- 4 month old rabbit with progressive cardiac murmur, now a grade 5/6
- less active than his litter mates
- Echo done under midazolam sedation shows an increased LA:Ao ratio =1.64 but LA measurements are within normal reference range for an adult rabbit
- Rest of measurements are as follows: LA=8.1, AO=4.9, IVSd=3.11, LVIDd=10.5, LVPWd=4.0, IVSs=5.6, LVIDs=6.1, LVPWs=4.5, FS=42%, HR=250bpm
- 4 month old rabbit with progressive cardiac murmur, now a grade 5/6
- less active than his litter mates
- Echo done under midazolam sedation shows an increased LA:Ao ratio =1.64 but LA measurements are within normal reference range for an adult rabbit
- Rest of measurements are as follows: LA=8.1, AO=4.9, IVSd=3.11, LVIDd=10.5, LVPWd=4.0, IVSs=5.6, LVIDs=6.1, LVPWs=4.5, FS=42%, HR=250bpm
- Based upon Casamian-Sorrosal and Saunders et al. article in the Journal of Veterinary Cardiology, (M-mode, two-dimensional and Doppler echocardiographic findings in 40 healthy doemstic pet rabbits), I am seeing decreased preload and increased function.
- Color flow Doppler showed no AV or PA insufficiencies. In some views, AO blood flow was turbulent but velocity measured 1.0-1.5m /s.
- I was using a 6S-RS probe for the Doppler studies which may have been too low a frequency for this 1.5kg rabbit. Could that make me miss an insufficiency?
- Could the turbulent aortic blood flow be due to a subaortic stenosis?
- Am I missing a VSD? I have a clip with the color flow doppler on the TV valve in transverse RP LA view, but only see a mosaic pattern on the aorta and nothing at the level of the TV valve.
- If this rabbit had a VSD that was causing a grade 5/6 murmur, wouldn’t I be seeing left ventricular volume overload?
Comments
Hi!
I must admit that I don’t
Hi!
I must admit that I don’t echo many rabbits
I think that there are not many rabbit owners in Austria who would let me do an echo in a 4 month rabbit 
A VSD is certainly possible. Small VSDs are typically louder than large ones. Means that insignificant VSDs can cause a loud heart murmur.
The direction of the flow on the color image could match with a VSD but I`m not certain because I cannot really see the VSD itself. A tricuspid regurgitation without any other changes is unlikely to cause a heart murmu 5/6.
Re the probe used for color Doppler: Usually lower frequency probes give you better color Doppler signals, but less 2D detail. Maybe use a higher frequency probe to get a better 2D resolution so that we can combine the color and 2D information.
Best regards!
Peter
Thanks Peter. the rabbit
Thanks Peter. the rabbit belongs to a breeder who obviously wants to know what is happening in her line. I don’t see an obvious defect in the RPLVOV view obtained with my curvilinear 8C-RS probe, posted above. I will see if I can add another clip. The primary vet is concerned that the increased intensity of the murmur signifies severe heart disease. Based upon my reference values, there is no left ventricular volume overload. The left atrium measures normal in size even though the LA to Ao ratio is increased. Based upon the measurements I have given and the images posted above, it just doesn’t seem like heart failure is imminent. What do you think? Any other thoughts besides a small VSD?
Yes, I agree, heart failure
Yes, I agree, heart failure is not imminent here.
Ddx for a loud systolic heart murmur are VSD, mitral regurgitation or outflow tract obstruction. Since your AO velocity and PA color Doppler were normal, VSD and mitral regurgitation (due to dysplasia) are the only remaining Ddx (apart from very very rare ones…)
Re aorta: Of course there can be turbulence without markedly increased vmax, but this would be unlikely to cause a loud heart murmur…
Peter
Thanks Peter!
Thanks Peter!