The role of chronotropic impairment during exercise after the Mustard operation.

To better understand the role of chronotropic impairment on exercise performance after the atrial switch (Mustard) operation, 20 patients who had undergone this operation for uncomplicated d-transposition of the great arteries exercised to maximal volition using a 1 min incremental treadmill protocol. Heart rate, oxygen consumption, carbon dioxide production and minute ventilation were monitored continuously. Two-dimensional echocardiograms were obtained before testing to calculate the right ventricular inflow volume indexed to body surface area. All patients achieved maximal aerobic capacity based on their ventilatory patterns and respiratory exchange ratio. Maximal heart rate was reduced (175 beats/min; 87% of predicted for age) and maximal oxygen consumption was decreased (31 ml/kg per min; 75% of predicted for age and gender). There was no correlation between maximal oxygen consumption and maximal heart rate. Right ventricular volume index, however, had a significant inverse correlation with maximal heart rate (r = -0.62, p less than 0.005). There was no correlation between right ventricular volume index and heart rate at rest. These results suggest that decreased maximal oxygen consumption in patients after the Mustard procedure is not a result of chronotropic impairment. Right ventricular dilation may be a compensatory response to chronotropic impairment.

Rapid ventricular pacing in dogs with right ventricular outflow tract obstruction: insights into a mechanism of sudden death in postoperative tetralogy of Fallot.

OBJECTIVES: We explored the hypothesis that residual outflow tract obstruction and ventricular hypertrophy associated with rapid ventricular rhythm contribute to sudden death, in part because they result in humoral or hemodynamic changes that predispose to ventricular fibrillation, such as increased catecholamine release or decreased coronary flow, or both. BACKGROUND: Ventricular arrhythmia after surgical repair of tetralogy of Fallot has been associated with sudden death, particularly in patients with residual right ventricular hypertension. However, the mechanisms by which sudden death occurs remain unclear. METHODS: Seven awake, unanesthetized mature beagles with chronically elevated right ventricular pressure (high pressure group: right ventricular/left ventricular systolic pressure ratio > 0.5) were compared with six beagles with low right ventricular pressure at rest and at the end of 5 min of ventricular pacing at 240 beats/min (low pressure group). RESULTS: In the high pressure group, cardiac output decreased during ventricular pacing (compared with sinus rhythm) from 304 +/- 21 to 218 +/- 21 ml/min per kg (p < 0.01) and plasma norepinephrine increased substantially from 673 +/- 64 to 1,047 +/- 92 pg/ml (p < 0.01). Comparable changes were not observed in the low pressure group. Plasma epinephrine levels were similar in both groups at rest and did not change with pacing. Postpacing norepinephrine levels from both groups correlated positively with both right ventricular systolic and diastolic pressure at rest and correlated negatively with the change in cardiac output from rest to pacing. Regional right ventricular myocardial blood flow increased with pacing in the low pressure group, whereas in the high pressure group it was increased at rest and did not increase further with pacing. CONCLUSION: During ventricular pacing, dogs with right ventricular outflow tract obstruction and high right ventricular pressure had a decrease in cardiac output and an increase in plasma norepinephrine, coupled with a loss of right ventricular myocardial blood flow reserve. Similar changes may occur in postoperative patients with similar hemodynamics and tachyarrhythmia and could contribute to the occurrence of ventricular fibrillation and sudden death.

Quantification of myocardial blood flow and flow reserve in children with a history of Kawasaki disease and normal coronary arteries using positron emission tomography.

