Exercise capacity in children with isolated congenital complete atrioventricular block: does pacing make a difference?

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.

Unusual course of congenital complete heart block in an adult: A case report

BACKGROUND

Congenital complete heart block (CCHB) with normal cardiac structure and negativity for anti-Ro/La antibody is rare. Additionally, CCHB is much less frequently diagnosed in adults, and its natural history in adults is less well known.

CASE SUMMARY

A 23-year-old woman was admitted to our hospital for frequent syncopal episodes. She had bradycardia at the age of 1 year but had never had impaired exercise capacity or a syncopal episode before admission. The possible diagnosis of acquired complete atrioventricular block was carefully ruled out, and then the diagnosis of CCHB was made. According to existing guidelines, permanent pacemaker implantation was recommended, but the patient declined. With regular follow-up for 28 years, the patient had an unusually good outcome without any invasive intervention or medicine. She had an uneventful pregnancy and led a normally active life without any symptoms of low cardiac output or syncopal recurrence.

CONCLUSION

This case implies that CCHB in adulthood may have good clinical outcomes and does not always require permanent pacemaker implantation.

Levels of Physical Activity and Physical Fitness in Pediatric Pacemaker Patients: A Cross-Sectional Study

Children with heart diseases have reduced physical activity (PA) levels relative to their peers, which in turn increases cardiovascular risk. To the best of our knowledge, physical fitness and objectively measured PA levels have not been previously studied in children with pacemakers. We evaluated PA levels and physical fitness in pediatric pacemaker patients compared to their healthy peers. Twenty-eight pediatric patients with pacemakers (15 female, 13 male; mean age 13.43 ± 3.68 years) and 24 healthy subjects (14 female, 10 male; mean age 13.08 ± 3.67 years) were included. Physical fitness was assessed using the Munich Fitness Test (MFT). SenseWear Armband metabolic Holter device was used to record the PA for 7 consecutive days. MFT total and sub-parameter scores were significantly lower in the patient group (p < 0.05). Patients' total and active energy expenditure, PA level, total distance, number of steps, and vigorous PA were significantly lower than those of healthy children (p < 0.05). Sedentary activity and light, moderate, and very vigorous PA durations were similar in both groups (p > 0.05). Duration of mean moderate to vigorous PA was higher than 60 min/day recommended in PA guidelines in both patients and healthy subjects. These results provide initial data on PA and fitness in children with pacemakers and suggest that physical fitness and activity levels in children with pacemakers are lower than in healthy peers. Appropriate exercise programs may improve PA levels in pediatric pacemaker patients. Awareness of the importance of PA should be raised among the parents and families of these children.

Follow-up of isolated congenital complete atrioventricular block with longitudinal measurements of serum NT-proBNP and cardiothoracic ratio

There are a few children with isolated congenital complete atrioventricular block (ICCAVB) who do not require a pacemaker. We report a female infant born at 36 weeks by emergency cesarean section because of fetal heart rate abnormalities who was diagnosed as having ICCAVB. In accordance with the echocardiographic findings, we simultaneously measured the cardiothoracic ratio (CTR) by chest radiography and serum N-terminal pro-BNP (NT-proBNP) and have continued to follow her as an outpatient for about 8 years. CTR and NT-proBNP showed strong positive correlation (r=0.894, p<0.05). In such few children with ICCAVB as this patient, CTR measurement during their follow-up would be very useful to easily understand their cardiac load status.

Key Role of Pacing Site as Determinant Factor of Exercise Testing Performance in Pediatric Patients with Chronic Ventricular Pacing

Chronic right ventricular (RV) apical pacing has been associated with deterioration of functional capacity and chronotropic incompetence during exercise testing in children. The effects of alternative pacing site on exercise performance in pediatric population remain unknown. We evaluated the influence of ventricular pacing site on exercise capacity in pediatric patients with complete congenital atrioventricular block requiring permanent pacemaker therapy. Sixty-four children paced from RV apex (n = 26), RV midseptum (n = 15) and left ventricular (LV) apex (n = 23) were studied cross-sectionally. Treadmill exercise stress testing was performed according to modified Bruce protocol. LV apical pacing was associated with greater exercise capacity. In comparison with the other study groups, children with RV apical pacing showed significantly lower VO₂peak (37 ± 4.11; p = 0.003), O₂ pulse (8.78 ± 1.15; p = 0.006), metabolic equivalents (7 ± 0.15; p = 0.001) and exercise time (6 ± 3.28; p = 0.03). Worse values in terms of maximum heart rate (139 ± 8.83 bpm; p = 0.008) and chronotropic index (0.6 ± 0.08; p = 0.002) were detected in the RV apical pacing group although maximal effort (respiratory exchange ratio) did not differ among groups (p = 0.216). Pacing from RV apex (odds ratio 9.4; confidence interval 2.5-18.32; Wald 4.91; p = 0.0036) and low peak heart rate achieved (odds ratio 3.66; confidence interval 0.19-7.4; Wald 4.083; p = 0.015) predicted significantly decrease in exercise capacity. Duration of pacing, gender, VVIR mode, baseline heart rate and QRS duration had not significant impact on exercise capacity. The site of ventricular pacing has the major impact on exercise capacity in children requiring permanent pacing. Among the sites assessed, LV apex is related to the better exercise performance.

