Collateral bronchopulmonary circulation after spontaneous recanalisation of pulmonary thromboemboli in the dog.

STUDY OBJECTIVE

The aim was to study the fate of enlarged bronchial arteries after resolution of experimental pulmonary embolism.

DESIGN

Embolisation of the pulmonary arteries of both lungs was performed with intravenous gelfoam. Pulmonary pressure and pulmonary arteriolar resistance were measured 1 h, 40 d and 80 d after embolisation. Pulmonary angiography and aortography were performed at the same time to evaluate the pulmonary emboli and the collateral bronchopulmonary circulation. Aortography and gross pathological and histological examination of the lungs was performed after 80 d.

EXPERIMENTAL MATERIAL

15 adult mongrel dogs of either sex were studied, weight 22-25 kg. Nine dogs were embolised and there were six controls.

MEASUREMENTS AND MAIN RESULTS

All animals survived until 80 d. There was a rise (p less than 0.001) in mean pulmonary artery pressure and arteriolar resistance 1 h after embolisation. Pulmonary artery pressures and resistances were still raised 40 d after embolisation but had returned to normal after 80 d. Pulmonary arteriography at 1 h confirmed massive thromboembolism. After 40 d antegrade pulmonary blood flow was almost completely restored, and the thromboemboli had largely disappeared. Pulmonary angiograms were completely normal after 80 d. Aortography after 40 d showed a well developed collateral bronchopulmonary circulation, most pronounced in the lower lobes, which persisted unchanged until 80 d. Aortography and gross pathological and histological examination at necropsy confirmed the presence of hypertrophic well developed bronchial arteries to both lower lobes and to a lesser extent to the middle and upper lobes, with only a few organised and recanalised thrombi in segmental arteries of both lower lobes.

CONCLUSIONS

Our data show a temporal dissociation between the resolution of pulmonary thromboemboli in the present model and the eventual regression of developed bronchopulmonary collateral vessels. The mechanism of this dissociation could not be elucidated.