Thursday, June 27, 2013

Three things I learned: heart disease in dogs

Dog with glasses on.
Dixie in academic mode.

Veterinary cardiologist Rita Singh gave an excellent webinar for the Australian   Small Animal Veterinary Association reviewing mitral valve disease, dilated cardiomyopathy and patent ductus arteriosus in canine patients. Three things I learned:
  1. Although I was taught that coughing was a sign of congestive heart failure (likely due to compression of bronchi due to left atrial enlargement), recent studies including one by Ferasin et al in the Journal of Veterinary Internal Medicine (2013:27) found that there was no association between heart failure and cough. Dogs in heart failure definitely presented with dyspnoea and tachypnoea, but if a small breed dog presents for a cough without tachypnoea there should be a work up for airway disease. Singh herself published a study (JVIM 2012:26) which found that many of these coughing dogs also had airway disease.
  2. While no treatment is shown to prolong the time it takes for dogs with sub-clinical mitral valve disease to progress to heart failure, treatment with pimobendan MAY slow the progression of disease in dogs with subclinical cardiomyopathy (as per Summerfield JVIM 2012:26). 
  3. PDA is the most common congenital heart disease in dogs (esp miniature and toy poodles, collies, shelties, yorkies, pomeranians) and 65% will develop heart failure within one year. Surgical ligation of a PDA can be used to treat the condition but the use of devices to occlude the vessel are more commonly used now. Complication rates are low but the biggest complication is haemorrhage.
In question time Singh revealed that cardiologists are less reliant on the vertebral heart score to determine cardiomegaly (they are more likely to base their judgement of the presence or absence of cardiomegaly on experience) and it has become very common to assess progression of heart disease from the resting respiratory rate. No matter the size of the patient, an RR of under 30 is good, but dogs with an RR of 40-60 may have moderate heart failure.