Exercise-Induced Pulmonary Hypertension in Long-Term Survivors of Congenital Diaphragmatic Hernia.

OBJECTIVE: To determine the prevalence of exercise-induced pulmonary hypertension (PH) among long-survivors of congenital diaphragmatic hernia repair. STUDY DESIGN: This is a single-center, retrospective cohort study of CDH survivors who underwent exercise stress echocardiography (ESE) at Boston Children's Hospital from January 2006 to June 2020. PH severity was assessed by echocardiogram at baseline and after exercise. Patients were categorized by right ventricular systolic pressure (RVSP) after exercise: Group 1 - no or mild PH; and Group 2 - moderate or severe PH (RVSP ≥ 60 mmHg or ≥ ½ systemic blood pressure). RESULTS: Eighty-four patients with CDH underwent 173 ESE with median age 8.1 (4.8 - 19.1) years at first ESE. Sixty-four patients were classified as Group 1, 11 as Group 2, and 9 had indeterminate RVSP with ESE. Moderate to severe PH after exercise was found in 8 (10%) patients with no or mild PH at rest. Exercise-induced PH was associated with larger CDH defect size, patch repair, use of ECMO, supplemental oxygen at discharge, and higher WHO functional class. Higher VE/VCO2 slope, lower peak oxygen saturation, and lower percent predicted FEV1, and FEV1/FVC ratio were associated with Group 2 classification. ESE changed management in 9/11 Group 2 patients. PH was confirmed in all 5 Group 2 patients undergoing cardiac catheterization after ESE. CONCLUSIONS: Among long-term CDH survivors, 10% had moderate-severe exercise-induced PH on ESE, indicating ongoing pulmonary vascular abnormalities. Further studies are needed to optimally define PH screening and treatment for patients with repaired CDH.

Participation in Competitive Sports by Patients With Congenital Heart Disease: AHA/ACC and EAPC/ESC/AEPC Guidelines Comparison.

Sports participation in patients with congenital heart disease is an evolving subject. The American Heart Association/American College of Cardiology released a set of guidelines that advise the type and level of sports participation based primarily on anatomical defects with secondary consideration given to hemodynamic effects. Recently, the European Association of Preventive Cardiology/European Society of Cardiology/Association for European Paediatric and Congenital Cardiology offered a contrasting approach to sports participation that is based on hemodynamic and electrophysiological profiles of each patient, regardless of anatomical consideration. These guidelines are drastically different in their approaches but do have some similarities. In this review, we compare both documents, focusing on the aim, population, classification of sports, and the methodology of making recommendations. This review aims to assist practicing cardiologists in integrating the available published data and recommendations when counseling patients for sports participation.

Exercise as Medicine: Evaluation and Prescription for Adults with Congenital Heart Disease.

PURPOSE OF REVIEW: Understanding exercise physiology as it relates to adult congenital heart disease (ACHD) can be complex. Here we review fundamental physiologic principles and provide a framework for application to the unique ACHD patient population. RECENT FINDINGS: ACHD exercise participation has changed dramatically in the last 50 years. A modern approach focuses on exercise principles and individual anatomic and physiologic considerations. With an evolving better understanding of ACHD exercise physiology, we can strategize plans for patients to participate in dynamic and static exercises. Newly developed technologies including wearable devices provide additive information for ACHD providers for further assessment and monitoring. Preparation and assessment for ACHD patients prior to exercise require a thoughtful, personalized approach. Exercise prescriptions can be formulated to adequately meet the needs of our patients.

Assessment of Exercise Function in Children and Young Adults with Hypertrophic Cardiomyopathy and Correlation with Transthoracic Echocardiographic Parameters.

