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. 2018 Dec 17;20(1):85.
doi: 10.1186/s12968-018-0505-4.

Maldistribution of pulmonary blood flow in patients after the Fontan operation is associated with worse exercise capacity

Tarek Alsaied  1 , Lynn A Sleeper  1   2 , Marco Masci  1 , Sunil J Ghelani  1   2 , Nina Azcue  1 , Tal Geva  1   2 , Andrew J Powell  1   2 , Rahul H Rathod  3   4
Affiliations

Maldistribution of pulmonary blood flow in patients after the Fontan operation is associated with worse exercise capacity

Tarek Alsaied et al. J Cardiovasc Magn Reson. .

Abstract

Background: Maldistribution of pulmonary artery blood flow (MPBF) is a potential complication in patients who have undergone single ventricle palliation culminating in the Fontan procedure. Cardiovascular magnetic resonance (CMR) is the best modality that can evaluate MPBF in this population. The purpose of this study is to identify the prevalence and associations of MPBF and to determine the impact of MPBF on exercise capacity after the Fontan operation.

Methods: This retrospective single-center study included all patients after Fontan operation who had maximal cardiopulmonary exercise test (CPET) and CMR with flow measurements of the branch pulmonary arteries. MPBF was defined as > 20% difference in branch pulmonary artery flow. Exercise capacity was measured as percent of predicted oxygen consumption at peak exercise (% predicted VO2). Linear and logistic regression models were used to determine univariate and multivariable predictors of exercise capacity and correlates of MPBF, respectively.

Results: A total of 147 patients who had CMR between 1999 and 2017 were included (median age at CMR 21.8 years [interquartile range (IQR) 16.5-30.6]) and the median time between CMR and CPET was 2.8 months [IQR 0-13.8]. Fifty-three patients (36%) had MPBF (95% CI 29-45%). The mean % predicted VO2 was 63 ± 16%. Patients with MPBF had lower mean % predicted VO2 compared to patients without MPBF (60 ± 14% versus 65 ± 16%, p = 0.04). On multivariable analysis, a lower % predicted VO2 was independently associated with longer time since Fontan, higher ventricular mass-to-volume ratio, and MPBF. On multivariable analysis, only compression of the branch pulmonary arteries by the ascending aorta or aortic root was associated with MPBF (OR 6.5, 95% CI 5.6-7.4, p < 0.001).

Conclusion: In patients after the Fontan operation, MPBF is common and is independently associated with lower exercise capacity. MPBF was most likely to be caused by pulmonary artery compression by the aortic root or the ascending aorta. This study identifies MPBF as an important risk factor and as a potential target for therapeutic interventions in this fragile patient population.

Keywords: Cardiovascular magnetic resonance imaging; Congenital heart disease; Exercise capacity; Fontan procedure; Maldistribution of pulmonary blood flow.

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Conflict of interest statement

Ethics approval and consent to participate

The Boston Children’s Hospital Committee on Clinical Investigation approved this retrospective study and waived the requirement for informed consent.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
Cardiovascular magnetic resonance (CMR) example of different measurements used in our study. a Branch pulmonary artery (PA) flow measurement. b Branch PA cross-sectional area was calculated by measuring two orthogonal dimensions at the narrowest segment. c Left pulmonary artery (LPA) compression by a dilated ascending aorta. d Lung volume calculation by Simpson’s method using manual tracing in each slice on an axial image balanced steady-state free precession stack
Fig. 2
Fig. 2
Percentage difference in branch PA blood flow between the two branch PAs. The mean branch PA flow is 56% to the right PA. Green denotes no MPBF (%difference < 20); yellow denotes MPBF (%difference ≥ 20). MPBF: Maldistribution of pulmonary blood flow. PA: Pulmonary artery. PBF: Pulmonary blood flow
Fig. 3
Fig. 3
Association between branch PA flow percentage and lung volume percentage (a, b) and ipsilateral PA cross sectional area (c, d). N = 140. The estimate r denotes Pearson correlation coefficient. LPA: Left pulmonary artery. RPA: Right pulmonary artery. Log: Logarithmic transformation
Fig. 4
Fig. 4
Patients with maldistribution of pulmonary blood flow (MPBF, n = 53; yellow) had lower mean % predicted peak VO2 compared to patients with no MPBF (n = 94, green). Error bars denote one standard deviation
See this image and copyright information in PMC

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