This is the first article in a two-part series. Go here to read the second article, "Heart Health Basics: What is a "Normal" Blood Pressure?"

I am a big proponent of taking your health into your own hands. This entails collecting data about your health then making good decisions based on the numbers. There are many tests you can take, and often the challenge is to get the right tests ordered and then understanding what to do with the results.

But, there is one test virtually every heart patient gets multiple times per year and it is easy to understand: your blood pressure.

We all recognize that high blood pressure is a problem that leads to increasingly severe heart disease. Yet both doctors and patients often fail to keep abreast of the latest discoveries regarding blood pressure, and, most importantly, what a healthy blood pressure is.

What is blood pressure?

Your arteries are essentially a vast network of tubes that deliver life-sustaining blood, pumped by your heart, to all the tissues in your body. The blood pushes against the inner walls of your arteries and creates pressure. If your arteries are soft and supple they expand easily to accommodate your blood flow, creating relatively light pressure. As arteries become diseased, they stiffen and “push back” with increased pressure. Over time, this higher pressure can damage your heart and entire circulatory system.

With every heartbeat, the heart muscle contracts, squeezing approximately one-third cup of blood out of the heart-pumping chambers and into your arteries, raising your blood pressure for a fraction of a second. This heart contraction is known as “systole” (pronounced sis-toe-lee) and the pressure measured at this point in time is known as “systolic pressure.” It is the first or “top” number reported by your doctor.

After contracting, the heart muscle relaxes and the brief rush of blood is rapidly distributed along all the body's arteries. This causes pressure to drop to its original level. This relaxation phase is known as diastole (dye-ass-toe-lee) and the pressure measured at this time is known as diastolic pressure, the second or “bottom” number reported.

For example, a common blood pressure of “120/80” (reported as “120 over 80”) means the systolic pressure (during heart contraction) is 120 mmHg (millimeters of mercury), the same pressure produced by a 120 mm column of mercury, while the diastolic pressure (during heart relaxation) is 80 mmHg.

Two little numbers provide a wealth of information

This small amount of blood pressure information can tell us a great many things about our health.

Diet. Blood volume and therefore blood pressure can increase due to fluid retention often caused by high sodium levels. A major contributor to high sodium levels is excess salt in our diet.

Kidney function. High blood pressure (hypertension) may signal varying degrees of kidney failure. If the kidneys are unable to remove excess fluid from our bodies, blood pressure rises.

Internal bleeding. Not surprisingly, blood volume and blood pressure drop if you are hemorrhaging internally. Bleeding is easy to spot on the outside but not quite so simple on the inside!

Dehydration. It is easy to become dehydrated without realizing it. It happens all the time. One sure sign of dehydration is low blood pressure.

Heart plaque (atherosclerosis). As explained above, “stiff” arteries “push back” harder against blood and this push back is measured as increased blood pressure. One of the principle ways arteries stiffen is by accumulating cholesterol that hardens into plaques over time.

Aortic valve problems. If the aortic valve fails to completely close after contraction, blood will leak back into the heart and create abnormally low diastolic blood pressure.

Exercise tolerance. Systolic blood pressure should rise with exercise but anything above 170 mmHg can indicate a problem. Interestingly, diastolic blood pressure dips slightly in young, healthy individuals, so a rising or even unchanged diastolic pressure can signal anything from natural aging to heart problems.

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