Heart Attack

What is a heart attack?

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The definition of heart attack is the slow or complete interruption of blood flow to the myocardium (cardiac muscle). A heart attack is technically known as MYOCARDIAL INFARCTION or for short MI. (MYO means muscle; CARDIO means heart; INFARCTION means death of the tissue).


As described earlier, the cardiac muscle receives its nutrients and oxygen supply from two arteries, namely the LEFT and RIGHT CORONARY ARTERIES. Each artery divides into several branches and each branch supplies a specific area of the cardiac muscle. The main cause of myocardial infarction is ATHEROSCLEROSIS, or hardening of the arteries, which is responsible for about 95 % of all heart attacks.

ATHEROSCLEROSIS and ARTERIOSCLEROSIS, this terminology is used interchangeably, but the following definitions are more accurate ARTERIOSCLEROSIS (ahr teer ee o’ skle ro’sis). Arteriosclerosis, the general term used for the process and damage of the arteries in general. ARTERIO means (artery) SCLEROSIS means (hardening or scarring).

ATHEROSCLEROSIS pronounced (ath”ur o”skle ro’sis). Atherosclerosis is the specific process of cholesterol and fat deposits on the inner side or inner wall of the artery, known as plaque deposits. It is by far the most common form of artery damage.

Figure 3-1 Schematic diagram of atherosclerosis formation in the coronary artery


Arteries are blood vessels that transfer blood away from the heart. Tissues and organs receive their supply of oxygen from oxygenated blood through arteries. If for any reason an artery

Arteries are blood vessels that transfer blood away from the heart. Tissues and organs receive their supply of oxygen from oxygenated blood through arteries. If for any reason an artery occludes, its share of blood to the organ it supplies stops, or significantly diminished. That organ will eventually die if that artery remains blocked, or suffers extensive damage.

Since, arteries travel long distances, under a certain amount of pressure generated by the heart, there anatomy differently to withstand that pressure. An artery is made of three layers (Figure 3-2),

Figure 3-2 Schematic illustration of the three layers of an artery. The intima, media and adventitia


1) Intima (inner surface and closest to blood) it releases a substance into the blood stream, preventing it from clotting.

2) Media (middle layer) it contains muscle fibers

3) Adventitia (outer cover), it contains nerve endings and minute arterioles that supply the artery itself

Atherosclerosis is a two-step process:

1. The damage of the specialized cells

2. The fats circulating in the blood infiltrate into the muscular layer of the artery. The muscle fibers become highly irritated, causing further damage.

Once the arteries are damaged this may lead to the damage of the tiny blood vessels that supply oxygen to the artery itself and this disruption may cause the blood cells to gather and stick together, Once the specialized layer of cells (endothelium) is damaged, they are dislodged, exposing the tissue of the middle layer (Media) to the blood stream. These cells are called PLATELETS they are very sticky cells; therefore, they collect at the site of injury within the artery. This leads to the formation of a clot(s) that may block the artery entirely (Figure 3-3).


Figure 3-3 to the arterial wall A = Damage to the endothelial cells. B = the exposed tissue attracts platelets from the blood. C = As large numbers of platelets collect in the injured area, blood clots may form, and may dislodge to travel in the blood stream eventually blocking smaller arteries causing a heart attack or a stroke. Pl = platelets, En = endothelial cells, D = site of damage, BC = blood clot.


Like hypertension, atherosclerosis also known as a ‘SILENT KILLER”.


When coronary arteries are affected by atherosclerosis, certain warning signals manifest themselves in the form of chest pain known, as ANGINA PECTORIS. Angina is an aching of the cardiac muscle itself, due to lack of oxygen. Angina Pectoris happens when the coronary arteries are becoming more and more narrowed. Usually angina occurs during some sort of physical activity such as climbing stairs, manual labor, as well as emotional excitement. Normally, the pain will subside shortly after the activity or excitement has stopped.

Anginal pain is usually a dull or pressing pain just beneath the sternum or breastbone. Some patients describe the pain as a “burning” or “squeezing” sensation, tightness or crushing pain. It is very common to see that the sufferer of anginal pain clenches his fist against his chest while describing the pain. Angina cannot be pointed out with one finger because it is diffuse in nature and is never a localized pain. (Figure 3-4)

Figure 3-4 Sites of anginal pain. 1 = Dull diffuse pain in the upper chest. 2 = Beneath the sternum, neck and mandible. 3 = Beneath the sternum, left shoulder and arm. 4 = Epigastric. 5 = Neck and mandible. 6 = Left shoulder and both arms


The above illustration shows the different place of the diffuse pain can manifest itself. Although the above six different sites of anginal pain are typical, a combination of these may very well happen.

Anginal pain usually disappears with rest but is better relieved with medication such as nitroglycerine. However, if pain persists, this might indicate that a heart attack might be eminent and the individual should seek immediate medical help by going to the emergency room for a complete cardiac evaluation.

ANGINA PECTORIS and MYOCARDIAL INFARCTION are two different conditions; however, both have the same underlying cause ATHEROSCLEROSIS. Angina pectoris is the REDUCTION of oxygen to the cardiac muscle causing pain. A myocardial infarction is the complete interruption of oxygen to the cardiac muscle. If this deficiency of oxygen is not reversed, the cardiac muscle will die. (Figure 3-5).

