Your heart. Do you think about it? Are you aware of it? Probably not. Given some regular attention, you can ensure it doesn’t have to remind you that it’s there.
In basic terms, the heart is a muscle about the size of your fist. But it’s not solid, and it’s not only muscle. A human heart has four cavities, surrounded by muscle and separated by fibrous valves that direct the blood flow through those cavities (and don’t allow backflow). The two cavities at the top of the heart are the right atrium and the left atrium. Below them are the right and left ventricles.
Blood comes into the right atrium from the rest of the body. It’s sent through the right ventricle and out to the lungs, where it picks up oxygen and dumps carbon dioxide. Blood flows from the lungs back to the left atrium, into the left ventricle and back out to the rest of the body to deliver a fresh load of oxygen. The muscle of the heart itself is supplied with nutrients, energy and oxygen by a network of blood vessels on the surface of the heart.
The electrical system of the heart, the conduction system, carefully coordinates all of this pumping activity. At the top of the heart, there’s a nerve bundle called the sinus node, that charges and discharges automatically at a variable rate. That’s your pulse. The sinus node initiates the contraction of the atria and then sends an electrical impulse to the ventricles so that they can contract exactly when they’ve filled with the optimal amount of blood to pump at maximum efficiency.
This all happens over and over and over again, 70 times per minute, more than 100,000 times per day. If any one of these structures is damaged or malfunctions, your heart will demand attention.
The muscle itself can be damaged by infection, which is fairly rare but can be so serious as to require heart transplant. Chronic alcohol abuse, abnormal deposits of iron or other fibrous substances can also damage the heart muscle. When the heart muscle can’t keep up with the body’s demands, congestive heart failure can result.
If the blood vessels get blocked, either chronically with cholesterol deposits or suddenly with a blood clot or spasm, that can cut off blood flow to part of the heart muscle causing a “myocardial infarction” or heart attack. This can also lead to heart failure. Cigarette smoking and high blood pressure can cause damage to these vessels, thus making them more susceptible to blockage
Heart valves can be damaged by infection, chronic calcium or cholesterol deposits and other conditions, either producing obstruction to flow or allowing backflow. Either way, it disrupts normal function.
The electrical system of the heart is crucial for optimal function. Rarely, total failure of the sinus node can occur, resulting in the heart just stopping. Without rapid intervention with CPR and advanced procedures, this is fatal. But there are many common, very troublesome, disorders of the conduction system.
“Sick sinus syndrome” means the sinus node slows down or periodically fades and spurts, causing very slow heart rates that lead to episodes of lightheadedness or loss of consciousness. This is typically treated with a pacemaker.
“Atrial fibrillation” is a condition in which the atria quiver or contract erratically, losing their orderly connection with the ventricles. The presence of atrial fibrillation can increase risk of stroke by two to five times as clots may develop more easily in the atria. There are many causes and treatment is complex—but very important to reduce risk of stroke and other serious consequences.
Many other disorders of the conduction system can occur which can produce relatively minor consequences, from the palpitations many of us feel from time to time to very serious conditions that may severely compromise the function of the heart.
Taking good care of your heart is a matter of doing the things we’ve advocated in this column over and over again: exercise regularly; keep your weight in the ideal range; keep your blood pressure controlled; don’t smoke; consume alcohol in careful moderation; have happy interests in life; get adequate rest and keep stress under control; and eat a healthy diet that’s low in fat and animal products with plenty of fiber, vegetables and fruits of many colors. Take care of your heart and, with a little luck, it’ll never make you pay any special attention.
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