Living at an altitude adversely affects exercise capacity in Fontan patients

2640 Meters Closer to The Stars: Does High Altitude Affect Fontan Results?

BACKGROUND

Risk factors and postoperative results of the Fontan operation in patients living at high altitude (> 2500 meters above sea level) in the Andean region remains unknown. Evaluate results and risk factor for immediate postoperative outcomes and short- and long-term functional class after Fontan.

METHODS

From June 2003 to February 2019, 104 patients receiving Fontan procedure at 2640 meters (8661 feet) above-sea-level were retrospectively studied. Preoperative catheterization, intraoperative variables and post-operative outcomes were described. Functional class was evaluated in patients living permanently below (Group I) and at or higher than 2500 meters (8202 feet) above sea level. (Group II) Risk factors for mortality were analyzed.

RESULTS

Median age at operation was 8.5 ± 4.4 years; Pulmonary artery pressure 16.2 ± 3.6 mmHg; EDVP 13.3 ± 3.8mmHg, PVRI 2.1(IQR 07-3.7) Wood units. Chest tube duration was 8,5 (6-12) days. Mortality was 4.8%, with 0 in the last 5 years. Higher preoperative pulmonary pressure (16.2 ± 3.6 vs 21.2 ± 3.40mmHg, (P Value 0.01), aortic cross clamp time (P value< 0.001) and renal failure (P value <0.01) were associated with mortality. Functional class improve to class I in 86.4%. Overall survival was 90. 7 % at ten years follow up.

CONCLUSIONS

Increased pulmonary pressure and PVRI are directly related to high altitude. Fontan-Kreutzer operation performed at high altitude in the Andean region is feasible with good results. We routinely fenestrate all cases to avoid dysfunction in the early postoperative period. Functional status is adequate after the operation.

Fibrin airway cast obstruction: Experience, classification, and treatment guideline from Denver

BACKGROUND AND OBJECTIVES

Plastic bronchitis (PB) is a condition characterized by the formation of thick airway casts leading to acute and often life-threatening airway obstruction. PB occurs mainly in pediatric patients with congenital heart disease (CHO) who have undergone staged surgical palliation (Glenn, Fontan), but can also occur after chemical inhalation, H1N1, severe COVID-19, sickle cell disease, severe asthma, and other diseases. Mortality risk from PB can be up to 40%-60%, and no treatment guideline exist. The objectives herein are to develop a standardized evaluation, classification, and treatment guideline for PB patients presenting with tracheobronchial casts, based on our experience with PB at the Children's Hospital of Colorado in Denver.

METHODS

We describe 11 patients with CHO-associated PB (post-Fontan [n = 9], pre-Fontan [n = 2]) who presented with their initial episodes. We utilized histopathological analysis of tracheobronchial casts to guide treatment in these patients, utilizing our hospital-wide guideline document and classification system.

RESULTS

We found that 100% of post-Fontan PB patients had fibrinous airway casts, while pre-Fontan PB casts were fibrinous only in one of two patients (50%). Utilizing histopathology as a guide to therapy, PB patients with fibrin airway casts were treated with airway-delivered fibrinolytics and anticoagulants, as well as aggressive airway clearance and other supportive care measures. These therapies resulted in successful cast resolution and improved survival in post-Fontan PB patients.

CONCLUSION

We have shown an improved outcome in PB patients whose treatment plan was based on Denver's PB classification schema and standardized treatment guideline based on tracheobronchial cast histopathology.

Predictors of Poor Functional Status in Adult Fontan Patients Living at Moderate Altitude

