Page 191 - Cote clinical veterinary advisor dogs and cats 4th

78 Arrhythmogenic Right Ventricular Cardiomyopathy, Dog

typically positive in lead II, consistent with should be based on the severity of the • Dogs with CHF should be treated with
arrhythmia.
a right-ventricular origin. • Ideally, treatment should be based on Holter standard CHF therapy, including pimoben-
VetBooks.ir monitor) is recommended in animals without results; however, dogs with clinical signs that enzyme (ACE) inhibitor, and spironolactone
dan, furosemide, angiotensin-converting
• A 24-hour ambulatory ECG (Holter
have frequent ventricular arrhythmias on
(pp. 408 and 409).
malignant arrhythmias (animals requiring
baseline ECG should be treated immediately.
immediate treatment based on initial ECG).
• Thoracic radiographs are usually normal but • In general, treatment indications include the Drug Interactions
may show LV enlargement with possible signs following: Antiarrhythmic drugs carry proarrhythmic
of left/biventricular CHF if the patient has ○ Clinical signs (e.g., syncopal dogs) with risks, particularly when used in combination.
type III disease. Thoracic radiographs may ventricular arrhythmias or those demon- When possible, reevaluation of Holter monitor-
be useful to rule out structural heart disease strating hemodynamic compromise ing is indicated 2-4 weeks after initiation of
as a source of ventricular arrhythmias. ○ Ventricular tachycardia on Holter or therapy.
• Echocardiogram baseline ECG
○ Echocardiogram is generally normal in ○ R on T complexes, particularly if frequent Possible Complications
types I and II, although prolonged or in ventricular runs Due to the potential for antiarrhythmic drugs
tachycardia can cause transient systolic ○ Frequent multiform VPCs to be proarrhythmic, patients may rarely
dysfunction from myocardial stunning. • Goals of treatment develop worsening clinical signs, including more
○ LV and/or right ventricular dilation with ○ Reduced frequency of clinical signs related frequent or severe syncopal episodes and sudden
persistent systolic dysfunction despite to the arrhythmia death. This underscores the importance of
tachyarrhythmia control is consistent with ○ Decreased arrhythmia complexity, includ- monitoring antiarrhythmic therapy.
type III ARVC (DCM phenotype). ing fewer R on T complexes, fewer ven-
• CBC, chemistry, and urinalysis are generally tricular couplets/triplets/runs, elimination Recommended Monitoring
normal but may be useful to rule out meta- of multiform complexes, and slower rates • Holter monitors are used to assess arrhythmia
bolic- or electrolyte-related causes of ven- of ventricular arrhythmias frequency and severity and to judge response
tricular arrhythmias. ○ Reduction of the absolute number of to therapy. Frequency of monitoring depends
ventricular arrhythmias by > 85% on on severity of disease.
Advanced or Confirmatory Testing subsequent 24-hour Holter monitoring ○ Type I dogs that are not receiving treat-
• The genetic test for the striatin mutation reports ment should receive annual Holter
can be helpful for supporting a diagnosis of monitoring.
ARVC and may be helpful in providing Acute General Treatment ○ Type II dogs and type I dogs that are
prognostic information. • Dogs with R on T ventricular complexes, receiving treatment should be monitored
○ Animals that test positive homozygous for frequent couplets/triplets or ventricular at least annually by Holter monitors, but
the striatin mutation are more likely to tachycardia runs should be treated emergently more frequent monitoring may be indi-
be affected by type III disease; monitoring with lidocaine at a 2 mg/kg IV dose; this cated by clinical severity.
with annual Holter and echocardiogram bolus may be repeated up to 4 times, with • Annual echocardiogram should be used to
is recommended. These animals also more 3-5 minutes between boluses, or until the monitor for development of type III disease,
commonly demonstrate severe ventricular patient shows signs of nausea/vomiting (the which can develop as a progression of type
arrhythmias, and genetic testing may help first sign of toxicity). I or II disease. This is of particular concern
guide reevaluation schedules and influence • Initial boluses should be followed by a in dogs that are homozygous for the striatin
the choice and dose of antiarrhythmic lidocaine continuous rate infusion (CRI) at mutation.
therapies. 25-80 mcg/kg/min, titrated to effect and ○ Monitoring for CHF in type III dogs
○ Animals that test heterozygous positive reduced if signs of toxicity occur (nausea/ should include evaluation of periodic
may or may not demonstrate signs of the vomiting or neurologic signs). thoracic radiographs (for pulmonary
disease and should be monitored annually • Begin concurrent oral therapy (see below). edema) assessment for cavitary fluid
with Holter and/or echocardiogram after (ascites/pleural effusion), blood pressure
the age of 3 years. Chronic Treatment measurement, and renal function monitor-
○ Boxer dogs without the mutation should • Sotalol 1.5-3 mg/kg PO q 12h and/or ing in patients receiving ACE inhibitor
still be screened by Holter because some mexiletine 5-6 mg/kg PO q 8h or diuretic therapy.
dogs with ARVC have been identified that ○ Typically begin with sotalol monotherapy ○ Owners should be trained to monitor
do not test positive for the striatin (low side effect profile, q 12h administra- resting respiratory rate at home because
mutation. tion). Mexiletine is more likely to cause trending increases in respiratory rate or
• Cardiac troponin I may be supportive of gastrointestinal (GI) side effects, but persistent elevations > 35 breaths per
and correlate with severity of disease but is combination therapy is occasionally minute while sleeping indicate possible
not sensitive or specific for diagnosis of the necessary and more effective than either development of CHF.
ARVC. drug alone.
• Postmortem histopathology demonstrates • Atenolol 1-1.5 mg/kg PO q 12h may also PROGNOSIS & OUTCOME
myocytolysis with fibrofatty infiltration be used if arrhythmia control is not attained
in the right ventricle (and/or the left with sotalol or mexiletine. This medication • Dogs are at risk of sudden cardiac death.
ventricle). The degree of myocytolysis and should not be used in a patient with CHF • Types I and II ARVC patients have a similar
fibrofatty infiltration is related to disease or severe systolic dysfunction. survival to non-ARVC boxers, with a
severity. • Amiodarone is not commonly used reported median survival time of 11 years.
due to high side effect profile, but it is However, successful treatment results in
TREATMENT occasionally necessary to treat refractory reduced clinical signs in affected dogs (e.g.,
arrhythmias. collapse, syncope).
Treatment Overview • Fish oil (780 mg EPA and 497 mg DHA) • Type III ARVC patients have a worse progno-
• Treatment is not necessary for all dogs with PO q 24h as an adjunct to sotalol/mexiletine sis and greater risk for sudden death. Average
ventricular arrhythmias secondary to sus- has been shown to decrease the number of survival time after a diagnosis of concurrent
pected ARVC, and the decision to treat daily VPCs. CHF is approximately 6-9 months.

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