Question

This image is from an asymptomatic 6 year old cavalier King Charles spaniel, Harvey, with degenerative mitral valve disease (DMVD).

Should you prescribe pimobendan in this case and why?

What else could you measure using ultrasound to help you decide?

Answer

A) This image is a right parasternal short-axis view at the level of the aortic valve during ventricular diastole (after closure of the aortic valve). The left atrial diameter is 2.75 cm and the aortic diameter is 1.67 cm. The left atrial : aortic ratio is therefore 1.65.

Based on the results of the EPIC trial (Boswood et al. J Vet Intern Med 2016), administration of pimobendan to dogs with DMVD and echocardiographic evidence of cardiomegaly results in prolongation of the preclinical period by approximately 15 months.

The cut-off used in the EPIC trial is a left atrial : aortic ratio ≥ 1.6 or a normalised left ventricular internal diameter in diastole of ≥ 1.7. As Harvey has a left atrial : aortic ratio of 1.65, he is therefore a suitable candidate for pimobendan.

In addition, and to help you decide whether to prescribe pimobendan, you could also measure the left ventricular internal diameter in diastole (LVIDd). This can be measured from the right parasternal short-axis M-mode view at the level of the insertion of the chordae tendinae (Scan B). The Cornell method (Cornell et al. J Vet Intern Med 2004) can then be used to scale the LVIDd to bodyweight. A normalised left ventricular internal diameter in diastole (LVIDdN) of ≥ 1.7 is further evidence there is cardiac remodelling present and a reason to prescribe pimobendan.

How did you get on? This question and answer are from Emily Dutton, tutor on the upcoming small group practical attendance course Practical Cardiac Ultrasound Level 2. This course is for vets in practice who are already confident with a basic cardiac examination of and want to develop their skills further. Read on for hands-on help.....

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