Rust in the pipes

By Dr. Jim Ferguson

I like to be a bit unpredictable.  I want my readers to wonder what I’m going to say next.  Will he write about politics or medicine?  Will he launch into physics or discuss history?  Maybe this week will be a sermonette or a treatise on some philosophical point.  Actually, I worry that I’ve become too formulaic as I try to meld many of these perspectives into my essays.  And so to break the cycle I sometimes counter with an occasional travel story.

Some readers prefer medical topics, and others say I should keep my mouth shut and not comment on politics.  But then the ancient Athenian statesman Pericles said that those who mind their own business have no business there at all.  And what is an expert?  Is it someone who has a plaque on the wall from some university?  Right now we have a bunch of “experts” running the CDC and other branches of the government.  How’s that working out?  I believe the guy with street smarts and so-called common sense wins out any day over the pin heads in Washington and Pennsylvania Ave.

Becky and I built our home in 1980 and as result it’s aging with us.  We weren’t affluent when I began my practice in internal medicine.  Consequently, we built our house on a shoestring.  I would have waited until we could afford to build a house, but Becky is such an optimist she assured me that everything would be alright; and it was.  She even designed our home and was energized by the project.  I had diarrhea for a year from financial worries.

Recently, the thirty-four year old shoestring plumbing had become a problem with minor leaks and low pressure, despite a desalination system to combat calcium carbonate concretions from our well water.  When we first moved into our home we noted white deposits in our teapot.  A friend of mine at UT analyzed our water and assured me our family would never have constipation, and said we could sell our well water as a mineral tonic.  Unfortunately, the minerals in tonics may build up in old pipes and necessitate plumbing solutions.

Humans don’t build up rust as occurs in old plumbing, but we can develop narrowed arteries with limited blood flow.  We call the obstructing cholesterol-laden buildup in arteries plaque.  The buildup increases over a lifetime and is accelerated by the cardiovascular risk factors smoking, diabetes, hypertension and elevated LDL (bad) cholesterol.  Historically, plaque occurs at an earlier age in men than women, but equal rights and Virginia Slims have narrowed the age discrepancy.

The biological cardiovascular system is far more complicated than the simple pump and PVC pipes my plumber had to deal with.  The heart pump can vary its rate and strength of contraction, and its cardiac output as needed.  Furthermore, blood vessels are not like rigid copper tubing.  Blood vessels dilate and constrict to preferentially shunt blood to the digestive organs after a meal, or to your exercising leg muscles when you heed your doctor’s advice and go for a brisk walk.

Constriction and relaxation of muscles within arterial walls alter the vessel’s lumen and blood flow.  However, it’s even more elegant than this simple explanation.  The inside lining of arteries is called the endothelium.  This layer of the artery wall is only one cell thick yet its cumulative mass is comparable to that of the liver.  The endothelium is an active organ responding to various pressure and circulating molecules.  Have you even stepped on a puff-ball in the forest and marveled as thousands of fungal spores rise on the breeze?  Similarly, endothelial cells release tiny puffs of nitric oxide.  This is not to be confused with the dentist’s anesthetic laughing gas (nitrous oxide), Demi Moore’s recreational drug of choice.  Nitric oxide lasts only a few seconds in the blood stream yet is a potent agent of vascular dilation and regional blood flow.  Furthermore, the endothelial cells function is damaged by smoking and the other cardiovascular risk factors.

Some years ago a fascinating study was done to measure arterial reactivity.  The experimental model used a Big Mac and the flood of fats into the bloodstream as the “happy” meal was enjoyed.  The fat caused transient, but measureable, alteration in vascular dilation, ostensibly due to endothelial cell dysfunction.

Any injury produces inflammation as part of the injury-inflammation-healing process.  We take for granted that a skinned knee will heal.  We don’t consider the sublime forces at work that recognize the injury and modulate the healing process through signaling proteins called cytokines.  A part of that process is microscopic calcium deposition in the healing wound.  A gross example of calcium deposition can be seen in a healed bone fracture that is easily visible years after the injury.  A similar process occurs in blood vessels injured by toxins in cigarettes or the vascular stress from hypertension.  The end result is excessive cholesterol deposits within the vascular walls.  These deposits cause inflammation and heal with calcium accumulation that can be seen by CAT scans (computerized axial tomography).

Doctors and patients would like to know if they have a build-up of cholesterol-laden plaque in their arteries before a crisis such as a heart attack or stroke occurs.  Various non-invasive techniques have been developed to measure the plaque burden produced by the repeated atherogenic (plaque) injury-inflammation-healing process.  One such controversial technique is the coronary artery calcium score derived from a non-contrast CAT scan.  The higher the score the greater the risk of significant calcium-associated plaque.  This test is not covered by Medicare and can be expensive.  Additionally, the radiation exposure can be three times that of a mammogram and can uncover lung nodules that may lead to further invasive testing for benign or transient conditions.

The bottom line is that those of us north of fifty have rust (plaque) in our pipes whether we know it or not.  As more risk factors are added to the equation the risk of significant plaque with vascular obstruction and endothelial dysfunction increases.

As always, a careful medical and family history is better than the latest technique or gadget.  A good doctor listens to his patient and uses common sense to assess risk and benefit of any test.  And then the latest gadget can be used most appropriately.

 

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