Physical performance and physical activity in grown-up congenital heart disease

Aim

To review exercise performance and exercise habits in patients with congenital heart disease (CHD).

Background and methods

Physical exercise and physical activity has shown beneficial effects on the physical, psychological and social level in adult patients with cardiovascular disease. Favourable effects have also been documented in children with CHD. Exercise testing is preferentially performed on a treadmill in children, with the measurement of gas exchange.

Results

An overview of the literature showed that formal exercise testing has frequently documented reduced or suboptimal values for aerobic exercise performance in children with left-to-right shunts (atrial septal defect, ventricular septal defect), valvular heart disease and obstructive anomalies (aortic stenosis, pulmonary stenosis, coarctation of the aorta). Subnormal values for exercise tolerance have also been observed in patients with successfully repaired cyanotic heart disease (tetraology of Fallot, transposition of the great arteries, Fontan operation). An important contributing factor to the impaired exercise performance is the hypoactive lifestyle, as often observed in patients with CHD. This frequently results from parental or environmental overprotection.

Conclusion

These patients should be stimulated to be physically active, unless medical restriction is imposed. Fortunately, this represents only a small fraction of the total number of congenital heart defects for which sports participation is allowed.

Introduction

The beneficial effect of physical exercise on the cardiovascular system has been documented in many reports, both in healthy individuals as well as in patients with cardiovascular disease. Physically active individuals are known to have a lower incidence of ischaemic heart disease and a greater life expectancy [1].

Regular physical exercise has also been shown to have a beneficial long-term effect in patients with congenital heart disease (CHD) [2]. Despite this evidence a large number of patients are physically inactive because they are overprotected by their parents and their environment. The main reason for this attitude is the fear of sudden cardiac death, although only a small number of cases have been reported during physical exercise in patients with CHD [3].

On the basis of this experience, children with CHD are currently encouraged to be normally active and to participate in recreational sport activities, also after corrective cardiac surgery. These recommendations are based on the experience that physical exercise in children with CHD has favourable effects on the physical, psychological and social level, both for the children as well as their parents. In the majority of cases, these children do not need to participate in formal rehabilitation programmes. Even after corrective surgery, formal rehabilitation is mostly restricted to the hospitalization period, and consists mainly of chest physiotherapy (breathing exercises) and early mobilization. As soon as the children are discharged from the hospital, they are encouraged to resume their normal physical activities at home, and are stimulated to be as active as their healthy peers.

There are only a few contraindications to exercise for non-operated cardiac defects as for operated defects. The final decision to allow a child with CHD to participate in physical exercise should always be based on a full cardiological evaluation.

A few controlled studies in patients with CHD have shown that maximal exercise capacity can be improved after a period of physical training [4]. Cumulative medical experience has shown that the risk of physical exercise in patients with CHD is very low. Only a few defects (hypertrophic cardiomyopathy, congenital abnormalities of the coronary arteries, aortic stenosis …) have been associated with sudden cardiac death during physical activity. Fortunately, these anomalies represent only a small percentage of the total number of congenital heart defects for which sport participation is allowed.

Evaluation of children with congenital heart defects

To get an objective assessment of the functional capacity of children and adolescents with congenital heart defects, formal exercise testing should be performed with continuous measurement of gas exchange. Other methods such as history taking and questionnaires are inaccurate and not sensitive.

Exercise testing with gas exchange measurement allows a sensitive evaluation of the global cardiovascular function. Exercise tests can be performed on a cycle ergometer or preferentially for paediatric exercise testing on a treadmill. Exercise tests can be submaximal or maximal. Measurements of maximal exercise performance include the determination of maximal workload or maximal oxygen uptake on a cycle ergometer or treadmill, or the measurement of the maximal endurance time during treadmill exercise. Although the measurement of maximal oxygen uptake is a useful index and is considered to be the gold standard to assess aerobic fitness in adults, its application in children with congenital heart defects can have some limitations. Many children do not reach a true maximal oxygen uptake value because they are not motivated to exercise to the point of exhaustion. Therefore, measurements of maximal exercise performance should be complemented with submaximal exercise parameters that are motivation independent. Typical measurements are the determination of the ventilatory anaerobic threshold, which refers to the highest exercise intensity before which a disproportionate increase in carbon dioxide output and ventilation is found versus oxygen uptake, which is concomitant with the development of lactic acidosis during exercise. Other measurements, based on the heart rate response during exercise, in these patient groups are unreliable because many patients with congenital heart defects will show a reduced heart rate response (blunted heart rate response) during exercise [5]. This is not associated with a high value for maximal exercise performance as seen in normal individuals [6,7]. More recent parameters to assess aerobic exercise function include the study of oxygen uptake kinetics, such as the assessment of the oxygen deficit and time constants during exercise [8]. However these measurements require more sophisticated laboratory equipment such as fast-responding gas analysers or a mass spectrometer.

