Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, post mortem and imaging study. IV. Changes in the bronchial circulation demonstrated by C.T. scanning and microradiography.

This research study investigated the role of bronchial arteries in exercise-induced pulmonary haemorrhage (EIPH) in horses using advanced imaging techniques. It was concluded that bronchial vascular lesions in EIPH cases are likely the source of haemorrhage, and small airway disease could be the initial instigator for vascular growth in these lesions.

Research Methods

• The research team took lungs from four horses with histories of exercise-induced pulmonary haemorrhage (EIPH).
• To prepare the lungs for imaging, they were perfused with a mixture of red latex and contrast materials (barium or iodine) in the broncho-oesophageal artery. Meanwhile, the pulmonary supply only received blue latex.
• Computerised tomographic scans were then performed on the prepared inflated lungs from the caudal end to the hilus.
• Selected lung slices were also examined using microradiography on a device called a Faxitron.

Study Findings

• The results showed diffuse areas of increased density, with a preferential bronchial arterial supply seen on the computerised tomographic scans.
• The same areas were confirmed by carrying out microradiography.
• The imaging methods identified intensely dense, focal, and diffused plexuses of enlarged, highly branched bronchial arterial networks, centred mainly around certain small airways.

Conclusions

• The research concluded that vascular lesions in the bronchial arteries in horses suffering from EIPH are probably the origin of bleeding.
• The investigators propose that diseases affecting small airways are likely the triggering stimulus for the proliferation of bronchial vascular in the lesions.
• The authors also stated that the characteristics and structure of the new blood vessel tissue in these lesions provide the requisite conditions for haemorrhage in horses with EIPH.