Pulmonary vascular resistance as assessed by bicycle stress echocardiography in patients with atrial septal defect type secundum.

BACKGROUND: Volume overload of the pulmonary circulation in patients with atrial septal defect (ASD)-type secundum causes pulmonary vascular disease over a long period of time. This study aimed at (1) evaluating pulmonary vascular resistance (PVR) and (2) investigating the relation between PVR and exercise capacity in patients with open and closed ASD. METHODS AND
RESULTS: Forty-six patients with ASD-type secundum (18 open, 28 closed) and 20 age-matched controls were enrolled. All underwent standard and symptom-limited bicycle stress echocardiography and cardiopulmonary exercise testing. PVR was calculated as the slope of a pulmonary artery systolic pressure (PAP)-flow plot or as the ratio of PAP to cardiac output (total PVR). The slope of PAP-flow was higher in patients with open (5.1±2.2 versus 3.0±0.8 mm Hg/L per min; P=0.002) and closed ASD (4.0±1.7 versus 3.0±0.8 mm Hg/L per min) compared with controls. In patients with an open ASD, total PVR did not change from rest to peak exercise. In patients with a closed ASD and controls, total PVR decreased from rest to peak exercise. However, in patients with an ASD closed later in life (≥34 years, median age at repair), the slope of PAP-flow was higher (5.1±1.4 versus 3.0±0.8 mm Hg/L per min; P<0.0001), but total PVR did not change from rest to peak exercise. Peak oxygen consumption correlated inversely with the slope of the PAP-flow plots in patients with open (P=0.013) and closed ASD (P=0.005).
CONCLUSIONS: In patients with an open ASD, the slope of PAP-flow was higher and total PVR did not change from rest to peak exercise. In patients with an ASD closed later in life, the slope of PAP-flow was higher and total PVR did not change from rest to peak exercise, indicating altered pulmonary hemodynamics in these patients.