Subcostal & Suprasternal-Notch Views

The Subcostal Window

The subcostal window is acquired with the patient supine and the knees flexed, which relaxes the abdominal wall. The transducer is placed just below the xiphoid process and angled to use the liver as an acoustic window, directing the beam superiorly and slightly leftward toward the heart.

Subcostal Four-Chamber View

With the index marker toward the patient's left, the subcostal four-chamber view shows all four chambers in an orientation similar to A4C, but the ultrasound beam strikes the interatrial septum at a near-perpendicular angle. Because a perpendicular beam minimizes septal dropout artifact, this is the preferred view for assessing the integrity of the interatrial septum — for suspected atrial septal defect, patent foramen ovale, or septal aneurysm. The subcostal window is also frequently the best or only obtainable window in patients who are mechanically ventilated, hyperinflated (e.g., COPD), obese, or post-sternotomy, which makes it the primary window in point-of-care/focused cardiac ultrasound (FoCUS) and the first view checked for pericardial effusion in emergent settings.

Subcostal IVC (Long-Axis) View

Rotating the transducer roughly 90 degrees counterclockwise from the subcostal four-chamber position (marker toward the patient's head) brings the imaging plane into a sagittal orientation, showing the inferior vena cava (IVC) as it enters the right atrium along with the hepatic vein confluence. IVC diameter and its collapse with a sniff or deep inspiration are used to estimate right atrial pressure (RAP):

Subcostal Short-Axis View

Rotating a further 90 degrees from the subcostal four-chamber view produces a short-axis image analogous to the parasternal short-axis views, useful as a backup when the parasternal window is technically difficult.

The Suprasternal Notch (SSN) Window

The suprasternal window is obtained with the patient supine, neck extended, chin elevated, and head turned to the left. The transducer is placed directly in the suprasternal (jugular) notch and angled inferiorly into the mediastinum.

Suprasternal Long-Axis (Aortic Arch) View

With the index marker toward the patient's left ear (roughly the 3-o'clock position), this view images the aorta in a coronal, long-axis plane — the classic 'candy cane' or 'hockey stick' appearance — showing the ascending aorta, the transverse aortic arch, and the proximal descending thoracic aorta. Three arch branch vessels are typically identified peeling off the superior arch: the innominate (brachiocephalic) artery, the left common carotid artery, and the left subclavian artery. Below the arch, the right pulmonary artery is often seen in cross-section. This view is essential for evaluating aortic arch pathology — coarctation of the aorta (continuous-wave Doppler across the coarctation site demonstrates a diastolic 'runoff' tail and an elevated gradient), aortic dissection (an intimal flap), and arch atheroma — and provides an additional acoustic window onto the descending thoracic aorta when the parasternal descending aorta view is inadequate.

Suprasternal Short-Axis View

Rotating the transducer 90 degrees from the long-axis position shows the right pulmonary artery in its long axis passing beneath the aortic arch, along with the superior vena cava — useful for assessing anomalous pulmonary venous or systemic venous connections in congenital disease.

Subcostal Views in Emergency and Point-of-Care Settings

Because it does not require the left lateral decubitus position, the subcostal four-chamber view is one of the standard views in the extended FAST (eFAST) trauma protocol and is frequently the fastest view to obtain in a supine, unstable, or recently resuscitated patient. Its near-perpendicular incidence on the pericardium also makes it a reliable window for detecting pericardial effusion and evaluating tamponade physiology — including respirophasic ventricular septal shift and IVC plethora — when the parasternal and apical windows are not accessible. The subcostal IVC view can also be recorded in M-mode, placing the cursor perpendicular to the IVC roughly 1-2 cm from the cavoatrial junction to trace the diameter change across the respiratory cycle and calculate a collapsibility index alongside the two-dimensional diameter assessment.

Suprasternal Notch: Additional Clinical Value

Beyond arch anatomy, the suprasternal long-axis view provides continuous-wave Doppler access to descending aortic flow that is otherwise difficult to interrogate from the chest wall, making it useful for grading a coarctation gradient and for screening the arch and proximal descending aorta for atheroma, a source of embolic stroke. Because head and neck positioning affects image quality substantially, the suprasternal view is often deferred to the end of the study and re-attempted with head repositioning if the arch is not initially well seen.

Putting the Windows Together

Between them, the subcostal and suprasternal windows complete structures that the parasternal and apical windows cannot reliably assess: the interatrial septum, the IVC/RAP estimate, and the aortic arch. Because they require different patient positioning (supine rather than left lateral decubitus) and are less dependent on rib-space acoustic access, they also serve as reliable fallback windows when body habitus, lung disease, or mechanical ventilation degrades parasternal and apical image quality.