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J. Häggström1
1Swedish University of Agriculural Sciences, Department of Clinical Sciences, Uppsala, Sweden
New concepts in the medical therapy of heart disease in dogs
J. Häggström
Professor, DVM, PhD, DECVIM-CA (Cardiology)
Department of Clinical Sciences, Faculty of Veterinary Medicine and Animal Science
Swedish University of Agricultural Sciences, Uppsala, Sweden
Myxomatous mitral valve disease (MMVD) and dilated cardiomyopathy (DCM) in dogs may lead to signs of congestive heart failure (CHF). During the last 20 years, an important paradigm shift has occurred in the demand for data to support our clinical decisions in dogs with heart disease. Today, several drugs have in clinical
trials been shown to improve outcome in small animal CHF patients, as evidenced by improved quality of life and increased survival times. This presentation reviews current treatment alternatives from asymptomatic to progressed stages, associated with severe clinical signs of CHF, in dogs with MMVD or DCM.
Treatment by disease stage
Dogs with heart disease may progress into CHF at different rates. The American College of Veterinary Internal Medicine (ACVIM) has proposed a new scheme of classification of heart failure, with classes ranging from A to D. Although this scheme was intended for dogs with MMVD, it may, to some extent, be applicable to dogs with DCM.
Risk populations (Class A)
No therapy is indicated at this stage, but, screening for heart disease is typically conducted in this category of dogs.
Asymptomatic heart disease (Class B)
Because of important clinical implications for prognosis and treatment, Stage B is subdivided into Class B1 and B2. Class B1 refers to asymptomatic dogs with no signs of cardiomegaly. Class B2 refers to asymptomatic dogs that have signs of cardiomegaly.
Myxomatous mitral valve disease
The ACE-inhibitors were the first studied pharmacological modality in class B MMVD dogs. The SVEP and the VetProof studies investigated the effects of enalapril compared to placebo in delaying the onset of CHF in dogs with MMVD. The two trials showed a similar outcome with a non-significant difference in the time from initiation of therapy until diagnosed CHF. Recently, the results of a trial called the EPIC trial was published. The trial included 360 dogs with cardiomegaly secondary to MMVD, but no signs of CHF, that were randomly allocated to pimobendan or placebo. The primary endpoint was diagnosed CHF or cardiac related death/euthanasia. The main result was that the median time to the primary endpoint was 1228 days (95% CI 856 – NA) in the pimobendan group and 766 days (95% CI 667-875) in the placebo group (P = 0.0038). Adverse events were not different between treatment groups. Dogs in the pimobendan group lived longer (P = 0.012). The EPIC trial is a landmark trial in small animal cardiovascular medicine.
Dilated cardiomyopathy
The PROTECT Study was published in 2012 and comprised Doberman Pinscher dogs with asymptomatic (stage B) DCM. Pimobendan prolonged the time to the onset of CHF or sudden death (Median 718 days, versus the placebo group 441 days, P = 0.0088), and increased survival time (Median 623 days versus the placebo group 466 days, P = .034). Although the PROTECT study
was restricted to Doberman Pinscher dogs, the results speak in favor of treating dogs of other breeds with DCM in class B with pimobendan. Finally, there is evidence that some Cocker spaniels develop a form of DCM responsive to Taurine and Carnitine supplementation.
Symptomatic heart disease (Class C)
Class C of the ACVIM classification, denotes dogs which have developed signs of CHF. Dogs with severe signs of CHF require hospitalization for stabilization with the goal of chronic management at home. Treatment of dogs with DCM in acute CHF is comparably similar to strategies outlined for MMVD dogs, with a few exceptions. Dogs with DCM in acute CHF are more are likely to benefit more from inotropic support and more likely in need of antiarrhythmics. Very few studies are available on efficacy of medical treatments for acute CHF and treatment modalities are often based on clinical experience.
Acute treatment of CHF in dogs with MMVD or DCM include: Furosemide (IV/IM/SC), Pimobendan, oxygen supplementation, and centesis if needed. The following drugs may be considered: ACE-inhibitors, nitroglycerin ointment, dobutamine, hydralazine.
An Urban Experience

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