Smoking is associated with depletion of endothelial progenitor cells (EPCs) and may subsequently contribute to the development of vascular dysfunction. The aim of this study was to investigate the relation between circulating EPCs and pulmonary artery systolic pressure (PASP) as determined by flow cytometry and echocardiography in 174 patients (mean age 69 ± 9 years, 95 smokers) with established coronary artery disease. Smokers had significantly lower circulating log CD34/KDR(+) (0.86 ± 0.03 vs 0.96 ± 0.03 × 10⁻³/ml, p = 0.032) and log CD133/KDR(+) (0.68 ± 0.03 vs 0.82 ± 0.03 × 10⁻³/ml, p = 0.002) EPCs and a higher prevalence of elevated PASP >30 mm Hg (52% vs 30%, p = 0.001) than nonsmokers. Smokers with elevated PASP also had significantly lower circulating log CD34/KDR(+) (0.74 ± 0.04 vs 0.88 ± 0.06 × 10⁻³/ml, p <0.001) and log CD133/KDR(+) (0.61 ± 0.04 vs 0.78 ± 0.05 × 10⁻³/ml, p <0.001) EPCs, higher pulmonary vascular resistance, and larger right ventricular dimensions with impaired function (all p values <0.05). Log CD34/KDR(+) and log CD133/KDR(+) EPC counts were significantly and negatively correlated with PASP (r = -0.30, p <0.001, and r = -0.34, p <0.001, respectively) and pulmonary vascular resistance (r = -0.29, p = 0.002, and r = -0.18, p = 0.013, respectively). In conclusion, this study demonstrated that in patients with coronary artery disease, smoking was associated with a reduced number of EPCs and elevated PASP. This suggests that in smokers, depletion of circulating EPCs might be linked to the occurrence of pulmonary vascular dysfunction.
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