Exercise Physiology and Testing in Adult Patients with Congenital Heart Disease

Cardiopulmonary Exercise Testing after Surgical Repair of Tetralogy of Fallot-Does Modality Matter?

BACKGROUND

Despite a successful repair of tetralogy of Fallot (rToF) in childhood, residual lesions are common and can contribute to impaired exercise capacity. Although both cycle ergometer and treadmill protocols are often used interchangeably these approaches have not been directly compared. In this study we examined cardiopulmonary exercise test (CPET) measurements in rToF.

METHODS

Inclusion criteria were clinically stable rToF patients able to perform a cardiac magnetic resonance imaging (CMR) and two CPET studies, one on the treadmill (incremental Bruce protocol) and one on the cycle ergometer (ramped protocol), within 12 months. Demographic, surgical and clinical data; functional class; QRS duration; CMR measures; CPET data and international physical activity questionnaire (IPAQ) scores of patients were collected.

RESULTS

Fifty-seven patients were enrolled (53% male, 20.5 ± 7.8 years at CPET). CMR measurements included a right ventricle (RV) end-diastolic volume index of 119 ± 22 mL/m2, a RV ejection fraction (EF) of 55 ± 6% and a left ventricular (LV) EF of 56 ± 5%. Peak oxygen consumption (VO2)/Kg (25.5 ± 5.5 vs. 31.7 ± 6.9; p < 0.0001), VO2 at anaerobic threshold (AT) (15.3 ± 3.9 vs. 22.0 ± 4.5; p < 0.0001), peak O2 pulse (10.6 ± 3.0 vs. 12.1± 3.4; p = 0.0061) and oxygen uptake efficiency slope (OUES) (1932.2 ± 623.6 vs. 2292.0 ± 639.4; p < 0.001) were significantly lower on the cycle ergometer compared with the treadmill, differently from ventilatory efficiency (VE/VCO2) max which was significantly higher on the cycle ergometer (32.2 ± 4.5 vs. 30.4 ± 5.4; p < 0.001). Only the VE/VCO2 slope at the respiratory compensation point (RCP) was similar between the two methodologies (p = 0.150).

CONCLUSIONS

The majority of CPET measurements differed according to the modality of testing, with the exception being the VE/VCO2 slope at RCP. Our data suggest that CPET parameters should be interpreted according to test type; however, these findings should be validated in larger populations and in a variety of institutions.

The oxygen uptake efficiency slope in adults with CHD: group validity

The maximal oxygen uptake (V02 max) is a well-validated measure of cardiorespiratory function that is calculated during a maximal cardiopulmonary exercise test. V02 max enables physicians to objectively assess cardiopulmonary function to aid in decision-making for patients with CHD. A significant proportion of these patients however are unable to achieve a maximal exercise test, and as such, there is a need for reliable submaximal predictors of cardiorespiratory reserve.The oxygen uptake efficiency slope represents a measure of how effectively oxygen is extracted from the lungs and taken into the body and can be calculated from a submaximal exercise test. Its reliability as a predictor of cardiorespiratory reserve has been validated in various patient populations, but there is limited evidence for its validity in adult patients with CHD.Retrospective analysis of cardiopulmonary exercise test data in 238 consecutive patients with CHD who completed a maximal cardiopulmonary exercise test at our tertiary cardiology centre demonstrated a strong correlation between peak V02 and the oxygen uptake efficiency slope (0.936). A strong correlation with peak V02 was also demonstrated when oxygen uptake efficiency slope was calculated at ventilatory anaerobic threshold (OUESVAT), 75% (OUES75), and 90% (OUES90) of the test (0.833, 0.905, 0.927 respectively).In adult patients with CHD who are unable to complete a maximal cardiopulmonary exercise test, the oxygen uptake efficiency slope is a reliable indicator of cardiopulmonary fitness which correlates strongly with peak V02 at or beyond the ventilatory anaerobic threshold. Further research is required to validate the findings in patients with less common anatomies and to assess the relationship between the oxygen uptake efficiency slope and mortality.

The Use of Stress Cardiovascular Imaging in Pediatric Population

Although not frequent in the pediatric population, ischemia could occur in children due to several congenital and acquired disease. Stress imaging is key for the non-invasive evaluation of myocardial abnormalities and perfusion defect in this clinical setting. Moreover, beyond ischemia assessment, it can provide complementary diagnostic and prognostic information in valvular heart disease and cardiomyopathies. When performed using cardiovascular magnetic resonance, it could detect, in addition, myocardial fibrosis and infarction, increasing the diagnostic yield. Several imaging modalities are currently available for the evaluation of stress myocardial perfusion. Advances in technologies have also increased the feasibility, safety and availability of these modalities in the pediatric age group. However, despite the established role of stress imaging and its increasing use in daily clinical practice, there are currently no specific guidelines, and little data are available in the literature on this topic. The aim of this review is to summarize the most recent evidence on pediatric stress imaging and its clinical application with a focus on the advantages and limitations of each imaging modality currently available.

