriate use of OCT depends on accurate interpretation and understanding of the clinical significance of OCT findings. In this Review, we summarize the state of the art in cardiac OCT and facilitate the uniform use of this modality in coronary atherosclerosis. Contributions have been made by clinicians and investigators worldwide with extensive experience in OCT, with the aim that this document will serve as a standard reference for future research and clinical application.

Multiparametric Cardiac Magnetic Resonance Imaging Detects Altered Myocardial Tissue and Function in Heart Transplantation Recipients Monitored for Cardiac Allograft Vasculopathy

BACKGROUND

Cardiac allograft vasculopathy (CAV) is a complication beyond the first-year post-heart transplantation (HTx). We aimed to test the utility of cardiac magnetic resonance (CMR) to detect functional/structural changes in HTx recipients with CAV.

METHODS

Seventy-seven prospectively recruited HTx recipients beyond the first-year post-HTx and 18 healthy controls underwent CMR, including cine imaging of ventricular function and T1- and T2-mapping to assess myocardial tissue changes. Data analysis included quantification of global cardiac function and regional T2, T1 and extracellular volume based on the 16-segment model. International Society for Heart and Lung Transplantation criteria was used to adjudicate CAV grade (0–3) based on coronary angiography.

RESULTS

The majority of HTx recipients (73%) presented with CAV (1: n = 42, 2/3: n = 14, 0: n = 21). Global and segmental T2 (49.5 ± 3.4 ms vs 50.6 ± 3.4 ms, p < 0.001;16/16 segments) were significantly elevated in CAV-0 compared to controls. When comparing CAV-2/3 to CAV-1, global and segmental T2 were significantly increased (53.6 ± 3.2 ms vs. 50.6 ± 2.9 ms, p < 0.001; 16/16 segments) and left ventricular ejection fraction was significantly decreased (54 ± 9% vs. 59 ± 9%, p < 0.05). No global, structural, or functional differences were seen between CAV-0 and CAV-1.

CONCLUSIONS

Transplanted hearts display functional and structural alteration compared to native hearts, even in those without evidence of macrovasculopathy (CAV-0). In addition, CMR tissue parameters were sensitive to changes in CAV-1 vs. 2/3 (mild vs. moderate/severe). Further studies are warranted to evaluate the diagnostic value of CMR for the detection and classification of CAV.

Patterns of Early Coronary Artery Changes in Pediatric Heart Transplant Recipients Detected Using Optical Coherence Tomography

BACKGROUND

Cardiac allograft vasculopathy, the leading cause of graft failure in pediatric heart transplant recipients, is characterized by diffuse and concentric coronary intimal thickening. Early treatment yields better outcomes. While coronary angiography is the standard for cardiac allograft vasculopathy screening and diagnosis, it only identifies luminal narrowing, which occurs in more severe disease. Coronary optical coherence tomography (OCT) is a high-definition intravascular imaging modality that may offer earlier diagnosis. We used OCT to investigate coronary intimal thickening in pediatric transplant recipients and examined its (1) location (ie, vessel type and location) and (2) nature (ie, characteristics of cross-sectional and longitudinal thickening).

METHODS

Sites collected coronary angiography and OCT data from participants (N=258 vessel segments from 73 individuals; median age: 11.5 years [8.4-15.3]; 55% male). Images were collected from the left anterior descending, left circumflex, and right coronary arteries, and location (ie, proximal, middle, and distal) were classified using coronary angiography.

RESULTS

OCT identified 32 vessel segments meeting criteria for significant thickening, 88% of which were angiographically silent. Longitudinal thickening was segmental rather than global in 88%, and cross-sectional thickening was 48% eccentric and 52% concentric. Intimal thickening prevalence and severity measures did not consistently differ between coronary artery type (P=1.000) or location (P=0.248) but increased with time since transplant and age at transplant and OCT procedure.

CONCLUSIONS

In pediatric transplant recipients, we observed a surprisingly high prevalence of segmental and eccentric intimal thickening. Insights from intravascular imaging suggest these patterns of coronary vascular changes may precede overt cardiac allograft vasculopathy. Identifying early changes may offer opportunity for enhanced surveillance and earlier intervention.

The fundamental role of stress echo in evaluating coronary artery disease in specific patient populations

Stress echocardiography (SE) was initially used for assessing patients with known or suspected coronary heart disease by detecting and evaluating myocardial ischemia and viability. The implementation of SE has gradually been extended to several cardiovascular diseases beyond coronary artery disease, and SE protocols have been modified and adapted for the detection of coronary artery disease (CAD) or other cardiovascular diseases in specific patient populations. This review attempts to summarize current data concerning SE implementation and clinical value in these specific and diverse populations: patients with an intramural course of a coronary artery - known as a myocardial bridge, chronic severe or end-stage hepatic disease, chronic severe or end-stage kidney disease, cardiac allograft vasculopathy, patients scheduled for solid-organ transplantation and other intermediate and high-risk surgery and, finally, patients treated with anticancer drugs or radiotherapy.

Validation of multiparametric rubidium-82 PET myocardial blood flow quantification for cardiac allograft vasculopathy surveillance

BACKGROUND

We previously demonstrated high diagnostic accuracy of Rubidium-82 positron emission tomography (PET) myocardial blood flow (MBF) quantification for CAV. The purpose of this study was to validate multiparametric PET detection of CAV by combined rate-pressure-product-corrected myocardial flow reserve (cMFR), stress MBF, and coronary vascular resistance (CVR) assessment.

