Left ventricular overload caused by collateral pulmonary circulation in chronic pneumopathies-myth or reality?

The collateral pulmonary blood flow was measured by the dye dilution method in four patients with chronic obstructive pulmonary disease, in 16 patients with diffuse pulmonary fibrosis, in 15 patients with pulmonary embolism, and in three patients with primary pulmonary hypertension. The authors found that collateral pulmonary circulation was small in the first two groups (0.3 % and 1.7% of the pulmonary blood flow, respectively), absent in primary pulmonary hypertension, and high (14.0% of pulmonary flow) in pulmonary embolism. The magnitude of the bronchopulmonary collateral circulation did not correlate with degree of precapillary pulmonary hypertension, left atrial pressure and left ventricular enddiastolic pressure. It seems that the bronchopulmonary collateral flow does not produce diastolic left ventricular overload in chronic pneumopathies.