Cardiac output drop reflects circulatory attrition after Fontan completion: serial cardiac magnetic resonance study

Abstract

Aims: Cardiac magnetic resonance (CMR) imaging is a main diagnostic tool in the follow-up of Fontan patients. However, the value of serial CMR for the evaluation of Fontan attrition is unknown. The aim of this prospective study of serial CMR is to describe the analysis of time-dependent evolution of blood flow distribution, ventricular volumes, and function in patients after Fontan completion.

Methods and results: In this prospective single-centre study, between 2012 and 2022, 281 CMR examinations were performed in 88 Fontan patients with distribution of blood flows, measurements of ventricular volumes, and ejection fraction. Linear mixed model regression for repeated measurements was used to analyse changes of measurements across serial CMR examinations. During a time interval of 10 years, the median number of CMR per patient was 3 (range 1-5). Indexed flow of ascending aorta, caval veins, and pulmonary arteries decreased significantly across serial CMR examinations. Although a decrease of mean indexed aortic flow (3.03 ± 0.10 L/min/m² at first CMR vs. 2.36 ± 0.14 L/min/m² at fourth CMR, P < 0.001) was observed, ejection fraction did not decline (50 ± 1% at first CMR vs. 54 ± 2% at fourth CMR, P = 0.070). Indexed ventricular volumes did not differ significantly across serial CMR examinations.

Conclusion: The decrease of indexed aortic and cavopulmonary flows reflects the attrition of univentricular circulation and can be detected by means of serial CMR. Ventricular systolic dysfunction does not contribute significantly to this attrition. In order to detect significant change of indexed aortic flow, we recommend performing serial CMR as routine practice in the Fontan population.

Keywords: Fontan circulation; cardiac magnetic resonance; congenital heart disease; univentricular physiology.

Graphical Abstract

Decrease of indexed aortic and caval veins flows (Kaplan–Meier curves, Graph A) detected by means of serial CMR reflects attrition of univentricular circulation. The contribution of ventricular systolic dysfunction to this attrition is limited: Kaplan–Meier curves of indexed aortic flow and EF diverge remarkably (Graph B). We recommend performing serial CMR as routine practice in Fontan population to detect significant haemodynamic change. CMR, cardiac magnetic resonance; EF, ejection fraction.

Figure 1

CMR pictures that show the anatomical level of the measured blood flows. (A) RPA, direct distal from the cavopulmonary anastomosis and before the first pulmonary artery branch. (B) Ascending aorta, 1.5 cm above the aortic valve. (C) LPA, between the cavopulmonary anastomosis and the first pulmonary artery branch. (D) SCV, below the entrance of the azygos vein, if present. (E) ICV, between hepatic vein confluence and right atrium or conduit.

Figure 2

Kaplan–Meier curves of estimated indexed aortic flow ≥ 2.5 L/min/m² (A); estimated indexed caval veins flow ≥ 2 L/min/m² (B); estimated EF ≥ 35% (C); estimated HR ≥ 60 bpm (D). Shaded areas represent CI 95%. Time zero corresponds to date of Fontan completion.

Figure 3

(A) Kaplan–Meier curves of all estimated indexed volumes: ESV ≥ 30 mL/m², EDV ≥ 65 mL/m², and SV ≥ 35 mL/m². Kaplan–Meier curves of estimated indexed ESV ≥ 30 mL/m² (B), EDV ≥ 65 mL/m² (C), and SV ≥ 35 mL/m² (D). Shaded areas represent CI 95%. Time zero corresponds to date of Fontan completion.