Current practice of exercise stress testing among pediatric cardiology and pulmonology centers in the United States

A Systematic Approach for the Interpretation of Cardiopulmonary Exercise Testing in Children with Focus on Cardiovascular Diseases

Cardiopulmonary exercise testing (CPET) is the clinical standard for children with congenital heart disease (CHD), heart failure (HF) being assessed for transplantation candidacy, and subjects with unexplained dyspnea on exertion. Heart, lung, skeletal muscle, peripheral vasculature, and cellular metabolism impairment frequently lead to circulatory, ventilatory, and gas exchange abnormalities during exercise. An integrated analysis of the multi-system response to exercise can be beneficial for differential diagnosis of exercise intolerance. The CPET combines standard graded cardiovascular stress testing with simultaneous ventilatory respired gas analysis. This review addresses the interpretation and clinical significance of CPET results with specific reference to cardiovascular diseases. The diagnostic values of commonly obtained CPET variables are discussed using an easy-to-use algorithm for physicians and trained nonphysician personnel in clinical practice.

Remodeling in the AV block dog is essential for tolerating moderate treadmill activity

Background

A preclinical model standardized at different remodeling stages after AV block induction in awake state is suitable for the evaluation of improved cardiac devices. We studied exercise-induced cardiorespiratory parameters at three different timepoints after inducing AV block in dogs.

Methods

Mongrel dogs (n = 12) were placed on a treadmill with a 10% incline and performed a moderate exercise protocol (10-minute run at 6 km/h). Dogs ran at sinus rhythm (SR), at two days (AVB2d, initiation of remodeling), three weeks (CAVB3) and six weeks (CAVB6, completed remodeling) after AV block.

Results

All dogs completed the exercise protocol at SR, CAVB3 and CAVB6, while 6/12 dogs at AVB2d failed to complete the exercise protocol. The atrial rate was higher at all AV block timepoints (126 ± 20 to 141 ± 19 bpm at rest and 221 ± 10 to 231 ± 13 bpm during exercise) compared to SR (100 ± 29 bpm at rest and 162 ± 28 bpm during exercise, p < 0.05). Upon exercise, stroke volume increased from 66 ± 15 ml at SR, to 96 ± 21 ml at AVB2d (p < 0.05), 91 ± 13 ml at CAVB3 (p < 0.05) and 85 ± 24 ml at CAVB6 but failed to compensate for the AV block-induced bradycardia. Therefore, cardiac output was lower after AV block compared to SR. Exercising dogs at AVB2d showed most arrhythmic events, lowest VO₂, and signs of desaturation and acidification in venous blood.

Conclusion

Dogs with limited remodeling after AV block have a reduced exercise tolerance, which is reflected in changes in cardiorespiratory parameters.

Practices and Procedures in Clinical Pediatric Exercise Laboratories in North America

Interinstitutional differences in clinical pediatric exercise laboratory (CPEL) practices may affect patient care and efficacy of multicenter research.

PURPOSE

To describe current practices/procedures in CPELs and explore differences in CPELs employing exercise physiologists to those that do not.

METHODS

A 40-item survey was distributed to CPELs in North America focusing on (1) staffing; (2) exercise stress testing (EST) volumes, reporting, and interpretation; and (3) EST procedures/protocols.

RESULTS

Of the 55 responses, 89% were in the United States, 85% were children's hospitals with university affiliation, and 58% were cardiology specific. Exercise physiologists were employed in 56% of CPELs, and 78% had master's degrees or higher. Certifications were required in most CPELs (92% emergency life-support, 27% professional, and 21% clinical). Median volume was 201 to 400 ESTs per year, 80% used treadmill, and 10% used cycle ergometer as primary modalities. Ninety-three percent of CPELs offered metabolic ESTs, 87% offered pulmonary function testing, 20% used institution-specific EST protocols, and 72% offered additional services such as cardiac/pulmonary rehabilitation. CPELS staffing exercise physiologists performed higher volumes of ESTs (P = .004), were more likely to perform metabolic ESTs (P = .028), participated in more research (P < .001), and provided services in addition to ESTs (P = .001).

CONCLUSIONS

Heterogeneity in CPELs staffing and operation indicates need for standardization.

