Canine cardiomyopathies Flashcards
Types of cardiomyopathies in dogs. (6)
- Primary cardiomyopathies
– Dilated cardiomyopathy (DCM)
– Arrhythmogenic right ventricular cardiomyopathy
(ARVC)
– Hypertrophic cardiomyopathy (HCM) - Secondary
– Nutritional
– Myocarditis
– Hypothyroidism
Describe dilated cardiomyopathy.
DCM is a primary heart muscle disease involving reduction of systolic function. Its Definitive cause is unknown but its known to have a genetic predisposition, can be caused by nutrition, and infectious disease.
DCM vs. DCM-phenotype meaning a heart showing features of DCM (dilation and dysfunction) but without meeting full diagnostic criteria for DCM as a primary disease.
The “DCM-phenotype” may be seen in conditions where LV dilation and dysfunction are secondary to another disease, such as:
Hypertrophic cardiomyopathy (HCM) in its end-stage
Arrhythmogenic cardiomyopathy (ACM)
Myocarditis
Tachycardia-induced cardiomyopathy
Signalment in DCM.
Mostl Affects Large and medium sized Male dogs.
Very, very uncommon in small breed dogs but not impossible!
2 breeds that may see early/young-age DCM:
portugese water dogs
manchester terriers
Clinical presentation of occult phase in DCM. (2)
May have Arrhythmias, murmurs that can be caught at Screening (echocardiography, ECG, Holter).
Clinical presentation of symptomatic phase in DCM. (3)
- congestive heart failure
- syncope
- sudden death
Etiology of canine cardiomyopathies. (6)
Majority Idiopathic (so genetics related essentially because we don’t know the genes).
Taurine deficiency (e.g. American Cocker Spaniels and Atypical or mixed breeds)
Carnitine deficiency in e.g. Boxers but you can supplement this, its not dangerous to give extra carnitine.
Other dietary etiologies
– BEG (“Boutique, exotic, grain-free”) correlation found but still open as to how exactly.
Tachycardia induced
Toxic (doxorubicin a chemotherapy)
Pathophysiology in canine cardiomyopathies.
Reduction of systolic function means Reduction of cardiac output and lowered blood pressure.
Compensatory mechanisms include:
1. Reduction of parasympathetic tone
2. Increased sympathetic tone
3. Water retention
4. Myocardial Remodelling
CO=HR*SV
Taurine and other nutritional deficiencies & canine cardiomyopathies.
- Cocker spaniels predisposed (found to have Taurine plasma levels <50umol/mL)
- Golden retrievers, Newfoundlands too
- Dalmatians on u/d diet for urate stones
- Lamb and rice diets seem not to have sufficient taurine so can cause DCM.
Great danes and heart disease. (5)
- Prevalence 35%
- X-chromosome recessive suspected
- Autosomal dominant
- Atrial fibrillation and VPCs are common in occult phase
- VPC-s are common with DCM in general
Irish Wolfhounds and heart disease. (6)
- Prevalence 29%
- 56% males, 44% females
- Mean age at diagnosis: 4.4 +/-2 years
- Median survival after onset of CHF: 7.3 mths
- Median survival without CHF: 22-29 mths
- Some IWH-s have AF and never develop DCM
Boxer cardiomyopathy, ARVC.
Arrhythmogenic right ventricular cardiomyopathy (ARVC), is a genetic heart disease commonly affecting Boxers.
It is characterized by the replacement of normal heart muscle with fatty or fibrous tissue, primarily in the right ventricle, leading to arrhythmias, heart failure, or sudden death.
The condition is inherited in an autosomal dominant manner and often presents with symptoms such as exercise intolerance, syncope, or, in severe cases, congestive heart failure.
Treatment focuses on managing arrhythmias with antiarrhythmic medications like sotalol or mexiletine and addressing heart failure if present, but there is no definitive cure.
Doberman cardiomyopathy
- Occult phase
– Ventricular arrhythmias
– Often several years
– 1/3 die suddenly - DCM phenotype
– CHF and/or ascites
– 1/3 die suddenly - Prevalence: 45-63%
- Male dogs get earlier echo changes (DCM-phenotype).
- Females remain longer in VPC-s only.
Diagnostic work up for DCM type cases. (6)
- 5-minute ECG: even a single VPC is alarming
- Holter ECG: >50 (100) VPCs/24h
– Assess Frequency, complexity - Echocardiography
– M-mode
– 2D - Biomarkers
- Genetic tests
- Radiography
Tx of DCM/cardiomyopathies in dogs. (4)
- Occult phase
– Pimobendan
– ACEI? - CHF
– diuretics - Arrhythmias – treat?
– Fast atrial fibrillation (AF): digoxin, diltiazem (calcium channel stabilizer)
– Ventricular tachycardia: lidocaine!, sotalol, mexiletine, atenolol - Nutritional cardiomyopathy
– supplementation of taurine; carnitine?
– Avoidance of BEG (boutique, exotic, grain-free)
diltiazem
Diltiazem is a calcium channel blocker used in dogs to manage cardiomyopathy, particularly in cases involving hypertrophic or dilated cardiomyopathy with arrhythmias.
It works by reducing myocardial oxygen demand, slowing heart rate, and improving ventricular filling, making it useful for conditions like atrial fibrillation or supraventricular tachycardia.
It primarily works by inhibiting calcium influx into cardiac muscle and the sinoatrial (SA) and atrioventricular (AV) nodes. This leads to slowed conduction through the AV node, making it particularly useful in managing supraventricular arrhythmias, such as atrial fibrillation.
tx of fast atrial fibrillation in dogs
mexiletine
tx of ventricular tachycardia in dogs
Mexiletine is an oral class IB antiarrhythmic drug used in dogs to manage ventricular tachycardia (VT) and other ventricular arrhythmias, often in cases of dilated cardiomyopathy (DCM) or arrhythmogenic right ventricular cardiomyopathy (ARVC).
It works by blocking sodium channels, stabilizing cardiac cell membranes, and reducing abnormal ventricular excitability without significantly affecting atrioventricular (AV) conduction.
Mexiletine is often combined with beta-blockers (e.g., atenolol) or sotalol for better rhythm control. Dosing is tailored based on response and potential side effects, which may include gastrointestinal upset, ataxia, or lethargy. Regular ECG monitoring is essential to ensure efficacy and safety.
Prevention of DCM or related health crises. (3)
– Routine health checks
– Breeding programs
– Dietary aspects
