Myocardial disease in small animals Flashcards
what is myocardial disease
weakness or thickening of the heart muscle
What are the four types of primary myocardial diseases
dilated cardiomyopathy (DCM)
Arrhythmogenic right ventricular cardiomyopathy (ARVC)-
Hypertrophic cardiomyopathy (most common in cats)
Restrictive cardiomyopathy (common in cats
List 3 secondary causes of myocardial disease
Infective myocarditis
deficiency diseases
toxic causes
Describe dilated cardiomyopathy (DCM)
characteristics by impaired myocardial contractility
left ventricle becomes weakened and enlarged, and is unable to pump blood efficiently throughout the body
DCM is an end stage of many cardiac diseases
What is the most common type of myocardial disease in dogs
dilated cardiomyopathy
What is the predisposition for dilated cardiomyopathy
BIG DOGS
doberman, newfoundland, IWH, st Bernards, Labradors, Great Dane, GSD
Cocker spaniels
Usually dogs over 12kg
usually middle aged dogs
What are the clinical signs of dilated cardiomyopathy
Occult phase- non-symptomatic - can last weeks- years
symptomatic phase= syncope, weight loss, sudden death, soft murmur, atrial fibrillation, if right side affected will see ascities
what is atrial fibrillation
quivering or irregular heartbeat, usually rapid
what is the common history of a dog with DCM
exercise intolerance
recent weight loss
inappetence/ anorexia
cough
What will you observe on a clinical exam of a dog with dilated cardiomyopathy?
Tachycardia +/- arrythmias (atrial fibrillation, Ventricular premature complexes, Ventricular tachycardia)
Pulse defecits
LCHF
Galloping sounds
Soft murmurs
What will you see on a clinical exam of a dog with DCM if there is forward failure?
Pale mucous membranes
sluggish CRT
cold extremities
THIS IS A BAD SIGNS
How would you diagnose DCM
Echocardiograph (often definitive diagnosis) + doppler
Electrocardiograph
Radiography- confirms CHF
24hr Holter monitor- more for screening
What will you see on an echocardiography of a dog with DCM?
Left atrial and left ventricle enlargement with normal or occasionally thinly-walled dilated ventricles.
Rounded apex - reduced index of sphericity.
Hypokinetic (Large, round, poorly contractile) left ventricle.
Massive left atrial dilatation is often seen in Irish Wolfhound.
What will you see in an M-mode echocardiography of a dog with DCM
increased E point to septal separation if left dilation
What do you tend to see on a radiograph of a dog with DCM
gross generalised cardiomegaly
left atrial and ventricular enlargement
pulmonary venous congestion and pulmonary oedema
pleural effusion
What do you tend to see on ECG of a dog with DCM
Findings are very variable from normal to wide +/- tall complexes (occasionally small complexes).
*Many dogs will present with atrial fibrillation
*If in CHF the ventricular rate maybe very rapid
* Rate control is the key
Why would you use a holter monitor in patients with cardiomyopathies?
- To monitor for heart rate control
- Unexplained syncope or collapse
- Arrhythmias
4 .Monitoring therapy
How would you treat dilated cardiomyopathy
Diuretics
ACE inhibitors
Beta blockers (carvedilol, metoprolol, bisoprolol)
Inotropes (pimobendan)- to improve contractility
Limit salt and fluid intake
What is arrhythmogenic right ventricular cardiomyopathy (ARVC)?
A disease in which the heart muscles atrophy and are replaced by fibrous, fatty tissue.
rhythm disturbance caused by the cardiac muscle in the right ventricle
Commonly affects boxers
What are the three stages of arrythmic right ventricular cardiomyopathy (ARVC)?
1 - Asymptomatic with ventricular arrhythmias
2 - Symptomatic with normal heart size and LV function but the dogs are syncope / weak from ventricular arrythmias.
3 - Congestive heart failure: poor myocardial function and ventricular arrhythmias
What are the clinical signs of Arrythmic Right Ventricular Cardiomyopathy
Supra-ventricular arrhythmias
Ventricular arrythmias
Syncope
Death
How would you investigate a suspected ARVC?
ARVC is a diagnosis of exclusion:
Holter monitor is necessary.
The identification of a severe arrhythmia in the absence of other underlying disease, especially in the presence of clinical signs (Type II dogs) can make for a straightforward diagnosis.
How would you treat ARVC
treat any heart failure
anti-arrhythmic medication–> soltalol (beta blocker- commonly used)
What is the most common myocardial disease of cats
hypertrophic cardiomyopathy (HCM)
What is hypertrophic cardiomyopathy
Inappropriate myocardial hypertrophy of a non-dilated left ventricle, occurring in the absence of an identifiable stimulus
how do you diagnose hypertrophic cardiomyopathy
is a diagnosis of exclusion- need to make sure there isn’t another cause e.g. hyperthyroidism
what are the 2 clinical forms of hypertrophic cardiomyopathy
obstructive and non-obstructive
treated in the same way
what is the signalment of hypertrophic cardiomyopathy
maine coons
ragdolls
rare in dogs
what is restrictive cardiomyopathy
build up of fibrosis in the ventricles
atrial enlargement due to poor ventricular filling and regurgitation
how do cats with cats with cardiomyopathies generally present
often present in heart failure
Range from asymptomatic cat with a heart murmur (are rare in cats) to recumbent, cold dyspnoeic cat via congestive cardiac failure
what generally causes feline dilated cardiomyopathy
taurine deficiency
taurine levels in commercial diets has been increased so rarer now
what must you not give a hypertrophic cardiomyopathy cat
pimobendan- as increases the contractility - making the already thickened heart work even harder
which side is affected in DCM
left usually but can also be the right
what are the 2 main types of DCM
narrow myocardial cells
OR
myofibre degeneration
what are the 2 phases of DCM
occult phase and symptomatic phase
what type of arrythmias do many DCM dogs have
ventricular arrythmias
what is a holter monitor
a portable electrocardiograph that is worn by an ambulatory patient to continuously monitor the heart rates and rhythms over a 24-hour period
how can doxorubicin affect the heart
it can lead to cardiotoxicity
name two nutrients that can lead to secondary myocardial disease if deficient
L-carnitine
taurine
List 5 types of myocardial disease in cats
hypertrophic cardiomyopathy
restrictive cardiomyopathy
dilated cardiomyopathy
arrythmogenic right ventricular cardiomyopathy
feline unclassified cardiomyopathy
what are 4 things that can lead to concentric hypertophy (not HCM)
aortic stenosis
systemic hypertension
metabolic disorders
renal disease and associated hypertension
Describe obstructive HCM
blood can’t get out of the aorta due to a thickened septum, mitral valve has flopped into the aorta due to pressure and this has become obstructive
what happens to the atria in HCM
They enlarge due to the inability to move all the blood into the ventricles
what is the difference between HCM and RCM
in HCM, the walls are thickened. In RCM, the walls are normal size but the constriction is bad
what are the 2 forms of RCM
endomyocardial and myocardial
what can be seen on radiography of a feline HCM
pleural effusion
pulmonary oedema
cardiomegaly and venous congestion
can dogs get HCM
yes but it is rare
