By Dr Ananya Mandal, MD
Angina is manifested as a chest pain that may (in case of stable angina) or may not (in case of unstable type of angina) be brought about by physical exertion or mental stress. 1-5
Physiology of the heart and its blood vessels
The heart muscles work non-stop throughout life to contract and pump blood to the various organs of the body. As they are constantly in motion they require regular and adequate supply of oxygen-rich blood to function normally.
Blood to the heart muscles, called cardiac muscles, is supplied by two large blood vessels that are known as the left and right coronary arteries. These originate at the base of the largest artery that arises out of the left ventricle to supply all the organs of the body called the aorta.
Pathology of angina
When the heart beats faster or needs to pump harder like in cases of fear, emotional distress, stress, physical exertion etc. the blood supply to the heart rises along with the demand of the heart muscles for oxygen.
This increased demand thus, is usually met by the body. When this increased demand for oxygen rich blood is not met by the coronary arteries the heart muscles undergo a process called ischemic heart disease.
Types of angina
There are two types of angina – stable and unstable. In stable angina the symptoms of ischemia of the heart muscles, due to increase demand and reduced supply of blood, occurs when there coronary arteries become narrow and hardened by a process called atherosclerosis. This restricts the blood flow to the muscles of the heart.
When the heart is back at rest or if the person who has developed the attack of angina rests, the symptoms of chest pain gradually recede. This means that the relative discrepancy between supply and demand is met and removed at rest.
In patients with unstable angina the underlying cause is still atherosclerosis. Atherosclerosis leads to deposits of fatty tissues called plaques in the walls of the coronary arteries. These may break open or rupture and lead to clots of blood within the artery. This leads to obstruction of blood flow and symptoms of angina.
This type of angina may rapidly progress into a heart attack that is caused due to death of a large part of heart muscles due to ischemia and lack of oxygen rich blood supply.
Who is at risk of angina?
Angina (both Stable and Unstable types) are caused when any cause leads to narrowing of the coronary arteries. These may include hypertension, high blood cholesterol and so forth.
Hypertension or high blood pressure
Risk factors for high blood pressure include:
- lack of exercise
- family history of high blood pressure
Hypertension is more common in people of Afro-Caribbean and south Asian (Indian, Pakistani and Bangladeshi) descent. This could be a genetic link. High blood pressure raises the risk of getting angina.
High blood cholesterol or dyslipidemia
Cholesterol is normally is needed for the functions of the body. There are two main types of cholesterol – LDL and HDL.
Low density lipoprotein (LDL) often referred to as ‘bad cholesterol’ as it blocks the arteries when in excess. Another type is high density lipoprotein (HDL) that helps remove the fat deposits from within the arteries and is thus called ‘good cholesterol’.
People with high levels of LDL and low levels of HDL are at risk of atherosclerosis and development of angina.
Obesity and overweight individuals
A diet high in fat and lack of exercise predisposes to heart disease, hypertension and high blood cholesterol and raises risk of angina.
Smoking damages the arterial walls and also helps form platelet clots, clumps and plaques that may obstruct blood flow and lead to angina. In addition smoking decreases the oxygen carrying capacity of blood and leads to a raised risk of angina.
High alcohol consumption
This leads to risk of high blood pressure and high blood cholesterol and is interlinked with risk of angina.
Other risk factors for angina
Other risk factors for angina include:
- Diabetes mellitus
- Advancing age – Arterial walls thicken and harden with age and the arteries tend to get narrow.
- Those with a family history of angina – Those with a first degree relative (mother, father, brother or sister) who has high blood pressure, high blood cholesterol, heart disease or angina carry a higher risk of angina.
- Other conditions include arrhythmias (abnormal heart rhythms), disease of the heart valves, aortic stenosis, structural or anatomical defects of the coronary arteries, severe anemia, hypertrophic obstructive cardiomyopathy, etc.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)