Optical coherence tomography for characterization of cardiac allograft vasculopathy in late survivors of pediatric heart transplantation

Influence of donor age and donor-recipient age difference on intimal hyperplasia in pediatric patients with young and adult donors vs. adult patients after heart transplantation

AIM

Optimal selection and allocation of donor hearts is a relevant aspect in transplantation medicine. Donor age and cardiac allograft vasculopathy (CAV) affect post-transplant mortality. To what extent donor age impacts intimal hyperplasia (CAVIH) in pediatric and adult patients after heart transplantation (HTx) is understudied.

METHODS

In a cohort of 98 HTx patients, 58 pediatric (24.1% with adult donors) and 40 adult patients, we assessed the effect of donor age and donor-recipient age difference (D-R) on the continuous parameter of maximal intima thickness (mIT) in optical coherence tomography. We evaluated their predictive value regarding higher mIT and the prevalence of CAVIH, defined as mIT > 0.3 mm, and compared it to established CAV risk factors.

RESULTS

In the overall population, donor age correlated with mIT (p < 0.001), while in the pediatric subpopulation, both donor age and D-R correlated with mIT (p < 0.001 and p = 0.002, respectively). In the overall population, donor age was a main predictor of higher mIT and CAVIH (p = 0.001 and p = 0.01, respectively) in addition to post-transplant interval, arterial hypertension, and dyslipidemia. In the pediatric patients, dyslipidemia remained a main predictor of both higher mIT and CAVIH (p = 0.004 and p = 0.040, respectively), while donor age and D-R were not.

CONCLUSION

While there was an effect of the non-modifiable parameter of donor age regarding maximal intimal thickness, a stronger association was seen between the modifiable risk factor dyslipidemia and higher maximal intimal thickness and CAVIH in both the overall population and the pediatric subpopulation.

Multimodality Imaging to Detect Rejection, and Cardiac Allograft Vasculopathy in Pediatric Heart Transplant Recipients—An Illustrative Review

The three most common modalities of graft surveillance in pediatric heart transplant (HT) recipients include echocardiography, coronary angiography, and endomyocardial biopsy (EMB). The survival outcomes after HT in children have improved considerably in recent years. However, allograft rejection and cardiac allograft vasculopathy remain the leading cause of death or re-transplantation. The routine surveillance by EMB and coronary angiography are invasive and risky. Newer noninvasive echocardiographic techniques, including tissue Doppler imaging (TDI), 2-D speckle tracking echocardiography, CT coronary angiography (CTCA), cardiovascular magnetic resonance (CMR), single-photon emission computed tomography (SPECT), and positron emission tomography (PET) and invasive techniques such as intravascular ultrasound (IVUS), functional flow reserve (CFR) of coronary arteries, optical coherence tomography (OCT), have emerged as powerful tools which may help early recognition of sub-clinical rejection, response to treatment, early detection, and progression of CAV. The multimodality imaging approach, including noninvasive and invasive tests, is the future for the transplanted heart to detect dysfunction, rejections, and early CAV. This review illustrates noninvasive and invasive imaging techniques currently used or could be considered for clinical use in detecting heart transplant rejection, dysfunction, and CAV in children.

Computerized Texture Analysis of Optical Coherence Tomography Angiography of Choriocapillaris in Normal Eyes of Young and Healthy Subjects

Computerized texture analysis uses higher-order mathematics to identify patterns beyond what the naked eye can recognize. We tested its feasibility in optical coherence tomography angiography imaging of choriocapillaris. Our objective was to determine sets of parameters that provide coherent and consistent output when applied to a homogeneous, healthy group of patients. This observational cross-sectional study involved 19 eyes of 10 young and healthy Caucasian subjects. En-face macular optical coherence tomography angiography of superficial choriocapillaris was obtained by the RTVue-XR Avanti system. Various algorithms were used to extract texture features. The mean and standard deviation were used to assess the distribution and dispersion of data points in each metric among eyes, which included: average gray level, gray level yielding 70% threshold and 30% threshold, balance, skewness, energy, entropy, contrast, edge mean gradient, root-mean-square variation, and first moment of power spectrum, which was compared between images, showing a highly concordant homology between all eyes of participants. We conclude that computerized texture analysis for en-face optical coherence tomography angiography images of choriocapillaris is feasible and provides values that are coherent and tightly distributed around the mean in a homogenous, healthy group of patients. Homology of blob size among subjects may represent a “repeat pattern” in signal density and thus a perfusion in the superficial choriocapillaris of healthy young individuals of the same ethnic background.

