Feline Cardiomyopathies Flashcards
Discuss myocardial disease in the cat?
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
What is the definition of hypertrophic cardiomyopathy?
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
How is hypertrophic cardiomyopathy diagnosed?
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
Discuss hypertrophic cardiomyopathy?
- 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
What are the two clinical forms of hypertrophic cardiomyopathy?
Two clinical forms:
- Obstructive
- Non obstructive
Discus HCM obstructive form?
- 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
Describe systolic anterior motion of the Mitral valve?
What are the typical features of hypertrophic cardiomyopathy?
Typical features of feline form
Animal model of human disease
- Disproportionate hypertrophy of the septum
- Myofiberdisarray or malalignment
- Arteriosclerosis “small vessel disease”
Discuss hypertrophic cardiomyopathy?
- 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.
What is the clinical presentation of hypertrophic cardiomyopathy?
- 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
Discuss the general history of a hypertrophic cardiomyopathy cat?
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
Discuss a general clinical exam with regards to cardiovascular system?
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
How to perform cardiac auscultation?
- 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
Hypertrophic cardiomyopathy auscultatory findings?
- 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
Compare normal heart sounds and gallop sounds?
Discuss electrocardiography with regards to HCM?
- 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
Echo findings in HCM?
- 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)
What can be seen here?
Typically HCM cat free wall is about 1cm thick
What can be seen here?
IVS measurement a little over what it should be
- Enlarged
What can be seen here?
- LA thick/papillary muscles
- anterior mitral leaflet being sucked into outflow track
Discuss papillary muscles in HCM?
- Hyperechoic
- Hypertrophied
- Irregular endomyocardial border
- Thick myocardium, irregular hyperechoic pappilary muscles
- Variable echogenecity. Bright white areas assume is fibrosis.
Look at these hypertrophic obstructive cardiomyopathy?
What can be seen here?
SAM (Systolic anterior motion of the mitral valve)
AMVL being sucked into base of aorta causing an obstruction
What can be seen here in M Mode?
What can be seen here?
Dynamic left ventricular outflow tract obstruction
Discuss dynamic right ventricular outflow tract obstruction?
- 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
What is this?
Dynamic right ventricular outflow tract obstruction
What can be seen here?
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.
What can be seen here?
LPLA (left parasternal long axis)
- Smoke
- Slow blood swirling around in LA
Discuss thoracic radiography?
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
What can be seen here?
- 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.
What can be seen with feline HCM?
Atria get big=classic valentines heart as ventricles remain same size
Look at these images of left atrial enlargement and right atrial enlargement?
Discuss restraint for radiography?
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
Discuss pleural effusion in cats with HCM?
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
List other forms of cardiomyopathy?
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!
Discuss restrictive cardiomyopathy?
- Unknown aetiology probably multifactorial as there is range of pathological findings
- Could be end stage of other disease processes
What are the two forms of restrictive cardiomyopathy?
2 Forms
- Endomyocardial (fibrosis tends to affect the endomyocardium)
- Myocardial
What is the pathophysiology of restrictive cardiomyopathy?
- 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
What can be seen here?
Endomyocardial Restrictive CardioMyopathy
Discuss dilated cardiomyopathy?
- 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
Discuss features of Dilated cardiomyopathy?
- 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)
Discuss cardiomyopathy complications?
- Recurrent Pleural effusion
- Refractory heart failure
- Thromboembolic disease
- Sudden death
Discuss thromboembolic disease?
- 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
What is the pathophysiology of thromboembolic disease?
- 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!
What does a clinical exam of a thromboembolic disease yield?
- 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
How is thromboembolic disease diagnosed?
- Cardiac evaluation
- Clinical pathology
- Renal function, muscle enzymes
- Measure blood flow with Doppler
- Ultrasound terminal aorta
What is the treatment for thromboembolic disease?
- 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?
Discuss outcome of thromboembolic disease treatment?
- 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!
