Resources for Dog Owners

Congestive Heart Failure in Dogs

1. What is Myxomatous Mitral Valve Disease?

Myxomatous Mitral Valve Disease (MMVD), also known as "endocardiosis" and "chronic valvular insufficiency" is an initially asymptomatic and slowly progressive condition that leads to congestive heart failure [1]. MMVD accounts for around 75% of all cases of congestive heart failure in dogs¹.

2. What are the symptoms of congestive heart failure caused by MMVD?

While MMVD itself is an asymptomatic condition, some of the symptoms of congestive heart failure arising from MMVD include¹:

• Coughing
• Reduced tolerance for exercise
• Anxiety and restlessness during the night
• Laboured breathing

Some or all of the symptoms above may appear, and all impact on the dog’s quality of life.¹ In severe and advanced cases of congestive heart failure, there may also be fainting and collapse.¹

3. How is congestive heart failure due to MMVD diagnosed?

The diagnosis of MMVD is usually via the detection of a heart murmur during routine veterinary check-ups using a stethoscope. Although stethoscope findings may be suggestive of MMVD, a veterinarian may also rely on the following tests to confirm the presence of congestive heart failure:

• Radiographs (x-rays): to check for any enlargement of the heart or fluid accumulation in the lungs¹
• Echocardiography (ultrasound): to show any thickening of the heart valve edges¹, or enlargement of the chambers of the heart.

By contrast, electrocardiographs (which measure electrical activity in the heart) are of limited use in the diagnosis of MMVD.

4. How is congestive heart failure caused by MMVD normally treated?

Treatment of MMVD-based congestive heart failure generally takes place when clear symptoms of heart failure emerge¹, and is tailored for the individual canine patient and their owner.¹ Since surgery to prevent further deterioration is rarely possible in canine patients, management of heart failure seeks to improve quality of life and extend life expectancy¹, usually through daily medication.

5. What are the other causes of congestive heart failure in dogs?

There are other less common forms of heart disease which can cause heart failure in dogs.

Dilated cardiomyopathy (DCM) is a disease which affects the myocardium. In DCM, the myocardium (heart muscle) becomes thin and weak, which means that the heart's contractions become weaker and the supply of blood to the body is compromised. Unlike MMVD this is often a rapidly progressive disease which affects large and medium-sized dogs such as the Doberman pinscher, Great Dane and English Cocker Spaniel.¹ There are a number of treatments licensed for dogs with DCM, with early diagnosis and intervention offering the best prognosis.[2]

6. Is there a cure for congestive heart failure in dogs?

Currently there is no cure for congestive heart failure in dogs caused by MMVD¹. Treatments are available, however, to help dogs live a longer and more comfortable life. The success of any treatment, however, depends on various factors, including early detection and diagnosis.

About QUEST

1. What is QUEST?

The QUEST trial is the largest clinical study of its kind ever to be conducted amongst dogs with congestive heart failure due to Myxomatous Mitral Valve Disease (MMVD) – also known as "endocardiosis" and "chronic valvular insufficiency". QUEST stands for "Quality of Life and Extension of Survival Time", and is an international, multi-centre clinical trial comparing the effects on survival and quality of life of pimobendan (Vetmedin®) and benazepril hydrochloride (an ACE-inhibitor treatment) in dogs with congestive heart failure due to MMVD. 260 dogs were enrolled into the study across 11 countries with the trial spanning three years.

2. What are the aims of QUEST?

The primary aim of QUEST is to assess the effect of pimobendan therapy on survival time, in comparison with benazepril hydrochloride, in dogs with congestive heart failure due to MMVD. The secondary aim is to assess the effect of pimobendan, in comparison with benazepril hydrochloride, on the quality of life in dogs with congestive heart failure due to MMVD.

3. How was the QUEST trial designed?

QUEST is a randomised, positive-controlled, multi-centre trial conducted at 28 sites across Australia, Canada and Europe. Patients were recruited over a two year period and randomly allocated to either the pimobendan or benazepril hydrochloride treatment group, each group consisting of 130 dogs. The trial spanned three years and followed dogs to death, euthanasia or treatment failure leading to withdrawal from the trial.

4. What are the results from QUEST?

The results of the trial will be published in the September/October 2008 edition of the Journal of Veterinary Internal Medicine.

About Pimobendan (Vetmedin®)

This information is intended for owners of dogs who have been prescribed pimobendan (Vetmedin®) by their veterinarian. Vetmedin is a prescription-only medicine, and is only available with a prescription from your veterinarian. Any question about your pet should be directed to your veterinarian.

1. What is Vetmedin?

Vetmedin contains pimobendan, and is the first dual acting inodilator licensed in veterinary medicine, a breakthrough treatment for congestive heart failure resulting from Myxomatous Mitral Valve Disease (MMVD) or Dilated Cardiomyopathy (DCM) in dogs. An inodilator is an agent with both inotropic (affecting the force of muscular contractions) and vasodilator (causing dilation of the blood vessels) effects. Vetmedin may be given alone, or alongside other medication.

2. How does Vetmedin work?

Vetmedin works by opening up the blood vessels taking blood away from the heart, thereby reducing resistance in the circulation and the work the heart has to do to pump blood around the body. At the same time, Vetmedin opens up the blood vessels that return blood to the heart, reducing pressure on the heart.

3. How is Vetmedin different from other treatments?

Not only does Vetmedin open up the blood vessels, reducing resistance in the circulation and workload on the heart, it also differs from other commonly used heart drugs by helping the heart to pump more efficiently without increased energy expenditure.

4. How is Vetmedin given?

Vetmedin is given orally to dogs in either a chewable tablet or capsule presentation, twice daily.

5. How fast does Vetmedin work?

Pet owners should begin to see an improvement in their dog within a week [3], although it is important to bear in mind that the severity of heart failure will vary from dog to dog, and this will affect how well the dog responds to treatment. It is also possible that the initial improvement witnessed after one week may be followed by further improvements in following weeks.

[1] Häggstrom J, Kvart C and Pedersen H. ”Acquired valvular heart disease” in Ettinger SJ, Feldman EC (Eds). Textbook of veterinary internal medicine: diseases of the dog and cat. 2005 (6th edition)

[2] Meurs KA. “Primary myocardial disease in the dog” in Ettinger SJ, Feldman EC (Eds). Textbook of veterinary internal medicine: diseases of the dog and cat. 2005 (6th edition)

[3] Lombard C, Jöns O, Bussadori C. Clinical Efficacy of Pimobendan Versus Benazepril for the Treatment of Acquired Atrioventricular Valvular Disease in Dogs. J Am Anim Hosp Assoc. 2006; 42: 249-261.