Stable Angina

Topic Highlights

' Angina is a disease of the coronary arteries causing chest pain and discomfort.

' Coronary arteries are blocked due to plaque build up, resulting in reduced blood supply to the heart.

' This visual presentation describes the types of angina, focusing on stable angina, coronary artery blockage, diagnostic procedures, treatment - medications and surgery.

Transcript

Chest discomfort is one of the most common symptoms for which people need medical help. Angina, known as angina pectoris, is one of the most important conditions that cause mild to severe chest pain. Angina is a disease of the coronary arteries affecting millions of people worldwide. Angina causes disability and economic loss and in most cases impairs a person's quality of life. It also increases risk of fatal myocardial infarction (or heart attack) and death.

The coronary arteries originate from the aorta and supply blood to the heart muscle. The word coronary is derived from the Latin word meaning crown as the three main coronary vessels appear like a crown superimposed on the heart.

There are different types of chest pain such as that caused by indigestion and muscular pain, however, anginal pain is the chest pain or discomfort that occurs when heart muscles are starved of oxygenated blood. Angina derives its name from the Latin word 'angerer' meaning 'tight chest'. When angina is caused by a blockage of the coronary arteries it is classified by three principal types. These are stable angina, unstable angina and variant angina.

In stable angina the chest pain follows a regular pattern of frequency, intensity and duration and is fairly predictable, normally occurring after physical and mental exertion. The patient may be aware or unaware of his exertion limitation. Stable angina is caused by a fixed blockage in the coronary artery that results in reduced blood supply to the heart. Angina is precipitated when the demand surpasses the supply and is relieved by rest or medication.

Unstable angina, as the name suggests, does not follow a pattern and is not predictable. Unstable angina can also be a manifestation of the later stages of stable angina, where unlike stable angina, it can occur without physical exertion and is not relieved by rest or medication. Unstable angina frequently occurs at rest and is a more serious condition than stable angina as it may progress to acute myocardial infarction or heart attack.

Variant angina is a rare form of angina, which occurs at rest. The chest pain is caused by coronary artery spasm, a sudden constriction of a coronary artery resulting in a decrease in blood supply to the region supplied by the artery. Variant angina is also called Prinzmetal's angina after the physician who described it.

Atherosclerosis is the single most important underlying cause of angina pectoris. Atherosclerosis derives its name from the Greek words 'athero' meaning gruel or porridge and 'sclerosis' meaning hardness. It is the hardening of the arterial wall and the narrowing of the arterial lumen due to the slow build-up of lipid-rich plaque on the inside walls of the arteries. Plaque is formed by the build-up of fat, cholesterol, calcium, and other substances circulating in the blood.

Plaques are of two types, hard and soft. Hard or stable plaques have a relatively thick covering due to calcification and cause artery walls to thicken and harden. Soft or unstable plaques are the most vulnerable as they have the potential to rupture without warning. When the soft plaque bursts, it triggers the formation of a clot, a 'thrombus' in the artery at the site of the rupture and restricts the flow of blood drastically causing a potential larger block in the lumen.

There are many risk factors that increase the likelihood of developing angina. Some cannot be controlled, while others are controllable and modifiable. Some of the risk factors that cannot be controlled are advancing age, gender, and family history. Advancing age is strongly associated with atherosclerosis, hence with angina. Atherosclerosis is more common in males until middle age, after which the risk becomes equal between both sexes. Individuals with a family history of angina or heart attacks are at a greater risk compared to those without. Menopause in women increases the risk for developing cardiovascular disease including angina because of decreased levels of estrogen, which is a vasodilator that is responsible for opening blood vessels and increasing blood flow.

Some of the risk factors that can be controlled are high blood cholesterol level, diabetes mellitus, hypertension, cigarette smoking, alcohol consumption, lack of physical activity/exercise and obesity. Increased levels of low-density lipoproteins (LDLs) (or bad cholesterol), decreased levels of high-density lipoproteins (HDLs) (or good cholesterol) and high levels of triglycerides in the blood increases the overall risk for atherosclerosis; and thus angina. Infections that cause inflammation in the arterial wall may also increase the risk for angina. Stress and anger is also a well-known trigger for angina.

The pain is normally precipitated by exercise or physical or emotional stress. Physical stress occurs while climbing stairs, walking uphill or against the wind, sexual intercourse etc. Angina is more likely to occur if physical activity is undertaken immediately after a heavy meal or in extreme cold temperatures.

