Feline cardiomyopathy

Question 1

What is the definition of “cardiomyopathy”?

Answer 1

abnormal myocardial function and/or structure in the absence of other cardiovascular disease sufficient to cause the observed myocardial changes

Question 2

When ist the term “cardiomyopathy phenotype” used?

Answer 2

When underlying disease is not yet diagnosed

Question 3

Name two causes of transient myocardial thickenning

Answer 3

1. systemic illness
2. stressful event

Question 4

Name tow possible underlying myocardial changes for TMT

Answer 4

1. Myocarditis
2. Myocardial edema

Question 5

What are the 5 phenotypic classes of feline cardiomyopathy?

Answer 5

1. HCM
2. DCM
3. RCM
4. Arrhythnogenic right ventricular Cardiomyopathy
5. Nonspecific cardiomyopathy

Question 6

What are the phenotypic characterstics of HCM?

Answer 6

Segmental or diffusely increased LV wall thickness

Question 7

What are the phenotypic characterstics of DCM?

Answer 7

1. Primary reduction in LV systolic function
2. normal or reduced LV wall thickness
3. eventual dilation of the LV and LA

Question 8

What are the two forms of RCM?

Answer 8

1. Endomyocardial RCM
2. Myocardial RCM

Question 9

What are the phenotypic characteristics of the two RCM types?

Answer 9

Endomyocardial = endocardial scar bridging the LV septum and free wall with associated LA or biatrial dilation

Myocardial = left of biatrial enlargement with normal LV dimensions

Question 10

What is the phenotypic characteristic of ARVC?

Answer 10

Severe dilation of the right heart with RV systolic dysfunction and myocardial thinning

Question 11

What is the phenotype of the nonspecific cardiomyopathy?

Answer 11

Any phenotype not fitting the characteristics of other phenotypic classifications

Question 12

What are possible clinical sequelae of HCM, DCM and RCM?

Answer 12

• FATE
• CHF
• Ventricular arrhythmias
• supraventricular arrhythmias

Question 13

In which feline phenotypic cardiomyopathy is a normal lifespan possible?

Answer 13

HCM

Question 14

What are possible clinical sequelae of ARVC in the cat?

Answer 14

• R-CHF
• Ventricular arrhythmias
• supraventricular arrhythmias
• PTE

Question 15

What phenotype is the most common phenotype of feline cardiomyopathies? What percentage is it?

Answer 15

HCM –> 14.7%

Question 16

Describe the 5 stages of feline cardiomyopathies based on the ACVIM consensus statement

Answer 16

A: prone to cardiomyopathies (family history of breeds like Maine Coon/Ragdoll)

B1: occult cardiomyopathy (normal or mildly enlarged LA) + low risk for CHF/ATE

B2: occult cardiomyopathy (moderate to severely enlarged LA) with higher risk for CHF/ATE

C: Overt cardiomyopathy - has experienced CHF/ATE

D: refractory CHF

Question 17

Name 8 underlying diseases contributing to the development of feline cardiomyopathy (mostly HCM)

Answer 17

1. Hypertension
2. Neoplastic myocardial infiltration
3. TMT
4. Inflammatory myocardial infiltration
5. Acromegaly
6. Hyperthyroidism –> HCM, RCM + nonspecific
7. Taurine deficiency
8. Chronic tachycardia

Question 18

What is the main gene described in the involvement of genetic HCM?

Answer 18

gene myosin binding protein C (MYBP3)

Question 19

What two areas of the cardiomyocyte can be effected in the development of a feline cardiomyopathy?

Answer 19

1. myosin (thick)
2. actin (thin)

–> causing hypercontractile cardiac sarcomere

Question 20

What are the two main effects of HCM on cardiac function?

Answer 20

1. LV hypercontractility
2. diastolic dysfunction

Question 21

Describe the pathophysiology of the development of HCM and how it results in congestion

Answer 21

LV hypercontractility –> LV hypertrophy –> energy depletion + altered Ca++ handling + mytochondrial dysfunction –> myocardial fibrosis + myofiber disarray –> LV stiffenning + diastolic dysfunction –> increased LV diastolic pressure –> increased LA volume + pressure –> increased pulmonary venous pressure –> increased hydrostatic pressure within venous capillary bed > oncotic pressure within vasculatury –> fluid leakage –> pulmonary edema and/or pleural/pericardial effusion

Question 22

What are 3 congestive consequences of HCM?

