UK researchers say they have found a new way to tell if a heart attack is more severe and might cause lasting harm - by looking for bruising or bleeding in the heart muscle.
Patients with this sign on scans more often develop serious problems like heart failure, says the Glasgow team.
It's hoped the discovery could help with preventing such complications.
Half a million UK people have heart failure and heart attacks are the leading cause.
Heart failure can leave people unable to do simple everyday tasks, such as climbing the stairs.
Symptoms occur because the damaged heart doesn't have enough strength to pump blood around the body efficiently.
This makes the person breathless, tired and, untreated, means fluid can gather in the legs and lungs.
There are drugs that can help, but these have to be taken long-term.
Some people with heart failure may need heart surgery too.