As angina is caused due to a temporary insufficiency of oxygen supply to the heart, it typically lasts for a couple of minutes. However it goes away within minutes of stopping the stressful activity. The other symptoms associated with angina pectoris are breathlessness, nausea, sweating, light-headedness and a sense of impending death.

Angina pectoris can be diagnosed from the patient's history and descriptive symptoms besides the presence of risk factors. The chest pain is typical in its position, duration and precipitation. In addition to blood tests, some specialized tests can be done to diagnose angina.

An electrocardiogram (ECG), echocardiogram, exercise stress test on a treadmill or bike, nuclear scan or thallium scan, electron beam CT and coronary angiogram are some of the tests done to diagnose angina.

The treatment involves an all round approach by assessing the extent and severity of the disease, identifying the risk factors, management of the symptoms and evaluation of existing treatment to improve the life expectancy and quality of life in high risk patients. The treatment of angina pectoris varies depending on the symptoms and the severity of the disease. Treatment includes lifestyle changes, medication and, sometimes, invasive procedures and surgery.

Lifestyle changes are mainly directed to decrease the risk factors related to atherosclerosis, the most important cause of angina. These include maintaining weight, quitting smoking and excess alcohol, increasing regular exercise, decreasing sodium (salt) content in the food and consuming a low-fat, low-cholesterol diet to maintain an optimum lipid profile where the total cholesterol level is 5.0mmol/L or less.

Cholesterol lowering agents help bring down the cholesterol levels to normal. This helps control one of the risk factors of atherosclerosis. Examples of lipid lowering drugs are ezetimibe, simvastatin, atorvastatin, rosuvastatin, pravastatin, that is, the statins, and the fibrates such as gemfibrozil. Combination drugs such as ezetimibe and simvastatin are also available.

There are four groups of drugs available to help relieve and prevent the symptoms of angina. They are nitrates, beta blockers, calcium antagonists (calcium channel blockers) and the potassium channel activator, nicorandil. Some countries also have the sinus node inhibitor, ivabradine that lowers heart rate. Aspirin is used to prevent clots forming in the arteries.

The new drug procoralan is the first selective sinus node If inhibitor. It selectively reduces the heart rate while maintaining the amount of blood pumped by the heart. Unlike many other antianginal drugs procoralan has no effect on blood pressure.

The most widely used invasive treatment to treat angina or coronary artery disease is percutaneous coronary intervention (PCI) also called percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass graft surgery (CABG).

Balloon angioplasty or PTCA has been available for twenty years. It is a non-surgical procedure that removes the blockages in the coronary arteries. The procedure is done with a small balloon catheter inserted into an artery in the groin or arm, and passed into the blockage in the coronary artery. The balloon is then inflated several times to enlarge the narrowed artery. Invariably a self-expanding coronary stent is deployed at the same time to help keep the artery open.

The stent may be inserted into the artery at the blockage. The stent is placed at the tip of the catheter, over the balloon. When the catheter reaches the blockage, the balloon is inflated, expanding the stent. Then the balloon is deflated and removed along with the guide wire and the catheter. The stent is left in the coronary artery to prevent it getting blocked again. The chance of reblockage or restenosis of the artery remains high even with a stent and the patient may need a repeat procedure or a CABG. Sometimes stents are coated with medicines to prevent restenosis. These stents slowly release the medicine into the surrounding tissue, which helps prevent restenosis process.

In CABG, the surgeon will bypass the blockage using grafts. These may be veins from the legs or arteries from the arm or chest wall. One end of the graft is attached to the aorta and the other to the coronary artery beyond the blockage. The surgery is done by many methods. CABG is also performed using advanced techniques like minimally invasive surgery. Here the surgery is done through small incisions without the need to open the chest itself. This surgery is suitable for patients requiring one to two bypasses in the arteries on the front of the heart (i.e., epicardial arteries).

In some of cases an advanced technique called beating heart or off-pump surgery is performed. It is performed by opening the chest using a stabilizing device to restrict the movement of small segments of the heart, while the patient's heart continues to beat. This allows the surgeon to operate without the use of a heart lung machine used in conventional cardiac surgery. Robot assisted coronary artery bypass is a latest advance in this field. Surgeons use a robotic device to perform the bypass through a much smaller incision without separating the breastbone. In this type of surgery, surgeons perform the operation while watching a video screen without any direct contact with the patient.

It is important to do everything possible to limit the progression of angina. This can be achieved by a combination of treatment and making appropriate changes to your lifestyle.