OBJECTIVES: The purpose of this investigation was to determine whether myocardial blood flow and flow reserve, based on quantitative measurements derived from positron emission tomographic (PET) imaging, would be globally impaired in children with a previous history of Kawasaki disease and normal epicardial coronary arteries. BACKGROUND: Kawasaki disease is an acute inflammatory process of the arterial walls that results in panvasculitis in early childhood. Children with a history of Kawasaki disease and normal epicardial coronary arteries were previously considered to have normal coronary flow reserve. However, recent studies have reported exercise-induced regional perfusion abnormalities on single-photon positron emission tomographic (SPECT) imaging. METHODS: We assessed myocardial blood flow and flow reserve at rest and during adenosine stress with nitrogen-13 ammonia and PET in 10 children with a history of Kawasaki disease and in 10 healthy young adult volunteers. All children had acute Kawasaki disease 4 to 15 years before the PET study. None of the children had epicardial coronary artery abnormalities at the acute stage of the disease or during follow-up, as assessed by echocardiography. RESULTS: Rest blood flows normalized to the rate-pressure product, an index of cardiac work, were similar in both the patients with Kawasaki disease and healthy adult volunteers (82 +/- 14 vs. 77 +/- 16 ml/100 g per min [mean +/- SD], p = NS). However, hyperemic blood flows were significantly lower in the patients with Kawasaki disease than in the control subjects (263 +/- 64 vs. 340 +/- 57 ml/100 g per min, p = 0.01). As a result, estimates of myocardial flow reserve were lower in the patients with Kawasaki disease than in the healthy young adult volunteers (3.2 +/- 0.7 vs. 4.6 +/- 0.9, p = 0.003). In addition, total coronary resistance was higher in the patients with Kawasaki disease than in the healthy adult volunteers (33 +/- 11 vs. 24 +/- 5 mm Hg/ml per g per min, p = 0.04). Quantitative analysis of perfusion images demonstrated no evidence of regional perfusion abnormalities. CONCLUSIONS: Children with a previous history of Kawasaki disease and normal epicardial coronary arteries exhibit normal rest myocardial blood flows but reduced hyperemic flows and flow reserve. The abnormal hyperemic blood flows and flow reserve suggest an impaired vasodilatory capacity, possibly due to residual damage of the coronary microcirculation.

Impact of early ventricular unloading on exercise performance in preadolescents with single ventricle Fontan physiology.

OBJECTIVES: We sought to determine if early ventricular volume unloading improves aerobic capacity in patients with single ventricle Fontan physiology. BACKGROUND: Surgical strategies for patients with single ventricle include intermediate staging or early Fontan completion to reduce the adverse affects of prolonged ventricular volume load. The impact of this strategy on exercise performance has not been evaluated. METHODS: Retrospectively, we reviewed the exercise stress test results of all preadolescents with single ventricle Fontan physiology. "Volume unloading" was considered to have occurred at the time of bidirectional cavopulmonary anastomosis or at the time of Fontan surgery in those patients who did not undergo intermediate staging. Potential predictors of aerobic capacity were analyzed using multivariate regression. RESULTS: The patients (n = 46) achieved a mean percentage predicted of maximal oxygen consumption (VO2max) of 76.1% +/- 21.1%. The mean age at the time of volume unloading was 2.7 +/- 2.4 years, and the mean age at testing was 8.7 +/- 2 years. Intermediate staging was performed in 16 of 46 patients (35%). In multivariate analysis, younger age at volume unloading was associated with increased aerobic capacity (p = 0.003). Other variables were not predictive. The subgroup of patients who underwent volume unloading before two years of age achieved a mean percentage predicted VO2max of 88.6% +/- 24.1%. CONCLUSIONS: Preadolescents with single ventricle who undergo volume unloading surgery at an early age demonstrate superior aerobic capacity compared with those whose surgery is delayed until a later age.

Exercise capacity and incidence of myocardial perfusion defects after Kawasaki disease in children and adolescents.

OBJECTIVES: This study evaluated exercise performance and myocardial perfusion during exercise in patients with Kawasaki disease who had a broad spectrum of residual coronary abnormalities. BACKGROUND: Reports of exercise performance after Kawasaki disease have generally included a small number of patients evaluated by various protocols, frequently with incomplete data. Myocardial perfusion studies have usually been limited to those using pharmacologically induced coronary vasodilation. Therefore, to our knowledge there has not been a large study directly correlating exercise performance, electrocardiographic (ECG) changes and myocardial perfusion imaging. METHODS: Forty-six patients were classified into three groups on the basis of coronary artery status: group 1 (n = 27) had no objective evidence of coronary artery lesions; group 2 (n = 11) had resolved aneurysms; group 3 (n = 8) had persistent coronary aneurysms. All patients underwent exercise testing with monitoring of ECG changes and oxygen consumption. Single-photon emission computed tomographic imaging was performed at rest and during peak exercise using technetium-99m sestamibi. RESULTS: Maximal oxygen consumption was within normal limits and was similar for all three groups. Five patients had mild ST segment changes at peak exercise. Two of these patients had stress-induced perfusion defects. Myocardial perfusion defects were present in 37% of patients in group 1, 63% in group 2 and 100% in group 3. Perfusion defects corresponded to the coronary artery lesion site in all but three patients. CONCLUSIONS: Maximal oxygen consumption is normal after Kawasaki disease regardless of coronary artery status. Stress-induced perfusion defects are frequent even in the absence of coronary abnormalities and are common in the absence of ST segment changes suggestive of ischemia.

Design and baseline characteristics for the ACE Inhibitor After Anthracycline (AAA) study of cardiac dysfunction in long-term pediatric cancer survivors.

