Coronary heart disease (known as atherosclerosis) is when the blood vessels that serve the heart thicken. These vessels have walls of muscle that can tighten and relax to change their diameter, so the body can control the flow of blood to organs, limbs and extremities to adapt to changing conditions.
Heart disease doesn't just affect the arteries of the heart; it impacts all of the blood vessels in the body, including those in the fingertips. Blood vessels are lined with a thin layer of cells called the endothelium, which protects the vessel walls from damage and modulates the way they expand and contract to maintain the right levels of blood flow and blood pressure. When the endothelial layer is not working properly, this is an early indication of heart disease. Blood flow is restricted so not enough blood is getting to the fingertips.
A related possible side effect of heart disease is something called Raynaud phenomenon, a condition that causes blood vessels to restrict and contract repeatedly, interrupting blood flow to the fingertips and, more rarely, the toes. (For some reason, the thumb is rarely affected.) During an attack, those areas become cold and pale, and a person may experience numbness, pain or swelling once the blood starts to glow back to the fingertips. In the most severe cases, the tissue can die if a blood vessel becomes completely blocked, leading to open sores or amputation.
Other underlying conditions that can lead to Reynaud's phenomenon include carpal tunnel syndrome or autoimmune disorders, such as lupus and AIDS.
The Endo-Pat 2000 is under continuing clinical investigation at major medical centers such as Mayo Clinic, Harvard and Yale. Pharmaceutical companies are also developing new agents to treat endothelial dysfunction are now including it in trials, and it was recently incorporated into the Framingham Heart Study.