Comparison of Peak Oxygen Consumption During Exercise Testing Between Sexes Among Children and Adolescents in Taiwan

Objective: Studies among Western children have observed that the peak oxygen consumption (peak V ˙ O₂) of boys is higher than that of girls, and this difference increases as children progress through adolescence. However, the maturation process and social expectation toward Eastern boys and girls are much different from their Western counterparts. This study aimed to provide baseline information on cardiopulmonary fitness (CRF) of Taiwanese children and adolescents in relation to age and sex. We also evaluated the correlation between body mass and CRF and compared the CRF between non-obese and overweight/obese children. Methods: We conducted a retrospective study of children and adolescents aged 4-18 years in Taiwan. Participants were classified into four groups based on age (group 1, aged 4-6; group 2, aged 7-9; group 3, aged 10-13; and group 4, aged 14-18 years). All participants completed symptom-limited exercise test by treadmill and anthropometric measurements through bioelectrical impedance method. Results: In total, 897 (448 men, 449 women) participants were analyzed. Boys had higher peak V ˙ O₂ (all p < 0.01) and peak metabolic equivalent (MET, all p < 0.05) than girls in all the four groups. Age significantly (P < 0.001) correlated with peak V ˙ O₂ in all participants, boys, and girls, with coefficients of determination (R ²) of 0.9349, 0.9433, and 0.9085, respectively. The peak V ˙ O₂ (all p < 0.001) of all the groups and peak MET (all p < 0.05) of group 2-4 associated with BMI and FMI modestly to moderately. Non-obese children had higher peak MET in group 1 (p = 0.049) and group 2-4 (all p < 0.001) than overweight/obese children significantly. Conclusions: The difference in peak V ˙ O₂ and anthropometry-body composition between sexes was observed earlier in children in Taiwan than those in Western countries. Non-obese children had better CRF than overweight/obese children and the difference presented since preschool age.

Comparison of cardiorespiratory fitness between preschool children with normal and excess body adipose ~ An observational study

Objective

Overweight and obesity in preschoolers might develop into childhood and even adulthood obesity. Overweight and obesity have been shown to be negatively related with cardiorespiratory fitness (CRF) in children and adults but few studies did among preschoolers. We aimed to evaluate whether excess body adipose is negatively associated with CRF in both the submaximal and maximal effort of preschool children in exercise testing and to examine if there is difference to achieve maximal effort during exercise testing between preschoolers with normal and excess body adipose.

Methods

Data of 106 preschoolers aged 4–6 that received symptom-limited treadmill exercise testing was analyzed. Anthropometry was measured by vector bioelectrical impedance analysis. Excess body adipose was defined as (1) ‘overweight’ and ‘obesity’ by body mass index (BMI), (2) fat mass index (FMI) greater than the sex- and age-specific 75th percentile of whole subjects, and (3) fat-free mass index (FFMI) smaller than the sex- and age-specific 25th percentile. CRF was indicated by metabolic equivalent (MET) at anaerobic threshold (AT MET), peak MET, oxygen uptake efficiency slope (OUES) calculated by the 50% (OUES-50) and the entire (OUES-100) duration of the exercise testing.

Results

Preschoolers with excess body adipose by three different definitions (BMI, FMI, and FFMI) all had poorer ability to perform maximal effort (p = 0.004, 0.043, and 0.007, respectively). Preschoolers with excess body adipose by BMI and FFMI classifications had lower OUES-50 (p = 0.018, and 0.001, respectively), and lower OUES-100 (p = 0.004, and 0.001, respectively) than peers with normal body adipose during exercise testing while those with excess body adipose by FMI classification showed no significant differences from peers with normal body adipose in both OUES-50 and OUES-100.

Conclusions

Preschoolers with excess body adipose had lower CRF significantly during treadmill exercise testing. Weight control and health promotion should start as early as possible.

A Systematic Approach to Interpreting the Cardiopulmonary Exercise Test in Pediatrics

The use of cardiopulmonary exercise testing in pediatrics provides critical insights into potential physiological causes of unexplained exercise-related complaints or symptoms, as well as specific pathophysiological patterns based on physiological responses or abnormalities. Clinical interpretation of the results of a cardiopulmonary exercise test in pediatrics requires specific knowledge with regard to pathophysiological responses and interpretative strategies that can be adapted to address concerns specific to the child's medical condition or disability. In this review, the authors outline the 7-step interpretative approach that they apply in their outpatient clinic for diagnostic, prognostic, and evaluative purposes. This approach allows the pediatric clinician to interpret cardiopulmonary exercise testing results in a systematic order to support their physiological reasoning and clinical decision making.

Fitkids Treadmill Test: Clinical Utility and Factors Associated With Its Use Among Physical Therapists

BACKGROUND

Although the Fitkids Treadmill Test (FTT) has been validated and normative values are available for healthy 6- to 18-year-old children and adolescents, these facts do not automatically imply uptake of the test in routine practice of physical therapists.

