Understanding Myxomatous Mitral Valve Disease in Dogs
If your dog has been diagnosed with a heart murmur, there’s a good chance it could be due to myxomatous mitral valve disease (MMVD)—the most common type of acquired heart disease in adult dogs. This condition is especially prevalent in small-breed dogs like Cavalier King Charles Spaniels, Dachshunds, Chihuahuas, and Toy Poodles.
What is MMVD?
The mitral valve lies between the left atrium and left ventricle of your dog’s heart. Over time, this valve can become thickened and irregular, causing it to leak. As a result, blood flows backward into the atrium during each heartbeat, creating a characteristic heart murmur that your vet may hear during a routine wellness exam.
What symptoms might I notice?
In the early stages of MMVD, most dogs show no outward symptoms. That’s why annual wellness visits at your vet clinic in Fargo ND are so important—many murmurs are first caught during a routine exam. As the disease progresses, you might begin to notice:
Coughing (especially at night or after activity)
Decreased stamina or tiring more easily on walks
Labored or rapid breathing
Loss of appetite or weight loss
Collapse or fainting (in advanced cases)
What will my TRVH vet look for on imaging?
At Two Rivers Vet Hospital, our veterinarians use radiographs (X-rays) to assess heart size and shape. Dogs with advancing MMVD often have left atrial enlargement, and you may hear us mention changes like a “backward bowing” of the trachea due to heart enlargement. We may also recommend an echocardiogram (ultrasound of the heart) for more detailed information or collaboration with a cardiologist.
What does treatment look like?
For dogs with mild MMVD and no symptoms, we may simply monitor the condition with regular exams and chest X-rays every 6–12 months. Once symptoms appear or X-rays show enlargement, medications like pimobendan and diuretics can dramatically improve quality of life and slow progression. Your TRVH vet will customize a treatment plan and monitor kidney function, electrolytes, and respiratory rate closely throughout therapy.
Stay proactive—catch it early
With early detection and proper management, many dogs with MMVD live for years after diagnosis. If your dog has been diagnosed with a heart murmur, or you're noticing changes in energy or breathing, don’t wait—reach out to Two Rivers Vet Hospital today. We’re here to help!
