Coronary Artery Disease

Overview

The heart ensures that blood circulates throughout your body, supplying oxygen and nutrients to cells, tissues, and organs and clearing away metabolic wastes and carbon dioxide. Just like the other organs and tissues of your body, your heart too requires a constant and regular supply of oxygenated blood in order to continue functioning optimally.

The heart pumps out oxygenated blood into the aorta which carried it to the rest of the body. From the aorta, there arise two blood vessels known as the left and right coronary arteries. These run along the surface of the heart and supply oxygenated blood to the left and right sides of the heart respectively. These arteries are narrow and represent the only source of blood to the heart tissues. Hence, any condition that interferes with the ability of the coronary arteries to deliver blood to the heart cells can have critical consequences.

What is Coronary Artery Disease?

Coronary artery disease (CAD) is a form of cardiovascular disease that can give rise to a variety of conditions such as angina and myocardial infarction (heart attack). Some sources also refer to CAD as coronary heart disease. CAD arises when, generally due to a blockage in the coronary arteries, there is a reduction in the supply of blood to the tissues of the heart. This can be a life-threatening condition.

The main underlying mechanism that gives rise to coronary artery disease is a condition known as atherosclerosis. Atherosclerosis involves the formation of deposits or plaques within the arteries, creating an obstruction in the path of the blood flowing through the arteries. In this case, it is the coronary arteries that are affected.

What is the Relationship Between CAD and Atherosclerosis?

Let us briefly consider the process that gives rise to atherosclerosis, since this has a bearing on CAD. To put it simply, arteries are blood vessels with thick muscular walls and narrow lumens or passages for the blood to flow through. The walls are flexible and elastic and the arterial lumen is lined on the inside by a layer of cells known as the epithelium. Sometimes, the epithelium becomes damaged and these sites of damage become inflamed. If conducive factors are present, these sites begin to slowly accumulate fatty deposits along with cellular wastes, calcium and even living cells. As these deposits build up, the lumen becomes obstructed and the arterial walls stretch to make up for the lost space. Eventually, however, this causes the walls to become inflexible and hardened with plaque, and the blood flow becomes restricted, starving the target tissues of oxygen and nutrients.

How Does CAD Develop and Progress?

When atherosclerosis develops in the coronary arteries which serve as the crucial conduits for supplying oxygen-rich blood to the heart’s tissues, this gives rise to coronary artery disease. Gradually, the heart itself becomes starved of the oxygen and nutrients it requires. This is known as ischemia. This process may be gradual and progressive, spread out over a lifetime. Alternatively, it is possible for a blockage to develop suddenly, when a blood clots forms over the deposit or a section of the plaque itself becomes detached and lodged in the narrow coronary artery, resulting in completely shutting off blood supply.

Sometimes a narrowed artery can develop new branches in order to get around the obstruction caused by the plaque. However, these new arteries may fail under conditions of stress or vigorous physical activity.

What Are The Causes and Risk Factors?

The list below mentions some factors that increase the risk of developing atherosclerosis and coronary artery disease.

• The risk increases with age.
• Being male is associated with a higher probability of developing CAD.
• Post-menopause, women are at a higher risk of developing CAD.
• Having a family history of cardiovascular disease.
• Being African-American, Mexican-American or native American has been shown by some studies to be associated with a higher risk of developing CAD.
• Being overweight or obese.
• Having diabetes.
• Even passive smokers are at a higher risk of developing CAD than non-smokers.
• Elevated blood cholesterol.
• Hypertension.
• Excessive alcohol consumption.
• Stress.

What Are The Signs and Symptoms of CAD?

Initially, atherosclerosis tends to remain asymptomatic. However, as the degree of plaque deposit in the arterial lumen increases and blood flow reduces, early symptoms such as angina or chest pain will typically begin to manifest. This may be particularly exacerbated during periods of increased physical activity or stress. However, as the disease progresses, the patient may even begin to experience angina when he or she is at rest.

The list below outlines some typical symptoms of all stages of CAD beginning from the initial phase to the more severe manifestations.

• Angina or chest pain. Sometimes this is mistaken for heartburn caused by acid reflux. Further, pain could appear on the shoulders, neck, and arms.
• Elevated heart rate. Some may even experience heart palpitations.
• Sweating.
• Dizziness.
• Nausea.
• Weakness.
• Feeling short of breath.

What Are The Potential Complications?

CAD can lead to a variety of critical outcomes, such as:

• Abnormal heart rhythm or cardiac arrhythmia.
• Myocardial infarction (heart attack).
• Heart failure.
• Death.

What Tests Will I Need?

The process of diagnosis may involve the following stages, depending on the particulars of the case:

• Medical history and family history.
• Physical examination.
• Blood tests.
• Electrocardiogram.
• Stress test.
• CT scans.
• Coronary angiography.

What Are Some Treatment Options?

The treatment of coronary artery disease focuses mainly on lifestyle changes. Medications and certain medical procedures are also an essential part of the treatment protocol.

Lifestyle Modifications: Certain modifications in the lifestyle of an individual are: quitting smoking, choosing healthier foods, regular physical activity, maintaining optimum body weight, and stress reduction. A healthy lifestyle leads to healthy arteries.

Medications: Some of the drugs prescribed in order to treat CAD are as follows:

• Cholesterol-modifying medications– Lowering the levels of low-density lipoprotein (LDL) cholesterol or the ‘bad’ cholesterol, can impede, stop or even reverse the build-up of the fatty deposits in the arteries. Increasing the levels of the high-density lipoprotein (HDL) cholesterol, also known as the good cholesterol, can also help to prevent the deposition of plaque in the arteries. Certain medications such as statins, niacin, bile acid sequestrants, and fibrates can be administered to lower the cholesterol levels. Statins also help in help stabilizing the lining of the heart arteries.
• Aspirin- It acts as a blood thinner and reduces the risk of getting a heart attack.
• Beta-blocker drugs– These drugs lower your heart rate and blood pressure, reducing the stress on the heart and help in relieving symptoms of chest pain. They also reduce the risk of heart attacks.
• Ranolazine– This drug helps to relieve chest pain.
• Calcium channel blockers- They are used to treat angina (in some cases).
• Nitroglycerin– This drug can be administered in the form of tablets, sprays or patches. It causes temporary dilatation of the coronary arteries thereby reducing the chest pain.
• Angiotensin-converting enzyme (ACE) inhibitors– These medications lower blood pressure, interfere with the hormone that constricts the blood vessels and thereby reduce the load on the heart. They also reduce the risk of recurrent heart attacks.
• Surgical intervention- Procedures such as angioplasty and coronary artery stent placement or coronary artery bypass surgeries are performed to restore and improve the flow of blood.

Prevention of CAD can be done by lifestyle modifications such as regular exercise, intake of a balanced diet, maintaining healthy body weight, managing stress and by quitting smoking.

References