Background: Impaired exercise capacity is a common feature of congenital heart disease (CHD). In adults with CHD, it has been shown that impaired heart rate response during exercise may contribute to exercise limitation. Systematic data in children and adolescents on this topic is limited. We therefore purposed to assess heart rate response during treadmill exercise testing in children and adolescents with CHD compared to healthy controls.Methods: One hundred and sixty three children and adolescents (103 with CHD, median age 15 years and 60 age-matched controls) performed cardiopulmonary exercise testing and were included in this study. Beyond peak oxygen consumption, increase in heart rate from resting level to peak exercise (heart rate reserve) and decrease of heart rate after peak exercise (heart rate recovery) were measured. Chronotropic index was defined as percentage of age predicted maximal heart rate reserve. According to data from adults on bicycle exercise, chronotropic incompetence was assumed for chronotropic index below 0.8.Results: While resting heart rate was similar between both groups, peak heart rate, heart rate reserve as well as chronotropic index were lower in the CHD group than in controls. Chronotropic index was lowest in patients with single ventricle hemodynamics and correlated with peak oxygen consumption. Heart rate recovery was impaired in the CHD group 1 and 2 min after peak exercise compared to controls and correlated with peak oxygen consumption. Chronotropic index below 0.8 was a relatively frequent finding even in the control group suggesting that the threshold of 0.8 appears inadequate for the identification of chronotropic incompetence using treadmill exercise testing in children. After normalizing to the 2.5th chronotropic index percentile of the control group we obtained a chronotropic incompetence threshold of 0.69.Conclusion: As an adjunct to measurement of peak oxygen consumption, heart rate response to exercise appears to be a physiologically important diagnostic parameter in children and adolescents with CHD. However, interpretation of heart rate response needs to consider specific age characteristics and the mode of exercise test. Our data may help future studies on chronotropic incompetence using treadmill ergometer protocols in children and adolescents.

Objective: In children with congenital heart defects (CHD), a sedentary lifestyle should be avoided and usually WHO recommendations on physical activity (PA) are supposed to be followed. In order to obtain representative data of the actual amount of PA (and potential influencing factors) in children with CHD we performed a nationwide online survey. Methods: All patients aged 6-17 years registered in the German National Register for CHD were contacted by email and asked to participate in the survey using the comprehensive questionnaire of the "Motorik-Modul" from the German Health Interview and Examination Survey for Children and Adolescents (KiGGS), thus allowing the comparison with a representative age-matched subset of 3.385 participants of the KiGGS study. The questionnaire for CHD-patients was amended by specific questions regarding medical care, sports recommendations and PA restrictions. Results: Complete datasets of 1.198 patients (mean age of 11.6 ± 3.1 years) were available for evaluation. Compared to the reference group, CHD patients significantly less frequently reached the WHO recommended level of 60 min of daily PA (8.8 vs. 12%; p < 0.001). Enjoyment in sports was almost equally distributed across CHD and reference groups, and strongly correlated with the level of PA (r = 0.41; p < 0.001). Remarkably, 49.2% of children with complex CHD, 31.7% with moderate, and even 13.1% with simple CHD were advised by their physician to restrict PA. Conclusions: According to this nationwide survey, PA is markedly reduced in children with CHD. An important reason for this might be an unexpected high rate of physician-recommended restrictions on levels of PA.

Acute rejection of the donor heart is a major cause of mortality in infant heart transplant recipients. The early diagnosis of acute cardiac rejection (ACR) is crucial. Non-invasive methods have shown poor sensitivity in detecting rejection when compared to endomyocardial biopsies (EMB). We assessed troponin I as a new marker to diagnose cardiac rejection. Serum cardiac troponin I (cTNI) levels were retrospectively analysed in 25 heart transplant patients (ages, 2 wk to 13 yr; mean age, 3 months) presenting 36 acute rejections. In early post-operative rejection and initially elevated cTNI levels, rejection was associated with a second increase of serum cTNI concentrations in 21% of the patients (p = 0.15). If cTNI levels were in normal range before ACR an elevation was monitored in 59% of the rejection periods (p < 0.05). In 25% of the cases (n = 9) cTNI levels remained in normal range during the rejection episode (<0.6 ng/mL), in 22% (n = 8) cTNI levels did not exceed pathological values from 0.6 to 1.5 ng/mL and in 53% (n = 19) the measured levels went beyond 1.5 ng/mL. Maximum concentrations of cTNI were measured mostly 12 d from the moment rejection was suspected (day 1) in patients (median day 3). However, cTNI levels were elevated for 2-43 d after ACR was diagnosed (median 10 d). Twenty per cent of the patients with grade 3 rejection (ISHLT) and 75% of the patients with grade 4 rejection had a corresponding elevated cTNI level (p = 0.013). No false-positive elevations of cTNI were documented. The present data demonstrate that cTNI is a not a sensitive but a specific marker of ACR in children.