Causes of Heart Failure

Question 1

What differentials should you think about if the point of maximal intensity is at the base of the heart (dorsal and cranial)?

Answer 1

Physiological flow murmurs
Aortic/Pulmonic stenosis
PDAs

Question 2

What differentials should you think about if the point of maximal intensity is at the the apex of the heart (sternum - caudal and ventral)?

Answer 2

Mitral Regurgitation

Question 3

What differentials should you think about if the point of maximal intensity is at the level of the right ventricle (cranial to left)?

Answer 3

Tricuspid Regurgitation
VSDs

Question 4

What differentials should you think about in small breed dogs with a left apical murmur?

Answer 4

Mitral Valve Disease

Question 5

What differentials should you think about in large breed dogs with a left apical murmur?

Answer 5

Dilated Cardiomyopathy but some breeds can also regularly have MMVD (particularly Cocker Spaniel, Labradors, Collies)

Question 6

In practice, what can you do about a murmur in a puppy or a kitten?

Answer 6

• If loud (grade 3+) more likely to be a congenital anomaly, but loud does not necessarily mean bad (think small VSD)
• If < grade 2 could be innocent – re-assess at 3 and 6 months
• Return to breeder and get money back (rarely done, bond formed)
• Ultimately one can only assess nature and severity of lesion with a full Doppler echocardiogram

Question 7

How can we identify stage B2 MMVD dogs?

Answer 7

• Likely to be largely asymptomatic – sometimes a degree of exercise intolerance is present; coughing
• Murmur grade correlates well with severity of disease; Patients with grade 1-2 murmurs unlikely to have atrial enlargement
• Presence of sinus arrhythmia also good indicator atrial enlargement is unlikely to be present
• Therefore if murmur grade 3+ in a small breed dog then further investigation warranted to confirm if B2 or not;
• If breed suggests DCM also a possibility (discussed later) then regardless of murmur grade investigation warranted

Question 8

What are clues to feline heart disease?

Answer 8

• Murmur: unreliable, can be present in healthy cats and not present in cats with severe heart disease – challenging conversation to have with owners
• Gallop rhythm: more reliable indicator
• Arrhythmia: reliable indicator, less common but majority of arrhythmias in cats caused by feline cardiomyopathy
• May be no clues to identify an asymptomatic cat as having heart disease; will often present in heart failure or even as sudden death
• Breed – Maine Coon/Ragdolls, other pedigrees?
• History – exercise intolerance, intermittent dyspnoea, syncope
• Tachycardia – far less reliable in cats than dogs
• Tachypnoea/dyspnoea

Question 9

What is dilated cardiomyopathy?

Answer 9

• Most common form of myocardial disease in the dog
• Characterised by impaired myocardial contractility with dilation of LV (+/- RV)
• Secondary arrhythmias are common
• DCM is an end stage of many cardiac diseases – primary DCM is a diagnosis of exclusion

Question 10

What are potential underlying causes of DCM?

Answer 10

• Inherited
• Taurine Deficiency
• Carnitine Deficiency
• Toxic/drugs – eg doxorubicin
• Endocrine – hypothyroidism
• Infectious causes leading to myocarditis - possibly under-recognised
• Persistent tachycardia
• Diet? – gluten free diets

Question 11

What are the 2 stages of DCM? What clinical signs are associated to the second?

Answer 11

1. Occult/Asymptomatic phase: Can be prolonged, difficult to detect – limited clues, early arrhythmia clues – intermittent VPCs etc
2. Symptomatic phase: Usually present in CHF◦ Soft left/right apical murmur – enlarged ventricle pulls mitral/tricuspid valve leaflets apart
   ◦ Weight loss
   ◦ Sudden death
   ◦ Lethargy
   ◦ Exercise Intolerance
   ◦ Dyspnoea
   ◦ Symptomatic Arrhythmias
   ◦ Forward failure: pale mucous membranes, sluggish CRT, cool extremities (bad news)

Question 12

What are the 2 common presentations of pericardial disease? What history is associated with each?

Answer 12

• Acute cases
  ◦ Sudden onset exercise intolerance, weakness, collapse, shock, rapid death if untreated
• Chronic cases – more common
  ◦ 2 week history of ascites, progressive exercise intolerance, lethargy, GIT signs, collapse

Question 13

What clinical signs are associated with pericardial disease?

Answer 13

• Jugular distension
• Positive hepatojugular reflex
• Ascites
• Tachycardia
• Muffled heart sounds
• Weak femoral pulses
• Pale mucous membranes
• Tachypnoea/dyspnoea
• GIT signs

Question 14

What causes pericardial effusion in dogs and cats?

Answer 14

Pericardial effusion in dogs
* Cardiac neoplasia (most common)
* Haemangiosarcomas
* Heart base tumors
* Mesotheliomas
* Lymphosarcoma
* Idiopathic (haemorrhagic)
* Left atrial rupture
* Coagulopathies, uremic, infection (bacterial and fungal)

Pericardial effusion in cats
* Congestive heart failure, FIP