METHODS AND RESULTS

Diagnostic CAV cut-offs of cMFR < 2.9, stress MBF < 2.3, CVR > 55 determined in a previous study (derivation) were assessed in heart transplant recipients referred for coronary angiography and intravascular ultrasound (IVUS) (validation). CAV was defined as International Society of Heart and Lung Transplantation CAV1-3 on angiography; and maximal intimal thickness ≥ 0.5 mm on IVUS. Eighty patients (derivation n = 40, validation n = 40) were included: 80% male, mean age 54±14 years, 4.5±5.6 years post transplant. The prevalence of CAV was 44% on angiography and 78% on IVUS. Combined PET cMFR < 2.9, stress MBF < 2.3, CVR > 55 CAV assessment yielded high 88% (specificity 75%) and 83% (specificity 40%) sensitivity for ≥ 1 abnormal parameter and high 88% (sensitivity 59%) and 90% (sensitivity 43%) specificity for 3 abnormal parameters, in the derivation and validation cohorts, respectively.

CONCLUSION

We validate the diagnostic accuracy of multiparametric PET flow quantification by cMFR, stress MBF, and CVR for CAV.

Optical Coherence Tomography in Cardiac Allograft Vasculopathy: State-of-the-Art Review

Cardiac allograft vasculopathy (CAV) is a challenging complication of heart transplantation. CAV pathophysiology is incompletely understood, standard screening modalities such as angiography have significant limitations, and currently available therapies have only modest efficacy in preventing progression. Optical coherence tomography is a light-based technique that provides microscopic level catheter-based intravascular imaging and has dramatically expanded our understanding of CAV, demonstrating it to be a complex, heterogeneous, and dynamic process. This review covers characteristics and uses of optical coherence tomography, including vessel characterization, serial use to assess progression of disease, guiding percutaneous intervention, and monitoring response to CAV therapies. We also discuss the potential of optical coherence tomography in providing individualized assessment and enable customized CAV therapies, which may lead to improvements in long-term transplant outcomes.

Feasibility and safety of quantitative adenosine stress perfusion cardiac magnetic resonance imaging in pediatric heart transplant patients with and without coronary allograft vasculopathy

BACKGROUND

Pediatric heart transplant patients require cardiac catheterization to monitor for coronary allograft vasculopathy. Cardiac catheterization has no safe and consistent method for measuring microvascular disease. Stress perfusion cardiac magnetic resonance imaging (MRI) assessing microvascular disease has been performed in adults.

OBJECTIVE

To investigate the feasibility and safety of performing cardiac MRI with quantitative adenosine stress perfusion testing in pediatric heart transplant patients with and without coronary allograft vasculopathy.

MATERIALS AND METHODS

All pediatric heart transplant patients with coronary vasculopathy at our institution were asked to participate. Age- and gender-matched pediatric heart transplant patients without vasculopathy were recruited for comparison. Patients underwent cardiac MRI with adenosine stress perfusion testing.

RESULTS

Sixteen pediatric heart transplant patients, ages 6-22 years, underwent testing. Nine patients had vasculopathy by angiography. No heart block or other complications occurred during the study. The myocardial perfusion reserve for patients with vasculopathy showed no significant difference with comparison patients (median: 1.43 vs. 1.48; P=0.49). Values for both groups were lower than expected values based on previous adult studies. The patients were also analyzed for time after transplant and the number of rejection episodes. Patients within 6 years of transplantation had a nonsignificant trend toward a higher myocardial perfusion reserve (median: 1.57) versus patients with older transplants (median: 1.47; P=0.46). Intra- and interobserver reproducibility were 97% and 92%, respectively.

CONCLUSION

Myocardial perfusion reserve is a safe and feasible method for estimating myocardial perfusion in pediatric heart transplant patients. There is no reliable way to monitor microvascular disease in pediatric patients. This method shows potential and deserves investigation in a larger cohort.

Long-Term Prognostic Value of Coronary CTA in Orthotopic Heart Transplant Recipients

OBJECTIVE. This study aimed to evaluate the long-term prognostic value of coronary CTA (CCTA) in heart transplant recipients. MATERIALS AND METHODS. The records of 114 patients who had undergone a heart transplant (mean age, 61.7 ± 11.1 [SD] years; 83.3% men) and who underwent CCTA for the surveillance of coronary allograft vasculopathy (CAV) from June 2007 to December 2017 were retrospectively evaluated for the occurrence of major adverse cardiovascular events (MACEs) (cardiac death, nonfatal myocardial infarction, unstable angina requiring hospitalization, coronary revascularization, cardiac arrhythmias, stroke, and retransplant). Patients were classified according to the presence of nonobstructive CAV (lumen reduction < 50%) or obstructive disease (lumen reduction ≥ 50%) and using a coronary segment involvement score (SIS). Differences in MACE rate between groups were compared. RESULTS. Obstructive CAV was observed in 12 heart transplant recipients (10.5%). During a mean follow-up of 67.5 ± 41.4 months the overall rates of MACE were 50% and 14.7% in patients with obstructive and nonobstructive CAV, respectively (p < .05), resulting in an odds ratio for MACE of 6 (95% CI, 1.7-21.2). Comparison of event-free survival showed a hazard ratio (HR) of 5 (95% CI, 1.95-13; p =. 004) for patients with obstructive disease. The presence of four or more stenotic coronary segments (SIS ≥ 4) was associated with a higher rate of events (HR, 3.46; 95% CI, 1.46-8.23). CONCLUSION. In patients who have undergone a heart transplant, CCTA offers a significant long-term prognostic impact on the prediction of MACEs.

