An Introduction to Coronary Artery Disease (Atherosclerotic Heart Disease - ASHD)

The heart is like any other muscle, requiring blood to supply oxygen and nutrients for it to function. The heart's needs are provided by the coronary arteries,  which begin at the base of the aorta and spread across the surface of the heart, branching out to all areas of the heart muscle. 

The coronary arteries are at risk for narrowing as cholesterol deposits, called plaques, build up inside the artery. If the arteries narrow enough, blood  supply to the heart muscle may be compromised (slowed down), and this slowing of blood flow to the heart causes pain, known as angina pectoris.  A heart attack or myocardial infarction occurs when a plaque ruptures, allowing a blood clot to form. This completely obstructs the artery, stopping blood flow to part of the heart muscle, and that portion of muscle dies. 

What are the major risk factors for Coronary Artery Disease 

Risk factors for heart disease include: 

• Smoking  
• High blood pressure (hypertension) 
• High cholesterol 
• Diabetes  
• Family history 
• Peripheral artery disease 
• Obesity 

What are the symptoms of heart disease?

The typical symptoms of coronary artery disease are associated chest pain or  shortness of breath at rest or with activities.  Classically, the pain of angina  is described as a pressure or heaviness behind the breast bone with radiation to the jaw and down the arm accompanied by shortness  of breath and sweating. Unfortunately, angina has a variety of presentations, and there may not even be specific chest pain. There may be shoulder or back ache, nausea, indigestion or upper abdominal pain.  

Women, the elderly, and people with diabetes may have different perceptions of pain or have no discomfort at all. Instead, they may complain of malaise or fatigue. 

Healthcare providers and patients may have difficulty understanding each  other when symptoms of angina are described. Patients may experience pressure or tightness but may deny any complaints of pain. 

People with coronary artery disease usually have gradual progression of their symptoms over time. As an artery narrows over time, the symptoms that it causes may increase  in frequency and/or severity. Healthcare providers may inquire about changes in exercise tolerance (How far can you walk before getting symptoms? Is it to  the mailbox? Up a flight of stairs?) and whether there has been an acute change in the symptoms. 

Once again, patients may be asymptomatic until a heart attack occurs. Of course, some patients also may be  in denial as to their symptoms and procrastinate in seeking care. 

How is coronary artery disease diagnosed? 

The diagnosis of heart disease begins with obtaining a history that  the potential for coronary artery disease exists. Risk factors need to be assessed, and then testing may be required to confirm  the presence of heart disease.

Diagnostic Studies 

Not every patient with chest pain needs heart catheterization (the most invasive test). Instead, the healthcare provider will try to choose the testing modality that will best provide the diagnosis, and if coronary artery disease is present, decide what impairment, if any, is present. 

Electrocardiogram (ECG or EKG) 

The heart is an electrical pump, and the electrical impulses it generates can be detected on the surface of the skin. Normal muscle conducts electricity in  a reproducible fashion. Muscle that has decreased blood supply conducts electricity poorly. Muscle that has lost its blood supply and has been replaced  with scar tissue cannot conduct electricity. The electrocardiogram (EKG) is a noninvasive test used to reflect underlying heart conditions by measuring the electrical activity of the heart. 

Some people have "abnormal" EKGs at baseline but this may be  normal for them. It is important that  an electrocardiogram be compared to previous tracings. If a patient has a baseline abnormal EKG, they should carry a copy with them for reference if they ever need another EKG. 

Stress testing 

If the baseline EKG is relatively normal, then monitoring the EKG tracing while the patient exercises may uncover electrical changes that may indicate the presence of coronary  artery disease. There are a variety of testing protocols used to determine whether the exercise intensity is high enough to prove that the heart is normal.  Sometimes, a radioactive technetium isotope known as thallium (or myoview) is used during the stress test to provide the cardiologist with additional information regarding normal or abnormal blood flow to certain areas of the heart muscle.  Some patients are unable to exercise on a treadmill test, but they can still undergo cardiac stress testing by using intravenous medication that causes the heart to work harder. 

Stress testing is done under the supervision of medical personnel because of the potential of provoking angina, shortness of breath, abnormal heart rhythms, and heart attack. 

