Noninvasive Assessment of Right Ventricular-Pulmonary Arterial Coupling in Repaired Tetralogy of Fallot by Magnetic Resonance Imaging.

BACKGROUND: Right ventricular (RV) to pulmonary arterial coupling (RVPAc) quantifies RV contractility in relation to its afterload but traditionally requires high-fidelity catheter derived pressure-volume loops. We sought to evaluate a noninvasive volume-based RVPAc parameter in children and adults with repaired tetralogy of Fallot in relation to pulmonary regurgitation (PR), RV outflow tract obstruction (RVOTO), and exercise capacity.

METHODS: We retrospectively studied 92 pediatric and 105 adult patients with repaired tetralogy of Fallot who had cardiovascular magnetic resonance imaging and cardiopulmonary exercise testing within a 1-year interval. RVPAc was calculated as the ratio of RV end-systolic volume over stroke volume. RVOTO gradient was obtained by echocardiography; RV ejection fraction, and PR fraction by cardiovascular magnetic resonance imaging. Exercise capacity was measured as the percentage of predicted peak oxygen consumption during cardiopulmonary exercise testing. Subgroups were established depending on the combination of PR-RVOTO (cutoff defined as PR >30% and RVOTO >25 mm Hg).

RESULTS: RVPAc was significantly higher in adult versus pediatric patients (1.23 [1.03-1.48] versus 1.00 [0.88-1.15]; P<0.001). RVPAc was comparable in the 4 pediatric hemodynamic subgroups (P=0.38) but tended to be higher in adults with either RVOTO, PR, or RVOTO+PR (P=0.05). RVPAc highly correlated with RVEF (r=-0.991, P<0.001) but was not associated with percentage of predicted peak oxygen consumption.

CONCLUSIONS: Worse RVPAc in adult versus pediatric patients with repaired tetralogy of Fallot may signify progressive RV-PA uncoupling with age- or era-related effects. However, the clinical use of volumetric RVPAc in repaired tetralogy of Fallot appears limited, as it does not provide additional information over RVEF and is not associated with exercise capacity.