Who should get a stress test and when?

"Doc my buddy was only 40 and he just died of a heart attack. All our friends are getting stress tests now. Do you think I should have one?"

This is a sad story but one I hear at least once or twice a year. Heart attacks or Myocardial Infarctions (MI's) are all too common. Although it may seem like cancer is public enemy number one, heart disease kills more people in the U.S. than all cancers combined. There were nearly 600,000 deaths in the U.S. due to heart disease in 2011.  The incidence of heart attacks climb dramatically after age 65 but many adults will see their first friend have a heart attack when they are in their 40's.

Source: "Health, United States, 2012, With special feature on emergency care"

Given the fact that most MI's in this age group occur with little warning it's understandable that these events strike fear in the hearts of men and women who begin to consider their own mortality. Its logical therefor to wonder whether a stress test might be a smart idea for those who want a bit of insurance against our number one killer. So what is a stress test and who should consider having one done?

What is a stress test?

There are several types of stress tests.
  • Standard Stress Test
  • Echo Stress test
  • Thallium ( or Nuclear) Stress test
All three types of stress tests require the individual to walk on a treadmill in order to "stress" the heart muscle. The only difference is in the way they evaluate how that stress is affecting the heart.

A standard stress test connects the patient to an EKG machine and looks for signs of stress in the hearts electrical activity. Heart muscle that is not getting enough blood flow may not conduct electrical impulses normally and this can show up in the EKG

An Echo Stress Test uses a sonogram ( echocardiogram) to examine how the heart muscle moves before and after the patient walks on the treadmill. Here we are looking for any sign that inadequate blood flow is causing some of the heart muscle to contract less effectively.

With a Thallium or Nuclear Stress Test the doctor injects the patient with a radioactive substance that is picked up in the heart. Areas of the heart with decreased blood flow will pick up less of the radioactive tracer. A detector is placed over the chest before and after the patient exercises on the treadmill and an image is created showing where the tracer was distributed. If there is an area that did not get as much tracer then this may indicate poor blood flow.

There is no "best" stress test. Each type of stress test has its advantages and disadvantages. Your doctor will determine which type is most appropriate for your situation if you need one of these.

Who should have a stress test?

Stress tests were originally designed to help doctors diagnose a patient who came in with complaints of chest pain. Many things can cause chest pain. Most of the time when a patient sees a doctor for chest pain the heart is not the source of the problem. So how does a doctor decide who has a heart problem and who doesn't?  We needed a non-invasive way to determine which patients might require further more invasive testing and which ones could be managed conservatively. To fill this need the stress test was invented.

There is little controversy about the use of stress tests in situations where a patient is having chest pains, but what about someone who has just seen their friend have a heart attack and wants to see if he or she is at risk? Unfortunately this is one of those areas where what happens in real life doesn't match up well with what the facts and the science tell us.

Most patients who walk into their doctors office with this question will likely get an EKG and even if that is normal they will often be scheduled for a stress test to ease their concerns. The approach that many doctors take and patients demand is "better safe than sorry". No one wants a patient to walk out of their office with a life threatening condition when there might have been something they could have done about it. This argument ignores one important fact though. Stress tests are not harmless, and if there is a potential risk or side effect to a test then we need strong evidence that the good the test might do will outweigh the potential harm it can cause.

What are the risks of doing a stress test?

So what are the risks of having a stress test? All you do is walk on a treadmill right? How risky can that be?  All good questions that deserve good answers.

The most obvious risk of the stress test is the treadmill itself. While it doesn't happen often, there are some patients every year who have a heart attack during the stress test. Its difficult to know in advance who this might happen to, but while its rare, the risk does exist.

The more important and more common risk is the one no one considers. What if the test results are wrong ? Stress tests like all tests are not perfect. There are false positives and false negatives.

A false negative is a test that says everything is fine when its not. The risk here is that the patient goes back to their bad habits and has a heart attack later that might not have occurred if they had not been reassured and the impact of their friends heart attack had stuck with them.

False positives are a much bigger concern There is no way to know if a stress test is a false positive unless we do further testing. With heart disease that often means doing an angiogram. During an angiogram a doctor threads a catheter through a large vein in the groin or the arm up to the heart and then injects die into the arteries of the heart so they show up on an x-ray imaging screen allowing the doctor to see if there is a blockage. Angiograms are relatively safe but there is always some risk when you do an invasive procedure. Those risks include hemorrhage, triggering an irregular heart beat ( arrhythmia), infection, kidney damage from the dye, and even sudden death. The overall rate of complications from cardiac catheterization is approximately 2-3% with a death rate of about 0.08%1. These numbers are low but they are not zero. When a patient's risk of heart disease is high ( someone with suspicious chest pain) the risk may be acceptable but if the person is healthy then the logic of going down this path needs to be reconsidered.

Should we do stress testing on someone who has no symptoms?

Ideally we would like some studies that followed asymptomatic men and women who had stress tests done and compared them to a similar group who did not undergo screening. If we compared these two groups we could then determine if screening reduced heart attack deaths and more importantly we would want to know if screening decreased the overall death rate. It does no good to reduce the deaths from heart attacks if the screening and subsequent treatments then increase deaths by some other route.

Unfortunately no such study has been done. The U.S Preventive Services Task Force reviewed this subject2 recently and was unable to find any studies that addressed this issue. Some studies have been done which examined how well stress tests predict cardiac risk compared with other methods but none of them examined whether adding stress test to the usual risk assessment method improved the outcome of patients.

Because of the lack evidence to support the benefits of routine stress testing the USPSTF as well as the American College of Cardiology and the American College of Physicians recommend against using stress testing in low risk asymptomatic individuals. For patients with moderate risk it is felt that there is insufficient evidence to make a recommendation for or against the use of stress testing.

If a stress test isn't recommended is there anything an asymptomatic person can do?

Absolutely.  Even though testing isn't the answer there is a lot we can do. It all comes down to controlling your risk factors. If you smoke, quit..NOW! If you have high cholesterol treat it with diet or medication to improve your numbers. If you have high blood pressure control that too. Get off the couch and exercise. Lose weight and reduce your alcohol consumption to one or two drinks per day. We know most of the risk factors for heart disease and although you can't pick your parents, or your sex, or stop the aging process, most of the other risk factors are things you can control.

Will controlling your risk factors guarantee that you won't have a heart attack? Of course not, but neither will a test. There are no guarantees in life, but if your real goal is to reduce the risk of a heart attack modifying your risk factors is the best way to improve your odds. Only you can do that by taking control of your risk factors before something happens.

Modifiable Heart Disease Risk Factors - Click on each one for assistance on controlling the risk factor.
Non-modifiable risk factors
  • Family history
  • Age
  • Gender



Michael Melgar

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