Plumbing, Wiring, Drywall

My father, a professor of undergraduate human anatomy and physiology, used to stump his class by asking them what the biggest organ of the body is.  The immediate answers—brain, liver, colon—would, of course, all be wrong.  The skin, he’d explain, with its epithelium, sweat and oil glands, hair follicles, and subcutaneous tissue, is the largest organ of the body.  He used this example to define for his class the term organ, then launched into further elaboration of nomenclature such as tissue and organ system.

The skin is the organ we are all most familiar with (we see it every day, after all—can’t exactly say that about the brain, eh?) and recognize this structure in all its variation.  We all know that the pads of our feet are very different from the thin membranes of our eyelids, and no one would confuse the hard, deadened keratin of our nails with the soft, sensitive skin of our lips.

Diseases of the skin come in a dizzying array of shapes and colors.  An entire medical specialty (with 3 years of dermatology residency training) is predicated on the recognition and treatment of the myriad of moles, rashes, blisters, and lesions that can afflict our outer shell.  When a discoloration or bump pops up on our skin we may not know what it is, but we sure know it’s not supposed to be there.

We’re also pretty clear about the nature and extent of our skin problems—we know that being cursed with one type of skin malady doesn’t necessarily mean that we’re destined to get them all.  If a doctor tells you that you’ve come down with a case of, say, acne, you wouldn’t immediately assume that your skin will break out in lichen planus, psoriasis, and eczema.  Even the least educated among us recognizes that there are lots of ways our skin can get sick.  In a way we’re all sort of skin experts (because it’s so visible) to a degree that we can’t claim about other organs.  There’s a reason we say “I know that like the back of my hand” and not “I know that like the back of my prostate.”

The heart is clearly a different story.  The public’s understanding of heart disease is pretty one-dimensional, despite the fact that there are dozens of completely unrelated ways in which the function of the heart can be impaired.  For many people, the diagnosis of any one type of heart disease is taken as a declaration that all other cardiac ailments must also be present.  I tell a patient he has a leaky valve and he assumes this means he’ll have a heart attack.  A patient diagnosed with atrial fibrillation (because this involves her heart) goes home and tells her family that she has heart failure and comes back the next week asking about defibrillators and heart surgery.

In order to better help us understand the independence of the various aspects of heart function I’ll use the example of the construction of a house to better explain (I can’t, by the way, can’t claim credit for this metaphor.  I’ve heard this from several other cardiologists and think it’s a pretty clever way to think about the heart).

Structural: The chambers and valves of the heart are the framework of this organ and, like the framework of a house, can have structural problems.  Congenital heart problems, such as septal defects and chamber rearrangements, are like design flaws that put doors and windows in all the wrong places and sticks a bathroom where the kitchen belongs—the early, developing cells of the heart did exactly what the DNA told them to; it’s just the blueprint that was faulty.  Older patients can develop structural problems in hearts that were normal earlier in life.  Examples would be leaky or narrowed valves that lead to inefficient movement of blood through the cardiac chambers.  Just as framework problems in a house are best addressed by carpentry, structural heart problems are often treated with surgery—replace the valve, patch the septal defect, etc.

Electrical: The electrical system of the heart is a separate system altogether and is, of course, akin to the wiring in a home.  Electrical problems come in two main varieties: too much electricity and too little.  More electrical signals lead to rapid rhythm abnormalities and can be treated with medication and ablation procedures.  A shortage of signals results in bradycardia, or slowing of the heart, that is easily fixed with the implantation of a pacemaker.  In the medical world—as in the world of home construction—certain practitioners specialize in problems of an electrical nature (electrophysiologists) and perform the procedures needed to correct both racing and sluggish heart rhythms.

Plumbing: Finally comes the plumbing.  The heart muscle receives its supply of oxygen and nutrients not from the gallons of blood it pumps every day, but rather through its own set of arteries that arise from the aorta just as the blood is pumped out of the ventricle.  Plug up just one of these miniature conduits and you suffer a heart attack.  The plumbers in our trade are the interventional cardiologists who specialize in putting very small stents in very small spaces.

While it’s true that there are certain areas of overlap in function, many of the cardiac disease processes tend to afflict the heart in isolation.  A patient with atrial fibrillation (electrical) doesn’t necessarily have any higher risk of heart attack (plumbing) than someone with normal rhythm.  Aortic valve stenosis (structural) has no immediate correlation with, say, supraventricular tachycardia (electrical) or coronary disease (plumbing).

Outside forces can affect all three subdivisions.  A good example is uncontrolled hypertension which will eventually lead to left ventricular hypertrophy (structural) and serves as a risk factor for heart attack and stroke (plumbing).  Atrial fibrillation (electrical) is more prevalent among patients with uncontrolled hypertension because the long-standing pressure exerted on the delicate left atrial chamber ultimately expands this chamber (structural) and makes the muscle more electrically irritable.

While the heart may not have as many unusual syndromes as the skin (or as many bizarre names, to wit “pityriasis lichenoides et varioliformis acuta”) it clearly has a variety of categories in which problems can arise, categories that often represent separate and unrelated issues.  To those of you with heart problems I encourage you to educate yourself on both what you have as well as what you don’t have.  Ask your doctor how your illness and your medications affect the other functions of the heart.  Find out what you need to know to be as educated about your heart as you are about your skin—get to know your heart as well as you know the back of your hand.