Most veterinarians incorporate the left apical 4 and 5 chamber views into their standard echo examinations, as they move from beginner into intermediate and advanced level echocardiography. Adding the 2 and 3 chamber apical views into your examination will help you to build up an even more comprehensive picture of your patient. Below are just some of the reasons why you may want to add these views into your examination.
The way in which your ultrasound beam cuts through the mitral valve affects your impression of the valve and any regurgitation which is present. From the left apical 2 chamber view, for example, you are cutting the mitral valve through its commissures – along the meeting point of the two leaflets. From the 3 chamber view, you are cutting the mitral valve through the middle of both leaflets, as if you were dividing them both into two. These almost perpendicular cross-sections of the valve can give you a much more complete picture of the severity and point of origin of a regurgitant jet, as well as being essential for searching for small lesions such as endocarditis.
In dogs with dilated cardiomyopathy, it is important for experienced users to calculate the volume of the left ventricle and compare it to the normal values for that breed, particularly if you are screening for DCM and have a patient who is borderline. If you rely on a single view, you may fail to show the left ventricle at its maximum extent, and underestimate its volume. More views are always better for these difficult cases!
Hypertrophy may be more visible from one view than another, or so asymmetric that one apical view may demonstrate complete cavity obliteration where another does not. If you are trying to decide whether or not there is obstruction at the mid-cavity level, multiple views are essential.
Measuring the left atrium is important in both dogs and cats, and a dilated left atrium is present in the vast majority of cardiac diseases that we see. The left atrium does not dilate uniformly in all directions, and may be disproportionately enlarged along a single plane – which is precisely why we should not rely solely on the LA:Ao ratio. The more views you can examine and measure the left atrium in, the better. In cats with dilated left atriums, you can also get an excellent view of the left atrial auricle from the left apical 2 chamber view, as well as obtain a PW Doppler trace from this area, so it’s definitely a view that is worth gaining familiarity with and practicing on as many patients as possible.
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