The heart is the motor of the blood circulation. It is a powerful muscle with four cavities forming the two antechambers and the right and left ventricles. Chambers and antechambers are separated by heart valves. The heart is surrounded by the pericardium. All blood vessels leading away from the heart are called arteries. In the veins then that blood flows back to the heart, to which the organism has already extracted oxygen for the metabolism. From the pulmonary artery, it is transported to the lungs, where it takes in oxygen again, then flows back to the heart and from there via the main artery (aorta) supplies the entire body with oxygen. During the course of life it comes to signs of wear and one day the point is reached that the heart can no longer function properly and complaints occur. If there is no timely treatment, a path of suffering begins for the affected dog that ends with too early death. However, as there are very good methods for the early detection of heart disease in veterinary medicine and modern therapies for extending life with a good quality of life are available, “my PETER” has the head of the cardiology department at Vetmeduni Vienna, Dr. med. Sabine Giant, interviewed on this topic.
Question: Unfortunately, heart disease in older dogs is very common. What is the cause?
Dr. Giant: Degenerative changes are usually responsible for heart problems in older dogs. These are mainly due to the mitral valve, which separates the left antechamber from the left ventricle. The flap mobility changes, the mitral valve thickens and shortens. The result is that they can not close properly, so it comes to valve insufficiency. This leads to a backwater of the blood in the lungs. The tricuspid valve, which lies between the right antechamber and the right ventricle, is therefore not so often affected because the right heart has to work much less in comparison to the left one.
Trust and bonding
Dr. Giant: If master or mistress then retrieves the four-legged treasure from the frolicsome game, and the puppy happily jumps towards its owners, then this is not only one of the most beautiful experiences of success, but above all the result of a work in whose center are the concepts Trust and bonding stand. Getting to know each other and exploring new situations, the common existence of the many small “big” challenges in this dog kindergarten create trust! Trust the puppy develops towards its owner, who leads him safely to the goal in unknown and unusual situations. Trust, which ultimately creates the optimal bond with which the dog later unconditionally follows its owner in a variety of everyday situations, because he has long since learned that he can rely on his human being. So even “Easy” knows since puppy days that the “ride” on a wobbly rocking horse is a matter of course, and has learned that even unpaved moving surfaces are not a reason to panic or stress, but that they always and in can rely on any situation on mum. From the puppy’s point of view, these are exciting adventures and great challenges that need to be shared with the people at their side. As a matter of course, the young dogs learn to fix their concentration on their people despite distraction, to keep an eye on their human partners, and to pay full attention to the managerial (feed) hand.
Are all dogs equally affected by heart disease or are there differences, e.g. in terms of race?
Dr. Giants: Degenerative heart valve disease is particularly common in small dogs, whereas large breeds are rarely affected. Why this is so, you do not know exactly, but it is believed that it may be because they generally have stronger connective tissue – and the heart valves are indeed made of connective tissue. For this theory also speaks that particularly often affected small-growth breeds, such as. Pug, bulldog, King Charles spaniel or dachshund, naturally tend to have some connective tissue weakness. However, how early the degenerative changes on the heart begin depends on the sex: Male animals fall ill earlier than female. For example, male King Charles Spaniels are often heart disease at the age of five.
How do dog owners notice that something is wrong with their four-legged friend’s heart?
Dr. Giant: In the initial stage, the pet owners often do not notice anything, because the dog does not show any symptoms. The vet usually discovers a heart murmur as part of a vaccination or check-up. At the second, already advanced, stage, the dog owner notices that the animal quickly fatigues when loaded, e.g. longer walks or dog sports can not be sustained. Some dog owners then simply ascribe this low stress to age and neglect to visit the vet. For others, the limited resilience is the occasion to have the dog examined Only in the third, already advanced stage show clear symptoms on the heart disease: The dogs cough, have no appetite, are listless to apathetic and not resilient. Circulatory collapse and short-term unconsciousness to the point of powerlessness occur.
What kind of examinations are necessary to make an accurate diagnosis?
Dr. Giant: In the first stage, although the heart murmur is heard, but in the X-ray is still no change detectable. For this reason, an ultrasound examination of the heart should absolutely be carried out, since it is already possible to determine in the ultrasound at this early stage in which state the heart valves are; whether deposits are present, whether even a flap incident exists and whether the holding apparatus of the valves is already damaged. In the second stage derailment of a regulatory system of the organism, which normally regulates the electrolyte and water balance. An active ingredient in this regulatory system, namely aldosterone, is now produced in excess and promotes the transformation of the heart muscle into connective tissue. This means a loss of elasticity of the heart, the heart becomes stiff, so to speak – it can not expand and contract enough; the heart function is impaired. Aldosterone in excess is therefore partly responsible for the progression of heart disease. The extent of the damage is again clarified with ultrasound, but even an X-ray can show something at this stage. Without therapy, the connective tissue transformation of the heart muscle progresses and finally the heart can no longer compensate and the third stage begins. The significantly enlarged heart is now clearly visible on the x-ray. But even at this stage can not be dispensed with a study with ultrasound. For a precise differentiation of the already existing damage is possible, so that in the treatment of each patient can be treated individually and also can be clarified whether any other causes are responsible for the pathological conditions, such. in small dogs a collapse of the trachea. The third stage of heart failure leads untreated to death very quickly. For further refinement of the diagnosis and the additional exclusion of cardiac arrhythmias, the electrocardiogram (ECG) is also used in all stages.
How can the progression of the disease be delayed and what treatment options are there?
Dr. Giants: In the first stage, no special cardiac therapy is needed yet. The dog should move normally, best to do endurance training – e.g. longer walks. As a result, the blood vessels are trained, which can only be beneficial for later stages of heart failure. You should weigh the dog regularly to avoid overweight. A gross mistake would be to start already with a low-salt diet. This would cause a shift in the electrolyte balance of the organism, thereby boosting the production of aldosterone, which in turn would accelerate the connective tissue transformation of the heart muscle. A low-salt diet should be started only in the second stage. From the second stage, it makes sense to reduce the blood pressure with so-called ACE inhibitors, such as Prilenal tablets for dogs, and thus to facilitate the heart’s work. Aldosterone blockers (Prilactone tablets for dogs) are now also available for dogs in order to prevent the transformation of the heart muscle into connective tissue. The active ingredient of these tablets has been used in human medicine for a long time with great success, but the special preparation for dogs is new and only available in Austria since this year. It also has a slightly dehydrating and vasodilating effect. For older males, who often suffer from prostate enlargement, Prilactone tablets have an additional benefit – they make the prostate smaller. In the third stage of the disease, stronger dehydrating agents, antihypertensive ACE inhibitors and agents that strengthen the heart muscle, e.g. As digitalis or pimobendan used. And continue to use aldosterone blockers (Prilactone tablets for Hunde), as these significantly extend the survival time.
Is there also the possibility that one can stop heart therapy again?
Dr. Giant: No, this possibility does not exist. Since healing is ruled out, every cardiac therapy lasts lifelong; one can only slow the progression of the disease and improve the animal’s quality of life.
In humans, diseased heart valves are operated, why not with the dog?
Dr. Giants: In the US and Japan, such operations are also performed on dogs. But in Europe, the replacement of diseased heart valves in dogs will be possible in five to ten years. Minimally invasive via a cardiac catheter without having to cut open the heart. One will not have to fall back on valve replacement for humans, since an artificial heart valve was developed especially for the dog.