Correlation Between Fontan Pathway Diameter and Inferior-Superior Vena Cava Gradients in Adults Undergoing Exercise Catheterization

Fontan haemodynamics in adults with obesity compared with overweight and normal body mass index: a retrospective invasive exercise study

AIMS

The effects of obesity on Fontan haemodynamics are poorly understood. Accordingly, we assessed its impact on exercise invasive haemodynamics and exercise capacity.

METHODS AND RESULTS

Seventy-seven adults post-Fontan undergoing exercise cardiac catheterization (supine cycle protocol) were retrospectively identified using an institutional database and categorized according to the presence of obesity [body mass index (BMI) > 30 kg/m2] and overweight/normal BMI (BMI ≤ 30 kg/m2). There were 18 individuals with obesity (BMI 36.4 ± 3 kg/m2) and 59 with overweight/normal BMI (BMI 24.1 ± 3.6 kg/m2). Peak oxygen consumption (VO2) on non-invasive cardiopulmonary exercise testing was lower in patients with obesity (15.6 ± 3.5 vs. 19.6 ± 5.8 mL/kg/min, P = 0.04). At rest, systemic flow (Qs) [7.0 (4.8; 8.3) vs. 4.8 (3.9; 5.8) L/min, P = 0.001], pulmonary artery (PA) pressure (16.3 ± 3.5 vs. 13.1 ± 3.5 mmHg, P = 0.002), and PA wedge pressure (PAWP) (11.7 ± 4.4 vs. 8.9 ± 3.1 mmHg, P = 0.01) were higher, while arterial O2 saturation was lower [89.5% (86.5; 92.3) vs. 93% (90; 95)] in obesity compared with overweight/normal BMI. Similarly, patients with obesity had higher exercise PA pressure (29.7 ± 6.5 vs. 24.7 ± 6.8 mmHg, P = 0.01) and PAWP (23.0 ± 6.5 vs. 19.8 ± 7.3 mmHg, P = 0.047), but lower arterial O2 saturation [82.4 ± 7.0% vs. 89% (85; 92), P = 0.003].

CONCLUSION

Adults post-Fontan with obesity have worse aerobic capacity, increased Qs, higher filling pressures, and decreased arterial O2 saturation compared with those with overweight/normal BMI, both at rest and during exercise, mirroring the findings observed in the obesity phenotype of heart failure with preserved ejection fraction. Whether treating obesity and its cardiometabolic sequelae in Fontan patients will improve haemodynamics and outcomes requires further study.

Novel lateral tunnel Fontan operation in children promotes continued pathway growth into adulthood

Objective

Most Fontan operation techniques currently used in children are limited by a blood flow pathway with no growth potential. The external pericardial lateral tunnel Fontan is a novel technique using the patient's pedicled pericardium and atrial wall in situ to create a Fontan pathway. We hypothesize that viable, autologous tissue will allow growth potential of the pathway and adapt to increasing physiologic demands of somatic growth.

Methods

We performed a single-center retrospective review of serial echocardiographic measurements of the inferior vena cava junction and mid tunnel in patients with an external pericardial lateral tunnel Fontan. Linear mixed model and Pearson correlation tests were used for analysis of changes in pathway size with time and body surface area.

Results

A total of 1592 echocardiographic studies from 172 patients up to 23 years after the procedure were identified. Significant enlargement of the pathway at the inferior vena cava junction and mid tunnel was observed over time (P < .0001, P < .0001, respectively). There is a strong positive correlation between increasing size of the inferior vena cava junction and increasing body surface area (R = 0.81, P < .0001). There is also a strong positive correlation between increasing size of the mid tunnel with increasing body surface area (r = 0.67, P < .0001).

Conclusions

The external pericardial lateral tunnel Fontan technique creates a Fontan pathway that enlarges into adulthood. The correlation of increasing pathway size with increasing body surface area suggests pathway growth, responding to increasing physiologic demands of somatic growth into adulthood. Further studies are needed to investigate the impact of this novel technique on Fontan physiology and long-term patient outcomes.

Advances in Diagnostic and Interventional Catheterization in Adults with Fontan Circulation

Over the past five decades, the Fontan procedure has been developed to improve the life expectancy of patients with congenital heart defects characterized by a functionally single ventricle. The Fontan circulation aims at redirecting systemic venous return to the pulmonary circulation in the absence of an impelling subpulmonary ventricle, which makes this physiology quite fragile and leads to several long-term complications. Despite the importance of hemodynamic assessment through cardiac catheterization in the management and follow-up of these patients, a thorough understanding of the ultimate functioning of this type of circulation is lacking, and the interpretation of the hemodynamic data is often complex. In recent years, new tools such as combined catheterization with cardiopulmonary exercise testing have been incorporated to improve the understanding of the hemodynamic profile of these patients. Furthermore, extensive percutaneous treatment options have been developed, addressing issues ranging from obstructive problems in Fontan pathway and acquired shunts through compensatory collaterals to the percutaneous treatment of lymphatic circulation disorders and transcatheter edge-to-edge repair of atrioventricular valves. The aim of this review is to detail the various tools used in cardiac catheterization for patients with Fontan circulation, analyze different percutaneous treatment strategies, and discuss the latest advancements in this field.

Exercise catheterization in adults post-Fontan with normal and abnormal haemodynamic criteria: Insights into normal Fontan physiology

AIM

The normal (i.e. expected) haemodynamics in adults post-Fontan remain poorly delineated. Moreover, the definitions of elevated exercise pulmonary artery (PA) and PA wedge pressure (PAWP) for this population have not been described.

METHODS AND RESULTS

Seventy-two adults post-Fontan undergoing exercise catheterization were categorized into abnormal (Group I, n = 59; defined as resting mean PA ≥14 mmHg and/or PAWP ≥12 mmHg, ΔPAWP/Δsystemic flow [Qs] >2 mmHg/L/min, and/or ΔPA/Δpulmonary flow >3 mmHg/L/min) and normal (Group II, n = 13) haemodynamics. Thirty-nine patients with non-cardiac dyspnoea (NCD) were included as controls. There was no difference in exercise arterial oxygen saturation (87% [81-92] vs. 89% [85-93], p = 0.29), while exercise PA pressure (27 [23-31] vs. 16 [14.5-19.5] mmHg, p < 0.001) and PAWP were higher (21 [18-28] vs. 12 [8-14] mmHg, p < 0.001) in Group I. At peak exercise, Group I had lower heart rate (97 [81-120] vs. 133 [112.5-147.5] bpm, p < 0.001) and Qs response (67.3 [43.8-93.1] vs. 105.9 (82-118.5) % predicted, p < 0.001) than Group II. Exercise superior vena cava pressures were higher (16 [14-22.5] vs. 5.5 [3-7.3] mmHg, p < 0.001) and arterial oxygen saturation lower (89% [85-93] vs. 97% [96-98], p < 0.001) in Group II compared to NCD, while no differences in PAWP, stroke volume index, heart rate, or Qs response were seen. If defined as two standard deviations above mean values for Group II, elevated PAWP and mean PA pressure post-Fontan would correspond to 20.6 mmHg and 25.8 mmHg, respectively.

CONCLUSION

PAWP >20 mmHg and mean PA pressure >25 mmHg could be used to define elevated values during exercise in adults post-Fontan. The major discrepancy in exercise haemodynamics among Group II compared to controls appears to be the degree of systemic venous hypertension and arterial desaturation.