Feline cardiomyopathies Flashcards
Types of Feline cardiomyopathies. (5+1)
– Primary
* Hypertrophic (HCM)
* Restrictive (RCM)
* Dilated (DCM)
* Unclassified (FUCM = FelineUnclassifiedCardioMyopathy)
* Arrhythmogenic right ventricular (ARVC)
– Secondary
* Hyperthyroidism induced
Heterogeneous group of diseases that lead to thickening, enlargement or stiffening of heart muscle.
Prevalence of feline cardiomyopathies.
Fairly common, not unusual.
Principal cause of cardiovascular morbidity and mortality in cats.
Majority remain asymptomatic though.
Most common feline cardiomyopathy.
hypertrophic cardiomyopathy
Secondary feline cardiomyopathy is typically caused by
hyperthyroidism
Virchow’s triad.
3 factors need for thombus formation:
* endothelial damage
* blood stasis
* platelet activation
Why is thrombosis formation not seen in MMVD in dogs?
too much turbulence and dog platelets are less active than cats’
phenotypic diff. between HCM and RCM
no hypertrophy in RCM (restrictive), only ventricular wall stiffness increases.
Some say these aren’t even 2 separate diseases, maybe this is just a spectrum of the same disease. Perhaps RCM is advanced HCM.
back in the 80s-90s, feline DCM was found to be due to
taurine deficiency which is why all cat foods now contain taurine.
Main complications of heart disease in cats: (3)
- Congestive heart failure
- Arterial thromboembolism (FATE)
- Sudden death
Cat breed dispositions for cardiomyopathy. (6)
Maine Coon,
Ragdoll,
BSH,
Sphynx,
Persian,
Norwegian Forest Ccat
Some involved genes have been indentified.
Staging of feline cardiomyopathies.
A-D
A = predisposition (healthy but due to breed and/or familial history, very predisposed)
B = Subclinical
* B1 = Normal- mild atrial enlargement
* B2 = Moderate- severe atrial enlargement
C = Current or previous CHF/ATE
D = Refractory CHF
Prevalence, morbidity, mortality of HCM in cats.
Estimates vary depending on the population.
* 5-15% in general cat population
- Up to 30% in older cats
- CHF develops in 17…30% of cats with HCM
- FATE occurs in 3%
- 5-year cumulative mortality 23%
Non-cardiac causes of HCM. (5)
hyperthyroidism
super athlete
neoplasia (e.g. lymphoma, cardiac)
hypertension
renal failure
What exactly about hyperthyroidism predisposes or leads to HCM? (4)
Its not known with certainty but the following factors are believed to contribute:
* volume overloading
* increased sympathetic stim. as well as increased sensitivity to adrenaline
* hypertension
* direct effect of T4 on the myocardium
Sensitive tests are good for
Sensitive tests are good for SCREENING.
Sensitivity refers to the probability that the test is positive and the patient really has the disease.
If the SENSITIVE test is NEG, the disease is safely ruled out due to low false negatives. A highly sensitive test has fewer false negatives.
“SnNout” (SeNsitivity—Negative result rules OUT disease)
Why are highly specific tests good rule IN tests?
Specificity measures a test’s ability to correctly identify those without the disease (true negatives).
A test with 100% specificity means that all HEALTHY individuals test negative, and there are no false positives.
Highly specific tests are good for ruling IN a disease because they have a low false positive rate.
“SpPin” (SPecificity—Positive result rules IN disease)
Positive predictive value (PPV) =
Negative predictive value (NPV) =
Positive predictive value (PPV) is the probability that the POSITIVE test results correctly indicate the
presence of the disease.
* So a High PPV means that a positive result does in fact reliably indicate the presence of Dz.
Negative predictive value (NPV) is the probability that a NEGATIVE test result correctly indicates the
absence of the disease.
* So a high NPV means that a negative result reliably indicates the absence of Dz.
Decreased prevalence improves what value?
Increased prevalence improves…?
- Decreased prevalence improves the NPV.
- Increased prevalence improves the PPV.
Increased sensitivity improves…?
Decreased prevalence improves…?
- Increased sensitivity improves the predictive value of a negative test because it reduces the likelihood of false negatives.
A highly sensitive test rarely misses cases, meaning if the test is negative, it is very likely that the person does not have the disease.