OBJECTIVE

The objectives of this study were to evaluate the utility of the FTT in different diagnostic groups and to explore potential factors affecting the use of the FTT in clinical practice.

DESIGN

Mixed methods with both quantitative and qualitative data were used in this study.

METHODS

Outcome parameters from the FTT were retrieved from the Fitkids database. For evaluation of the utility of the FTT, 2 indicators, exercise duration and maximal effort, were used. An online survey was sent to physical therapists in Fitkids practices to identify factors affecting the use of the FTT in clinical practice.

RESULTS

The proportion of children and adolescents in each of the diagnostic groups who reached the minimal duration of a maximal exercise test ranged from 94% to 100%. The proportion of participants who reached a peak heart rate ≥180 beats/min ranged from 46% for participants with cognitive, psychological, or sensory disorders to 92% for participants with metabolic diseases. The most important facilitator for use of the FTT was the fact that most physical therapists were convinced of the additional value of the FTT. The main barriers were therapists' attitudes (resistance to change/lack of experience) and, on the environmental level, the absence of a treadmill ergometer in physical therapist practice.

LIMITATIONS

Structured interviews would have provided more information on potential factors affecting the use of the FTT in clinical practice.

CONCLUSIONS

This study has shown the clinical utility of the FTT in different diagnostic groups in pediatric physical therapist practice. Responding to the factors identified in this study should enable improved uptake of the FTT in clinical practice.

Incidence and Predictors of Clinically Important and Dangerous Arrhythmias During Exercise Tests in Pediatric and Congenital Heart Disease Patients

OBJECTIVES

This study quantified the incidence of arrhythmias during pediatric exercise stress tests (ESTs) and evaluated criteria to identify patients at risk of clinically important arrhythmias.

BACKGROUND

The incidence of clinically important arrhythmias during pediatric ESTs and criteria for identifying high-risk patients are poorly characterized.

METHODS

A retrospective review of ESTs performed from 2013 to 2015 was studied. Arrhythmias were categorized into 4 classes based on need for test termination and intervention. Risk factors evaluated included having an implantable cardioverter-defibrillator (ICD), cardiomyopathy, severe ventricular dysfunction, complex arrhythmia history, coronary disease with concern for ischemia, pulmonary hypertension, select poorly palliated congenital heart disease (CHD), and concerning symptoms. Negative predictive values (NPVs) were calculated.

RESULTS

During the study period, 5307 ESTs were performed. Median age of the subjects was 16 years (interquartile range: 13 to 24 years); 20% had complex CHD. At least 1 high-risk criterion was present in 507 tests (10%); having an ICD (37%) and cardiomyopathy (36%) were the most common criteria. Some arrhythmias were seen in 46% of tests, but only 33 events (0.6%) required test termination. Three events (0.06%) required cardiopulmonary resuscitation, all with high-risk criteria. Absence of a high-risk criterion had a 99.7% (95% confidence interval [CI]: 99.5% to 99.8%) NPV for an arrhythmia that required test termination and a 99.96% (95% CI: 99.85% to 99.99%) NPV for an arrhythmia that required intervention beyond test termination.

CONCLUSIONS

Although self-terminating arrhythmias are common, dangerous arrhythmias are rare during ESTs in a high-volume pediatric cardiology program. Pre-defined high-risk criteria identified all patients with the most serious events. The absence of any criteria predicted a low risk for arrhythmias that required test termination. These data permitted informed choices regarding supervision of ESTs.

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.).

Correlation of subjective questionnaires with cardiac function as determined by exercise testing in a pediatric population

BACKGROUND

Although exercise testing is an important objective method used to assess cardiopulmonary function, subjective assessment often is used as a proxy in the clinical setting. This study aimed to determine whether responses to a subjective functional capacity questionnaire administered to parents and patients in a pediatric exercise laboratory correlate with objective assessment of functional capacity, measured by peak oxygen consumption during maximal voluntary exercise testing.

METHODS

Subjective questionnaire responses and exercise test results collected over 10 years were retrospectively analyzed. Symptoms and physical capabilities were assessed using a 6-point Likert scale regarding the ability to attend school/work, walk, climb stairs, and run, as well as the frequency of fatigue, palpitations, and chest pain. Values of 0 to 3 were considered abnormal, whereas values of 4-5 were regarded as normal. Exercise testing was performed on a stationary cycle ergometer with a continuous ramping protocol. Heart rate and oxygen saturation were continuously monitored. Blood pressures and electrocardiograms (ECGs) were obtained at 2-min intervals. Metabolic gas analysis was performed using a breath-by-breath method. The results of the exercise testing were normalized for body size and expressed as a percentage of predicted peak oxygen consumption (%pVO(2)).

