Echocardiography is a safe, easily accessible test that allows for the rapid assessment of the structure and function of the heart. Any vet with access to an ultrasound machine can perform a basic heart scan – it is not necessary to have specialised software or a phased array probe to screen for severe cardiac disease. The barrier to the widespread use of echocardiography is, therefore, the skill and experience of the user, not access to the right equipment.
The dangers of misdiagnosis by those without adequate experience or training are real. However, the cumulative loss of information from echocardiography that could positively impact patient management (as well as the career development of veterinarians otherwise too nervous to place an ultrasound probe on the chest) is arguably more damaging.
This article aims to combat this with a summary of three ways you can start building confidence with echocardiography.
1) Have a protocol
It is essential to have a protocol you follow for echocardiography, no matter how short it may be. In fact, it is better to become confident in obtaining and interpreting a limited number of views than to attempt an overly ambitious protocol that raises more questions than answers!
It is essential to have a protocol you follow for echocardiography, no matter how short it may be
Video 1 demonstrates four views you can obtain with only a microconvex probe, from which you can begin to make a visual assessment of the size and function of a patient’s heart.
Being able to visually assess chamber size, wall thickness and systolic function does require experience, but it will be easier to commit to practising on every patient you can if you stick to a realistic protocol with just a few views (or even a single view at first). This also allows you to build up experience quickly.
Nevertheless, scanning alone without access to feedback is difficult. The quality of the one-off lectures and short courses available now is excellent, but the best way to maintain and build upon this knowledge is to become part of a lifelong learning programme and community committed to consistently exposing you to cases. (There is more on this at the end of this article.)
2) Be aware of the common pitfalls
There are common yet avoidable mistakes people make when gaining experience with echocardiography, which ultimately make accurate interpretation of findings difficult.
The first is not recognising an off-axis image (Videos 2A and 2B). The right parasternal long-axis views are the first views we obtain for dogs and cats and form the basis for the rest of the examination. If your long-axis views are off-axis, your short-axis ones will also suffer.
Another very common mistake is foreshortening (Video 3). This is where you have under- or over-rotated the image and are effectively somewhere between the long and short axis. For example, a dilated left ventricle may have a rounded appearance, but when visualised from the right parasternal long-axis or apical views, a normal left ventricle does not.
Finally, be careful to cut chambers cleanly. In the case of the left ventricle, you should aim to exclude papillary muscles and chordae tendinae from your imaging plane. Obliquely cutting chambers is one of the most common reasons for misinterpreting normal structures as masses.
3) Make subjective assessments
There is a lot of pressure to obtain measurements from echocardiograms, particularly an LA:Ao ratio (the ratio between the diameter of the aorta and the diameter of the left atrium, usually taken from the short-axis 2D image) in canine and feline patients and wall thickness in felines – two of the most difficult measurements to perform well!
Relying on measurements when you first start can absolve you from having to interpret the image yourself and can easily give false reassurance
Reporting measurements before you are confident with your imaging is inadvisable: firstly, because your measurements will have poor reproducibility and may be inaccurate; and secondly, because you need to train your own interpretation skills. Relying on measurements when you first start can absolve you from having to interpret the image yourself and can easily give false reassurance.
Up for a challenge? Then check out the images below and see if you can answer the corresponding questions.
- Do you need to measure to tell which of these ventricles has increased wall thickness?
- Do you need an LA:Ao ratio to tell you which dog’s left atrium is dilated in the videos below?
Summary
As long as you know your own limitations, cardiac ultrasound is an indispensable tool for any first opinion or emergency veterinary professional. However, many individuals feel too intimidated to begin using echocardiography or abandon it quickly. This is because they feel pressured to immediately produce measurements they know are unreliable or perform full Doppler studies before they’re in a position where the added time to do so will actually make a difference to their diagnosis.
As long as you know your own limitations, cardiac ultrasound is an indispensable tool […] however, many individuals feel too intimidated to begin using echocardiography
To build confidence and reproducibility with echocardiography, remember:
- Start with just a few views and try to improve on them each time you scan
- If your image is off-axis, foreshortened or of poor quality, definitely don’t measure!
- When ruling for severe pathology, your subjective assessment is always worth more than a measurement
Don’t forget that having access to a community of fellow users of echocardiography can help you accelerate your learning through providing exposure to the case mix, experience and knowledge of others. It also provides access to expert mentors who will support you in correcting any imaging errors.
