YOUR HEALTH - MEDICINE 101

ELECTROCARDIOGRAM

Did you know that your entire body produces small amounts of the same kind of electricity as this battery?

Every single cell within the body has a different electrical charge on the inside and the outside. During many cell functions, this electrical charge changes. Nowhere in the body is this more apparent than in the heart where the natural pacemaker cells fire regularly to initiate a heart contraction. In 1887 a Dutch physiologist named Einthoven tried to measure the small electricity that was produced by these pacemaker cells. He attached sensors to the limbs and chest wall and found he could pick up a small electric current with each heart beat. We're not talking about enough current to turn on a radio here - that would need 220 volts. But Einthoven found that at the skin he could measure one millivolt of current each time the heart contracted and by moving his sensors around the body he could produce a picture of the electrical activity within the heart. He called this technique an electrocardiograph - ELECTRO from the word electricity, CARDIO from the heart, and GRAPH meaning picture. But we know it as the ECG.

Today the E.C.G. machine looks like this. Various leads or sensors are attached to your arms and legs and also across the front of your chest. These leads sense the electricity in twelve different combinations, and then spit out a graph. It's a photograph of what the electricity of the heart looks like at that particular time. There are three different parts to the electrocardiogram - the first part, the P-wave, shows the electrical activity within the atria or collecting chambers of the heart. The next part reflects the electrical activity when the ventricles contract and the last part reflects the electrical activity as the ventricles electrically come back to normal. Here's what a normal electrocardiogram looks like.

But here's one that shows the heart rhythm isn't right - the P-wave, the electrical activity of the atria, is simply not present, and the heart rate is irregular. This is called fibrillation of the atria. It means the atria aren't contracting - they're just quivering. Here it is in the ventricle - called ventricular fibrillation … that's a life -threatening irregular heartbeat.

The E.C.G. is often used to diagnose a heart attack. Here's what it looks like - the heart cells aren't getting adequate blood flow and that changes the electricity patterns. You can see the difference in the configuration of this area of the E.C.G. Not bad for something more than a century old. It's cheap, non-invasive, and gives a lot of information.

When Joni Mitchell sang "You turn me on, I'm a radio", I don't think she was talking about electrocardiograms, but she was talking about the same principle - each of us is filled with electricity. Sometimes it's the electricity of love, but mostly it's the electricity of life.