Exercise capacity reflects ventricular function in patients having the Fontan circulation

Correlation between three-dimensional echocardiography and cardiopulmonary fitness in patients with univentricular heart: A cross-sectional multicentre prospective study

BACKGROUND

The prognosis of patients with a functional single ventricle has improved, with better cardiopulmonary fitness, health-related quality of life and survival. Conventional echocardiography remains the first-line technique in single ventricle follow-up. Three-dimensional (3D) echocardiography has shown recent value in congenital cardiology, but its ability to predict functional status in patients with a single ventricle remains unknown.

AIM

To evaluate, in patients with a single ventricle, the association between 3D echocardiography variables and functional status determined by cardiopulmonary fitness.

METHODS

Children and adults with a functional single ventricle were prospectively enrolled in this multicentre study. Cardiopulmonary fitness was assessed by cardiopulmonary exercise test, with measures of maximum oxygen uptake (VO_2max) and ventilatory efficiency (VE/VCO₂ slope). 3D echocardiography was performed with off-line reproducibility analyses, using TomTec Arena™ software. Health-related quality of life was assessed using the SF-36 questionnaire.

RESULTS

A total of 33 patients were screened, and 3D echocardiography analyses were feasible in 22 subjects (mean age 28±9years). 3D echocardiography ejection fraction correlated with percent-predicted VO_2max (r=0.64, P<0.01), VE/VCO₂ slope (r=-0.41, P=0.05), two-dimensional echocardiography ejection fraction (r=0.55, P<0.01) and health-related quality of life physical functioning dimension (r=0.56, P=0.04). 3D echocardiography indexed end-systolic volume correlated with percent-predicted VO_2max (r=-0.45, P=0.03) and VE/VCO₂ slope (r=0.65, P<0.01). 3D echocardiography reproducibility was good.

CONCLUSIONS

Single ventricle ejection fraction and volumes measured by 3D echocardiography correlated with cardiopulmonary fitness, as determined by two main prognostic cardiopulmonary exercise test variables: VO_2max and VE/VCO₂ slope. Despite good reproducibility, 3D echocardiography feasibility remained limited. 3D echocardiography may be of value in single ventricle follow-up, provided that the technique and analysis software are improved.

Coronary Microvascular Dysfunction in Patients with Congenital Heart Disease

Congenital heart diseases represent a wide range of cardiac malformations. Medical and surgical advances have dramatically increased the survival of patients with congenital heart disease, leading to a continuously growing number of children, adolescents, and adults with congenital heart disease. Nevertheless, congenital heart disease patients have a worse prognosis compared to healthy individuals of similar age. There is substantial overlap in the pathophysiology of congenital heart disease and heart failure induced by other etiologies. Among the pathophysiological changes in heart failure, coronary microvascular dysfunction has recently emerged as a crucial modulator of disease initiation and progression. Similarly, coronary microvascular dysfunction could be important in the pathophysiology of congenital heart diseases as well. For this systematic review, studies on maximal vasodilatory capacity in the coronary microvascular bed in patients with congenital heart disease were searched using the PubMed database. To date, coronary microvascular dysfunction in congenital heart disease patients is incompletely understood because studies on this topic are rare and heterogeneous. The prevalence, extent, and pathophysiological relevance of coronary microvascular dysfunction in congenital heart diseases remain to be elucidated. Herein, we discuss what is currently known about coronary microvascular dysfunction in congenital heart disease and future directions.

Circulatory Response to Rapid Volume Expansion and Cardiorespiratory Fitness in Fontan Circulation

