Right ventricular load and function during exercise in patients with open and closed atrial septal defect type secundum

Abstract
Purpose: This study aimed at evaluating (1) right ventricular (RV) mean power during exercise, (2) the contribution of flow and pressure to RV mean power, and (3) the impact of pulmonary artery pressure on RV function during exercise.
Methods: Fifty patients with atrial septal defect (ASD) type secundum (20 open, 30 closed) were enrolled. All underwent standard echocardiography, a bicycle stress echocardiography, and symptom-limited cardiopulmonary exercise testing. RV mean power was calculated as the product of RV cardiac output and mean pulmonary artery pressure (mPAP). RV function was assessed using RV fractional area change (FAC) at rest and at peak exercise.
Results: RV mean power was linearly related with oxygen uptake (VO2) in patients with open (R2¼0.88; p<0.0001) and closed ASD (R2¼0.90; p<0.0001). The increase in RV mean power was steeper in open than in closed ASD patients (p<0.0001). The change in RV cardiac output (7.13.4 vs. 5.72.4 l/min; p¼0.132) was not statistically different, but the change in mPAP (21.79.6 vs. 12.84.6 mmHg; p<0.0001) and RV mean power (0.970.56 vs. 0.530.22 W; p¼0.009) were higher in patients with an open ASD. The change in RV FAC from rest to peak exercise was related to peak mPAP in open (R¼0.589; p¼0.010) and closed (R¼0.450; p¼0.021) ASD patients.
Conclusion: RV mean power during exercise is higher in patients with an open than in patients with a closed ASD. The workload of the RV in patients with an open ASD is higher at rest due to a left-to-right shunt, at peak exercise due to an additional increase in mPAP. A higher increase in afterload may affect RV function during exercise.