Assessment of the habitual level of physical activity in children with congenital heart disease

The reported hypoactive lifestyle in children with CHD, which is frequently present during daily life, is often the result of overprotection by the parents or relatives. In the majority of cases no medical restriction is imposed on the patients being fully active. A medically imposed restriction on competitive sports is justified for a number of pathologies, such as aortic stenosis, obstructive cardiomyopathy and malignant arrhythmias.

Despite this, previous studies on patients with a small left-to-right shunt showed a significantly decreased level of physical activity when assessed with a standard questionnaire [9–12]. This decreased activity level correlated with reduced aerobic exercise performance. This reduced activity level is considered to be incidental to the disorder. A low level of physical activity is also generally found in patients with unoperated aortic stenosis, but this results from a medical restriction on performing intensive and competitive exercise and sports.

Exercise performance capacity in some specific types of congenital heart disease

Left-to-right shunts Atrial septal defect

An atrial septal defect (ASD) causes right volume overload, increased pulmonary blood flow, possibly resulting in pulmonary hypertension if large ASD are untreated [13,14].

Children and adolescents with an unoperated ASD usually have a normal or only slightly impaired aerobic exercise capacity [2,15,16].

In patients with an unoperated ASD, the increase in cardiac output during exercise is smaller than the expected normal value and the maximal heart rate response during exercise has been shown to be lower than normal [7]. In children who undergo surgical closure of an ASD, the age at surgery has been shown to influence the exercise capacity. In a series of 24 patients who underwent surgical closure of an ASD [15], a normal value for the ventilatory threshold was found in children who underwent surgical closure before the age of 5 years, whereas a significantly lower than normal value was found in children operated after that age (up to 18 years of age).

Generally, abnormalities detected in children with unoperated or operated ASD are usually minor and do not result in major limitations of exercise performance. In adults, percutaneous closure results in improved exercise performance [17].

Ventricular septal defect

A ventricular septal defect (VSD) with associated left-to-right shunt causes left ventricular volume overload resulting in left ventricular dilatation. Patients with a VSD are characterized by a higher pulmonary to systemic flow ratio both at rest and during exercise. The relative shunt fraction has been shown to decrease with the increasing intensity of exercise [18]. Exercise performance assessed from measurements of maximal oxygen uptake, maximal endurance time on the treadmill, maximal work rate on the bicycle ergometer and maximal heart rate have been shown to be slightly decreased when compared with age-matched controls (e.g. 90.8 ± 1.6% for maximal oxygen uptake) [16,18,19]. We found in a consecutive series of 43 patients with unoperated VSD a reduced aerobic performance capacity, which correlated with a reduced level of daily physical activity [9]. Exercise capacity, assessed by the determination of the ventilatory threshold, was found to be slightly subnormal (86 ± 12% of normal). In a series of patients who were followed at the outpatient clinic, serial exercise testing showed that exercise capacity remained stable in this patient group (both operated and unoperated) when the patients were re-evaluated approximately 3 years after an intitial exercise test [10]. In patients with large VSD and pulmonary hypertension who underwent surgical closure of the VSD before 1 year of life, normal values were also found for aerobic exercise performance (> 90% of normal), 10.5 ± 3.4 years after surgery [20]. This shows that early surgical correction of the defect allows patients to become fully active and to reach normal values for aerobic exercise performance.

Valvular heart lesions and obstructive anomalies

Aortic stenosis

Patients with aortic stenosis have a reduced aerobic exercise performance. This reduced aerobic capacity has been shown to correlate with the gradient [21]. The reduced exercise performance in this patient group has been attributed to the inability to increase cardiac output adequately. The myocardial oxygen supply to the hypertrophied myocardium is also impaired, resulting in ECG changes in the ST segment during exercise [16]. An increase in the peak instantaneous gradient has been shown to correlate with an increase in ST segment changes [22,23]. After successful surgery, maximal exercise performance increases in the majority of the patients, with less incidence of ST segment changes during exercise [23].

Another factor that adversely affects exercise performance in patients with aortic stenosis is the medically imposed restriction on performing heavy (competitive) physical activity or isometric exercise.

