(What it is, the process and the risk factors)
By: Dr Eugene Nwosu MBBS, FACC, FACP, FAHA Chief Medical Director
Coronary Artery disease (CAD) can be defined as the buildup of plague that clog up the inside of blood vessels supplying blood to the heart muscles. These vessels are referred to as coronary arteries. The process of coronary artery disease (also called atherosclerosis) starts with endothelial dysfunction (damage to the endothelium). The endothelium is the thin membrane lining the inside of the blood vessels. Most risk factors for CAD cause endothelial dysfunction.
Small plaque buildup that occupies less than 70% of the cross sectional area of the coronary vessels typically have no symptoms, but they are the usual cause of sudden cardiac death (cardiac arrest) and acute heart attack by the process of plaque rupture. Plaque buildup of greater than 70% of the cross sectional area of the coronary arteries can cause angina, which is defined as chest pain, tightness or heaviness that is brought on by exertion. Emotion stress can also cause angina.
Other names that are used to describe coronary artery disease are heart attack, myocardial infarction, angina, atherosclerosis and cardiovascular disease.
Effects of Plaque Buildup.
The two most dreaded effect of plaque buildup are sudden cardiac death or cardiac arrest and acute myocardial infarction (Heart Attack). Plaque buildup can also result in angina pectoris and congestive heart failure.
Angina Pectoris is chest pain that occurs with effort or activity. This arises from decreased blood supply to the heart muscles from a fixed plaque. The blood supply to the heart muscles at resting state is adequate to meet the need of the heart but with exercise, the supply becomes inadequate. Angina therefore occurs as a result of supply and demand mismatch. Sometimes buildup of significant plaque over the years may affect coronary vessels depriving the heart muscles adequate supply of blood and nutrients. This results in weak heart muscles and heart failure.
Heart Failure is defined as the inability of the heart to meet the demands of the body. The heart is unable to pump blood at an adequate rate or in adequate volume.
Plaque rupture is like volcanic eruption: Unpredictable and can be catastrophic
Why Coronary Artery Disease is Important.
Coronary artery disease affects all. No race, nationality or gender is exempt. It is the commonest cause of sudden death, “Most Sudden Death in Nigeria is not Juju, it is Heart Attack.” The incidence in Nigeria and the developing world is on the rise because of several factors, including changing life styles and diet, increasing obesity and diabetes epidemics among others. The process of atherosclerosis starts early in childhood and it takes a couple of decades to build up plaques.
In order to reduce the incidence of coronary artery disease related mobility and mortality we must recognized the risk factors and take action to modify those risk. The more the number of risk factors someone has, the higher his or her risk of developing Coronary Artery Disease.
Risk Factors For Coronary Artery Disease.
1. Family History: If your sibling, parents or grandparents have had early heart attacks by age 55 for male relatives and by age 65 for female relatives you may be at increased risk.
2. Age: is a recognized risk of CAD: incidence increases in men from age 45 or older and for women age 55 or older. Risk of CAD is very high in elderly population 75 and older.
3. Sex: Incidence of CAD is higher in males but women’s risk increase after menopause, when the protective effect of estrogen is lost
4. Hypertension: HTN is a significant risk for CAD. HTN occurs at younger age in people of African descents and is often more severe. HTN is a silent killer because for most people, it does not have any symptoms. It is imperative that the diagnosis is made and appropriate treatment to goal is achieved.
5. Diabetes Mellitus: is a significant risk for CAD and the risk is considered heart attack equivalent.
NHS study in England and Wales found significant increase in Cardiovascular Disease in Diabetes
i. 48% increased risk of heart attack.
ii. 65% increased risk of heart failure.
iii. 25% increased risk of stroke
iv. 71% increased risk of angina.
6. Smoking: Smoking and long term exposure to second hand smoke increase the risk of heart attack.
i. Smoking increases blood pressure, decreases exercise tolerance and increases the tendency for blood to clot. Smoking also increases the risk of recurrent coronary heart disease after bypass surgery.
ii. Cigarette smoking is the most important risk factor for young men and women. It produces a greater relative risk in persons under age 50 than in those over 50.
iii. Women who smoke and use oral contraceptives greatly increase their risk of coronary heart disease and stroke compared with non-smoking women who use oral contraceptives.
iv. Smoking decreases HDL (good) cholesterol. Cigarette smoking when combined with a family history of heart disease also seems to greatly increase the risk.
7. Cholesterol: High cholesterol increases the risk of atherosclerosis. People with what is considered normal cholesterol levels still have heart attack. Several studies have shown practically nonexistent CAD in populations around the world with total cholesterol between 120 to 150 mg/dl. It is important to go beyond total cholesterol numbers alone. Complete lipid profile should include LDL (bad cholesterol) level, HDL (good cholesterol) and Triglyceride levels. In some cases, we need to check for LDL particles size and numbers and Lipoprotein levels. Small dense LDL particles are highly atherogenic.
In one –third of people who develop CAD they have a very dangerous form of LDL called lipoprotein (a). Lipoprotein (a) is an LDL molecule that contains the usual Apoprotein B but it also carriers another protein called Apoprotein (a). This protein inhibits the clot- dissolving process. Lipoprotein (a) therefore presents a double risk; it enhances the process of atherosclerosis and helps blood clot formulation when plaque rupture occurs.
8. Obesity: is a known risk for CAD: in obesity where you carry your fat is very important. Apple shape has excess fat on the abdomen and has significant correlation with metabolic syndrome.
Pear shape has lower body fat with excess fat on the thighs and buttocks. It has no significant correlation with metabolic syndrome. One good advice therefore is eat an Apple but do not become one.
• Obesity is associated with high cholesterol, high triglyceride, HTN and diabetes.
• Loosing just 10% of your body weight can lower your risk.
• BMI of 35 or more carries high risk for CAD.
• For BMI < 35, abdominal girth (waist circumference) of greater than 102cm (40in) for men carries high risk for CAD and that greater than 88cm (35in) carries high risk for women.
• Waist size predicts heart disease death better than body weight.
9. Sedentary Life Style:
• Lack of exercise and physical activity increase the risk of heart attack.
• Persons that are out of shape or deconditioned do poorly after heart attack and take longer time to recover.
• Physical inactivity identifies people who do not get the recommended level of regular physical activity.
• American Heart Association (AHA) recommends 30 to 60 minutes of aerobic exercise 3 to 4 times per week.
• Minimum level of physical activity required to achieve health benefits is a daily expenditure of 150 kilocalories in moderate vigorous activities.
• Regular physical activity reduces the risk of dying prematurely from CAD.
• It helps to prevent development of diabetes.
• It helps maintain weight loss and reduces hypertension.
• Regular physical activity helps to protect first cardiac episodes, helps patient’s recovery from coronary surgeries and reduce the risk of recurrent cardiac events.
10. Metabolic Syndrome: People with metabolic syndrome have high risk for future cardiac event. Metabolic syndrome is a cluster of metabolic abnormalities consisting of impaired fasting glucose, low (good) HDL cholesterol, elevated triglycerides along with abdominal obesity and increased blood pressure.
Having at least 3 of the following five conditions below defines metabolic syndrome.
• Abdominal Obesity (waist circumference more than 40inches/102cm for men or more than 35 in/88cm for women)
• Triglyceride levels more than 150mg/dl
• Low level of (good) HDL cholesterol less than 40mgldl for men or less than 50mgl/dl for women.
• Elevated Blood pressure more than 130/85mml
• Elevated fasting glucose more than 100mg/dl
Metabolic syndrome is associated with insulin resistance and excessive amount of small dense (bad) LDL particles.