Determinants and functional impact of restrictive physiology after repair of tetralogy of Fallot: New insights from magnetic resonance imaging

Background: The presence of end-diastolic forward flow (EDFF) in the pulmonary arteries is commonly regarded as a hallmark of restrictive physiology of the right ventricle (RV) which, in turn, has been associated with a better long-term prognosis in patients after TOF repair. However, controversy persists over the beneficial clinical consequences of restrictive physiology. We aimed at determining the clinical relevance of restrictive physiology late after TOF repair. Methods: Fifty magnetic resonance examinations of 50 patients (age 13.0 ± 2.8 years, 26 males) with repaired TOF were evaluated. The patients were divided into: Group-1 with and Group-2 without EDFF; Group-A with smaller RVs (< 170 ml/m2) and Group-B with larger RVs (≥ 170 ml/m2). Maximum oxygen consumption as percent of predicted (VO₂max-pred) at a recent exercise test was recorded. Results: Groups-1 and 2 did not differ with regard to their right ventricular end-diastolic volume, pulmonary regurgitant volume, or QRS duration. Patients in Group-1 had a higher VO₂max-pred than patients in Group-2 (70.3% versus 54.7% of predicted, p < 0.01). In Group-1A versus 2A (RV < 170 ml/m², with and without EDFF) this difference persisted, but in Group B there was no difference in VO₂max-pred between patients with and without EDFF. The flow volume of EDFF correlated with VO₂max-pred (r = 0.444, p = 0.007). Conclusions: End-diastolic forward flow measured by magnetic resonance is present in patients with small and large RVs. The presence of EDFF is associated with better exercise tolerance, but only in patients with relatively small RVs.