2-dimensional transthoracic echocardiogram (2D TTE) from the subcostal view showing a normal inferior vena cava (IVC) during respiration

The subcostal view in a normal subject shows the IVC. (A) Prior to inspiration, the normal diastolic IVC diameter (arrows) is less than 20 mm. (B) During inspiration, the IVC collapses to less than 50% of its original diameter.