What is Stroke?

A stroke, also known as cerebrovascular accident (CVA), is the rapid loss of brain functions due to the lack of blood flow caused by blockage such as thrombosis, arterial embolism and hemorrhage. When the blood vessels get clogged, the brain cells become deprived from nutrients and oxygen as there is no blood supply. Eventually, that part of the brain starts to die. A stroke occurs. The results of having stroke are impairments in memory, speech ability and physical mobility.

 According to National Stroke Association of Malaysia, stroke is the third largest cause of death in Malaysia.

The types of stroke is divided into three:

• Ischemic stroke-It is main type of stroke. It is due to blockage of blood vessels supplying the brain.
• Hemorrhagic stroke-It is due to bleeding into or around the brain.
• Transient ischemic stroke(TIA)- A mini-stroke

Images are from Google Images
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Stroke is the third largest cause of death in Malaysia. Only heart diseases and cancer kill more. It is considered to be the single most common cause of severe disability, and every year, an estimated 40,000 people in Malaysia suffer from stroke. Anyone can have a stroke, including children, but the vast majority of the cases affect adults. - National Stroke Association Malaysia

References:

1. http://www.strokeassociation.org/STROKEORG/AboutStroke/Types-of-Stroke_UCM_308531_SubHomePage.jsp
2. http://en.wikipedia.org/wiki/Stroke

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What is coronary heart disease(CHD)?

Coronary heart disease is also known as coronary artery disease(CAD). This disease is caused by the narrowing of the small blood vessels that supply blood and oxygen to the heart. It is a major cause of illness and death. 


 Coronary heart disease is generally caused by atherosclerosis - when plaque (cholesterol substances) accumulates on the artery walls, causing them to narrow, resulting in less blood flow to the heart. Sometimes a clot may form which can obstruct the flow of blood to heart muscle. Coronary heart disease commonly causes angina pectoris (chest pain), shortness of breath, heart attack (myocardial infarction) and other symptoms. 


 The coronary arteries are called so because they encircle the heart like a crown (corona in Latin means crown). 


Statistics
 According to the National Institutes of Health (NIH), USA, coronary heart disease is the leading cause of death for males and females in the USA. 17.6 million Americans were thought to have had the condition in 2006. It caused the death of over 425,000 people in the USA in 2006. 


 According to the National Health Service (NHS), UK, coronary heart disease causes the death of 1 in every 4 men and 1 in every 6 women in the United Kingdom - it is the UK's biggest killer. The risk of developing the disease increases with age. More males are affected than females.


References :
http://www.medicalnewstoday.com/articles/184130.php

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What is Atherosclerosis?

Atherosclerosis (also known as arteriosclerotic vascular disease or ASVD) is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol. It is a syndrome affecting arterial blood vessels, a chronic inflammatory response in the walls of arteries, caused largely by the accumulation of macrophage white blood cells and promoted by low-density lipoprotein ( LDL-C - plasma proteins that carry cholesterol and triglycerides) without adequate removal of fats and cholesterol from the macrophages by functional high-density lipoproteins (HDL-C). It is commonly referred to as a hardening or furring of the arteries. It is caused by the formation of multiple plaques within the arteries.

The atheromatous plaque is divided into three distinct components:

1. The atheroma ("lump of gruel," from ἀθήρα, athera, gruel in Greek), which is the nodular accumulation of a soft, flaky, yellowish material at the center of large plaques, composed of macrophages nearest the lumen of the artery
2. Underlying areas of cholesterol crystals
3. Calcification at the outer base of older/more advanced lesions.

Reference:

http://en.wikipedia.org/wiki/Atherosclerosis

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Arterial Plaque

Cross section showing an artery with plaque

Arteries are blood vessels that carry blood rich in oxygen throughout your body. They go to your brain as well as to the tips of your toes. Healthy arteries have smooth inner walls and blood flows through them easily. Some people, however, develop clogged arteries. Clogged arteries result from a build-up of a substance called plaque on the inner walls of the arteries. Arterial plaque can reduce blood flow or, in some instances, block it altogether.

Clogged arteries greatly increase the likelihood of heart attack, stroke, and even death. Because of these dangers, it is important to be aware, no matter how old you are, of the causes of artery plaque and treatment strategies to prevent serious consequences.

What causes arterial plaque?

Plaque that accumulates on the inner walls of your arteries is made from various substances that circulate in your blood. These include calcium, fat, cholesterol, cellular waste, and fibrin, a material involved in blood clotting. In response to plaque build-up, cells in your artery walls multiply and secrete additional substances that can worsen the state of clogged arteries.

As plaque deposits grow, a condition called atherosclerosis results. This condition causes the arteries to narrow and harden.

Although experts don’t know for sure what starts atherosclerosis, the process seems to stem from damage to the arterial wall. This damage, which enables the deposition of plaque, may result from:

• High “bad” cholesterol and low “good” cholesterol - High levels of “bad” cholesterol, or low-density lipoprotein (LDL), are major contributors to arterial plaque formation. But that doesn’t tell the whole story. Everyone also has “good” cholesterol, or high-density lipoprotein (HDL), circulating in the blood. HDL is believed to remove some of the bad cholesterol from plaque in clogged arteries and transport it back to the liver where it is eliminated.
• High blood pressure - Having high blood pressure increases the rate at which arterial plaque builds up. It also hastens the hardening of clogged arteries.
• Cigarette smoke - Cigarette smoke seems to increase the rate of atherosclerosis in the arteries of the heart, legs, and the aorta -- the largest artery in the body.

