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Canine pulmonic stenosis is one of the most common congenital heart defects in dogs. It consists of a malformation of the pulmonic valve leading to obstruction to the flow of blood from the heart into the lungs. This a hereditary condition, hence breeding of affected animals is highly discouraged.
Blood arriving from the body and head to the right atrium in the heart passes through the tricuspid valve into the right ventricle before being ejected into the pulmonary artery through the pulmonic valve. This blood is directed to the lungs and after "loading" with oxygen returns to the heart via the pulmonary veins into the left atrium, passes thorugh the mitral valve into the left ventricle and is ejected to the whole body through the aorta.
The valve cusps open completely.
|Fused valve (Type A)
The valve cusps are fused and fail to open completel
|Dysplastic valve (Type B)
The orifice of the pulmonic artery is too small and the valve cusps are rudimentary and fused.
|Mild stenosis: pressure < 50 mmHg
In these cases life expectancy may be normal and clinical signs may never be observed throughout life.
|Moderate stenosis: pressure > 50 mmHg and < 80 mmHg
Some dogs may cope well with the disease and some may not. The heart is chronically subjected to higher stress than normal and forced to work more than it should. The heart muscle will become thicker in order to compensate for this increased effort. Clinical signs may occur at any point throughout life.
|Severe stenosis: pressure > 80 mmHg
Dogs with severe stenosis are at increased risk of clinical signs, heart failure and even death.
Possible significant complications consist of occurrence of life-threatening arrhythmias which must be dealt with swiftly and on very rare occasions may result in death during the procedure. The use of beta-blockers (normally given ahead of the procedure) reduces this risk. Although a rare occurrence, presence of catheters and wires within the blood vessels and the heart risks damage to these structures and at worst rupture and internal hemorrhage which could result in death or may require urgent surgical repair with open-chest surgery.
Less serious complications such as hemorrhage at the incision site and arrhythmias may occur in about 5% of the cases.
Re-formation of the narrowing may occur in up to 10% of cases and a second procedure may be necessary. This usually occurs several weeks to months after the procedure and is not possible to foresee.
Is it possible to perform in all cases ? No. The procedure may not be possible and may be abandoned if severe thickening of the heart muscle does not allow passage of the catheters up to the pulmonic valve or if the risk of life-threatening arrhythmias is perceived to be high. In some cases, detection of an abnormal coronary artery close to the pulmonic valve during the procedure, may be another reason to abandon the intervention due to the risk of rupture resulting in death.
This procedure is effective in about 80% of the cases of canine pulmonic stenosis. Ideally, pressure in the right ventricle is reduced to half of the initial pressure or less than 80 mmHg. Balloon valvuloplasty is more effective in type A pulmonic stenosis than type B.
"Dogs with severe pulmonic stenosis live longer when balloon valvuloplasty is successfully performed."
Shorpe, Donald P. Balloon theBalloon Valvuloplasty of valvular pulmonic stenosis in the. . Clin 182Clin Tech Small Anim Pract, 2005; 20:182-195
C. Bussadori, C. Amberger, G. Le Bobinnec, C.W. Lombard,, Guidelines stenosisGuidelines for the echocardiographic studies of suspected subaortic and pulmonic stenosis .. European Society CardiologySociety of Veterinary Cardiology
M. Strafford Johnson, M. Martin, D. Edwards, A. French and W. Henley, Pulmonic Stenosis in Dogs: Balloon Dilation Improves Clinical Outcome. Journal of Veterinary Internal 656Internal Medicine 2004; 18:656-662
Chiara Locatelli, Oriol Domenech, Pedro Oliveira, Joel Silva, Elisabetta Sala, Paola G Brambilla, Claudio Bussadori, Independent longIndependent predictors of immediate and long--term results after pulmonary balloon valvuloplasty in dogs. Journal 21Journal of Veterinary Cardiology 2011 Mar; 13 (1) :21-30
P. Oliveira, O. Domenech, J. Silva, S. Vannini, R. Bussadori, C. Bussadori, Retrospective review of congenital heart disease in 976 dogs. Journal of Veterinary Internal Medicine 477Medicine 2011; 25:477-483