Volumetrics and fit assessments for donor to recipient size matching in pediatric heart transplantation: Is it time for a new paradigm?

Pediatric heart transplant patients face the highest waitlist mortality in solid organ transplantation. Given the relatively fixed number of donor organs becoming available each year, improving donor organ utilization could potentially have significant impact on reducing waitlist mortality. Donor to recipient weight ratio has historically been used to identify suitable donors; however, this method does not take into account the potential for significant variance in heart size due to complex congenital heart disease or underlying cardiomyopathy. We believe, based on our experience to date, that donor matching based upon weight ratios should be augmented by improved methodologies that provide a more accurate assessment of heart volumes. Herein we describe the rationale for these methodologies and our single-center experience using volumetrics as an alternative for donor fit assessments.

Alternative methods for virtual heart transplant-Size matching for pediatric heart transplantation with and without donor medical images available.

BACKGROUND: Listed pediatric heart transplant patients have the highest solid-organ waitlist mortality rate. The donor-recipient body weight (DRBW) ratio is the clinical standard for allograft size matching but may unnecessarily limit a patient's donor pool. To overcome DRBW ratio limitations, two methods of performing virtual heart transplant fit assessments were developed that account for patient-specific nuances. Method 1 uses an allograft total cardiac volume (TCV) prediction model informed by patient data wherein a matched allograft 3-D reconstruction is selected from a virtual library for assessment. Method 2 uses donor images for a direct virtual transplant assessment. METHODS: Assessments were performed in medical image reconstruction software. The allograft model was developed using allometric/isometric scaling assumptions and cross-validation. RESULTS: The final predictive model included gender, height, and weight. The 25th-, 50th-, and 75th-percentiles for TCV percentage errors were -13% (over-prediction), -1%, and 8% (under-prediction), respectively. Two examples illustrating the potential of virtual assessments are presented. CONCLUSION: Transplant centers can apply these methods to perform their virtual assessments using existing technology. These techniques have potential to improve organ allocation. With additional experience and refinement, virtual transplants may become standard of care for determining suitability of donor organ size for an identified recipient.

Prolonged hospital length of stay after pediatric heart transplantation: A machine learning and logistic regression predictive model from the Pediatric Heart Transplant Society.

BACKGROUND: Heart transplantation (HT) is the gold standard for managing end-stage heart failure. Multiple quality metrics, including length of stay (LOS), have been used in solid organ transplantation. However, limited data are available regarding trends and factors influencing LOS after pediatric HT. We hypothesized that various donor, peri-transplant and recipient factors affect LOS after pediatric HT. METHODS: We analyzed patients <18years at time of HT from January 2005 to December 2018 in the Pediatric Heart Transplant Society database, and examined LOS trends, defined prolonged LOS (PLOS = LOS>30days after HT), identified factors associated with PLOS and assessed outcomes. RESULTS: Of 4827 patients undergoing HT, 4414 patients were discharged and included for analysis. Overall median LOS was 19days[13,34]. Median LOS was longer in patients with congenital heart disease(CHD = 25days[15,43] than with cardiomyopathy(CM = 17days[12,27] across all ages. Median LOS in age <1year was 26-days[16,45.5] and in age >10year was 16days[11,26]. PLOS was seen in 1313 patients(30%). Patients with PLOS were younger, smaller and had longer CPB times. There was no difference in utilization of VAD at HT between groups, however, ECMO use at listing(8.45% vs 2.93%,p < 0.05) and HT was higher in the PLOS group(9.22% vs 1.58%,p < 0.05). PLOS was more common in patients with previous surgery, CHD, single ventricle physiology, recipient history of cardiac arrest or CPR, end organ dysfunction, lower GFR, use of mechanical ventilation at HT and Status 1A at HT. CONCLUSION: We present novel findings of LOS distribution and define PLOS after pediatric HT, providing a quality metric for individual programs to utilize and study in their practice.

Percutaneous Closure of a "Doughnut Leak" Around an Atrial Septal Occluder Device in a Patient With Recurrent Migraines.

A 10-year-old girl with pulmonary atresia status post transannular patch repair and secundum atrial septal defect (ASD) underwent percutaneous ASD closure 5 years earlier. There was improvement in arterial saturation from 86% to 98% with minimal residual right-to-left shunt. Despite subsequent medical therapy, she developed recurrent migraines, which led us to pursue percutaneous closure of the shunt.