Imaging of Cardiac Transplantation: An Overview

Heart transplantation (HTx) remains the optimal treatment for selected patients with end-stage advanced heart failure. However, survival is limited early by acute rejection and long term by cardiac allograft vasculopathy (CAV). Even though the diagnosis of rejection is based on histology, cardiac imaging provides a pivotal role for early detection and severity assessment of these hazards. The present review focuses on the use and reliability of different invasive and non-invasive imaging modalities to detect and monitor CAV and rejection after HTx. Coronary angiography remains the corner stone in routine CAV surveillance. However, angiograms are invasive and underestimates the CAV severity especially in the early phase. Intravascular ultrasound and optical coherence tomography are invasive methods for intracoronary imaging that detects early CAV lesions not evident by angiograms. Non-invasive imaging can be divided into myocardial perfusion imaging, anatomical/structural imaging and myocardial functional imaging. The different non-invasive imaging modalities all provide clinical and prognostic information and may have a gatekeeper role for invasive monitoring. Acute rejection and CAV are still significant clinical problems after HTx. No imaging modality provides complete information on graft function, coronary anatomy and myocardial perfusion. However, a combination of invasive and non-invasive modalities at different stages following HTx should be considered for optimal personalized surveillance and risk stratification.

A primer for managing cardiac transplant patients in the emergency department setting

BACKGROUND

Cardiac transplant is an effective long-term management option for several severe cardiac diseases. These cardiac transplant patients may present to the emergency department with a range of issues involving the cardiac transplantation, including complications due to their transplant as well as altered presentations of disease resulting from their transplant.

OBJECTIVE

This narrative review provides a focused guide to the evaluation and management of patients with cardiac transplantation and its complications.

DISCUSSION

Cardiac transplant is an effective therapy for end-stage heart failure. A transplanted heart varies both anatomically and physiologically from a native heart. Several significant complications may occur. Graft failure, rejection, and infection are common causes of morbidity and mortality within the first year of transplant. As these patients are on significant immunosuppressive medication regimens, they are at risk of infection, but inadequate immunosuppression increases the risk of acute rejection. A variety of dysrhythmias such as atrial fibrillation and ventricular dysrhythmias may occur. These patients are also at risk of acute coronary syndrome, cardiac allograft vasculopathy, and medication adverse events. Importantly, patients with acute coronary syndrome can have an altered presentation with the so-called "painless" myocardial infarction. Consultation with the transplant physician is recommended, if available, for these patients to assist in evaluation and management.

CONCLUSIONS

An understanding of the presentations and various complications that may affect patients with cardiac transplant will assist emergency clinicians in the care of these patients.

Cardiac allograft vasculopathy: Differences of absolute and relative intimal hyperplasia in children versus adults in optical coherence tomography

BACKGROUND

Intracoronary imaging enables an early detection of intimal changes. To what extend the development of absolute and relative intimal hyperplasia in intracoronary imaging differs depending on age and post-transplant time is not known.

METHODS

Aim of our retrospective study was to compare findings between 24 pediatric (cohort P) and 21 adult HTx patients (cohort A) using optical coherence tomography (OCT) at corresponding post-transplant intervals (≤5 years: P1 (n = 11) and A1 (n = 10); >5 and ≤ 10 years: P2 (n = 13) and A2 (n = 11),. Coronary intima thickness (IT), media thickness (MT) and intima to media ratio (I/M) were assessed per quadrant. Maximal IT >0.3 mm was considered absolute, I/M > 1 relative intimal hyperplasia.

RESULTS

Compared to A1, I/M was significantly higher in P1 (maximal I/M: P1: 5.41 [2.81-13.39] vs. A1: 2.30 [1.55-3.62], p = 0.005), whereas absolute IT values were comparable. In contrast, I/M was comparable between P2 and A2, but absolute IT were significantly higher in A2 (maximal IT: P2: 0.16 mm [0.11-0.25] vs. A2: 0.40 mm [0.30-0.71], p < 0.001). A2 presented with higher absolute IT (maximal: A1: 0.16 mm [0.12-0.44] vs. A2: 0.40 mm [0.30-0.71], p = 0.02) and I/M (maximal I/M A1: 2.30 [1.55-3.62] vs. A2: 3.79 [3.01-5.62], p = 0.04).

CONCLUSION

Our results suggest an age- and time-dependent difference in the prevalence of absolute and relative intimal hyperplasia in OCT, with an early peak in children and a progressive increase in adults.

