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Unit 1: Anatomy and the ECG

Lesson 1: ECGs and the Heart

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Lesson 1 – ECGs and the Heart

Electrocardiogram (ECG or EKG)

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Lesson 1 – ECGs and the Heart

Layers of the heart

Pericardium

Myocardium

Endocardium

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Lesson 1 – ECGs and the Heart

Chambers of the heart

Septum

Atria

Ventricles

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Lesson 1 – ECGs and the Heart

Heart valves

Atrioventricular

Tricuspid
Bicuspid / Mitral

Semilunar

Pulmonary
Aortic

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Lesson 1 – ECGs and the Heart

Circulation of blood

Pulmonary

Systemic

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Lesson 1 – ECGs and the Heart

Path of blood through heart

Right atrium
Tricuspid valve
Right ventricle
Pulmonary valve
Left atrium
Bicuspid / mitral valve
Left ventricle
Aortic valve

Path of Blood through the Heart

When deoxygenated blood returns from the body, it follows this path through the heart.

1) The right atrium receives deoxygenated blood from the body through the inferior and superior vena cava.

2) The blood moves to the lower portion of the heart through the tricuspid valve. The valve prevents blood from moving back into the right atrium. 3) The right ventricle fills with blood.

4) The right ventricle contracts to send the blood through the pulmonary valve to the pulmonary artery and the lungs. The valve prevents blood from returning to the right ventricle.

5) The left atrium receives oxygenated blood from the lungs through the pulmonary veins.

6) The blood moves to the lower portion of the heart through the bicuspid (mitral) valve. The valve prevents blood from moving back into the left atrium.

7) The left ventricle fills with blood.

8) The blood leaves the heart through the aortic valve to the aorta, which sends the blood to all parts of the body. The valve prevents blood from returning to the left ventricle

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Unit 1: Anatomy and the ECG

Lesson 2: Heartbeat and the ECG Cycle

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Lesson 2 – Heartbeat and the ECG Cycle

Heartbeat

Electrical impulses stimulate contractions

Cycle

Contract and push
Relax and fill

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Lesson 2 – Heartbeat and the ECG Cycle

Cardiac cycle (heartbeat)

Systole
Diastole

Tissues transmit electrical impulses

Sinoatrial node
Atrioventricular node
Bundle of His
Purkinje fibers

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Lesson 2 – Heartbeat and the ECG Cycle

Path of electrical impulses

Sinoatrial node
Atria
Atrioventricular node
Bundle of His
Purkinje fibers

Path of Electrical Impulses

During each cardiac cycle, the electrical impulses in the heart follow the path below:

1) The sinoatrial (SA) node sends out an electrical impulse that begins the heartbeat and sets its rhythm, or pattern. The SA node is also known as the sinus node or the body's "natural pacemaker.“

2) The electrical impulse from the SA node moves through the atria, causing them to contract first.

3) From the atria, the impulse travels to the atrioventricular (AV) node. Here the impulse is slightly delayed to give the atria time to fully contract and fill the ventricles with blood.

4) Then the AV node passes the impulse to the bundle of His.

5) The impulse continues along the branches of the bundle of His to the Purkinje fibers. This network of fibers spreads the impulse to the ventricles, causing them to contract.

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Lesson 2 – Heartbeat and the ECG Cycle

ECG cycle

Electrical activity

Waves

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Lesson 2 – Heartbeat and the ECG Cycle

ECG cycle

P wave / atrial depolarization

QRS complex of waves / ventricular depolarization

T wave / repolarization

U wave

What the ECG Cycle Shows

The series of waves in the ECG cycle gives a picture of the cardiac cycle.

The P wave on the graph shows atrial depolarization. This state occurs when the impulse starts in the SA node and causes the atria to contract.

The QRS complex of waves shows ventricular depolarization. This state occurs when the impulse moves through the AV node, bundle of His, and Purkinje fibers and causes the ventricles to contract.

The T wave shows repolarization. This state occurs during a time of electrical recovery. Then the ventricles relax briefly before the cycle starts again.

A U wave although not seen on every ECG, is characterized by a small upward curve during which there is repolarization of the Purkinje fibers. It is often indicative of electrolyte imbalance.

