The Boxer is likely to have a heart disease known as subvalvular aortic stenosis. The main symptom is the inability of the left ventricle to deliver the right amount of blood to the aorta. It works hard to function properly but eventually warns out which leads to serious heart problems. In many cases, surgery is applicable.
11. West Highland White Terrier
This courageous and independent small breed is subject to pulmonary stenosis. Because the pulmonary valve is too narrow, the blood is not going through the heart properly and the right ventricle fails. The blood does not receive enough oxygen and the lungs are under pressure.