Why do heart tests sometimes disagree? A thicker heart muscle might be the surprising reason.

If you're being checked for a clogged heart artery, doctors might use two different tests: a stress MRI and a special X-ray called an angiogram. Sometimes, these tests disagree. The MRI might show a problem, but the angiogram looks normal. This can be confusing for both patients and doctors. This study looked at 354 people with suspected clogged arteries to understand why this happens. They found that people whose tests disagreed in this way—abnormal MRI but normal angiogram—had a thicker heart muscle than people whose tests both agreed everything was normal. The study also found a hint that these people might have more resistance in their tiniest blood vessels. The researchers conclude that a thicker heart muscle can potentially confuse the results. It might make the pressure reading from the angiogram look falsely normal, even when there is a problem. This means that for some people with a thicker heart muscle, a normal angiogram result might not tell the whole story.