Exercise function is well characterized in adults with hypertrophic cardiomyopathy (HCM); however, there is a paucity of data in children and young adults with HCM. Here we sought to characterize exercise function in young people with HCM, understand limitations in exercise function by correlating exercise function parameters with echocardiogram parameters and identify prognostic value of exercise parameters. We performed a retrospective, single-center cohort study characterizing exercise function in patients < 26 years old with HCM undergoing cardiopulmonary exercise testing (CPET). Patients with syndromic HCM or submaximal effort were excluded. We compared exercise function in this cohort to population normal values and measured changes in exercise function over time. We correlated exercise function parameters with echocardiographic parameters and investigated the relationship between exercise test parameters and a clinical composite outcome comprised of significant ventricular arrhythmia, death, or heart transplantation. We identified 229 CPETs performed by 117 patients (mean age at time of first CPET 15.6 ± 3.2 years). Mean %-predicted peak VO2, O2 pulse, and peak heart rate were statistically significantly depressed compared to population normal values and exercise function gradually worsened over time. Abnormal exercise testing correlated closely with echocardiographic indices of diastolic dysfunction. There was a trend toward increased incidence of poor clinical outcome in patients with abnormal exercise function. While adverse clinical outcomes were rare, normal exercise function appears to be a marker of low risk for adverse clinical outcomes in this population.

Activity During the COVID-19 Pandemic in Children with Cardiac Rhythm Management Devices.

Decreased physical activity is associated with cardiovascular, metabolic and mental health disease. While decreases in physical activity during the COVID-19 pandemic have been described in the general population, there is a paucity of data regarding children with underlying cardiovascular disease. We hypothesized there would be a decrease in physical activity at the onset of the COVID-19 pandemic. Performed a single-center, retrospective cohort study of children aged < 19 years with cardiac rhythm management devices. Patients were included if they had device-measured physical activity data from > 80% of dates from February 3, 2020 through June 30, 2020. Patients with significant neurologic/neuromuscular disease were excluded. We identified 144 patients with a median age of 15.4 years. 47% were female. 34% had congenital heart disease, 20% had cardiomyopathy, 19% had an inherited arrhythmia syndrome and 5% had atrioventricular block without congenital heart disease. 47% of patients had an implantable loop recorder, 29% had a permanent pacemaker and 24% had an implantable cardioverter-defibrillator. We observed a significant decrease in device-measured physical activity from baseline (February 3-March 9), with up to a 21% decrease in physical activity during mid-March through early May. Activity levels returned to pre-pandemic levels in June. Physical activity sharply declined in children with cardiac rhythm management devices at the onset of the COVID-19 pandemic. These data highlight the importance of finding strategies to maintain physical activity during the current pandemic and future public health crises.

Reducing radiation dose from myocardial perfusion imaging in subjects with complex congenital heart disease.

INTRODUCTION: The prevalence of defects and effective radiation dose from various myocardial perfusion imaging (MPI) strategies in congenital heart disease (CHD) is unknown. METHODS: We studied 75 subjects with complex CHD (ages 5 to 80 years) referred for MPI between 2002 and 2015. A rest and exercise or pharmacologic stress MPI was performed using 99mTechnetium sestamibi, 82rubidium or 13N-ammonia, and Sodium iodide SPECT (single-photon emission computed tomography), SPECT/CT or Cadmium zinc telluride (CZT) SPECT or PET (positron emission tomography)/CT scanners. Deidentified images were interpreted semi-quantitatively in three batches: stress only MPI, stress/rest MPI, and stress/rest MPI with taking into account a history of ventricular septal defect repair. Effective radiation dose was estimated for stress/rest MPI and predicted for 1-day stress-first (normal stress scans), and for 2-day stress/rest MPI (abnormal stress scans). RESULTS: The median age was 18.6 years. The most common type of CHD was transposition of the great arteries (63%). Rest/stress MPI was abnormal in 43% of subjects and 25% of the abnormal scans demonstrated reversible defects. Of the subjects with abnormal MPI, 33% had significant underlying anatomic coronary artery obstruction. Estimated mean effective radiation dose ranged from 2.1 ± 0.6 mSv for 13N-ammonia PET/CT to 12.5 ± 0.9 mSv for SPECT/CT. Predicted effective radiation dose was significantly lower for stress-first MPI and for 2-day stress/rest protocols. CONCLUSIONS: Due to the relatively high prevalence of abnormal stress MPI, tailored protocols with a stress-first MPI as well as the use of 2-day protocols and advanced imaging technologies including CZT SPECT, novel image reconstruction software, and PET MPI could substantially reduce radiation dose in complex CHD.

