Responses of normal children and young adults to controlled bicycle exercise

Brazilian Guideline for Exercise Testing in Children and Adolescents - 2024

CLASSES OF RECOMMENDATION

LEVELS OF EVIDENCE

Peak Oxygen Consumption (V̇O 2peak ) Recovery Delay in a Pediatric Fontan Population

PURPOSE

The purpose of this study is to identify predictors and correlates of VO2RD in youth with Fontan.

METHODS

Cardiopulmonary exercise test data was used from a single center, cross-sectional study of children and adolescents (age, 8-21 yr) with Fontan physiology. The VO2RD was determined using time (s) to <90% of V̇O 2peak and categorized as "low" (≤10 s) or "high" (≥10 s). t Tests and χ 2 analysis were used to compare continuous and categorical variables, respectively.

RESULTS

The analysis sample included 30 adolescents with Fontan physiology (age, 14.2 ± 2.4 yr; 67% male) with either right ventricular (RV) dominant (40%) or co/left ventricular (Co/LV) dominant (60%) systemic ventricular morphology. There were no differences in V̇O 2peak between the high and low VO2RD groups (high = 1.3 ± 0.4 L·min -1 ; low = 1.3 ± 0.3 L·min -1 ; P = 0.97). VO2RD in participants with RV dominance was significantly greater than in patients with Co/LV dominance (RV = 23.8 ± 15.8 s; Co/LV = 11.8 ± 16.1 s; P = 0.03).

CONCLUSIONS

V̇O 2peak was not correlated with VO2RD when analyzed as high/low VO2RD groups. However, morphology of the systemic single ventricle (RV vs Co/LV) may be related to rate of recovery in V̇O 2 after a peak cardiopulmonary exercise test.

Moderators of peak respiratory exchange ratio during exercise testing in children and adolescents with Fontan physiology

OBJECTIVES

Many patients with Fontan physiology are unable to achieve the minimum criteria for peak effort during cardiopulmonary exercise testing. The purpose of this study is to determine the influence of physical activity and other clinical predictors related to achieving peak exercise criteria, signified by respiratory exchange ratio ≥ 1.1 in youth with Fontan physiology.

METHODS

Secondary analysis of a cross-sectional study of 8-18-year-olds with single ventricle post-Fontan palliation who underwent cardiopulmonary exercise testing (James cycle protocol) and completed a past-year physical activity survey. Bivariate associations were assessed by Wilcoxon rank-sum test and simple regression. Conditional inference forest algorithm was used to classify participants achieving respiratory exchange ratio > 1.1 and to predict peak respiratory exchange ratio.

RESULTS

Of the n = 43 participants, 65% were male, mean age was 14.0 ± 2.4 years, and 67.4% (n = 29) achieved respiratory exchange ratio ≥ 1.1. Despite some cardiopulmonary exercise stress test variables achieving statistical significance in bivariate associations with participants achieving respiratory exchange ratio > 1.1, the classification accuracy had area under the precision recall curve of 0.55. All variables together explained 21.4% of the variance in respiratory exchange ratio, with peak oxygen pulse being the most informative.

CONCLUSION

Demographic, physical activity, and cardiopulmonary exercise test measures could not classify meeting peak exercise criteria (respiratory exchange ratio ≥ 1.1) at a satisfactory accuracy. Correlations between respiratory exchange ratio and oxygen pulse suggest the augmentation of stroke volume with exercise may affect the Fontan patient's ability to sustain high-intensity exercise.

Single ventricular strain measures correlate with peak oxygen consumption in children and adolescents with Fontan circulation

INTRODUCTION

Children with a single ventricle post-Fontan palliation are at increased risk of poor outcomes with peak oxygen consumption acting as a surrogate outcome marker. The purpose of this study is to evaluate the relationship between peak oxygen consumption and echocardiographic measures of ventricular function and deformation, including ventricular global longitudinal strain and dyssynchrony, in children and adolescents following Fontan palliation.

METHODS

Patients (age 8-21 years) with single ventricle post-Fontan palliation were prospectively recruited and participated in an echocardiogram, including views optimised for two-dimensional speckle tracking, and a cardiopulmonary exercise test on a cycle ergometer to maximal volitional fatigue.

RESULTS

Thirty-eight patients (mean age 13.7 ± 2.3 years) post-Fontan palliation had either a single left ventricular (n = 20), single right ventricular (n = 14), or biventricular (n = 4) morphology. Peak oxygen consumption (24.9 ± 5.6 ml/kg/minute) was correlated with global longitudinal strain (r = -0.435, p = 0.007), a strain discoordination time to peak index (r = -0.48, p = 0.003), and the presence of an electro-mechanical dyssynchrony strain pattern (p = 0.008). On multivariate regression modelling, these three variables were associated with peak oxygen consumption independently of age and sex. The single right ventricular group had evidence of possible diastolic dysfunction by E/e' compared to the single left ventricular and biventricular groups (p = 0.001).

CONCLUSIONS

Strain analysis measures are correlated with peak oxygen consumption in this cohort of children, adolescents, and young adults following Fontan palliation, suggesting that ventricular mechanics may influence the efficiency of the Fontan circulation.

Case report: A proposed role for cardiopulmonary exercise testing in detecting cardiac dysfunction in asymptomatic at-risk adolescents

Noninvasive cardiopulmonary exercise testing (CPET) provides the valuable capacity to analyze pulmonary gas exchange and cardiovascular responses that can be used to differentiate normal cardiopulmonary responses from abnormal. This case report highlights a proposed role for CPET in identifying potential cardiac pathologies in at-risk adolescents. An abnormal CPET response in an asymptomatic adolescent revealed a family history of early-age CAD. The significance of the abnormal CPET response was further supported by the presence of an elevated concentration of circulating high sensitivity C-reactive protein (hs-CRP). These findings emphasize the importance of a thorough clinical evaluation in at-risk adolescents, as CPET can aid in the early detection and management of cardiac pathologies, especially when combined with other relevant biomarkers such as plasma hs-CRP concentration, which can further suggest underlying pathology. Management considerations using serial CPET evaluations are recommended. Thus, CPET abnormalities combined with elevated hs-CRP should be taken seriously and provide justification for further evaluation and monitoring in adolescents at risk for cardiovascular disease.

Performing moderate to severe activity is safe and tolerable for healthy youth while wearing a cloth facemask

OBJECTIVE

To investigate if a cloth facemask could affect physiological and perceptual responses to exercise at distinct exercise intensities in healthy young individuals.

METHODS

Nine participants (sex, female/male: 6/3; age: 13±1 years; VO2peak: 44.5±5.5 mL/kg/min) underwent a progressive square-wave test at four intensities: (1) 80% of ventilatory anaerobic threshold (VAT), (2) VAT, and (3) 40% between VAT and [Formula: see text] wearing a triple-layered cloth facemask or not. Participants then completed a final stage to exhaustion at a running speed equivalent to the maximum achieved during the cardio-respiratory exercise test (Peak). Physiological, metabolic, and perceptual measures were measured.

RESULTS

Mask did not affect spirometry (forced vital capacity, peak expiratory flow, forced expiratory volume; all p≥0.27), respiratory (inspiratory capacity, end-expiratory volume [EELV] to functional vital capacity ratio, EELV, respiratory frequency [Rf], tidal volume [VT], Rf/VT, end-tidal carbo dioxide pressure, ventilatory equivalent to carbon dioxide ratio; all p≥0.196), hemodynamic (heart rate, systolic and diastolic blood pressure; all p>0.41), ratings of perceived exertion (p = 0.04) or metabolic measures (lactate; p = 0.78) at rest or at any exercise intensity.

CONCLUSIONS

This study shows that performing moderate to severe activity is safe and tolerable for healthy youth while wearing a cloth facemask.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT04887714.

