About Coronary Artery Disease
How does a normal heart function?
The heart is a pump distributing the blood throughout the body. The right side of the heart receives venous blood ("dark" or blue blood), which comes from all over the body, and propels it towards the lungs, where it is enriched with oxygen and becomes the 'red blood'.
Each side of the heart has two chambers: one receiving the blood, called the atrium, and an pumping chamber, called the ventricle. The ventricles have a thick muscular wall, the myocardium, which contracts regularly (at rest, at a rate of 60 to 70 times a minute) to pump the blood towards the various organs; as the blood flows in the arteries, it produces a characteristic beat called the heart rate or pulse.
For an adequate work, the heart like all other organs, receive oxygen-rich blood. This blood is brought to the heart through the coronary arteries, which are the first branches of the initial aorta. They are called coronary because they are placed like a crown around the heart. In a normal heart, the coronary arteries provide a normal supply of blood to the myocardium and thus the myocardium and valves function properly.
What happens when you have coronary artery disease?
To function, the heart needs energy and oxygen, supplied by the blood from the coronary arteries. There are 2 coronary arteries : the right and the left, with the left subdivided in two major branches. Coronary artery disease occurs when one or more of these arteries is partially obstructed by atherosclerotic plaques. Angina pectoris may occur when the artery is blocked and when the diameter is reduced by less than 50%. During exertion, the body needs more oxygen and the cardiac output is increased. If the coronary arteries are occluded, the supply to the heart becomes insufficient, for example during exercise, and the cardiac output cannot increase to satisfy the need in blood and oxygen of the tissues.
- The area supplied by blocked coronary arteries suffers from ischemia: Ischemia is created by the imbalance between myocardial oxygen demand and myocardial oxygen supply. During angina pain on effort (the common form of angina pectoris) myocardial oxygen demand is increased but the coronary arteries blockade does not permit to increase adequately the flow, creating the imbalance and thereby ischemia.
- The atherosclerotic plaque may rupture and this leads to a clot which completely or sub totally occludes the artery: the pain then occurs when the person is at rest: this is unstable angina, an acute coronary syndrome.
- Coronary artery disease is a chronic disease but with acute episodes related to atherosclerotic plaque rupture. When the vessel is completely occluded by a clot, the area supplied by this particular vessel is deprived of blood and oxygen. The muscle cells rapidly die and a necrosis occurs in this territory: this is myocardial infarction (heart attack).
- The short and long-term prognosis of a myocardial infarction is depending on the size of the necrotic area.
What causes coronary artery disease?
The cause of coronary atherosclerosis is multifactorial.
Very simply, it might be related to a wall aggression (Tobacco, spasm, hypertension) appealing the deposition of fats and finally fibers healing this area; However, we very well know the factors able to favor the development of coronary artery disease.
A risk factor is quite simply a personal characteristic increasing the likelihood to develop a cardiovascular event.
Risk factors have been identified by epidemiological studies looking at lifestyle (smoking, exercise, diet) and state of health (weight, blood pressure, cholesterol) of many people based on questionnaires and medical examinations. These people were then followed up for several years to detect the occurrence of cardiovascular events.
What are the identified cardiovascular risk factors?
According to guidelines from scientific societies (such as the European Society of Cardiology), there are factors that can be modified and others that cannot:
Non-modifiable risk factors
- Age: the older you get, the greater your risk
- Family history: your risk is higher if your parents, grandparents, or brothers and sisters suffered a cardiovascular event at a relatively young age (under 55 for men and under 65 for women).
- Medical background
- Gender
- Ethnic background
Modifiable risk factors
You can reduce three of these risk factors yourself:
- Smoking: smoking considerably increases your risk (not only of a cardiovascular event, but also of lung cancer, cancer of the mouth or larynx, cervical cancer, and bladder cancer).
- Increased cholesterol: a high level of cholesterol in the blood clearly increases the risk of a future cardiovascular event.
- A sedentary lifestyle: people who do not regularly practice a physical activity such as taking a brisk walk at least once a week, have a shorter life expectancy than those who are physically active.
For some modifiable risk factors, you will also need the help of your doctor:
- Hypertension (raised blood pressure)
- Diabetes
- Obesity
- Increased cholesterol
References
Collins P, Fox KM. Pathophysiology of angina. Lancet. 1990; 1: 94-96
Fox K, Borer JS, Camm J, Danchin N, Ferrari R, Lopez Sendon JL, Steg PG, Tardif JC, Tavazzi L, Tendera M. Resting heart rate in cardiovascular disease. JACC. 2007;50(9):823-830.
Graham, I., D. Atar, et al. (2007). "European guidelines on cardiovascular disease prevention in clinical practice: executive summary." Eur Heart J 28(19): 2375-414.