Exercise testing and spirometry as predictors of mortality in congenital heart disease: Contrasting Fontan physiology with repaired tetralogy of Fallot.

OBJECTIVE: Risk prediction using cardiopulmonary exercise testing (CPET) in complex congenital heart disease tends to either focus on single diagnoses or complete cohorts. We aimed to evaluate patients with two distinct anatomies cared for at a single institution over the same time period to determine CPET variables associated with mortality. DESIGN: All Fontan and tetralogy of Fallot (TOF) subjects with CPET between November 1, 2002 and December 31, 2014 and subsequently died were identified (cases). Cases were matched 1:3 to controls with similar age, underlying anatomy and timing of exercise test. RESULTS: Of the 42 cases, 27 had a Fontan circulation and 15 with TOF. All Fontan patients had a low peak VO2 but there was no significant difference between cases and controls (52.5 ± 14.7 v. 57.4% ± 13.5% predicted, P = .11). Spirometry values were significantly lower in Fontan cases than controls (eg, FVC 67.4 ± 19.1 v 77.6% ± 14.9% predicted, P = .007). Spirometry values were also lower in TOF cases than controls (% predicted FVC 62.8 ± 16.7 v 75 ± 14, P = .006). In contrast to the Fontan analysis, both %peak predicted VO2 and VE/VCO2 slope were worse in TOF cases than controls (50.1 ± 13.5 v. 68.5% ± 15.0% predicted VO2 , P = .0004; 33.9 ± 12.9 v 26.6 ± 4.4, P = .002). Multivariable analysis also identified different predictors of mortality among the anatomic subgroups. Spirometric data (FVC) correlated most strongly with mortality in Fontan patients while the VE/VCO2 slope was most associated with outcome in TOF patients. CONCLUSIONS: Variables most predictive of mortality in Fontan and TOF patients diverge but spirometry was abnormal and associated with mortality in both groups. When compared with age-matched controls, reduced FEV1 and FVC correlated most strongly with mortality in Fontan patients while VE/VCO2 slope correlated with mortality for TOF patients. These findings further support the importance of lung health in patients with complex congenital heart disease.

Contrast volume to estimated glomerular filtration rate ratio for prediction of contrast-induced acute kidney injury after cardiac catheterization in adults with congenital heart disease.

BACKGROUND: Adults with congenital heart disease (ACHD) are vulnerable to contrast-induced acute kidney injury (CI-AKI) after cardiac catheterization. The aim of this study was to identify risk factors for clinically significant CI-AKI and evaluate the predictive value of contrast volume to estimated glomerular filtration rate ratio (V/eGFR) for the risk of CI-AKI following catheterization in the ACHD population. METHODS: ACHD patients who underwent catheterization at Boston Children's hospital between 1/2011 and 1/2017 were retrospectively analyzed. CI-AKI was defined as an increase in serum creatinine ≥0.3 mg/dL within 48 hr or ≥1.5 times baseline within 7 days of procedure. Controls without CI-AKI were matched for calendar year of catheterization with cases using a 3:1 ratio. RESULTS: Of 453 catheterizations meeting inclusion criteria, 27 catheterizations (5.9%) were complicated by CI-AKI, with dialysis being used to manage renal dysfunction in five of these events. Older age, male gender, admission prior to catheterization, and V/eGFR ratio were found to be related to risk of CI-AKI. Patients with a V/eGFR ≥ 2.6 had a significantly higher risk of CI-AKI (OR = 6.4; 95% CI = 2.0-20.4; P = 0.002). Survival at 3 years post-catheterization, was significantly shorter for CI-AKI cases compared to controls (49% versus 97%; P < 0.001) even in those with return to baseline renal function prior to discharge (60% versus 97%, P < 0.001). CONCLUSION: In ACHD patients undergoing cardiac catheterization, a higher V/eGFR ratio is a strong predictor of clinically significant CI-AKI. Development of CI-AKI is a poor prognostic indicator and is associated with decreased survival in this population.

