10: Canine Cardiomyopathies

Arrhythmogenic right ventricular cardiomyopathy (ARVC)

Fatty deposits in RV ± LV muscle cells that cause ventricular arrhythmias

ARVC is a common cause of what

Sudden death

Categories/progression of ARVC

• Asymptomatic with ventricular arrhythmias

• Normal heart size and function but with syncope from ventricular arrhythmias

• DCM like → CHF

How is ARVC fundamentally different than myocarditis

ARVC is not inflammatory, it is caused by fatty infiltrates

Primary demographic for ARVC

5-7 year old boxers, rare in other breeds

Why is ARVC commonly overlooked

It causes arrhythmias with no structural changes in the beginning

Why do dogs with ARVC experience weakness, collapse, and syncope

Ventricular arrhythmias causing decreased perfusion

Why is diagnosis of ARVC so expensive

You need to rule out other diseases that cause ventricular arrhythmias

Diagnostics for ARVC

• Bloodwork: full, genetic testing, cardiac biomarkers

• Imaging: abdominal US, chest rads, echo

• Holter monitor/ECG/Telemetry

Mainstay of ARVC diagnosis

24 hour holter monitor

Recommendation for screening boxers for ARVC, especially if intending to breed

Annual holter monitor screening starting at 3 years old

How do we evaluate efficacy for ARVC treatment

Looking for at least an 80% reduction in ventricular arrhythmias

Types of arrhythmias characteristic of ARVC

• Single VPCs

• Couplets

• Ventricular bigeminy

• Runs of vTach

Finding on a holter monitor that is categorized as likely having ARVC

>100 VPCs in 24 hours

Radiographic findings associated with ARVC

• May be normal

• Lateral: loss of caudal waist, backpack, dorsal trachea

• Interstitial to alveolar perihilar pulmonary pattern

• Pulmonary venous congestion

• Increased VHS

T/F: boxers with the identified genetic defect will develop ARVC

Nope

T/F: cardiac biomarkers are useful for ARVC prognosis

Nope

ARVC treatment

• Anti-arrhythmic (sotalol or mexiletine)

• Positive inotrope (pimobendan)

• CHF management: diuretics, ACE inhibitors

Last resort treatment for refractory ARVC

Synchronized electrical cardioversion

ARVC prognosis

Can do well if there is no cardiac enlargement, poor prognosis if they develop DCM

Prevalence of ischemic heart disease in dogs

Very rare

Type of coronary artery disease that is more common in dogs

Non-atherosclerosis narrowing

Tachycardia-induced cardiomyopathy

Rapid, uncontrolled tachycardia causing myocardial dysfunction and activation of neurohormonal pathways → CHF

Prevalence of HCM in dogs

Rare, think cats