Atherosclerosis

What is atherosclerosis ?
Atherosclerosis is a disease affecting blood vessels and means literally "hardening of the arteries". Large and medium sized arteries are most commonly affected. The inside wall of the artery becomes furred up with deposits of cholesterol and calcium causing the blood vessel to become narrowed or blocked. These deposits are called atherosclerotic plaque. Atherosclerosis is a multifocal condition. A patient with hardening of the arteries developing in one area of the body, for example the heart, is highly likely to have the same condition present in arteries elsewhere in the body. For this reason, someone who has a heart attack due to atherosclerosis is at elevated risk of having a stroke due to the same underlying condition affecting the brain arteries.


How does atherosclerosis cause problems ?
Atherosclerosis causes symptoms in three ways :
  1. Restriction of blood flow
  2. Embolisation (a blood clot forms, breaks off and lodges downstream)
  3. Thrombosis (the artery clots and blocks)
The consequence of atherosclerosis depends on which arteries are affected by the hardening process. Atherosclerosis in the heart causes angina and heart attacks. Atherosclerosis in the arteries supplying the brain causes strokes. Hardened arteries in the limbs cause pain on walking (intermittent claudication). These conditions are explained in their sections of the website (see Conditions Treated, Prevented and Cured).

Risk factors for atherosclerosis


Fixed risk factors
These are of limited interest since no-one can alter their age, the population into which they were born or the age at which a parent had a heart attack or stroke. Vascular disease in any one arterial territory is an important risk factor for adverse events in others. Patients surviving strokes are more likely to die of a heart attack than another stroke. Similarly, intermittent claudication is a major risk factor for stroke and ischaemic heart disease. Strokes and intermittent claudication are both explained in their sections of the website (see Conditions treated, Prevented and Cured).

Risk factors that can be changed


Smoking, Hypertension, Hypercholesterolaemia and sedentary lifestyle each double the risk of Acute Myocardial Infarction. When two or more are present, the risk is multiplied.

Smoking


The more someone smokes, the higher their risk of developing hardening of the arteries. This fact is complicated by the oddity that some individuals may smoke heavily without obvious ill effects, whilst others are much more susceptible to artery damage after smoking even a few cigarettes. Some people can get away with it, most can't.

Hypertension
The International Society of Hypertension now defines hypertension as systolic pressure over 140 mmHg and diastolic pressure over 90 mmHg. These levels are arbitrary since the risk of ischaemic heart disease and stroke rises steadily across the whole range of blood pressure. The effect of the entire population lowering their population by only 5mmHg by lifestyle changes would be dramatic, reducing nearly of heart attacks and 1/3 of strokes. The lower the blood pressure, the lower the risk of atherosclerosis.
Cholesterol
Like hypertension, the definition of hypercholesterolaemia is arbitrary and the risk of vascular disease rises steadily across the whole range of blood cholesterol concentrations. Treating patients with arterial disease with statins provides protection against heart attack and stroke even for patients with normal cholesterol levels, since statins stabilise atherosclerotic plaque.
Exercise
Regular Exercise Regular aerobic exercise confers considerable protection against myocardial infarction. Thirty minutes of moderate activity most days of the week is the current recommendation.
Diabetes
Diabetes Patients Patients with diabetes are at greatly elevated risk of vascular disease in all territories (cardiac, carotid and peripheral). Good diabetic control improves prognosis.
Alcohol
Heavy drinkers tend to have higher blood pressure but those who consume modest quantities of wine on a regular basis have lower mortality rates than teetotallers.
Homocysteine
Blood levels of this amino acid may be an independent risk factor for arterial disease and increasing intake of vitamin B6 and folate effectively reduce homocysteine concentrations. It is not yet clear whether this will be an important way of reducing atherosclerotic disease.