What it is
The mitral valve is a two-flap door between the two chambers on the left side of the heart. With each heartbeat it should close tightly so that blood moves forward into the body. When the flaps or the cords that hold them are malformed, the door either leaks and lets blood slip back, or opens too narrowly and makes the heart push harder. Either way, the left side of the heart takes on extra work and may stretch.
The defect is present from birth and is thought to be inherited. A mild defect may cause no signs at all, while a severe one can show in a young dog that never quite keeps up with its littermates.
Your vet can tell you how much exercise suits your dog. At home, it helps to learn how your dog breathes at rest: count its breaths while it sleeps, so you can spot a change early. Hot days and hard play are best kept in check.
Signs you may notice
- Tires sooner than other dogs
- Fast breathing at rest
- Coughing
- Slow growth in a puppy
- Fainting or collapse
A vet may hear a heart murmur at a puppy check while the puppy itself seems healthy. With a more severe defect the dog tires sooner, breathes with effort, coughs or grows poorly, and suddenly laboured breathing or fainting is a sign to see a vet immediately.
When to see a vet
Book a visit if your dog tires more easily, coughs or breathes faster than before while resting. Sudden laboured breathing, blue gums or fainting needs a vet immediately.
This is general information, not veterinary advice. For your own dog's health, tests and treatment, see a vet.