Coronary Artery Disease: Causes, Symptoms, Treatment, Pathophysiology, Risk Factors, Diagnosis
What is Coronary Artery Disease?
Coronary artery disease (CAD) is a medical condition where there is accumulation or buildup of plaque in the coronary arteries, which supply blood to the muscles of the heart. Any type of damage, disease or inflammation within these arteries leads to coronary artery disease. Coronary artery disease is a serious condition, which if not treated, can ultimately result in a heart attack.
The arteries are naturally elastic and smooth in nature; however, if there is accumulation of plaque in their walls, then there is narrowing and rigidity of the arteries. This leads to diminished or restricted blood flow and deprivation of oxygen to the heart. As the plaque continues to accumulate, it can rupture resulting in sudden cardiac death or heart attack.
Pathophysiology of Coronary Artery Disease
The buildup of plaque can start from a very young age and increases as a person's age increases. Symptoms of coronary artery disease start to appear when there is a blockage in the artery from the accumulated plaque. The plaque buildup leads to inflammation of the arterial walls and increases the risk of blood clots and heart attacks. The inner walls of the arteries also become sticky from the plaque. The plaque buildup also leads to development of other things such as inflammatory cells, calcium, lipoproteins, which travel in the blood and mix with the accumulated plaque in the blood vessel. Additional inflammatory cells mix with cholesterol leading to increase in the plaque interiorly in the artery, which pushes the walls of the artery outwards. There is narrowing of the lumen of the arteries.
Eventually, the supply of blood to the heart decreases, there is development of new blood vessels from the narrowed coronary artery, which traverse around the blockage to supply blood to the heart. However, if the patient is under extreme stress then even these new arteries will not be able to supply oxygen-rich blood to the muscles of the heart. If the buildup of plaque becomes excessive then the plaque ruptures leading to a blood clot, which can obstruct the blood supply to the heart muscle resulting in a heart attack. If there is any blockage to a blood vessel to the brain then it results in an ischemic stroke. If the blood vessel within the brain ruptures, (commonly from uncontrolled hypertension) then it results in a hemorrhagic stroke.
According to research, taking low-dose aspirin daily helps in preventing strokes and heart attacks in people who are at risk for heart disease and for those people who are above the age of 50 years.
Causes of Coronary Artery Disease
Coronary artery disease is caused by injury, damage, or accumulation of plaque in the inner layer of the coronary artery. Some of the causes of these are:
After there is damage to the inner wall of the artery, there is accumulation of plaque, which are nothing but fatty deposits made of cholesterol and cellular waste products at the site of the damage. This process is known as atherosclerosis. When there is any breakage in a part of the plaque, then platelets start to collect at this region to repair the artery. This clump of platelets can further block the arterial lumen leading to a heart attack.
Risk Factors for Coronary Artery Disease
Age: As a person ages so does, the risk of developing damaged and narrowed arteries and coronary artery disease.
Family History: Having a family history of heart disease or CAD increases the risk of coronary artery disease.
Sex: Men are at an increased risk for developing coronary artery disease than women. However, there is an increase in risk for CAD in women after menopause.
Hypertension: Uncontrolled high blood pressure causes thickening and hardening of the arteries along with narrowing of the lumen of the artery, which is nothing but coronary artery disease.
Smoking: Smoking significantly increases the risk of coronary artery disease. Even exposure to secondhand smoke increases the risk of coronary artery disease.
Hypercholesterolemia: Increased levels of blood cholesterol increase the risk of plaque formation and atherosclerosis and thus coronary artery disease.
Diabetes: Diabetes also increases the risk of coronary artery disease.
Increased Stress: High stress levels also causes damage to the arteries and worsens other risk factors for coronary artery disease.
Obesity: Being overweight worsens other risk factors and indirectly increases the risk of coronary artery disease.
Sedentary Lifestyle: Leading a sedentary life without any exercise or physical activity not only increases the risk of coronary artery disease but also the increases other risk factors of coronary artery disease.
Symptoms of Coronary Artery Disease
Commonest symptom of Coronary Artery Disease is angina (chest pain). Angina can be felt as chest heaviness, ache, pressure, burning, numbness, squeezing sensation, fullness and pain. Angina can be misdiagnosed as heartburn or indigestion. Angina is typically felt in the chest, however, if the patient is having a heart attack due to CAD, then pain can be felt or pain can radiate towards his/her arms, jaw, neck, left shoulder, back and neck. Women experience more subtle symptoms and have accompanying symptoms such as sweating, nausea, fatigue and breathlessness along with angina. Other symptoms of coronary artery disease include palpitations, shortness of breath, tachycardia, dizziness, weakness, nausea and sweating.