A Pilot Study of Inspiratory Muscle Training to Improve Exercise Capacity in Patients with Fontan Physiology.

While the Fontan procedure has improved life expectancy, patients with single ventricle physiology have impaired exercise capacity due to limited increase in pulmonary blood flow during activity. Enhancing the "thoracic pump" using inspiratory muscle training (IMT) may ameliorate this impairment. Adult nonsmokers with Fontan physiology were recruited through Boston Children's Hospital's outpatient clinic. Participants underwent cardiopulmonary exercise testing and pulmonary function testing, followed by 12 weeks of IMT and then repeat testing. The primary endpoint was change in % predicted peak oxygen consumption (VO2). Secondary endpoints were changes in other exercise metrics. Eleven patients (6 male) were enrolled. Median ages at time of enrollment and Fontan completion were 28.8 years (25.7, 45.5) and 7.8 years (3.9, 16.5), respectively. Average baseline maximal inspiratory pressure (MIP) was normal; only 2 patients had MIP <70% predicted. Peak work rate improved significantly from baseline after 12 weeks of IMT (116.5 ± 45.0 to 126.8 ± 47.0 W, P = 0.019). Peak VO2 tended to improve (baseline 68.1 ± 14.3, change + 5.3 ± 9.6% predicted, P = 0.12), as did VE/VCO2 slope (34.1 ± 6.7 to 31.4 ± 3.6, P = 0.12). There was no change in peak tidal volume or MIP. In a small cohort of Fontan patients with mostly normal MIP, IMT was associated with significant improvement in peak work rate and a trend toward higher peak VO2 and improved ventilatory efficiency. Larger studies are needed to determine if this reflects true lack of effect or whether this pilot study was underpowered for effect size, and whether IMT is more narrowly useful for patients with impaired MIP.

Association of Albuminuria With Major Adverse Outcomes in Adults With Congenital Heart Disease: Results From the Boston Adult Congenital Heart Biobank.

Importance: Albuminuria is associated with adverse outcomes in diverse groups of patients, but the importance of albuminuria in the emerging population of increasingly complex adults with congenital heart disease (ACHD) remains unknown. Objective: To assess the prevalence, risk factors, and prognostic implications of albuminuria in ACHD. Design, Setting, and Participants: This prospective study assessed a cohort of ambulatory patients aged 18 years and older who were examined at an ACHD referral center and enrolled in the Boston ACHD Biobank between May 17, 2012, to August 5, 2016. Albuminuria was defined as an urine albumin-to-creatinine (ACR) ratio of 30 mg/g or more. Main Outcomes and Measures: Death or nonelective cardiovascular hospitalization, defined as overnight admission for heart failure, arrhythmia, thromboembolic events, cerebral hemorrhage, and/or disease-specific events. Results: We measured the ACR of 612 adult patients with CHD (mean [SD] age, 38.6 [13.4] years; 308 [50.3%] women). Albuminuria was present in 106 people (17.3%) and was associated with older age (patients with ACR <30 mg/g: mean [SD]: 37.5 [13.2] years; vs patients with ACR ≥30 mg/g: 43.8 [13.1] years; P < .001), presence of diabetes mellitus (ACR <30 mg/g: 13 of 506 [2.6%]; vs ≥30 mg/g: 11 of 106 [10.4%]; P < .001), lower estimated glomerular filtration rate (ACR <30 mg/g: median [interquartile range (IQR)]: 103.3 [90.0-116.4] mL/min/1.73 m2; ACR ≥30 mg/g: 99.1 [78.8-108.7] mL/min/1.73 m2; P = .002), and cyanosis (ACR <30 mg/g: 23 of 506 [5.1%]; vs ACR ≥30 mg/g: 21 of 106 [22.6%]; P < .001). After a mean (SD) follow-up time of 270 (288) days, 17 patients (2.5%) died, while 68 (11.1%) either died or experienced overnight inpatient admission. Albuminuria predicted outcome, with 30 of 106 patients with albuminuria (28.3%) affected vs 38 of 506 patients without albuminuria (7.5%; hazard ratio [HR], 3.0; 95% CI, 1.9-4.9; P < .001). Albuminuria was also associated with increased mortality (11 of 106 [10.4%]; vs 6 of 506 [1.2%] in patients with and without albuminuria, respectively; HR, 6.4; 95% CI, 2.4-17.3; P < .001). Albuminuria was associated with the outcomes only in patients with a biventricular circulation (HR, 4.5; 95% CI, 2.5-8.0) and not those with single-ventricle circulation (HR, 1.0; 95% CI, 0.4-2.8; P = 0.01 compared with biventricular circulation group). Among 133 patients (21.7%) in NYHA functional class 2, albuminuria was strongly associated with death or nonelective hospitalization. Conclusions and Relevance: Albuminuria is common and is associated with increased risk for adverse outcome in patients with ACHD with biventricular circulation. Albuminuria appears especially useful in stratifying risk in patients categorized as NYHA functional class 2.

