Cardiovascular disease is a non-communicable disease; it is not caused by a pathogen and cannot be passed from person to person. Most cardiovascular disease begins with atherosclerosis developing in an artery due to factors such as high blood pressure. In this article we will look at how atheromas develop, cardiovascular disease risk factors, and treatments.
Development of atherosclerosis
Atherosclerosis begins with damage to the endothelium (the inner layer) of an artery. There is an inflammatory response to this damage, and white blood cells flood the area. The white blood cells absorb lipids from LDL cholesterol (see below) in the blood. They begin to build up in the area as fatty deposits, and combine with connective tissue to form an atheroma (a plaque). The growing atheroma begins to block the lumen of the artery, reducing blood flow. This increases blood pressure, and also means that tissues may not be receiving enough oxygen. If the obstruction is an a coronary artery, that means that the heart muscle tissue is not receiving enough oxygen for aerobic respiration and it can lead to a myocardial infarction (heart attack).
If an atheroma completely ruptures the endothelium, blood clots can form due to the release of thromboplastin. Take a look at this article for a full explanation of the blood clotting process. If a blood clot breaks off from the atheroma, this can then lodge in a blood vessel somewhere else in the body and block or reduce blood flow to tissues.
Cholesterol is a type of lipid which you may have come across already in cell membranes. There are two main types of cholesterol in the blood: LDL cholesterol and HDL cholesterol. Both have very different effects on cardiovascular disease risk. LDL cholesterol transports cholesterol from the liver to the blood, where it is able to contribute to atheroma formation as described above. However, HDL cholesterol transports cholesterol from the blood back to the liver, so is actually beneficial for reducing cardiovascular disease risk. Therefore a high LDL:HDL ratio is a cardiovascular disease risk factor.
The main risk factors for cardiovascular disease are as follows:
- Age – risk increases with age.
- Sex – men have increased risk compared to women.
- High blood pressure – this increases the risk of damage to the artery endothelium.
- Smoking – nicotine increases risk of high blood pressure, and carbon monoxide reduces the amount of oxygen carried in the blood.
- Poor diet – a diet high in saturated fat raises blood LDL cholesterol. A high salt diet can increase blood pressure.
- Low activity levels – a sedentary lifestyle increases blood pressure.
- Genetic predisposition – some people have alleles which increase risk.
Many of these risk factors are lifestyle factors, so risk can be reduced by a patient improving their lifestyle. However some factors, such as age, are not within a patient’s control. Remember when looking at data about CVD risk factors that correlation does not necessarily mean causation.
The main treatments for cardiovascular disease target the underlying risk factors. For example, patients can be given antihypertensive drugs to lower blood pressure (hypertension = high blood pressure). Statins can be taken to lower blood LDL cholesterol, and anticoagulants can be taken to prevent blood clots forming.
- Cardiovascular disease often begins with damage to the artery endothelium due to factors such as high blood pressure.
- Atheromas form due to the inflammatory response and accumulation of connective tissue. They can reduce blood flow to tissues.
- Endothelium damage can trigger blood clotting.
- High LDL cholesterol is a major risk factor, along with high blood pressure, poor lifestyle, and genetic predisposition.