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Pulmonic (Pulmonary) Stenosis

The pulmonary artery carries blood from the right ventricle to the lungs. If a congenital narrowing of this vessel or its valves is present, normal blood flow will be impeded. Without normal pressure, not enough blood can pass through the vein and enter the lungs. To compensate, the right side of the heart must pump harder. This enlarges its muscles and size. The right side of the heart becomes overworked and prone to failure.

What are the symptoms?
Most affected dogs initially show no symptoms even though a heart murmur will be present. These types of murmurs are typically noted on routine veterinary examinations with a stethoscope. Later in the syndrome, as the right side of the heart fails, it is unable to accommodate all of the blood returning from the body. This leads to edema or fluid build-up within the abdomen and limbs.

What are the risks?
In severe cases of pulmonic stenosis, the heart will be overworked. This can lead to a shortened life span and heart failure.

What is the management?
Minor cases are generally not treated. In severely affected dogs, surgery can be performed to remove the narrowing (stenosis) and improve blood flow.

Question and Answer

What is pulmonic stenosis?

Pulmonic stenosis is a heart defect that results in narrowing of one of the heart valves (the pulmonic valve). This causes blockage of the flow of blood from the heart to the lungs, which causes the right ventricle to work harder than normal. Back-pressure can build up behind the obstructed valve, which can lead to increased pressure in the veins of the body. The increased pressure causes fluid to accumulate in the abdomen or the chest cavity. Alternatively, the extra work may cause the heart muscle to become irritable, with abnormal heart rhythms. The obstruction to flow can limit the blood supply to the rest of the body, so that muscles do not receive enough blood supply during exercise. The brain may also be starved of its normal blood supply during exercise, leading to weakness or fainting.

What causes pulmonic stenosis?

Pulmonic stenosis is known to be inherited in some dog breeds. The tendency of certain other breeds of dog to develop pulmonic stenosis suggests that it may be genetic in these other breeds also.

What are signs of pulmonic stenosis?

Animals with mild pulmonic stenosis may not ever develop any obvious signs, apart from the presence of a heart murmur. The heart murmur is caused by turbulent blood flow as it accelerates past the narrowed valve. Animals with severe pulmonic stenosis may show reduced ability to exercise, or may faint or become weak with exertion. Some animals develop a distended abdomen as fluid accumulates, or they may develop breathing difficulties. A small number of animals may die suddenly without prior signs.

How is pulmonic stenosis diagnosed?

Your veterinarian may detect a heart murmur during a routine physical examination. This murmur can be heard by listening through the stethoscope. X-rays (radiographs) and electrocardiograms (EKG or ECG) may provide additional information about the cause of the murmur, but usually an echocardiogram (cardiac ultrasound scan) is necessary to confirm that pulmonic stenosis is the cause. Doppler echocardiography, a special type of echocardiogram, can precisely measure the severity of the obstructed valve. Some animals may develop heart failure, with excess fluid accumulating in the abdomen.

How is pulmonic stenosis treated?

A procedure called "Balloon Valvuloplasty" can be used to relieve the obstructed valve. During this procedure, a catheter is passed into the heart while the animal is under general anesthesia. A balloon is inflated to dilate the narrowed valve. The results can be very good, though final results can depend on the type of narrowing present. With some forms of pulmonic stenosis, balloon valvuloplasty may not result in much improvement. In these cases, surgery may be recommended to enlarge the obstructed valve. If heart failure has developed, fluid will accumulate in the abdomen and diuretic drugs may be given to help clear the excess fluid.

What is the prognosis for animals with pulmonic stenosis?

The prognosis is excellent for animals with mild pulmonic stenosis. For animals with severe pulmonic stenosis, the prognosis is guarded. Without some form of treatment to relieve the obstruction, most of the severely affected animals are at risk of heart failure, or premature death. Balloon valvuloplasty is a comparatively safe procedure. The risks associated with other surgical procedures are somewhat higher, and surgery is generally only carried out in the most severe cases.

The information on this page was obtained from the site www.peteducation.com and www.vetmedcenter.com