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.

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.

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.

Five decades of pediatric heart transplantation: challenges overcome, challenges remaining

PURPOSE OF REVIEW

Pediatric heart transplants continue to be the therapy of choice for children with end stage heart failure. The interplay of limited donor supply, improvement in ventricular assist device (VAD) technology and utilization, and a focus on optimizing long-term outcomes make it critically important for practitioners to be aware of an evolving diagnostic and therapeutic arsenal.

RECENT FINDINGS

Data suitable to define best practices for pediatric heart transplantation consist of an amalgam of small single center series, registry reviews and judicious inference from adult studies. Large-scale prospective pediatric studies are essentially nonexistent; the pediatric heart transplant study group continues to be highly productive while new collaboratives are emerging.

SUMMARY

Outcomes for pediatric transplants continue to improve. Technology and innovation continue to drive shifts in management. Improvements in VAD support along with refinement of solid-phase assays require clinicians to develop a deeper understanding of pre and post transplant management of donor-specific antibodies and antibody-mediated rejection. Expertise in retransplantation and the care of adults with congenital heart disease will be critical in the future.

Current state of pediatric cardiac transplantation

Pediatric heart transplantation is standard of care for children with end-stage heart failure. The diverse age range, diagnoses, and practice variations continue to challenge the development of evidence-based practices and new technologies. Outcomes in the most recent era are excellent, especially with the more widespread use of ventricular assist devices (VADs). Waitlist mortality remains high and knowledge of risk factors for death while waiting and following transplantation contributes to decision-making around transplant candidacy and timing of listing. The biggest gap impacting both waitlist and overall survival remains mechanical support options for infants and patients with single ventricle physiology. Though acute rejection has decreased progressively, both diagnosis and management of antibody-mediated rejection has become increasingly challenging and complex, as has the ability to understand the implication of anti-HLA antibodies detected both pre- and post-transplantation-including when and how to intervene. Trends in immunosuppression protocols include more use of induction therapy and steroid avoidance or withdrawal protocols. Common long-term morbidities include renal insufficiency, which can be mitigated with surveillance and renal-sparing strategies, and infections. Functional outcomes are excellent, but significant psychosocial challenges exist in relation to neurodevelopment, non-adherence, and transition from child-centered to adult-centered care. Cardiac allograft vasculopathy (CAV) remains a barrier to long-term survival, though it is more apparent that objective evidence of an impact on the allograft is important with regards to impact on outcomes. Retransplantation is rare in pediatric heart transplant recipients. Pediatric heart transplantation continues to evolve in order to address the challenges of the diverse group of patients that reach end-stage heart failure during childhood.

New developments for the detection and treatment of cardiac vasculopathy

PURPOSE OF REVIEW

Cardiac allograft vasculopathy (CAV) is a major limitation to long-term survival after heart transplantation. Innovative new techniques to diagnose CAV have been applied to detect disease. This review will examine the current diagnostic and treatment options available to clinicians for CAV.

RECENT FINDINGS

Diagnostic modalities addressing the pathophysiology underlying CAV (arterial wall thickening and decreased coronary blood flow) improve diagnostic sensitivity when compared to traditional (angiography and dobutamine stress echocardiography) techniques.

SUMMARY

Limited options are available to prevent and treat CAV; however, progress has been made in making an earlier and more accurate diagnosis. Future research is needed to identify the optimal time to modify immunosuppression and investigate novel treatments for CAV.