Assessment of late-term progression of cardiac allograft vasculopathy in patients with orthotopic heart transplantation using quantitative cardiac 82Rb PET

The risk stratification and long-term survival of patients with orthotopic heart transplantation (OHT) is impacted by the complication of cardiac allograft vasculopathy (CAV). This study evaluates changes in myocardial blood flow (MBF) and myocardial coronary flow reserve (CFR) in a group of long-term OHT patients using quantitative cardiac ⁸²Rb-positron emission tomography (PET). Twenty patients (7 females and 13 males, mean age = 72.7 ± 12.2 years with CAV and 62.9 ± 7.2 years without CAV and post-OHT mean time = 13.9 years), were evaluated retrospectively using dynamic cardiac ⁸²Rb-PET at rest and regadenoson-induced stress. The patients also underwent selective coronary angiography (SCA) for diagnosis and risk stratification. CAV was diagnosed based on SCA findings and maximal intimal thickness greater than 0.5 mm, as defined by International Society of Heart and Lung Transplantation (ISHLT). Global and regional MBFs were estimated in three vascular territories using the standard 1-tissue compartment model for dynamic ⁸²Rb-PET. The myocardial CFR was also calculated as the ratio of peak stress MBF to rest MBF. Among twenty patients, seven had CAV in, at least, one major coronary artery (ISHLT CAV grade 1 or higher) while 13 patients did not have CAV (NonCAV). Mean rate-pressure products (RPP) at rest were significantly elevated in CAV patients compared to those without CAV (P = 0.002) but it was insignificant at stress (P = NS). There was no significant difference in the stress MBFs between CAV and NonCAV patients (P = NS). However, the difference in RPP-normalized stress MBFs was significant (P = 0.045), while RPP-normalized MBFs at rest was not significant (P = NS). Both CFR and RPP-normalized CFR were significantly lower in CAV compared to NonCAV patients (P < 0.001). There were significant correlations between MBFs and RPPs at rest for both CAV (ρ = 0.764, P = 0.047) and NonCAV patients (ρ = 0.641, P = 0.017), while there were no correlations at stress for CAV (ρ = 0.232, P = NS) and NonCAV patients (ρ = 0.068, P = NS). This study indicates that the resting MBF is higher in late-term post-OHT patients. The high resting MBF and reduced CFR suggest an unprecedented demand of blood flow and blunted response to stress due to impaired vasodilatory capacity that is exacerbated by the presence of CAV.

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

BACKGROUND

Noninvasive screening for cardiac allograft vasculopathy (CAV) instead of invasive coronary angiography (ICA) within the first 3 to 5 years after heart transplantation (HTx) is controversial. We evaluated a strategy of intravascular ultrasound (IVUS)-guided conversion to early noninvasive screening post-HTx.

METHODS

A single-center study of 103 consecutive HTx recipients from 2008 to 2018 undergoing ICA at 1 year post-HTx. Of 88 patients with normal 1-year ICA, sixty-six patients underwent IVUS examination for risk stratification by maximal intimal thickness (MIT) into (i) low-risk group (MIT < 0.5 mm) (n = 41, 62%) followed noninvasively versus (ii) high-risk group (MIT ≥ 0.5 mm) (n = 25, 38%) followed with yearly ICA. Both groups underwent ICA at year 5 post-HTx. We evaluated a combined endpoint of angiographic CAV and death at 5-year follow-up post-HTx.

RESULTS

Median (IQR) age was 51 (33-60) years, and 62% were male. Follow-up was 1443 (1125-1456) days. Survival free from angiographic CAV (Kaplan-Meier) differed significantly between groups (log-rank p < .0001). A subgroup of 27 patients completed ICA at year 5, and the proportion of angiographic CAV was significantly lower in low-risk patients (p < .0001).

CONCLUSION

IVUS-guided selection for early noninvasive CAV screening appears to be safe and holds promise as a novel strategy for early risk stratification and CAV surveillance post-HTx.

Cardiac allograft vasculopathy: Incidence and predictors in a single-center cohort

INTRODUCTION AND AIMS

Cardiac allograft vasculopathy (CAV) is one of the most significant complications after orthotopic heart transplantation. We aimed to investigate the incidence and predictors of CAV in a large cohort of orthotopic heart transplantation patients.

METHODS

We conducted a retrospective analysis on a prospective cohort of 233 patients who underwent transplantation between November 2003 and May 2014. Baseline clinical data and invasive coronary angiograms (n=712) performed as part of the follow-up program were analyzed by two independent investigators.

RESULTS

We included 157 male and 45 female patients with a median age of 66 years. A third of patients had previous ischemic heart disease, 30% peripheral arterial disease, 37% hypertension and 47% dyslipidemia, and 17% were smokers. Acute moderate or severe rejection occurred in 42 patients during the first year. Over a median follow-up of 2920 days, 18% were diagnosed with CAV, with an incidence of 2.91 cases per 100 person-years. Predictors of CAV were previous ischemic heart disease (HR 2.32, 95% CI 1.21-4.45, p=0.01), carotid artery disease (HR 2.44, 95% CI 1.27-4.71, p<0.01), and donor age (HR 1.04, 95% CI 1.00-1.07, p=0.01).

CONCLUSION

In a single-center cohort of orthotopic heart transplantation patients, predictors of CAV were previous ischemic heart disease, carotid artery disease and donor age.

