Chronic Respiratory Complications in Pediatric Heart Transplant Recipients

Comparing donor and recipient total cardiac volume predicts risk of short-term adverse outcomes following heart transplantation

INTRODUCTION

In pediatric heart transplantation, donor: recipient weight ratio (DRWR) has long been the sole metric for size matching. Total cardiac volume (TCV)-based size matching has emerged as a novel method to precisely identify an upper limit of donor organ size of a heart transplant recipient while minimizing the risk of complications from oversizing. The clinical adoption of donor: recipient volume ratio (DRVR) to prevent short-term adverse outcomes of oversizing is unknown. The purpose of this single-center study is to determine the relationship of DRWR and DRVR to the risk of post-operative complications from allograft oversizing.

METHODS

Recipient TCV was measured from imaging studies and donor TCV was calculated from published TCV prediction models. DRVR was defined as donor TCV divided by recipient TCV. The primary outcome was short-term post-transplant complications (SPTC), a composite outcome of delayed chest closure and prolonged intubation > 7 days. A multivariable logistic regression model of DRWR (cubic spline), DRVR (linear) and linear interaction between DRWR and DRVR was used to examine the probability of experiencing a SPTC over follow-up as a function of DRWR and DRVR.

RESULTS

A total of 106 transplant patients' records were reviewed. Risk of the SPTC increased as DRVR increased. Both low and high DRWR was associated with the SPTC. A logistic regression model including DRWR and DRVR predicted SPTC with an AUROC curve of 0.74. [95% CI 0.62 0.85]. The predictive model identified a "low-risk zone" of donor-recipient size match between a weight ratio of 0.8 and 2.0 and a TCV ratio less than 1.0.

CONCLUSION

DRVR in combination with DRWR predicts short-term post-transplant adverse events. Accepting donors with high DRWR may be safely performed when DRVR is considered.

Long-term respiratory outcomes following solid organ transplantation in children: A retrospective cohort study

BACKGROUND

Solid-organ transplantation (SOT) has become commonly used in children and is associated with excellent survival rates into adulthood. Data regarding long-term respiratory outcomes following pediatric transplantation are lacking. We aimed to describe the prevalence and nature of respiratory pathology following pediatric heart, kidney, and liver transplant, and identify potential risk factors for respiratory complications.

METHODS

Retrospective review involving all children under active follow-up at the provincial transplant service in British Columbia, Canada, following SOT.

RESULTS

Of 118 children, 33% experienced respiratory complications, increasing to 54% in heart transplant recipients. Chronic or recurrent cough with persistent chest x-ray changes was the most common clinical picture, and most infections were with nonopportunistic organisms typically found in otherwise healthy children. A history of respiratory illness before transplant was significantly associated with risk of posttransplant respiratory complications. Eight percentage8% were diagnosed with bronchiectasis, which was more common in recipients of heart and kidney transplant. Bronchiectasis was associated with recurrent hospital admissions with lower respiratory tract infections, treatment of acute rejection episodes, and treatment with sirolimus.

INTERPRETATION

Respiratory morbidity is common after pediatric SOT, and bronchiectasis rates were disproportionately high in this patient group. We hypothesize that this relates to recurrent infections resulting from iatrogenic immunosuppression. Direct pulmonary toxicity from immunosuppression drugs may also be contributory. A high index of suspicion for respiratory complications is needed following childhood SOT, particularly in those with a history of respiratory disease before transplant, experiencing recurrent or severe respiratory tract infections, or exposed to intensified immunosuppression.

Reducing the wait: TCV can expand the donor pool for heart transplant candidates

A 16-year-old with new-onset dilated cardiomyopathy underwent VAD placement, later complicated by low flow from outflow graft kinking. To expedite heart transplantation, TCV was calculated and compared with 141 normal patients pinpointing the upper weight threshold. He was transplanted 2 days later within the expanded weight range with no post-transplant complications.

Sleep-disordered breathing in pediatric heart transplant recipients

BACKGROUND

Sleep-disordered breathing is commonly found in adults with heart failure both before and after HTx. Untreated sleep-disordered breathing post-transplant has been linked to late graft dysfunction, reduced quality of life, and increased morbidity. Sleep-disordered breathing has not been investigated in pediatric HTx recipients.

METHODS

We conducted retrospective review of patients <21yo who underwent primary HTx at our center from 2009 to 2019 to describe clinical characteristics, cardiac history, and PSG results.

