Acquired CV disease of cats

Question 1

Commonest acquired cardiac disease - CATS

Answer 1

Myocardial - i.e. cardiomyopathy
Congenital - less common
Primary arrhythmias - also less common
Primary valvular disease - extremely rare
Pericardial disease - much less common than dogs

Question 2

Types of cardiomyopathy

Answer 2

Same classification as humans:
****Hypertrophic - HCM****
Dilated - DCM
Restrictive - RCM
Arrhythmogenic - ARVC

Question 3

Key features - HCM

Answer 3

Concentric LV hypertrophy (disatolic septum or free wall thickness > or equal to 6mm)
Poor LV relaxation
Stiff LV

Question 4

Key features - DCM

Answer 4

Dilated LV with thin LV walls

Hypokinetic LV

Question 5

Key features - RCM

Answer 5

Marked atrial dilation
No LV hypertrophy or dilation
Stiff LV

Question 6

Key features - ARVC

Answer 6

Left heart relatively normal
Severe dilation of RA and RV
RV wall thinning

Question 7

List examples of secondary myocardial disease

Answer 7

Hyperthyroid myocardial disease
Hypertensive myocardial disease
Cardiomyopathy secondary to hypersomatotropism (acromegaly)

Question 8

When is it difficult to identify the original form of myocardial disease?

Answer 8

when pathological processes such as myocarditis or infarction are also present

Question 9

Another name for HCM

Answer 9

Idiopathic (or genetic) left ventricular hypertrophyy (i.e. NOT due to systemic hypertension, aortic stenosis or hyperthyroidism)

Question 10

Mutations - HCM

Answer 10

Human - usually associated with genetic mutations in sarcomeric proteins

Mutations in myosin binding protein C identified in Maine Coons and Ragdolls with HCM

Question 11

Pathophysiology - HCM

Answer 11

MILD DISEASE: Impaired ventricular relaxation and increased ventricular stiffness. BOTH –> diastolic dysfunction

END STAGE: LA dilation, LA contractile dysfunction, LV systolic dysfunction (EFFECTS = increased atrial pressures, CHF, LA thrombus formation)

Also dynamic LVOTO

Question 12

Define LVOTO

Answer 12

left ventricular outflow tract obstruction.

It describes the abnormal motion of the anterior mitral leaflet during systole (SAM)–> anterior leaflet moves towards OT during ejection –> OT obstruction and mitral regurgiatation –> worse with increased contractility, SNS stimulation or ventricular septal hypertrophy

Question 13

Pathological findings - HCM

Answer 13

LV hypertrophy may affect any part of LV
LA dilates when filling pressures increased
Myocardial infarction may occur, appear as localised wall thinning with hypomobility and scarring.

Question 14

Signalment - HCM

Answer 14

most common in young male adults
BUT all ages affected
Predisposition: maine coons, persians, ragdolls, cornish rexes and bengals. Most cats with HCM are moggies.

Question 15

Presenting signs - HCM - 4

Answer 15

Asymptomatic - majority
Respiratory distress (CHF) - minority
HL paralysis due to ATE - minority
Sudden death - unknown prevalence

Question 16

PE - HCM

Answer 16

** +/- variable intensity systolic murmur **
Prominent apical impulse
+/- gallop sounds (poor prognosis), arrhythmias
+/- tachypnoea, crackles
May be completely NORMAL

Question 17

Radiography - HCM

Answer 17

LV hypertrophy (long cardiac silhouette on lateral view)
Pulmonary oedema and/or pleural effusion (indicate CHF)

Question 18

Echocardiography - HCM

Answer 18

LV hypertrophy = diastolic septal or free wall thickness greater than or equal to 6mm (focal or generalised)

SAM of mitral valve causes DLVOTO and murmur

Question 19

Define SAM

Answer 19

Systolic anterior motion

Question 20

Define DLVOTO

Answer 20

Dynamic left ventricular outflow tract obstruction

Question 21

Prognosis - HCM

Answer 21

GOOD: short-medium term if LA normal size
POOR: if clinical signs present, LA enlargement, ATE

Question 22

Describe DCM

Answer 22

Dilation of all 4 chambers, with thinning of the ventricular walls and hypokinesis (systolic dysfunction). Historically associated with taurine deficiency. Now uncommon - most cats diagnosed have normal serum taurine levels.

Question 23

Clinical presentation - DCM

Answer 23

Middle-aged and older
Taurine-deficiency (if fed dog food)
Signs of output failure (hypotension, hypothermia, bradycardia)
Murmur quiet/absent but gallop often present
Thromboembolic disease - common

Question 24

Echocardiography - DCM - 3

Answer 24

Dilated, spherical LV
FS < 30%
LV end-systolic diameter >14mm

Question 25

Prognosis - DCM

Answer 25

Grave

Question 26

Outline RCM

Answer 26

Severely impaired diastolic filling Stiff LV Relatively normal LV dimensions and systolic function

Question 27

2 forms of RCM

Answer 27

Endomyocardial form - severe endomyocardial scarring such as a bridging scar across the LV. Myocardial form - normal LV dimensions, non-infiltrative, patchy thickening of the LV walls Severe atrial enlargement in both forms.