Altered hemodynamics by 4D flow cardiovascular magnetic resonance predict exercise intolerance in repaired coarctation of the aorta: an in vitro study

BACKGROUND

Coarctation of the aorta (CoA) is associated with decreased exercise capacity despite successful repair. Altered flow patterns have been identified due to abnormal aortic arch geometry. Our previous work demonstrated aorta size mismatch to be associated with exercise intolerance in this population. In this study, we studied aortic flow patterns during simulations of exercise in repaired CoA using 4D flow cardiovascular magnetic resonance (CMR) using aortic replicas connected to an in vitro flow pump and correlated findings with exercise stress test results to identify biomarkers of exercise intolerance.

METHODS

Patients with CoA repair were retrospectively analyzed after CMR and exercise stress test. Each aorta was manually segmented and 3D printed. Pressure gradient measurements from ascending aorta (AAo) to descending aorta (DAo) and 4D flow CMR were performed during simulations of rest and exercise using a mock circulatory flow loop. Changes in wall shear stress (WSS) and secondary flow formation (vorticity and helicity) from rest to exercise were quantified, as well as estimated DAo Reynolds number. Parameters were correlated with percent predicted peak oxygen consumption (VO2max) and aorta size mismatch (DAAo/DDAo).

RESULTS

Fifteen patients were identified (VO2max 47 to 126% predicted). Pressure gradient did not correlate with VO2max at rest or exercise. VO2max correlated positively with the change in peak vorticity (R = 0.55, p = 0.03), peak helicity (R = 0.54, p = 0.04), peak WSS in the AAo (R = 0.68, p = 0.005) and negatively with peak WSS in the DAo (R = - 0.57, p = 0.03) from rest to exercise. DAAo/DDAo correlated strongly with change in vorticity (R = - 0.38, p = 0.01), helicity (R = - 0.66, p = 0.007), and WSS in the AAo (R = - 0.73, p = 0.002) and DAo (R = 0.58, p = 0.02). Estimated DAo Reynolds number negatively correlated with VO2max for exercise (R = - 0.59, p = 0.02), but not rest (R = - 0.28, p = 0.31). Visualization of streamline patterns demonstrated more secondary flow formation in aortic arches with better exercise capacity, larger DAo, and lower Reynolds number.

CONCLUSIONS

There are important associations between secondary flow characteristics and exercise capacity in repaired CoA that are not captured by traditional pressure gradient, likely due to increased turbulence and inefficient flow. These 4D flow CMR parameters are a target of investigation to identify optimal aortic arch geometry and improve long term clinical outcomes after CoA repair.

Aorta size mismatch predicts decreased exercise capacity in patients with successfully repaired coarctation of the aorta

OBJECTIVE

Coarctation of the aorta (CoA) is associated with decreased exercise capacity despite successful repair with no residual stenosis; however, the hemodynamic mechanism remains unknown. This study aims to correlate aortic arch geometry with exercise capacity in patients with successfully repaired CoA and explain hemodynamic changes using 3-dimensional-printed aorta models in a mock circulatory flow loop.

METHODS

A retrospective chart review identified patients with CoA repair who had cardiac magnetic resonance imaging and an exercise stress test. Measurements included aorta diameters, arch height to diameter ratio, left ventricular function, and percent descending aorta (%DAo) flow. Each aorta was printed 3-dimensionally for the flow loop. Flow and pressure were measured at the ascending aorta (AAo) and DAo during simulated rest and exercise. Measurements were correlated with percent predicted peak oxygen consumption (VO2 max).

RESULTS

Fifteen patients (mean age 26.8 ± 8.6 years) had a VO2 max between 47% and 126% predicted (mean 92 ± 20%) with normal left ventricular function. DAo diameter and %DAo flow positively correlated with VO2 (P = .007 and P = .04, respectively). AAo to DAo diameter ratio (DAAo/DDAo) negatively correlated with VO2 (P < .001). From flow loop simulations, the ratio of %DAo flow in exercise to rest negatively correlated with VO2 (P = .02) and positively correlated with DAAo/DDAo (P < .01).

CONCLUSIONS

This study suggests aorta size mismatch (DAAo/DDAo) is a novel, clinically important measurement predicting exercise capacity in patients with successful CoA repair, likely due to increased resistance and altered flow distribution. Aorta size mismatch and %DAo flow are targets for further clinical evaluation in repaired CoA.

Functional Capacity Is Affected by Younger Age of Repair in Tetralogy of Fallot Patients But Not by Era of Repair

Background:

Cardiopulmonary exercise testing is widely used to assess functional capacity in patients with tetralogy of Fallot after surgical repair. Little is known regarding the impact of age at the time of primary complete repair and surgical era effect on exercise capacity.

Methods:

A retrospective, single-center chart review was done from 1976 to 2016 on pediatric patients with tetralogy of Fallot who underwent cardiopulmonary exercise testing with cycle ergometry utilizing the James protocol and were then sorted by repair before/after 1990 and by age of complete repair before/after one year. Exclusion criteria included submaximal tests, incomplete data, previous pulmonary valve replacement, and surgery prior to complete repair (ie, Blalock-Taussig shunt placement).

Results:

When comparing the groups who underwent primary complete repair before (N = 39) and after (N = 26) one year of age, the younger group demonstrated a higher percentage of predicted peak oxygen consumption ([Formula: see text] o2peak; 83.1% ± 11.8% vs 73.1% ± 16.1%; P = .005) despite having worse pulmonary insufficiency at the time of exercise testing. There were no differences in heart rate and blood pressure response. Age of repair was independently associated with [Formula: see text] o2peak. Data were statistically similar to the study eras (repair before 1990, N = 23; repair after 1990, N = 65): percentage of predicted [Formula: see text] o2peak (81.4% ± 13.6% vs 79.1% ± 14.4%, P = .5), maximal systolic blood pressure (155.1 ± 22.4 mm Hg vs 153.9 ± 17 mm Hg, P = .8), and percentage of predicted maximal heart rate (89.8% ± 9% vs 92% ± 7.1%, P = .3).

Conclusions:

Older age at primary repair appears to negatively impact [Formula: see text] o2peak; however, era effect does not appear to influence cardiopulmonary exercise testing outcomes.

Measurement and Interpretation of Maximal Aerobic Power in Children

The assessment of maximal aerobic power ( V˙O2max ) in both children and adults is an invaluable tool for the evaluation of exercise performance capacity and general physical fitness in clinical, athletic, public health, and research applications. The complexity of means and considerations, as well as varying specific aims of V˙O2max testing, has prevented the formulation of a universally applicable, standard testing protocol, in general, and for children in particular. Numerous tester-controllable factors, such as exercise modality, metabolic measurement system, testing protocol, or data reduction strategies, can affect both the measurement and interpretation of V˙O2max data. Although the general guiding principles are similar, children differ from adults in several aspects. One notable difference is the frequent absence of a discernible V˙O2 plateau in children. Thus, the proper choice of equipment and procedures may be different for children than for adults. It is therefore the aim of this article to highlight the general and pediatric-specific considerations that may affect V˙O2max measurement and interpretation of results.

Cognitive Performance, Aerobic Fitness, Motor Proficiency, and Brain Function Among Children Newly Diagnosed With Craniopharyngioma

OBJECTIVES

Craniopharyngioma survivors experience cognitive deficits that negatively impact quality of life. Aerobic fitness is associated with cognitive benefits in typically developing children and physical exercise promotes recovery following brain injury. Accordingly, we investigated cognitive and neural correlates of aerobic fitness in a sample of craniopharyngioma patients.

METHODS

Patients treated for craniopharyngioma [N=104, 10.0±4.6 years, 48% male] participated in fitness, cognitive and fMRI (n=51) assessments following surgery but before proton radiation therapy.

RESULTS

Patients demonstrated impaired aerobic fitness [peak oxygen uptake (PKVO2)=23.9±7.1, 41% impaired (i.e., 1.5 SD&lt;normative mean)], motor proficiency [Bruininks-Oseretsky (BOT2)=38.6±9.0, 28% impaired], and executive functions (e.g., WISC-IV Working Memory Index (WMI)=96.0±15.3, 11% impaired). PKVO2 correlated with better executive functions (e.g., WISC-IV WMI r=.27, p=.02) and academic performance (WJ-III Calculation r=.24, p=.04). BOT2 correlated with better attention (e.g., CPT-II omissions r=.26, p=.04) and executive functions (e.g., WISC-IV WMI r=.32, p=.01). Areas of robust neural activation during an n-back task included superior parietal lobule, dorsolateral prefrontal cortex, and middle and superior frontal gyri (p&lt;.05, corrected). Higher network activation was associated with better working memory task performance and better BOT2 (p&lt;.001).

