8. Myocardial diseases in dogs and cats Flashcards
Myocardial diseases in dogs and cats?
Dilated Cardiomyopathy (DCM) ?
Dilated Cardiomyopathy (DCM)
Progressive loss of myocyte number & function; ↓ Contractility
Leads to eccentric hypertrophy (see previous topic)
Breed disposition: Doberman-pinscher; Great Dane; Irish
wolfhound; Poodle; New-foundland
Juvenile onset: Portuguese water dog
Dogs > Cat; Large breed > Small breed
PATHOGENESIS
Variety of causes: Idiopathic; Toxic; Viral; Nutritional; Genetic
Nutritional cause: Usually seen in cats with a taurine deficiency
CLINICAL SIGNS
May vary depending on the side of heart failure
Early signs: Murmur; Weak peripheral pulse; Exercise intolerance
Left-sided CHF (Usually predominant)
§ Dyspnoea
§ Pulmonary oedema → Cough
§ Weight loss
§ Cyanosis
§ Hydrothorax
Right-sided CHF
§ Ascites
§ Distended jugular vein
§ Subcutaneous oedema
§ ↑ Cardiac dullness
§ Weak pulse & heart beats
Left & Right-sided CHF: Pleural effusion
Cats: Respiratory signs; Pulmonary oedema; Pleural effusion
Auscultation: Systolic heart murmur; Arrhythmia with associated
pulse deficit
DIAGNOSIS
Echocardiography
§ LA/LV dilation → Enlargement & thin walls
§ RA/RV dilation may or may not be present
§ Mitral/tricuspid valve regurgitation → Papillary
displacement
§ Eccentric hypertrophy
§ Poor contractility → Prolonged end-point septal separation
§ ↓ Fractional shortening (FS)
ECG
Detection of arrhythmias; May show premature complexes,
ventricular tachycardia (VT), atrial fibrillation (AF) and evidence of
cardiac enlargement
§ Sinus tachycardia; Supraventricular tachycardia
§ Wide/tall QRS-complexes; Wide P-waves
§ Atrial/ventricular premature contractions
§ Atrial fibrillation
Radiography: Only used to see secondary alterations e.g.
cardiomegaly
TREATMENT
§ ↓ Oedema/Effusion: Diuretics e.g Furosemide
§ Improve contractility: Pimobendan
§ Reduce adverse effects of angiotensin II: ACE Inhibitor
Hypertrophic cardiomyopathy?
Hypertrophic Cardiomyopathy (HCM)
Concentric left ventricular hypertrophy
Predisposition: Cats > Dogs (small dogs); Male > Female
Maine Coon; Ragdoll cats
This section will focus on hypertrophic cardiomyopathy in cats only
CLINICAL SIGNS
Can often be sudden
Tiredness; Exercise intolerance; Asphyxia; Cyanosis; Collapse;
Ascites
CSx associated with Left-sided HF: Pulmonary oedema; Pleural
effusion → Tachypnoea; Dyspnoea (coughing is atypical)
Auscultation: Soft prominent systolic murmur; Gallop sounds;
Dynamic murmur; Arrhythmia with pulse deficit; Tachycardia
DIAGNOSIS
Echocardiography
§ LV wall thickening
§ Papillary muscle hypertrophy
§ Thickened LV septum
§ ↓ LV end-systolic diameter → ↓ Systolic function
§ Dilated LA; Narrowed LV
ECG: Ø Use in cats
Radiology: LA enlargement; Sometimes LV enlargement
Blood pressure: Good for DDx
TREATMENT
No causative treatment available
Controlling the CSx of CHF
§ Acute: Furosemide; Oxygen therapy; ACE inhibitor
Symptomatic treatment
§ Oxygen therapy
§ Thoracocentesis (in cases of pleural effusion)
§ Furosemide (in cases of pleural effusion)
Restrictive cardiomyopathy?
Restrictive Cardiomyopathy (RCM)
Unknown cause; Potential diastolic dysfunction
Present in cats (though rare)
LV = Normal; LA = Enlarged
PATHOGENESIS
Stiff, non-compliant LV due to ↑ collagen → ↑ Diastolic pressure →
↑ LA size → LS-HF → Thrombus formation (similar to HCM)
Different to HCM in that HCM has hypertrophy of muscle, whereas
restrictive cardiomyopathy is collagen
DIAGNOSIS
Echocardiography
Doppler imaging is needed
CLINICAL SIGNS – SEE HCM
TREATMENT – SEE HCM
Arrhythmogenic right ventricular cardiomyopathy?
Arrhythmogenic Right Ventricular Cardiomyopathy
(ARVC)
“Boxer cardiomyopathy”; Fatty infiltration of the right ventricular
myocardium
PATHOGENESIS
Non-sustained VT → Ø Cerebral perfusion for >6-8 sec → Syncope
Some develop DCM → HF
CLINICAL SIGNS
CSx associated with LS-HF; Sudden death
DIAGNOSIS
Arrhythmia: Ventricular premature complexes (VPCs); Ventricular
Extrasystole (VES)
Holter monitor: >100-300 VPCs are considered diagnostic
TREATMENT
Ø DCM: Sotalol; Mexiletine + Atenolol
Antiarrhythmic treatment
Unclassified Cardiomyopathies?
Unclassified Cardiomyopathies
MYOCARDITIS
Infectious disease
§ Virus: Parvovirus; Distemper virus
§ Bacteria: Borrelia spp.; Rickettsia spp.
§ Fungi: Aspergillus spp.; Cryptococcus spp.
§ Protozoa: Toxoplasma spp.; Neospora spp.
NEOPLASIA
§ Hemangiosarcoma
§ Chemodectoma
§ Lymphosarcoma
METABOLIC DISORDERS
§ Hyperthyroidism; Hypothyroidism
§ Electrolyte imbalance
§ Uraemia
§ Glycogen storage diseases
TOXICOSIS
§ Heavy metals; CO2; Ethanol
§ Drug toxicosis: Doxorubicin; Catecholamines; Digoxin;
Monensin
NUTRITIONAL DEFICIENCY
§ Selenium
§ Vit. E
PHYSICAL CAUSES
§ Hypothermia
§ Trauma
§ Hypoxia
§ Electric shock