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Unit 1: Anatomy and the ECG

Lesson 3: Recognizing Cardiac Emergencies

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Lesson 3 – �Recognizing Cardiac Emergencies

Not every patient who has chest pain is having a heart attack

Cardiac compromise – the abnormal function of the heart
Cardiac arrest – when the patient is both apneic and pulseless

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Lesson 3 – �Recognizing Cardiac Emergencies

Atherosclerosis – the stiffening of blood vessels due to a buildup of fatty plaques
Myocardial ischemia – a reduction in blood flow to the heart
Acute coronary syndrome – any one of several serious heart conditions

Atherosclerosis

Atherosclerosis is the stiffening of blood vessels due to a buildup of fatty plaques. The blood vessels become narrowed and impede the flow of blood. Eventually, the vessel can become completely or almost entirely occluded from the plaque buildup alone or by a blood clot that becomes lodged in the narrowed vessel. Atherosclerosis is a disease that affects the cardiovascular system but is not considered a cardiac emergency. Although atherosclerosis is often considered a heart problem, it can affect arteries anywhere in the body.

When atherosclerosis affects the coronary arteries, it is called coronary artery disease or coronary heart disease. This can then lead to myocardial ischemia, which is a reduction in blood flow to the heart. The patient experiences chest pain and other symptoms indicative of an acute coronary syndrome. An acute coronary syndrome is any one of several serious heart conditions.

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Lesson 3 – �Recognizing Cardiac Emergencies

Reduced blood flow of myocardial ischemia is usually the result of a partial or complete blockage of the heart’s arteries (coronary arteries).

Angina – a condition marked by severe pain in the chest that often spreads to the shoulders, arms, and neck.
Levine’s sign – clenching of a fist over the center of the chest

Myocardial Ischemia and Angina

Myocardial ischemia occurs when blood flow to the heart is reduced, preventing it from receiving enough oxygen. The reduced blood flow is usually the result of a partial or complete blockage of the heart’s arteries (coronary arteries). This can happen through atherosclerosis, a blood clot, or a need for additional oxygen, such as with exercise. A sudden, severe blockage of a coronary artery can lead to a heart attack.

Angina is a condition marked by severe pain in the chest that often spreads to the shoulders, arms, and neck. It is caused by inadequate blood supply to the heart (myocardial ischemia). Angina is the most common symptom of cardiac compromise.

The chest pain typical of cardiac compromise centers around the sternum and radiates down the abdomen and arms, and to the shoulders, jaw, or back. Levine's sign, which is the clenching of a fist over the center of the chest, is a signal of severe pain. In other cases, the chest pain presents as general chest discomfort or backache, usually between the shoulder blades. Other patients have no chest or back discomfort at all. The pain is often made worse upon exertion.

Any patient that complains of chest pain or discomfort, or has other common symptoms, should be managed as a heart attack.

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Lesson 3 – �Recognizing Cardiac Emergencies

The following conditions can also indicate heart failure:

Pupils that are dilated or sluggish
Cyanosis of mucous membranes
Jugular venous distension (JVD) - abnormal engorging of the jugular veins
Wheezing or crackles upon auscultation
Peripheral edema - swelling of tissue in the feet and legs as a result of excess fluid

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Lesson 3 – �Recognizing Cardiac Emergencies

Most common symptoms of cardiac compromise and acute coronary syndrome:

Discomfort in the chest, abdomen, left arm or shoulder, or jaw
Sudden diaphoresis
Shortness of breath or coughing
Cool, pale skin
Lightheadedness
Anxiety or feeling of impending doom
Nausea and vomiting
Headache
Abnormal blood pressure
Abnormal pulse rate

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Lesson 3 – �Recognizing Cardiac Emergencies

Women, the elderly, and patients with diabetes are high-risk groups that often present with atypical symptoms, including:

Pressure in the chest
Shortness of breath
Neck ache or back pain
Tingling of the fingers
Fatigue or water weight gain
Insomnia

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Lesson 3 – �Recognizing Cardiac Emergencies

Pediatric patients rarely exhibit cardiac problems unless they are congenital or present at birth.
Geriatric patients can present with atypical symptoms of cardiac compromise.