Patients who have undergone Fontan palliation have reduced exercise tolerance measured by maximal oxygen consumption (VO₂ max). Declining exercise capacity is associated with increased morbidity and mortality. The impact of hemodynamics and other variables on this population's functional status is not well understood. This study sought to identify variables that predict low VO₂ max in Fontan patients living at moderate altitude (5,000-8,000 feet). We performed a retrospective cohort study of 44 adult Fontan patients living at moderate altitude who had undergone cardiopulmonary exercise testing (CPET) and cardiac catheterization. We evaluated hemodynamic parameters measured during catheterization, imaging results, and laboratory studies for correlation with VO₂ max measured during CPET. Our study cohort (median age 30 years, 52% female) had exercise impairment with mean VO₂ max of 21.6 mL/kg/min. Higher trans-pulmonary gradient (TPG) (p < 0.001) and mean pulmonary artery (PA) pressure (p = 0.013) were predictors of lower maximal and submaximal VO₂. Higher BNP values correlated with lower VO₂ max (p = 0.01). Platelet count, GGT, albumin, and pulmonary vasodilator therapy did not correlate with VO₂ max. None of the studied variables were associated with higher minute ventilation to peak carbon dioxide production (VE/VCO₂ slope) or change in VO₂ max over time. In conclusion, higher TPG and mean PA pressure predicted lower exercise tolerance amongst our cohort of adult Fontan patients living at moderate altitude. Future studies are needed to determine if these clinical variables represent viable therapeutic targets that could result in improved exercise tolerance and outcomes in patients with Fontan circulation.

Exercise-induced hypoxia predicts hypobaric hypoxia during flight in patients after Fontan operation

BACKGROUND

Hypobaric hypoxia (HH) during flight might be more detrimental to pulmonary circulation in Fontan patients compared healthy individuals. This study was designed to clarify whether exercise-induced hypoxia could predict HH during flight in Fontan patients.

METHODS AND RESULTS

Percutaneous oxygen saturation (SpO₂) was analyzed during flight in 11 Fontan patients and eight volunteers. SpO₂ was measured before taking off (S1), at the initial (S2), the end of stabilization (S3), and after landing (S4). The SpO₂-dynamics were compared with SpO₂-dynamics during cardiopulmonary exercise testing (CPX), pulmonary function, and hemodynamics in the Fontan patients. At all measurements, SpO₂ was lower in the Fontan patients than the volunteers during flight. The total SpO₂ decline from S1 to S3 was greater in the Fontan patients than the volunteers. While SpO₂ change from S2 to S3 was negative in the Fontan patients, it was stable in the volunteers. In the Fontan patients, the median value of exercise-induced SpO₂ decline (Ex-dSpO₂), SpO₂ at rest, and SpO₂ at peak was -6%, 93%, and 88%, respectively. In addition to exercise capacity and pulmonary function, the Ex-dSpO₂ was correlated strongly with SpO₂ at all phases during flight (r = 0.75-0.98, p < 0.01 for all). Flight-associated adverse events occurred in two patients with SpO₂ < 80% at S3.

CONCLUSIONS

Both the Fontan patients and the volunteers demonstrated similar SpO₂-dynamics during flight with a greater HH in the Fontan patients. CPX with SpO₂ monitoring is useful in predicting SpO₂-dynamics and adverse events during flight in these patients.

Exercise Performance at Increased Altitude After Fontan Operation: Comparison to Normal Controls and Correlation with Cavopulmonary Hemodynamics

Exercise performance declines as patients who have undergone Fontan operation enter adolescence. However, the effect of altitude on functional capacity after Fontan remains inadequately studied. Our aim was to describe exercise performance in a cohort of patients with Fontan physiology living at increased altitude and compare to a normal control group and relate these data to invasively derived hemodynamics. We hypothesized that peak oxygen consumption ([Formula: see text]) would be decreased, in association with elevated mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance (PVRi). Patients were evaluated in a multidisciplinary clinic for patients with Fontan physiology. Evaluation included cardiopulmonary exercise test and cardiac catheterization at predetermined intervals. Descriptive statistics were calculated. Associations of catheterization and exercise testing measures with [Formula: see text] were estimated with Spearman correlation coefficients. One hundred patients with age- and gender-matched controls were included in the analysis. The mean age was 13.3 ± 3.9 years, with mean weight of 47.1 ± 18.4 kg. The mean [Formula: see text] was 29.0 ± 7.8 ml/kg/min, significantly lower than the control group, 40.2 ± 8.4 ml/kg/min (p < 0.0001). There was no statistically significant linear correlation between [Formula: see text] and mPAP or PVRi. We characterized exercise performance in a large cohort with Fontan physiology living at increased altitude and showed a decrease in [Formula: see text] compared to controls. Our data do not support the hypothesis that moderately increased altitude has a detrimental effect on exercise performance, nor is there a substantial link between poor cavopulmonary hemodynamics and exercise in this setting.

