Influence of pulmonary regurgitation inequality on differential perfusion of the lungs in tetralogy of Fallot after repair: a phase-contrast magnetic resonance imaging and perfusion scintigraphy study.
OBJECTIVE
The purpose of this study was to evaluate the influence of pulmonary regurgitation inequality on differential perfusion of the lungs in tetralogy of Fallot (TOF) after repair.


BACKGROUND
Asymmetry of lung perfusion is one of the best predictors of outcome in TOF after repair. A recent phase-contrast magnetic resonance imaging (PC-MRI) study found prominent regurgitation inequality between the bilateral pulmonary arteries in TOF after repair.


METHODS
Forty-three TOF post-repair patients (median age = 51 months, 31 men) received PC-MRI and 99mTc-labeled macroaggregates of albumin perfusion scintigraphy (PS) in the same day. We took PC-MRI measurements of forward flow volume (FFV), backward flow volume (BFV), and net flow volume (NFV) (NFV = FFV - BFV) and regurgitation fraction (RF) (RF = BFV/FFV) at the left and right pulmonary arteries (LPA and RPA). The differential perfusion of the left lung (L%) (L% = left lung/left + right lung) as calculated by NFV ratio, by FFV ratio of PC-MRI, and by PS were compared.


RESULTS
The discrepancy between L% by NFV versus L% by PS was affected by the severity of RF of LPA (r = -0.51, p = 0.001); agreement between L% by NFV versus L% by PS was good (intraclass correlation coefficient [Ri] = 0.87) if RF of LPA <0.4 (n = 23) but downgraded (Ri = 0.51) and underestimated the L% (median of error = -14%, range = -25.3% to 5.5%) if RF of LPA > or =0.4 (n = 20). In contrast, agreement between L% by FFV versus L% by PS was high and unaffected by RF of LPA (Ri = 0.94, 0.92, respectively).


CONCLUSIONS
While integrating PC-MRI of pulmonary artery as a comprehensive MRI evaluation of TOF after repair, conventional NFV ratio method tended to underestimate the left lung perfusion and may lead to unnecessary intervention. The FFV ratio method should be used for precise assessment of differential lung perfusion.
Wu
Ming-Ting
MT
Faculty of Medicine, School of Medicine, National Yang Ming University, Taipei, Taiwan, ROC. wu.mingting@gmail.com
Huang
Yi-Luan
YL
Hsieh
Kai-Sheng
KS
Huang
Ju-Tung
JT
Peng
Nan-Jing
NJ
Pan
Jun-Yen
JY
Huang
Jer-Shyung
JS
Yang
Tsung-Lung
TL
D001783:Blood Flow Velocity; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008168:Lung / Q000098:blood supply / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging; D008297:Male; D011184:Postoperative Period; D011446:Prospective Studies; D011651:Pulmonary Artery / Q000000981:diagnostic imaging*; D011652:Pulmonary Circulation; D011877:Radionuclide Imaging; D012039:Regional Blood Flow; D013771:Tetralogy of Fallot / Q000503:physiopathology / Q000601:surgery*