Feline Cardiomyopathies

Question 1

Discuss myocardial disease in the cat?

Answer 1

They are NOT small dogs

Valvular disease is rare in the cat

Myocardial disease is the commonest heart disease in the cat.

Multiple types of myocardial disease is the cat (does it really matter though as they all present with HF and are treated the same):

• HCM (HOCM)
• RCM (restrictive cardiomyopathy) Most common type
• DCM (dilated cardiomyopathy)
• ARVC (arrhythmogenic right ventricular cardiomyopathy)
• FUCM (Feline unclassified cardiomyopathy)

Hypertrophic cardiomyopathy (HCM) is the most common type of myocardial disease in the cat

Exact cause is unknown but a genetic bases is thought to underlie many cases

Question 2

What is the definition of hypertrophic cardiomyopathy?

Answer 2

Definition

• Inappropriate myocardial hypertrophy of a non-dilated left ventricle, occurring in the absence of an identifiable stimulus (e.g don’t have aortic stenosis, hyperthyroidism)
• External diameter of ventricle remains normal but hypertrophy of heart muscle reduces the size of the lumen of the ventricle

Question 3

How is hypertrophic cardiomyopathy diagnosed?

Answer 3

Diagnosis of exclusion

Aortic stenosis

Systemic hypertension

• Primary, Diabetes Mellitus, Cushing’s disease

Metabolic disorders capable of inducing hypertrophy

• Hyperthyroidism
• Acromegaly

Renal disease

Acromegaly? If it causes hypertrophy or just increases severity of HCM patients

Hyperthyroidism involved in the creation of hypertension and hypertrophy

Renal disease, Cushings, diabetes

Question 4

Discuss hypertrophic cardiomyopathy?

Answer 4

• Wide phenotypic variability
• Principally affects LV
• Hypertrophy is not symmetrical (e.g intraventricular septum in a is huge and free wall is not)

A -all segments of LV

B –diffuse asymmetric (+ septum)

C –diffuse asymmetric (+ FW)

D –diffuse (+ Septal bulge)

E and F –Basal septum and FW

B and D are the most common

Question 5

What are the two clinical forms of hypertrophic cardiomyopathy?

Answer 5

Two clinical forms:

• Obstructive
• Non obstructive

Question 6

Discus HCM obstructive form?

Answer 6

• Dynamic left ventricular outflow tract obstruction
• Due to abnormal movement of the anterior mitral valve leaflet in systole –Systolic anterior motion of the mitral valve (SAM)
• Turbulent blood flow in LVOFT
• Concurrent eccentric jet of mitral regurgitation along the posterior wall of the left atrium

Question 7

Describe systolic anterior motion of the Mitral valve?

Answer 7

Question 8

What are the typical features of hypertrophic cardiomyopathy?

Answer 8

Typical features of feline form

Animal model of human disease

• Disproportionate hypertrophy of the septum
• Myofiberdisarray or malalignment
• Arteriosclerosis “small vessel disease”

Question 10

Discuss hypertrophic cardiomyopathy?

Answer 10

• Commonest acquired heart disease in cats
• 3 genetic mutations now discovered (2 in Maine Coon cats and 1 in Ragdoll cats)
• Rare in dogs
• Excessive LV hypertrophy without dilation
• Cause unknown but probably genetic
• LV hypertrophy involving LVFW +/-IVS
• Extent and distribution of LVH is variable
• LA enlargement varies depending on the severity of diastolic dysfunction
• Reason CO falls is that the ventricle cannot fill adequately. A disorder of diastole as it cannot fill properly. HF develops because CO falls and reason CO falls in cats is that the ventricle cannot fill properly meaning in the atria in cats become disproportionately large.

Question 11

What is the clinical presentation of hypertrophic cardiomyopathy?

Answer 11

• Very variable
• Range from asymptomatic cat with a heart murmur to recumbent, cold dyspnoeic cat via congestive cardiac failure
• Often increased respiratory rate at rest/panting (be concerned if a cat is panting is very rare they do this)
• If stressed then can lead to severe dyspnoea
• Often presented at a late stage
• Acute onset lameness / paralysis secondary to HD due to thromboembolism
• Sudden death
• Sedentary house cats often don’t present until disease is well advanced

Question 12

Discuss the general history of a hypertrophic cardiomyopathy cat?

Answer 12

General history

• Vaccination, worming, FeLV, FIV status etc
• Appetite (1 st thing owner may notice, cardiomyopathy are cachexic conditions they loose weight very quickly), drinking habits
• vomiting, diarrhoea
• Respiratory rate
• panting?
• Coughing
• usually a sign of respiratory disease
• Exercise tolerance

Question 14

Discuss a general clinical exam with regards to cardiovascular system?

