by Rob Lamberts, MD
What is an EKG?
The first test I’ll discuss is the electrocardiogram, or EKG. EKG’s can be used to diagnose a heart attack (past or present), abnormal heart rhythms, and other things that can go wrong with the heart.
How Does an EKG Work?
The heart has special cells that act like wires to tell the heart when to beat and make sure it does so in the right rhythm. An EKG looks at that electrical flow through the heart as it beats. During an EKG, electrical sensors are placed across the chest and on the arms and legs. These sensors pick up the electrical flow and can tell if the heart’s electrical flow is messed up.
What Does an Abnormal EKG Mean?
An abnormal EKG means one of three things:
Something happened to the heart in the past.
Something is happening to the heart right now.
Nothing is wrong; the person just has abnormal electrical flow in the heart to begin with.
That last point underlines how tough it is to read EKG’s; it takes a lot of experience to properly interpret one. EKGs provide the most information when a person has an old one to use for comparison.
What Does a Normal EKG Mean?
A normal EKG, on the other hand, does not mean:
There’s nothing wrong with the heart because the test can miss lots.
Nothing bad is going to happen.
An abnormal EKG is far more telling than a normal one.
Doctors use EKGs a lot because they’re cheap and very easy. But further testing needs to be done if you want more information about what’s going on with the heart.
What Is a Stress Test?
The most common test chosen after the EKG is the stress test. A standard stress test consists of an EKG done while the heart is beating hard. The easiest way to do this is to put the person on a treadmill (although other things can be used to increase the heart as well, such as medications, watching congressional hearings, or having a person’s spouse say: “we need to talk.”).
To make them even more accurate, sometimes a dye is injected that shows blood flow in the heart.
What Does a Stress Test Measure?
The main goal of a stress test is to see if the blood flow of the heart changes when there is increased demand for blood (which happens when a person is working hard—like when exercising). The plaques I discussed in my last article can narrow the blood vessel. The narrowed vessel may be able to supply the heart with blood at rest, but under increased demand (like with exercise), the heart can become starved for oxygen.
What Does an Abnormal Stress Test Mean?
A negative stress test does not mean there is nothing wrong; you can still have narrowing of the arteries that can lead to a heart attack.
An abnormal stress test usually indicates there is a narrowing of an artery supplying blood to the heart, although there are some cases where the test is abnormal on someone with a normal heart. But please be aware that a negative stress test does not mean there is nothing wrong either; you can still have less-severe narrowing of the arteries that can still lead to a heart attack. But it is reassuring if the test is normal.
What is a Cardiac Catheterization?
If the doctor thinks there is a high likelihood of narrowed blood vessels, even if a stress test or EKG were normal, the next step is a cardiac catheterization. In this diagnostic test, the coronary arteries are injected with dye and narrowing is identified.
A heart with narrowing in the coronary arteries is much more likely to have trouble in the future: either from a heart attack or from a fatal heart rhythm caused by decreased blood flow. What is done about the narrowing depends on how bad it is. A normal catheterization means that the likelihood of a heart attack in the near future is very low.
What is a Heart Calcium Score?
One test that is still quite controversial is the coronary calcium score. This test is a CT scan of the heart that looks for small amounts of calcium in the coronary arteries. That calcium isn’t a problem in itself, but it is a marker for the presence of fatty plaques that can lead to heart attacks. If calcium is absent from the coronary arteries, the chance of there being significant plaque build-up is very low.
So why is it controversial? First off, it exposes the person to a lot of radiation. That radiation is not dangerous in itself, but if added to other tests over a person’s lifetime, scientists fear that it could do harm. The second problem is that we don’t know how to interpret it. It’s not hard on either extreme: either a score of zero, or a very high score – indicating a lot of plaque. But what happens if someone low-risk gets a score that is low, but not zero? We really don’t know.
The only time I have found these tests useful is if I am trying to decide if someone needs to start on medication for cholesterol or blood pressure. The main purpose of these medications is to reduce future risk of heart attack, so the presence of heart plaque is key in my decision-making process. Don’t get it done unless your doctor recommends it.
What is an Echocardiogram?
The last diagnostic test I am going to mention is the echocardiogram, or the sonogram of the heart. This test uses sound waves from a probe placed on the chest to make a picture of the heart while it’s beating.
What Does an Echocardiogram Measure?
Conditions that are picked up by an echocardiogram include:
Past heart attacks
Valve problems, such as mitral valve prolapse
Congestive heart failure – which is when the heart is damaged enough that its pumping can’t keep up with the body’s demands.
Inflammation of the sack that surrounds the heart.
They do not, however, tell if someone is at risk for a heart attack or even if they have any plaque on their coronary arteries. Coronary artery catheterization is the right test for that.
So once bad stuff is identified, what can be done about it? That’s information for a future article.
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Let me once again remind you that this podcast is for informational purposes only. My goal is to add to your medical knowledge and translate some of the weird medical stuff you hear, so when you do go to your doctor, your visits will be more fruitful. I don’t intend to replace your doctor; he or she is the one you should always consult about your own medical condition.
Catch you next time! Stay Healthy!