Subaortic Stenosis (SAS)

Subaortic Stenosis (SAS)


  • DEFINITION (What it is):
    • Subaortic Stenosis (SAS) is a disease where the aorta, as it leaves the left ventricle, is narrowed.
    • The narrowing can be mild, moderate, or severe
      • The narrowing is caused by scar-like tissue just underneath the aortic valve (hence the name subaortic (underneath the aorta) stenosis (narrowing).
      • The narrowing makes it more difficult for the heart to pump blood forward to the body.
      • The heart muscle, to compensate, gets very thick (just as lifting heavy weights causes muscles to get larger)
    • This causes
      • As the heart muscle thickens, blood supply to the heart muscle is inadequate, and scarring of the heart muscle itself results from this inadequate blood supply.
      • This scarring causes rhythm disturbances of the heart, and it is these rhythm disturbances that generally lead to problems.
        • The hallmark of this disease is sudden death.
          • These dogs are generally without any symptoms, and then die suddenly from a lethal rhythm disturbance.
      • Some animals may develop congestive heart failure, with fluid in the lungs, but this is not nearly as common.
  • EPIDEMIOLOGY (Who gets it):
  • This is one of the most common congenital (from birth) defect seen in large breed dogs
    • about 21% of all puppies that have a heart birth defect will have SAS
    • This defect tends to affect large breed dogs
      • Golden Retrievers have very high increased risk, followed by Newfoundlands, Rottweilers, Bichon frise and Pomeranians
    • It can occur in larger breed dogs, though other defects are more common
      • German Shepherd dogs are prone to this defect
  • Only about 10% of kittens with congenital heart defects will have a PDA


  • CAUSE:
    • In dogs it has been shown that the lack of closure of a PDA is due to lack of proper muscle in the PDA
      • There is probably a genetic component since we see this commonly in certain breeds, but these genes have not been identified
    • In humans, some PDA’s will close when given Indomethacin, an aspirin- like antiprostiglandin to contract muscle in the PDA
      • So giving Indomethacin to puppies does not work


  • CLINICAL SIGNS (with a patent ductus arteriosus):
    • Many puppies will simply have a murmur detected on their puppy examinations
    • Others, when they have already developed congestive heart failure (fluid in the lungs)
      • They may not be as active as normal puppies
      • They will breathe fast and may cough
  • DIAGNOSTICS (See Tests We Often Perform)

    • Echocardiography (heart ultrasound)
      • Definitive diagnosis of the PDA is made by echocardiography
        • The consequences to the heart will also be evaluated
        • The presence of other defects will be determined
    • Radiographs (x-rays)
      • We usually will want radiographs, to make sure there is no fluid in the lungs (congestive heart failure)
  • THERAPY
    • If there is congestive heart failure present, treatment until surgery can be performed
      • Diuretics (furosemide)
        • Decrease the amount of fluids that the heart has to handle and get rid of fluid in the lungs
      • Inodilators (pimobendan) in some, but not all cases
        • Make the heart pump blood forward more effectively
    • The definitive treatment for PDA closing the defect
      • There are two methods, surgery or an occluder device
        • Surgery
          • The surgery should be performed as soon as possible, and there is no puppy too small to close in the hands of an experienced surgeon
            • If one waits with this disease, the puppy may go into congestive heart failure and be more difficult to anesthetize
          • Death rates of puppies undergoing PDA surgery, in the hands of experienced surgeons, are very low. Certainly less than 5%
        • Occluder devices
          • These have the advantage of being less invasive
            • The device is placed through an incision in the groin
            • Complication rates are very low
          • There is generally no cost advantage over surgery
          • Occluder devices cannot be used in every case
            • The pet is too small
            • The PDA is of the wrong shape to handle the device
  • PROGNOSIS
    • With closure, excellent
      • They have normal life spans and exercise tolerance
      • It is extremely rare for any of these pets to be on long term medications afterwards
    • Without closure, many of these pets will go on to have congestive heart failure (fluid in the lungs)
      • The heart failure is very difficult to treat
  • FOLLOW UP CARE
    • We understand that your money has to be spent wisely to be able to monitor and treat your pet for it’s lifetime, so we are very respectful of your finances and yet provide excellent care for your pet
      • We work as a team with your family veterinarian, and maintaining routine and non-specialist care is a very important part of our consideration
    • We will generally perform another echocardiogram about  week after surgery to make sure any residual valve leaks are resolving
      • If there is damage to the heart from the PDA, we may have to perform repeat echocardiograms at infrequent intervals
    • Generally, you are back to your family veterinarian for routine care for a lifetime!