It's easy to imagine the cardiovascular system in a simplistic way. First of all, the heart is the pump. It can vary the fluid flow in the system by either pumping more forcefully, more frequently, or by increasing pump volume. Then there are the pipes, which are the arteries and the veins. The pressure and velocity in the vascular system depends on the diameters and tone of the pipes. Think of squeezing a garden hose and feeling the pressure and velocity rise. The main plumbers in the system are the kidneys, making constant adjustments in the fluid viscosity and in the pipes' diameters with chemical vascular tone enhancers or tone reducers.
This is, of course, a very simplistic model for a living system. The true system is infinitely more complex. The heart has both innate mechanisms and brain hook-ups which make moment to moment changes in its pumping capacities. The pipes are alive and stretch and contract, altering the force within the system. Rather than two plumbers, there are numerous cells and chemicals which make continuous adjustments in the system. Sometimes these mini-plumbers can work against one another in a counter-productive fashion or too much to drop the pressure or too little to decrease the pressure.
Before we proceed, we need to clarify why blood pressure and hypertension are such critical determinations. Simply put, they are major factors in the occurrence of coronary heart disease, stroke, kidney failure, aneurysms, and overall health and longevity.
What are desirable and undesirable blood pressures? Any values less than 120/80 are considered normal and desirable. If a blood pressure is 120 to 139/ 80 to 90, this is called prehypertension. This is a strong indicator of blood pressure problems to come. A blood pressure of 140 to 159/90 to 99 is called Stage I hypertension. Values above 160/99 are called Stage II hypertension, and can lead to serious consequences.
There may be underlying medical causes for high blood pressure like thyroid, pituitary, or adrenal conditions called secondary hypertension. If there is no apparent underlying cause, it is called essential hypertension. 90% to 95% of hypertension is essential. This is not to say we don't know things which can contribute to hypertension like obesity, family history, being of African-American or Native-American race, excessive use of alcohol, poor physical conditioning, and excessive intake of salt. Although these factors contribute to hypertension, their effect is still considered essential hypertension.
The medicines for hypertension basically work on the cardiovascular system at various levels to reduce the blood pressure. One of the first treatments to have been used is diuretics, which reduce the fluid volume in the system. They work by causing the kidneys to excrete sodium, or salt, and this salt takes fluid with it. The beta blockers and calcium channel blockers reduce heart pumping force and rate, and relax blood vessel constriction. Then there are the so-called ACE inhibitors which interfere with the kidneys making angiotensin II from renin, a kidney-secreted hormone. Angiotensin II is a substance which constricts blood vessels in the vascular system. Finally, there are the ARB's which actually block the receptors for angiotensin II in the blood vessel walls.
So here's the deal with your blood pressure: You've got to check it frequently. Mostly, it is silent in its relentless destructive processes, and unless it is advanced to the point that you're having severe headaches, passing out, going blind, or going into kidney failure, you won't otherwise know it's elevated. Stick your arm in those blood pressure measuring devices when you're waiting at the pharmacy. Have it checked when you're at a health fair. If it is showing up elevated, go ahead and invest in a blood pressure device you can use at home especially with a printer that can record your pressure accurately and permanently. Be sure you know how to use it; have it checked for accuracy at your physician's office. Keep a notebook with your blood pressure readings in it, and always take it with you when you see your physician.
Take your blood pressure medicine every day, and don't miss a dose. Remember the lifestyle changes that can benefit your blood pressure-- like slimming down and getting moderate exercise every day. A diet that's low in salt, cholesterol, and saturated fat can't do anything but help you. Evaluate your alcohol intake: if it's more than a drink a day, it would be good to reduce it to that level. Smoking is something else that elevates blood pressure. Be aware that you may have family or ethnic history that predisposes you to high blood pressure. If you are diabetic, it is especially important that you keep your blood pressure at the lowest desirable values.
There is probably nothing more significant that you can do for your immediate and long-term health than maintaining a normal blood pressure. There are enough medicines available, and at reasonable costs, that everyone should be able to do this vital step. It is a tragedy when someone has a stroke or a heart attack, or ends up on a dialysis machine, because he or she had high blood pressure which could have been controlled with a simple office visit to their physician several times a year.
Douglas Beatty M.D.
Doctors Medical Center
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