Canine cardiomyopathies

Question 1

What type of CMO do large and giant breed dogs get?

Answer 1

Dilated CMO

Question 2

What is the definition of a canine cardiomyopathy?

Answer 2

Primary heart muscle disease of uncertain aetiology

Usually poor contractility, dilation, +/-arrhythmias - progressing to CHF

Question 3

What is the general prognosis for CMO’s?

Answer 3

Guarded to poor

Question 4

What is special about Boxer dogs?

Answer 4

They get their own unique CMO

Arrhythmias and sudden death, not necessarily with dilation

Question 5

What is the proper name for Boxer CMO?

Answer 5

Arrhythmogenic right ventricular cardiomyopathy of Boxers

Question 6

What dog signalment is most common in presenting with dilated cardiomyopathy?

Answer 6

Large to giant breeds
4-10 years old
Males more than females
Rare in dogs under 12kg

Question 7

What percentage of Irish Wolfhounds and male and female Doberman’s eventually develop dilated cardiomyopathy?

Answer 7

25% Irish wolfhounds
50% Male Doberman’s
33% Female Doberman’s

Question 8

Describe the pathophysiology of DCMO?

Answer 8

Weak muscle, decreased ventricular contractility
Systolic dysfunction, low output HF
Progressive chamber enlargement, failure of valves to close and eventual diastolic stiffness
Right and Left sided CHF
Atrial fibrillation commonly develops
Loss of atrial ‘kick’ and persistent tachycardia
Lower C.O. and disease progression
Ventricular tachyarrhythmias can also develop and cause sudden death

Question 9

What is the length of disease progression in DCM and the development of clinical signs?

Answer 9

Prolonged preclinical occult stage that can last years

Once clinical signs develop they die shortly after

Question 10

How can you detect occult disease in DCM?

Answer 10

By echocardiography

Question 11

What are some clinical features of a dog with DCM?

Answer 11

Exercise intolerance
Weakness
Lethargy
Tachypnoea (rapid breathing)
Dyspnoea
Cough
Anorexia
Abdominal swelling
Syncope
Cardiac cachexia

Question 12

Why do you get cardiac cachexia in dogs with DCM?

Answer 12

Aren’t pumping blood properly to the muscles
Cytokines are released
Causes a decrease in muscle mass

Question 13

How do you diagnose a dog with a suspected DCM?

Answer 13

Signalment and history
Systolic mitral and/or tricuspid murmur (might be v. soft)
+/- gallop
+/- irregularly irregular arrhythmia
+/- pulse deficits, weak femoral pulse
+/- Mucous membranes pallor, slow CRT, cold extremities
+/- signs of CHF

Question 14

In DCM why can the murmur be very quite/soft?

Answer 14

Because of the weak muscle contraction

Question 15

What are the 4 treatment principles for canine DCM?

Answer 15

Diuretic to relieve congestion
Positive inotrope to support ventricular function
ACEI to oppose RAAS, reduce salt and water retention, mildly vasodilate
Anti-arrhythmic drugs as needed

Question 16

During the occult stage of canine DCM, how could you potentially treat them?

Answer 16

Any treatment may or may not help much
ACEI - enalapril, benazepril
Spironolactone
Beta blockers
Anti-arrhythmic drugs

Question 17

How do you treat a dog in the overt stage of DCM?

Answer 17

Just like CVHD plus anti-arrhythmic therapy
Complete exercise restriction initially
Frusemide at lowest effective oral dose
Pimobendan (inodilator)
ACEI
+/- Digoxin - beware toxicity
+/- Spironolactone - aldosterone antagonist

Question 18

When putting a dog on digoxin for DCM, what signs must you tell the owners to look out for and why?

Answer 18

Going off their food and vomiting
Next can get cardiac toxicity to an already sick heart
Can be very toxic and need to measure the level of it in serum

Question 19

How do you monitor a dog with DCM?

Answer 19

Regular ECG and Echo - see the strength of the heart
At home - resting respiratory rate/effort and heart/pulse rate and rhythm
Body weight and condition score
Serum electrolytes, creatinine maybe
Arterial blood pressure measurement
If on digoxin, monitor serum concentration of it

Question 20

In dogs with DCM, after the onset of CHF what is the average survival length?

Answer 20

6-12 weeks

Question 21

In DCM, what sign is a poor prognostic indicator?

Answer 21

Pleural effusion

Question 22

Name 5 secondary CMO’s in dogs?

Answer 22

Doxorubicin (anti-cancer drug)
Toxins and poisonous plants
L-carnitine and taurine deficiency
Myocardial infarction
Tachycardia-induced CMO (from an accessory pathway)