RESULTS

One hundred and fifty patients were included; 60% had congenital heart disease, and 40% had cardiomyopathy. Fifty patients had PSG performed at median age of 6.1 years. Forty-one were referred for symptoms of sleep-disordered breathing. Obstructive sleep apnea was diagnosed in 45 patients and central sleep apnea in 3 patients. Of those with first PSG post-transplant (n = 36), median AHI was 9.1/h, and 19 (53%) were diagnosed with moderate or severe sleep apnea. Patients diagnosed with obstructive sleep apnea on PSG had more post-transplant ventilator days (median 3 vs 2 days, P < .05) and longer post-transplant lengths of stay (median 28 vs 22 days, P < .05).

CONCLUSIONS

In this single-center cohort of pediatric HTx recipients, sleep-disordered breathing was common and associated with longer peri-transplant respiratory support and length of stay. Given the high incidence of moderate and severe OSA detected in this population, clinicians should regularly screen for SDB and consider PSG testing more frequently in children who have undergone HTx. Further study into the long-term impact of sleep-disordered breathing in pediatric HTx recipients is needed.

Sleep and the Cardiovascular System in Children

Subspecialty pediatric practice provides comprehensive medical care for a range of ages, from premature infants to children, and often includes adults with complex medical and surgical issues that warrant multidisciplinary care. Normal physiologic variations involving different body systems occur during sleep and these vary with age, stage of sleep, and underlying health conditions. This article is a concise review of the cardiovascular (CV) physiology and pathophysiology in children, sleep-disordered breathing (SDB) contributing to CV morbidity, congenital and acquired CV pathology resulting in SDB, and the relationship between SDB and CV morbidity in different clinical syndromes and systemic diseases in the expanded pediatric population.

Risk factors for specific causes of death following pediatric heart transplant: An analysis of the registry of the International Society of Heart and Lung Transplantation

We sought to determine temporal changes in COD and identify COD-specific risk factors in pediatric primary HTx recipients. Using the ISHLT registry, time-dependent hazard of death after pediatric HTx, stratified by COD, was analyzed by multiphasic parametric hazard modeling with multivariable regression models for risk factor analysis. The proportion of pediatric HTx deaths from each of cardiovascular cause, allograft vasculopathy, and malignancy increased over time, while all other COD decreased post-HTx. Pre-HTx ECMO was associated with increased risk of death from graft failure (HR 2.43; p < 0.001), infection (HR 2.85; p < 0.001), and MOF (HR 2.22; p = 0.001), while post-HTx ECMO was associated with death from cerebrovascular events/bleed (HR 2.55; p = 0.001). CHD was associated with deaths due to pulmonary causes (HR 1.78; p = 0.007) or infection (HR 1.72; p < 0.001). Non-adherence was a significant risk factor for all cardiac COD, notably graft failure (HR 1.66; p = 0.001) and rejection (HR 1.89; p < 0.001). Risk factors related to specific COD are varied across different temporal phases post-HTx. Increased understanding of these factors will assist in risk stratification, guide anticipatory clinical decisions, and potentially improve patient survival.

The successful management of respiratory complications with long-term, low-dose macrolide administration in pediatric heart transplant recipients

We report three pediatric heart transplant (HTx) patients whose respiratory symptoms were successfully controlled with long-term, low-dose macrolide administration (clarithromycin: CAM; approximately 2.5 mg/kg bid). The first case was an 18-year-old boy who underwent HTx at the age of three for dilated cardiomyopathy (DCM). Beginning at age 5, he had repeated fevers and respiratory symptoms. He was diagnosed with chronic sinusitis at age 11 and sinobronchial syndrome with mild bronchiectasis at age 14. Administration of long-term, low-dose CAM and otolaryngeal topical therapy led to significant improvement of his symptoms. The second case was a 7-year-old boy who underwent HTx for DCM at age one. Starting at age 4, he had repeated fevers and cough due to atelectasis and pneumonia. As antibiotics and respiratory physical therapy proved ineffective, he received long-term, low-dose CAM, resulting in successful control of his atelectasis and recurrent pneumonia. The third case was a 13-year-old boy who underwent HTx at age 6 for DCM. He had chronic sinusitis starting at age 7, and was diagnosed with obstructive sleep apnea syndrome at age 10. Adenotonsillectomy and continuous positive airway pressure support therapy were indicated. At age 13, long-term, lowdose CAM administration was started following mycoplasma infection. In all three cases, the levels of calcineurin inhibitors (cyclosporine and tacrolimus) and everolimus were kept in the optimal range with careful drug monitoring. Longterm, low-dose macrolide administration effectively prevents and treats respiratory complications in pediatric HTx patients as long as attention is paid to potential drug interactions.