- Increased specificity improves the predictive value of a positive test because it reduces the likelihood of false positives.
A highly specific test rarely misidentifies healthy individuals as diseased, meaning a positive result is very likely to be correct.
Early detection of heart disease in cats.
Otherwise asymptomatic cats may be found to have (3)
– Presence of a murmur
* 80% of cats with HCM have a murmur
* But also 30-45% of healthy cats have a murmur!
- Positive predictive value of a murmur is 18-43%. A lower PPV means that when a murmur is present, it does not always indicate heart disease.
- Negative predictive value 90-100% so if a cat does not have a murmur, there is a very high probability that it does not have heart disease.
– Gallop sound: present in 3-19% cats with preclinical HCM.
– Arrhythmia
A gallop sound is present in what percentage of cats with preclinical HCM?
present in 3-19% cats with preclinical HCM
Physical exam findings in cardiomyopathy cats. (6)
- Murmur, gallop sound, arrhythmias
- Dyspnoea
- Tachypnea
- Orthopnea
- Muffled heart sounds
- Thromboembolism
Radiography in feline cardiomyopathy. (4)
- Is insensitive in mild/moderate HCM.
- Severe atrial enlargement may be seen on xray but is not specific to the type of cardiomyopathy.
- Pulmonary oedema can be found.
- Risk of deterioration! Estimate value vs risk.
proBNP for occult heart disease
n-terminal pro B-type natriuretic peptide is a good rule-in test for occult heart disease:
over 100 pmol/L means heart disease is likely
proBNP for respiratory distress cases
the SNAP test is a good rule OUT test. If you’re wondering CHF vs resp. dz and you do the snap and get a neg. result, you can lean toward resp. dz.
Cardiac troponin I (“i”)
– Good rule-in test: if you get a pos. then you prob have myocardial damage but a neg. test doesn’t rule out heart issue so well.
– Does not specify the cause of damage
– Short half-life
Tx of asymptomatic HCM. (3)
- Limited evidence to back tx of asympptomatic HCM.
- Beta-blockers
– No survival benefit found
– May be useful in some cats with “angina pectoris” aka chest pain - Diltiazem (calcium channel blocker)
– No clear benefit
– Theory is that it causes reduction of myocardial oxygen consumption.
angina pectoris =
chest pain or pressure
Tx of congestive heart failure. (6)
Loop diuretics (furosemide, torasemide)
– Dose depends on severity of CHF.
– Mild: 1 mg/kg BID PO
– Acute/severe: 1-2 mg/kg IV q30…60 min
Monitor response by checking RR, repeat Xray &
Renal parameters, electrolytes.
Furosemide “resistance” can occur at which point resort to Sequential nephron blockade with thiazide (low dose).
ACE inhibitors
– Have Questionable efficacy
– Risk of hyperkalemia
– Risk of hypotension
Spironolactone
– No significant benefit
– Risk of severe skin lesions as side effect is sloughing.
Pimobendan
– Avoid in obstructive cardiomyopathy (loud murmur) – Not licenced in cats
Mötskula gives furo IM unless very severe dyspnea, he says IV can cause vomiting in cats due to sudden elctrolyte shifts.
Thiazide-like diuretics primarily act upon the distal convoluted tubule and secondarily upon the proximal tubule.
When in need of sequential blockade, whats the main risk?
very, very high risk of azotemia after adding thiazide for sequential blockade for furosemide resistance. start at a low dose siis and recheck renal parameters.
severe side effect of spironolactone sometimes seen in cats?
patchy facial skin sloughing
Tx of FATE. (6)
- ANALGESIA!!!
- Anxiolysis
- Oxygen
- Medical:
– Heparin (does not break down the thrombus tho)
– Thrombolytic agents? - NB! Reperfusion injury – hyperkalemia
- Prevention with:
– Clopidogrel
– Aspirin
clopidogrel
is an antiplatelet medicine.
binds specifically and irreversibly to platelet receptors, inhibiting platelet activation and aggregation.
can be sent home as an oral med for cats.
hyperkalemia in reperfusion injury due to
all the released K+ from broken down muscle cells
If you have a cat with severe cardiac changes you can prescribe
clopidogrel or aspirin to prophylactically treat for thombus formation.
