Aortic stenosis (AS) is the narrowing of the aorta valve –a semilunar valve between the left ventricle and the aorta that prevents blood from flowing from the aorta back into the heart). This narrowing or partial obstruction of the opening of left ventricle into aorta puts pressure on the heart, causing it to work harder to pump out an adequate blood volume to the rest of the body. When the left ventricle pumps blood to the body, it goes first through the aorta. which branches into smaller arteries that supply oxygen rich blood to different areas. With aortic stenosis, the opening between the left ventricle and aorta is smaller than normal causing the left ventricle to work much harder to force the required amount of blood through the restricted area into the aorta and on to the rest of the body. This excessive and undue pressure causes muscle cells to increase in size to maintain forward blood flow and subsequent thickening of the heart wall. The defect or narrowing is usually caused by abnormal formation of nodules or a fibrous ridge or ring of tissue.
AS may be mild and not affect the quality or longevity of the dog's life or it may be severe. In later situations, supply of oxygenated blood to brain and other vital organs of the body is significantly affectd and results in fainting, collapse and sudden death.
This congenital (present at birth) condition is the second most common congenital heart defects in dogs and mostly affects large breed dogs such as Newfoundland, German shepherd, golden retriever, rottweiler, and boxer.
Aortic stenosis can be differentiated into three forms based on the location of the narrowing. These forms are vulvar aortic stenosis (stenosis in actual aortic valve), subvulvar aortic stenosis (present just below the aortic valve) and supravulvar aortic stenosis (present just above the aortic valve). Of the three forms, the most common form is subvulvar aortic stenosis. Development of this condition happens in first few weeks of the puppy and is complete by one year of age but onset of symptoms can happen in any age, depending on the severity of condition.
Many dogs may not show any symptoms of the disease other than an abnormal heart sound in the form of systolic murmur. In such dogs, the sound will be louder on the left side of the chest than on the right side; at the level of the heart base. In dogs that do show symptoms, most common symptoms are sudden collapse and exercise intolerance.
Other symptoms associated with aortic stenosis include
Congestive heart failure
Sudden loss of consciousness (syncope)
Difficulty breathing (dyspnea)
Rapid breathing (tachypnea)
Abnormal lung sounds
Irregular heart beat