Because we’ll return often to the way the heart works when it’s well and doesn’t work when it’s damaged, here’s an anatomy lesson about the heart and the circulation system that feeds and flows from it.
You know that the heart is a muscle-the muscle. Like all muscles it needs oxygen-enriched blood to function effectively. Deprived of blood, the heart, like any other muscle, suffers. That suffering can be more or less extreme. If the blood flow is decreased so that the heart starves for blood but is still sufficiently alive to function, the condition is called ischemia, which simply means a deficiency of blood flow. The more extreme case of heart attack, or myocardial infarction, means that the flow of blood has been so impaired that the heart, literally starving for blood, is dying.
Now let’s look at this in a little more detail. The heart is divided into four chambers: two upper chambers and two lower ones. The upper chambers are called the right atrium and the left atrium. The lower chambers are the right ventricle and the left ventricle. Blood enters the heart through the right atrium. All the blood in the body, from the tip of your toes to the top of your head, usually passes through the right atrium.
From the right atrium, it passes to the right ventricle, the second chamber, where it is pumped into the pulmonary arteries that channel the blood up into the lungs. When we breathe, we take in oxygen that is delivered to the blood pumped from the right ventricle into our lungs. Once that blood, now enriched with oxygen, is ready to leave the lungs, it goes into the third chamber called the left atrium, and from there it goes to the left ventricle. That fourth chamber has the crucial function of pumping the blood into the aorta-the major blood vessel coming off the heart that supplies blood to every other artery in the body.

The aorta, because it feeds all these secondary arteries, is responsible for supplying the oxygen-rich blood and nutrients to every organ of the body. It does this by means of branches, the aorta resembling the trunk. The branches, or arteries, feed our muscles, tissues, and organs. This is possible through a system of capillaries, which are narrower tubes that transfer blood from the organs to their destinations. It is from the capillaries that the muscles, tissues, and organs extract the oxygen and nutrients they need to function properly.

Once that extraction has occurred, the blood travels from capillaries into veins. These veins carry the blood to the larger veins called the superior vena cava and the inferior vena cava. And, if you get the gist, you’ll have guessed that those large veins carry the blood back to the first chamber of the heart, the right atrium, where the process begins again.

To review, blood already drained of oxygen and nutrients comes into the heart, where it is resupplied with oxygen, then pumped through the left atrium to the left ventricle, and out through a major highway of the heart-that is, the major artery-called the aorta. The aorta disperses blood throughout the body and into small sidestreets (also called arteries) that deliver blood, by way of capillaries, to the tissues, muscles, and organs. There, the oxygenated nutrients are extracted and the blood is carried through the veins back to the right side of the heart.

There are two last details: first, coming off the aorta are two arteries-the right coronary artery and the left coronary artery. An Introduction to Coronary Artery Disease 11 As their names indicate, the right coronary artery supplies the right side of the heart with blood and the left coronary artery supplies the left side of the heart with blood. When these arteries become clogged, the result can be angina or a heart attack. Second, as the drawing makes clear, the aorta divides into two other arteries called the carotid arteries. When the carotid arteries become blocked, the result will be a stroke.
The good news is that not all, or even most, heart attacks are fatal. If you suffer one, you have a good chance of recovery if you get prompt and appropriate treatment. But, as with other problems, this one is far better nipped in   fi II  Once there has been a heart attack, even if it isn’t fatal, damage has been done to the heart itself, and repair of, and recovery from, that damage is far more difficult than taking preventive measures to avoid the problem. As to the chances of recovering from a stroke, fully or partially, that depends on how much damage was done. The more serious the stroke, the more likelihood of coma or death. In the case of minor strokes, the chance for recovery is good.