CONCLUSIONS

Before adjuvant therapy, children with craniopharyngioma demonstrate significantly reduced aerobic fitness, motor proficiency, and working memory. Better aerobic fitness and motor proficiency are associated with better attention and executive functions, as well as greater activation of a well-established working memory network. These findings may help explain differential risk/resiliency with respect to acute cognitive changes that may portend cognitive late effects. (JINS, 2019, 25, 413-425).

Cardiopulmonary Aerobic Fitness Assessment During Maximal and Submaximal Exercise Testing in Pediatric Oncology Patients After Chemotherapy

PURPOSE

The cardiopulmonary exercise test (CPET) is a valuable tool to assess cardiopulmonary exercise capacity in pediatric oncology patients after chemotherapy. In addition, few studies on the utility of submaximal testing have been performed, which could be important as some patients are unable to complete a maximal effort test secondary to deconditioning by both disease and treatment.

MATERIALS AND METHODS

We performed a retrospective chart review of pediatric cancer patients exposed to chemotherapy from 1992 to 2013 who underwent CPET with cycle ergometry (n=27). The study patients were compared with age-matched, sex-matched, and size-matched normal controls. The submaximal measure recorded was the oxygen consumption (VO2)@respiratory exchange ratio (RER) 1.0 during a maximal effort test.

RESULTS

The chemotherapy group demonstrated significantly lower exercise time (9.2±3.6 vs. 11.4±3.8; P=0.008), total work capacity (4914.4±3290.3 vs. 7664.4±4289.5; P=0.004), systolic blood pressure at peak exercise (162.9±23.2 vs. 177.3±23.8; P=0.01), indexed peak VO2 (33.9±6.9 vs. 40.0±6.3; P=0.001), and indexed peak oxygen pulse (6.1±1.3 vs. 7.0±1.5; P=0.004)). For the submaximal outcome measured, 11/27 of the chemotherapy patients had VO2@RER 1.0 values <-2 SD from the mean compared with 0/27 control patients.

CONCLUSIONS

Pediatric patients exposed to chemotherapy have impaired cardiopulmonary exercise capacity. The VO2@RER 1.0 in chemotherapy patients suggests that this may be a reliable submaximal measure in this population.

IMPLICATIONS FOR CANCER SURVIVORS

This study demonstrates that the CPET can be used in pediatric cancer survivors with prior exposure to chemotherapy to demonstrate impaired cardiopulmonary exercise tolerance, which is demonstrated on submaximal and maximal effort testing.

Cardiorespiratory and metabolic responses to body mass-based squat exercise in young men

Background

The purpose of this study was to quantify cardiorespiratory and metabolic responses to body mass-based squat exercise, with specific emphasis on the relationships with the exercise duration.

Methods

Fifteen healthy young men performed body mass-based squat exercise as well as an incremental loaded bicycle test, which determine maximal oxygen uptake and maximal heart rate, with an interval of 2 days between the tests. During both tasks, oxygen uptake, blood lactate concentration (BLa), and heart rate (HR) were determined. Oxygen uptake in both tasks was divided by body mass (VO₂). VO₂ in the squat task was normalized to VO₂ in the incremental test (%VO₂max). In addition, electromyograms (EMGs) were also recorded from the vastus lateralis, rectus femoris, vastus medialis, biceps femoris, and gluteus maximus.

Results

Cardiorespiratory parameters and BLa did not change after 5 min from the exercise onset. The %VO₂max and BLa during body mass-based squat exercise were significantly related to maximal VO₂ obtained by the incremental test. Metabolic equivalents reached 6.5 when the squat exercise was continuously performed for 5 min.

Conclusions

These findings indicate that (1) the squat exercise adopted here is of moderate intensity and predominantly uses aerobic energy supply after 5 min from the start of the exercise and (2) relative intensity during the exercise depends on an individual’s maximal aerobic power.

A human pluripotent stem cell model of catecholaminergic polymorphic ventricular tachycardia recapitulates patient-specific drug responses

Although β-blockers can be used to eliminate stress-induced ventricular arrhythmias in patients with catecholaminergic polymorphic ventricular tachycardia (CPVT), this treatment is unsuccessful in ∼25% of cases. Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) generated from these patients have potential for use in investigating the phenomenon, but it remains unknown whether they can recapitulate patient-specific drug responses to β-blockers. This study assessed whether the inadequacy of β-blocker therapy in an individual can be observed in vitro using patient-derived CPVT iPSC-CMs. An individual with CPVT harboring a novel mutation in the type 2 cardiac ryanodine receptor (RyR2) was identified whose persistent ventricular arrhythmias during β-blockade with nadolol were abolished during flecainide treatment. iPSC-CMs generated from this patient and two control individuals expressed comparable levels of excitation-contraction genes, but assessment of the sarcoplasmic reticulum Ca(2+) leak and load relationship revealed intracellular Ca(2+) homeostasis was altered in the CPVT iPSC-CMs. β-adrenergic stimulation potentiated spontaneous Ca(2+) waves and unduly frequent, large and prolonged Ca(2+) sparks in CPVT compared with control iPSC-CMs, validating the disease phenotype. Pursuant to the patient's in vivo responses, nadolol treatment during β-adrenergic stimulation achieved negligible reduction of Ca(2+) wave frequency and failed to rescue Ca(2+) spark defects in CPVT iPSC-CMs. In contrast, flecainide reduced both frequency and amplitude of Ca(2+) waves and restored the frequency, width and duration of Ca(2+) sparks to baseline levels. By recapitulating the improved response of an individual with CPVT to flecainide compared with β-blocker therapy in vitro, these data provide new evidence that iPSC-CMs can capture basic components of patient-specific drug responses.

Estimating equations for cardiopulmonary exercise testing variables in Fontan patients: derivation and validation using a multicenter cross-sectional database

Cardiopulmonary exercise testing (CPET) is a common method of evaluating patients with a Fontan circulation. Equations to calculate predicted CPET values are based on children with normal circulation. This study aims to create predictive equations for CPET variables solely based on patients with Fontan circulation. Patients who performed CPET in the multicenter Pediatric Heart Network Fontan Cross-Sectional Study were screened. Peak variable equations were calculated using patients who performed a maximal test (RER > 1.1) and anaerobic threshold (AT) variable equations on patients where AT was adequately calculated. Eighty percent of each cohort was randomly selected to derive the predictive equation and the remaining served as a validation cohort. Linear regression analysis was performed for each CPET variable within the derivation cohort. The resulting equations were applied to calculate predicted values in the validation cohort. Observed versus predicted variables were compared in the validation cohort using linear regression. 411 patients underwent CPET, 166 performed maximal exercise tests and 317 had adequately calculated AT. Predictive equations for peak CPET variables had good performance; peak VO2, R (2) = 0.61; maximum work, R (2) = 0.61; maximum O2 pulse, R (2) = 0.59. The equations for CPET variables at AT explained less of the variability; VO2 at AT, R (2) = 0.15; work at AT, R (2) = 0.39; O2 pulse at AT, R (2) = 0.34; VE/VCO2 at AT, R (2) = 0.18; VE/VO2 at AT, R (2) = 0.14. Only the models for VE/VCO2 and VE/VO2 at AT had significantly worse performance in validation cohort. Of the 8 equations for commonly measured CPET variables, six were able to be validated. The equations for peak variables were more robust in explaining variation in values than AT equations.