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.

Decline in peak oxygen consumption over time predicts death or transplantation in adults with a Fontan circulation.

Peak oxygen consumption (pVO2) measured by cardiopulmonary exercise test (CPET) predicts mortality in adults with a Fontan circulation. The purpose of this study was to assess the additive prognostic value of change in pVO2 over time. METHODS: We analyzed a cohort of adults (≥18 years old) with a Fontan circulation who underwent at least 2 maximal CPETs separated by 6-30 months at Boston Children's Hospital between 2000 and 2015. Survival analysis was performed to determine whether changes in CPET variables, including pVO2 between consecutive tests, were associated with subsequent clinical events. The primary outcome was transplant-free survival. RESULTS: The study included 130 patients with 287 CPET test pairs. Average age was 26.6±9.5 years. Baseline pVO2 averaged 22.0±5.7 mL/kg/min or 60.9%±13.7% predicted. In the cohort overall, there was no change in mean pVO2 between sequential CPETs. Eleven patients died and 2 underwent transplant. On average, pVO2 declined for patients who subsequently died or underwent transplant but remained stable among those who did not (-9.8%±14.6% vs 0.0±13.0%, P<.01). Those with a decline in pVO2 between CPETs were at greater risk of death or transplantation (per 10% decrease in pVO2: HR=2.0, 95% CI 1.2-3.1, P=.004). Change in pVO2 remained a significant predictor of death or transplant after adjusting for pVO2 at first CPET (per 10% decline in pVO2: HR=2.5, 95% CI 1.5-4.2, P<.001). CONCLUSIONS: A decline in pVO2 between consecutive CPETs predicts increased risk for death or transplant in adults with a Fontan circulation independent of baseline pVO2. These results support the additive clinical value of serial CPET in this population.

Feasibility of exercise stress echocardiography and myocardial response in patients with repaired congenital heart disease.

