Subcostal view

The subcostal window has many advantages, because there is no bone or lung tissue to obstruct the heart.

It may be the only possible window in patients with poor parasternal and/or apical views, patients who cannot be positioned on their left side, with COPD or during CPR.

• The patient lies on his back (supine position) with their legs bent at the knees to relax the abdominal wall. 
• Place the transducer under the xiphoid, slightly to the right of the sternum.
• Ask the patient to inhale, this allows the heart to move closer to the transducer, and push the probe down with a slight tilt to the patient’s right.

‍Subcostal windows are used to visualize:

• the heart – all 4 chambers
• pericardium and pericardial effusion
• RV free wall thickness
• great vessels located in the abdomen
• inferior vena cava (IVC)
• superior vena cava (SVC)
• hepatic veins (Hvns)
• abdominal aorta

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1) Subcostal Four Chamber view

• Place the transducer beneath the xiphoid, slightly to the right of the sternum.
• Push the probe down with the probe pointing towards the patient’s left shoulder.
• Index marker should point towards the left (3 o’clock).
• All four heart chambers should be visible, with the right-sided compartments at the top. The whole of LV with apex should be shown and the AV should not be seen.
• This view is important for the interatrial and interventricular septum defects.
• The diameter of the RV free wall and interventricular septum are measured.
• It’s possible to examine the RA, TV, RV, LA, MV and LV, IVS and IAS, especially if there’s poor quality on other views.
• Pericardial effusion is evaluated as the separation of pericardium and epicardium measured in centimetres.

‍Image 1 Subcostal Four Chamber view = Index marker should point towards the left (3 o’clock)‍

‍Video 1 Subcostal 4-chamber view

Image 2 Subcostal 4-chamber view anatomy

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2) Subcostal Short Axis views

• To obtain a short axis orientation of the heart, from the subcostal four chamber view rotate the probe 90° counter-clockwise
• The marker is now pointing towards the patient’s head (12 o’clock)
• Short-axis views can be acquired at different levels by moving the probe to the right (basal segments) and to the left (ventricular segments). It’s a useful alternative for patients with inadequate PSAX windows.

a) Subcostal SAX at the level of AV and RVOT

• Aortic valve, RVOT, pulmonary valve and Main Pulmonary Artery are visualized
• Structure and function of the AV may be evaluated.
• Evaluate structure and flow through the RVOT, PV and MPA if they are seen.

‍b) Subcostal SAX of Left Ventricle

• Sweep the transducer across the whole LV and apex to assess the LV function and dimensions.
• The subcostal SAX is an alternative window in individuals with difficult parasternal and apical windows for complete LV function assessment.
• The mitral valve morphology and function may be assessed in this view.

‍Video 2 Subcostal SAX (basal part of LV)

Video 3 Subcostal SAX (apical part of LV)

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3) Subcostal Inferior Vena Cava view

• From the subcostal Four Chamber view, rotate the probe 90°counterclockwise while keeping the RA in view.
• Marker is pointing towards the patient’s head (12 o’clock)
• A long-axis view of the inferior vena cava is obtained as it enters the RA.
• Hepatic veins which drain into the inferior vena cava are seen below the diaphragm.

‍Image 3  Subcostal Inferior Vena Cava view = Index marker should point towards the patient’s head (12 o’clock)

Image 4 Subcostal Inferior Vena Cava view anatomy

‍The Inferior Vena Cava diameter

• The measurement should be taken 1-2 cm from the junction of the IVC and right atrium.
• Measurement should be made perpendicular to the IVC long axis.
• The IVC diameter changes during the respiratory cycle, it generally collapses >50% of its expiration diameter if the central venous pressure is normal. 