Hepatic Vein Incorporation Into the Azygos System in Heterotaxy and Interrupted Inferior Vena Cava.

BACKGROUND: Patients with heterotaxy, single ventricle and interrupted inferior vena cava are at risk of developing significant pulmonary arteriovenous malformations and cyanosis, and inequitable distribution of hepatic factor has been implicated in their development. We describe our experience with a technique for hepatic vein incorporation that reliably provides resolution of cyanosis and presumably equitable hepatic factor distribution. METHODS: A retrospective review of a single-surgeon experience was conducted for patients who underwent this modified Fontan operation utilizing an extracardiac conduit from the hepatic veins to the dominant superior cavopulmonary connection. Preoperative characteristics and imaging, operative details, and postoperative course and imaging were abstracted. RESULTS: Median age at operation was 5 years (2-10 years) and median weight was 19.6 kg (11.8-23 kg). Sixty percent (3/5) of patients had Fontan completion without cardiopulmonary bypass, and follow-up was complete at a median of 14 months (range 1-20 months). Systemic saturations increased significantly from 81% ± 1.9% preoperatively to 95% ± 3.5% postoperatively, P = .0008. Median length of stay was 10 days (range: 7-14 days). No deaths occurred. One patient required reoperation for bleeding and one was readmitted for pleural effusion. Postoperative imaging suggested distribution of hepatic factor to all lung segments with improved pulmonary arteriovenous malformation burden. CONCLUSIONS: Hepatic vein incorporation for patients with heterotaxy and interrupted inferior vena cava should optimally provide equitable pulmonary distribution of hepatic factor with resolution of cyanosis. The described technique is performed through a conventional approach, is facile, and improves cyanosis in these complex patients.

Improved exercise performance in pediatric heart transplant recipients after home exercise training.

Pediatric heart transplant recipients have been shown to have reduced exercise performance. Studies of adult heart transplant recipients demonstrate improved endurance from regular aerobic exercise; however, this strategy has not been studied in children. We hypothesized that regular aerobic/strength training would improve exercise performance in children post-heart transplant. After an initial training session, an exercise protocol was performed at home for 12 wk, three days/wk. Aerobic exercise consisted of either running or use of an exercise bicycle to an established target HR for >or=20 min of a 30-min session for three days/wk. Subjects wore a HR monitor and kept a diary to monitor compliance. Two days/wk, strength training was performed with elastic bands to specifically exercise biceps and triceps groups for 15-20 min/session. Aerobic exercise capacity was assessed at baseline and post-training using the standard Bruce treadmill protocol. Strength was measured at baseline and post-intervention by dynamometer. Exercise and strength parameters at baseline and post-intervention were compared using paired student t-tests. Eleven subjects completed the 12-wk program, eight females and three males. The mean age at enrollment was 14.7 +/- 5.3 yr (8-25) and mean time from transplant was 5.26 +/- 5.34 yr (0.58-14.71). Endurance time and peak oxygen consumption improved significantly post-exercise; there was no difference in peak HR or systolic blood pressure. Strength improved in the triceps, quadriceps, and biceps groups. After a 12-wk in home exercise intervention, pediatric heart recipients had improved exercise endurance and strength. The protocol was safe and implemented at relatively low cost. Further study is warranted to determine if the intervention can be extended to more children and whether benefits after such a short-term intervention can be sustained.

Therapeutic options in hypertrophic cardiomyopathy: a pediatric perspective.

Hypertrophic cardiomyopathy (HCM) is the most prevalent genetic cardiomyopathy in children and young adults. Despite advances in understanding the molecular etiology of this disorder, the clinical phenotypes vary widely from asymptomatic septal hypertrophy, to frank congestive heart failure due to left ventricular outflow tract obstruction (LVOTO), to unexpected sudden cardiac death. Thus, isolating a specific genetic defect in this disease does little to predict the clinical consequence. This is best seen in large families with several people affected by HCM who all have the identical mutation but who may have very different clinical phenotypes. Evaluating individuals with HCM consists of establishing the diagnosis through cardiac imaging, noninvasively assessing the risk for sudden death, and medically or surgically treating symptomatic LVOTO when it is present.