Pulmonary shunts

Complex cyanotic congenital heart disease (e.g., single ventricle states) / Surgically constructed systemic pulmonary shunts or conduits... 

Treatment planning requires a multi-disciplinary team with clear leadership and accountability to ensure that the screening, diagnostic and treatment procedures are conducted in a seamless fashion. The essential steps include (1) calculation of target liver mass to be infused and tumor burden (2) visceral angiography to map out tumor-perfusing vessels and embolize collaterals (3) assessment of pulmonary shunt (4) determination of the optimal therapeutic dose (5) room preparation (6) radiation monitoring and safety procedures (6) calculation of residual activity and efficiency of delivery. 

Fig. 16.13. Selective catheterization of thyrocervical trunk (arrow), demonstrating pathologic enhancement of left apical region and pulmonary shunting (arrowhead)...

This estimation will be supported by the results of the technetium-99m macroaggregated albumin scanning ( Tc MAA scan) necessary to assess potential pulmonary shunting (see below). 

Depending on the type (Table 2.7.2) of microsphere, a pulmonary shunt fraction of 10%-20% can be tolerated. Furthermore, one should be aware that evaluation of the shunt fraction can be influenced by several factors ... 

Another severe complication may be radiation-induced pneumonitis due to aberrant pulmonary particle implantation via hepato-pulmonary shunts. Radiation pneumonitis may be suspected if nonproductive cough together with a variably dense infiltration on a chest radiograph arise a few days after microparticle treatment. There is no treatment for pneumonitis - vfliich can take a fatal course - to justify a thorough pre-interventional work-up in order to exclude or to identify potential hepato-pulmonary shunts (Dancey et al. 2000). 

Hung JC et al. (2000) Evaluation of macroaggregated albumin particle sizes for use in pulmonary shunt studies. J Am Pharm Assoc 40 46-51... 

Radiation pneumonitis is a concern with hepatic-directed radiation treatment. Previous preclinical and clinical studies with microspheres demonstrated that up to 30 Gy to the lungs could be tolerated with a single injection, and up to 50 Gy for multiple injections [13], For this reason, patients with Tc-MAA evidence of potential pulmonary shunting resulting in lung doses greater than 30 Gy should not be treated. 

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