[Assessment of exercise capacity in congenital heart disease]

For many years, the treatment of congenital heart diseases has been a field in which, based on the seriousness of these conditions, treatment options were viewed with the greatest deference. This has conditioned, in many cases, the interventions to be undertaken in each. In this sense, exercise was thought to have a negative impact and thus the practise of almost any physical activity was limited. Although there has recently been a change in the paradigm with respect to exercise, this idea continues to hold sway. For many cardiopathies, the information obtained through a stress test is essential in order to implement and supervise an exercise program. The aim of this study is to analyze the parameters within the stress test which allow for an adequate stratification of the risk to subjects with congenital heart diseases who undertake exercise, as well as their values in accordance with the type of pathology, the gravity of such, and the age of the patients. Furthermore, these parameters will be analyzed for both their survival markers and the protocols that can best be adjusted for patients with these characteristic.

Dynamic interactions of gas exchange, body mass, and progressive exercise in children

PURPOSE

Cardiopulmonary exercise testing (CPET) is increasingly used as a biomarker of fitness in children. Maximal or peak values remain the most common variables obtained in CPET, but these physiologically challenging high-intensity work rates (WR) are often not achieved. We hypothesized that interactions of gas exchange, heart rate (HR), and WR CPET variables (slopes) could yield useful mechanistic and clinical insights that might enhance the clinical utility of CPET in children. We further hypothesized that the dependence of the slope on body mass could be predicted by the first-principle analysis of body size and physiological response.

METHODS

One hundred and sixty-nine healthy participants (8-18 yr old, body mass index <95th percentile, 82 females) underwent dual x-ray absorptiometry scan to estimate lean body mass (LBM) and performed a ramp-type progressive cycle ergometry exercise protocol with a breath-by-breath measurement of gas exchange. Linear regression was used to calculate the slopes among VO2, VCO2, VE, HR, and WR.

RESULTS

ΔWR/ΔHR (r = 0.87) and ΔVO2/ΔHR (r = 0.96) were strongly correlated with VO2peak, whereas ΔVO2/ΔWR (r = 0.42) and ΔVE/ΔVCO2 (r = -0.51) were mildly correlated with peak values. LBM was more highly correlated with those slopes predicted to be body size dependent (P < 0.0001) compared with total body mass.

CONCLUSIONS

The data largely supported our original hypotheses. Unlike peak or maximal values, which are derived from no more than a few data points at the end of a progressive exercise test, the CPET slopes were calculated from a much larger data set obtained throughout the test. An analysis of these slopes might ultimately prove useful clinically and in research studies when peak values are not achieved.

Functional capacity of patients with pacemaker due to isolated congenital atrioventricular block

BACKGROUND

Isolated congenital atrioventricular block (CAVB) is a rare condition with multiple clinical outcomes. Ventricular remodeling can occur in approximately 10% of the patients after pacemaker (PM) implantation.

OBJECTIVES

To assess the functional capacity of children and young adults with isolated CAVB and chronic pacing of the right ventricle (RV) and evaluate its correlation with predictors of ventricular remodeling.

METHODS

This cross-sectional study used a cohort of patients with isolated CAVB and RV pacing for over a year. The subjects underwent clinical and echocardiographic evaluation. Functional capacity was assessed using the six-minute walk test. Chi-square test, Fisher's exact test, and Pearson correlation coefficient were used, considering a significance level of 5%.

RESULTS

A total of 61 individuals were evaluated between March 2010 and December 2013, of which 67.2% were women, aged between 7 and 41 years, who were using PMs for 13.5 ± 6.3 years. The percentage of ventricular pacing was 97.9 ± 4.1%, and the duration of the paced QRS complex was 153.7 ± 19.1 ms. Majority of the subjects (95.1%) were asymptomatic and did not use any medication. The mean distance walked was 546.9 ± 76.2 meters and was strongly correlated with the predicted distance (r = 0.907, p = 0.001) but not with risk factors for ventricular remodeling. (Arq Bras Cardiol. 2014; [online].ahead print, PP.0-0) CONCLUSIONS: The functional capacity of isolated CAVB patients with chronic RV pacing was satisfactory but did not correlate with risk factors for ventricular remodeling.