Answer 22

1. Pulmonary edema
2. Pleural effusion
3. Pericardial effusion

Question 23

What is the characteristic of end-stage HCM (burnout HCM)?

Answer 23

Overt reduction in systolic function

Question 24

What does the term DRVOTO describe?

Answer 24

Dynamic left ventricular outflow tract obstruction

Results from mid-ventricular hypertrophy

Question 25

What are two pathophysiologic mechanisms for SAM?

Answer 25

1. MV moves out of place during systole + makes contact with IVS --> impedes blood flow through LV outflow tract 2. Anterior displacement of anterior paipllary muslce due to myocardial hypertrophy --> elongated, anteriorly displaced MV leaflet grtd pushed and draged throughout systole --> displacement of valve + MR Greater degrees of LV hypertrophy with SAM (unclear if cause or result) Poor prognostic indicator in people (not been shown in cats)

Question 26

What is the risk (in %) of CHF with HCM?

Answer 26

24%

Question 27

What does SAM stand for?

Answer 27

Systolic anterior motion

Question 28

On what does the degree of SAM depend on?

Answer 28

1. preload 2. contractile state 3. heart rate

Question 29

What causes thrombus formation in feline cardiomyopathy?

Answer 29

1. LA dilation + reduced left auricular function --> blood stasis + endothelial damage 2. increased platelet activation

Question 30

What is the incidence of ATE in cats with HCM?

Answer 30

11%

Question 31

What is the most common location of ATE and what are its clinical signs?

Answer 31

aortic trifurcation --> variable degrees of pelvic limb paresis

Question 32

What are locations of ATE? List with most likely first

Answer 32

1. Aortic trifurcation 2. Brachial artery (R>L) 3. Mesenteric artery 4. Arteries within CNS

Question 33

What is the consequence of ATE that results in the clinical signs?

Answer 33

Ischemic injury leads to the release of vasoactive substances from activated platelets (e.g. serotonin) which causes collateral artery occlusion

Question 34

Name 3 histologic changes of HCM

Answer 34

1. Cardiomyocyte disarray 2. Arteriosclerosis 3. Fibrosis --> all contribute to arrhythmogenic potential --> sudden death

Question 35

Name are 4 histologic changes of RCM

Answer 35

1. Cardiomyocyte disarray 2. abnormal LV coronary arteriole 3. Myocardial fibrosis 4. Ischemia

Question 36

What are the changes in cardiac function observed with RCM?

Answer 36

Diastolic dysfunction without significant hypertrophy

Question 37

What is the disease outcome of RCM?

Answer 37

Similar to HCM

Question 38

What are the pathologial changes of feline DCM?

Answer 38

Primary reduction of myocardial contractility leading to myocardial fibrosis and increased LV end diastolic volume --> LA enlargement

Question 39

Name 3 possible consequences of feline DCM

Answer 39

1. Thromboembolism 2. Arrhythmias 3. CHF

Question 40

What are the pathological changes of feline ARVC?

Answer 40

Cardiomyocyte death + atrophy --> RH fibrofatty infiltration --> systolic RV dysfunction --> R-CHF

Question 41

Name 3 possible consequences of feline ARVC?

Answer 41

1. Ventricular + supraventroicular arrhythmias 2. intracardiac thrombus formation 3. PTE

Question 42

What is the most common presenting complaint in feline cardiomyopathies?

Answer 42

respiratory distress

Question 43

How can a heart murmur develop in cats without underlying heart disease?

Answer 43

Dynamic right ventricular outflow tract obstruction (e.g. anemia, fever, pregnancy...)

Question 44

Name 3 clinical findings that can make you suspicious for an underlying heart disease in the cat?

Answer 44

1. heart murmur (more common in cats with occult cardiomyopathy) 2. Gallop sounds (rare in normal cats) 3. Arrhythmias

Question 45

Name 6 clinical findings in cats with CHF

Answer 45

1. tachypnea/laboured breathing 2. pulmonary crackles 3. muffled heart/lung sounds 4. heart murmur (less likely to be appreciated once CHF developed) 5. Gallop 6. Arrhythmias

Question 46

What are 3 specific clinical findings that make CHF more likely than primary respiratory disease?

