Instead of sealing the portal between the two chambers when the ventricle contracts, a prolapsed mitral valve is forced backward into the atrium, allowing some of the blood that has just left there to return. The culprits in this condition are stretched and weakened papillary muscles, which ordinarily hold the lips of the valve tightly in place. The mitral valve plays a role in other problems as well. In the condition called mitral valve stenosis, the opening narrows, hindering the normal progress of blood from the atrium to the ventricle. The problem is an aftermath of rheumatic fever.
Blood pressure is the measure of the force of blood traveling through the circulatory system.
Contraction increases the resistance, reducing blood flow, increasing blood pressure, and thereby causing the heart to work harder. Nearly everyone is familiar with the blood pressure cuff, called a sphygmomanometer, which is strapped on during a physical examination to measure blood pressure. Men are more likely to have high blood pressure than women, but African American women have higher levels than any other group. The cause of most hypertension is unknown, although overweight and excessive salt in the diet seem to be contributing factors. A genetic component is also likely.