Greater Susceptibility for Metabolic Syndrome in Pediatric Solid Organ and Stem Cell Transplant Recipients

Obesity and metabolic syndrome in a diverse pediatric kidney transplant population: which anthropometric measure best predicts arterial stiffness?

BACKGROUND

Obesity and metabolic syndrome (MS) accelerate arterial stiffening, increasing cardiovascular (CV) risk after transplant. BMI is limited by inability to differentiate muscle, fat mass, and fat distribution patterns. The aim of this study was to identify the best anthropometric measure to detect arterial stiffness as assessed by pulse wave velocity (PWV) in a racially diverse pediatric transplant population.

METHODS

Kidney transplant recipients 6-20 years old and ≥ 6 months post-transplant were prospectively enrolled. PWV was measured oscillometrically by Mobil-O-Graph. Skeletal muscle-to-fat mass ratio (SM:FM) and percent body fat (PBF) were evaluated by dual-frequency bioelectrical impedance. BMI and waist-to-height ratio (WHR) were calculated. Associations of arterial stiffness (high PWV) with obesity and MS as defined by WHR, SM:FM, PBF, and BMI were evaluated.

RESULTS

Participants (n = 67) were 15 (IQR 11, 18) years old and 39 (IQR 10, 68) months post-transplant. Participants with SM:FM-obesity (OR 3.2) and WHR-obesity (OR 3.0) had increased odds of high PWV (p = 0.04) while PBF-obesity (OR 2.6, p = 0.09) and BMI-obesity (OR 2.2, p = 0.17) were not significant. Participants with WHR-MS (OR 12.5, p = 0.02), SM:FM-MS (OR 5.2, p = 0.03), and PBF-MS (OR 5.0, p = 0.02) had increased odds of arterial stiffness, while BMI-MS was not significant (OR 3.7, p = 0.08).

CONCLUSIONS

Obesity is associated with arterial stiffness in a racially diverse cohort of pediatric transplant recipients. Anthropometric measures that assess body fat distribution (WHR) and body composition (SM:FM) are more strongly associated with arterial stiffness than BMI. MS has a stronger association with arterial stiffness than obesity alone, particularly when WHR is used.

Cardiac Comorbidity and Exercise Intolerance in Bilateral Lung Transplant Recipients Followed at a Pediatric Center

Reduced exercise capacity is common in young bilateral lung transplantation (Bi-LTx) recipients, but longer-term data on cardiac comorbidities are limited. We evaluate potential cardiac contributions to long-term exercise intolerance in this population. All Bi-LTx recipients at a single pediatric center, who completed routine clinical post-transplant cardiac assessment, including echocardiogram, cardiac exam, and cardiopulmonary exercise testing (CPET), were included. Cardiac risk factors (CRFs) were assessed by history and laboratory tests. CPET-derived peak and percent-predicted peak myocardial oxygen consumption (VO2 peak, ppVO2 peak) were used to quantitate exercise capacity. Percent-predicted peak oxygen pulse (pp peak O2 pulse) assessed stroke volume. 15 patients (67% M; median age 21.6 years, median follow-up from Bi-LTx 7.0 years) were included. Almost all patients (14, 93%) had multiple CRFs; hypertension and hyperlipidemia/dyslipidemia were the most common. On CPET, 93% (n = 14) had abnormal (≤ 85%) ppVO2 peak (median 59%). 73% (n = 11) had abnormal pp peak O2 pulse (median 74%). Ten had blunted heart rate response to exercise. Nine had left ventricular diastolic dysfunction (LV-DD) on echocardiogram. Median percent-predicted forced expiratory volume in one second was 70%. One had severe chronic lung allograft dysfunction. Cardiac risk factors and exercise intolerance are common among young Bi-LTx recipients years post-transplant, even among those without significant pulmonary dysfunction. High prevalence of multiple CRFs, LV-DD, chronotropic dysfunction, and abnormal stroke volume suggest cardiac comorbidities may contribute to intolerance. Medical management of CRFs and tailored exercise may decrease cardiac risk and improve functional capacity for Bi-LTx survivors.

