The heart consists of 4 chambers, 2 atria and 2 ventricles, with the atrioventricular valves ensuring the blood flows from the atria to the ventricles when the heart is beating. A defect or weakness in the mitral valve or left atrioventricular valve allows some blood to move back into the left atrium, known as mitral regurgitation. This means the heart is less efficient at pumping blood through the body.
Mitral valve insuffiency is the most common of the acquired cardiac diseases in older dogs, affecting over 1/3 of dogs older than 10 years. However, in certain breeds, mitral valve insufficiency develops at a younger age, due to an inherited predisposition for the disorder.
The first signal that a dog might have Mitral Valve Disease is the development of a heart murmur. However, a dog with a heart murmur may live a full life span, depending up the progression of the disease in that particular dog. Some dogs that have developed heart murmurs at young ages have lived to the average lifespan of that breed. A veterinarian while listening to a dog's heart may hear a heart murmur on the left side. (Please note there are other causes for heart murmurs, to diagnose MVD it will depend upon where the regurgitation is heard) The veterinarian will then grade the murmur for severity from Grade 1 (mild) to Grade 6 (severe) and depending upon the grade will advise proper treatment.
Treatment will depend upon the grade of the murmur and any clinical signs your dog may be showing. During the early stages of the disease, though a systolic murmur of grade 1-2 is heard there are usually no clinical signs. As the disease progresses, the murmur will become more audible, the dog may become intolerant of exercise, respiratory rate will increase and finally as fluid begins to accumulate in the lungs coughing and laboured breath develops.
Many dogs live for years with a low grade murmur and treatment consists of dietary changes such as low sodium foods. Some breeders recommend that any dog diagnosed with a heart murmur is put on Co-enzyme Q10. This is a natural medication that may be helpful in treating the disease. While no studies have been done with this medication in dogs, there have been considerable studies in humans and the evidence is pointing to great success in treatment of cardiac disease with its use. Co-enzyme Q10 is an over the counter product and can be bought at virtually any health food store.
As the disease progresses and clinical signs appear such as coughing and laboured breathing medications such as vasodilators and diuretics will be considered.
Implication for Owner
Some dogs do develop a murmur which is the early sign of MVD, however, if the progression of the disease is slow, they may live out long lives without further symptoms or requiring medication. In many cases, a dog will not need heart medication or monitoring until late in life.
Implication for breeders
At present the mode of inheritance is unknown for MVD, though it is suspected to be polygenetic (several genes involved) and multifactorial (environment, food, weight). In other words there is a genetic predisposition for the disease but other unknown factors will go into why one dog is affected and at what age and another dog, even a littermate, is not affected at all.
At the moment the most commonly used test available to breeders is annual auscultation (listening to the heart with a stethoscope) by either a veterinarian or preferably a cardiologist. One problem with this test is that it only tells a breeder that at the time the test was performed the dog did not have a heart murmur. This does not mean that the dog will not develop MVD at any point in time nor does it mean that the dog does not carry the genes which might produce MVD. Only a definitive DNA test, which is not available at present, would be able to tell if a dog was clear of MVD.
Another important factor in Mitral Valve Disease is the rate of progression of the heart murmur and this is why breeders should continue to monitor the heart on an annual basis.
Pulmonic Stenosis is the third most common form of canine heart disease and has been reported in the Cesky Terrier. It can be accompanied by additional heart defects and can range in severity from severe breathlessness and the liklihood of a very short life to being mild enough to cause little apparent problem for the dog.
“Pulmonic stenosis” refers to a “stenosis” or constriction of the pulmonic heart valve through which blood must pass on its way from the heart to the lung.
What is pulmonic stenosis?
As part of normal circulation in the body, the right side of the heart (the right ventricle) pumps blood to the lungs to receive oxygen. The oxygenated blood goes back to the left side of the heart from which it is pumped out to the rest of the body.
Blood flows from the right ventricle of the heart through the pulmonic valve into the pulmonary artery and thence to the lungs. With pulmonic stenosis, there is partial obstruction of normal blood flow, most commonly due to a malformation of the pulmonic valve ("pulmonic valve dysplasia") but the abnormality may be immediately above or below the valve as well.
The effect of this partial obstruction is to force the heart to work harder to pump blood to the lungs. The extent to which a dog will be affected depends on the degree of narrowing (stenosis) of the valve area. With severe stenosis the dog will likely develop congestive heart failure due to the increased workload of the heart.
Regular heart testing is advisable