Dealing with Ebstein's anomaly

Ebstein's anomaly is a complex congenital disorder of the tricuspid valve. Presentation in neonatal life and (early) childhood is common. Disease severity and clinical features vary widely and require a patient-tailored treatment. In this review, we describe the natural history of children and adolescents with Ebstein's anomaly, including symptoms and signs presenting at diagnosis. Current classification strategies of Ebstein's anomaly are discussed. We report on diagnostic methods for establishing the severity of disease that might enhance decision on the timing of surgical intervention. Furthermore, we describe different surgical options for severely ill neonates and multiple surgical interventions after infancy. Only with ample knowledge and understanding of the above, this complex and diverse group of patients can be correctly treated in order to improve not only duration, but also quality of life.

The effect of childhood obesity on cardiac functions

Obesity is a metabolic disorder defined as excessive accumulation of body fat, which is made up of genetic, environmental, and hormonal factors and has various social, psychological, and medical complications. Childhood obesity is a major indicator of adult obesity. The aim of this study is to evaluate the cardiac functions via electrocardiography (ECG), echocardiography (ECHO), and treadmill test in childhood obesity. A patient group consisting of 30 obese children and a control group consisting of 30 non-obese children were included in the study. The age range was between 8 and 17 years. Anthropometric measurements, physical examination, ECG, ECHO, and treadmill test were done in all patients. P-wave dispersion (PD) was found to be statistically significantly high in obese patients. In ECHO analysis, we found that end-diastolic diameter, end-systolic diameter, left ventricle posterior wall thickness, and interventricular septum were significantly greater in obese children. In treadmill test, exercise capacity was found to be significantly lower and the hemodynamic response to exercise was found to be defective in obese children. Various cardiac structural and functional changes occur in childhood obesity and this condition includes important cardiovascular risks. PD, left ventricle end-systolic and end-diastolic diameter, left ventricle posterior wall thickness, interventricular septum thickness, exercise capacity, and hemodynamic and ECG measurements during exercise testing are useful tests to determine cardiac dysfunctions and potential arrhythmias even in early stages of childhood obesity. Early recognition and taking precautions for obesity during childhood is very important to intercept complications that will occur in adulthood.

Cardiovascular fitness and haemodynamic responses to maximal cycle ergometer exercise test in children 6-8 years of age

We investigated cardiovascular fitness and haemodynamic responses to maximal cycle ergometer exercise test in children. The participants were a population sample of 425 children (204 girls, 221 boys) aged 6-8 years. Heart rate (HR) and systolic blood pressure (SBP) were measured from the beginning of pre-exercise rest to the end of recovery period. We provided reference values for peak workload and changes in HR and SBP during and after maximal exercise test in girls and boys. Girls had a lower cardiovascular fitness, indicated by peak workload per body weight [mean (2 s) 2.7 (0.9) vs. 3.1 (1.0) W · kg(-1), P < 0.001] and lean mass [mean (2 s) 3.5 (0.9) vs. 3.8 (1.0) W · kg(-1), P < 0.001] than boys. Plateau or decline in SBP close to the end of the test was found in about third of children and was considered a normal SBP response. Girls had a slower HR decrease within 2 min after the test than boys [mean (2 s) 53 (18) vs. 59 (22) beats · min(-1), P < 0.001]. The results are useful for physicians and exercise physiologists to evaluate cardiovascular fitness and haemodynamic responses to exercise in children and to detect children with low exercise tolerance or abnormal haemodynamic responses to exercise.

Systemic blood pressure after stent management for arch coarctation implications for clinical care

OBJECTIVES

The goal of this study was to prospectively assess blood pressure (BP) and echocardiographic parameters to delineate the incidence and nature of the hypertension burden in this cohort.

BACKGROUND

Few data are available on the long-term outcomes of aortic stenting.

METHODS

Thirty-one patients with successfully stented coarctation during childhood (mean age 12.4 years) underwent 24-h ambulatory BP monitoring (ABPM), exercise BP measurement, and echocardiographic assessment.

RESULTS

Mean time after stent implantation was 5.3 ± 4 years. Hypertension was noted on one-off right-arm BP assessment in 3 patients (10%), but on the basis of the 24-h ABPM assessment in 14 patients (45%). Twenty-four of 31 patients (80%) had an abnormally elevated exercise BP response. Peak exercise BP correlated with left ventricular mass index (r = 0.51; p < 0.05), which was also significantly increased in the entire cohort (mean = 91.3 g/m(2); p < 0.05). In patients with significant somatic growth since implantation, the indexed diameter of the stent (to aortic diameter) had significantly decreased from the 48th percentile at the implantation to the 4th percentile during the study (p < 0.05). There was no difference in any parameter between patients with native or those with recurrent coarctation.

CONCLUSIONS

Hypertension is endemic in patients with stented coarctation, irrespective of the absence of residual obstruction. Due to abnormal BP homeostasis, hypertension should be aggressively pursued by ABPM assessment and exercise stress testing in this population. Relative hypoplasia of the stented arch after somatic growth may contribute to this tendency and should provoke consideration of elective serial redilation of coarctation stents.

Predictors of exaggerated exercise-induced systolic blood pressures in young patients after coarctation repair

BACKGROUND

In normotensive subjects, an exaggerated blood pressure response to exercise is associated with the development of resting hypertension. We sought to determine the prevalence of elevated blood pressures during exercise in post-operative coarctation patients with normal resting blood pressure, and investigate associations with exercise-induced hypertension in this population.

METHODS

A total of 38 patients were enrolled after end-to-end anastomosis repair and resting normotension. All patients underwent anthropometric and blood pressure measurements, echocardiographic evaluation of function, arterial stiffness assessment by pulse wave velocity, and a graded exercise test. An abnormal response was defined as a maximum systolic blood pressure greater than the 95th percentile of published normal values. Correlation analyses and stepwise regression analyses were performed.

RESULTS

The mean age was 12.7 years, including 79% male patients. The mean resting systolic blood pressure was 111.3 millimetres of mercury and the mean exercise systolic blood pressure was 178.1 millimetres of mercury. The prevalence of a systolic blood pressure greater than the 95th percentile was 16.7%. In multivariate analysis, the exercise systolic blood pressure index was associated with body mass index, age, aortic valve annulus, shortening fraction, and pulse wave velocity (R2 equal to 0.79, p equal to 0.0009). Estimates of ventricular filling and indexed left ventricular mass were elevated.

CONCLUSIONS

There is a risk of elevated systolic blood pressure during exercise in normotensive patients after coarctation repair. Resting blood pressures are useful but not sufficient. Echocardiography demonstrated abnormalities suggestive of a chronic cardiac burden despite resting normotension. Regular imaging may be necessary to improve long-term outcomes. New paradigms for the continued follow-up of these patients are necessary.

KINEMATICS PROPERTIES AND ENERGY COST OF BELOW-KNEE AMPUTEES

This study scientifically measures the dynamic gait characteristics and energy cost of six male below-knee amputees, three vascular and three traumatic, while wearing SACH, single axis and multiple axis prosthetic feet via six-camera motion analysis, metabolic measurement cart and heavy-duty treadmill. Subjective results are additionally determined via questionnaire after testing. Motion analysis showed statistically significant differences at p < 0.05 between the solid ankle cushion heel (SACH), single axis and multiple axis foot in the velocity, cadence, stride length end gait cycle. Significant differences were found in energy cost among the prosthetic feet tested, and significant changes in walking under different speeds and different inclines. Results provide quantitative and qualitative information about the dynamic performance of the various feet which can be helpful in prescribing the optimal prosthetic foot for individual amputees.

Cardiopulmonary exercise testing in congenital heart disease: equipment and test protocols

Cardiopulmonary exercise testing (CPET) in paediatric cardiology differs in many aspects from the tests as performed in adult cardiology. Children's cardiovascular responses during exercise testing present different characteristics, particularly oxygen uptake, heart rate and blood pressure response, which are essential in interpreting haemodynamic data. Diseases that are associated with myocardial ischaemia are very rare in children. The main indications for CPET in children are evaluation of exercise capacity and the identification of exercise-induced arrhythmias. In this article we will review exercise equipment and test protocols for CPET in children with congenital heart disease. (Neth Heart J 2009;17:339-44.).

Exercise performance in adolescents with autonomic dysfunction

OBJECTIVE

To test the hypothesis that excessive postural tachycardia is associated with deconditioning rather than merely being an independent sign of autonomic dysfunction in patients with postural orthostatic tachycardia syndrome (POTS).