Exercise responses in children and adults with a Fontan circulation at simulated altitude

BACKGROUND

Traveling to high altitude has become more popular. High-altitude exposure causes hypobaric hypoxia. Exposure to acute high altitude, during air travel or mountain stays, seems to be safe for most patients with congenital heart disorders (CHD). Still, current guidelines for CHD patients express concerns regarding safety of altitude exposure for patients with a Fontan circulation. Therefore, investigating hemodynamic and pulmonary responses of acute high-altitude exposure (±2500 m) at rest and during maximal exercise in patients with Fontan circulation can provide clarity in this dispute and may contribute to improvement of clinical counseling.

METHODS

Twenty-one Fontan patients with 21 age-matched healthy controls, aged 8-40 years, were enrolled in an observational study. Participants performed two cardiopulmonary exercise tests on a cycle ergometer with breath-by-breath respiratory gas analyses combined with noninvasive impedance cardiac output measurements: one at sea level (±6 m) and one at simulated high altitude (±2500 m), respectively.

RESULTS

The effect of altitude exposure was different in rest for saturation (-2.3% vs -4.1%) between Fontan patients and healthy controls (P < .05). At peak exercise the effects of high altitude exposure was different on VO₂ (-5.1% vs 9.6%) and AvO₂ -diff (-0.3% vs -12.8%) between Fontan patients and healthy controls.

CONCLUSION

Although, acute high-altitude exposure has a detrimental effect on exercise capacity, the impact on pulmonary and hemodynamic responses of high-altitude exposure is comparable between Fontan patients and healthy controls.

The Fontan circulation after 45 years: update in physiology

The Fontan operation was first performed in 1968. Since then, this operation has been performed on thousands of patients worldwide. Results vary from very good for many decades to very bad with a pleiad of complications and early death. A good understanding of the physiology is necessary to further improve results. The Fontan connection creates a critical bottleneck with obligatory upstream congestion and downstream decreased flow; these two features are the basic cause of the majority of the physiologic impairments of this circulation. The ventricle, while still the engine of the circuit, cannot compensate for the major flow restriction of the Fontan bottleneck: the suction required to compensate for the barrier effect cannot be generated, specifically not in a deprived heart. Except for some extreme situations, the heart therefore no longer controls cardiac output nor can it significantly alter the degree of systemic venous congestion. Adequate growth and development of the pulmonary arteries is extremely important as pulmonary vascular impedance will become the major determinant of Fontan outcome. Key features of the Fontan ventricle are early volume overload and overgrowth, but currently chronic preload deprivation with increasing filling pressures. A functional decline of the Fontan circuit is expected and observed as pulmonary vascular resistance and ventricular filling pressure increase with time. Treatment strategies will only be successful if they open up or bypass the critical bottleneck or act on immediate surroundings (impedance of the Fontan neoportal system, fenestration, enhanced ventricular suction).

Pediatric Pulmonary Hypertension: Guidelines From the American Heart Association and American Thoracic Society

Pulmonary hypertension is associated with diverse cardiac, pulmonary, and systemic diseases in neonates, infants, and older children and contributes to significant morbidity and mortality. However, current approaches to caring for pediatric patients with pulmonary hypertension have been limited by the lack of consensus guidelines from experts in the field. In a joint effort from the American Heart Association and American Thoracic Society, a panel of experienced clinicians and clinician-scientists was assembled to review the current literature and to make recommendations on the diagnosis, evaluation, and treatment of pediatric pulmonary hypertension. This publication presents the results of extensive literature reviews, discussions, and formal scoring of recommendations for the care of children with pulmonary hypertension.

