{"id":79246,"date":"2025-06-12T13:29:52","date_gmt":"2025-06-12T13:29:52","guid":{"rendered":""},"modified":"2026-02-27T16:56:02","modified_gmt":"2026-02-27T16:56:02","slug":"news-measuring-the-left-atrium-what-where-when-and-why","status":"publish","type":"post","link":"https:\/\/www.imv-imaging.com\/en\/2025\/06\/news-measuring-the-left-atrium-what-where-when-and-why\/","title":{"rendered":"Measuring the left atrium: what, where, when, and why?\u00a0\u00a0"},"content":{"rendered":"\n

<\/path><\/svg><\/span><\/span>Estimated reading time: <\/span>10<\/span> minutes<\/span><\/p>\n\n\n\n

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Why measure the left atrium?  <\/h2>\n\n\n\n

Whether it forms part of an out-of-hours TPOCUS<\/a> (Thoracic Point-Of-Care Ultrasound) exam in the prep room, or a full echocardiogram performed by a diplomat cardiologist, the left atrial size is an essential structure to quantify in some form.  <\/p>\n\n\n\n

Generally, this is because without left atrial enlargement, congestive heart failure is very unlikely (with rare exceptions). This leads the practitioner to a simple yes\/no question as part of the workup for cases such as acutely dyspnoeic cats, or coughing dogs; is this a cardiac issue or something else?  <\/p>\n\n\n\n

So where to start?  <\/h3>\n\n\n\n
Part 1: The Long Axis <\/h5>\n\n\n\n

First things first; a lot of information can be gained from a right-sided, parasternal, long axis, four chamber view of the heart (RPLA4Ch view). This is known unofficially as the heart homepage<\/em> view, and is a great starting point, since it allows both subjective and objective assessment of left atrial size. Don\u2019t underestimate how important the subjective assessment of the heart can be; diagnoses can be made based on this analysis alone.  <\/p>\n\n\n\n

In this view, we can see the four main chambers of the heart (labelled in Image 1, below). <\/p>\n\n\n\n

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Image 1; the RPLA4Ch view. <\/strong>RV; right ventricle. RA; right atrium. IAS; inter-atrial septum. LV; left ventricle. MV; mitral valve. LA ; left atrium.<\/em><\/p>\n\n\n\n

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Subjective assessment at the RPLA4Ch view:  <\/strong><\/p>\n\n\n\n

The left atrium should be roughly square, or broadly hexagonal in shape<\/strong>. It should not bow into the right atrium, and the inter-atrial septum should appear horizontal, rather than displaced towards the right atrium (Image 2, below)<\/p>\n\n\n\n

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Image 2; subjective assessment of the left atrial shape. <\/strong>In the image on the left, the left atrium forms a roughly square shape. In the image on the right, from the same dog at a later systolic stage, the refilling left atrium forms a roughly hexagonal shape.<\/em><\/p>\n\n\n\n

The length of the left atrium should be approximately equal to 1\/3 of the total length of the cardiac silhouette<\/strong>, with the left ventricle taking up the other 2\/3 (Image 3, below) <\/p>\n\n\n\n

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Image 3; the rule of thirds. <\/strong>In this image, the left atrium (on the right of the image) forms 1\/3 of the length of the cardiac silhouette at the end of diastole.<\/em><\/p>\n\n\n\n

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The height of the left atrium should approximately equal the height of the left ventricle, when the ventricle is in diastole (Image 4, below) <\/p>\n\n\n\n

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Image 4; left atrial height. <\/strong>The height of the left atrium and left ventricle in mid diastole are equal. The illustrative purple arrows are the same height.<\/em><\/p>\n\n\n\n

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Objective assessment at the RPLA4Ch view:  <\/strong><\/p>\n\n\n\n

a) Cats: Left Atrium in Long Axis (LAD)   <\/p>\n\n\n\n

The Left Atrium in Long Axis (otherwise known as Left Atrial Dimension, or LAD) is commonly used as a standalone indication of left atrial enlargement in cats. Long axis measurements in general are often easier to perform than short axis measurements in these patients. This is in part due to the prominence of the papillary muscles when performing M-mode studies, which are made in short axis, as well as the higher heart rate and smaller intercostal spaces creating additional challenges with achieving a short axis Left atrium: Aortic ratio (LA:Ao). These factors can all contribute to measurement errors.    <\/p>\n\n\n\n

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  1. The measurement is taken at end systole;  <\/strong><\/li>\n<\/ol>\n\n\n\n