Mild acute cellular rejection and development of cardiac allograft vasculopathy assessed by intravascular ultrasound and coronary angiography in heart transplant recipients-a SCHEDULE trial substudy

To evaluate the association between mild acute cellular rejection (ACR) and the development of cardiac allograft vasculopathy (CAV) after heart transplantation (HTx). Substudy of the SCHEDULE trial (n = 115), where de novo HTx recipients were randomized to (i) everolimus with early CNI elimination or (ii) CNI-based immunosuppression. Seventy-six patients (66%) were included based on matched intravascular ultrasound (IVUS) examinations at baseline and year 3 post-HTx. Biopsy-proven ACR within year 1 post-HTx was recorded and graded (1R, 2R, 3R). Development of CAV was assessed by IVUS and coronary angiography at year 3 post-HTx. Median age was 53 years (45-61), and 71% were male. ACR was recorded in 67%, and patients were grouped by rejection profile: no ACR (33%), only 1R (42%), and ≥2R (25%). Median ∆MIT (maximal intimal thickness)_BL-3Y was not significantly different between groups (P = 0.84). The incidence of CAV was 49% by IVUS and 26% by coronary angiography with no significant differences between groups. No correlation was found between number of 1R and ∆MIT_BL-3Y (r = -0.025, P = 0.83). The number of 1R was not a significant predictor of ∆MIT_BL-3Y (P = 0.58), and no significant interaction with treatment was found (P = 0.98). The burden of mild ACR was not associated with CAV development.

Pharmacological vs Exercise Stress Echocardiography for Detection of Cardiac Allograft Vasculopathy

Objective

To test the hypothesis that exercise and dobutamine would provide levels of cardiac stress that are comparable to those achieved in a general stress test population, and to one another, in heart transplant recipients.

Patients and Methods

From February 10, 2015, to December 31, 2017, 81 patients underwent exercise stress (N=45) or dobutamine stress (N=36) echocardiography at a mean ± SD of 11±14 years (range, 1-29 years) after heart transplant. Hemodynamic and inotropic responses were compared between groups, and to a prior test, longitudinally. The primary outcome was peak heart rate (HR) × systolic blood pressure (SBP).

Results

Peak exercise HR × SBP × 10⁻³ was a mean ± SD of 24.9±4.9 mm Hg/min for exercise stress vs 21.2±3.4 mm Hg/min during dobutamine stress (P<.001). In 35 patients who underwent a dobutamine stress test followed later by another dobutamine stress test, peak HR × SBP changed by 4.2%±16% (P=.05). In 25 patients who underwent a dobutamine stress test followed later by an exercise stress test, peak HR × SBP increased by 12%±23% (P=.002 vs serial dobutamine stress tests). Peak exercise HR did not correlate with time since heart transplant, patient age, or graft age. Peak dobutamine HR correlated modestly with patient age (r²=0.28). Inotropic responses were similar in both groups. Overall, patients preferred exercise stress testing to dobutamine stress tests. Dobutamine stress testing was more expensive than exercise stress tests.

Conclusion

Exercise induces a level of cardiac stress that is equal to or greater than dobutamine-induced stress, at lower cost, in heart transplant recipients who express preference for exercise stress testing.

Semi-quantitative myocardial perfusion MRI in heart transplant recipients at rest: repeatability in healthy controls and assessment of cardiac allograft vasculopathy

BACKGROUND

Cardiac Allograft Vasculopathy (CAV) is a major cause of chronic cardiac allograft failure. Invasive coronary angiography (ICA) and intravascular ultrasound (IVUS) are the current diagnostic methods. Myocardial perfusion MRI has become a promising non-invasive method to evaluate myocardial ischemia, but has not been thoroughly validated in CAV. Our objective was to assess the repeatability of myocardial rest-perfusion MRI in healthy volunteers and its feasibility in detecting CAV in transplant patients (Tx).

METHODS

Twelve healthy volunteers and twenty transplant patients beyond the first year post- transplant underwent cardiac MRI at 1.5 T at rest including first-pass perfusion imaging in short axis (base, mid, apex) after injection of gadolinium. Volunteers underwent repeated cardiac MRI on different days (interval = 15.6 ± 2.4 days) to assess repeatability. Data analysis included semi-automatic contouring of endocardial and epicardial borders of the left ventricle (LV) and quantification of peak perfusion, time-to-peak (TTP) perfusion, and upslope of the perfusion curve.

RESULTS

Between scans and re-scans in healthy volunteers, peak signal intensity, slope, and TTP demonstrated moderate agreement (ICC = 0.53, 0.48, and 0.59, respectively; all, p < .001). Peak signal intensity, slope, and TTP were moderately variable with COV values of 23%, 42%, and 35%, respectively. Peak perfusion was significantly reduced in CAV positive (n = 9 Tx patients) compared to CAV negative (n = 11 Tx patients) groups (90.7 ± 27.0 vs 139.5 ± 30.2, p < .001).

CONCLUSION

Cardiac MRI is a moderately repeatable method for the semi-quantitative assessment of first-pass myocardial perfusion at rest. Semi-quantitative surrogate markers of LV perfusion could play a role in CAV detection.