Answer 46

1. RR > 80/min 2. Hypothermia <37°C 3. HR > 200/min

Question 47

Name X clinical findings of ATE

Answer 47

1. variable degrees of paresis (uni/bilateral pelvic or unilateral thoracic R>L) 2. absent or attenuated arterial pulses 3. Cyanosis of distal extremity 4. relative poikilothermia of distal extremity 5. firm muscle groups 6. Pain

Question 48

What are possible signs of feline cardiomyopathy of radiographs?

Answer 48

1. Left auricular buldge on DV/VD 2. VHS > 9.3 in left lateral (highly suggestive of cardiomyopathy severe enough for CHF) BUT VHS < 8 --> unlikely to be CHF 3. Pulmonary edema 4. Distension of pulmonary arteries, veins or both 5. Pleural effusion

Question 49

What are radiographic changes of feline cardiogenic pulmonary edema?

Answer 49

1. patchy unstructured interstitial/alveolar pattern 2. peribronchiolar infiltrates (can have appearance of bronchial pattern)

Question 50

What is the gold standard for diagnosing feline cardiomyopathy?

Answer 50

Echocardiography

Question 51

What is the most important echocardiographic measure for guidance of therapy in felines cardiomyopathy?

Answer 51

LA size --> maximal dimension in long axis: 16.5mm

Question 52

What is the cut of for LA enlargement regarding LA:Ao in cats?

Answer 52

>1.5

Question 53

What is the sensitivitiy and specificit yof seeing > 3 B-lines in 1 site for CHF?

Answer 53

Sensitivity: 79% Specificity: 83%

Question 54

What is the LV %FS in feline cardiomyopathes?

Answer 54

Mostly normal: ≥ 40%

Question 55

Name 11 historical indications of echocardiography in the cat

Answer 55

1. Syncope 2. Seizure (in absence of other neurologic abnormalities) 3. Family history of cardiomyopathy 4. Weakness 5. Exercise intolerance 6. Intolerance to fluid therapy 7. Pedigree cat intended for breeding 8. Maine coon or ragdoll with MYBPC3 mutation 9. Endocrinopathy 10. positive heartworm status 11. FUO

Question 56

Name X physical examination findings indicative for echocardiography in the cat

Answer 56

1. abnormal cardial auscultation 2. tachypnea 3. pulmonary crackles 4. jugular venous distension or pulsation 5. ascites 6. hyperkinetic or hypokinetic femoral arterial pulse pressure 7. acute paralysis/paresis

Question 57

What are 3 indicatiosn for echocardiography in the cat > 9y old?

Answer 57

1. GA 2. Fluid therapy 3. Extended-release glucocorticoids

Question 58

How many cats (%) with systemic hypertension will have LV hypertrophy?

Answer 58

85%

Question 59

In what stage of feline cardiomyopathy can hypotension appear, why and how can this be managed?

Answer 59

end-stage cardiomyopathies with reduced systolic function --> inotropic support

Question 60

Name two cardiac biomarkers used in feline cardiomyopathy

Answer 60

1. NT-proBNP 2. cardiac TnI

Question 61

What are sensitivity and specificity of the POC ELISA for CHF in a respiratory distress setting?

Answer 61

Sensitivity: 93% Specificity: 72% --> quantitative test has better sensitivity for identifying subclinical cardiomyopathy than POC ELISA

Question 62

What is the cut-off value for cardiac TnI in cats when a feline cardiomyopathy is suspected?

Answer 62

> 0.7 ng/ml --> increased risk for cardiac death, independent of LA size

Question 63

What tests should be done to identiy potential contributors to a cardiomyopathy phenotype?

Answer 63

1. T4 2. BP 3. Plasma taruine levels --> History of diet (grain free? Boutique? 4. ILGF-1 (Acromegaly)

Question 64

Name the 3 corncerstones of management of feline cardiomyopathies

Answer 64

1. identification and treatment of underlying contributing diseases 2. monitoring for risk factors of disease complications 3. treating complications that occur (ATE, CHF, arrhythmias)

Question 65

Is DRVOTO associated with increased mortality or morbidity in cats with HCM?

Answer 65

No

Question 66

What drug can be used in cats with a feline cardiomyopathy B1 and what are 5 possible benefits? How does this treatment affeect survival?

