In this section of our NREMT Study Guide, we will help you prepare for the Cardiology portion of the exam. This section covers the anatomy and physiology of the cardiovascular system, common disorders or conditions associated with the cardiovascular system and ischemic heart disease, the signs and symptoms of each to assist you in forming your differential diagnosis, and how to treat patients presenting with cardiac-related illnesses.
After you have reviewed this section of the study guide, there will be five practice questions to test your knowledge and retention of the material you have read.
Anatomy of the Cardiovascular System
As an EMT, a majority of medical emergencies you will respond to will be cardiac-related. In addition to knowing the signs and symptoms and how to treat cardiac emergencies, you must first understand the anatomy and physiology of the cardiovascular system.
The cardiovascular system is the primary system responsible for maintaining and supplying blood flow to the body. The cardiovascular system includes the heart, arteries, veins, and interconnecting capillaries. However, EMTs are taught the cardiovascular system consists of three main parts:
- The pump (the heart)
- A container (the blood vessels that reach the cells of the body)
- The fluid (blood and body fluids)
The Heart
The heart provides the body’s organs with a rich blood supply. Because of the heart’s responsibility to provide the blood supply to the body, it cannot permit disruption of blood flow for more than a few minutes. One unique feature of the heart is how it works as two paired pumps.
Each side of the heart has two chambers. The upper chambers are known as the atrium and the lower chambers are the ventricles. Both chambers pump blood in a controlled, systematic manner; the blood leaves each chamber through a one-way valve that prevents backflow and keeps the blood moving in the proper direction.
The right side of the heart receives deoxygenated blood from the body through the veins. It then pumps the oxygen-poor blood to the lungs, where the blood is oxygenated. The oxygen-rich blood is then pumped to the left side of the heart, where it is sent through arteries to the rest of the body. The left side of the heart is more muscular than the right, since it is responsible for pumping blood into the aorta and arteries to reach all the cells of the body.
The Blood Vessels
When blood flows out of the heart, it travels into the aorta, which is the largest artery in the body. As the arteries travel further away from the heart, they become smaller. The smaller blood vessels that connect the capillaries and arteries are called arterioles.
Capillaries are small tubes that pass among all of the body’s cells, linking the arterioles and venules. Blood that leaves the distal side of the capillaries flows into these tiny venules, which are thin-walled vessels that empty into the veins.
The veins empty their blood into what is known as the inferior and superior vena cavae. This constant process returns blood in the venous part of the circulatory system to the heart. Nutrients and oxygen pass seamlessly from the capillaries into the body’s cells, diffusing carbon dioxide and waste from the cells into the capillaries. This system allows the body to eliminate itself of these waste products.
The Blood
Blood is composed of red blood cells, white blood cells, platelets, and plasma. The red blood cells transport oxygen to the cells and move the carbon dioxide from the cells to the lungs. During exhalation, the carbon dioxide is removed from the body.
White blood cells are responsible for fighting infections and other diseases and are considered part of the body’s immune system. When a patient has a chronic illness or disease, it is often due to a low count of white blood cells in the body.
Platelets are responsible for the formation of blood clots that control blood loss when injured or when the body is affected by disease processes. When the body’s tissues are injured, platelets collect at the injury site, causing the red blood cells to get sticky and bond together. As the cells bond together, a protein found in plasma reinforces the developing clot and becomes a threadlike mesh that forms the clot itself.
Pathophysiology of the Cardiovascular System
Pathophysiology is defined as “the disordered physiological processes associated with disease or injury.” One disease covered in this study guide is ischemic heart disease, which occurs when there is a decrease in blood flow to one or more areas of the heart. When a patient has chest discomfort or pain, it is usually due to ischemia.
We will also cover five disorders or conditions associated with the cardiovascular system and ischemic heart disease so you can better understand the pathophysiology of the disease while assessing and treating your patients.
Atherosclerosis
Decreased blood flow to the heart tissue is often caused by coronary artery atherosclerosis, a disorder in which calcium and cholesterol form plaque inside the blood vessel’s walls. This buildup obstructs blood flow and decreases the vessel’s ability to contract and dilate. Over time, atherosclerosis can cause a complete occlusion (blockage) of a coronary artery, causing a disruption in blood flow to the heart.
Acute Coronary Syndrome
Acute coronary syndrome (ACS) is used to describe a group of symptoms caused by myocardial ischemia. There are two conditions that fall under ACS: angina pectoris and acute myocardial infarction (AMI). Since the signs and symptoms of both are very similar, they are generally treated the same.
Angina Pectoris
Angina pectoris, or angina, is the pain that occurs when a patient’s heart tissues are briefly not being supplied with sufficient oxygen. Angina can also be caused by a spasming artery, but it is most often a symptom of atherosclerosis. Angina generally occurs during physical activity or when a patient is under emotional stress due to a decreased oxygen supply while the heart is working hard.