Physical activity and its impact on cardiovascular health in pediatric kidney transplant recipients

BACKGROUND

Cardiovascular (CV) morbidity after kidney transplantation (KTx) in childhood is of increasing importance. In light of a high prevalence of CV risk factors, protective measures such as physical activity (PA) come into focus. Our aim was to comprehensively assess PA in pediatric KTx recipients and evaluate its impact on CV health.

METHODS

Forty-eight patients were assessed for frequency, duration, intensity, and setting of PA using the "Motorik-Modul" PA questionnaire. Walking-based activity was measured by accelerometer in a subgroup (n = 23). CV risk factors and subclinical CV organ damage were determined. The impact of PA on CV parameters was analyzed using linear regression models.

RESULTS

Fifty-two percent of pediatric KTx recipients did not reach WHO recommended PA level; 54% did not engage in PA with vigorous intensity (VPA). Twenty-nine percent indicated an extremely inactive lifestyle (< 120 min/week of moderate to vigorous intensity PA, MVPA). Compared to the healthy German KiGGS cohort, KTx recipients specifically lacked engagement in sport activities (KTx: 129 min/week; 95%CI, 97-162 vs. KiGGS, 242 min/week; 95%CI, 230-253). VPA was associated with lower systolic blood pressure (p = 0.024) and resting heart rate (p = 0.005), MVPA with fewer components of the post-transplant metabolic syndrome (p = 0.037), and better left ventricular diastolic function (p = 0.006).

CONCLUSIONS

A considerable lack of PA, especially VPA, exists in young KTx recipients. PA was positively associated with important parameters of CV health. While long-term CV protection through PA seems promising in pediatric KTx recipients, specific educational approaches are most likely needed to increase patients' engagement in sport activities.

Hypertension in Pediatric Solid Organ Transplant Recipients

PURPOSE OF REVIEW

To review the current literature regarding hypertension (HTN) following pediatric solid organ transplant (SOTx), including definition, prevalence, risk factors, outcomes, and treatment.

RECENT FINDINGS

In recent years several new guidelines for the definition, monitoring, and management of pediatric HTN have been published, but with no specific recommendations regarding SOTx recipients. HTN remains highly prevalent, yet underdiagnosed and undertreated in kidney transplant (KTx) recipients, especially when ambulatory blood pressure monitoring (ABPM) is utilized. There are little data regarding its prevalence in other SOTx recipients. HTN in this population is multifactorial and is associated with HTN status prior to Tx, demographic factors (age, sex, and race), weight status, and immunosuppression protocol. HTN is associated with subclinical cardiovascular (CV) end-organ damage, including left ventricular hypertrophy (LVH) and arterial stiffness, yet there are no recent data regarding its long-term outcomes. There are also no updated recommendations regarding the optimal management of HTN in this population. Given its high prevalence and the young age of this population facing years at increased CV risk, post-Tx HTN requires more clinical attention (routine monitoring, frequent application of ABPM, better BP control). Additional research is needed for a better understanding of its long-term outcomes as well as its treatment and treatment goals. Much more research is needed regarding HTN in other pediatric SOTx populations.

Incidence of cardiovascular disease and mortality in childhood solid organ transplant recipients: a population-based study

BACKGROUND

With improved survival among children after transplantation, our understanding of the risk for developing other comorbidities is improving, yet little is known about the long-term risk of cardiovascular events and mortality after solid organ transplantation.

METHODS

In a cohort study using health administrative data, we compared cardiovascular events in children (n = 615) with liver, lung, kidney, small bowel, or multi-organ transplant at the Hospital for Sick Children, Toronto, Canada, with asthmatic children (n = 481,697) between 1996 and 2014. Outcomes included non-fatal cardiovascular events, cardiovascular death, all-cause mortality, and a composite of non-fatal and fatal cardiovascular events. Time-stratified Cox proportional hazards models were used.

