Background: A patent foramen ovale (PFO) is not widely recognized as a factor contributing to hypoxemia in patients with chronic obstructive pulmonary disease (COPD). We therefore sought to clarify the prevalence and clinical significance of a PFO in patients with COPD, and to analyze the factors related to its occurrence.
Methods: This study included 52 consecutive stable patients with COPD and 50 healthy controls. The demographic and clinical features of the study group were noted. To test for a PFO, standard and contrast transthoracic echocardiographic examinations were performed while resting and during the Valsalva maneuver (VM). Patients performed 6-min walking tests (6 MWT), and the distances traveled were measured.
Results: During VM, we detected a PFO in 23 COPD patients and 10 healthy controls (P<0.01). A PFO was detected while resting in 11 COPD patients, but in none of the controls (P=0.001). Comparison of multiple parameters between COPD patients with and without a PFO during VM did not reveal any clinically significant differences. When we compared COPD patients with and without a PFO during resting, however, we found that the former had longer durations of disease, lower PaO2 and SaO2, higher dyspnea scores, shorter distances walked during 6 MWT and higher desaturation rates (P<0.05). Logistic regression analysis showed that longer duration of disease, lower SaO2 and higher systolic pulmonary artery pressure were independent predictors of the occurrence of a PFO in resting COPD patients.
Conclusions: The prevalence of a PFO is higher in patients with COPD than in healthy individuals. The presence of a PFO while resting may contribute significantly to the deterioration of arterial oxygenation and performance status. These findings indicate that a PFO may be a principle cause of hypoxemia in patients with COPD.