Question 28

Clinical presentation - RCM

Answer 28

``` older cats dyspnoea from pleural effusion common +/- low output signs +/- ATE arrhythmias common ```

Question 29

Echocardiography - RCM

Answer 29

severe bilateral enlargement Endomyocardial form of RCM is distinctive - endomyocardial scarring is readily imaged Myocardial form is more challenging

Question 30

Outline ARVC

Answer 30

Arrhythmogenic right ventricular cardiomyopathy Only recently characterised in cats - fibrofatty infiltration of the LV (scar tissue and adipose cells). Marked right heart enlargement May be asymptomatic May be syncopal in association with arrhythmias May have right-sided HF

Question 31

Echocardiography - ARVC

Answer 31

Severe RV and RA dilation | Tricuspid regurgitation usually present

Question 32

How is feline heart disease staged?

Answer 32

``` A = predisposed B1 = HCM, no CHF, normal LA B2 = HCM, no CHF, big LA C = HCM + CHF (past or present) D = HCM + CHF despite treatment ```

Question 33

Treatment options - A - cats at risk of HCM

Answer 33

MBPC mutation test available - maine coons and ragdolls only ANY cat could be at risk of HCM Echocardiography provides a definitive diagnosis Can consider NT-proBNP as initial step (>100picomols/litre)

Question 34

Treatment options - B - asymptomatic cats (HCM)

Answer 34

Some affected cats are at low risk for complications and don't need treatment (no gallop, no arrhythmia, normal LA size, low NT-porBNP/troponin-I) LVOTO - give a beta-blocker such as atenolol, may control the obstruction, currently no proven survival benefit, eases angina pain in humans High risk cats (LA dilation, systolic dysfuction, extreme hypertrophy) - consider anti-thrombotic to reduce risk of ATE (e.g. clopidogrel is better than aspirin)

Question 35

What should you be aware of in cats with acute life-threatening HF?

Answer 35

Do everything to cause the least stress possible - echo is less stressful than radiographs

Question 36

Treatment - C - past or present HF

Answer 36

IMPROVE OXYGENATION: Administer CO2 - oxygen cages practical SEDATION: since dyspnoeic cats often become very distressed (butophanol sometimes works well) IV FUROSEMIDE TO EFFECT: initial dose lower than dogs (2mg/kg) with subsequent doses (1-2mg/kg) every 60 mins until RR increases THORACOCENTESIS: generally with a butterfly cannula INCREASE CO: Difficult! If BP normal --> just treat congestive signs. AVOID IV fluids - won't increase CO and will worsen CHF.

Question 37

What are aims of home therapy for mild-moderate HF patients?

Answer 37

Eliminate abnormal fluid retention Modulate neurohormonal activation Optimise haemodynamic function Prevent thromboembolism

Question 38

How do you eliminate fluid retention

Answer 38

FUROSEMIDE (1-4mg/kg q12-24 hours PO) - use to effect - decrease once congestive signs clear ACEI - target dose of benazepril (0.5mg/kg q24 h)

Question 39

How can neurohormonal activation be modulated?

Answer 39

ACEI - benazepril preffered as licesned in cats - no evidence that abnormal hypertrophy is reveresed - Imidapril is difficult to pill cats with as it is a tasteless liquid.

Question 40

How can haemodynamic function be optimised?

Answer 40

Pimobendan if systolic dysfunction present | Otherwise v difficult to improve diastolic function

Question 41

Treatment - supraventricular tachycardia

Answer 41

Diltiazem

Question 42

What are the thoughts on using negative inotropes for dynamic obstruction?

Answer 42

Negative inotropes may decrease LVOTO gradients and beta-blockers are more effective at this than diltiazem in cats. However, negative inotropes may worsen CHF.

Question 43

Treatment - chronic refractory HF

Answer 43

If CHF persists despite therapy with furosemide and an ACEI, increase furosemide dose. If CHF continues desptite this, consider adding other diuretics: Spironolactone - not licensed in cats - dosing similar to dogs - 1mg/kg q24h PO. Facial skin lesions Thiazides - off label - combination used most commonly For cats with systolic dysfunction, pimobendan can be added. Not licensed and should NOT be used in cats with DLVOTO.

Question 44

When may ATE occur?

Answer 44

any cardiomyopathy particularly when the LA is dilated and poorly contractile A thrombus usually forms in the left auricle and when disolodge dis ejected into the systemic circulation only to lodge in a peripheral artery. The commonest site is the distal aorta, but other sites include subclavian artery or a cerebral, renal or mesenteric artery. CS: peracute and severe, with HL paresis and pain associated with obstruction of the terminal aorta. Rate of survival to discharge <45%. Underlying myocardial disease predisposing to TE cannot usually be resolved.

Question 45

Management - acute ATE - 5

Answer 45

Analgesia - methadone, fentanyl CRI Manage electrolyte and acid-base abnormalities Prevent thrombus extension - consider early use of clopidogrel Pulses often return in 72h, thorough limb use longer (physio) Thrombolysis can be associated with increased risk of reperfusion syndrome - therefore not usually attempted

Question 46

How can systemic TE be prevented? 4

Answer 46

Clopidogrel (superior to aspirin) Aspirin (high or low dose) Warfarin - not recommended LMW-heparins - not recommended, costly, SC injection