BACKGROUND: Exercise stress echocardiography (ESE) can unmask ventricular dysfunction in asymptomatic patients with congenital heart disease (CHD), but its acquisition and interpretation is often challenging, and the method has not been validated in CHD. This study aimed to evaluate the feasibility of ESE using Doppler imaging and to assess myocardial response to exercise in patients with biventricular (BiV) and univentricular (UniV) circulation after CHD repair. METHODS: In this single-center prospective study, we recruited 55 participants (17 females), median age 14 years (8-22 years). Our analysis categorized participants in these three groups: with structurally normal hearts as controls (n=21), with BiV circulation (n=20) and with UniV circulation (n=14). We acquired ESE images of the systemic ventricle including pulsed-wave flow and spectral tissue Doppler imaging (TDI) of lateral free wall before and immediately after standard, symptom-limited exercise tests on an electronically braked cycle ergometer. RESULTS: During ESE we obtained inflow E-wave and TDI systolic (S') and early diastolic (E') velocities in 93% to 100% of participants at rest and in 90% to 100% of participants post exercise. Feasibility to obtain Doppler imaging parameter was the same across study groups. The myocardial response to exercise was increase in heart rate (HR), S' and inflow E-wave velocity in all participants. Patients with BiV circulation had preserved ventricular function at rest. While patients with UniV circulation had low S', E', and E-wave velocities at rest in comparison to controls and to BiV group (all P<.001), both patients with BiV and UniV circulation showed significant increases in HR, S' velocity and inflow E-wave velocity post exercise, with magnitudes of these increases higher in controls than in the BiV and UniV group. The S' and E' velocities were strongly associated with lower percent predicted peak oxygen consumption VO2 (rs=0.614 and rs=0.64, respectively, both P<.001). CONCLUSION: ESE with Doppler imaging is a practical noninvasive diagnostic method and sufficiently robust for the assessment of morphologic LV/systemic ventricles under exercise in patients after biventricular and univentricular CHD repair. Although patients with BiV and UniV circulation had both preserved myocardial response to exercise, the magnitude of this response was the lowest in patients with UniV circulation.

The effect of 1 year of Alagebrium and moderate-intensity exercise training on left ventricular function during exercise in seniors: a randomized controlled trial.

Sedentary aging leads to left ventricular (LV) and vascular stiffening due in part to advanced glycation end-products (AGEs) cross-linking of extracellular matrix proteins. Vigorous lifelong exercise ameliorates age-related cardiovascular (CV) stiffening and enhances exercise LV function, although this effect is limited when exercise is initiated later in life. We hypothesized that exercise training might be more effective at improving the impact of age-related CV stiffening during exercise when combined with an AGE cross-link breaker (Alagebrium). Sixty-two seniors (≥60 yr) were randomized into four groups: sedentary + placebo, sedentary + Alagebrium, exercise + placebo, and exercise + Alagebrium for 1 yr. Moderate-intensity aerobic exercise was performed 3-4 sessions/wk; controls underwent similar frequency of yoga/balance training. Twenty-four similarly-aged, lifelong exercisers (4-5 sessions/wk) served as a comparator for the effect of lifelong exercise on exercising LV function. Oxygen uptake (Douglas bags), stroke index (SI; acetylene rebreathing), and effective arterial elastance (Ea) were collected at rest and submaximal and maximal exercise. Maximum O2 uptake (23 ± 5 to 25 ± 6 ml·kg(-1)·min(-1)) increased, while SI (35 ± 11 to 39 ± 12 ml/m(2)) and Ea (4.0 ± 1.1 to 3.7 ± 1.2 mmHg·ml(-1)·m(-2)) were improved across all conditions with exercise, but remained unchanged in controls (exercise × time, P ≤ 0.018). SI or Ea were not affected by Alagebrium (medication × time, P ≥ 0.468) or its combination with exercise (interaction P ≥ 0.252). After 1 yr of exercise plus Alagebrium, exercise SI and Ea remained substantially below that of lifelong exercisers (15-24 and 9-22%, respectively, P ≤ 0.415). In conclusion, Alagebrium plus exercise had no synergistic effect on exercise LV function and failed to achieve levels associated with lifelong exercise, despite a similar exercise frequency.

Evaluation of Health Care Quality in Adults with Congenital Heart Disease.

Providing medical care for adults with congenital heart disease (CHD) is a complex endeavor requiring an understanding of all aspects of the health system. Adult patients with CHD often have multiple medical issues related to the underlying CHD, the sequelae of surgical or catheter interventions, and the addition of typical conditions of adulthood superimposed on the CHD. In this article, the authors first frame the assessment of quality in the health care system as a whole and then focus on CHD and the unique approach required in the care of the adult with CHD.