Diagnosis of Coronary Artery Disease
Medical history and physical exam of the patient are done. After which the following diagnostic tests are done:
Electrocardiogram (ECG): This test records electrical signals when they travel through the heart and helps in detecting any problem in the electrical signals. An ECG is helpful in finding out if the patient has had a previous heart attack or if a heart attack is in progress.
Holter Monitor: In some patients, Holter monitoring is done where the patient wears a portable monitor for 24 hours as he/she does their daily activities. This type of ECG can record some abnormalities, which can indicate inadequate blood flow to the heart because of coronary artery disease.
Echocardiogram: This is a form of ultrasound test where sound waves are used to generate images of the patient's heart. During this test, the doctor determines which parts of the heart wall are functioning normally and which are not, which gives an indication whether the patient has coronary artery disease or not. The parts of the heart, which are damaged move weakly and can be oxygen deprived, which can indicate coronary artery disease.
Stress Test: This is a test, which detects any changes in the heart when the patient exercises. If the patient experiences symptoms during any physical activity then stress test is done, which involves the patient riding a stationary bike or walking on a treadmill while an ECG is done. Sometimes, medication can be given to stimulate the heart instead of exercise. Stress test is also known as exercise stress test, stress EKG, exercise electrocardiogram, treadmill test or graded exercise test.
Sometimes stress tests can be done using an echocardiogram where the doctor performs an ultrasound before and after the patient exercises on a bike/treadmill. Stress test shows the performance of the heart under stress or any physical exertion which in turn helps with the diagnosis of coronary artery disease.
Nuclear Stress Test: This is another type of stress test, which measures the blood flow to the heart muscle at rest as well as during stress. Nuclear Stress Test is like a regular exercise stress test with the difference being that in nuclear stress test, there is generation of the images of the heart along with an ECG. A small quantity of radioactive substance is injected into the patient's bloodstream, which gives clear images of the heart, the chambers of the heart and the blood supply to the heart. All this information helps in finding out if the patient has coronary artery disease or not. Nuclear Stress Test is also known as myocardial perfusion scan, thallium stress test or a radionuclide test.
Angiogram or Cardiac Catheterization: This is a type of x-ray test where a special dye is injected and a camera is used to take pictures of the blood flow through the heart. The dye is injected via a catheter into the arteries. The dye delineates the blockages and narrowed parts of the arteries and can be seen as x-ray images. In case of an arterial blockage, a balloon is pushed via a catheter and inflated, so that the blood flow in the coronary arteries increases. A stent can be placed after this to keep the dilated artery open.
Heart Scan: Also known as coronary calcium scan, this scan helps in detecting calcium deposits in the arteries, which cause narrowing of the arteries. If there is a significant amount of calcium present, then it indicates coronary artery disease.
Treatment of Coronary Artery Disease
Lifestyle Modifications: Making positive changes to one's lifestyle helps a lot in preventing as well as controlling coronary artery disease. The habits, which need to be incorporated, include quitting smoking and alcohol, avoiding processed foods and following a low-salt, low-trans-fat and low-sugar diet. Along with dietary change, it is also important to perform some type of exercise or physical activity daily. It can be something as simple as walking daily. It is also important to consult your doctor before starting any exercise regime, especially if the patient has risk factors for heart disease or diabetes, or already has heart disease or diabetes.
Medications: Medications commonly prescribed for treating coronary artery disease include aspirin and statins.
Surgery: Surgical procedures commonly done for treatment of coronary artery disease include coronary balloon angioplasty, coronary artery bypass surgery and stent placement. All these procedures help in increasing the blood supply to the heart, however, these procedures are not a cure for coronary artery disease and they only help in preventing the worsening of coronary artery disease. However, it is important that patient try to decrease his/her risk factors along with medication and surgery to prevent further worsening of coronary artery disease.
New Treatments for Coronary Artery Disease
Other new innovative treatment methods are being studied to prevent coronary artery disease and heart disease and these treatments are:
EECP (Enhanced External Counter Pulsation): Patients suffering from chronic angina and who do not get relief from nitrate medications or who are not a candidate for surgery can benefit from EECP. This is an outpatient procedure where cuffs are placed on the legs, which inflate and deflate to enable an increase in the blood supply to coronary arteries.
Angiogenesis: This process consists of stem cells and other genetic things that are given directly into damaged tissue of the heart or are given via vein. Angiogenesis helps in growth and development of new blood vessels so that they can travel around the blocked vessels and supply blood to the heart muscles.