Sizing the Atrial Septal Defects. From Calculations Based on Geometrical Assumptions to Actual Measurements

by Luigi P. Badano, MD, PhD; Denisa Muraru, MD, PhD;
Department of cardiac, thoracic and vascular sciences, University of Padua, School of Medicine, Padua, Italy

Clinical Case

  • Female, 32 yrs old.
  • Heart murmur and dilated right ventricle at chest X-ray
  • Previous 2D TOE showed ostium secundum atrial septal defect
  • New echo study requested to size the defect in order to select the proper management strategy (i.e. percutaneous vs. surgical closure)

Two-dimensional echocardiography from apical approach. Off-axis 4-chamber view showing a relatively large ostium secundum atrial septal defect (ASD)

Two-dimensional, modified subcostal views with color Doppler (right panel) focused on the interatrail septum to showi the ASD. Sizing of the septal defect can be obtained at by measuring orthogonal diameters of the defect or calculating the QP/QS ratio. However, both methods are heavily dependend on the accuracy of multiple measurements and geometric assumptions about the shape of the defect or the shape of the left and right outflow tracts

Ao, aorta; ASD, atrial septal defect; LA, left atrium; LV, left ventricle; RVOT, right ventricular outflow tract, RA, right atrium; TV, tricuspid valve

Proper cropping of multibeat transthoracic 3D data sets acquired both from parasternal (upper panel) and apical (lower panel) approaches can show the ASD en-face (from the left side in this case) allowing the observer to visualize its actual morphology and dynamic changes throughout the cardiac cycle

Finally, the area of the defect can be planimetered on the volume rendered image, thus providing a measure of the defect size which is independent on assumptions about its shape

Example of weird morphology of ASD which can be hardly described by just measuring few diameters on two-dimensional views (Diameter 1, measured from the subcostal view, corresponds to the blue line in the middle of the ASD seen en-face from right atrial perspective). 3D echocardiography allows both the visualization of the shape of the defect and to measure its actual size by direct planimetry

Key Messages

2D/Doppler echocardiography enabled:

  • Identification of the presence of atrial septal defect

3D echocardiography allowed:

  • Identification of its position, shape and direct visualization of its dynamic changes in size during the cardiac cycle
  • Proper sizing of ASD without any assumption about its shape
  • Direct estimation of the extent of rims
  • Quantitation of the effects (volumes and function) of the volume overload on the right heart chambers


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