The role of dysfunction of the single ventricle in Fontan failure is incompletely understood. We aimed to evaluate hemodynamic responses to preload increase in Fontan circulation, to determine whether circulatory limitations in different locations identified by experimental preload increase are associated with cardiorespiratory fitness (CRF), and to assess the impact of left versus right ventricular morphology. In 38 consecutive patients (median age = 16.6 years, 16 females), heart catheterization was supplemented with a rapid 5-mL/kg body weight volume expansion. Central venous pressure (CVP), ventricular end-diastolic pressure (VEDP), and peak systolic pressure were averaged for 15‒30 s, 45‒120 s, and 4‒6 min (steady state), respectively. CRF was assessed by peak oxygen consumption (VO_2peak) and ventilatory threshold (VT). Median CVP increased from 13 mmHg at baseline to 14.5 mmHg (p < 0.001) at steady state. CVP increased by more than 20% in eight patients. Median VEDP increased from 10 mmHg at baseline to 11.5 mmHg (p < 0.001). Ten patients had elevated VEDP at steady state, and in 21, VEDP increased more than 20%. The transpulmonary pressure difference (CVP‒VEDP) and CVP were consistently higher in patients with right ventricular morphology across repeated measurements. CVP at any stage was associated with VO_2peak and VT. VEDP after volume expansion was associated with VT. Preload challenge demonstrates the limitations beyond baseline measurements. Elevation of both CVP and VEDP are associated with impaired CRF. Transpulmonary flow limitation was more pronounced in right ventricular morphology. Ventricular dysfunction may contribute to functional impairment after Fontan operation in young adulthood.ClinicalTrials.gov identifier NCT02378857.

Prognostic Value of Maximal and Submaximal Exercise Performance in Fontan Patients < 15 Years of Age

In patients after Fontan completion exercise capacity is significantly reduced. Although peak oxygen consumption (VO_2peak) is a strong prognostic factor in many cardiovascular diseases, it requires the achievement of a maximal effort. Therefore, submaximal exercise parameters such as oxygen uptake efficiency slope (OUES) may be of value. In the present observational study we evaluated the exercise capacity with maximal and submaximal parameters in a group of Fontan patients with an extracardiac conduit and determined their prognostic value. Sixty Fontan patients followed up in the Leiden University Medical Center who have performed an exercise test were included in this retrospective study. Exercise tests were performed at a median age of 11 years. Fontan patients showed on average lower values for all exercise parameters compared to reference values from a healthy dataset as shown by the %predicted values: VO_2peak%:mean 66%(95%CI:64 to 74) and OUES%:mean 72%(95%CI:67 to 77). Twenty percent of the patients were not able to achieve an RER>1.0. RER showed a moderate positive correlation with VO_2peak but not with OUES. There was a deterioration of VO_2peak% and OUES% over time. OUES was significantly lower in patients with cardiac events in the follow up period. Fontan patients have an impaired exercise performance even at young ages and it deteriorates with age. An important percentage of Fontan patients is not able to reach maximal effort so the use of submaximal parameters, like OUES, should be considered as part of the evaluation. Moreover, OUES could have a prognostic value in this group of patients.

Exercise Intolerance, Benefits, and Prescription for People Living With a Fontan Circulation: The Fontan Fitness Intervention Trial (F-FIT)-Rationale and Design

Background: Despite developments in surgical techniques and medical care, people with a Fontan circulation still experience long-term complications; non-invasive therapies to optimize the circulation have not been established. Exercise intolerance affects the majority of the population and is associated with worse prognosis. Historically, people living with a Fontan circulation were advised to avoid physical activity, but a small number of heterogenous, predominantly uncontrolled studies have shown that exercise training is safe-and for unique reasons, may even be of heightened importance in the setting of Fontan physiology. The mechanisms underlying improvements in aerobic exercise capacity and the effects of exercise training on circulatory and end-organ function remain incompletely understood. Furthermore, the optimal methods of exercise prescription are poorly characterized. This highlights the need for large, well-designed, multi-center, randomized, controlled trials. Aims and Methods: The Fontan Fitness Intervention Trial (F-FIT)-a phase III clinical trial-aims to optimize exercise prescription and delivery in people with a Fontan circulation. In this multi-center, randomized, controlled study, eligible Fontan participants will be randomized to either a 4-month supervised aerobic and resistance exercise training program of moderate-to-vigorous intensity followed by an 8-month maintenance phase; or usual care (control group). Adolescent and adult (≥16 years) Fontan participants will be randomized to either traditional face-to-face exercise training, telehealth exercise training, or usual care in a three-arm trial with an allocation of 2:2:1 (traditional:telehealth:control). Children (<16 years) will be randomized to either a physical activity and exercise program of moderate-to-vigorous intensity or usual care in a two-arm trial with a 1:1 allocation. The primary outcome is a change in aerobic exercise capacity (peak oxygen uptake) at 4-months. Secondary outcomes include safety, and changes in cardiopulmonary exercise testing measures, peripheral venous pressure, respiratory muscle and lung function, body composition, liver stiffness, neuropsychological and neurocognitive function, physical activity levels, dietary and nutritional status, vascular function, neurohormonal activation, metabolites, cardiac function, quality of life, musculoskeletal fitness, and health care utilization. Outcome measures will be assessed at baseline, 4-months, and 12-months. This manuscript will describe the pathophysiology of exercise intolerance in the Fontan circulation and the rationale and protocol for the F-FIT.

