The subcostal bicaval view
We are familiar with the subcostal 4 chamber and inferior vena cava (IVC) views. There is also something called subcostal bicaval view, where you can visualize both IVC and the superior vena cava (SVC). This view is helpful to evaluate the tip of dialysis catheter, pacemaker leads, flow pattern in SVC etc. However, its not always easy to get this view, especially in patients with central adiposity. To image the SVC, first optimize the image of IVC long axis, increase the depth, and angle the transducer toward the head, which brings SVC into view. The SVC will be at the bottom of the sector at ~5 to 6 o’clock, seen entering into the right atrium (RA). Below are some examples.
This view is also known as the snail view: shell = RA, head = IVC and tail = SVC as shown below. Spectral Doppler tracing of the SVC can be obtained in this view as the vessel is relatively parallel to ultrasound beam. Color of the vessel is red as the blood flows towards the transducer and the trace is above the baseline (otherwise similar to that of hepatic vein). It has been shown that S-wave to D-wave ratio in this view correlates well with the right atrial pressure.
On the other hand, mid-esophageal bicaval view is a standard view on transesophageal echocardiography (TEE). Imaged in this view are the left atrium, right atrium, IVC, SVC, right atrial appendage, and interatrial septum. This is a great view to evaluate for atrial septal defect/PFO as well as to evaluate structures that are not well-visualized on transthoracic echo such as eustachian valve and right atrial appendage for any abnormalities such as clots. Crista terminalis is a normal anatomic variant consisting of thick muscular bridge within the RA. Sometimes, it can mimic a mass or clot, and TEE bicaval view allows closer evaluation.