Answer 14

CV system

• Mucous membrane colour
• Femoral pulses
  
  • Bilateral, Quality, regular, pulse deficits
• Extremities?
• Palpate apex beat on both sides
• Chest compressibility (useful in cats as intrathoracic disease is common cause of resp signs, if you have a mass then compressibility is compromised)
• Chest percussion
• Auscultation
• Remember cats are NOT ALWAYS TACHYCARDIC

Question 15

How to perform cardiac auscultation?

Answer 15

• Quiet room
• Standing position
• Avoid warm room to minimise panting
• Purring! (tricks to stop cats purring turn on a tap or tap on nose)
• Well restrained patient

Question 16

Hypertrophic cardiomyopathy auscultatory findings?

Answer 16

• Many have auscultatory abnormalities
• Systolic murmur point of maximal intensity sternal border
• Often dynamic murmur
• Gallop sounds with severe HCM (s3/s4 get louder as ventricles having trouble filling)
• Crackles throughout lung fields due to pulmonary oedema
• Dull lung and heart sounds due to pleural effusion
• Murmurs and gallop sounds often louder over sternum in cats

Question 17

Compare normal heart sounds and gallop sounds?

Answer 17

Question 18

Discuss electrocardiography with regards to HCM?

Answer 18

• A large proportion of cats with myocardial disease have abnormalities on ECG
• Morphological changes due to chamber enlargement
• Conduction abnormalities (QRS complexes look abnormal in lead 2 ECG)
• Arrhythmias (rare to need to medcially manage rhythm disturbances in cats)
  
  • Ventricular arrhythmias including VT
  • Atrial fibrillation

Question 19

Echo findings in HCM?

Answer 19

• LV hypertrophy often asymmetrical
• Basal septum frequently affected
• Hypertrophied, hyperechoic, irregular papillary muscles
• LVH >6mm (5.5mm, 5mm) IN DIASTOLE
• 2DE measurements as well as M Mode
• LV lumen is usually small
• LA enlargement is variable -mild to severe
  
  • Can have obstructive component –Systolic anterior motion of the mitral valve (SAM)

Question 20

What can be seen here?

Answer 20

Typically HCM cat free wall is about 1cm thick

Question 21

What can be seen here?

Answer 21

IVS measurement a little over what it should be

• Enlarged

Question 22

What can be seen here?

Answer 22

• LA thick/papillary muscles
• anterior mitral leaflet being sucked into outflow track

Question 23

Discuss papillary muscles in HCM?

Answer 23

• Hyperechoic
• Hypertrophied
• Irregular endomyocardial border
• Thick myocardium, irregular hyperechoic pappilary muscles
• Variable echogenecity. Bright white areas assume is fibrosis.

Question 24

Look at these hypertrophic obstructive cardiomyopathy?

Answer 24

Question 25

What can be seen here?

Answer 25

SAM (Systolic anterior motion of the mitral valve) AMVL being sucked into base of aorta causing an obstruction

Question 26

What can be seen here in M Mode?

Answer 26

Question 27

What can be seen here?

Answer 27

Dynamic left ventricular outflow tract obstruction

Question 28

Discuss dynamic right ventricular outflow tract obstruction?

Answer 28

* This occurs in some cats and leads to a right sternal border murmur * Exact significance of DRVOFTO is uncertain but is does occur in higher frequency in those cats with significant left sided disease * Very rarely severe enough to warrant treatment * Leads to a right sided sternal murmur

Question 29

What is this?

Answer 29

Dynamic right ventricular outflow tract obstruction

Question 30

What can be seen here?

Answer 30

RPSA (right parasternal short axis) * LA (left atrial) dilation * LA enlargement. * Atleast 2 aortas size. * Look for if there is slow static blood swirling around in atria particulary is there a thrombus these cats are predisposed to developing clots and therefore thromboembolic disease.

Question 31

What can be seen here?

Answer 31

LPLA (left parasternal long axis) * Smoke * Slow blood swirling around in LA

Question 32

Discuss thoracic radiography?

Answer 32

Imperative for diagnosing heart failure Ideally only when patients are stable Cardiogenic pulmonary oedema can be very variable in cats with heart failure **Triad of signs (LCHF)** * Interstitial / alveolar infiltrate * Cardiomegaly * Pulmonary venous congestion The majority of cats with CHF will have pulmonary oedema

Question 33

What can be seen here?

Answer 33

* Cat hearts should be 2 rib spaces wide and should look like a lemon. * Dorsal enlargement is often seen as atria get really big in cats. * PVs enlarged.

Question 34

What can be seen with feline HCM?

Answer 34

Atria get big=classic valentines heart as ventricles remain same size

Question 35

Look at these images of left atrial enlargement and right atrial enlargement?

Answer 35

Question 36

Discuss restraint for radiography?