Pulmonary valve disease

Pulmonary valve stenosis results in right ventricular pressure overload. As in aortic stenosis, a diminished increase in cardiac output occurs during exercise. During graded exercise testing the transvalvular pressure gradient may increase in pulmonary stenosis [24]. In mild cases (gradients for peak instantaneous gradient < 30 mmHg) values for the ventilatory anaerobic threshold have been found to be at or slightly below the lower limit of normal in patients with pulmonary stenosis [10]. In the Second Natural History Study of Congenital Heart Defects, the maximal exercise duration on the treadmill was slightly below the age-predicted levels in patients who had undergone previous valvulotomy [16]. In that series, patients with a fair or poor clinical status had a lower exercise performance level than those in a good clinical condition.

Coarctation of the aorta

In patients with successful operation for coarctation of the aorta, normal values for aerobic exercise capacity have been observed, even in those patients who develop heart failure in the neonatal period [25]. In the majority of patients a normal resting blood pressure has been reported. However, in some cases a residual or recurrent coarctation has been found. In these cases, a mild or moderate gradient and hypertensive blood pressure response can be observed [26]. Therefore exercise testing is useful in this patient group because it adds information to detect an abnormal blood pressure response during exercise. In a comparison between patients who underwent surgical repair early in life (less than 1 year of age) and those who underwent repair at a later age, a higher incidence of persistent exercise hypertension was observed in patients with a later repair (23%) versus those who were operated at an early age (7%) [27].

Cyanotic congenital heart disease

Tetralogy of Fallot

Although the majority of patients are usually well in daily life, formal exercise testing has repeatedly shown subnormal values for aerobic exercise performance, as assessed by determination of the maximal oxygen uptake or anaerobic threshold [6,28,29]. In a review of the literature, Wessel and Paul [30] reported an average value for maximum oxygen consumption, which amounted to 36 ml/min per kilogram or approximately 81% of the age-predicted normal value [30]. Abnormal values for aerobic exercise fitness and an inefficient ventilatory response to exercise have mostly been attributed to residual haemodynamic defects such as pulmonary valve incompetence [29,30] or chronotropic incompetence [6,7]. However, adequate relief of pulmonary valve incompetence or residual stenosis by using homograft insertion leads to a normalization of the aerobic exercise performance capacity in the majority of patients [31].

Transposition of the great arteries

In patients with transposition of the great arteries, two separate circulations exist. To survive, the Mustard or Senning procedures have been introduced. With this surgical intervention a baffle is placed in the atria to redirect systemic venous blood to the left ventricle and pulmonary artery and arterial blood to the right ventricle and aorta. In this atrial switch procedure, the right ventricle has to function as the systemic ventricle. Although many patients owe their survival to these procedures, in the majority of them reduced aerobic exercise performance has been found [32–34]. This decrease in exercise performance is related to filling abnormalities or diastolic dysfunction caused by the baffle procedure. The baffle becomes the limiting factor for filling the left ventricle. Late complications are baffle obstruction and right ventricular dysfunction. The operation of choice is currently the arterial switch procedure in which the aorta and pulmonary artery are exchanged at the cardiac base, with transplantation of the coronary arteries. In patients with an arterial switch operation a normal or near normal exercise performance capacity has been found 8 ± 2.9 years after surgery [33]. Long-term follow-up is not yet available.

Fontan operation

In a number of conditions there may be a single functioning ventricle, such as in tricuspidatresia. To survive, a communication between the caval veins and the pulmonary artery is made, bypassing the right ventricle. This means that there is no effective right ventricular pump. Although the survival of these patients is dramatically improved, the majority of them have a strikingly reduced exercise tolerance [10,35–37]. In a study by Driscoll et al. [37] the maximal exercise performance in this patient group amounted to only 37% of the normal control value.

Exercise recommendations in patients with congenital heart disease

As it is impossible to predict how much energy will be expended by an individual patient when practising exercise or sports, some general guidelines can be formulated for different pathologies. Recommendations are generally based on clinical experience, which has shown that physical exercise has beneficial effects on the physical, social and psychological level in children with CHD. A classification of the intensity of sports has been made by the American College of Cardiology [38]. Exercise intensity is classified as low, moderate and high dynamic with a low, moderate and high static component. Detailed tables with typical sports have been published elsewhere [38]. Exercise recommendations as formulated by the European Society of Cardiology are presented in Table 1. These recommendations are intended to support the clinician and to offer some guidelines in making clinical decisions. An easy rule to define a safe exercise intensity is the use of the ‘talk test'. This means the children should exercise at an intensity level at which they still are able to talk to their peers or parents during exercise.

References