RESULTS

Among 615 children, 317 (52%) were recipients of kidneys, 253 (41%) of livers, and the remaining 45 (7%) had lung, small bowel, or multi-organ transplants. Median follow-up was 12.1 [7.2, 16.7] years. Non-fatal incident cardiovascular events were 34 times higher among solid organ transplant recipients than non-transplanted children (incidence rate ratio (IRR) 34.4, 95% CI: 25.5, 46.4). Among transplant recipients, the cumulative incidence of non-fatal and fatal cardiovascular events was 2.3% and 13.0%, 5 and 15 years after transplantation, respectively.

CONCLUSIONS

Increased rate of cardiovascular events in children after transplantation highlights the need for surveillance during transition into adulthood and beyond. A higher resolution version of the Graphical abstract is available as Supplementary information.

Arterial stiffness and blood pressure increase in pediatric kidney transplant recipients

BACKGROUND

Pulse wave velocity (PWV) is a measure of arterial stiffness. We investigated PWV and blood pressure (BP) to determine to what extent BP changes contribute to arterial stiffness, and secondly, to identify influencing factors on BP in children after kidney transplantation.

METHODS

Seventy children ≥ 2.5 years post-transplantation with at least two PWV measurements were included. Changes of systolic (Δ SBP) and diastolic BP (Δ DBP) were classified into "stable/decreasing," "1-10 mmHg increase," and " > 10 mmHg increase." Linear mixed modeling for PWV z-score (PWVz) adjusted either for Δ SBP or Δ DBP was performed. An extended dataset with monthly entries of BP, immunosuppression, and creatinine was obtained in 35 participants over a median of 74 months to perform linear mixed modeling for SBP and DBP.

RESULTS

PWVz increased with a rate of 0.11/year (95% CI 0.054 to 0.16). Compared to participants with stable BP, those with 1-10-mmHg SBP and DBP increase showed a higher PWVz of 0.59 (95% CI 0.046 to 1.13) and 0.86 (95% CI 0.43 to 1.30), respectively. A > 10-mmHg BP increase was associated with an even higher PWVz (SBP β = 0.78, 95% CI 0.22 to 1.34; DBP β = 1.37, 95% CI 0.80 to 1.94). Female sex and participants with lower eGFR showed higher PWVz. In the extended analysis, DBP was positively associated with cyclosporin A and everolimus trough levels.

CONCLUSIONS

A higher increase of PWV is seen in patients with greater BP increase, with higher cyclosporin A and everolimus trough levels associated with higher BP. This emphasizes the role of BP as a modifiable risk factor for the improvement of cardiovascular outcome after transplantation. A higher resolution version of the Graphical abstract is available as Supplementary information.

Telomere length is associated with intima-media thickness in pediatric liver transplant patients: A prospective cohort study

Leukocyte telomere length (LTL) is a marker for biological age. Pediatric liver transplant recipients show a high rate of subclinical atherosclerosis, indicated by elevated intima-media thickness (IMT). We hypothesized that atherosclerosis is associated with biological age in these patients and investigated the course of LTL over time. We measured LTL from peripheral blood leukocytes by quantitative polymerase chain reaction and IMT from 97 pediatric patients after liver transplantation in a prospective cohort study. Of the patients, 71% (n = 69) had two or more assessments (total, 228 observations; median follow-up, 1.1 years). Lower LTL was associated with higher IMT (β = -0.701, p = 0.01) and higher aspartate aminotransferase (β = -0.001, p = 0.02), adjusted for age, sex, and age at transplantation. Of the patients, 45% showed decreasing LTL over time, whereas 55% exhibited stable LTL. Patients with stable LTL showed a decrease in IMT (median, -0.02 mm/year) and a decrease of tacrolimus trough levels (median, -0.08 μg/L/year). LTL is associated with IMT independent of age in pediatric liver transplant patients, suggesting that early aging contributes to the high burden of subclinical cardiovascular damage and may furthermore negatively affect the graft.

