Backgrounds- Mitral stenosis (MS) causes elevation of left atrial and pulmonary venous pressures. Persistent elevation of pulmonary venous pressure causes anatomical and physiological changes in lung vasculature and tissue, and change in lung volumes thereafter. Studies showed improvement of lung function with improvement of mitral stenosis and decrease in left atrial pressure and pulmonary congestion. This study was performed to evaluate lung volumes before and after percutaneous transvenous mitral commissurotomy (PTMC), including FEV1, FVC, SVC, and their percent and FEF of 25, 50, 75, 25-75 percent and PEFR before and within 48 h after PTMC, and to evaluate correlation of each with valve area.
Methods- 26 from 51 patients with inclusion criteria stayed in the study with non-random consequential selection and the others were excluded. All of the patients had moderate to severe MS, good mitral valve morphology, echo score below 11, and absence of clot in the left atrium. Spirometery was done in all of the patients before and after PTMC and FEV₁, FVC, SVC, FEF_25%, FEF_50%, FEF_75%, FEF_25-75% FEV₁/FVC, and PEFR were measured.
Results- There were 26 patients (12 female, 14 male) with a mean age of 38.38 years old, mitral valve area was 0.88 cm² before and 1.46 cm² after PTMC (mean 0.58 cm² increase (p<.000). Mean value of lung volumes and flow changes were: SVC change= 100 ml (p<0.1), FVC=230 ml (p<0.005), FEV₁=250 ml (p<0.003), FEF_50%=0.85 (p<0.004), FEF_25% =0.98 (p<0.003), and FEF_25-75%=0.71 (p<0.01). Values for SVC, PEFR, and FEF_75% were not significant.
Conclusion- Mean value of FEV₁, FVC, FEF_50%, FEF_25% and FEF_25-75% increased significantly, but SVC, FEF_75% and PEFR had no significant improvement. This may suggest improvement of small airway function due to a decrease in lung congestion.