title: Changes in blood volume shunting in patients with atrial septal defects: assessment of heart function with cardiovascular magnetic resonance during dobutamine stress.
abstract: BACKGROUND
  The purpose of this study was to determine the effect of stress on left-to-right shunting in patients with atrial septal defect (ASD) and to investigate if the degree of shunting, cardiac output (CO), and right ventricular (RV) volumes are related to exercise capacity.
  
  
  METHODS
  Twenty-six patients with a secundum ASD and 16 healthy volunteers were studied with rest/stress cardiac magnetic resonance using 20 µg/kg/min dobutamine and 0.25-0.75 mg atropine to quantify CO, pulmonary to systemic flow ratio (QP/QS), and left ventricular (LV) and RV volumes. Peak oxygen uptake (VO2peak) was determined on ergospirometry.
  
  
  RESULTS
  In patients with ASD the QP/QS decreased from 2.0 ± 0.2 at rest to 1.5 ± 0.1 (P < 0.001) during dobutamine stress (n = 20) and shunt volume per heartbeat decreased from 70 ± 9 to 38 ± 9 mL (P < 0.001). However, absolute shunt volume per minute was unchanged (5.1 ± 0.8 vs. 4.5 ± 1.0 L/min, P = 0.32) explained by a higher increase in systemic CO during stress (90 ± 11%) compared with pulmonary CO (43 ± 7%, P < 0.001). In ASD patients, VO2peak correlated with aortic CO during stress (r = 0.77) and QP/QS at rest (r = -0.48) but not during stress (P = 0.09). VO2peak did not correlate with RV volumes in patients.
  
  
  CONCLUSIONS
  Pulmonary to systemic flow ratio and shunt volume per heartbeat decrease during stress in ASD patients. This may be explained by an enhanced LV diastolic function during stress and may have implications to detect disturbances in LV compliance in ASD patients. A high systemic CO during stress is a strong predictor of exercise capacity.
authors: Clinical Physiology, Department of Clinical Sciences, Lund, Lund University, Lund University Hospital, Lund, Sweden.|Pediatric Cardiology, Department of Clinical Sciences, Lund, Lund University, Lund University Hospital, Lund, Sweden.
authors: Sigurdur S
authors: SS
authors: Stephensen
authors: Clinical Physiology, Department of Clinical Sciences, Lund, Lund University, Lund University Hospital, Lund, Sweden.|Physiotherapy, Department of Health Sciences, Lund, Lund University, Lund, Sweden.
authors: Katarina
authors: K
authors: Steding-Ehrenborg
authors: Cardiology, Department of Clinical Sciences, Lund, Lund University, Lund University Hospital, Lund, Sweden.
authors: Ulf
authors: U
authors: Thilén
authors: Cardiology, Department of Clinical Sciences, Lund, Lund University, Lund University Hospital, Lund, Sweden.
authors: Johan
authors: J
authors: Holm
authors: Radiology, Department of Clinical Sciences, Lund, Lund University, Lund University Hospital, Lund, Sweden.
authors: Peter
authors: P
authors: Hochbergs
authors: Clinical Physiology, Department of Clinical Sciences, Lund, Lund University, Lund University Hospital, Lund, Sweden.
authors: Hakan
authors: H
authors: Arheden
authors: Clinical Physiology, Department of Clinical Sciences, Lund, Lund University, Lund University Hospital, Lund, Sweden.
authors: Marcus
authors: M
authors: Carlsson
mesh_terms: D000328:Adult; D000368:Aged; D006328:Cardiac Catheterization / Q000379:methods*; D002306:Cardiac Volume; D016022:Case-Control Studies; D025401:Echocardiography, Stress / Q000379:methods*; D017548:Echocardiography, Transesophageal / Q000379:methods; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D006334:Heart Function Tests; D006344:Heart Septal Defects, Atrial / Q000000981:diagnostic imaging* / Q000628:therapy; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012016:Reference Values; D018709:Statistics, Nonparametric