It wasn't that Steve had any heart-related symptoms. He had no chest pain or shortness of breath. At 72 years of age, he still exercises vigorously and feels great.
However, he’s concerned about heart disease. Several family members, including his father, had heart attacks in their 50s, so Steve has had regular stress tests over the last 20 years to “make sure everything was ok."
Steve was initially surprised when I told him I didn’t think he needed a stress test (or any other heart testing for that matter). But once I explained what a stress test can determine, and what it can’t, he was comfortable with skipping it.
What is a Stress Test?
The most common type of exercise stress test is performed by having the patient walk on a treadmill (more rarely a bike is used). In this test, the workload (incline and speed of the treadmill) increases until the patient is not able to continue due to fatigue or there are alarming signs or symptoms like very high blood pressure or life-threatening heart rhythm problems. Before, during and after the stress test, the patient’s electrocardiogram (ECG), blood pressure, and symptoms are continuously monitored.
A stress test tells us how well blood is flowing to the heart. If a patient can only go a few minutes on a stress test and has chest pain and ECG evidence of ischemia (lack of blood flow to the heart muscle), it could mean that there’s an obstruction in their arteries, putting them at high risk for a cardiac event.
Why Should You Not Do a Stress Test?
It used to be common to do routine or even annual stress testing on patients who didn’t have symptoms. The idea was that heart attacks can occur suddenly and without warning, so it made sense to screen for unsuspected heart disease to possibly avoid problems in the future. However, routine stress testing has not been shown to lower the rate of heart attack or heart-related death. There are several reasons why:
- Heart attacks usually occur from rupture of artery plaque that, up until that rupture, had not been obstructing blood flow and, thus, would not be detected by a stress test. Every cardiologist knows of examples of patients who had a heart attack within months of a normal stress test. This likely does not mean the stress test was wrong. Stress tests cannot detect blockages in arteries unless they impair blood flow to the heart muscle, which typically occurs when a blockage is 70% or greater.
- There is no evidence that detecting and fixing artery blockages that are not causing symptoms, even if the blockage is greater than 70%, lowers the risk of future heart attack or heart-related death.This is a surprise for many and bears repeating. Opening arteries with stents in an acute heart attack DOES lower death rates, but opening arteries with stable blockages (like those detected by a stress test) has NOT been shown to lower death rates or heart attacks.
- Stress testing is not perfect. Like all tests, there are false positives and false negatives. And when an imperfect test is performed on a group with a low probability of disease, a positive test is more likely to be a false positive than a true positive. Because of this, a stress test that is being done "to make sure everything is ok" can lead to harm by exposing the patient to unnecessary and potentially risky procedures like heart catheterization.
Based on this information, the U.S. Preventive Services Task Force and American College of Cardiology recommends to NOT do exercise treadmill testing in patients without symptoms who are low risk for heart disease.
When to Do a Stress Test?
The most common reason doctors recommend stress testing is to evaluate symptoms, typically chest pain or shortness of breath. Depending on the nature of the symptoms and the patient’s heart disease risk, an exercise treadmill test may be the best way to gather further information to either make a diagnosis or risk stratify the patient for possible invasive procedures like a heart catheterization. Other reasons to do stress testing may include assessing a very high risk sedentary patient who is having a high risk surgery or to guide an exercise prescription for a sedentary patient who wants to begin an exercise program.
The decision to do a stress test is complicated and depends on many factors. It is best made between a patient and their physician or healthcare professional where options, alternatives and patient preferences are discussed in a patient-centered approach.
BY R. TODD HURST, MD, FACC