Multi-modal imaging of the pediatric heart transplant recipient

The assessment of pediatric patients after orthotropic heart transplantation (OHT) relies heavily on non-invasive imaging. Because of the potential risks associated with cardiac catheterization, expanding the role of non-invasive imaging is appealing. Echocardiography is fast, widely available, and can provide an accurate assessment of chamber sizes and function. Advanced echocardiographic methods, such as myocardial deformation, have potential to assess for acute rejection or cardiac allograft vasculopathy (CAV). While not currently part of routine care, cardiac magnetic resonance imaging (CMR) and computed tomography may potentially aid in the detection of graft complications following OHT. In particular, CMR tissue characterization holds promise for diagnosing rejection, while quantitative perfusion and myocardial late gadolinium enhancement may have a role in the detection of CAV. This review will evaluate standard and novel methods for non-invasive assessment of pediatric patients after OHT.

Reduced Myocardial Flow Reserve by Positron Emission Tomography Predicts Cardiovascular Events After Cardiac Transplantation

BACKGROUND

We evaluated the diagnostic and prognostic value of quantification of myocardial flow reserve (MFR) with positron emission tomography (PET) in orthotopic heart transplant patients.

METHODS AND RESULTS

We retrospectively identified orthotopic heart transplant patients who underwent rubidium-82 cardiac PET imaging. The primary outcome was the composite of cardiovascular death, acute coronary syndrome, coronary revascularization, and heart failure hospitalization. Cox regression was used to evaluate the association of MFR with the primary outcome. The relationship of MFR and cardiac allograft vasculopathy severity in patients with angiography within 1 year of PET imaging was assessed using Spearman rank correlation and logistic regression. A total of 117 patients (median age, 60 years; 71% men) were identified. Twenty-one of 62 patients (34%) who underwent angiography before PET had cardiac allograft vasculopathy. The median time from orthotopic heart transplant to PET imaging was 6.4 years (median global MFR, 2.31). After a median of 1.4 years, 22 patients (19%) experienced the primary outcome. On an unadjusted basis, global MFR (hazard ratio, 0.22 per unit increase; 95% confidence interval, 0.09-0.50; P<0.001) and stress myocardial blood flow (hazard ratio, 0.48 per unit increase; 95% confidence interval, 0.29-0.79; P=0.004) were associated with the primary outcome. Decreased MFR independently predicted the primary outcome after adjustment for other variables. In 42 patients who underwent angiography within 12 months of PET, MFR and stress myocardial blood flow were associated with moderate-severe cardiac allograft vasculopathy (International Society of Heart and Lung Transplantation grade 2-3).

CONCLUSIONS

MFR assessed by cardiac rubidium-82 PET imaging is a predictor of cardiovascular events after orthotopic heart transplant and is associated with cardiac allograft vasculopathy severity.

Prediction of long-term (> 10 year) cardiovascular outcomes in heart transplant recipients: Value of stress technetium-99m tetrofosmin myocardial perfusion imaging

BACKGROUND

Myocardial perfusion imaging (MPI) using single-photon emission computed tomography (SPECT) is useful in the evaluation of cardiac allograft vasculopathy (CAV) in heart transplant (HTx) recipients. The current study evaluated the long-term prognostic value of stress SPECT MPI for predicting all-cause mortality and cardiac events in HTx recipients.

METHODS

The study population consisted of 166 HTx recipients (mean age 54 ± 10 years, 84% male) who underwent exercise or dobutamine stress 99mTc-tetrofosmin SPECT MPI for the assessment of CAV. An abnormal SPECT MPI was defined as the presence of a fixed or a reversible perfusion defect. Endpoints were all-cause mortality, cardiac mortality, and non-fatal myocardial infarction (MI).

RESULTS

MPI abnormalities were detected in 55 patients (33%), including fixed defects in 28 patients (17%), partially reversible in 17 patients (10%), and completely reversible defects in 10 patients (6%). During a median follow-up of 12.8 years (range 0-15, mean follow-up 9.5 years), 109 (66%) patients died (all-cause mortality), of which 67 (40%) were due to cardiac causes. A total of 5 (3%) patients experienced a non-fatal MI. HTx recipients with a normal stress 99mTc-tetrofosmin SPECT MPI had a significantly better prognosis as compared with those with an abnormal study, up to 5 years after the initial test. The presence of a reversible perfusion defect was a significant predictor of all-cause mortality, cardiac mortality, and major cardiac events, during the entire follow-up period.

CONCLUSIONS

Stress 99mTc-tetrofosmin SPECT MPI provides valuable prognostic information for the prediction of long-term outcome in HTx recipients. Patients with a normal stress 99mTc-tetrofosmin SPECT MPI have a significantly better prognosis as compared with those with an abnormal study, up to 5 years after initial testing.

Emerging Techniques for Cardiovascular PET

The application of positron emission tomography (PET) to cardiac disease has yielded tremendous developments in the evaluation of coronary artery, myocardial, and valvular heart disease over the past several decades. These advances have included development of new radiotracers, incremental technological improvements, and coupling of PET with other non-invasive cardiac imaging modalities. The current era has seen rapid, successive and wide-ranging advances in PET myocardial perfusion and metabolic imaging. This review will address emerging techniques in cardiovascular PET imaging, including the measurement of absolute myocardial blood flow (MBF), use of novel tracers, and other advances in heart failure, infection imaging, and valvular disease.

