When I first started working in cardiac rehabilitation as a new college grad, one of my Phase 3 cardiac rehab patients had a heart attack when he was only 35 years old. If that wasn’t unsettling enough, he had his heart attack the DAY AFTER he “passed” his treadmill test. Back then, I couldn’t understand how that could possibly happen, but I now know better.
How Sensitive Is Your Treadmill Test?
Here’s what you need to know. Currently, the exercise ECG is the most cost-effective first-line screening tool, but its accuracy relies on the ‘sensitivity’ of the test. Sensitivity refers to the percentage of cases in which exercise testing accurately identifies the presence of coronary artery disease (CAD). Unfortunately, the exercise ECG it is not 100% sensitive to detecting coronary artery disease.
Per the American College of Sports Medicine, the current sensitivity for detecting CAD using the exercise stress test is only about 70%. In other words, if you test 100 cardiac rehab patients with documented coronary artery disease, only 70 patients would show evidence of CAD per the stress ECG test. If you’re one of the 30 remaining patients, where does that leave you?
Well, don’t start your celebratory dance (or meal) just yet. It just means that you may fall in either of the following groups:
- You have a negative stress test. That is, you actually “passed” and show no signs of coronary artery disease.
- You have a false-negative finding. This means you’ve been given a negative stress test result (normal) where no CAD ‘appears’ to be present, but you actually have CAD.
The bottom line… a negative exercise ECG test is no guarantee that you do NOT have coronary artery disease (CAD) even if your cardiologist tells you, “Everything looks great! See you in a year.” So sorry to burst your bubble, but that’s the reality. Cardiac events that occur after a negative stress test happen all too often, but it’s not so perplexing to me anymore.
Causes of False-Negatives (Lower Sensitivity)
Stress test results are only as valuable as your performance, the technician’s monitoring, and the test interpretation. Here are some factors that may increase your chances of a false-negative finding: Continue reading “Be Aware If You Passed Your Treadmill Stress Test”