STUDY DESIGN

We retrospectively analyzed records from 202 adolescents who underwent both head up-tilt and maximal exercise testing. Patients were classified as POTS if they had ≥ 30 min(-1) rise in heart rate (HR) after tilt-table test; and deconditioned if peak O(2) uptake was < 80% predicted. Changes in HR during exercise and recovery were compared between groups.

RESULTS

Two-thirds of patients were deconditioned, irrespective of whether they fulfilled diagnostic criteria for POTS, but peak O(2) uptake among patients with POTS was similar to patients without POTS. HR was higher at rest and during exercise; whereas stroke volume was lower during exercise, and HR recovery was slower in patients with POTS compared with patients without POTS.

CONCLUSIONS

Most patients who presented with chronic symptoms of dizziness, fatigue, or pre-syncope, were deconditioned, but, because the proportion of deconditioned patients was similar in POTS vs non-POTS groups, we conclude that HR changes in POTS are not solely because of inactivity resulting in deconditioning.

Relation of systemic venous return, pulmonary vascular resistance, and diastolic dysfunction to exercise capacity in patients with single ventricle receiving fontan palliation

Fontan patients have a reduced exercise capacity, primarily owing to limitations in the ability to augment pulmonary blood flow and stroke volume. To date, the mechanism of peak exercise pulmonary blood flow restriction has not been elucidated. We performed a single-center, prospective, crossover trial of supine and upright exercise in Fontan patients and healthy controls to determine the mechanisms of exercise limitation in the Fontan-palliated patient. A total of 29 Fontan patients and 16 control subjects completed the protocol. The duration of exercise, percentage of predicted peak oxygen consumption (VO(2)) and peak work were reduced in the Fontan group, regardless of posture (p < or = 0.03). The percentage of predicted oxygen pulse, a surrogate for pulmonary stroke volume, was not increased with supine posture in the Fontan cohort (upright, 82.3 + or - 18.8% vs supine, 82.4 + or - 19.7%; p = 0.6). In both groups, the percentage of predicted peak VO(2) was lower with supine exercise than with upright exercise (p < or =0.002). Diastolic dysfunction was present in 57% of the Fontan patients and was associated with a reduced percentage of predicted peak VO(2) (p = 0.04) and supine peak work (p = 0.008). Six Fontan patients who underwent supine exercise with indwelling catheters failed to demonstrate the expected decrease in pulmonary vascular resistance characteristically seen with peak exercise (at rest, 2.8 + or - 0.7 mm Hg/L/min/m(2) vs at peak, 2.8 + or - 0.9 mm Hg/L/min/m(2); p = 0.9). In conclusion, supine exercise in Fontan patients does not result in an increased VO(2) or oxygen pulse, suggesting that inadequate venous return might not be the primary limitation of exercise capacity in this population. Diastolic dysfunction and relatively excessive peak exercise pulmonary vascular resistance might be more important factors in Fontan exercise limitation.

Insulin resistance and exercise capacity in male children and adolescents with non-alcholic fatty liver disease

Insulin resistance (IR) and obesity may be associated with impaired response to physical exercise. We aimed at assessing physical capacity in obese children with biopsy proven non-alcoholic fatty liver disease (NAFLD) as compared to normal weight and obese children without fatty liver disease. All male subjects, 20 NAFLD and 31 control individuals (20 obese, without NAFLD and 11 normal weight children) took part in the study. We evaluated changes in cardiovascular parameters during a bicycle-ergometer exercise test (James' test). Duration, power of exercise, heart rate (HR), blood pressure (BP), pulse pressure, cardiac output ((I)CO) and total peripheral vascular resistance indexed for height ((I)TPVR) were recorded at rest ((r)) and peak ((p)) exercise. The homeostatic model assessment was used to determine insulin resistance (HOMA-IR) and beta-cell action (HOMA-beta cell). In NAFLD and obese subjects, fasting leptin, insulin secretion, insulinogenic index (IGI), muscle insulin sensitivity (MISI) and hepatic insulin resistance index (HIRI) were assayed. Children with NAFLD were the most insulin-resistant (P = 0.001), and showed higher HIRI than obese controls (P = 0.05). At rest, they had the lowest values of SBP(r) (P = 0.001 vs. controls and P < or = 0.05 vs. obese controls); during the test, the highest values of (I)CO(p) (P = 0.005), Delta(I)CO (P = 0.003) and DeltaTRVP(p) (P < or = 0.0001). NAFLD and obese controls both had impaired DeltaHR(p) (P < or = 0.0001). However, obese controls were not able to reduce peripheral resistance during the test. HOMA-IR explained 28% of variance in Delta(I)CO of the whole sample, (P < or = 0.0001). In obese children with or without NAFLD, increased IR and body weight may induce cardiovascular compensatory changes in response to physical exercise with fairly different pathogenetic mechanisms, which are likely to be dependent on the different degree of IR.

Cardiac output and associated left ventricular hypertrophy in pediatric chronic kidney disease

A significant number of children with chronic kidney disease (CKD) have eccentric left ventricular hypertrophy (LVH), suggesting the role of preload overload. Therefore, we hypothesized that increased cardiac output (CO) might be a contributing factor for increased left ventricular mass index (LVMI) in these children. Patients aged 6-20 years with CKD stages 2-4 were enrolled. Echocardiograms were performed to assess LV function and geometry at rest and during exercise. Heart rate, stroke volume, and CO were also assessed at rest and during exercise. Twenty-four-hour ambulatory blood pressure (AMBP) monitoring was performed. Of the patients enrolled in this study, 17% had LVH. Increased stroke volume and CO were observed in patients with LVH compared to patients without LVH. Univariate analysis revealed significant positive associations between LVMI and CO, stroke volume, body mass index, pulse pressure from mean 24-h AMBP, and mean 24-h systolic BP load. No association with heart rate, age, parathyroid hormone, glomerular filtration rate, or anemia was observed. Only CO (beta = 1.98, p = 0.0005) was independently associated with increased LVMI in multivariate modeling (model R (2) = 0.25). The results of this study suggest that increased CO might predispose to increased LVMI in pediatric patients with CKD. Adaptations may be required to meet increased metabolic demand in these patients.

Decreased maximal aerobic capacity in pediatric chronic kidney disease

Adult and pediatric patients with ESRD have impaired maximum oxygen consumption (VO(2) max), a reflection of the cardiopulmonary system's ability to meet increased metabolic demands. We sought to determine factors associated with decreased VO(2) max in pediatric patients with different stages of CKD. VO(2) max was measured using a standardized exercise testing protocol in patients with stage 2 to 4 chronic kidney disease (CKD) (n = 46), in renal transplant recipients (n = 22), in patients treated with maintenance hemodialysis (n = 12), and in age-matched healthy controls (n = 33). VO(2) max was similar between children with stage 2 CKD and controls, whereas lower VO(2) max was observed among children with stage 3 to 4 CKD, those treated with hemodialysis, and transplant recipients. In univariate analysis, VO(2) max was significantly associated with body mass index, resting heart rate, C-reactive protein, serum triglycerides, serum creatinine, and measures of diastolic function; no significant associations with left ventricular structure or systolic function were identified. In multivariate regression analysis, patient category versus control and the presence of diastolic dysfunction were independent predictors of lower VO(2) max. These results suggest that aerobic capacity is decreased in the early stages of CKD in children and that lower VO(2) max can be predicted by the presence of diastolic dysfunction, even if systolic function is normal.

