Infective endocarditis is a big word that means a bad infection that can happen in your heart.
Inside your heart, there are little doors that open and close to let your blood flow in the right direction. But sometimes, little germs called bacteria can stick to these doors and make them not work so well.
When that happens, the bacteria can grow and make even more germs. They might even form a little colony that sticks to your heart like a spiderweb.
This is bad because it can hurt your heart and make it not work as well. Plus, if little pieces of the colony break off and travel through your blood, they can cause problems in other parts of your body, like your brain or your kidneys.
So if you ever feel sick or have a fever, it's important to tell a grown-up so they can help you get better. They might give you medicine to kill the bacteria and make sure your heart and the rest of your body stay healthy.