The Influence of Atrial Strain on Functional Capacity in Patients with the Fontan Circulation

Speckle-tracking echocardiography has been used to assess atrial function. This analysis is feasible in univentricular hearts. The aim of this study was to characterize the relationship between atrial strain and functional capacity in the Fontan circulation. Apical four-chamber echocardiographic loops of 39 Fontan patients were reviewed. The dominant atrium was assessed for active (ε_act), conduit (ε_con), and reservoir (ε_res) strain and ε_act/ε_res ratio. Cardiopulmonary exercise test was performed on the same day and oxygen uptake (VO₂) at ventilatory threshold (VT) and peak VO₂ were chosen as the dependent variables. Statistical analysis was performed using SPSS^® version 23. Unpaired t test was used for binomial and continuous variable correlation; single and multivariable linear regression were used for continuous variable correlation. Statistical significance was defined as p value < 0.05. VO₂ at VT as a percentage of predicted VO₂ was 36.8% (SD 10.7). Peak VO₂ was 64.7% (SD 18.9) of the predicted value. In univariate analysis, both were associated with age, atrioventricular regurgitation, ejection fraction, ε_res, ε_con, and ε_act/ε_res. In multivariate regression, higher VO₂ at VT and peak VO₂ were associated with younger age (p = 0.003 and p = 0.001, respectively) and higher ε_con (p = 0.026 and p = 0.020). Evaluation of heart function is difficult in the Fontan circulation, hindered by complex ventricular morphology and lack of normative data. VO₂ provides a good surrogate. Atrial strain parameters are compromised in these patients and associated with VO₂. Therefore, whenever possible, atrial strain should be measured as it may provide a new method of risk stratification.

Long Term Consequences of the Fontan Procedure and How to Manage Them

In 1971, Fontan and Baudet described a surgical technique for successful palliation of patients with tricuspid atresia. Subsequently, this technique has been applied to treat most forms of functional single ventricles and has become the current standard of care for long-term palliation of all patients with single ventricle congenital heart disease. Since 1971, the Fontan procedure has undergone several variations. These patients require lifelong management including a thorough knowledge of their anatomic substrate, hemodynamic status, management of rhythm and ventricular function along with multi organ evaluation. As these patients enter middle age, there is increasing awareness regarding the long-term complications and mortality. This review highlights the long-term outcomes of the Fontan procedure and management of late sequelae.

Prognostic power of cardiopulmonary exercise testing in Fontan patients: a systematic review

Objective

Exercise impairment is common in Fontan patients. Our aim is to systematically review previous literature to determine the prognostic value of exercise capacity in older adolescent and adult Fontan patients with respect to late outcome. Additionally, we reviewed the determinants of exercise capacity in Fontan patients and changes in exercise capacity over time.

Methods

PubMed, CINAHL, Embase, The Cochrane Library and Scopus were searched systematically for studies reporting exercise capacity and late outcome such as mortality, cardiac transplantation and hospitalisation. Studies were eligible for inclusion if more than 30 patients were included and mean age was ≥16 years.

Results

Four thousand and seven hundred and twenty-two studies were identified by the systematic search. Seven studies fulfilled the inclusion and exclusion criteria. The total number of patients was 1664 adult Fontan patients. There were 149 deaths and 35 heart transplantations. All eligible studies were retrospective cohort studies. The correlation between exercise capacity and late outcome was identified, and HRs were reported.