Aortic arch geometry and exercise-induced hypertension in aortic coarctation

Hypertension at rest or during effort is not uncommon in patients with aortic coarctation (CoA), even those with a successful repair or mild degree of obstruction. Anatomic factors and functional abnormalities have been proposed as causes of this finding. Recently, aortic arch geometry was reported in association with hypertension at rest in patients with successful CoA repair. Forty-one patients (age 15.7 +/- 4.6 years) without significant obstruction at rest (mean systolic Doppler gradient at rest < or =25 mm Hg) were selected for the study. All patients underwent a maximal cardiopulmonary exercise test and magnetic resonance imaging of the aorta. Aortic arch shape was defined on global geometry as normal, gothic, and crenel. Percentage of anatomic narrowing (AN) was also calculated. Twenty-four patients (58%) showed exercise-induced hypertension (EIH). Regarding the shape of the aortic arch, normal geometry was present in 17 patients (41%), 9 (21%) had gothic geometry, and 15 (36%) had crenel geometry. There were no differences among the 3 geometries in regard to the incidence of EIH (70.6% in normal, 55.6% in gothic, and 46.7% in crenel) or AN (36.9% in normal, 33.5% in gothic, and 36.6% in crenel). In conclusion, our results fail to show a correlation between a specific aortic arch shape and the incidence of EIH and significant AN in patients with native or residual CoA or repeat CoA. Therefore, at present, the role of aortic arch geometry in identifying patients at risk of EIH is still uncertain.

Atrioventricular nodal reentrant tachycardia in children

The purpose of this study was to identify the clinical and electrophysiological characteristics of children with atrioventricular reentry tachycardia (AVNRT) and to define the prognosis and the treatment strategy. Sixty-two children (28 males and 34 females mean age, 10.2 +/- 3.2 years) with AVNRT ("slow-fast" type) were included in the study. Patients were divided into two groups: 47 patients with severe symptoms (group A) and 15 with mild symptoms (group B). The severity of the symptoms was not related to the electrophysiological parameters. Females were more symptomatic than males. Patients in group B did not receive any treatment (except 1 because of parents' choice) nor did they develop symptoms, and 5 patients had resolution of palpitations. Forty-one of 46 patients in group A were successfully treated with medical therapy as initial treatment. Thirty-one patients in group A underwent slow pathway ablation. There were late recurrences of AVNRT in 6 patients. Typical AVNRT in young patients does not appear to be life threatening. Patients with mild or no symptoms do well without therapy. Medical therapy and slow pathway ablation appear to be effective in the more symptomatic patients. Age and electrophysiological variables are not related to the symptoms or response to treatment. Females with AVNRT are more symptomatic and more likely to present with syncope.

The fate of systemic blood pressure in patients after effectively stented coarctation

AIMS

The current study was designed to assess midterm results of stent implantation into the aorta for native and recurrent coarctation (CoA) in children and young adults.

METHODS AND RESULTS

Forty-three patients (native CoA, 8; female, 12) were treated with stent implantation at a median age of 16.8 years (range 7.9-44.8 years). Only stents dilatable to an adult size aorta were implanted. All but two patients with functionally univentricular hearts had arterial hypertension. Exercise tests, 24-h blood pressure, clinical examination, echocardiography, and elective catheterization were used to assess follow-up. The narrowed segment was widened significantly from a median of 8 to 12.4 mm (P < 0.0005). The peak-to-peak gradient between the ascending and the descending aorta was lowered significantly from a median of 22 mmHg to 1 mmHg (P < 0.0005). No major complications occurred. The systolic blood pressure at the right arm was lowered significantly (P < 0.0005) from 144 mmHg before stent implantation to 128 mmHg at the last visit. At a median follow-up of 30 months (3-72 months), 68% of all patients were classified to be normotensive.

CONCLUSION

Stent implantation for selected patients with recurrent and native CoA is safe and may effectively reduce the blood pressure gradient across the CoA site. We suggest using only stents dilatable to an adult size aorta. However, arterial hypertension persists in a significant number of the patients. Impaired elastic properties of the aorta may be the cause for this finding.

Long-term outcome after surgical closure of atrial septal defect in childhood with extensive assessment including MRI measurement of the ventricles

Surgical closure of the secundum type of atrial septal defect (ASD) in childhood leads to excellent survival. However, relevant morbidity has been reported. Transcatheter closure of these defects has now become an alternative approach. To compare the results of the two different interventions, reliable data are needed on the long-term morbidity after defect closure with both methods. Patients were evaluated after a minimum of 10 years after surgical closure of an ASD in childhood. Assessment included analysis of perioperative data, interview, clinical examination, electrocardiogram, (ECG), 24-hour ECG, ergometry, chest radiograph, echocardiography, and MRI. A total of 66 patients underwent operation between 1971 and 1986 at our institution. Forty-eight of them (73%) were interviewed and 38 (58%) participated fully in the study program. Eighteen (27%) either refused to participate or were lost to follow-up. There were no substantial residual disorders, such as arrhythmias, right-sided heart dilatation, pulmonary hypertension, or reduced work capacity. Surgical closure of an ASD in childhood has an excellent long-term outcome. Surgical closure is thus the standard against which transcatheter closure needs to be measured.

Blood pressure and total peripheral resistance in children with chronic kidney disease

We performed a study to assess cardiac output (CO) and total peripheral resistance (TPR) at rest and during peak exercise with the goal to better define the role of these parameters in the development of hypertension in children with chronic kidney disease (CKD) stage 2-4. Fifty-two pediatric patients with CKD (mean age 12.7+/-3.7 years) and 28 healthy individuals of comparable age and sex participated in the study. At rest, children with CKD had a significantly higher systolic and diastolic blood pressure (BP) and calculated mean arterial pressure (MAP) than healthy controls. Total peripheral resistance was significantly higher in children with CKD than in controls (1627.7+/-534.6 vs 1354.6+/-338.9 dynexsxcm(-5), p =0.02). There was no significant difference in heart rate or CO between the two groups. Children taking antihypertensive medications had lower TPR than children without BP medications (1514.6+/-439.6 vs 1788.2+/-505.4 dynexsxcm(-5), respectively, p =0.06). At peak exercise, children with CKD had a significant increase in MAP, heart rate and CO and had a significant decrease in TPR (difference between rest and peak exercise: -782.4+/-375.9 dynexsxcm(-5), p <0.001). Children taking BP medications had blunted MAP and CO responses when compared to controls (Delta CO: 6.2+/-2.8 l/min vs 9.8+/-4.5 l/min, respectively, p =0.01; MAP: 13.9+/-10.2 mmHg vs 21.5+/-11.7 mmHg, respectively, p =0.01). Children without BP medications had a similar to controls response to exercise in respect to CO, MAP and TPR. We conclude that increased TPR is a major contributor to elevated blood pressure in children with CKD and suggest that BP medications decreasing vascular resistance should be used as a first line of antihypertensive therapy in these patients.

Exercise-induced stridor due to abnormal movement of the arytenoid area: videoendoscopic diagnosis and characterization of the "at risk" group

We evaluated 4 patients who developed severe, symptomatic stridor during maximal cardiopulmonary exercise testing, all referred due to exercise-related dyspnea. All underwent resting, unsedated transnasal fiberoptic laryngoscopy and had normal findings. Four patients performed repeat maximal exercise testing with fiberoptic laryngoscopy, and they form the basis of this report. They had normal vocal cord motion during exercise, but developed abnormal anterior motion of the arytenoid and aryepiglottic folds only at peak exercise, leading to partial airway obstruction and severe stridor. This report details the workup and characterizes patients at risk for this unusual phenomenon.

Development of exercise-induced arm-leg blood pressure gradient and abnormal arterial compliance in patients with repaired coarctation of the aorta

Often, the lack of systemic arterial hypertension and the lack of a resting arm-leg blood pressure gradient are used to assess the adequacy of the anatomic result after intervention for coarctation of the aorta (CoA). Some patients with no arm-leg gradient at rest may develop a gradient with exercise, leading caregivers to question the success of the repair. It is not clear what the prevalence is of patients who have undergone a successful intervention for CoA and have no arm-leg gradient at rest but develop a significant gradient with exercise and which factors may predict the development of an arm-leg gradient with exercise. This study evaluates the prevalence and predictors of an exercise-induced arm-leg gradient in subjects who have undergone an apparently successful intervention for CoA.

Abnormal cardiac function in children after renal transplantation

BACKGROUND

Cardiac hypertrophy frequently is found in children with a renal transplant. In adults with a transplant, left ventricular (LV) mass (LVM) is associated with cardiac dysfunction. However, in children with a transplant, the relationship between LVM and LV function has not been evaluated.

