Subcostal Four Chamber View
©Walter Rasmussen, R.D.C.S.
To obtain the subcostal four-chamber view, place the transducer just inferior to the xyphoid process, positioning the index marker to the patient’s left side and angling the transducer superiorly toward the left thorax. If the heart is not immediately visible, have the patient inhale until the image quality improves, holding their breath while each image is composed and recorded. Adjust the focal zone and TGC tabs for a sharp and evenly-lit image. If the image is faint, try lowering the transducer frequency. Adjust the dynamic range compression or reject to correct an overly foggy image. If the heart is not found in the typical location, it may be necessary to widen the search area because the image of the heart may be located at the mid-line or toward the right side of the thorax.
If all attempts at viewing the subcostal 4-chamber view fail, it could be because the heart is located too high in the chest and it can be helpful to move the transducer superiorly over the lowest left rib and when an intercostal space is found, pointing it sharply to the patient’s left in order to obtain an off-axis four-chamber view. With this view of the heart the orientation is similar to and yields much of the same information found in the subcostal four-chamber view.
For the initial subcostal four-chamber view image, adjust the depth to well beyond the heart for assessment of the surrounding tissue and the presence of pericardial and pleural effusions, which might otherwise be overlooked.
Once a general four-chamber view has been recorded, decrease the depth or zoom-in on the heart so that it fills the screen. Adjustment of the focal zone to the area of interest can help to sharpen the image. Of particular importance in this view, is the right ventricular free wall. Observe for the presence or absence of a sliding motion at the pericardium. If there is an effusion and pericardial tamponade is suspected, record an M-Mode through the right ventricular wall, the RV and LV for a high resolution assessment of right ventricular free wall motion.
When the Apical 4-Chamber view has been sub-optimal, the subcostal 4-chamber is extremely valuable as a backup view for the assessment of LV chamber size, volume and wall motion. Tilting the transducer toward the apex can often help to visualize the whole left ventricle.
After obtaining the two-dimensional portion of the Subcostal four-chamber view, narrow the image width and make individual color Doppler recordings of the tricuspid valve, the inter-atrial septum, inter-ventricular septum and mitral valve. If there is tricuspid regurgitation and other views have not yielded satisfactory CW Doppler TR recordings, attempt to record it in this view both as a backup view and because the TR jet may be better-aligned with this transducer orientation and thus reveal a higher velocity.
The subcostal four chamber view is one of the best for detecting both atrial septal defects and ventricular septal defects because the jets usually arise relatively perpindicular to the septae and parallel to the ultrasound beam. Lower the color Doppler scale to 30-40 cm/sec, and pan the transducer anteriorly and posteriorly across the interatrial septum. The exact setting of the color Doppler scale for detection of an ASD is dependent upon the amount of turbulence within the right atrium, which can become very strongly represented by the color Doppler and interfere with the assessment. The proper color Doppler scale setting is also dependent on the size of the shunt, with large shunts requiring lower setting due to the slower, less restricted blood flow. If lowering the scale causes too much of a confusing color display, improvements can be made by increasing the wall filter, decreasing the color Doppler gain and raising the scale so that it looks less cluttered. Observe the atrial septum carefully because it is more likely the case that if a small ASD is present, it will appear as a small orange/red point or flame, indicating blood moving from the left atrium to the right atrium. Seldom does color Doppler detect a small right to left shunt for which an agitated saline shunt study is more sensitive.
It is important to differentiate the suspected left to right ASD from the normal blood flow entering the right atrium via the vena cava as it too will appear red and will often course parallel to or be diverted off the inter-atrial septum, looking very similar to an ASD. An effective way to demonstrate that the SVC flow is not an ASD is to create a longer clip that starts at the ostium of the vena cava and pans to follow its course adjacent to the inter-atrial septum. Another method is to turn the transducer counter-clockwise until the subcostal short axis at the atrial septum is acquired. These methods will clear-up any confusion concerning ASD vs. caval flow.
The suspected ASD by color Doppler should be followed-up by recording CW and PW Doppler of the defect at normal (100cm/sec) and slow (25 cm/sec) speeds, for documentation of physiologic influences upon the pressure gradients.
The subcostal four-chamber view is one of the best views for assessing the functional status of an ASD closure device. Two-dimensional and three-dimensional echo images ascertain the device position and whether or not it is well-seated, while color Doppler can detect residual shunting around the closure device.