Safety and prognostic value of regadenoson stress cardiovascular magnetic resonance imaging in heart transplant recipients

BACKGROUND

There is a critical need for non-invasive methods to detect coronary allograft vasculopathy and to risk stratify heart transplant recipients. Vasodilator stress testing using cardiovascular magnetic resonance imaging (CMR) is a promising technique for this purpose. We aimed to evaluate the safety and the prognostic value of regadenoson stress CMR in heart transplant recipients.

METHODS

To evaluate the safety, we assessed adverse effects in a retrospective matched cohort study of consecutive heart transplant recipients who underwent regadenoson stress CMR matched in a 2:1 ratio to age- and gender-matched non-heart transplant patients. To evaluate the prognostic value, we compared the outcomes of patients with abnormal vs. normal regadenoson stress CMRs using a composite endpoint of myocardial infarction, percutaneous intervention, cardiac hospitalization, retransplantation or death.

RESULTS

For the safety analysis, 234 regadenoson stress CMR studies were included - 78 performed in 57 heart transplant recipients and 156 performed in non-heart transplant patients. Those in heart transplant recipients were performed at a median of 2.74 years after transplantation. Thirty-four (44%) CMR studies were performed in the first two years after heart transplantation. There were no differences in the rates of adverse effects between heart transplant recipients and non-heart transplant patients. To study the prognostic value of regadenoson stress CMRs, 20 heart transplant recipients with abnormal regadenoson stress CMRs were compared to 37 with normal regadenoson stress CMRs. An abnormal regadenoson stress CMR was associated with a significantly higher incidence of the composite endpoint compared with a normal regadenoson stress CMR (3-year cumulative incidence estimates of 32.1% vs. 12.7%, p = 0.034).

CONCLUSIONS

Regadenoson stress CMR is safe and well tolerated in heart transplant recipients, with no incidence of sinus node dysfunction or high-degree atrioventricular block, including in the first two years after heart transplantation. An abnormal regadenoson stress CMR identifies heart transplant recipients at a higher risk for major adverse cardiovascular events.

High-Sensitivity Troponin T and Soluble Form of AXL as Long-Term Prognostic Biomarkers after Heart Transplantation

Antecedents

Cardiac allograft vasculopathy (CAV) is a frequent complication limiting the long-term (>1 year) survival after heart transplantation (HTx). CAV is initiated by endothelial dysfunction and can lead to severe cardiovascular (CV) complications. Since CAV is often clinically silent, biomarkers could help identifying HTx patients at risk of CAV and their severe complications.

Aim

Evaluate the clinical yield of high-sensitivity cardiac troponin T (hs-cTnT), marker of cardiomyocyte damage, and the soluble form of AXL (sAXL), biomarker of endothelial dysfunction, to assess the prognosis of long-term cardiovascular (CV) events occurring after HTx.

Methods

96 patients were evaluated at least > 1 year after HTx. CAV was evaluated by coronary angiography or multisliced tomography, and hs-cTnT and sAXL measured 6 months before or after CAV evaluation. Patients were followed during 42 ± 15 months for a combined end point including cardiac death, angina or acute myocardial infarction, left ventricular ejection fraction < 50%, or heart failure not due to an acute rejection.

Results

51 patients (53%) presented CAV at evaluation; 21 of them had CV events. Hs-cTnT (56 ± 45 versus 20 ± 18 ng/L; p = 0.04) and sAXL concentrations (98 ± 51 versus 26 ± 26 ng/L; p = 0.01) were significantly higher in patients with CV events. Hs-cTnT (HR 1.03; 95% CI 1.015–1.042, p = 0.0001) and sAXL (HR 1.01; 95% CI 1.001–1.019, p = 0.02) were independent predictors of CV events. A hs-cTnT concentration < 21 ng/L, detected by AUC ROC, predicted the absence of CV events with a predictive value of 91%; sAXL did not add more predictive value to hs-cTnT. Survival free of CV events was 92% in patients with hs-cTnT < 21 ng/L and 57% in those with hs-cTnT > 21 ng/L (p < 0.001).

Conclusion

Hs-cTnT, but not sAXL, measured during the long-term follow-up of HTx patients appears as a helpful biomarker to identify patients at low risk of adverse CV outcomes.

Progression of cardiac allograft vasculopathy assessed by serial three-vessel quantitative coronary angiography

Background

The purpose of the present study was to assess the short- and long-term progression of cardiac allograft vasculopathy (CAV) using serial 3-vessel quantitative coronary angiography (QCA).

Methods

CAV progression was assessed using serial 3-vessel QCA analysis at baseline, 1-year and long-term angiographic follow-up (8.5±3.7 years) after heart transplantation. The change in minimal lumen diameter (MLD) and percent diameter stenosis (%DS) was serially assessed within matched segments. Patients were graded according to the ISHLT-CAV classification and grouped as ISHLT-CAV₀ and ISHLT-CAV_1-3. The primary endpoint was mean change in MLD and %DS.

