6 year old dog with subaortic stenosis

Today’s case was a preoperative (non-cardiac surgery) echocardiogram for a six year old smooth coated terrier. The vets wanted to check that his heart was strong enough for anaesthesia.

His left ventricular systolic function looks good, but even at first glance it can be seen that this dog has mild concentric hypertrophy. Common causes of hypertrophy are:

  • Uncontrolled hypertension
  • Aortic stenosis
  • Hypertrophic cardiomyopathy (rare in dogs, and may not be concentric)

 

We always check the mitral valve in dogs, but in this dog, we were most interested in the aortic valve. The valve itself appeared to open well, but there is clearly some turbulence before the valve highlighted by the colour Doppler. There also appears to be a shelf-like narrowing just before the left ventricular outflow tract.

 

Possible subaortic stenosis

Possible subaortic stenosis

Turning the dog over and examining from the 5 chamber view, it was possible to confirm some degree of stenosis using continuous wave Doppler, and actually confirm the location of the partial obstruction using pulsed wave Doppler.

 

By retracting the pulsed wave sample gate back into the left ventricle, we can precisely identify the point at which the obstruction begins (the point at which the PW trace exceeds the limits of our maximised scale). Before this point, velocities are normal, although in this case we are so far back into the left ventricle we are unable to obtain a smooth PW trace – flow is not laminar this far back into the left ventricle.

Continuous wave Doppler (shown below) allows us to identify the peak, which is almost 3m/s or 36mmHg. A gradient below 40mmHg in the presence of good left ventricular systolic function usually corresponds to mild aortic stenosis, and that does indeed fit with the overall echocardiographic and clinical picture for this dog.

Continuous Wave trace

 

Bonus points if you also spotted the trivial jet of aortic regurgitation, shown again below:

 

Aortic regurgitation

 

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