What You Need to Know
- Chronic Degenerative Valvular Disease (CDVD)/Myxomatous Mitral Valve Degeneration (MMVD), also known as endocardiosis, is a heart disease your dog can develop over time where heart valves become thickened and leaky, allowing blood to flow backward
- Your veterinarian typically first suspects this condition when they hear a heart murmur during a routine exam
- Treatment depends on the stage of disease: early stages may not require medication, while advanced stages can result in issues like congestive heart failure (fluid in the lungs secondary to poor cardiac function), which requires immediate therapy
Understanding Your Dog's Heart Condition
As some dogs age, one or more of the four valves in the heart becomes "leaky." A normal valve is thin and able to create a tight seal when in the close position, ensuring that blood flows only in the forward direction. With this disease, the valves become thickened and irregular, allowing blood to flow backward within the heart. This backward flow is referred to as valvular insufficiency or regurgitation.
CDVD/MMVD is an acquired heart disease, and is a genetic disorder with no known causative environmental factors. That is, it is not present at birth, but instead occurs as dogs age. While some breeds develop this condition at a relatively young age (e.g. Cavalier King Charles Spaniels), most dogs do so at middle age or later. This is the most common heart disease diagnosed in dogs, and can happen in any breed, but is more likely to occur in smaller breed dogs.
💙 Breed Considerations
Certain breeds, like Cavalier King Charles Spaniels, are predisposed to developing valve disease at younger ages. If your dog is a breed known for heart disease, regular cardiac monitoring is especially important.
How Will My Veterinarian Diagnose CDVD/MMVD?
The valvular insufficiency that occurs as a result of CDVD/MMVD is often first suspected based on detection of a heart murmur during routine physical examination. This is an abnormal "whooshing" sound associated with the normally crisp heart sounds, heard while listening to the heart with a stethoscope. The murmur is described according to its loudness and where it is best heard on the chest wall. These findings depend on which of the four valves in the heart are affected, and how much blood is consequently allowed to flow backward. All four valves of the heart can be affected, although the mitral valve is most commonly involved.
💡 About That Cough
If your dog has been coughing, it doesn't necessarily mean they're in congestive heart failure. While dogs can cough from their heart disease, coughing has been found to be an inconsistent and unreliable indicator of cardiac issues in canines, as there are many things that can potentially cause coughing in dogs.
Confirming the Diagnosis with an Echocardiogram
Definitive diagnosis of CDVD/MMVD requires an echocardiogram (ultrasound examination of the heart). Affected valves are typically seen to be thickened, so that when the leaflets of the valve meet to prevent backflow of blood, they do not form a perfect seal as they should. The result is valvular insufficiency (or regurgitation). This can be seen using an ultrasound tool called "color flow Doppler," which displays blood in different colors according to its direction and how smoothly it is flowing from one chamber of the heart to another. Measurement of the heart's chambers may reveal enlargement of one or more of them.
Additional Testing Your Dog May Need
Other diagnostic tests may be useful depending on the specific situation. Chest x-rays provide a "big picture" view of the heart and allow detection and monitoring of congestive heart failure if present. They can also be important in ruling out other causes of coughing and difficulty breathing. An electrocardiogram (EKG or ECG) is useful to confirm or rule out arrhythmias (abnormalities in cardiac rhythm) and to monitor their response to antiarrhythmic therapy. Measurement of blood pressure and certain kinds of blood work may also be valuable, depending on overall condition and medications being used.
Treatment Options for Your Dog
In the early stages of the disease, medications are often not required. Many dogs with this disease progress slowly and never end up needing therapy. If/when dogs develop enlargement of their heart secondary to their valve leak, this is the point when medications should be initiated. This is why regular monitoring is important. While there are no medications that can treat the valve thickening itself, there are drugs that can improve heart function in other ways. Pimobendan (Vetmedin) is the only drug that has been definitively shown to prolong survival and delay congestive heart failure for asymptomatic dogs with CDVD/MMVD. Other drugs, such as ACE inhibitors, can also be considered. ACE inhibitors cause blood vessels throughout the body to relax, creating more space within them for fluid. This reduces the workload placed on the heart and may delay the onset of congestive heart failure.
If Congestive Heart Failure Develops
If congestive heart failure is present or develops at some point after initial diagnosis, medical therapy is begun immediately. Long-term therapy for congestive heart failure includes the medication furosemide (often referred to by one of its brand names, Lasix or Salix) as well as Pimobendan/Vetmedin and other drugs like an ACE inhibitor. Lasix is a diuretic agent. It causes increased urination and so decreases fluid retention within the body, again reducing the workload on the heart. Other medications may be used as well, depending on the initial response to these two agents, the presence of arrhythmias, and the nature of the symptoms present.
🌟 Surgical Options
It is worth noting that definitive therapy for diseases causing valvular insufficiency, performed routinely in people, involves surgical repair of the affected valve using cardiac bypass. Although this is performed infrequently in dogs, largely due to financial reasons, it is performed at a few veterinary institutions throughout the world and is a potential topic for discussion. A newer technique, called TEER (Transcatheter Edge-To-Edge-Repair) or V-Clamp, is also being performed at some veterinary hospitals. This surgery entails a small device being attached to the mitral valve in order to reduce leaking.
What to Watch For: Monitoring Your Dog
Dogs with endocardiosis need ongoing monitoring to watch for progression of disease and development of heart failure. Regular veterinary checkups are essential, as your veterinarian will listen for changes in the heart murmur and watch for signs of heart enlargement or fluid buildup/congestive heart failure.
Signs That Your Dog May Need Immediate Care
Contact your veterinarian if you notice any of the following symptoms in your dog:
- Increased coughing, especially at night or when lying down
- Difficulty breathing or rapid breathing at rest
- Reduced energy or exercise intolerance
- Loss of appetite or weight loss
- Restlessness or difficulty settling down to sleep
- Weakness or collapse
These symptoms may indicate that congestive heart failure is developing or worsening and require prompt veterinary attention.
⚠️ When to Call Your Vet
If your dog shows difficulty breathing, severe coughing, or collapse, seek emergency veterinary care immediately. These signs may suggest congestive heart failure and require urgent treatment.
Download Our Valve Disease Management Guide
Get a printable resource with medication schedules, symptom tracking sheets, and guidelines for when to seek veterinary care.
Download PDF GuideLiving with Valve Disease: A Partnership in Care
Chronic Degenerative Valvular Disease is a progressive condition, but many dogs live comfortably for months to years after diagnosis with appropriate management. The key to success is regular monitoring, prompt treatment when heart failure develops, and close communication with your veterinary team. While there's no cure for CDVD/MMVD, medications can significantly improve quality and duration of life particularly if heart failure occurs. Some dogs may even be candidates for surgical valve repair at specialized centers. By staying alert to changes in your dog's breathing, energy level, and appetite, and by keeping up with veterinary checkups and prescribed medications, you're giving your dog the best chance at continued comfort and happiness.