In this VETgirl online veterinary continuing education blog, Dr. Christopher Kennedy, DACVECC, DECVECC discusses Focused Cardiac Ultrasound (FCU) Examination in the dog and cat. When used correctly, FCU can be helful in formulating a problem list, making a diagnosis and managing an acutely or critically ill patient. Read on to learn about the core FCU examination. In future blog posts, we will expand on FCU and its use (and abuse!) in dogs and cats.
By Dr. Christopher Kennedy, DACVECC, DECVECC
Focused Cardiac Ultrasound (FCU) Examination
What is Focused Cardiac Ultrasound?
Focused Cardiac Ultrasound (FCU) is ultrasound of the heart and major vessels, and can be very helpful in identifying the pericardium, pericardial sac and the right and left heart. There is no formal definition: we use it as cardiac ultrasound performed in non-cardiology settings to answer specific questions about cardiac structure and sometimes function. It is not a complete echocardiogram; it typically involves only 2D and M-mode cardiac imaging; Doppler echocardiography is part of critical care echocardiography (CCE), which is more advanced.
What are the goals of FCU?
1. To visualize the pericardium/pericardial space, the right and the left heart from several angles.
2. To identify overt abnormalities.
3. To integrate this information with history and clinical examination.
FCU is not the same as a formal echocardiogram performed by a cardiologist. Like other point of care ultrasound categories, it is designed to be quickly implemented and answer targeted questions. As such, we are often looking for obvious, as opposed to subtle, abnormalities. A clever FCU practitioner uses it to complement their clinical examination and not as their only diagnostic tool.
We teach FCU exclusively from the right side. It can be performed in lateral or sternal recumbency or standing. Cardiologists use phased-array probes: Microconvex (curvilinear) probes can be used too.
1. Parasternal long-axis 4 chamber view (PLAX4)
This view is your landing view: always start your examination here. It captures most of the heart – four chambers, right and left, and the pericardium – in one view. It can provide bountiful information, so work on obtaining this view first. (See Video 1).
VIDEO 1: PLAX4
2. Parasternal short-axis view at the level of the papillary muscles (PSAX-pap)
Often called the “mushroom view,” this view is useful; however, it should not be obtained first, as it does not provide the same overview of the heart as the PLAX4, which means you might hyperfocus and miss something important! (See Video 2).
VIDEO 2: PSAX-pap
3. Parasternal short-axis view at the level of the heart base (PSAX-base)
This is the “LA:Ao view.” We prefer other measures to the LA:Ao – which we will discuss in future posts! – and this view considers more than just the left atrium, so we don’t call it that.
4. Subxiphoid view (SX), which has two variations (SX-CVC and SX-heart)
Sometimes called “transdiaphragmatic,” this view is an icing-on-the cake view for any FCU practitioner who wants to up their FCU’ing skills to become the crème de la crème. (See Video 3)
VIDEO 3: SX-CVC
VIDEO 4: SX-heart. This video starts of visualizing the right heart and moves to the left heart.
Anatomy of the image
The probe emits and receives ultrasounds. It processes the ultrasounds it receives and an image is displayed on the screen. This is the “sector.” (See Figure 6).
An orientation marker is visible on the probe and the screen (See Figure 7).
Sometimes structures in the sector can be muddled by the processing of the ultrasounds. Resolution is the ability to differentiate between two points in proximity. (See Figure 8)
– Lateral resolution: the ability to differentiate between two things lying linearly side-by-side at the same depth.
– Axial resolution: the ability to differentiate between two things along the same linear path as the ultrasound beam.
In each view, there are three questions to ask yourself and in this specific order:
1. Is there pericardial effusion?
2. How is the right heart?
3. How is the left heart?
This is what we call the “systematic approach to FCU.”
These three questions are an excellent starting place. As we journey through the world of FCU, these questions will become more focused and, when integrated into clinical context, will become more meaningful.
Isn’t it more logical to start with the left heart and then move on to the right?
I am glad you asked! In short, no.
Here is an example.
VIDEO 5: Focusing on the left heart, the left ventricle is underloaded. This might prompt you to consider hypovolemia and fluid administration.
VIDEO 6: When we consider first the right heart, it is clearly enlarged. This explains the underfilling of the left heart and identifies this patient as probably fluid intolerant – intravenous fluids will likely worsen this patient. Cases like this should be discussed with a cardiologist.
The systematic approach to FCU is more developed than a quick peek at the heart. It involves several views, three general questions (see above) and encourages appraisal of all four heart chambers, their walls, the valves and the pericardium.
Remember: we are not cardiologists, so we are not performing a formal echocardiogram. Goal #3 of FCU is to integrate this information into our clinical examination. What clinical questions were you asking? Sometimes these questions are simple – in my collapsed patient with poor pulses, is there pericardial effusion? Sometimes these questions are more complex – in my patient with respiratory distress, could there be a cardiac cause?
An easy way to integrate your FCU findings is to ask yourself “do these findings fit with my clinical examination?” In other words, did something seem off – was there a tiny left heart in your patient with suspected left congestive heart failure?
CAUTION: to do this effectively, you need to consider the whole heart. If we hyper-focus on one thing – say, a small left ventricle – we may miss other important information. And that is why we go from pericardium-to-right-to-left, in multiple views.
Every test we do, every measurement we perform, has a margin of error – we accept that our measurement could be off by a few points. Precision is how close we are to the true value. Cardiologists by training have greater precision (lower error) than non-cardiologists.† When we report a value, we must accept that it might not be precise. Error is acceptable, providing that we a) acknowledge it exists and b) accept that it exists. Acknowledging error allows us to practice medicine. Accepting error allows us to forgive ourselves for not being perfect. Practice your FCU to improve your precision and clinical integration. If you have a friendly neighborhood cardiologist, don’t be afraid to ask for help! 😊
1. Ng A and Swanevelder J. Resolution in ultrasound imaging. BJA Education 2011;11(5):186-192. doi: 10.1093/bjaceaccp/mkr030
2. DeFrancesco T. POCUS: Heart – Introduction and Image Acquisition. In Lisciandro GR editor. Point-of-care ultrasound techniques for the small animal practitioner, 2nd ed. Hoboken: Wiley Blackwell; 2021, pp. 403-416.
3. Ward JL, DeFrancesco TC. The Role of Point-of-Care Ultrasound in Managing Cardiac Emergencies. Vet Clin North Am Small Anim Pract. 2023 Jul 7:S0195-5616(23)00090-6. doi: 10.1016/j.cvsm.2023.05.017.
4. †This is a topic within my PhD (in progress), where we have seen non-cardiologists tend to have greater error.