Regional lung function in chronic pulmonary congestion with and without mitral stenosis

Relative regional ventilation and perfusion were measured with xenon-133 in 16 seated patients with pure or predominant mitral stenosis (group 1) and in 12 patients with chronic pulmonary congestion due to left-sided heart disease without mitral stenosis (group 2). The apex-base perfusion gradient was abnormally reduced and often reversed in group 1 patients. There was a significant negative correlation between perfusion gradient and mean pulmonary capillary pressure in both groups, but for a given elevation of pulmonary capillary pressure the perfusion gradient tended to be greater (i.e., less abnormal) in group 2. The regression line of perfusion gradient on pulmonary capillary pressure indicated that perfusion gradient had a value of zero (indicating reversal of the perfusion gradient) at a mean pulmonary capillary pressure of 26 mm Hg in group 2 but at only 18 mm Hg in group 1. Relative lower zone ventilation was abnormally reduced in group 1 and there was a significant negative correlation between ventilation gradient and pulmonary capillary pressure in group 1 but not group 2 patients. Comparison of the distribution of slowly inhaled small volume boluses, large volume boluses, and inspiratory capacity breaths of 133Xe suggested that the lower zone hypoventilation was due mainly to closure of peripheral airways but that selectively increased resistance and reduced compliance in the lower zones may contribute in some patients. Both ventilation and perfusion were reduced at the lung bases in group 1 patients, and between regions nonuniformity of relative ventilation/perfusion was significantly less than normal. Although ventilation distribution was relatively normal in group 2 patients, they also had significantly less regional ventilation/perfusion nonuniformity than normal subjects.