Exercise capacity in the Bidirectional Glenn physiology: Coupling cardiac index, ventricular function and oxygen extraction ratio

In Bi-directional Glenn (BDG) physiology, the superior systemic circulation and pulmonary circulation are in series. Consequently, only blood from the superior vena cava is oxygenated in the lungs. Oxygenated blood then travels to the ventricle where it is mixed with blood returning from the lower body. Therefore, incremental changes in oxygen extraction ratio (OER) could compromise exercise tolerance. In this study, the effect of exercise on the hemodynamic and ventricular performance of BDG physiology was investigated using clinical patient data as inputs for a lumped parameter model coupled with oxygenation equations. Changes in cardiac index, Qp/Qs, systemic pressure, oxygen extraction ratio and ventricular/vascular coupling ratio were calculated for three different exercise levels. The patient cohort (n=29) was sub-grouped by age and pulmonary vascular resistance (PVR) at rest. It was observed that the changes in exercise tolerance are significant in both comparisons, but most significant when sub-grouped by PVR at rest. Results showed that patients over 2 years old with high PVR are above or close to the upper tolerable limit of OER (0.32) at baseline. Patients with high PVR at rest had very poor exercise tolerance while patients with low PVR at rest could tolerate low exercise conditions. In general, ventricular function of SV patients is too poor to increase CI and fulfill exercise requirements. The presented mathematical model provides a framework to estimate the hemodynamic performance of BDG patients at different exercise levels according to patient specific data.

Evaluation of the thickness of the proximal femoral canal in patients living at altitude

OBJECTIVE:

Our goal is to confirm the hypothesis that people who were born and raised on cities at altitude have a smaller proximal femoral canal.

METHODS:

Prospective study with 169 participants, divided into two groups. Group A: 99 patients who were born and raised at altitude and group B: 70 patients who were born and raised at low altitude. All patients underwent panoramic radiographs of the pelvis, where we marked three measure and checked the thickness of the cortical and the lateral and medial cortical, as well as the thickness of the femoral canal.

RESULTS:

We noticed that the first measure showed no significant difference in both groups, but the second measure, the lateral cortex, is thicker in group A, and the femoral canal is smaller in comparison to group B.

CONCLUSION:

We concluded that patients who were born and raised at altitude have a smaller femoral canal. This may help in proper planning of future surgical procedures, especially in total hip arthroplasty cases.

Level of Evidence II, Development of Diagnostic Criteria in Consecutive Patients (with universally applied reference "gold" standard).

Effect of high altitude exposure on the hemodynamics of the bidirectional Glenn physiology: modeling incremented pulmonary vascular resistance and heart rate

The considerable blood mixing in the bidirectional Glenn (BDG) physiology further limits the capacity of the single working ventricle to pump enough oxygenated blood to the circulatory system. This condition is exacerbated under severe conditions such as physical activity or high altitude. In this study, the effect of high altitude exposure on hemodynamics and ventricular function of the BDG physiology is investigated. For this purpose, a mathematical approach based on a lumped parameter model was developed to model the BDG circulation. Catheterization data from 39 BDG patients at stabilized oxygen conditions was used to determine baseline flows and pressures for the model. The effect of high altitude exposure was modeled by increasing the pulmonary vascular resistance (PVR) and heart rate (HR) in increments up to 80% and 40%, respectively. The resulting differences in vascular flows, pressures and ventricular function parameters were analyzed. By simultaneously increasing PVR and HR, significant changes (p <0.05) were observed in cardiac index (11% increase at an 80% PVR and 40% HR increase) and pulmonary flow (26% decrease at an 80% PVR and 40% HR increase). Significant increase in mean systemic pressure (9%) was observed at 80% PVR (40% HR) increase. The results show that the poor ventricular function fails to overcome the increased preload and implied low oxygenation in BDG patients at higher altitudes, especially for those with high baseline PVRs. The presented mathematical model provides a framework to estimate the hemodynamic performance of BDG patients at different PVR increments.

Living at altitude adversely affects survival among patients with a Fontan procedure

OBJECTIVES

This study sought to determine whether survival in this cohort of patients was adversely affected by increased residential altitude.

BACKGROUND

The success of the Fontan procedure depends in large part on low pulmonary vascular resistance (PVR). Factors that increase PVR, including an increase in residential altitude, may adversely affect long-term outcome. Higher altitude has been shown to affect functional well-being in patients with a Fontan circulation.

