Angina Without Pain

Shortness of breath may not be due to a lung problem.

Human respiration is simple until you begin to think about it, at which point certain complexities become apparent.

On average, we breathe in and out about twenty times a minute, a rate that varies depending on our bodies' demand for oxygen. The rate setting mechanism is in a control center in the primitive portion of our brain, and we aren't normally aware of its activity.

Here's a brief reminder from your sixth-grade biology teacher: The goal of the respiratory system is to provide body cells with a raw material, oxygen, which they need to function properly. Coincidentally, used up oxygen, as carbon dioxide, is blown off. (Remember your first artificial respiration mantra? "Out goes the bad air, in comes the good?")

There are three parts of the respiratory system, lungs, heart, and red blood cells. Malfunction in any of these three will result in less oxygen being delivered to cells. The rate setting department responds to this by increasing the frequency of respiration, and the owner of the lungs becomes aware that something is awry. The word for this is "dyspnea" (dis-knee-uh).

It is easy to think that all dyspnea is due to malfunction of lung tissue, since most of the time, it is. Asthma, emphysema, chronic bronchitis and pneumonia are some of the common malefactors. When the red blood cell mass is too low (for a variety of reasons, including a rapid change in elevation) shortness of breath will result. What this is leading up to is this: Another, and slightly unusual reason for dyspnea, coronary artery disease.

When flow of blood in the arteries to the heart muscle is shut down or decreased, the symptom usually felt is pain in the chest. That's angina, isn't it? Everyone who reads this column regularly knows that. Now it's time to add another symptom, dyspnea, to those which might signal coronary disease (others are unexplained sweating and faintness).

The explanation for the dyspnea is best put like this: Heart muscle that isn't getting much blood can't function (pump) well, and the overall cardiac output falls. Since the heart, as the third member of the respiratory "system", has to deliver the goods to the body, its failure to do so has consequences. One of them is (fanfare!) lack of oxygen to the tissues with dyspnea symptoms close behind.

There is a gender thing going on here - women are twice as likely as men to experience dyspnea as their only symptom of angina. Nobody knows why there is this difference between the two main types of humans.

There is one known factor in the "painless angina" syndrome - that's diabetes. People with diabetes may not experience painful angina (or even a painful heart attack) because their sensory nervous systems lose their ability to perceive pain. Women without diabetes, and otherwise perfectly normal, can feel pain just like anyone else, so what's with this "angina without pain" business?

Perception of pain takes place in the more advanced portions of our brains, the place where we do art and calculus. It has been known for years that there is a gender difference. Women, who endure the discomfort of childbirth (which would send most men screaming for morphine), are more likely to have chronic pain syndromes such as fibromyalgia and TMJ.

There is a difference between the sexes, and it isn't just hormonal. Interested parties are working on it - so far, there are some theories. These mostly relate to the presence or absence of receptors, or something that stimulates receptors, in the brains of males and females. Or maybe it's something totally different! Whatever the cause, women will have shortness of breath as their only angina "symptom" twice as frequently as men.

(For the sake of common decency, there will be no quiz on this material.)