PURPOSE: The ACE Inhibitor After Anthracycline (AAA) study is a randomized, double-blind, controlled clinical trial comparing enalapril with placebo to determine whether treatment can slow the progression of cardiac decline in patients who screen positive for anthracycline cardiotoxicity. METHODS: The primary outcome measure is the rate of decline, over time, in maximal cardiac index (in liters per minute per meters squared) at peak exercise; the secondary outcome measure is the rate of increase in left ventricular end systolic wall stress (in grams per centimeters squared). Patients >2 years off therapy and <4 years from diagnosis, aged 8 years and older, were eligible if they had received anthracyclines and had at least one cardiac abnormality identified at any time after anthracycline exposure. RESULTS: A total of 135 patients were randomized to enalapril or placebo. Baseline characteristics were similar across treatment groups. CONCLUSIONS: The AAA study will provide important information concerning the efficacy of using angiotensin-converting enzyme inhibitors to offset the effects of late anthracycline cardiotoxicity.

Exercise performance after the arterial switch operation for D-transposition of the great arteries.

Early- and intermediate-term results of the arterial switch operation for D-transposition of the great arteries (D-TGA) are encouraging. However, questions remain about the long-term outcome for these patients, especially with regard to exercise performance. Preliminary studies have demonstrated normal endurance time on treadmills. However, data regarding aerobic capacity and cardiopulmonary function are lacking. We report the cardiopulmonary performance of 22 school-age patients with D-TGA who underwent the arterial switch operation. Outcome variables included maximal oxygen consumption (VO2), maximal cardiac index, and peak heart rate. Patient and procedure-related variables were assessed for their association with outcome variables using linear and logistic regression. The mean values of maximal VO2 (113 +/- 19% predicted) and maximal cardiac index (96 +/- 18% predicted) were within normal limits for the pediatric population. Although the mean peak heart rate for the entire group (184 +/- 14 beats/min) was within normal limits, there were 7 subjects (32%) with chronotropic impairment. Significant ST-segment depression was seen in 2 subjects (9%). In regression analysis, surgery subsequent to the arterial switch was associated with lower maximal cardiac index (p = 0.01). Other variables were not significantly associated with maximal VO2, maximal cardiac index, and peak heart rate. In particular, chronotropic impairment was not significantly associated with maximal VO2 or maximal cardiac index. These findings demonstrate that cardiopulmonary performance during exercise is excellent after the arterial switch operation. The finding of ST-segment depression in some subjects supports the role of formal exercise testing in those patients participating in vigorous athletic activities.

Cardiopulmonary performance at rest and exercise after repair of total anomalous pulmonary venous connection.

Although long-term evaluations of patients after repair of total anomalous pulmonary venous connection have generally shown them to be clinically asymptomatic, assessment of their cardiovascular and pulmonary systems have been limited. Residual cardiopulmonary abnormalities undetected at rest may result in impaired function during exercise. To evaluate this hypothesis 9 patients underwent exercise testing after repair of total anomalous pulmonary venous connection. Pulmonary function testing was performed before exercise. Patients exercised using a 1-minute incremental bicycle or treadmill protocol monitoring heart rate, oxygen consumption, carbon dioxide production and minute ventilation. Compared with healthy children, the study patients had reduced maximal oxygen consumption and reduced oxygen consumption at ventilatory anaerobic threshold. Chronotropic response was impaired in 5 patients. Resting pulmonary functions showed evidence of mild restrictive lung disease. Breathing reserve was within normal limits. It is concluded that (1) aerobic capacity is mildly reduced after repair of total anomalous pulmonary venous connection, (2) chronotropic impairment is a common occurrence, and (3) pulmonary testing suggests mild restrictive lung disease that does not compromise exercise performance.

Prolonged extracorporeal membrane oxygenation as a bridge to cardiac transplantation.

Cardiac transplantation provides the best option for neonates with congenital heart disease that is not amenable to surgical repair or palliation. The scarcity of suitable organs for this group has resulted in prolonged waiting times; many infants die awaiting transplantation. We present the case of a newborn with severe Ebstein's anomaly and low cardiac output who was supported with extracorporeal membrane oxygenation for 1,126 hours, until an appropriate organ became available.

Quantitative QRS changes with exercise in children and adolescents.