METHODS

Twenty-nine children who underwent transplantation and 33 controls had echocardiographic evaluations during rest and peak exercise. LV contractility was determined based on the relation between heart rate-corrected velocity of circumferential fiber shortening and end-systolic wall stress. Contractile reserve was assessed by the difference between contractility at rest and peak exercise. Early diastole was assessed using indices of LV relaxation derived from transmitral and tissue Doppler and reported as maximal early (E wave) and late (A wave) wave ratio (E-A ratio) and septal mitral annular velocities (Em). Late diastole was determined using an index of LV compliance (E-Em ratio).

RESULTS

Compared with controls, children with a transplant had a significantly greater LVM index (P < 0.001) and high prevalence of LV hypertrophy (LVH; 55%). Transplant recipients had increased LV contractility (P < 0.001). Contractile reserve was similar to that of controls. Patients with a transplant had a lower E-A ratio and Em (P < 0.01 for both variables) and higher E-Em ratio (P < 0.001) than controls. In children with a transplant, LVM index was a significant independent predictor for both abnormal LV relaxation (Em; P = 0.03) and abnormal LV compliance (E-Em ratio; P = 0.02).

CONCLUSION

Results show impaired cardiac structure and diastolic function in pediatric renal allograft recipients. This suggests that LVH may be a risk factor for diastolic dysfunction in these children.

Exercise testing in children -- what works, what doesn't, and where to go?

Exercise testing is a valuable tool in the assessment of healthy children and those with a chronic disease. However, especially for testing small children modified equipment is required. The choice of the exercise protocol and the outcome variables depends mainly on the reason for conducting the test. Future developments in pediatric exercise testing will focus on testing protocols designed to accommodate the specific biology and behavior of children. A further focus will be on the development of norms based on appropriate scaling techniques.

Cardiovascular physiology during supine cycle ergometry and dobutamine stress

PURPOSE

This study compared cardiac hemodynamics during supine cycle ergometry and dobutamine stress.

METHODS

Thirty-two healthy volunteers (19 female, 13 male, 23.5 +/- 3.5 yr old) completed respective tests on separate days and in random order. Heart rate, blood pressure, and cardiac output were recorded at baseline and peak stress. Echocardiographic measures included left ventricular end-diastolic dimension, fractional shortening, heart rate corrected velocity of circumferential fiber shortening, end-systolic wall stress, and the difference between measured and predicted fiber shortening for measured wall stress.

RESULTS

Compared with peak exercise, dobutamine infusion resulted in lower cardiac output (12 +/- 2 vs 16 +/- 4 l x min(-1), P < 0.0001), heart rates (163 +/- 7 vs 175 +/- 12 beats x min(-1), P < 0.0001), and systolic blood pressure (160 +/- 22 vs 185 +/- 20 mm Hg, P < or = 0.0001). Echocardiography demonstrated smaller left ventricular end-diastolic dimension (4.2 +/- 0.7 vs 4.5 +/- 0.7 cm, P = 0.013), higher fractional shortening (0.55 +/- 0.07 vs 0.50 +/- 0.06%, P < 0.001), higher VCFc (2.07 +/- 0.36 vs 1.54 +/- 0.20 circs x s(-1), P < 0.001) higher VCFdiff (0.94 +/- 0.35 vs 0.48 +/- 0.20 circs x s(-1), P < 0.001), and lower end-systolic wall stress (25 +/- 11 vs 42 +/- 16 g x cm(-2), P < 0.001). The stress-velocity relationship during dobutamine demonstrated higher y-intercept and steeper slope, indicating greater load-independent contractility.

CONCLUSION

The cardiovascular adaptation to exercise and dobutamine stress differ significantly. Cardiac output during peak exercise is greater than during peak dobutamine secondary to increased heart rate and stroke volume. Despite a greater increase in contractility and decrease in afterload, a smaller increase in cardiac output during dobutamine stress may be secondary to limited ventricular preload.

Pulmonary function and exercise response in patients with pectus excavatum after Nuss repair

BACKGROUND/PURPOSE

The Ravitch repair of pectus excavatum removes segments of abnormal costal cartilages after which the sternum is elevated and stabilized. Some investigators have found a worsening in total lung capacity postoperatively. Recently, a technique has been used in which the costal cartilages are preserved, and the sternum is elevated with an internal steel bar (Nuss repair). The authors hypothesized that placement of a substernal bar in the first stage of the Nuss repair will not adversely affect pulmonary and exercise function.

METHODS

Patients who presented to the Children's Hospital of Buffalo for surgical repair of pectus excavatum from June 1997 through June 2000 underwent pulmonary function and exercise testing before and 6 to 12 months after the first stage of a Nuss repair.

RESULTS

Ten patients were studied (all boys; mean age at operative repair, 13.4 +/- 3 years). Mean baseline pulmonary function was normal, and no significant differences were seen before and after placement of the intrathoracic bar. Peak oxygen consumption was near normal, although work at VO2max was less than predicted (mean, 68.2% before v. 71.8% after surgery). V(E) was below normal and Vt/FVC was below the expected 50% to 60% level both before and after surgery (41.3% +/- 3 SE and 41.6% +/- 3 SE pre- and postoperatively, respectively).

CONCLUSIONS

Placement of a substernal steel bar in the first stage of the Nuss procedure for repair of pectus excavatum does not cause adverse effects on either static pulmonary function or on the ventilatory response to exercise.

Fontan conversion to total cavopulmonary connection and arrhythmia ablation: clinical and functional results

OBJECTIVES

To assess the early results of conversion from atriopulmonary to total cavopulmonary connection in patients with failing Fontan operation.

DESIGN

Early clinical and instrumental evaluation of patients undergoing conversion from atriopulmonary to total cavopulmonary connection from April 1999 to November 2000.

SETTING

Tertiary referral centre for congenital heart disease.

PATIENTS

11 Fontan patients (mean (SD) age 20.9 (6.7) years) with refractory arrhythmias or ventricular dysfunction.

INTERVENTIONS

Total cavopulmonary connection, intraoperative ablation, and AAIR pacemaker implantation.

MAIN OUTCOME MEASURES

Holter monitoring, transoesophageal atrial stimulation, ergometric test, and myocardial scintigraphy at a mean (SD) follow up of 16.8 (5.6) months.

RESULTS

One early postoperative death occurred. During follow up three patients had relapse of atrial tachycardia, controlled by medical treatment, and two were pacemaker dependent. Transoesophageal stimulation did not induce atrial tachycardia in any patient. Ergometric test showed a diminished exercise tolerance in all but one patient. Mean minute ventilation and maximum oxygen consumption were 62% and 40% of their respective predicted values. Myocardial scintigraphy showed reversal of rest or exercise dysfunction in five patients and improved systemic ventricular function in seven. Mean basal ejection fraction increased from 39.4% (95% confidence interval (CI) 32% to 46%) to 46.5% (95% CI 41.7% to 51.2%) and ejection fraction on effort from 42.3% (95% CI 33.9% to 50.7%) to 50.2% (95% CI 44.5% to 55.9%).

CONCLUSIONS

Our data show that total cavopulmonary connection associated with intraoperative ablation and pacemaker implantation allows for better control of arrhythmias and improves ventricular function in the majority of patients with failing Fontan.

Is there a role for intravenous transpulmonary contrast imaging in pediatric stress echocardiography?

OBJECTIVE

Intravenous transpulmonary contrast echocardiography plays a significant role in the enhancement of endocardial border delineation during stress echocardiography in the adult population. The current study was conducted to evaluate the feasibility of intravenous transpulmonary contrast in pediatric patients and to compare the quality of endocardial visualization by harmonic 2-dimensional (2D) imaging alone with harmonic 2D echocardiography with contrast imaging.