Answer 66

Beta-blockers 1. reduced HR 2. Anti-arrhythmic effect 3. Prolongation of diastole --> improved coronary perfusion 4. Attentuation of SNS activity 5. Reduction of DRVOTO -->treatment with atenolol was not associated with longer survival (Schober et al. JVC 2013)

Question 67

Name 3 contraindications for starteing a beta-blocker in cats with feline cardiomyopathy withou consultation of a cardiologist

Answer 67

1. CHF 2. reduced systolic function 3. severe LA enlargement

Question 68

What treatments are recommended for cats with feline cardiomyopathy B2?

Answer 68

B2 --> at risk for FATE --> Clopidogrel

Question 69

Name 3 echocardiographic indications for starting clopidogrel in a cat with feline cardiomyopathy

Answer 69

1. moderate to severe LA dilation 2. reduced LA function (%FS and/or reduced auricular appendage velocity) 3. spontaneous echo contrast in LA

Question 70

How does clopidogre compare to aspirin in cats with feline cariomyopathy?

Answer 70

Clopidogrel superior to aspirin in preventing second thromboembolic events in cats who have experienced ATE

Question 71

What are 2 presumbed benefits of an ACE-inhibitor for the treatment of feline cardiomopathy (stage B2)?

Answer 71

1. diminishing upregulation of RAAS 2. safe drug

Question 72

What are possible medication options if SVT or VT is present in feline cardiomyopathy?

Answer 72

1. Atenolol (6.25mg/cat PO BID) or 2. Sotalol (10-20mg/cat PO BID) 3. Diltiazem (mainly SVTs like atrial fibrillation)

Question 73

Name 2 medications currently under investigation for the treatment of feline cardiomyopathy and their MOA

Answer 73

1. Ivabradine = funny channel inhibitor --> negative inotrope 2. MYK-461 = small molecule sarcomere inhibitor --> reduced force generation by hypercontractile sarcomeres

Question 74

Name 7 treatments you would instigate in feline CHF

Answer 74

1. Oxygen therapy 2. cardiac sparing sedatives (butorphanol, benzos) 3. limit stress 4. furosemide 1-2mg/kg IV (or IM) q1-4hr initially vs. CRI 5. +/- thoracocentesis 6. +/- pimobendan IV/PO if low CO 7. Clopidogrel 18.75mg/cat PO SID

Question 75

Name 3 indications and 1 contraindication for pimobendan therapy in feline CHF

Answer 75

1. Hypotension 2. Bradycardia 3. reduced systolic function --> all leading to low CO CI: loud heart murmur suggestive of dynamic LVOTO

Question 76

Name 2 treatments contraindicated in the acute feline CHF setting

Answer 76

2. fluid therapy 2. ACE-inhibitors

Question 77

What testing would you instigate in feline CHF?

Answer 77

1. renal values + electrolytes at baseline

Question 78

What would you monitor clinically in a cat where diuretic therapy was started?

Answer 78

hydration + BW (if > 10% loss of BW in 24hr --> Excessive diuresis --> if no clinical improvement consider other cause for respiratory distress)

Question 79

What did King et al JVIM 2019 show regarding the use of ACE-inhibitors in chronic CHF management?

Answer 79

randomized placebo-controlled: benazepril does not delay onset of recurrent CHF

Question 80

Name 3 proposed benefits of pimobendan in feline CHF?

Answer 80

1. improvement of LA function 2. possible improval of survival 3. possible lusitropic effect (not investigated in cats yet)

Question 81

What would you tell owners when discharging a cat that has been in CHF?

Answer 81

1. Monitor RR (<30/min) daily 2. return in 3-7d for clinical assessment of improval + renal values + electrolytes + evaluation of cardiologst (if not already evaluated in acute setting)

Question 82

How does the management of CHIEF D defer from CHIEF C in cats with feline cardiomyopathy?

Answer 82

1. Consider replacement of furosemide by torasemid 0.1-0.2mg/kg PO q12hr if patient decompensating despite high doses of furosemide (>6mg/kg/d PO) 2. Start pimobendan (if not already on it) 3. Consider spironolactone 1-2mg/kg PO q12-24hr 4. Monitor weight --> cardiac cachexia is associated with shorter ST

Question 83

What is the proposed benefit of spironolactone in CHIEF D management for feline cardiomyopathy?

Answer 83

= Aldosterone antagonist --> may block profibrotic effect through chronic RAAS activation Side effect: facial excoriation (rare)