Characterizing Pulmonary Artery Flow Patterns and Their Prognostic Significance in Patients with Fontan Palliation

Friday, February 6, 2026

3:45 PM - 3:52 PM

Location: Galapagos / Aruba / Ilhabela (2nd Lower Level)

Presenting Author(s)

Rithvik Gunda, BSc

Research Fellow
UT Southwestern
Irving, Texas, United States

Primary Author(s)

Rithvik Gunda, BSc

Research Fellow
UT Southwestern
Irving, Texas, United States

Co-Author(s)

SE

Sukran Erdem, MD

Research Assistant
UT Southwestern Medical Center
Dallas, Texas, United States
MH

Mohammad Tarique Hussain, MD, PhD

Professor of Pediatric Cardiology and Radiology
The University of Texas Southwestern Medical Center, United States

Background: The Fontan procedure is the definitive palliative strategy for patients with single-ventricle physiology, directing systemic venous return directly to the pulmonary arteries without a subpulmonary ventricle [1]. This unique circulation produces passive, pressure-dependent pulmonary blood flow (PBF) and alters the hemodynamics of the branch pulmonary arteries [2]. Cardiovascular magnetic resonance (CMR) is central to the longitudinal evaluation of Fontan patients [3], yet the clinical significance of PBF patterns remains incompletely understood [4–8]. This study aimed to characterize PBF patterns using phase-contrast CMR and to investigate their association with adverse outcomes and established prognostic markers.

Methods: 288 patients with Fontan palliation (median age 13 years, range 4–39; 60% male) who underwent clinically indicated CMR were retrospectively analyzed. Pulmonary artery flow was assessed using two-dimensional phase-contrast imaging, with flow patterns categorized as phasic, continuous, late systolic flow cessation, or late systolic flow reversal (Fig. 1). Clinical outcomes (death, heart transplantation, listing for transplantation, or referral for transplant evaluation) were documented over a median follow-up of 36 months (range 1 to 100 months). CMR-derived volumetric indices, aortopulmonary collateral (APC) burden, and atrioventricular valve (AVV) regurgitation were quantified and correlated with PBF patterns.

Results: Late systolic flow reversal or late systolic flow cessation was identified in 28 patients (9.7%; 9 with late systolic reversal, 19 with late systolic flow cessation), while 260 (90.3%) demonstrated normal phasic or continuous flow (Table 1). Adverse outcomes occurred in 35 patients (12.2%) and were significantly more common in those with late systolic flow reversal or cessation (42.8% vs. 8.0%; p < 0.01) (Fig. 2). Patients with late systolic flow reversal or cessation exhibited significantly larger ventricular volumes (mean EDVi 155.3 vs. 105 mL/m²; mean ESVi 88 vs. 56 mL/m²; (both p < 0.001), while ejection fraction trended lower (45% vs. 48%, p = 0.11) (Table 2). Late systolic flow reversal or cessation further correlated with severe APC burden, severe AVV regurgitation, abnormal differential PBF and saturations (all p < 0.01). Multivariate analysis showed that only indexed end-systolic volume was an independent predictor of outcome (HR 1.03, p< 0.01). 15 Patients showed early systolic flow reversal, but this pattern showed no association with adverse outcomes.

Conclusion: End-systolic pulmonary artery flow cessation or reversal are present in approximately 10% of Fontan patients and this is strongly associated with ventricular volumes, AVV regurgitation,

collateral burden and saturations and outcome. However, on multivariate analysis, the only independent predictor of outcome was indexed end-systolic volume.

Table 1. Patient Characteristics, Cardiovascular Magnetic Resonance (CMR)-derived data and Clinical Outcomes

	N	Percentage/Median
Gender (Male)	174	60.2%
Age at the time of CMR acquisition (years)	Range 4-39	13
Follow-up time after CMR acquisition (months)	Range 1-120	36
Fontan type Extracardiac Lateral Tunnel Atriopulmonary Unknown	218 54 2 14	75.7% 18.7% 0.7% 4.9%
Systemic Ventricle Right Ventricle Left Ventricle	173 115	60% 40%
Congenital Heart Disease Diagnosis HLHS PA/IVS Tricuspid atresia Others	125 14 33 116	44% 5% 11% 40%
Pulmonary Blood Flow Pattern Normal Abnormal -Late systolic flow reversal -Late systolic flow reaching baseline	260 9 19	90.27% 3.12% 6.25%
Antegrade P</span>ulmonary Blood Flow Distribution Normal Branch Pulmonary Artery Stenosis	254 34	88% 12%
Atrioventricular valve regurgitation Severe Less than severe	13 275	4% 96%
Aortopulmonary Collateral Burden < 30% ≥30%	242 46	84% 16%
Clinical Outcomes Alive Dead Heart transplanted On heart transplant list Referred for heart transplant evaluation	253 7 13 12 3	87.8% 2.43% 4.51% 4.16% 1.04%

HLHS: Hypoplastic Left Heart Syndrome, PA/IVS: Pulmonary Atresia and Intact Ventricular Septum Table 2. Comparison of CMR-Derived Metrics, Clinical Outcomes, and Fontan Characteristics Between Patients with Abnormal Pulmonary Blood Flow (Late Systolic Flow reaching baseline and late systolic flow reversal) and Normal Flow Patterns (Continuous and Biphasic)

	Mean/N	P value
Clinical Outcomes		< 0.001
Late systolic flow reversal or reaching baseline Adverse Clinical Outcomes Alive Normal Adverse Clinical Outcome Alive	12/28 16/28 23/260 237/260
EDVi (ml/m2)		< 0.001
Late systolic flow reversal or reaching baseline Normal	155.28 104.8
ESVi (ml/m2)		0.0007
Late systolic flow reversal or reaching baseline Normal	87.58 55.93
EF %		0.11
Late systolic flow reversal or reaching baseline Normal	45.4 48.4
Aortopulmonary Collateral Burden >30%		< 0.001
Late systolic flow reversal & reaching baseline Normal	12/28 22/260
Abnormal differential P</span>ulmonary Artery Flow		0.003
Late systolic flow reversal & reaching baseline Normal	8/28 26/260
O2 Saturation < 90%		< 0.001
Late systolic flow reversal & reaching baseline Normal	18/28 60/260
Severe Atrioventricular Valve Regurgitation		0.0003
Late systolic flow reversal & reaching baseline Normal	5/28 8/260
Fontan Type		< 0.001
Lateral Tunnel Fontan Late systolic flow reversal & reaching baseline Normal Extracardiac Fontan Late systolic flow reversal & reaching baseline Normal	6/54 48/54 20/218 198/218

EDVi: End-diastolic volume index, ESVi : End-systolic volume index, EF: Ejection Fraction, ml/m2: milliliter/square meter, O2: Oxygen. Fig. 1 Pulmonary artery blood flow patterns. The upper left panel demonstrates phasic flow, while the upper right panel illustrates continuous flow. The lower left panel depicts late systolic flow reversal, and the lower right panel shows late systolic flow returning to baseline.

Fig. 2 Association between pulmonary blood flow (PBF) patterns and clinical outcomes in patients with Fontan circulation. Patients with continuous or phasic flow patterns (blue) were predominantly alive, whereas those with abnormal PBF patterns (late systolic flow reversal or late systolic flow reaching baseline; orange) demonstrated a higher proportion of adverse clinical outcomes.