Video 4 Variation of Inferior vena cava diameter with respiration = collapsing >50%

‍Video 5 Variation of dilated Inferior vena cava diameter with respiration = collapsing < 50%

Video 6 Variation of dilated Inferior vena cava diameter with respiration = not collapsing at all

• The IVC diameter should be measured at its maximum dimension, usually at end-expiration.
• Sufficiently long recording should be made to observe this change in diameter.
• If the collapse is not observed, the patient is instructed to perform a rapid inspiratory „sniff“ for a significant change in intrathoracic pressure. 

‍Image 5 Measurement of Inferior vena cava, not dilated IVC (15 mm)= measurement should be taken 1-2 cm from the junction of the IVC and right atrium‍

‍Image 6 Right atrial pressure may be derived from these measurements

Adapted from: Lang RM, Badano LP, Mor-Avi V. (2015). Recommendations for Cardiac Chamber Quantification by Echocardiography in Adults: An Update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging. JASE, 28(1), 1-53.

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Hepatic Veins flow pattern

• Hepatic veins are seen draining into the IVC.
• The hepatic flow is highly influenced by respiration, making it difficult to capture as the sample volume moves out of the vein lumen, and should therefore be averaged across 3 beats.
• This measurement is another tool for grading TR severity.

Image 7 PW Doppler of Hepatic Vein Flow - systolic flow reversal is seen with positive S waves present

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Abdominal aorta

• Abdominal aorta may be visualized from a modified subcostal view.
• Rotate the probe counterclockwise from the IVC view till you can see the abdominal aorta to the left of the inferior vena cava.
• Differentiation of the aorta from the vena cava can be made by appreciating the systolic pulsations of the aorta, which are usually easy to recognize.
• You can evaluate atheromatous irregularities and aneurysms of the proximal abdominal aorta or intimal flaps of aortic dissection.

Video 7 Abdominal aorta view

Image 8 Pulse Doppler imaging confirming Aorta descendens visualization

Image 9 Normal diameter of Aorta descendens = 18mm

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References

1. Lang RM, Badano LP, Mor-Avi V, Afilalo J, Armstrong A, Ernande L, Flachskampf FA, Foster E, Goldstein SA, Kuznetsova T, Lancellotti P, Muraru D, Picard MH, Rietzschel ER, Rudski L, Spencer KT, Tsang W, Voigt JU. Recommendations for cardiac chamber quantification by echocardiography in adults: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging. J Am Soc Echocardiogr. 2015 Jan;28(1):1-39.e14. doi: 10.1016/j.echo.2014.10.003. PMID: 25559473.
2. Mitchell C, Rahko PS, Blauwet LA, Canaday B, Finstuen JA, Foster MC, Horton K, Ogunyankin KO, Palma RA, Velazquez EJ. Guidelines for Performing a Comprehensive Transthoracic Echocardiographic Examination in Adults: Recommendations from the American Society of Echocardiography. J Am Soc Echocardiogr. 2019 Jan;32(1):1-64. doi: 10.1016/j.echo.2018.06.004. Epub 2018 Oct 1. PMID: 30282592.
3. Ayan R Patel, MD (2021). Transthoracic echocardiography: Normal cardiac anatomy and tomographic views. In I. Susan B Yeon, MD, JD, FACC (Ed.), UpToDate. Retrieved August 4, 2021 from www.uptodate.com
4. CAMM, A. J., LÜSCHER, T. F., & SERRUYS, P. W. (2020). The ESC textbook of cardiovascular medicine. Oxford, Oxford University Press
5. Otto, C. M. (2018). Textbook of clinical echocardiography. 
6. University Health Network. (2018). TTE Standard Views: Virtual Transthoracic Echocardiography, TTE, PIE, Toronto General Hospital Department of Anesthesia, FOCUS, FATE, Standard Views. Virtual Transthoracic Echocardiography. http://pie.med.utoronto.ca/tte/TTE_content/standardviews.html#introduction
7. Judith Buckland, MBA, RDCS, FASE, C. (2019, November 13). How to Estimate Right Atrial Pressure (RAP). Cardioserv. https://www.cardioserv.net/how-to-estimate-right-atrial-pressure/