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DOI: 10.1055/s-0040-1705537
Exercise Dependent Changes in Ventricular-Arterial Coupling and Aortopulmonary Collateral Flow in the Fontan Patients: A Real-Time CMR Study
Publication History
Publication Date:
13 February 2020 (online)
Objectives: Inefficient ventricular-arterial (V-A) coupling has been described in the Fontan patients that may result in adverse hemodynamics. A varying amount of aortopulmonary collateral (APC) flow is also frequently present that increases volume load of the single ventricle (SV). The aim of the study was to assess changes in V-A coupling and APC flow during exercise CMR.
Methods: The 18 Fontan patients (mean age, 24 ± 3 years, four females) and 14 healthy controls (mean age, 23 ± 4 years, five females, p = 0.17) underwent exercise CMR using a recumbent bicycle ergometer. Short-axis SV volumetry and 2D flow measurements in the ascending aorta (AAO), inferior vena cava (IVC), and superior vena cava (SVC) were assessed using real-time cine and phase-contrast sequences at baseline, 15, 30, 45, and 60 W work load. Measures of arterial elastance Ea (endsystolic pressure/stroke volume), ventricular elastance Ees (endsystolic pressure/endsystolic volume) and V-A coupling (Ea/Ees) were assessed. APC flow was quantified as AAO – (SVC + IVC).
Result: Ea did not differ between the two groups and remained unchanged during exercise in both groups, while the increase in Ees during exercise was significantly lower in the Fontan patients (1.1 ± 0.5 to 1.5 ± 0.8 vs. 1.2 ± 0.4 to 2.2 ± 1.0 mm Hg/mL/m2, p = 0.04). V-A coupling was significantly impaired in the Fontan patients at baseline (0.7 ± 0.2 vs. 0.5 ± 0.1, p = 0.04). Despite significant improvement during exercise, V-A coupling was still impaired compared with controls (0.5 ± 0.2 vs. 0.3 ± 0.1, p = 0.001). An attenuated increase in heart rate and cardiac output was observed in the Fontan group. Absolute APC flow in the Fontan patients did not change during exercise even at maximum work load (0.7 ± 0.5 to 0.8 ± 0.7 l/min/m2, p = 0.82).
Conclusion: Already at rest, the Fontan patients showed inefficient V-A coupling that was aggravated during exercise due to a restricted increase in ventricular contractility while APC flow remained unchanged. These results demonstrate the importance of a limited functional reserve of the SV but no further increase in volume load during exercise.