A hazardous materials placard is a diamond-shaped sign that must be affixed to any motor vehicle that carries hazardous materials. Ordinarily, it has a four digit number in the middle of the placard and a one digit number at the bottom that shows the hazard class and specific material being carried.
Aortic stenosis is abnormal narrowing of the aortic valve. A number of conditions cause disease resulting in narrowing of the aortic valve. When the degree of narrowing becomes significant enough to impede the flow of blood from the left ventricle to the arteries, heart problems develop. The oxygenated blood then returns to the left atrium and passes through the mitral valve into the left ventricle. 2  Blood is pumped by the left ventricle across the aortic valve into the aorta and the arteries of the body.
There are four valves in your heart including the mitral, tricuspid, aortic and pulmonic valves. The aortic valve is located between the left ventricle (lower heart pumping chamber) and the aorta, which is the largest artery in the body.Valves maintain one-way blood flow through the heart. 1  Click here to learn more about the heart valves.ortic valve disease occurs when the aortic valve does not work correctly. This can be caused by: 1  Aortic valve stenosis: These stiff, fused, thickened, inflexible valve leaflets lead to the narrowing of the aortic valve, that limits the blood flow.