CARDIO-RESPIRATORY
Coughing
Small Breed Dogs
by Dr Russel Leadsom BVSc,Cert VC (Veterinary Cardiology)
Reviewed by Dr Alain Carter BVSc, MMedVet(Med) Small Animals
The small breed dog that presents with both a heart murmur and a
chronic cough is often a diagnostic challenge. Is the coughing due to a
respiratory condition, a cardiac condition, or both?
RESPIRATORY
Dogs with a cough due to respiratory conditions often have a history of “kennel cough” that never fully
resolved. Certain breeds such as Yorkshire Terriers
and Chihuahuas may present with a typical “goosehonking” cough suggesting a collapsing trachea that
is expiratory if thoracic, and inspiratory if cervical. Living in a household with cigarette smokers is frequently associated with pulmonary problems.
nary congestion in approximately 30% of dogs. It should
be considered when dogs that have been well controlled
on standard medications develop an intractable cough,
become increasingly breathless with or without cyanosis,
and have persistent inspiratory crackles despite increasing
frusemide doses. The development of a murmur over the
tricuspid valve, together with an increased, or split, second
heart sound, and the detection of ascites would also be suggestive of PH.
Chronic coughing (when the cough is present for
more than 8 weeks) may be associated with chronic
tracheobronchitis, chronic obstructive airway/pulmonary disease, bronchiectasis, idiopathic pulmonary fibrosis and pulmonary hypertension. Inhaled foreign
bodies, tumours, allergies, enlarged lymph nodes and
infections should also be considered.
Confirmation of PH required Doppler investigations.
These dogs are often overweight, and have a normal
to slow heart rate. Accentuated respiratory sinus arrhythmia due to excessive vagal tone is frequently detected on ECG, together with tall P waves (P pulmonale) and a right shift in the electrical axis.
CARDIAC
It is important to appreciate that most dogs that cough due
to a cardiac condition do so in response to an enlarged left
atrium - and not necessarily due to congestive heart failure.
Conditions that result in left atrial enlargement include mitral
valve disease, patent ductus arteriosus and ventricular septal
defects - all of which produce characteristic murmurs.
Auscultation may reveal inspiratory crackles that are
easily misinterpreted as being due to pulmonary
oedema and left side congestive heart failure. Expiratory wheezes may also be evident. If crackles have
been present long term, they are probably due to respiratory disease.
Radiography may reveal a bronchial pattern (`tramlines and doughnuts`), sometimes with an interstitial
pattern o