RESULTS

Very weak but statistically significant correlations (τ < 0.25; P < 0.05) between the scores of the school/work, walking, stair climbing, running, and fatigue items and %pVO(2) were found using Kendall's rank correlations.

CONCLUSIONS

The subjective Likert scales used to assess basic physical capacity and cardiac-associated symptoms have limited ability to predict actual functional capacity as measured by %pVO(2) achieved. The very weak rank-order correlation between %pVO(2) achieved and the subjective reporting of the ability to attend school/work, walk, climb stairs, and run has low clinical significance and will not be useful in predicting functional capacity within the clinic setting.

Results of exercise stress testing in patients with diffuse pulmonary arteriovenous malformations

Patients with diffuse pulmonary arteriovenous malformations (PAVMs) are subject to frequent complications and need to be followed closely. As part of this follow-up, we have employed exercise stress testing (EST) as an aid to assess their status. Twenty patients from a cohort of 35 with diffuse PAVMs have undergone EST using a standard cycle ergometer test. All patients had previously undergone pulmonary angiography, noncontrast chest computed tomography (CT), and repair of large focal PAVMs, prior to EST. Mean room air oxygen saturation at baseline and at maximum exercise (85% of maximum heart rate) were tabulated. Serial studies in six children and young adults were plotted by year and compared using the patient as their own control. Fourteen females and six males ranging in age from 4 to 50 years (mean 22 years) were studied. Baseline mean oxygen saturation was 84% and fell to 73% at maximum exercise. There was no significant difference between those with unilateral and bilateral involvement (P = 0.09). In four of the six patients with serial EST, the baseline and exercise oxygen saturations were quite stable. In the two patients who became symptomatic, with age, growth, and more activity, complete embolization of one or more segments of the lung improved their EST and functionality. Based on our previous work in patients with diffuse PAVMs, EST appears to offer a relatively safe and noninvasive method for assessing these patients. Our limited experience with serial EST suggests a good correlation with decreased functionality in these patients.

Submaximal treadmill test predicts VO2max in overweight children

OBJECTIVE

To demonstrate the ability of a submaximal test to predict VO(2max) in overweight children.

STUDY DESIGN

A total of 130 children, 11 to 14 years old, with body mass index >85 percentile for age and sex performed a submaximal walking test. VO(2max) was measured by using open circuit spirometry during a graded exercise test to volitional fatigue. An equation to predict VO(2max) was modeled by using the variables of sex, weight (kg), height (cm), heart rate (HR) after 4 minutes during the submaximal test (4minHR), HR difference (4minHR - resting HR), and submaximal treadmill speed (miles per hour [mph]) in 75% of the subjects. Validation was performed by using the remaining 25% of subjects.

RESULTS

A total of 113 subjects achieved a maximal effort and was used in the statistical analysis. Development and validation groups were similar in all aspects. On validation, the mean square error was 241.06 with the predicted VO(2max) within 10% of the observed value in 67% of subjects.

CONCLUSION

VO(2max) was accurately predicted in this cohort of overweight children by using a submaximal, treadmill-based testing protocol.

Exercise limitation in patients with Fontan circulation: a review

The aim of the current literature study was to perform a literature review of the factors contributing to exercise limitation and physiological response to exercise in patients with Fontan circulation. In patients with Fontan circulation, peak oxygen uptake ranged from about 14.4 to 32.3 ml/min/kg, and showed a slowed acceleration in the kinetics of oxygen uptake at the onset of exercise. Peak heart rate during exercise was decreased to an average of 153 +/- 10 bpm and arterial oxygen saturation was also decreased at peak exercise, with an average of 89.5 +/- 1.94%. Cardiac output was subnormal, owing to reduced stroke volume, heart rate response and affected pulmonary venous return. Ventilatory anaerobic threshold was below normal values. Moreover, the ventilatory equivalent for carbon dioxide was found to be higher. Patients with Fontan circulation possess a unique physiological response to exercise. Although there is a wide range in exercise capacity among patients, all patients have reduced tolerance to exercise. Cardiac, pulmonary, and muscular factors might play a role in reduced exercise capacity and this distinct response to exercise.