Cardiovascular Burden Is High in Pediatric Lung Transplant Recipients

BACKGROUND

Cardiovascular morbidity is common in adults after lung transplantation (LTx) but has not been described for pediatric LTx recipients. Early subclinical cardiovascular damage is reflected by increases in pulse wave velocity (PWV; indicating arteriosclerosis), intima-media thickness (IMT; indicating atherosclerosis), and left ventricular mass index (LVMI; indicating left ventricular hypertrophy).

METHODS

We annually assessed 47 pediatric LTx recipients in a prospective longitudinal study (144 observations, mean 3.1 visits/patient, range of 1-4 visits, mean follow-up 2.2 y).

RESULTS

At inclusion, increased PWV and IMT were detected in 13% and 30%, respectively, and elevated LVMI was detected in 33%. Higher PWV was associated with male sex, longer time since LTx, higher diastolic blood pressure, and lower glomerular filtration rate. Male sex and lower hemoglobin levels were associated with higher IMT, and the presence of diabetes was associated with higher LVMI.

CONCLUSIONS

Pediatric LTx recipients suffer from a high and sustained burden of subclinical cardiovascular damage. In light of improving long-term outcomes, cardiovascular morbidity needs to be addressed. Our analysis identified classical and nonclassical risk factors to be associated with the measures for cardiovascular damage, which could serve as targets for intervention.

Parental Disease Specific Knowledge and Its Impact on Health-Related Quality of Life

OBJECTIVE

Structured education programs have been shown to improve somatic outcome and health-related quality of life (HRQOL) in a variety of chronic childhood diseases. Similar data are scarce in paediatric liver transplantation (pLTx). The purpose of this study was to examine the relationship of parental disease-specific knowledge and psychosocial disease outcome in patients after pLTx.

METHODS

Parents of 113 children (chronic liver disease n = 25, after pLTx n = 88) completed the transplant module of the HRQOL questionnaire PedsQL, the "Ulm quality of life inventory for parents of children with chronic diseases" ULQUI, and a tailor-made questionnaire to test disease-specific knowledge.

RESULTS

Parental knowledge was highest on the topic of "liver transplantation" and lowest in "basic background knowledge" (76% and 56% correct answers respectively). Knowledge performance was only marginally associated with HRQOL scores, with better knowledge being related to worse HRQOL outcomes. In contrast, self-estimation of knowledge performance showed significant positive correlations with both PedsQL and ULQUI results.

CONCLUSION

Patient HRQOL and parental emotional wellbeing after pLTx are associated with positive self-estimation of parental disease-specific knowledge. Objective disease-specific knowledge has little impact on HRQOL. Parental education programs need to overcome language barriers and address self-efficacy in order to improve HRQOL after pLTx.

School and sports participation post-transplant

Pediatric recipients of life-saving organ transplants are living longer, with improved graft and overall survivals. After successful transplant, children are encouraged to return to "normal life," with school attendance and participation in age-appropriate physical activities. This transition may cause stress to the recipients, parents, teachers, and other participating caregivers and staff. Planning for school reentry and assuring education for and open lines of communication with the school staff can help alleviate some of this discomfort and ease the process for the patient and the family. Cardiovascular disease has emerged as the leading cause of death in survivors of pediatric transplantation and is contributed to by modifiable risk factors such as obesity, hypertension, and the MS. Physical activity is a proven tool in decreasing surrogate markers of this risk. Sports participation is an important way to promote an enjoyment of physical activity that can ideally persist into adulthood, but conflicting advice and opinions exist regarding type and participation in physical activity. Moreover, specific recommendations are likely not applicable to all recipients, as certain degrees of rehabilitation may be needed depending on degree and length of illness. In general, a program of rehabilitation and increased physical activity has been shown to be safe and effective for most pediatric transplant recipients. Focusing on optimizing the "normal" childhood activities of going to school and participating in sports can improve the physical, social, cognitive, and mental health outcomes of this population after transplant and should be prioritized.