Mismatch between self-estimated and objectively assessed exercise capacity in patients with congenital heart disease varies in regard to complexity of cardiac defects

AIM

Regular evaluation of physical capacity takes a crucial part in long-term follow-up in patients with congenital heart disease (CHD). This study aims to examine the accuracy of self-estimated exercise capacity compared to objective assessments by cardiopulmonary exercise testing in patients with CHD of various complexity.

METHODS

We conducted a single centre, cross-sectional study with retrospective analysis on 382 patients aged 8-68 years with various CHD who completed cardiopulmonary exercise tests. Peak oxygen uptake was measured. Additionally, questionnaires covering self-estimation of exercise capacity were completed. Peak oxygen uptake was compared to patient's self-estimated exercise capacity with focus on differences between complex and non-complex defects.

RESULTS

Peak oxygen uptake was 25.5 ± 7.9 ml/minute/kg, corresponding to 75.1 ± 18.8% of age- and sex-specific reference values. Higher values of peak oxygen uptake were seen in patients with higher subjective rating of exercise capacity. However, oxygen uptake in patients rating their exercise capacity as good (mean oxygen uptake 78.5 ± 1.6%) or very good (mean oxygen uptake 84.8 ± 4.8%) was on average still reduced compared to normal. In patients with non-complex cardiac defects, we saw a significant correlation between peak oxygen uptake and self-estimated exercise capacity (spearman-rho -0.30, p < 0.001), whereas in patients with complex cardiac defects, no correlation was found (spearman-rho -0.11, p < 0.255).

CONCLUSION

The mismatch between self-estimated and objectively assessed exercise capacity is most prominent in patients with complex CHD.Registration number at Charité Universitätsmedizin Berlin Ethics Committee: EA2/106/14.

Six minute walk distance and reference values in healthy Italian children: A cross-sectional study

The 6-minute walking test (6MWT) is a simple assessment tool to evaluate exercise capacity. The result of the test is the distance that a subject can walk at a constant and normal pace within 6 minutes (6MWD) and reflects the aerobic/fitness performance related to walking function. Use of 6MWT has been relevant to assess exercise tolerance either in healthy children or in patients with, heart, lung and metabolic diseases. Our aim was to find 6MWT reference values in healthy Italian children. The 6MWT was performed in 5614 children aged 6–11 years recruited from primary Italian schools. Age related reference percentiles of the covered distance were gender-modeled. A linear and quadratic regression model was used to predict 6MWT performance. Males walked longer distances than females, respectively 598.8±83.9 m vs 592.1±77.6 m (p = 0.0016). According to the regression analysis, 6MWD was positively related to age, gender and height, while it was negatively related to body weight [(6MWD = -160.16 + 93.35× age (years) -4.05× age²(years) +7.34× gender (m) +2.12× weight (kg) −2.50× height (cm)]. Reference values were established for the 6MWT in healthy children. The age related 6MWD percentiles provided a useful tool in the assessment of capacity in 6–11 year children, in fact they may be helpful to evaluate the effect of a given treatment or rehabilitation program and represent a feasible measure as to prevention within the primary school context. It was found a substantial difference from other countries for 6mwd values. In our study, factors such as age, weight and height were relevant for the prediction of 6MWD, similarly to other studies. Therefore, these variables should be taken into account in context of exercise performance.

Cardiopulmonary Exercise Testing for Surgical Risk Stratification in Adults with Congenital Heart Disease

Adult congenital heart disease (ACHD) patients often require repeat cardiothoracic surgery, which may result in significant morbidity and mortality. Currently, there are few pre-operative risk assessment tools available. In the general adult population, pre-operative cardiopulmonary exercise testing (CPET) has a predictive value for post-operative morbidity and mortality following major non-cardiac surgery. The utility of CPET for risk assessment in ACHD patients requiring cardiothoracic surgery has not been evaluated. Retrospective chart review was conducted on 75 ACHD patients who underwent CPET less than 12 months prior to major cardiothoracic surgery at Children's Hospital of Wisconsin. Minimally invasive procedures, cardiomyopathy, acquired heart disease, single ventricle physiology, and heart transplant patients were excluded. Demographic information, CPET results, and peri-operative surgical data were collected. The study population was 56% male with a median age of 25 years (17-58). Prolonged post-operative length of stay correlated with increased ventilatory efficiency slope (V_E/[Formula: see text] slope) (P = 0.007). Prolonged intubation time correlated with decreased peak HR (P = 0.008), decreased exercise time (P = 0.002), decreased heart rate response (P = 0.008) and decreased relative peak oxygen consumption (P = 0.034). Post-operative complications were documented in 59% of patients. While trends were noted between post-operative complications and some measurements of exercise capacity, none met statistical significance. Future studies may further define the relationship between exercise capacity and post-operative morbidity in ACHD patients.