Typically, angina will go away when the increased oxygen demand goes away, as when a patient stops exercising. Angina pain is usually described as squeezing, crushing, or as if an elephant is sitting on the patient’s chest. The pain can also radiate to the jaw, left arm, shoulder, mid-back, and upper abdomen.
If the pain does not diminish when the increased oxygen demand is limited, it most often goes away with supplemental oxygen and nitroglycerin.
Acute Myocardial Infarction
Acute myocardial infarction (AMI), in layman’s terms, is a heart attack. AMI pain signals the death of cells in the heart where blood flow is obstructed. Once the cells have died, there is no repairing or reviving them. The dead cells create scar tissue that puts added strain on the heart. This is the reason patients having an AMI need rapid transport to the hospital so arterial blockages can be cleared by physicians.
As mentioned before, the signs and symptoms of an AMI and angina are very similar and must be treated the same. However, there are three ways the pain of an AMI differs from angina that you should look for:
- The pain of an AMI may or may not be caused by exertion and can occur when a patient is sitting or sleeping.
- The pain does not resolve in a few minutes and can last between 30 minutes and several hours.
- The pain may or may not be relieved by resting or nitroglycerin.
Not all patients experiencing an AMI have pain and may not recognize they are having a heart attack. This lack of pain generally occurs in women, older adults, and patients with diabetes. They may have other signs and symptoms associated with ischemia, such as dyspnea, nausea and vomiting, or weakness.
Cardiogenic Shock
Cardiogenic shock most often occurs after an acute myocardial infarction (AMI), causing the heart to lack the power to force an adequate volume of blood through the circulatory system. This type of shock can occur immediately after an AMI or up to 24 hours after the onset of a heart attack.
The signs and symptoms of a patient in cardiogenic shock are a result of the body’s organs functioning improperly. Signs and symptoms of cardiogenic shock are similar to other types of shock, including:
- Anxiety or restlessness
- Altered level of consciousness
- Pale, cool, and clammy skin
- Tachycardia
- Shallow, rapid breathing
- Nausea and vomiting
- Hypotension (a late sign of decompensated shock)
Treatment of cardiogenic shock is the same as for other types of shock, including transporting the patient in a position of comfort, high-flow supplemental oxygen, keeping the patient warm, and providing ventilatory assistance if needed.
Congestive Heart Failure
Heart failure occurs when the ventricular heart muscle is permanently damaged and cannot keep up with the return blood flow from the atria. Congestive heart failure (CHF) is the result of heart valve damage, a heart attack, or a long history of high blood pressure.
When the heart cannot contract effectively, the muscle tries other ways to provide adequate cardiac output. The heart will increase the heart rate and enlarge the left ventricle to increase the amount of blood pumped each minute.
When the heart cannot maintain these adaptations, CHF will develop. The lungs become congested with fluid when the left side of the heart fails to effectively pump the blood away from the heart. The blood then tends to back up into the pulmonary veins, causing pulmonary edema.
The signs and symptoms of CHF are:
- Dyspnea
- Agitation
- Chest pain (in some patients)
- Distended neck veins
- Dependent edema
- Hypertension
- Tachycardia
- Pink, frothy sputum
- Tachypnea
- Pale or cyanotic and sweaty skin signs
- Rales (crackles) when auscultating breath sounds
Treatment for CHF includes transporting the patient in a sitting position with their legs hanging down, high-flow oxygen, and the use of continuous positive airway pressure (CPAP) and nitroglycerin if protocols allow.
Hypertensive Emergencies
Hypertension (high blood pressure) is considered any systolic blood pressure of 140 mm Hg or greater or diastolic pressure greater than 90 mm Hg. When a patient has a hypertensive emergency, it is defined as a systolic pressure of 180 mm Hg or greater or a rapid rise in their systolic pressure. Untreated hypertensive emergencies can lead to a dissecting aortic aneurysm or a cerebrovascular accident (CVA), commonly known as a stroke.
When there is a weakness in the wall of a patient’s aorta, it is called an aortic aneurysm. The aorta will dilate in the weakened area, making it susceptible to rupture. A dissecting aortic aneurysm is caused by a separation of the inner walls of the aorta, allowing high-pressure blood to flow in between the layers. The aorta then becomes significantly weakened, making it more susceptible to rupture from uncontrolled high blood pressure. When a patient’s aorta ruptures, the internal blood loss is so significant that the patient will die immediately.
The signs and symptoms of a dissecting aortic aneurysm include:
- Sudden onset of chest pain located in the anterior portion of the chest or in the back between the shoulder blades
- Abrupt chest pain without additional symptoms
- Sharp, tearing pain
- Differing blood pressures in each arm
- Diminished pedal pulses
- Decreased femoral or carotid pulses
Treatment for a dissecting aortic aneurysm includes keeping the patient calm, calling for ALS support if your protocols allow, high-flow oxygen, and rapid transport to the emergency department.