METHODS

Twenty-two children, age 9.3 +/- 3.9 underwent dobutamine (19 patients) or exercise (3 patients) stress echocardiography. None had intracardiac shunting. Each patient underwent both harmonic 2D imaging alone and harmonic 2D imaging with contrast administration at peak stress. Oxygen saturation, heart rate, and blood pressure were monitored. Endocardial delineation was evaluated by qualitative grading of 22 endomyocardial regional segments in each patient. Contrast images were graded by an echocardiographer who was blinded to the scores previously assigned to harmonic 2D echocardiography images.

RESULTS

There were no changes in saturation, heart rate, or blood pressure during or after contrast administration. Use of contrast significantly improved endocardial visualization in 11 of 22 segments (P <.05), particularly lateral, apical, and anterior left ventricular wall segments.

CONCLUSION

Intravenous intrapulmonary administration is feasible and has no obvious adverse effects in a small pediatric patient group. Contrast echocardiography improves endocardial border delineation over harmonic imaging in pediatric stress echocardiography.

Responses of non-obese white children to treadmill exercise

OBJECTIVE

To determine the response to maximal treadmill exercise with the Bruce protocol in a cohort of healthy non-obese American children and adolescents.

STUDY DESIGN

A retrospective review of treadmill exercise studies on 347 white American children (188 boys, 159 girls) aged 5 to 18 years was performed with metabolic criteria to verify maximal exercise effort. Data on exercise endurance time, heart rate, blood pressure, and metabolic variables were assessed and compared between age groups and sexes by unpaired t testing and analysis of variance.

RESULTS

Exercise endurance time was lower in all age groups when compared with earlier published data. Girls had a lower endurance time than boys at all ages. There was no significant difference in maximum heart rate with respect to age or sex. The maximum systolic blood pressure and diastolic blood pressure increased with increasing age in both boys and girls. Boys had significantly higher maximum systolic blood pressure and diastolic blood pressure after 13 years of age. The maximum absolute oxygen consumption and indexed oxygen consumption showed similar trends for both sexes.

CONCLUSION

Lower exercise endurance times are seen despite physiologic evidence of maximal effort, raising the possibility that cardiovascular conditioning is reduced in contemporary American children.

Abnormal responses for blood pressure in children and adults with surgically corrected aortic coarctation

BACKGROUND

Despite successful surgical repair of aortic coarctation, life expectancy is reduced, and up to one-third of patients remain or become hypertensive. So as to characterize the responses for blood pressure, we have studied 55 patients with surgically repaired coarctation. Their mean age was 11.3 +/- 5.97 years. We documented maximal uptake of oxygen, anaerobic threshold, plasma renin activity and blood pressures during a Bruce protocol treadmill test. The velocity across the site of repair as imaged by cross-sectional echocardiography was measured before and after exercise. We measured the changes in heart rate and blood pressure subsequent to an infusion of 1 ug per kg of isoprenalin, monitoring blood pressure over 24 hours in all patients.

RESULTS

When compared with 40 healthy age-matched controls, the patients with coarctation had a normal exercise capacity. Resting systolic blood pressures above the 95th percentile were present in 45% of the patients. Exercise-induced hypertension, and an elevation in the average systolic 24 hour blood pressures, were observed, but less frequently than elevated baseline values, suggesting that so-called white-coat" hypertension may be present in this population. Abnormal reactions and elevation of plasma renin activity were related to a history of paradoxical hypertension at the time of surgery. Attenuation of the circadian rhythm for blood pressure was a frequent finding, and may have implications in the development of long-term damage to end-organs. A high correlation was found between mean systolic blood pressure measured by 24 hour monitoring and left ventricular hypertrophy (r=0.65, p<0.05).

CONCLUSIONS

Abnormalities in blood pressure occurred independently of significant mechanical obstruction. Despite successful surgical repair, abnormalities in the shape of the aortic arch, reduced sensitivity of baroreceptor reflexes, and neurohumoral factors may all contribute to the development of hypertension.

The role of the right ventricle during hypobaric hypoxic exercise: insights from patients after the Fontan operation

OBJECTIVES

The principal objective of this study was to examine the importance of the right ventricle for maximal systemic oxygen transport during exercise at high altitude by studying patients after the Fontan operation.

BACKGROUND

High-altitude-induced hypoxia causes a reduction in maximal oxygen uptake. Normal right ventricular pump function may be critical to sustain cardiac output in the face of hypoxic pulmonary vasoconstriction. We hypothesized that patients after the Fontan operation, who lack a functional subpulmonary ventricle, would have a limited exercise capacity at altitude, with an inability to increase cardiac output.

METHODS

We measured oxygen uptake (VO2, Douglas bag), cardiac output (Qc, C2H2 rebreathing), heart rate (HR) (ECG), blood pressure (BP) (cuff), and O2 Sat (pulse oximetry) in 11 patients aged 14.5+/-5.2 yr (mean +/- SD) at 4.7+/-1.6 yr after surgery. Data were obtained at rest, at three submaximal steady state workrates, and at peak exercise on a cycle ergometer. All tests were performed at sea level (SL) and at simulated altitude (ALT) of 3048 m (10,000 ft, 522 torr) in a hypobaric chamber.

RESULTS

At SL, resting O2 sat was 92.6+/-4%. At ALT, O2 sat decreased to 88.2+/-4.6% (P < 0.05) at rest and decreased further to 80+/-6.3% (P < 0.05) with peak exercise. At SL, VO2 increased from 5.1+/-0.9 mL x kg(-1) x min(-1) at rest to 23.5+/-5.3 mL x kg(-1) x min(-1) at peak exercise and CI (Qc x m(-2)) increased from 3.3+/-0.7 L x m(-2) to 6.2+/-1.2 L x m(-2). VO2 peak, 17.8+/-4 mL x kg(-1) x min(-1) (P < 0.05), and CI peak, 5.0+/-1.5 L x m(-2) (P < 0.05), were both decreased at ALT. Remarkably, the relationship between Qc and VO2 was normal during submaximal exercise at both SL and ALT. However at ALT, stroke volume index (SVI, SV x m(-2)) decreased from 37.7+/-8.6 mL x min(-1) x m2 at rest, to 31.3+/-8.6 mL x min(-1) x m2 at peak exercise (P < 0.05), whereas it did not fall during sea level exercise.

CONCLUSIONS

During submaximal exercise at altitude, right ventricular contractile function is not necessary to increase cardiac output appropriately for oxygen uptake. However, normal right ventricular pump function may be necessary to achieve maximal cardiac output during exercise with acute high altitude exposure.

Long-term outcome and prognostic determinants in children with hypertrophic cardiomyopathy

OBJECTIVES

We sought to determine clinical, angiographic, and echocardiographic predictors of survival in children with isolated hypertrophic cardiomyopathy (HCM) in a large pediatric centre.

BACKGROUND

Sudden death is a catastrophic outcome of HCM in childhood but has been difficult to predict. Current therapies might provide for improved outcome if factors identifying high risk can be identified.

METHODS

Records of 99 patients diagnosed with HCM from 1958 to 1997 at <18 yr were reviewed for clinical, angiographic (n = 62) and echocardiographic (n = 83) predictors of survival outcome. The effects of clinical characteristics on sudden death (including resuscitated sudden death) were individually tested in Cox's proportionate hazard modeling.

RESULTS

Seventy-one subjects were male. Median age at diagnosis was 5.0 yr with a medical follow-up interval of 4.8 yr. Thirty-seven of 97 patients had a family history of HCM. Ambulatory electrocardiograms (ECG) in 78 patients demonstrated supraventricular tachycardia in 16 and ventricular tachycardia in 21. Death or resuscitated sudden death occurred in 18 patients. Sudden death rate was 2.7%/yr after age 8 yr. Cox's proportionate survival modeling revealed increased corrected QT interval (QTc) dispersion on ECG (relative risk [RR] 1.61 per 20 ms increment, p < 0.0003), ventricular tachycardia (VT) on ambulatory ECG (RR 3.75, p < 0.006) and myocardial bridging of the LAD coronary (RR 12.0, p < 0.003) to be associated with reduced time to death or resuscitated sudden death.

CONCLUSIONS

Detailed assessment of ECGs, ambulatory ECGs, and coronary angiography can assist in identifying which children with HCM are at risk for sudden death.