Conclusion

In Fontan patients, the best predictors of death and transplantation were a decline in peak VO₂, heart rate variables and exercise oscillatory ventilation. Peak VO₂ was not strongly predictive of mortality or hospitalisation in Fontan patients. Several variables were strong and independent predictors of hospitalisation and morbidity.

Mechanism for temporal changes in exercise capacity after Fontan palliation: Role of Doppler echocardiography

BACKGROUND

The objective was to better understand Doppler hemodynamics and exercise capacity in patients with Fontan palliation by delineating the hemodynamic mechanism for temporal changes in their peak oxygen consumption (V̇o₂).

METHODS

We performed a retrospective review of adult Fontan patients with systemic left ventricle (LV) who underwent serial transthoracic echocardiograms (TTE) and cardiopulmonary exercise tests (CPET) at Mayo Clinic in 2000-2015. TTE and CPET data were used (1) to determine agreement between V̇o₂ and Doppler-derived LV function indices (eg, stroke volume index [SVI] and cardiac index [CI]) and (2) to determine agreement between temporal changes in peak V̇o₂ and LV function indices.

RESULTS

Seventy-five patients (44 men; 59%) underwent 191 pairs of TTE and CPET. At baseline, mean age was 24±3 years, peak V̇o₂ was 22.9±4.1 mL/kg/min (63±11 percent predicted), SVI was 43±15 mL/m², and CI was 2.9±0.9 L/min/m². Peak V̇o₂ correlated with SVI (r=0.30, P<.001) and with CI (r=0.45, P<.001) in the 153 pairs of TTE and CPET in patients without cirrhosis. Temporal changes in percent predicted peak V̇o₂ correlated with changes in SVI (r=0.48, P=.005) and CI (r=0.49, P=.004) among the 33 patients without interventions during the study. In the 19 patients with Fontan conversion, percent predicted peak V̇o₂ and chronotropic index improved.

CONCLUSIONS

Overall, there was a temporal decline in peak V̇o₂ that correlated with decline in Doppler SVI. In the patients who had Fontan conversion operation, there was a temporal improvement in peak V̇o₂ that correlated with improvement in chronotropic index.

Impact of sildenafil on echocardiographic indices of myocardial performance after the Fontan operation

The objective of this study was describe the impact of sildenafil on echocardiographic measures of myocardial performance in children and young adults with a functional single-ventricle physiology late after Fontan surgery. A double-blind, placebo-controlled, crossover trial was conducted in children and young adults after the Fontan operation at a single pediatric center. Subjects were randomized to receive placebo or sildenafil (20 mg tid) for 6 weeks. After a 6-week washout period, subjects were crossed for an additional 6 weeks. Each subject underwent an echocardiogram at the start and finish of each phase. A total of 27 subjects completed study testing at a mean age of 14.9 years and a mean time from Fontan surgery of 11.3 years. After sildenafil, subjects demonstrated improvement in their myocardial performance index (MPI; -0.051; 95% CI -0.095, -0.0077; p 0.02) and in the product of the velocity time integral (VTI) of the dominant outflow tract and the heart rate (HR; 110 cm × bpm; 95% CI 7.5, 220; p = 0.04). Measures of diastolic performance, including inflow velocities, myocardial velocities, and the ratio of blood pool velocity to myocardial velocity during passive inflow, did not change. In this cohort, there were significant improvements in both the MPI and the product of the VTI × HR after 6 weeks of treatment with sildenafil. These findings suggest that sildenafil may be a useful therapy to improve or maintain ventricular performance in select patients after the Fontan operation.

Patients with single-ventricle physiology: prognostic implications of stress testing

This study used a retrospective analysis of adults with single-ventricle physiology to ascertain the predictive power of cardiopulmonary stress-testing parameters in determining patients at increased risk of suffering from adverse clinical outcomes. We found that the specific parameters of percent of maximum predicted heart rate achieved and maximum oxygen consumption were significantly correlated with adverse clinical outcomes in patients with single-ventricle congenital heart disease.