Exercise-induced changes in QRS voltage have been used to evaluate left ventricular function in adults, children, and adolescents. The purpose of this study was to investigate changes in QRS voltage with exercise in a population of healthy children and adolescents. Eighty-two normal subjects (61 boys and 21 girls) ages 4-18 yr (mean = 12 yr) had maximal exercise testing performed according to Bruce treadmill protocol. Subjects were exercised to exhaustion with continuous monitoring of a VF, V2, and V5. Twelve lead electrocardiograms were recorded at each stage of exercise. Maximum heart rate obtained was 180-212 (mean = 197). Resting and exercise QRS voltages were measured in a VF and V5 averaged over five consecutive QRS complexes. From 12 lead electrocardiographic recordings, frontal and horizontal QRS vectors were calculated. There was no change in the frontal plane QRS vector with exercise (P = 0.4). There was a posterior change in horizontal vector at peak exercise (P less than 0.001) with a mean shift of 14.5 degrees. The R wave voltage diminished in V5 (P less than 0.001, mean decrease of 0.39 mV). However, V5 R wave voltage was increased or unchanged in 23 of the 61 boys and in three of the 21 girls. In males 10 yr of age or younger, 72% had no change or increased R wave voltage compared with 21% for males older than 10 yr (P less than 0.05). These findings are clearly different from the QRS changes with exercise in healthy adults.

Recommendations for physical activity, recreation sport, and exercise training in paediatric patients with congenital heart disease: a report from the Exercise, Basic & Translational Research Section of the European Association of Cardiovascular Prevention and Rehabilitation, the European Congenital Heart and Lung Exercise Group, and the Association for European Paediatric Cardiology.

All children have a natural need to move, play, and perform activities. Physical activity is necessary for optimal physical, emotional, and psychosocial development for healthy children as well as children with congenital heart disease (CHD). In this paper we provide recommendations for physical activity, recreational sport, and exercise training in children and adolescents with CHD. In general, children with CHD should be advised to comply with public health recommendations of daily participation in 60 min or more of moderate-to-vigorous physical activity that is developmentally appropriate and enjoyable and involves a variety of activities. While all patients with CHD can participate and benefit from physical activity and exercise, those with specific lesions or complications may require counselling regarding precautions and recommendations.

Exercise performance and quality of life following surgical repair of anomalous aortic origin of a coronary artery in the pediatric population.

OBJECTIVE: We sought to evaluate exercise performance and quality of life in children after surgical repair of anomalous aortic origin of a coronary artery with an interarterial course. METHODS: Patients who had surgery from October 2001 to January 2007 were eligible for inclusion. Exercise performance and quality of life were prospectively assessed by maximal exercise tests and age-appropriate questionnaires, respectively. We used t tests to compare pre- and postoperative exercise data and quality-of-life scores to published normative data. We performed linear regression analyses to assess associations between demographic, anatomic, and exercise variables and quality-of-life score. RESULTS: Of 25/27 patients, 64% were boys, 68% had anomalous right coronary, 32% were asymptomatic. Average age at surgery was 10.8 (+/-4.1) years; median follow-up was 14.5 (2 to 48) months. Postoperative percent-predicted exercise values were: peak heart rate 97 (+/-6), working capacity 91 (+/-15), maximal oxygen consumption 82 (+/-16). In those who had preoperative exercise testing (n = 11), resting and maximal heart rates decreased significantly without significant change in exercise performance. Average child quality of life was 85/100 (+/-13) and parent-proxy 88 (+/-11) compared with normal scores of 83 (+/-15) and 88 (+/-12), respectively. CONCLUSION: There is mild chronotropic impairment in children and adolescents following anomalous coronary artery repair without a decline in exercise performance. This does not appear to impair their overall quality of life. Because long-term effects on heart rate, exercise performance, and quality of life are unknown, serial exercise tests should be included as routine care of these patients.

The effects of rate responsive pacing on exercise performance in the postoperative univentricular heart.

Following the Fontan operation for definitive palliation of the univentricular heart, sinus node dysfunction, and/or atrioventricular block requiring pacemaker therapy is common. In previous studies ventricular rate responsive pacing (VVI,R) resulted in improved exercise performance over VVI pacing in anatomically normal hearts with either sinus node disease or atrioventricular block. In this study, the usefulness of both VVI,R and DDD,R pacing are evaluated in the postoperative univentricular heart following the Fontan operation. Eight postoperative Fontan patients with sinus node disease or atrioventricular block underwent exercise testing using a treadmill protocol. Six patients had single chamber ventricular pacemakers and two patients had dual chambered rate responsive pacemakers. Median age at exercise testing was 14 years. Patients were tested in the VVI, VVI,R, and DDD,R modes acting as their own controls. Heart rate, work rate, oxygen consumption, and respiratory exchange ratio were monitored continuously. Heart rate was significantly increased in the rate responsive modes compared to the VVI mode. In spite of the significant increase in heart rate, there was no change in maximal work rate or oxygen consumption. There was also no significant change in oxygen consumption at ventilatory anaerobic threshold. From these data we would conclude that VVI,R pacing in postoperative univentricular hearts does not result in improved exercise performance and that further study with DDD,R pacing is needed to determine its usefulness in this group of patients.

