Abstract |
Purpose: Determination of pulmonary to systemic blood flow ratio (QP/QS) is important for the management of
patients with left-to-right shunt. This study was performed to assess the agreement of Qp/Qs ratio using the
radionuclide method and oxymetry, to investigate the factors influencing the agreement, and to know how
interchangeable the results of each technique. Materials and Methods: We compared the Qp/Qs measured by
single-pass radionuclide angiocardiography and oxymetry during catheterization in 207 patients who underwent
both studies. In radionuclide method, Qp/Qs was calculated from the pulmonary time-activity curves using a
gamma variate fit. The correlation and Bland-Altman analysis were performed according to the levels of shunt and
associated lesions. Results: The mean Qp/Qs was 1.83¡¾0.50 by radionuclide, and 1.74¡¾0.51 by oxymetry. The
overall correlation coefficient was 0.86(p<0.001), and Bland-Altman range of agreement encompassing 4SD was 1.05.
For atrial septal defect, ventricular septal defect, patent ductus arteriosus, tricuspid and mitral insufficiency, the
correlation coefficient was 0.78, 0.90, 0.84, 0.63 and 0.44, and Bland-Altman range was 1.52, 0.74, 0.96, 1.57, and
1.50, respectively. Conclusion: There is good agreement but wide variance between the Qp/Qs ratios by
radionuclide method and oxymetry. Associated atrioventricular valvar insufficiency decreases the correlation
coefficient and widens the variance. Wide overall variance suggests that Qp/Qs measurements by two techniques
should not be used interchangeably. (Nucl Med Mol Imaging 2006;40(4):200-204)
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