7.4 Identifying Structures on Cardiac Ultrasound
Key Takeaways
- Standard transthoracic views—parasternal long and short axis, apical four-chamber, subcostal, and suprasternal notch—provide complementary planes for chamber, valve, and great vessel identification
- On parasternal long-axis view, the right ventricle is anterior, the left ventricle and left atrium are posterior, and the aortic root and mitral valve lie between them; the descending aorta appears posterior to the left atrium
- Parasternal short-axis at the papillary muscle level shows circular LV with two papillary muscles; at the base, the aortic valve is central with the tricuspid valve anterior and mitral valve posterior-left
- TEE provides superior posterior structure visualization (left atrium, LAA, pulmonary veins, interatrial septum) and is common for structural heart procedures; RCIS staff assist with probe insertion, safety checks, and image orientation
- Color Doppler confirms flow direction across valves; structure identification must precede pathology interpretation—know normal anatomy before recognizing regurgitation, stenosis, or effusion
Identifying Structures on Cardiac Ultrasound
Quick Answer: Cardiac ultrasound organizes the heart into standard views—each showing predictable anatomy. The parasternal long-axis view displays LV, LA, aortic root, and mitral valve; short-axis views slice the heart from base to apex; apical four-chamber shows all four chambers and AV valves; TEE adds posterior structures critical in the cath lab. Learn structures before pathology.
RCIS staff may assist during transesophageal echocardiography (TEE) for structural cases, support ICE imaging, or correlate bedside transthoracic echo (TTE) with cath findings. You are not required to be a registered sonographer, but CCI expects you to identify normal structures, understand probe orientation, and communicate findings accurately.
Imaging Modalities in the Cath Lab Context
| Modality | Probe Location | Best For | RCIS Role |
|---|---|---|---|
| TTE | Chest wall | Screening, effusion, gross function | Recognize views; call critical findings |
| TEE | Esophagus/stomach | LAA, septum, valves, guide wires/devices | Assist insertion, bite block, sedation monitoring |
| ICE | Intracardiac catheter | Transseptal, LAA closure, EP navigation | Console setup, documentation |
All three use the same sector (pie wedge) display: near field at top of screen (closest to transducer), far field at bottom. Orientation convention: in standard TTE/TEE, the patient's right is shown on the left side of the screen (radiologic convention).
Transthoracic Views and Structures
Parasternal Long-Axis (PLAX)
Probe placed at 3rd–4th intercostal space, left sternal border, indicator toward right shoulder.
| Structure | Appearance on PLAX | Identification Tip |
|---|---|---|
| Right ventricle (RV) | Small crescent anterior | Outflow tract may be visible |
| Left ventricle (LV) | Thick-walled chamber posterior | Septum between RV and LV |
| Left atrium (LA) | Posterior to mitral valve | Enlarges with MR, AF |
| Mitral valve | Anterior (aortic) and posterior leaflets | SAM in HOCM affects anterior leaflet |
| Aortic root / AV | Anterior to mitral valve | Three cusps in systole (best in short axis) |
| Descending aorta | Circular structure posterior to LA | Do not confuse with LA |
| Pericardial effusion | Anechoic (black) stripe around heart | Diastolic collapse → tamponade |
Parasternal Short-Axis (PSAX)
Rotate probe 90° clockwise from PLAX; indicator toward left shoulder. Sweep from base to apex.
| Level | Key Structures | Cath Lab Relevance |
|---|---|---|
| Aortic valve level | Aortic valve (Mercedes-Benz sign in systole), RVOT, tricuspid valve, pulmonic valve, interatrial septum | Pulmonic disease, septal anatomy |
| Mitral valve level | Mitral leaflets (fish-mouth in diastole) | Mitral pathology orientation |
| Papillary muscle level | Circular LV, two papillary muscles at ~5 and 7 o'clock | Global LV function assessment |
| Apex | Small circular LV cavity | Apex thrombus (anterior MI complication) |
Mercedes-Benz sign: Normal aortic valve closed sclerosis may show three commissures; bicuspid valve shows two commissures—relevant before TAVR or valvuloplasty.
Apical Four-Chamber (A4C)
Probe at cardiac apex, indicator toward left flank.
| Structure | Position on Screen |
|---|---|
| RV | Right side of screen (patient's right) |
| LV | Left side of screen (patient's left) |
| RA / LA | Superior chambers; RA on screen left, LA on screen right |
| Tricuspid valve | Between RA and RV |
| Mitral valve | Between LA and LV |
| Interventricular septum | Between RV and LV |
| Interatrial septum | Between RA and LA; probe aligned through septum |
From A4C, tilting the probe toward the aorta opens the apical five-chamber view, adding the aortic valve and LVOT—useful for aortic stenosis and LVOT obstruction assessment.
