ABSTRACT
AIMS: Inefficient ventricular-arterial (V-A) coupling has been described in Fontan patients and may result in adverse haemodynamics. A varying amount of aortopulmonary collateral (APC) flow is also frequently present that increases volume load of the single ventricle. The aim of the study was to assess changes in V-A coupling and APC flow during exercise CMR. METHODS AND RESULTS: Eighteen Fontan patients (age 24 ± 3 years) and 14 controls (age 23 ± 4 years) underwent exercise CMR using a cycle ergometer. Ventricular volumetry and flow measurements in the ascending aorta (AAO), inferior (IVC), and superior (SVC) vena cava were assessed using real-time sequences during stepwise increases in work load. Measures of systemic arterial elastance Ea, ventricular elastance Ees, and V-A coupling (Ea/Ees) were assessed. APC flow was quantified as AAO - (SVC + IVC). Ea remained unchanged during all levels of exercise in both groups (P = 0.39 and P = 0.11). Ees increased in both groups (P = 0.001 and P < 0.001) with exercise but was lower in the Fontan group (P = 0.04). V-A coupling was impaired in Fontan patients at baseline (P = 0.04). Despite improvement during exercise (P = 0.002) V-A coupling remained impaired compared with controls (P = 0.001). Absolute APC flow in Fontan patients did not change during exercise even at maximum work load (P = 0.98). CONCLUSIONS: Inefficient V-A coupling was already present at rest in Fontan patients and aggravated during exercise due to a limited increase in ventricular contractility which demonstrates the importance of a limited functional reserve of the single ventricle. APC flow remained unchanged suggesting no further increase in volume load during exercise.
Subject(s)
Fontan Procedure , Humans , Young Adult , Adult , Arteries , Heart Ventricles , Hemodynamics , AortaABSTRACT
BACKGROUND: Single ventricle (SV) patients with a Fontan circulation are at risk for functional deterioration. The aim of this study was to assess longitudinal Fontan hemodynamics using serial cardiovascular magnetic resonance (CMR) data and to study the impact of aortopulmonary collateral (APC) flow and type of SV morphology. METHODS: Forty-one Fontan patients (age at first CMR 13.4 ± 6.0 years) with two CMR examinations within a time interval of at least 4 years (follow-up 5.3 ± 0.9 years) were included. The protocol consisted of short-axis cine volumetry and 2-dimensional blood flow measurements in the inferior vena cava (IVC), superior vena cava (SVC) and ascending aorta (Ao). APC flow was calculated as Ao - (SVC + IVC). Myocardial strain/strain rate was assessed using feature tracking technique. RESULTS: SV end-diastolic volume (p = 0.14) and ejection fraction (p = 0.70) remained constant. No significant changes in CMR derived myocardial strain/strain rate values were observed. Ao flow decreased (p = 0.01), IVC flow remained unchanged (p = 0.52), while SVC flow (p = 0.003) and APC flow (p = 0.006) decreased significantly. Patients with a systemic right ventricle (RV) showed unchanged APC flow and a further increase in SV size over time compared to patients with a systemic left ventricle. CONCLUSIONS: Longitudinal CMR data in a cohort of clinically stable Fontan patients revealed no significant changes in SV dimensions and myocardial performance while APC flow decreased spontaneously. Patients with a systemic RV seem to be at risk for permanent SV volume overload through APCs and might therefore benefit from consequent interventional APC embolization.
