A complete Transthoracic Echocardiogram (TTE) relies on four primary acoustic windows to visualize the heart’s anatomy and hemodynamics.
1. Parasternal Long-Axis View (PLAX)
The PLAX view is typically the starting point for a TTE exam, providing a longitudinal slice of the left side of the heart.
- Probe Placement: 3rd or 4th intercostal space, just to the left of the sternum.
- Index Marker: Pointed toward the patient’s right shoulder.
Key Structures Evaluated:
- Left Atrium (LA) and Left Ventricle (LV)
- Right Ventricular Outflow Tract (RVOT)
- Mitral Valve (MV) and Aortic Valve (AV)
- Aortic Root and descending aorta (highly useful for differentiating between pericardial and pleural effusions)
2. Parasternal Short-Axis View (PSAX)
By rotating the probe 90 degrees clockwise from the PLAX position, you obtain a cross-sectional (“sausage slice”) view of the heart.
- Probe Placement: Same acoustic window as PLAX.
- Index Marker: Pointed toward the patient’s left shoulder.
Key Levels Evaluated:
- Aortic Valve Level: Visualizes the “Mercedes-Benz sign” of the aortic cusps, along with the LA, Right Atrium (RA), RVOT, and pulmonary valve.
- Mitral Valve Level: Evaluates anterior and posterior mitral leaflets.
- Mid-Papillary Level: The ideal level for assessing global and regional Left Ventricular wall motion.
- Apex Level: Assesses apical wall motion and checks for apical thrombi.
3. Apical 4-Chamber View (A4C)
This window provides a comprehensive look at all four chambers simultaneously, making it the primary view for assessing chamber size comparisons and longitudinal function.
- Probe Placement: At the Point of Maximal Impulse (PMI), usually the 5th intercostal space at the mid-clavicular line.
- Index Marker: Pointed toward the patient’s left side (3 o’clock position).
Key Structures Evaluated:
- Left and Right Ventricles (the RV should normally be roughly two-thirds the size of the LV).
- Left and Right Atria.
- Mitral and Tricuspid Valves (noting the normal slight apical displacement of the tricuspid valve relative to the mitral valve).
- Interventricular and Interatrial Septa.
4. Subcostal (Subxiphoid) View
This window uses the liver as an acoustic medium to view the heart from below. It is particularly useful in patients with COPD, hyperinflation, or otherwise poor chest wall windows.
- Probe Placement: Just below the xiphoid process, pressing downward and angling slightly upward toward the left shoulder.
- Index Marker: Pointed toward the patient’s left side (for the 4-chamber orientation).
Key Structures Evaluated:
- All four chambers (the perpendicular angle to the interatrial septum makes this the best view for detecting Atrial Septal Defects or Patent Foramen Ovale).
- Pericardial Space: The optimal view for rapidly identifying pericardial effusions and signs of tamponade physiology (e.g., diastolic RV collapse).
- Inferior Vena Cava (IVC): Rotating the index marker superiorly allows a longitudinal assessment of the IVC diameter and its respiratory variation, which is used to estimate Right Atrial pressure.
Once you have established the basic windows, a complete study relies on advanced and specific views to interrogate distinct myocardial territories, valvar hemodynamics, and extracardiac structures.
Here are the key special views needed for a comprehensive structural and functional assessment.
1. The Apical Expansions (A5C, A2C, A3C)
From the Apical 4-Chamber (A4C) position at the Point of Maximal Impulse (PMI), subtle probe manipulations unlock the rest of the left ventricle and the left ventricular outflow tract (LVOT).
Apical 5-Chamber View (A5C)
- How to get it: From the A4C, tilt the tail of the probe slightly downward (angling the beam anteriorly).
- What it adds: The “5th chamber” is the aortic root and AV.
- Clinical Utility: This is the primary window for using Continuous Wave (CW) Doppler to measure aortic valve gradients in suspected aortic stenosis, as the ultrasound beam is highly parallel to the LVOT flow.
Apical 2-Chamber View (A2C)
- How to get it: From the A4C, rotate the probe counterclockwise about 60 degrees (index marker pointing toward the patient’s anterior shoulder).
- What it adds: Isolates the Left Atrium (LA) and Left Ventricle (LV) without the right-sided structures.
- Clinical Utility: Specifically evaluates the anterior wall (LAD territory) and the inferior wall (RCA territory) of the left ventricle. Essential for calculating biplane ejection fraction via the modified Simpson’s rule.
Apical 3-Chamber View (A3C / Apical Long-Axis)
- How to get it: From the A2C, rotate counterclockwise another 60 degrees (index marker pointing roughly toward the right shoulder).
- What it adds: Looks remarkably similar to the PLAX view, but interrogated from the apex rather than the parasternal window.
- Clinical Utility: Evaluates the anteroseptal and inferolateral walls of the LV. It is also excellent for assessing mitral and aortic valve regurgitation with color Doppler.
2. Right Ventricular Inflow Tract (RVIT) View
While the standard parasternal views show slices of the right heart, the RVIT gives a dedicated look at the right-sided filling structures.
- How to get it: Return to the PLAX position. Angle the probe inferomedially (tilting the tail toward the patient’s left shoulder) to swing the beam into the right heart.
- Structures Evaluated: Right Atrium (RA), Right Ventricle (RV), and the anterior and posterior leaflets of the Tricuspid Valve. (Note: the septal leaflet is usually seen in the Apical 4-Chamber).
- Clinical Utility: This is often the best view to align the CW Doppler beam with a tricuspid regurgitation (TR) jet to accurately estimate Right Ventricular Systolic Pressure (RVSP) and assess for pulmonary hypertension.
3. Suprasternal Notch (SSN) View
This view moves away from the precordium entirely to interrogate the great vessels.
- How to get it: The patient’s neck is extended (often with a pillow under the shoulders). The probe is placed in the jugular notch, with the index marker pointing toward the patient’s left jaw/ear.
- Structures Evaluated: The ascending aorta, aortic arch, descending thoracic aorta, and the origins of the great vessels (brachiocephalic, left common carotid, and left subclavian arteries). The right pulmonary artery is often seen in cross-section beneath the arch.
- Clinical Utility: Crucial for identifying aortic pathologies such as coarctation of the aorta, aortic dissection flaps, or a Patent Ductus Arteriosus (PDA).