Vicious circle between progressive right ventricular dilatation and pulmonary regurgitation in patients after tetralogy of Fallot repair? Right heart enlargement promotes flow reversal in the left pulmonary artery.
The left pulmonary artery (LPA) contributes more than the right (RPA) to total pulmonary regurgitation (PR) in patients after tetralogy of Fallot (TOF) repair, but the mechanism of this difference is not well understood. This study aimed to analyze the interplay between heart and lung size, mediastinal geometry, and differential PR.



Forty-eight Cardiovascular Magnetic Resonance (CMR) studies in patients after TOF repair were analyzed. In addition to the routine blood flow and ventricular volume quantification cardiac angle between the thoracic anterior-posterior line and the interventricular septum, right and left lung areas as well as right and left hemithorax areas were measured on an axial image. Statistical analysis was performed to compare flow parameters between RPA and LPA and to assess correlation among right ventricular volume, pulmonary blood flow parameters and lung area.



There was no difference between LPA and RPA diameters. The LPA showed significantly less total forward flow (2.49 ± 0.87 L/min/m(2) vs 2.86 ± 0.89 L/min/m(2); p = 0.02), smaller net forward flow (1.40 ± 0.51 vs 1.89 ± 0.60 mL/min/m(2); p = <0.001), and greater regurgitant fraction (RF) (34 ± 10 % vs 43 ± 12 %; p = 0.001) than the RPA. There was no difference in regurgitant flow volume between RPA and LPA (p = 0.29). Indexed right ventricular end-diastolic volume (RVEDVi) correlated with LPA RF (R = 0.48, p < 0.001), but not with RPA RF (p = 0.09). Larger RVEDVi correlated with a more leftward cardiac axis (R = 0.46, p < 0.001) and with smaller left lung area (R = -0.58, p < 0.001). LPA RF, but not RPA RF, correlated inversely with left lung area (R = -0.34, p = 0.02). The follow-up CMRs in 20 patients showed a correlation of the rate of RV enlargement with the rates of LPA RF worsening (R = 0.50, p = 0.03), and of increasing left lung compression (R = -0.55, p = 0.012).



An enlarged and levorotated heart is associated with left lung compression and impaired flow into the left lung.
Division of Cardiology, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, 555 University Ave, Toronto, M5G 1X8, ON, Canada.
Atsuko
A
Kato
Division of Cardiology, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, 555 University Ave, Toronto, M5G 1X8, ON, Canada.|now: Université Laval, Quebec City, QC, Canada.
Christian
C
Drolet
Division of Cardiology, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, 555 University Ave, Toronto, M5G 1X8, ON, Canada.|Department of Diagnostic Imaging, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada.
Shi-Joon
SJ
Yoo
Division of Cardiology, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, 555 University Ave, Toronto, M5G 1X8, ON, Canada.|now: Heart Institute, Cincinnati Children's Hospital, Cincinnati, OH, USA.
Andrew N
AN
Redington
Division of Cardiology, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, 555 University Ave, Toronto, M5G 1X8, ON, Canada. lars.grosse-wortmann@sickkids.ca.|Department of Diagnostic Imaging, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada. lars.grosse-wortmann@sickkids.ca.
Lars
L
Grosse-Wortmann
D000293:Adolescent; D001783:Blood Flow Velocity; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D002648:Child; D005260:Female; D006439:Hemodynamics; D006801:Humans; D017380:Hypertrophy, Right Ventricular / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D011651:Pulmonary Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011652:Pulmonary Circulation; D011665:Pulmonary Valve Insufficiency / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology; D012189:Retrospective Studies; D013771:Tetralogy of Fallot / Q000503:physiopathology / Q000601:surgery*; D013997:Time Factors; D016896:Treatment Outcome; D016278:Ventricular Function, Right
Cardiovascular magnetic resonance; Differential pulmonary blood flow; Pulmonary regurgitation; Right ventricular enlargement; Tetralogy of Fallot