Objective To assess pulmonary flow dynamics and right ventricular (RV) function in patients without significant anatomical narrowing of the pulmonary arteries late after the arterial switch operation (ASO) by using magnetic resonance imaging (MRI).
Methods Seventeen patients (16.5±3.6 years after ASO) and 17 matched healthy subjects were included. MRI was used to assess flow across the pulmonary trunk (PT), RV systolic and diastolic function and mass.
Results Increased peak-flow velocity (>1.5 m/sec) was found across the PT in 14 of 17 patients. Increased RV mass was found in ASO patients: 14.9gram/m2±3.4 versus 10.0gram/m2±2.6 in normal subjects, P<0.01. Also, delayed RV relaxation was found after ASO: mean tricuspid valve E/A peak-flow velocity ratio was 1.60±0.96 versus 1.92±0.61 in normal subjects (P=0.03) and E-deceleration gradients were -1.69±0.73 versus -2.66±0.96, P<0.01. After ASO, RV mass correlated with PT peak-flow velocity (r=0.49, P<0.01) and tricuspid valve E-deceleration gradients (r=0.35, P=0.04). RV systolic function was well preserved in patients: ejection fraction was 53%±7 versus 52%±8 in normal subjects, P=0.72.
Conclusions Increased peak-flow velocity in the PT was frequently observed late after ASO, even in the absence of significant pulmonary artery stenosis. Hemodynamic consequences were RV hypertrophy and RV relaxation abnormalities as early markers of disease, whereas systolic RV function was still well preserved.
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