Magnetic resonance stress-perfusion comparison in patients with Fontan circulation of left- or right systemic ventricular morphology

Background: In patients with Fontan circulation, the cardiac output (CO) is decreased compared to biventricular circulation. A single ventricle is responsible for both systemic and pulmonary circulations which limits the heart’s capacity to augment CO during periods of increased metabolic demand, mainly because of increased central venous pressure and decreased diastolic filling. The coronary perfusion and its contribution have been less investigated. Therefore, the objectives of this study were to; 1) test feasibility and safety of adenosine stress-perfusion; 2) compare stress-perfusion, perfusion reserve, and global longitudinal strain (GLS) in left- (LV) versus right (RV) ventricular morphology and 3) explore the relationship between stress-perfusion and maximal oxygen consumption (VO2 max).

Methods: Patients with Fontan circulation and a total cavo-pulmonary connection (TCPC) (n=28, median age=25 (95% CI, 21.9 to 28.1), 46% female) were prospectively enrolled between April 2024 and June 2025. The cohort was stratified into two groups based on LV or RV ventricle morphology. All imaging were performed using a 1.5T magnetic resonance (MR) scanner (MAGNETOM, Sola, Siemens Healthineers, Forchheim, Germany). Quantitative perfusion mapping was performed using a research sequence in a single short-axis and long-axis slice using first-pass perfusion (0.05 mmol/kg gadobutrol; Gadovist, Bayer AB) imaging during adenosine infusion at 110 μg/kg/min, with titration up to 170 μg/kg/min if necessary (Adenosin, Life Medical AB, Sweden). Cardiopulmonary exercise testing (CPET) was conducted to assess VO2 max. Mann-Whitney U test was performed to compare independent samples and Spearman’s test for correlations.

Results: 16 patients, 25 years old (95% CI, 20.3 to 29.7), n=8 (50%) female) had LV morphology and 12 patients, 26 years old (95% CI, 21.0 to 30.0), n=5 (42%) female) had RV morphology. There was no serious adverse events; all recruited patients completed the MR study protocol. Analysis between the LV and RV groups showed better GLS (p=0.003) and a trend to higher systemic EF (p=0.07) in patients with LV morphology. There was no significant difference in perfusion during stress (p=0.19), rest (p=0.24) and perfusion reserve (p=0.87) between the groups (Table 1, Figure 1). No significant correlations were observed between stress-perfusion or perfusion reserve regarding VO2 max.

Conclusion: Adenosine quantitative stress-perfusion in patients with Fontan circulation and TCPC was feasible and safe with no serious adverse events. Quantitative perfusion during adenosine and rest was within the normal range from our hospital (1). Thus, we found no evidence of affected coronary circulation in Fontan patients. Ventricular morphology did not affect perfusion but GLS was significantly better in patients with LV morphology, confirming that patients with RV morphology exhibits reduced myocardial function. However, VO2 max did not differ between ventricular morphology and perfusion was not related to VO2 max.

Demographic, CMR findings and CPET parameters in left and right ventricular morphology

	LV n=16 (100)	RV n=12 (100)	P-value
Female (%)	8 (50)	5 (42)	NA
Age (year)	25.0 (20.3-29.7)	25.5 (21.0-30.0)	0.98
Stress perfusion (mL/min/g)	3.2 (2.7-3.6)	3.7 (3.0-4.4)	0.19
Rest perfusion (mL/min/g)	0.8 (0.7-0.9)	0.9 (0.7-1.1)	0.24
Perfusions reserve	4.0 (3.5-4.5)	3.9 (3.2-4.6)	0.87
GLS (-%)	17.9 (16.3-19.4)	13.8 (12.7-14.9)	0.003
EF (%)	55 (49-60)	48 (45-51)	0.07
VO₂ max (ml/(kg x min)	26.6 (23.0-30.2)	23.0 (17.8-28.2)	1.00

Demographics, CMR (cardiac magnetic resonance) findings and cardiopulmonary exercise testing (CPET) parameters divided into patients with left ventricle (LV) and right ventricle (RV) morphology. Data is presented as median (95% confidence interval) or n (%). Mann-Whitney U was used to calculate p-values. EF= ejection fraction; GLS=global longitudinal strain.Upper panel: stress-perfusion in mL/min/g. Lower panel: rest-perfusion. Patient with left ventricular (left four images), right ventricular (right four images) morphology. LAX=long axis ; LV= left ventricular; RV=right ventricular; SAX=short axis.