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.

A Randomized Trial Comparing Cardiac Rehabilitation to Standard of Care for Adults With Congenital Heart Disease

Background:

Cardiac rehabilitation (CR) improves exercise capacity and quality of life while reducing mortality in adults with acquired heart disease. Cardiac rehabilitation has not been extensively studied in adults with congenital heart disease (CHD).

Methods:

We performed a prospective, randomized controlled trial (NCT01822769) of a 12-week clinical CR program compared with standard of care (SOC). Participants were ≥16 years old, had moderate or severe CHD, had O2 saturation ≥92%, and had peak O2 consumption ([Formula: see text]) < 80% predicted. We assessed exercise capacity, physical activity, quality of life, self-reported health status, and other variables at baseline and after 12 weeks. The prespecified primary end point was change in [Formula: see text].

Results:

We analyzed data on 28 participants (aged 41.1 ± 12.1 years, 50% male), 13 randomized to CR and 15 to SOC. [Formula: see text] averaged 16.8 ± 3.8 mL/kg/min, peak work rate = 95 ± 28 W, and median Minnesota Living with Heart Failure Questionnaire (MLHFQ) score = 27 (interquartile range: 11-44). Cardiac rehabilitation participants were older (48 ± 9 years vs 36 ± 12 years; P = .01), but there were no significant between-group differences in other variables. There were no adverse events related to CR. [Formula: see text] increased in the CR group compared with SOC (+2.2 mL/kg/min, 95% confidence interval: 0.7-3.7; P = .002, age-adjusted +2.7 mL/kg/min; P = .004); there was a nonsignificant improvement in work rate (+8.1 W; P = .13). Among the 25 participants with baseline MLHFQ > 5, there was a clinically important >5-point improvement in 72.7% and 28.6% of CR and SOC participants, respectively ( P = .047). Cardiac rehabilitation was also associated with improved self-assessment of overall health ( P < .04).

Conclusions:

Cardiac rehabilitation is safe and is associated with improvement in aerobic capacity and self-reported health status compared with SOC in adults with CHD.

The Role of Cardiopulmonary Exercise Testing for Decision Making in Patients with Repaired Tetralogy of Fallot

Tetralogy of Fallot is the most common form of cyanotic congenital heart disease. As a result of the surgical strategies employed at the time of initial repair, chronic pulmonary regurgitation (PR) is prevalent in this population. Despite sustained research efforts, patient selection and timing of pulmonary valve replacement (PVR) to address PR in young asymptomatic patients with repaired tetralogy of Fallot (rToF) remain a fundamental but as yet unanswered question in the field of congenital heart disease. The ability of the heart to compensate for the chronic volume overload imposed by PR is critical in the evaluation of the risks and benefits of PVR. The difficulty in clarifying the functional impact of PR on the cardiovascular capacity may be in part responsible for the uncertainty surrounding the timing of PVR. Cardiopulmonary exercise testing (CPET) may be used to assess abnormal cardiovascular response to increased physiologic demands. However, its use as a tool for risk stratification in asymptomatic adolescents and young adults with rToF is still ill-defined. In this paper, we review the role of CPET as a potentially valuable adjunct to current risk stratification strategies with a focus on asymptomatic rToF adolescents and young adults being considered for PVR. The role of maximal and submaximal exercise measurements to identify young patients with a decreased or borderline low peak VO₂ resulting from impaired ventricular function is explored. Current knowledge gaps and research perspectives are highlighted.

Update on the challenges facing the adult with congenital heart disease community: for both the patient and provider

PURPOSE OF REVIEW

The success in the management of congenital heart disease has resulted in a growing population now expected to reach adulthood. The declining mortality during childhood results in adults with decades of cardiovascular disease burden. The purpose of this review is to provide an update on some of the common issues encountered when caring for the adult with congenital heart disease through a review of recently published articles.

RECENT FINDINGS

This review focuses on addressing the lack of information, gaps in clinical care, single ventricle complications, and heart failure in the adults with congenital heart disease population.

SUMMARY

The advancing age of the congenital heart population comes with a substantial life cardiovascular risk. Despite this, they typically experience and report a good quality of life. Providing care to adults with congenital heart disease requires a comprehensive team to address the many complications that are known to arise. This comprehensive team should be available to all.