Echocardiography 

Used with or without exercise, echocardiography can assess how  the heart works. Using sound waves to generate an image, a cardiologist can evaluate many aspects of the heart. Echocardiograms can examine the structure of the heart including the thickness of the heart muscle, the septum (the tissues that separate the four heart chambers from each other)  and the pericardial sac (the outside lining of the heart). 

The test can indirectly assess blood flow to parts of the  eart muscle. If there is decreased blood flow, then segments of the heart wall may not beat as strongly as adjacent heart muscle. These wall motion abnormalities signal the potential for coronary artery disease. 

The echocardiogram can also assess the efficiency of the heart by measuring ejection fraction. Normally when the heart beats,  it pushes more than 60% of the blood in the ventricle out to the body. Many diseases of the heart, including coronary artery disease,  can decrease this percentage (the ejection fraction). 

Perfusion studies 

Radioactive chemicals like thallium  or technetium can be injected into a vein and their uptake measured in heart muscle cells. Abnormally decreased uptake can signify decreased  blood flow to parts of the heart because of coronary artery narrowing. This test may be used when the patient's baseline EKG is not normal and is less reliable when used to monitor a stress test. 

Computerized tomography 

The latest generation of CT scanners can take detailed images of blood vessels and may be used as an adjunct to determine whether coronary artery disease is present. In some institutions, the heart CT is used as a negative predictor. That means that the test is done to prove that the  coronary arteries are normal rather than to prove that the disease is present. 

Heart catheterization or coronary angiography 

This test  is the gold standard for the diagnosis of coronary artery disease. A cardiologist inserts and then threads a small tube through the groin or arm into the coronary arteries, where contrast dye is injected to directly visualize the arteries on an x-ray. This test defines the anatomy of the coronary arteries. 

CT coronary angiogram is a fairly new test to diagnose coronary artery disease. During this procedure, intravenous dye containing iodine is injected into the patient and CT scanning is performed to image the coronary arteries. 

What is the treatment for  heart disease? 

Coronary artery disease is usually treated in a multi-step approach depending upon a patient's symptoms.  The patient and healthcare provider need to work together to return the patient to a normal lifestyle. 

Prevention of heart disease 

The key to the treatment is prevention.  A healthy lifestyle is the key, including exercise, proper nutrition, and smoking cessation. 

An aspirin a day is recommended to decrease the risk for heart disease and should be started with the recommendation of a healthcare provider. 

A little alcohol (one drink per day for women or two drinks per day for men) may decrease the risk of heart disease compared to nondrinkers. However, it is not recommended that nondrinkers begin drinking. 

Modifying risk factors for heart disease 

While patients cannot choose their family and alter their genetic predisposition to coronary artery disease, the rest  of the risk factors are under control of the patient. Keeping blood pressure, cholesterol and other lipid levels, and diabetes under control needs to become a life-long goal. Smoking cessation is highly encouraged. 

Medications 

The purpose of medications for coronary artery disease is to allow more efficient  heart muscle function to overcome any blockage that might exist. 

Aspirin  is one of the cornerstones of coronary artery disease treatment. It  prevents platelets  from clumping together when blood becomes turbulent, like when it flows past a narrowing in an artery. 

Beta blockers prevent the action  of adrenaline on the  heart and allow the heart  to beat  a more efficiently by reducing the  heart rate  and causing  the heart muscle to contract less aggressively. Examples of beta blockers include: 

• atenolol (Tenormin) 
• metoprolol (Lopressor, Toprol XL) 
• propranolol (Inderal, Inderal LA) 
• carvedilol (Coreg) 
• labetalol (Normodyne, Trandate) 
• Calcium channel blockers can also be used  to control heart rate and allow the heart to beat more efficiently. Examples of calcium channel blockers include: 
• diltiazem (Cardizem, Dilacor, Tiazac) 
• verapamil (Calan, Verelan, Verelan PM, Isoptin, Covera-HS) 
• amlodipine (Norvasc)
• 
  
• ranolazine (Ranexa)

• Coronary artery disease is  the most common cause of death in the United States. Over a million people each year will have a heart attack and 25% will die before they get to the hospital  or in the Emergency Department. 
• Prevention is the key to treatment. 
• Diagnosis is often made by careful history taken by a healthcare provider. Some patients may have atypical symptoms, including almost none at all. 
• The testing strategy to confirm the diagnosis and plan appropriate treatment needs to be individualized for each patient. 
• Treatment depends upon the severity  of disease and is often directed by the symptoms experienced by the patient.