Patent Foramen Ovale Is Not Associated with Hypoxemia in Severe Chronic Obstructive Pulmonary Disease and Does Not Impair Exercise Performance

Abstract

Patent foramen ovale (PFO) may be disadvantageous in chronic obstructive pulmonary disease (COPD). It is unknown whether right-to-left shunting through PFO increases during exercise impairing exercise performance. To determine whether (1) PFO prevalence is greater in hypoxemic versus less hypoxemic patients with COPD, (2) PFO is associated with clinically relevant impairment, and (3) right-to-left shunting increases during exercise and impairs exercise performance. Patients with COPD and age-matched control subjects underwent contrast transthoracic echocardiography and transcranial Doppler to identify PFO. Patients with COPD with no shunt and patients with large PFO underwent cardiopulmonary exercise tests with contrast transcranial Doppler, esophageal, and gastric balloon catheters. PFO prevalence was similar in 50 patients with COPD and 50 healthy control subjects (46% vs. 30%; P = 0.15). Large shunts were more common in patients with COPD (26% vs. 6%; P = 0.01). In an expanded COPD cohort, PFO prevalence was similar in 31 hypoxemic (Pao2 ≤ 7.3 kPa) and 63 less hypoxemic (Pao2 > 8.0 kPa) patients with COPD (39% vs. 52%; P = 0.27). Patients with intrapulmonary shunting had lower Pao2 than both patients with PFO and those with no right-to-left shunt (7.7 vs. 8.6 vs. 9.3 kPa, respectively; P = 0.002). Shunting significantly increased during exercise in patients with COPD with PFO. Endurance time at 60% Vo2max was 574 (178) seconds for patients with PFO and 534 (279) seconds for those without (P = ns). Hypoxemic patients with COPD do not have a higher prevalence of PFO. Patients with COPD with PFO do not perform less well either on a 6-minute walk or submaximal exercise testing despite increased right-to-left shunting during exercise.