What depth settings should be used for each view (parasternal long‑axis, parasternal short‑axis, apical, subcostal, suprasternal notch) during a routine transthoracic echocardiogram in an adult of average body habitus, and how should they be adjusted for obese or thin patients?

Depth Settings for Transthoracic Echocardiography Views

For a standard adult transthoracic echocardiogram, depth settings should be optimized for each acoustic window to encompass the entire structure of interest while maximizing spatial resolution: parasternal views typically require 12-16 cm depth, apical views 14-18 cm, subcostal views 16-20 cm, and suprasternal notch views 10-14 cm. 1

Standard Depth Settings by Acoustic Window

Parasternal Long-Axis View

• Set depth at 12-16 cm to visualize from the anterior chest wall through the left ventricular posterior wall and descending aorta 1
• The field should encompass the aortic root, left atrium, left ventricle, and mitral valve apparatus in their entirety 2
• Adjust to include the left ventricular apex when tilted appropriately, which may require slightly deeper settings (up to 16 cm) 1

Parasternal Short-Axis Views

• Use 12-16 cm depth for standard parasternal short-axis imaging at all levels (aortic valve, mitral valve, papillary muscle, and apex) 2
• The depth should be sufficient to visualize the entire circumference of the left ventricle at each level 1
• When focusing on the aortic valve level, slightly shallower depth (10-14 cm) may optimize resolution of the valve cusps 2

Apical Views (Four-Chamber, Two-Chamber, Three-Chamber)

• Set depth at 14-18 cm to capture from the apex to the base of the heart, including the atria 2, 1
• The apical views require deeper penetration to visualize all four chambers and both atrioventricular valves completely 2
• Ensure the left atrium and right atrium are fully included in the sector, which often requires the upper range of this depth setting 1

Subcostal Views

• Use 16-20 cm depth due to the greater distance from the transducer to cardiac structures when imaging through the liver window 3
• The subcostal four-chamber view requires sufficient depth to visualize the entire heart from the inferior approach 3
• For subcostal inferior vena cava views, depth of 18-20 cm is typically necessary to assess respiratory variation 3

Suprasternal Notch Views

• Set depth at 10-14 cm to visualize the aortic arch and its branches 3
• This shallower depth is appropriate given the proximity of the aortic arch to the suprasternal notch 3
• Adjust depth to include the descending aorta when assessing for coarctation or dissection 4

Adjustments for Body Habitus

Obese Patients

• Increase depth settings by 2-4 cm across all views to account for increased distance from skin to cardiac structures 3, 1
• Parasternal views may require 16-20 cm depth in significantly obese patients 3
• Apical views often need 18-22 cm depth to adequately visualize the left atrium and mitral annulus 1
• Subcostal views may require maximum depth settings (20-24 cm) and firm downward pressure to obtain adequate windows 3
• Consider using lower frequency transducers (2.0-2.5 MHz) to improve penetration, though this reduces spatial resolution 1

Thin Patients

• Decrease depth settings by 2-4 cm to optimize spatial resolution while still encompassing structures of interest 1
• Parasternal views may only require 10-12 cm depth 1
• Apical views can often be obtained with 12-14 cm depth 1
• Subcostal views may be adequate at 14-16 cm depth 3
• Higher frequency transducers (3.5-5.0 MHz) can be used to maximize resolution in thin patients 1

Critical Optimization Principles

General Rules for Depth Adjustment

• The structure of interest should occupy approximately 75% of the screen depth to balance adequate visualization with optimal resolution 1
• Avoid excessive depth that includes unnecessary far-field structures, as this degrades frame rate and spatial resolution 3
• Before acquiring images, optimize the 2D image first, as "suboptimal 2D images result in suboptimal data sets" 3

Common Pitfalls to Avoid

• Setting depth too shallow results in truncation of cardiac structures, particularly the left atrium in apical views and the posterior wall in parasternal views 1
• Setting depth too deep unnecessarily reduces frame rate and spatial resolution without adding diagnostic information 3
• Failing to adjust depth when switching between views leads to suboptimal imaging of different cardiac structures 1
• Not accounting for patient body habitus results in either inadequate penetration or wasted resolution 3, 1

Frame Rate Considerations

• Shallower depth settings allow higher frame rates, which is particularly important for assessing rapid cardiac motion and valve function 3
• When depth must be increased for obese patients, accept the trade-off of reduced frame rate but ensure it remains above 50 frames per second for adequate temporal resolution 3

Special Circumstances

Pediatric Patients

• Significantly shallower depths are required, typically 6-10 cm for parasternal views and 8-12 cm for apical views, though this is outside the scope of standard adult echocardiography 1

Post-Surgical Patients

• Parasternal windows may be limited, requiring greater reliance on apical and subcostal views with appropriately adjusted depths 5
• Subcostal views become particularly important and may require maximum depth settings to visualize through surgical changes 3