METHODS

Databases from a tertiary cardiac care center in the Intermountain West (elevation 5,000 feet) were analyzed for patients born with single-ventricle anatomy who would now be of adult age. Complete data were then collected on all identified patients who subsequently underwent the Fontan operation. Correlates of, and time to, adverse outcome, defined as death, cardiac transplantation, or clinical decompensation requiring a move to sea level, were determined.

RESULTS

Of 149 patients with single-ventricle anatomy, 103 underwent the Fontan procedure, with 70 surviving to adulthood at moderate altitude. Adverse outcome occurred in 55, with death in 24 (23%), cardiac transplantation in 18 (17%), and clinical decompensation requiring move to sea level in 13 (13%). There was no relationship between type, age at, or era of Fontan procedure and long-term outcome. Correlates of long-term, transplant-free survival at moderate altitude included lower residential altitude (4,296 vs. 4,637 feet, p < 0.001), and lower pulmonary artery pressures before the Fontan procedure (13 vs. 15 mm Hg, p = 0.01), and after (14 vs. 18 mm Hg, p = 0.01).

CONCLUSIONS

Long-term outcome after the Fontan procedure is adversely impacted by higher residential altitude.

Moderate altitude is not associated with adverse postoperative outcomes for patients undergoing bidirectional cavopulmonary anastomosis and Fontan operation: a comparative study among Denver, Edmonton, and Toronto

OBJECTIVE

Outcomes of patients with single ventricle physiology undergoing cavopulmonary palliations depend on pulmonary vascular resistance (PVR) and have been suggested to be adversely affected by living at elevated altitude. We compared the pulmonary hemodynamic data in correlation with postoperative outcomes at the 3 centers of Denver, Edmonton, and Toronto at altitudes of 1604, 668, and 103 meters, respectively.

METHODS

Hemodynamic data at pre-bidirectional cavopulmonary anastomosis (BCPA) and pre-Fontan catheterization between 1995 and 2007 were collected. Death from cardiac failure or heart transplantation in the same period was used to define palliation failure.

RESULTS

There was no significant correlation between altitude (ranged from 1 to 2572 meters) and PVR, pulmonary artery pressure (PAP) or transpulmonary gradient (TPG) at pre-BCPA and pre-Fontan catheterization. BCPA failure occurred in 11 (9.2%) patients in Denver, 3 (2.9%) in Edmonton, and 34 (11.9%) in Toronto. Fontan failure occurred in 3 (6.1%) patients in Denver, 5 (7.2%) in Edmonton, and 11 (7.0%) in Toronto. There was no significant difference in BCPA and Fontan failure among the 3 centers. BCPA failure positively correlated with PVR and the presence of a right ventricle as the systemic ventricle. Fontan failure positively correlated with PAP and TPG.

CONCLUSIONS

Moderate altitude is not associated with an increased PVR or adverse outcomes in patients with a functional single ventricle undergoing BCPA and the Fontan operation. The risk factors for palliation failure are higher PVR, PAP, and TPG and a systemic right ventricle, but not altitude. Our study reemphasizes the importance of cardiac catheterization assessments of pulmonary hemodynamics before BCPA and Fontan operations.

Moving on up: is it safe for patients to relocate to higher altitude following the fontan procedure?

The change in clinical status of patients status post-Fontan surgery who relocated from low (<1,500 feet) to moderate (>4,000 feet) altitude was assessed. Cardiology databases were queried for patients meeting inclusion criteria. The clinical records of these patients for the 6 months before and 6 months after relocation were then reviewed. Between 1990 and 2010, 16 patients relocated to moderate altitude. All patients developed a new cardiac-related adverse event within 6 months of relocation. A decrease in New York Heart Association functional classification occurred in 15 (94 %) patients, and 11 (69 %) of these required hospitalization. Clinical deterioration at higher altitude is common in patients who have undergone Fontan surgery. Physicians at lower altitudes should caution these patients about the potential risks of relocation to moderate altitude.