Feline cardiac disease Flashcards
What is HCM?
increased cardiac mass associated with left ventricular hypertrophy (LVH), which can affect different portions of the interventricular septum (IVS) and/ or left ventricular free wall (LVFW).
These lesions can be accompanied by left atrial dilation, aneurismal thinning of the left ventricle (LV) apex, right ventricular hypertrophy and right atrial enlargement.
Hypertrophic obstructive cardiomyopathy is a
form of HCM that is associated with dynamic outflow
obstruction
What is restrictive cardiomyopathy?
characterised by myocardial stiffness and diastolic dysfunction (restrictive pathophysiology)
The myocardial form of feline RCM is characterised by restrictive filling, a normal or mildly thickened LVFW or IVS, apparently preserved systolic function and severe atrial (often bi-atrial) enlargement
The endomyocardial form has extensive reparative fibrotic lesions, which affect primarily the LV and can present as large scars bridging the ventricular lumen.
What is DCM?
A severely dilated LV chamber and hypocontractile
myocardium
Mostly associated with taurine deficiency, although can be an end-stage form of another cardiac disease such as HCM, atrioventricular (AV) valvular dysplasia, ischaemic myocardial disease,
What is arrhythmogenic right ventricular cardiomyopathy
characterised by markedly enlarged right
chambers with a thin and hypokinetic myocardial free
wall, while the left chambers are minimally involved
May present with a range of arrythmias/ conduction disturbances
What is unclassified cardiomyopathy?
features that are not typical of any other commonly
recognised cardiomyopathy and are therefore described as ‘unclassified’, although they are likely to be an evolutionary phase of another recognised form of cardiomyopathy, (eg, an early or end-stage HCM or myocardial infarction) rather than an individual pathological entity
What is the typical signalment of cardiomyopathy cats?
males more than females
Some Maine coon, ragdoll, Norwegian forest, Persian and Burmese cats may be genetically predisposed, but majority are DSH cats
How does diastolic dysfunction occur?
reduced ventricular relaxation, which can be secondary to myocardial hypertrophy, interstitial fibrosis, loss of cellular architecture or a combination of these mechanisms. An increased heart rate may also exacerbate the diastolic dysfunction by reducing the time available for ventricular filling and for coronary bloodflow, which may lead to myocardial ischaemia. The diastolic dysfunction causes an increase in the LV and left atrium (LA) filling pressure, resulting in pulmonary venous hypertension and eventually pulmonary oedema and/or pleural effusion (congestive heart failure [CHF]).
Outline systolic dysfunction in HCM
Systolic impairment can appear in all forms of cardiomyopathy accompanied by ischaemia and replacement fibrosis, and systolic dysfunction will result in increased ventricular filling pressure and CHF.
What is the significance of ischaemia in HCM?
Ischaemia can be secondary to intramural coronary
arterial disease caused by myocardial hypertrophy,
and is frequently followed by malignant arrhythmias,
as well as systolic and diastolic impairment. The significant elevation of cardiac troponin-I (cTn-I) in cats
with HCM might indicate ongoing myocardial damage, possibly secondary to a concurrent myocardial
infarction
What is SAM?
n (SAM) of the mitral valve is a form of dynamic LV outflow obstruction that is present
in approximately half of feline HCM cases. It is characterised by an abrupt movement of the anterior leaflet
The dynamic obstruction caused by SAM has many
consequences:
■■ It reduces the stroke volume, hence the cardiac
output;
■■ It causes LV pressure overload, which may stimulate further cardiac hypertrophy;
■■ Mitral regurgitation may lead to atrial remodelling
(LA dilation);
■■ The continuous mechanical contact between the
septal mitral leaflet and the proximal IVS induces
fibrotic lesions (‘contact lesions’) that can affect the
normal function of both affected anatomical parts.
The blood flow turbulence originating during SAM
is also responsible for the presence of systolic murmurs
on auscultation in many cats with cardiomyopathy.
What is the px for cats with HCM?
a median
survival of 194 days in symptomatic cats versus 3617 in
the asymptomatic group (Payne and others 2010). In the same study, left atrial enlargement represents another negative prognostic variable. Other negative prognostic indicators include the presence of arrhythmias, gallop sounds, left atrial ‘smoke’ (spontaneous echocontrast), and reduced fractional shortening. Interestingly, the presence of SAM is associated with a longer survival time and this is possibly because it produces an audible heart murmur and allows earlier identification of the disease.
What do you need to exclude as a possible cause of HCM when you see it?
Hyperthyroidism Systemic hypertension Aortic stenosis Acromegaly Infiltrative disease Pseudohypertrophy
Which cats are predisposed to DCM
Abyssinians
Somali cats
What is a ddx for ARVC?
Tricuspid dysplasia
What is the prevalence of HCM
Approx 15% - not all have any issues though
