title: Quantification of left to right atrial shunts with velocity-encoded cine nuclear magnetic resonance imaging.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the ability of velocity-encoded nuclear magnetic resonance (NMR) imaging to quantify left to right intracardiac shunts in patients with an atrial septal defect.
  
  
  BACKGROUND
  Quantification of intracardiac shunts is clinically important in planning therapy.
  
  
  METHODS
  Velocity-encoded NMR imaging was used to quantify stroke flow in the aorta and in the main pulmonary artery in a group of patients who were known to have an increased pulmonary to systemic flow ratio (Qp/Qs). The velocity-encoded NMR flow data were used to calculate Qp/Qs, and these values were compared with measurements of Qp/Qs obtained with oximetric data derived from cardiac catheterization and from stroke volume measurements of the two ventricles by using volumetric data from biphasic spin echo and cine NMR images obtained at end-diastole and end-systole.
  
  
  RESULTS
  Two independent observers measured Qp/Qs by using velocity-encoded NMR imaging in 11 patients and found Qp/Qs ranging from 1.4:1 to 3.9:1. These measurements correlated well with both oximetric data (r = 0.91, SEE = 0.35) and ventricular volumetric data (r = 0.94, SEE = 0.30). Interobserver reproducibility for Qp/Qs by velocity-encoded NMR imaging was good (r = 0.97, SEE = 0.20).
  
  
  CONCLUSIONS
  Velocity-encoded NMR imaging is an accurate and reproducible method for measuring Qp/Qs in left to right shunts. Because it is completely noninvasive, it can be used to monitor shunt volume over time.
authors.affiliation: Department of Radiology, University of California Medical Center, San Francisco.
authors.forename: L D
authors.initials: LD
authors.lastname: Brenner
authors.forename: G R
authors.initials: GR
authors.lastname: Caputo
authors.forename: G
authors.initials: G
authors.lastname: Mostbeck
authors.forename: D
authors.initials: D
authors.lastname: Steiman
authors.forename: M
authors.initials: M
authors.lastname: Dulce
authors.forename: M D
authors.initials: MD
authors.lastname: Cheitlin
authors.forename: M
authors.initials: M
authors.lastname: O'Sullivan
authors.forename: C B
authors.initials: CB
authors.lastname: Higgins
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity; D006328:Cardiac Catheterization; D006325:Heart Atria / Q000473:pathology; D006344:Heart Septal Defects, Atrial / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D008875:Middle Aged; D009040:Motion Pictures / Q000295:instrumentation / Q000706:statistics & numerical data; D015588:Observer Variation; D010092:Oximetry / Q000706:statistics & numerical data; D012044:Regression Analysis