Subcostal View
Probe below the xiphoid, indicator to patient's right. Excellent for IVC size and collapsibility (volume status), pericardial effusion near diaphragm, and atrial septum when parasternal windows are poor.
| Finding | Normal | Abnormal Significance |
|---|---|---|
| IVC diameter | <2.1 cm with >50% inspiratory collapse (spontaneous breathing) | Dilated, non-collapsing IVC → elevated RA pressure |
| Effusion at subcostal | None | May be first view showing tamponade after cath |
Suprasternal Notch View
Indicator toward right shoulder from suprasternal notch. Visualizes aortic arch, brachiocephalic vessels, and descending aorta—occasionally used for coarctation or dissection screening.
Transesophageal Echocardiography (TEE) Views
TEE is standard for LAA thrombus exclusion, device guidance, and intraoperative monitoring. Probe flexion (anterior/posterior, right/left) combined with rotation generates standard views.
| TEE View | Depth / Flexion | Primary Structures |
|---|---|---|
| Mid-esophageal four-chamber (0°) | LA and LV centered | All four chambers, mitral and tricuspid valves |
| Mid-esophageal two-chamber (60–90°) | LA and LV | Anterior and inferior LV walls, mitral valve |
| Mid-esophageal long-axis (120°) | LVOT and AV | Aortic valve, mitral valve, LVOT |
| Transgastric short-axis (0°) | Advance in stomach | LV function at papillary level (monitoring) |
| Mid-esophageal AV short-axis (30–60°) | Base of heart | Aortic valve cusps, pulmonic valve |
| Mid-esophageal LAA view (0–20° with turn) | Anteflex and rotate | Left atrial appendage—critical before AF ablation/LAA closure |
LAA identification: Appears as a small pouch extending from the lateral LA wall, anterior to the pulmonary veins. Thrombus appears as echodense mass within the appendage.
Doppler Basics for Structure Confirmation
Color Doppler overlays flow on 2D images:
- Red (typically) = flow toward transducer
- Blue = flow away from transducer
| Application | What You Confirm |
|---|---|
| Mitral regurgitation | Blue or mosaic jet into LA during systole |
| Aortic regurgitation | Diastolic jet into LV outflow tract |
| Tricuspid regurgitation | Systolic jet into RA; estimates RVSP when combined with CW |
| Intracardiac shunt | Color across interatrial or interventricular septum |
Structure identification comes first: you must know which valve is which before interpreting a color jet as regurgitation versus normal physiologic flow.
Cath Lab Scenarios: Putting Anatomy Together
- Pre-TAVR TEE — Identify bicuspid vs tricuspid aortic valve, measure annulus, assess mitral regurgitation.
- LAA closure — TEE or ICE confirms appendage morphology; watch for thrombus before device deployment.
- Septal defect closure — TEE/ICE shows defect size, rims, and device position; color Doppler detects residual shunt.
- Post-PCI tamponade — Subcostal or TEE shows effusion with RA/RV diastolic collapse.
- Wire in wrong chamber — ICE/TEE confirms catheter location across septum or in LV apex.
RCIS Communication Tips
When reporting echo findings to the physician:
- Use standard view names (ME four-chamber, PSAX, etc.)
- Describe location relative to known structures ("mass in LAA," "effusion posterior to LV")
- Distinguish artifact vs pathology (reverberation from prosthetic valve vs thrombus)
- Never delay reporting acute findings: tamponade, thrombus before cardioversion, new severe regurgitation
Study Strategy
Build anatomy in layers: chambers → valves → great vessels → pathology. Draw each view on paper and label structures without looking. Pair images with cath lab procedures you perform most often—if your lab does structural heart cases, prioritize TEE/ICE atrial views; if diagnostic-heavy, prioritize TTE effusion and function assessment.
Identifying structures on cardiac ultrasound is foundational to every imaging-assisted procedure in the cath lab. Confidence in normal anatomy makes abnormal findings unmistakable.
On a standard parasternal long-axis transthoracic view, which structure appears as a small crescent-shaped chamber anterior to the left ventricle?
During TEE before left atrial appendage closure, the appendage is best visualized in which context?
A subcostal echocardiogram after an interventional procedure shows a large anechoic space surrounding the heart with right atrial diastolic collapse. The most appropriate concern is: