Dear Jack,
When I go to the veterinarian for a checkup, one of the first things they do is listen to my heart. They want to make sure it’s healthy because it pumps blood to my whole body.
I asked my friend Zhaokang Cheng about heart attacks. He’s a scientist at Washington State University. He works on new medicines to help people who have heart attacks or heart disease.
He told me that a heart attack happens when a big blood vessel that delivers blood to the heart gets blocked. Those blood vessels are called coronary arteries.
They get blocked when fatty gunk and other stuff build up on the walls of the arteries. Over time, the buildup can get thicker and harder. It can make the space inside the artery very narrow, so there isn’t much room for blood to get through. Or it can block the artery completely.
Sometimes a piece of the buildup can break off or a chunk of blood called a clot can clog up a narrow artery. It’s like how a pipe can get clogged with gunk so the water can’t get through.
A blocked coronary artery can stop the blood from getting to the heart. There’s just no way for it to get past the clog. That’s bad news because blood carries oxygen and nutrients that the heart needs to work.
The part of the heart that doesn’t get blood during a heart attack is called the ischemic region.
“Depending on where the blood vessel is blocked, the region that does not have blood supply can be small or really big,” Cheng said. “If the ischemic region is very large, a lot of the heart muscle does not have blood supply. That can be a critical situation because that means a lot of the heart muscle cells are dying.”
Most cells in the body die and get replaced by new ones all the time. But heart muscle cells are different. The heart muscle cells you have as a kid are the same ones you’ll have your whole life. If some of them die, the body has a very limited ability to make new ones.
“After a heart attack, that ischemic region is replaced by scars,” Cheng said. “That’s why large heart attacks are very dangerous. A major part of the heart is replaced by scars—and the scars cannot contract.”
When the veterinarian or doctor listens to your heart, the heartbeat they hear is caused by the heart muscle cells contracting. It pushes blood out of the heart to the other organs of the body. That’s how all those organs get the oxygen and nutrients they need to work.
A large heart attack prevents the heart from getting enough blood. It also damages all the other organs that don’t get enough blood, too.
That’s why it’s super important for someone who’s having a heart attack to get to the hospital fast. If doctors can get blood flowing to the heart again right away, fewer heart muscle cells will die. That means blood will get to all the other organs more quickly, too.
Once the blood is flowing normally again, that’s A-positive situation for the whole body.
Sincerely,
Dr. Universe