Whether and what kind of therapy is suitable for a pulmonary or aortic stenosis varies depending on the respective severity of the disease. Correspondingly, it is first of all important to determine the maximum blood flow velocity (Vmax) measured via a cardiac ultrasonic doppler examination.
The severity of pulmonary stenosis is divided into three stages:
In the case of a slight pulmonary stenosis (Vmax to 3.5 m/s), there is also a cardiac murmur, but not a thickening of the heart muscle. Consequently, no symptoms will occur in the affected dog. Even without therapy, dogs with a mild pulmonary stenosis show a normal resilience as well as a normal life expectancy. However, due to the hereditary nature of pulmonary stenoses, a dog with a low degree of severity should also be excluded from breeding.
Even in moderate pulmonary stenosis (Vmax to 4.5 m/s), the affected dogs don’t show any symptoms in most cases and have a favorable prognosis even without therapy in normal cases. But this applies only as long as there is no additional leakage of the tricuspid valve. In this case, a backflow can occur in the body's circulation and consequently oedema in the chest or abdomen. If these complications occur, dehydrating and circulatory supportive medication must be given, the oedema may be punctured, if appropriate, and a ballooning (see later) of the bottleneck may be performed.
Only in the case of a high-grade pulmonary stenosis (Vmax of more than 4.5 m/s) does thickening occur, resulting in an under-supply of the heart muscle, which frequently leads to cardiac arrhythmias. Dogs suffering from high-grade pulmonary stenosis should be treated with beta-blockers in order to reduce the risk of cardiac arrhythmia and, on the other hand, to counteract cardiac remodeling. In addition, ballooning is recommended in most cases.
A pulmonary ballooning is a minimally invasive catheter intervention, in which a small balloon is introduced into the affected bottleneck via a catheter and unfolded there. Depending on the initial severity of the pulmonary stenosis and the potential changes already occurring, the disease can be reduced to a low to moderate degree of severity by this method and the prognosis for the affected dog can be significantly improved.
The severity of a subaortic stenosis is divided into three stages:
In the case of a slight subaortic stenosis (Vmax to 3.5 m/s), there is also a heart murmur but not a thickening of the heart muscle. Consequently, no symptoms will occur in the affected dog. Even without therapy, dogs with a low-grade aortic stenosis show a normal resilience as well as a normal life expectancy.
Even in a moderate subaortic stenosis (Vmax to 4.5 m/s), the affected dogs do not show any symptoms in most cases and have a favorable prognosis even without therapy in normal cases. However, this is only as long as there is no additional leakage of the mitral valve. In that case, a backflow into the pulmonary circulation and consequently oedema in the lung can occur. If these complications occur, dehydrating and circulatory supportive drugs must be given.
Only in the case of a high-grade subaortic stenosis (Vmax of more than 4.5 m/s) does thickening occur, resulting in an under-supply of the heart muscle, which frequently leads to cardiac arrhythmias. Statistically two out of three dogs with high grade subaortic stenosis are already dying within the first three years of life.
In the case of aortic stenosis, surgical/catheter-based surgery is only indicated in very rare cases, since such an intervention usually has no prognostic and therapeutic advantage but presents a relatively high risk (for example, an inflammatory change in the aortic valve). For sub-aortic stenosis, the method of ballooning is entirely unsuitable, and thus only open-heart surgery using a heart-lung machine would be considered-but the prognosis for such a highly invasive operation is very poor.
Dogs suffering from a high grade (sub-)aortic stenosis are treated with medicines that improve oxygen supply to the heart muscle, lower heart rate and improve the performance of the heart. The medication of the choice is a Beta blocker (usually Atenolol) to reduce on the one hand the risk of cardiac arrhythmias and on the other hand to counteract remodeling processes on the heart.
The prognosis for pulmonary stenosis varies depending on the severity and potential changes that have already occurred in the heart. Dogs with a low to moderate degree of disease often have an undiminished life expectancy. Dogs with a severe manifestation of the disease are dying, if not treated, usually early due to sudden cardiac death or develop severe congestion in the body's circulation, which can also lead to death. For this reason, it is very important to recognize the disease as early as possible and to perform pulmonary ballooning in severe cases. In more than 90% of the affected dogs, this results in a significantly improved performance and therefore a better life expectancy.
The prognosis for a (sub-)aortic stenosis varies depending on the severity and the potentially already occurring changes in the heart, but is usually very good for low to moderate grades. In severe cases, however, the prognosis is rather poor, so up to 80% of the affected dogs already die within the first three years of life due to the sudden cardiac death. For this reason, it is also important to recognize the disease as early as possible and to counteract the risk of sudden cardiac death by the targeted use of medication.