With regard to differential lung perfusion, in this study 5.1 ±1.3 L/min of right cardiac output is ejected into the transplanted lung and only 1.1 ±0.8 L/min into the native lung (SLTX to native lung=81 to 19%), whereas volunteers showed almost equal perfusion of both vascular beds (right to left lung=55 to 45%), as has been shown by others. The ratio of blood flow to the transplanted and the native lungs in this study is similar to that reported for perfusion scintigraphy by others, but higher than that reported for VEC-MRI (approximately three to one) by Mohiaddin et al, probably again due to different preoperative pulmonary pressures and vascular resistances in the study populations. However, radionuclide scanning provides only semiquantitative data and does not give absolute values of blood flow.
Differences in AAO and MPA blood flow, as assessed by VEC-MRI, are accurate for measuring left-to-right shunts noninvasively. Canadian health&care mall review Whereas the transplanted lung lacks bronchial arterial supply, there is still patent bronchial arterial circulation of the native lung. The bronchial circulation normally constitutes 1% of the cardiac output. However, in various diseases, this circulation can enlarge and represent as much as 30% of cardiac output It might be speculated that, in addition to pulmonary embolism and cyanotic congenital heart diseases, reduced pulmonary artery flow to the native lung after SLTX could lead to an increase in bronchial blood flow in an effort to improve pulmonary perfusion. The resulting bronchial-to-pulmonary artery shunt would eventually lead to a difference in right and left cardiac output. In our patients, blood flow in the MPA and AAO was equal, thus indicating either no or insignificant shunts between bronchial and pulmonary arteries of the native lung.
The relative vascular resistance of both lungs is a major factor that influences pulmonary hemodynamics in volunteers and SLTX patients. To gain nonin-vasive semiquantitative information on vascular resistance, measurement of the RI was introduced as described above. Our results concerning RI values in the RPA and LPA of volunteers indicate once more a nearly equal vascular resistance in both lungs.