Plaque often starts to develop during the childhood or teenage years. Then clogged arteries develop in middle age or later.

What are the dangers of arterial plaque and clogged arteries?

It depends on where arterial plaque accumulates. Clogged arteries in different parts of the body can lead to multiple medical conditions, including:

• Coronary artery disease - When plaque accumulates in the arteries carrying blood to the heart, it results in coronary artery disease, or heart disease. This condition can lead to heart attacks and is one of the leading causes of death in the United States.
• Carotid artery disease - The carotid arteries run up either side of your neck. They supply oxygen to your brain. The accumulation of arterial plaque in the carotid can lead to stroke.
• Peripheral artery disease - If plaque builds up in the blood vessels that carry blood to your legs, it can reduce the amount of oxygen delivered. The reduced blood flow can cause you to experience pain, numbness, or serious infection in your legs and feet.

Source:

http://www.webmd.com/heart-disease/clogged-arteries-arterial-plaque

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The Coronary Arteries

The Heart and Coronary Arteries
Patrick J. Lynch, medical illustrator

A coronary artery is one of two blood vessels that branch from the aorta close to its point of departure from the heart and carry oxygen-rich blood to the heart muscle. Both arteries supply blood to the walls of both ventricles and to the partition between the chambers. The right coronary artery supplies blood to the right atrium, while the left supplies the left atrium. Blockage of any branch of the coronary arteries causes death of a portion of the heart tissue when it is deprived of oxygen-rich blood (see coronary heart disease).

Function

The coronary arteries supply oxygenated and nutrient filled blood to the heart muscle. There are two main coronary arteries: right coronary artery and left coronary artery. Other arteries diverge from these two main arteries and extend to the bottom portion of the heart.

Coronary Arteries: Branches

 Some of the arteries that extend from the main coronary arteries include:

Right Coronary Artery - Supplies oxygenated blood to the walls of the ventricles and the right atrium.

Posterior Descending Artery - Supplies oxygenated blood to the inferior wall of the left ventricle and the inferior portion of the septum.

Left Main Coronary Artery - Directs oxygenated blood to the left anterior descending artery and the left circumflex. 

Left Anterior Descending Artery - Supplies oxygenated blood to the anterior portion of the septum as well as to the walls of the ventricles and the left atrium (front region of the heart). 

Left Circumflex Artery - Supplies oxygenated blood to the walls of the ventricles and the left atrium (back region of the heart).

Source :

http://biology.about.com/od/anatomy/ss/Coronary-Arteries.htm

http://www.britannica.com/EBchecked/topic/138249/coronary-artery

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Understanding the Heart

The Size

A human being's heart is about the size of that human being's fist. As the body develops, the heart grows at the same rate as the fist. So an infant's heart and fist are about the same size at birth. In the womb, however, that similarity was not always true. During the first few weeks after conception, the fetal heart occupies most of the fetus' mid-section. The heartsize to bodysize ratio is nine times greater in the fetus than in the infant. During those first few weeks, the fetal heart lies high in the chest. Soon, it moves down to occupy its position in the chest cavity. 

Structure of the Human Heart

The heart you see drawn on the average Valentine is only a rough representation of the actual structure of the heart. Your heart is actually shaped more like an upside-down pear.

Source : http://www.ynhh.org/heart-and-vascular-center/heart_works.aspx?source=/cardiac/heart/index.html

The human heart is primarily a shell. There are four cavities, or open spaces, inside the heart that fill with blood. Two of these cavities are called atria. The other two are called ventricles. The two atria form the curved top of the heart. The ventricles meet at the bottom of the heart to form a pointed base which points toward the left side of your chest. The left ventricle contracts most forcefully, so you can best feel your heart pumping on the left side of your chest.

The left side of the heart houses one atrium and one ventricle. The right side of the heart houses the others. A wall, called the septum, separates the right and left sides of the heart. A valve connects each atrium to the ventricle below it. The mitral valve connects the left atrium with the left ventricle. The tricuspid valve connects the right atrium with the right ventricle.

The top of the heart connects to a few large blood vessels. The largest of these is the aorta, or main artery, which carries nutrient-rich blood away from the heart. Another important vessel is the pulmonary artery which connects the heart with the lungs as part of the pulmonary circulation system. The two largest veins that carry blood into the heart are the superior vena cava and the inferior vena cava. They are called "vena cava" because they are the "heart's veins." The superior is located near the top of the heart. The inferior is located beneath the superior.

View the structure of a preserved heart here.

How It Works

• Deoxygentated blood returning to the heart from veins all over the body flows into the right atrium via the vena cava.
• From there the blood flows into the right ventricle, which pumps it out to the lungs for oxygenation via the pulmonary vein.
• The oxygen-rich blood returns to the left atrium by the pulmonary artery.
• From there the blood flows into the left ventricle, which pumps it at high pressure into the arteries.

This entire process constitutes one heartbeat.

The pumping, or contraction, of the left ventricle must be very powerful because that is what keeps the blood flowing throughout the body.

The strength of the heart muscle depends on the oxygen and nutrient supply coming via the coronary arteries.

These arteries are usually strong, elastic, and quite flexible.

References :
http://www.fi.edu/learn/heart/

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