Dear Dr. Toshi,
What's a heart attack and how does it happen?
What's commonly known as heart attack is also called a "myocardial infarction" (MI). The heart is a muscular organ, and its muscle is called myocardium. Infarction is the death of the myocardium, and it's caused by coronary artery disease.
Coronary artery disease is a disease of arteries that carry oxygenated blood to the myocardium muscle. This is confusing because, well, you may ask, the heart pumps the blood, so what are these arteries that pump blood to the myocardium?
So, let's talk about the heart a little today. As you know, the heart sits a little to the left of the center of the chest for most people. It's a pump that pumps the blood. You might be surprised to hear that it's actually two separate pumps: one on the right side of the heart, and another on the left side. Each side has two chambers, or rooms. Interestingly, the blood going through the chambers on one side doesn't mix at all with the blood in the other side; they're completely separate systems.
Here is how it works. The left side of the heart pumps oxygen-rich blood out to your body. Then the oxygen-depleted blood comes back from the body to the right side of the heart. Then the right side of the heart pumps the blood to the lungs, where it gets oxygenated. That's right. The right side of the heart is actually connected to the lungs! That oxygen-rich blood from the lungs then goes to the left side of the heart and gets pumped out to the body again. So, the heart is actually two pumps: the left one pumps blood to the body, and the right one pumps blood to the lungs.
The left side of the heart pumps oxygen-rich blood out to the body through a large artery called the aorta, which is about the size of a garden hose. So, the aorta is the first and largest blood vessel in your body. Right where the aorta comes out of the heart, some smaller arteries branch out from the aorta. They are the coronary arteries that wrap around the outside of the heart to supply oxygenated blood to the heart muscle itself. The blood that's pumped through the heart chambers is completely separate from the blood in the coronary arteries.
Coronary artery disease is when fat- and cholesterol-rich plaque builds up on the inside walls of the arteries and narrows or blocks the flow of blood through the coronary arteries. This plaque buildup is called atherosclerosis. When this happens, the heart muscle doesn't get enough blood, oxygen, and nutrients, and that causes the heart muscle to cramp up (which is called ischemia) or even die (infarction). That's a heart attack.
The most common symptom of coronary artery disease is chest pain, which is called angina. This pain can also be felt in the upper back, shoulder, jaw, neck and arm. Some people, especially women and elderly people, may have symptoms other than chest pain, such as shortness of breath, palpitations (racing or pounding of the heart), irregular heartbeat, sweating, nausea, and dizziness.
So, if you ever have symptoms like these, don't wait, be sure to call 911 right away.
Dr. Toshiko ("Toshi") Luckow, MD, is a Family Physician at the West River Health Services Hospital and Clinics.