Lung biopsy analysis can bring important contributions to the knowledge of vaso-occlusive lesions that appear in the course of congenital cardiac defects, mainly when clinical and haemodynamic data fail to reach a conclusion regarding operability.
The findings must be cautiously analysed and compared to literature data of normal lung development. The exam must include morphometric evaluation of the vessels, such as the determination of the percentage of medial thickness and the alveoli to artery ratio. Cases showing great values of medial hypertrophy should receive particular attention in the post-operative period, since they are prone to the development of vasoconstriction and haemodynamic instability. Those showing increased alveoli/artery ratio can be considered inoperable if their age is beyond the age range were numerical increase of vessels is possible.
Qualitative evaluation is also part of the exam (Heath-Edwards grade). The presence of complete occlusion of the vessel lumen (grade III) or dilated lesions (plexiform and angiomatoid lesions- grades IV and V), also define the vascular disease as irreversible. However, these kind of lesions are not homogeneously distributed through the lung, what makes the isolated qualitative analysis not representative of the status of the vascular disease.
Other parameters can be obtained during the study of lung tissue, such as recent or organised thrombotic lesions, the later occurring during the course of defects causing low pulmonary flow.