Cardiology · Beaumont and St. Joseph Mercy
What is Blood Pressure? - Dr. James Heinsimer

What is blood pressure and why should I care about it?

Heart to Heart conversation: The Basics of Blood Pressure

Blood pressure is the measurement of the force created by the pumping of the heart as it sends blood through the blood vessels of the body. The blood vessels which are called arteries are the pathways that send blood to all of the organs of the body. When the heart pumps, it pushes blood out of the heart into the arteries. This pressure when the heart contracts is called the systolic pressure. When the heart relaxes after each contraction, the pressure inside the heart falls and valves opened to allow blood to go into the main pumping chamber (ventricles). This is called the diastolic blood pressure. A typical blood pressure might be 120/80 with the 120 representing the "systolic" pressure when the heart contracts and 80 being the "diastolic" pressure when the heart is relaxed. We measure these pressures in millimeters of mercury which is abbreviated "mmHg".

We care about these numbers because high blood pressure ("hypertension") can cause damage to blood vessels (from big arteries such as the aorta to small arterioles that go to the very small capillaries). High blood pressure can and does damage all of the arteries but causes particularly noticeable havoc to the arteries of the heart, the brain, the kidneys, and the eyes. When blood pressure is too high, the force of the blood causes direct damage to blood vessels and leads to such problems as heart attack, stroke, kidney failure, blindness and actual blood vessel rupture. So we care about high blood pressure because we want to prevent all of these problems. By controlling blood pressure along with fixing other risk factors such as high cholesterol, excess weight, high sugar and smoking, over years, the arteries avoid the damage and patients tend to do much better.

Two misconceptions are common about high blood pressure ("hypertension"). First, many people think that when doctors refer to "hypertension", that we are talking about someone who is anxious (too much tension). While it is true that anxiety and stress can raise blood pressure and cause hypertension, the term "hypertension" doesn't refer to someone who is tense. People who are perfectly calm can still have hypertension.

Second, many people think that they can "feel their blood pressure" but in most cases, high blood pressure is a "silent killer". Specifically, people may have headaches that they think is caused by their blood pressure and say that they can feel when their blood pressure is up. Basically the anxious feelings or pain due to the tension headache (often due to contraction of the muscles of the scalp) may cause the high blood pressure. So the high blood pressure and stress or pain may be associated but usually the blood pressure does not cause the headache (unless a blood vessel has ruptured which is usually severe and fairly dramatic and not the run of the mill headache).