Throughout the ages, both in psychological and spiritual terms, the human heart is linked to emotions which may be so. It is primarily a mechanical muscle pump which contracts and pushes blood into the circulation to supply oxygen and nourishment to all our body systems. It pumps blood into the arterial blood channels of our body. The blood vessels are channels or tubes that carry blood to and from all our organs such as the brain, kidneys, lungs, heart muscle, skeletal muscles, stomach, intestines, skin , etc.

The heart’s muscle, like any other muscle, would require its own supply of oxygen and nourishment. Its own quota for self is obtained through an exclusive set of arterial channels which originate from the mouth of the arota. These special tubes travel the surface of heart as if embracing it. These are shaped like a "corona" (crown), hence the name coronary arteries. The term was coined by Galen, the great Roman anatomist and physician, in the second century A.D. The pencil-sized coronary arteries originate from the principle arterial trunk known as aorta. The main trunk aorta, of course, arises from the left ventricle. There are three main coronary arteries and like the branch of a tree, each main coronary artery divides and subdivides to transport oxygenated blood to all cells of the heart muscle. The smallest branches often interlink with one another and form what are known as collaterals.

The names of three principal coronary arteries are :

1. Left anterior descending artery
   
2. Left circumflex artery
   Both above arteries branch off from a small common stem known as the Left Main. The left main, after a short path, divides into the major left anterior ascending and circumflex artery. The main stem artery arises from the left side of the base of arota.
   
   
   
3. Right coronary artery is also a principle artery and arises from right side of the mouth of the arota.

A " heart attack " is commonly caused by sudden occlusion or blockage of the lumen in one of the primary branch of coronary arteries or its large sub-branches. The blockage is caused by formation of a blood clot within the lumen of artery. The medical terms used for a major "heart attack" are coronary thrombosis or myocardial infarction. The clot in the coronary artery usually occurs when the inner lining of the coronary channel becomes thick, rough and uneven from atheroma. However, like all other tissues and organs of the body, heart too has a remarkable ability to repair itself after myocardial infarction.

When a bone is fractured or broken, it heals. Similarly, an injured heart can also form a firm and healthy scar, with a near complete restoration of the heart’s muscle strength. This happens in a good majority of patients.

With a complete blockage at a given location, the blood cannot flow further to supply that dependent area of the heart muscle, which cannot receive its own oxygen and nourishment for its survival. With a complete loss of blood supply, this dependent area of the heart muscle dies - this disease goes by the name of acute coronary thrombosis or acute myocardial infarction.

There are two other disease patterns that can manifest through partial obstruction of the coronary arteries. They are termed as 1. Chronic Stable Angina and 2. Acute Unstable Angina. Their mechanism will be discussed in later pages. The diagrammatic figures are given for understanding of coronary artery parthology in a simplified way.

Progress Of A Therosclerosis Of The Arteries As Shown In Diagrams From A To D

The middle coronary artery shows atheroma in its inner lining. The internal wall of coronary artery becomes thick, rough, narrow doe to deposits of fat like substances known as cholesterol. In this state, however, a person still feels normal and healthy because the other "side arteries " (B) known as collateral feeders manage to reach an adequate supply of blood to the heart muscle. The start of this fatty precipitate can initiate from very childhood and can steadily expand to obstruct our arteries more and more. It ordinarily takes 20 years or more to reach the stage C or Stage D. This stage is also known as " Silent ischemia. "

Coronary atheroma progresses to other side branches. Heart muscle becomes ischemic. It receives less blood. With increasing obstruction or narrowing and with failing collaterals the blood supply becomes less than required. This phase is called ischemia, angina or insufficiency. In this situation the heart muscle suffers from lack of adequate supply. The muscle, however, gets sufficient enough blood for the heart muscle to retain its viability. With complete occlusion by a blood clot in one of the blocked coronary arteries with the poor collaterals would give a necrosed muscle known as a myocardial infarction.

The blockage usually occurs due to clotting of circulating blood in the lumen of artery which has already become rough and narrow and crusty in its inner lining. The areas or the segment of heart muscle supplied by this blocked coronary branch gets practically no oxygen and hence gets completely damaged and non-viable. This destroyed area can be repaired by nature if proper time, rest and medicines are given.

There is another mechanism which is more common. Even with minimal atheroma a sudden crack with local bleeding due to some unknown reasons can develop to give acute coronary syndromes such as acute unstable angina or myocardial infarction as shown in the diagram.

• Simple crack fissure in a less blocked artery.
  
• Acute unstable Angina.
  
• Complicates into acute infarction.