Results

A total of 41 patients and 520 matched segments were available for serial 3-vessel QCA. Overall, MLD decreased non-significantly from baseline to 1-year follow-up and significantly from 1-year to the long-term angiographic follow-up (Δ-0.08mm/year [95%CI -0.11 to -0.05], P<0.001). %DS increased significantly from baseline to 1-year (Δ+0.96%/year [95%CI 0.04 to 1.88], P = 0.041) and from 1-year to long-term angiographic follow-up (Δ+0.61%/year [95%CI 0.33 to 0.88], P<0.001). ISHLT-CAV_1-3 at 1 year and at long-term angiographic follow-up was observed in 22% and 61%, respectively. Between baseline and long-term angiographic follow-up, a significant reduction in MLD was observed within both groups without a significant difference in the reduction between the two groups (ISHLT-CAV₀: median -0.49mm [IQR -0.54 to -0.43] vs. ISHLT-CAV_1-3: median -0.40mm [IQR -0.44 to -0.35], P = 0.4).

Conclusion

The current data suggest that QCA can’t predict CAV beyond 1 year, but, QCA affirmed that CAV progresses to a similar extent in patients who do not develop visual CAV during long-term follow-up.

Cardiopulmonary, biomarkers, and vascular responses to acute hypoxia following cardiac transplantation

Previous studies have suggested good adaptation of cardiac transplant (CTx) recipients to exposure to a high altitude. No studies have investigated the cardiopulmonary and biomarker responses to acute hypoxic challenges following CTx. Thirty-six CTx recipients and 17 age-matched healthy controls (HC) were recruited. Sixteen (16) patients (42%) had cardiac allograft vasculopathy (CAV). Cardiopulmonary responses to maximal and submaximal exercise at 21% O₂ , 20-minutes hypoxia (11.5% O₂ ), and following a 10-minute exposure to 11.5% O₂ using 30% of peak power output were completed. Vascular endothelial growth factor (VEGF), interleukin-6 (IL-6), suppression of tumorigenicity 2 (ST2) were measured at baseline and at peak stress. Endothelial peripheral function was assessed using near-infrared spectroscopy. Compared with HC, CTx presented a lesser O₂ desaturation both at rest (-19.4 ± 6.8 [CTx] vs -24.2 ± 6.0% O₂ [HC], P < 0.05) and following exercise (-23.2 ± 4.9 [CTx] vs -26.2 ± 4.7% O₂ [HC], P < 0.05). CTx patients exhibited a significant decrease in peak oxygen uptake. IL-6 and VEGF levels were significantly higher in CTx recipients in basal conditions but did not change in response to acute stress. CTx patients exhibit a favorable ventilatory and overall response to hypoxic stress. These data provide further insights on the good adaptability of CTx to exposure to high altitude.

Methotrexate associated to lipid core nanoparticles improves cardiac allograft vasculopathy and the inflammatory profile in a rabbit heart graft model

Coronary allograft vasculopathy is an inflammatory-proliferative process that compromises the long-term success of heart transplantation and has no effective treatment. A lipid nanoemulsion (LDE) can carry chemotherapeutic agents in the circulation and concentrates them in the heart graft. The aim of the study was to investigate the effects of methotrexate (MTX) associated to LDE. Rabbits fed a 0.5% cholesterol diet and submitted to heterotopic heart transplantation were treated with cyclosporine A (10 mg·kg^–1·day^–1 orally) and allocated to treatment with intravenous LDE-MTX (4 mg/kg, weekly, n=10) or with weekly intravenous saline solution (control group, n=10), beginning on the day of surgery. Animals were euthanized 6 weeks later. Compared to controls, grafts of LDE-MTX treated rabbits showed 20% reduction of coronary stenosis, with a four-fold increase in vessel lumen and 80% reduction of macrophage staining in grafts. Necrosis was attenuated by LDE-MTX. Native hearts of both LDE-MTX and Control groups were apparently normal. Gene expression of lipoprotein receptors was significantly greater in grafts compared to native hearts. In LDE-MTX group, gene expression of the pro-inflammatory factors tumor necrosis factor-α, monocyte chemoattractant protein-1, interleukin-18, vascular cell adhesion molecule-1, and matrix metalloproteinase-12 was strongly diminished whereas expression of anti-inflammatory interleukin-10 increased. LDE-MTX promoted improvement of the cardiac allograft vasculopathy and diminished inflammation in heart grafts.

Use of Anti-Thymocyte Globulin for Induction Therapy in Cardiac Transplantation: A Review

The most common causes of death after heart transplantation (HTx) include acute rejection and multi-organ failure in the early period and malignancy and cardiac allograft vasculopathy (CAV) in the late period. Polyclonal antibody preparations such as rabbit anti-thymocyte globulin (ATG) may reduce early acute rejection and the later occurrence of CAV after HTx. ATG therapy depletes T cells, modulates adhesion and cell-signaling molecules, interferes with dendritic cell function, and induces B-cell apoptosis and regulatory and natural killer T-cell expansion. Evidence from animal studies and from retrospective clinical studies in humans indicates that ATG can be used to delay calcineurin inhibitor (CNI) exposure after HTx, thus benefiting renal function, and to reduce the incidence of CAV and ischemia-reperfusion injury in the transplanted heart. ATG may reduce de novo antibody production after HTx. ATG does not appear to increase cytomegalovirus infection rates with longer prophylaxis (6-12 months). In addition, ATG may reduce the risk of lymphoproliferative disease and does not appear to confer an additive effect on acquiring lymphoma after HTx. Randomized, controlled trials may provide stronger evidence of ATG association with patient survival, graft rejection, renal protection through delayed CNI initiation, as well as other benefits. It can also help establish optimal dosing and patient criteria to maximize treatment benefits.