Figure 3-5 Schematic illustration of left coronary artery showing areas of narrowing a complete interruption of oxygen may lead to a heart attack. 1 = partially occluded coronary arteries, 2 = totally occluded coronary artery, 3 = distal to a totally occluded artery 2 will slowly fade away and eventually disappear.


Depending upon the severity of the blockage, you will learn how to avoid those activities that bring about angina, bear in mind, that it is how strenuously you do these activities, rather than how long, that causes angina. You might be able to walk a mile or more without any pain if you pace yourself, but will have severe pain if you walked rapidly and vigorously for only half a block. If certain activity prompts anginal pains such as mowing the lawn, housework, or sexual intercourse discuss the matter with your physician, he might prescribe or change the dosage of your medication.

Angina pectoris may take one of three forms:

1) Stable or Chronic angina. Stable angina is predictable, it occurs during some level of physical activity and/or emotional stress. The pain is a dull, crushing, tight, squeezing sensation just beneath the sternum and is not to one area. Shortness of breath, fainting, anxiety, and nausea may accompany the pain.

2) Unstable angina. It is more severe in nature than stable angina and usually precedes a myocardial infarction (heart attack). It is also known as pre-infarction angina


Myocardial infarction is an injury to the myocardium because of interruption of the blood supply to the area. Myocardial infarction is the main cause that leads to death.

Myocardial infarction normally happens in the left ventricle in four different locations (Figure 3-5)

1) SUBENDOCARDIAL INFARCTION This is the inner most area of the myocardium, and is closest to the cavity of the ventricle.

2) INTRAMURAL INFARCTION is an infarct that usually involves the middle area of the myocardium.

3) TRANSMURAL INFARCTION. The infarct usually involves the entire thickness of the myocardium, known as anterior, inferior, posterior, or lateral wall. Anterior wall myocardial infarction is the most severe; it affects large areas and may trigger arrhythmias.

4) SUBEPICARDIAL INFARCTION. The infarct usually involves the outermost area of the myocardium.

Figure 3-6 Different sites of myocardial infarct 1 = subendocardial infarction, 2 = intramural infarction, 3 = transmural infarction, 4 = subepicardial infarction. MV = mitral valve, TV = tricuspid valve, LV = left ventricle, RV = right ventricle, S = septum, P = papillary muscle.



The definition of congestive heart failure is the inadequate cardiac output, resulting in the retention of sodium and water. Congestive heart failure may develop because of a heart attack, valvular disease, and cardiomyopathy. This complication occurs when the damaged heart muscle can no longer pump an adequate volume of blood to the vital organs and the circulation is diminished resulting in the retention of fluids.

Fluid that collects in the lungs causes the patient to need more air to breathe and is usually the first symptom of heart failure.

Coronary artery disease, hypertension, valvular disease affects the left side of the heart. Therefore, primary failure frequently affects the left side. As blood backs-up in the pulmonary system, pressure build-up occurs, thus causing right side failure also. Fluid that collects in the lungs is seen on a chest X-Ray, and can be heard with a stethoscope. Like any other condition, certain risk factors intensify heart failure:

1) Infection, respiratory infection, the most common, others are less aggravating.

2) Pulmonary Embolism, clots in the lungs, these are the most common after infection.

3) Physical and Emotional stress, considerable strain such as a major surgical intervention or an unusual athletic effort or emotional strain may start heart failure.

4) Excessive intake of salts and fluids, heart failure is precipitated by additional intake of dietary salt or large amounts of water.

5) Certain types of drug


After a heart attack, the healing period may seem to pass very slowly because you are to cut down on a number of activities. Patients feel depressed, particularly if they are free of any symptoms, since they feel they can achieve a lot more. This process might take several months, with regular trips to your doctor. Lifestyle of patients will totally change


1) If you develop angina, shortness of breath, arm, or hand discomfort, stop, take some of your prescribed nitroglycerin, You should notify your physician, or go to the nearest emergency facility.

2) Space your activities to allow for your heart to rest Plan your work, rest if you are tired, pace yourself

3) If you do housework, follow these suggestions: Eliminate unnecessary tasks, clean one room at a time, do not move any furniture, make one side of the bed, try to sit down when ironing.

4) Avoid tensing your body, do not strain, do not lift any heavy objects.

5) Walk daily as much as you were waking at the hospital before your discharge.

6) Sex, like any other exercise, avoid sexual relations if you are: tired, just eaten, have been drinking, if you are angry, having chest pain

7) Long trip, check with your physician prior to taking a long trip,


After hospitalization because of a heart attack patient often, become depressed. They associate heart attack with some disabling disease and they think they are becoming invalid. This particularly happens to those who had been very active prior to their heart attack. They become anxious about whether they will be able to resume full physical, social, professional, and sexual activities. Usually there should be no worry if, of course, the patient follows the prescribed protocol of treatment, that is essential to full recovery. Like any other injury, it takes time for the healing process and, unless this period is followed carefully, recurrent heart attacks might follow. On the other hand, if the recovery period is followed normally, many patients never experience another heart attack again.