LEARNING OUTCOME AND OBJECTIVES:  Upon completion of this course, you will be better prepared to plan, deliver, and evaluate evidence-based preventative and therapeutic care for patients with or at risk for coronary artery disease. Specific learning objectives to address potential knowledge gaps include:

• Describe the anatomy and normal blood circulation of the heart.
• Review the pathophysiology of CAD.
• Differentiate between the major clinical presentations of CAD.
• Discuss nonpreventable and preventable risk factors.
• Identify the signs, symptoms, and clinical test outcome criteria used to screen and diagnose coronary artery disease.
• State the principles underlying the acute management of the disease.
• Explain the components of a comprehensive plan of care and monitoring for patients with chronic CAD.

INTRODUCTION

Coronary artery disease (CAD) is caused by atherosclerosis of the coronary arteries that leads to a restriction of blood flow to the heart. Atherosclerosis (or arteriosclerosis) is a word that comes from the Greek athere, meaning “fatty mush,” and skleros, meaning “hard.” Thus, it is commonly referred to as “hardening of the arteries.”

Atherosclerosis is a process that develops slowly over time. Typically, atherosclerosis begins in a person’s teenage years or earlier, and the disease worsens quietly for decades, based primarily on diet, lifestyle, and genetic traits. As people age, their atherosclerosis becomes more likely to involve the arteries of the heart and to become coronary artery disease.

Atherosclerosis is a chronic condition that narrows arteries by building lipid bulges in the arterial walls. These bulges are called atherosclerotic plaques, or simply plaques. These plaques can cause a narrowing of small blood vessels such as the coronary arteries, restricting the blood flow to the myocardium. Injury to the endothelium (the lining of the blood vessel wall) occurs, causing inflammation. In some people, the plaques become covered by collagen, narrowing the blood vessel lumen and restricting blood flow to distal tissue. When the blood vessels in question are the coronary arteries, the myocardium receives an insufficient amount of blood, and therefore oxygen, resulting in ischemia and pain (Lewis et al., 2020).

The myocardium is constantly active, and it requires a continuous blood supply. When a coronary artery is sufficiently narrowed or blocked, the heart muscle it supplies works less efficiently. If ischemia continues unrelieved, the inadequate supply of oxygen to the heart tissue causes the cells to infarct or die. Dead tissue is referred to as necrotic.

Angina

A reduced blood supply will reduce the oxygen supply to heart muscle, as oxygen is carried on the hemoglobin molecule. An oxygen-starved heart muscle responds with a characteristic feeling of pain or discomfort called angina. Angina is caused by either a decreased supply of oxygen to the myocardium, an increased oxygen demand, or a combination of both. An estimated 9.8 million people in the United States are believed to have angina of some form or another, and over 500,000 new cases are diagnosed each year (Alaeddini & Shirani, 2018).

When its arteries are narrowed by atherosclerosis, a heart may still get enough oxygen to pump blood at rest. But exercise increases the work of the heart, and narrowed arteries cannot always deliver the excess oxygen required by an exercising heart. A person with narrowed coronary arteries will develop angina when exercising. One of the first symptoms of coronary artery disease is the appearance of angina when a person is working strenuously.

Acute Coronary Syndrome and Myocardial Infarction

Acute coronary syndrome includes unstable angina and two forms of myocardial infarction (MI). (Heart attack is the commonly used lay term for an MI.) The NSTEMI form of MI presents as non-ST segment elevation (presented on a 12-lead electrocardiogram). The STEMI form of MI presents with ST segment elevation and is an emergency situation. Either MI results in necrotic myocardial tissue, and it is essential to open the blocked artery(ies) to limit the size of the infarction by extension that occurs during continued compromised blood flow to the myocardium (Sole et al., 2021). (See also “Myocardial Infarction” later in this course.)

Unstable angina is newly occurring angina that occurs at rest or sleep, lasts more than 10 minutes, and occurs with increasing frequency (Lewis et al., 2020).

Preventative Measures

The progression of atherosclerosis can be slowed or even stopped by a few preventive measures. These include stopping smoking, maintaining a healthy weight for one’s height and age, exercising regularly, and eating a low-fat, balanced diet. This includes foods with a low glycemic index and the right sort of fats. To control atherosclerosis, it is also important to keep blood pressure low, reduce low-density cholesterol levels, increase high-density cholesterol levels, and treat diabetes by maintaining fasting glucose levels at 70–100 mg/dL.

People who develop symptomatic CAD should begin or continue these anti-atherosclerotic programs. They should take aspirin daily to prevent platelets aggregating or clumping together, and they should take other medications (typically, beta blockers) to reduce the workload of the heart. Nitroglycerin tablets can be used to alleviate or prevent anginal pain, and interventional procedures are available to widen narrowed arteries and maintain their newly expanded diameter.

Incidence and Impact

Cardiovascular diseases are the underlying causes of about 1 in 3 deaths in the United States, claiming more lives each year than all forms of cancer and chronic lower respiratory diseases combined. CAD is the leading cause (42%) of deaths attributable to cardiovascular diseases, followed by stroke (17%) and high blood pressure (11%). It is estimated that 13% of deaths in the United States, or 365,744 people per year, are due to heart disease. In addition, heart disease is the primary cause of death in women, taking more lives than all cancers combined. It is estimated that nearly one half of all middle-aged men and one third of middle-aged women in the United States will develop some form of the disease.

However, the U.S. annual death rate due to coronary heart disease has declined 27.9% between 2008 and 2018. This is believed to be influenced by improved public education, earlier initiation of treatment, and improved treatment modalities.

Coronary artery disease is not just a problem in the United States. Throughout the world, coronary artery disease causes more 18.6 million deaths annually and is responsible for more 13% of healthcare-related costs, more than any other single illness (AHA, 2021a).