Failure of rate responsive ventricular pacing to improve physiological performance in the univentricular heart.

The physiological efficacy of single chamber, rate responsive ventricular pacing (VVIR) is unknown for symptomatic patients following the Fontan procedure for univentricular hearts. A total of six postoperative children, ages 6-21 years (mean 13), with symptomatic bradycardia requiring pacing therapy, underwent comparative treadmill exercise testing in randomized fixed rate (VVI) and VVIR pacing modes. In all instances, implanted activity pulse generators (Medtronic Model 8403) were programmed to identical age-appropriate low paced rates during VVI and VVIR modes with the upper rate response at 150 ppm. All studies were performed at least 2 weeks apart. Physiological values of heart rate, blood pressure, work rate (watts), oxygen consumption (VO2), carbon dioxide production (VCO2), and respiratory exchange ratio (RER) were monitored continuously during each test using a 1 minute incremental treadmill protocol. Ventilatory anaerobic threshold (VAT) was calculated from VO2, VCO2, and minute ventilation. The results demonstrated that although there was a significant increase in paced heart rate per minute throughout exercise (P less than 0.01) with VVIR pacing, maximum watts, VO2, and VAT remained unchanged. These findings indicate that in spite of an improved chronotropic response to exercise, children with univentricular hearts following the Fontan procedure continue to demonstrate altered hemodynamics which negate potential benefits of VVIR pacing.

Exercise performance in tetralogy of Fallot: the impact of primary complete repair in infancy.

Primary complete repair (PCR) of tetralogy of Fallot (TOF) is now routinely performed in infancy. Although operative results are excellent, the impact on exercise performance is incompletely understood. We reviewed data of all children with TOF who underwent PCR at our institution and had subsequent maximal cycle ergometer exercise testing between January 1995 and December 2000. Of the 193 patients with TOF who underwent PCR, 57 (30%) underwent exercise testing; maximal tests were available for 50 of 57 (88%). Exercise performance of subjects who underwent PCR at <1 year of age was compared to that of those who underwent repair at >l year of age. The median age at PCR was 10.9 months; 28 subjects (56%) underwent PCR in infancy (<1 year). A transannular incision was employed in the repair in 41 subjects (82%). The mean age at exercise testing was 12.5 +/- 3.2 years. The mean maximal VO2 was 94.9 +/- 18.8% predicted and the mean maximal work rate was 98.0 +/- 20.8% predicted. In multivariate analysis PCR in infancy (age <1 year) was not associated with maximal VO2, peak work rate, peak heart rate, or arrhythmias. Only older age at testing and male gender were significantly associated with higher maximal VO2 (p = 0.005 and p = 0.002, respectively). Intermediate-term exercise performance in subjects who undergo PCR of TOF in early childhood is near normal. Performing PCR in the first year of life does not impact subsequent exercise performance.

Cardiopulmonary performance during exercise in patients with repaired tetralogy of Fallot with absent pulmonary valve.

In patients with tetralogy of Fallot and absent pulmonary valve, the dilated pulmonary arteries sometimes result in bronchial compression and pulmonary symptoms due to airway obstruction, recurrent pulmonary infection, and development of bronchiectasis. After complete intracardiac repair, residual pulmonary disease may be expected to result in impaired cardiopulmonary performance during exercise. To assess this hypothesis, nine patients with tetralogy of Fallot and absent pulmonary valve underwent exercise testing and were compared to 38 patients with tetralogy of Fallot repaired using a transannular patch. All patients were exercised to maximum volition using a 1 minute incremental treadmill protocol with monitoring of pulmonary functions and expired gases. Maximal heart rate, maximal oxygen consumption, oxygen consumption at anaerobic threshold, and maximal respiratory exchange ratio were similar for the two groups. There was no significant difference for ventilation and gas exchange parameters at rest or at maximal exercise, and values for both groups were below the predicted normal for healthy subjects. Breathing reserve, however, did tend to be somewhat lower in the group with tetralogy of Fallot with absent pulmonary valve. In summary, despite significant preoperative symptoms, cardiopulmonary performance during exercise in patients with tetralogy of Fallot and absent pulmonary valve is similar to patients with tetralogy of Fallot repaired with a transannular patch.