Answer 36

Restraint o Conscious vs . sedation/GA * Cardiovascularly stable (treat CHF) **Dogs:** Care in hypotensive or bradycardic patients, or if right to left shunting defect * ACP 0.01 –0.03 mg /kg * Butorphanol0.1 –0.4 mg/kg **Cats:** ACP / Butorphanol: OK if cat is initially calm. * 0.05 mg/kg ACP; 0.2 mg/kg Butorphanol. Midazolam/ ACP / Ketamine * 0.2 mg/kg midazolam * ± 0.05 mg/kg ACP * 5 mg/kg ketamine Sevoflurane induction chamber Propofol has been shown to mildly reduce systolic function but does not alter diastolic function

Question 37

Discuss pleural effusion in cats with HCM?

Answer 37

Many cats with HCM present with a pleural effusion Modified transudate/chylous/pseudochylous When left sided heart failure –Why? Several theories: * Pulmonary hypertension from LCHF causing right sided heart failure * Feline visceral pulmonary veins drain into the pulmonary veins

Question 38

List other forms of cardiomyopathy?

Answer 38

Multiple types of myocardial disease is the cat: * HCM (HOCM) * RCM (restrictive cardiomyopathy) * DCM (dilated cardiomyopathy) * ARVC (arrhythmogenic right ventricular cardiomyopathy) * FUCM (Feline unclassified cardiomyopathy) Clinical presentation and management very similar to HCM Differentiated on echo only Manage what is in front of you!

Question 39

Discuss restrictive cardiomyopathy?

Answer 39

* Unknown aetiology probably multifactorial as there is range of pathological findings * Could be end stage of other disease processes

Question 40

What are the two forms of restrictive cardiomyopathy?

Answer 40

2 Forms * Endomyocardial (fibrosis tends to affect the endomyocardium) * Myocardial

Question 41

What is the pathophysiology of restrictive cardiomyopathy?

Answer 41

* Extensive endocardial, subendocardialor myocardial fibrosis * Atrial enlargement (usually very large!) * LV (normal, increased or decreased) * Mild LV hypertrophy * Diastolic failure * These cats cant fill their hearts properly

Question 42

What can be seen here?

Answer 42

Endomyocardial Restrictive CardioMyopathy

Question 43

Discuss dilated cardiomyopathy?

Answer 43

* Taurine deficiency was a major cause in the 80s * Taurine levels in commercial diets has been increased and now DCM secondary to taurine deficiency is rare – * DCM often end stage of another myocardial abnormality –toxic, drug induced, CM or infection

Question 44

Discuss features of Dilated cardiomyopathy?

Answer 44

* Features similar to dogs * Poor contractility * Dilation of all 4 chambers especially LV and LA * Arrhythmias (common) * Pleural effusion (modified transudate) (common) * Older cats * Frequently present in heart failure * Some present in output failure * Bradyarrhythmiascan also occur * Diagnosis as with HCM * Always check Taurine levels * supplement as indicated * Treatment as HCM when in CHF plus pimobendan (a + inotrope not licensed in cats)

Question 46

Discuss cardiomyopathy complications?

Answer 46

* Recurrent Pleural effusion * Refractory heart failure * Thromboembolic disease * Sudden death

Question 47

Discuss thromboembolic disease?

Answer 47

* Common complication to HCM, RCM, FUCM * Often sudden onset of clinical signs * Mistaken for neurological/traumatic disease * Thrombus forms in atrium, part trunks off and then lodges at the distal aorta and animals go off their back legs. Sometimes can affect front legs. * **3 things for clot to form:** Damage to endocardium, static blood flow, cats are naturally hypercoagulable

Question 48

What is the pathophysiology of thromboembolic disease?

Answer 48

* Thrombus lodges in terminal aorta – saddle thrombus –most common (\>90% cats) * Some cats (\<10%) thrombus in brachial artery / renal artery * Some cats thrombus in mitral valve –Sudden death!

Question 49

What does a clinical exam of a thromboembolic disease yield?

Answer 49

* Cold, cyanotic, paralysed hind limbs * Absent femoral pulse * Hypothermia * Painful firm muscles * Vocalisation * +/-dyspnoea due to CHF * Can present as sudden death * Often first sign you get that cat has heart disease

Question 50

How is thromboembolic disease diagnosed?

Answer 50

* Cardiac evaluation * Clinical pathology * Renal function, muscle enzymes * Measure blood flow with Doppler * Ultrasound terminal aorta

Question 51

What is the treatment for thromboembolic disease?

Answer 51

* Analgesics -opiates * Prevent further thrombus formation * Aspirin, clopidogrel, LMWH (low molecular weight heparin) These don’t break clots down just stop them getting worse * Treat CHF * NURSING CARE * (thrombolytic agents??) * Amputation?

Question 52

Discuss outcome of thromboembolic disease treatment?

Answer 52

* Reperfusion injury * MONITOR potassium levels * All dead cells release potassium on reperfusion which causes real rhythm problems as K goes up. Can be life threatening. * Ions are released once reperfusion occurs due to damaged muscle * Metabolic acidosis and hyperkalaemia can be life threatening * 1/3 survive, 1/3 die, 1/3 PTS –one study!