Chapter 5 — The Standard Transthoracic Examination in the ICU

📚 Guideline basis

ASE 2019 comprehensive TTE examination in adults (JASE 2019;32:1–64); ASE 2015 chamber quantification (Lang et al., JASE 2015;28:1–39); ASE 2025 right heart guideline for RV-focused views; ACCP/SRLF basic CCE view set.

The five acoustic windows

The ICU inversion: in ambulatory echocardiography the parasternal window is acquired first and is usually best. In the mechanically ventilated patient, hyperinflation displaces the heart, and the subcostal window is frequently the only reliable one. Train the subcostal window deliberately; it is the workhorse of critical care echocardiography.

Core view set and what each answers

Parasternal long axis (PLAX)

Structures: RV outflow tract anteriorly, interventricular septum, LV cavity, posterior wall, mitral valve, aortic valve, LVOT, aortic root, descending thoracic aorta in cross-section posteriorly, coronary sinus.

Measurements: LV internal dimensions at end-diastole and end-systole (perpendicular to the long axis, at or just distal to the mitral leaflet tips), septal and posterior wall thickness, LVOT diameter, aortic root and sinotubular junction, left atrial anteroposterior dimension, E-point septal separation.

Errors: oblique cuts foreshorten the LV and produce spuriously small dimensions; the "true" PLAX shows the aortic and mitral valves in the same plane with the LV apex not visible. If you can see the apex, the plane is wrong.

Parasternal short axis (PSAX)

Sweep from base to apex through four levels: aortic valve level (three cusps, tricuspid vs bicuspid, interatrial septum, tricuspid and pulmonic valves, RVOT — the level for RVOT VTI and pulmonic assessment); mitral valve level ("fish-mouth", planimetry of mitral orifice); papillary muscle level (the standard level for septal motion, D-shaping, and regional wall motion in all three coronary territories); apical level.

The papillary muscle level is the single most informative image for RV pressure/volume overload: septal flattening producing a D-shaped LV, with timing that distinguishes the mechanism (Chapter 9).

Apical four-chamber (A4C)

Structures: all four chambers, mitral and tricuspid valves, interatrial and interventricular septa.

Measurements: biplane Simpson's LV volumes and EF (with A2C), LV and RV areas, RV basal and mid diameters, TAPSE (M-mode through the lateral tricuspid annulus in the RV-focused view), tricuspid annular s′, mitral inflow E/A, mitral annular e′, LA volumes, TR jet by CW.

RV-focused A4C is a distinct view, not the standard A4C. Rotate and tilt to maximise RV free wall without foreshortening; RV linear dimensions and TAPSE must be measured from it. Measuring RV basal diameter from a standard A4C over- or under-estimates depending on the rotation, and is the commonest source of spurious "RV dilatation".

Apical five-chamber (A5C) and three-chamber (A3C / apical long axis)

Both open the LVOT to Doppler. The A5C is obtained by anterior tilt from A4C. Either is acceptable for LVOT VTI; the A3C often gives better alignment. Report which view was used so serial studies are comparable.

Apical two-chamber (A2C)

Inferior and anterior LV walls; required for biplane Simpson's. Obtained by ~60° counterclockwise rotation from A4C, with the RV excluded from the image — if any RV is visible, the plane is wrong.

Subcostal views

Four-chamber (probe flat, aimed at the left shoulder): pericardial effusion detection is most sensitive here (dependent fluid, no lung interposition), RV free wall thickness measurement is specified from this view (normal < 5 mm per ASE 2025), and interatrial septal motion is best seen.

Subcostal IVC (rotate to sagittal): IVC diameter measured 1–2 cm from the cavo-atrial junction, or just distal to the hepatic vein confluence. Hepatic vein Doppler from the same window (Chapters 12, 13).

Suprasternal notch

Aortic arch; PW/CW in the proximal descending aorta for holodiastolic flow reversal (a specific sign of severe aortic regurgitation, Chapter 19) and for coarctation.

A staged ICU protocol

The comprehensive ASE examination requires 60–90 views and is not the ICU workflow. Stage the examination by question:

Stage 1 — Focused (2–4 min), answers: is there a mechanical cause of shock or arrest?

Subcostal 4C, subcostal IVC, PLAX, A4C. Assesses: effusion/tamponade, RV:LV ratio, gross LV function, gross volume state.

Stage 2 — Haemodynamic (5–10 min), answers: what is the flow state and what will fluid do?

Adds: LVOT diameter (PLAX zoomed), LVOT VTI (A5C/A3C), TR jet, mitral inflow E/A, mitral annular e′, IVC with respiratory variation, hepatic vein flow, respiratory variation of LVOT VTI.

Stage 3 — Comprehensive (20–30 min), answers: what is the structural diagnosis?

Full ASE view set: all valves with colour and spectral Doppler, biplane volumes, regional wall motion in all segments, right parasternal AS interrogation, suprasternal aorta, shunt assessment.

Escalate to TEE (Chapter 25) when Stage 2 cannot be completed because of window failure, or when the question is one TTE answers poorly: prosthetic mitral valve, endocarditis, aortic dissection, LA appendage thrombus, post-sternotomy tamponade, ECMO cannula position.

Timing, ECG and respiration

• An ECG trace is mandatory for any measurement requiring timing (end-diastole = onset of QRS or the frame before mitral valve closure; end-systole = the frame before mitral valve opening, or aortic valve closure).
• In ventilated patients, note when in the respiratory cycle an image was acquired. End-expiration is conventional. Serial studies compared across different respiratory phases will differ by an amount that can exceed the intervention effect.
• Record heart rate with every Doppler measurement. VTI falls with tachycardia while cardiac output may rise; reporting VTI without heart rate is uninterpretable.

ICU-specific limitations

🛑 Critical pitfall: Apical foreshortening. A foreshortened apical view shrinks LV length, reduces calculated volumes, and inflates ejection fraction — often by 5–10 EF points. Verify by confirming the LV is maximally long and the apex does not move toward the transducer in systole. Where possible, use the ultrasound enhancing agent rather than accepting a poor border.

🛑 Critical pitfall: Diagnosing "RV dilatation" from a non-RV-focused apical view. The RV:LV ratio varies substantially with rotation. Confirm in more than one view — RV-focused A4C plus PSAX septal morphology plus subcostal — before acting on it.

• 💡 Clinical pearl: In the ventilated patient, spend the first 30 seconds finding the best window rather than the first view. The subcostal window will often deliver in seconds what five minutes of parasternal attempts will not.
• 💡 Clinical pearl: Store an unmeasured loop of every view you obtain, even the poor ones. The over-read and the follow-up study depend on them, and a repeat scan four hours later against a stored baseline is worth more than any absolute measurement.
• 💡 Clinical pearl: The right parasternal window is omitted in most ICU studies and is where the highest aortic velocity is found in a meaningful minority of patients. Omitting it under-grades aortic stenosis.

References

1. Mitchell C, Rahko PS, Blauwet LA, et al. Guidelines for performing a comprehensive transthoracic echocardiographic examination in adults. J Am Soc Echocardiogr 2019;32:1–64.
2. Lang RM, Badano LP, Mor-Avi V, et al. Recommendations for cardiac chamber quantification by echocardiography in adults: an update from the ASE and the EACVI. J Am Soc Echocardiogr 2015;28:1–39.
3. American Society of Echocardiography. Guidelines for the echocardiographic assessment of the right heart in adults and special considerations in pulmonary hypertension. J Am Soc Echocardiogr 2025.