electrocardiography for healthcare professionals
DESCRIPTION
Learning Outcomes 2.1 Describe circulation as it relates to the ECG. 2.2 Recall the structures of the heart. 2.3 Differentiate between the pulmonary, systemic and coronary circulation. 2.4 Explain the cardiac cycle, and relate the difference between systole and diastole.TRANSCRIPT
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Electrocardiography for Healthcare Professionals
Chapter 2: The Cardiovascular
System
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Learning Outcomes2.1 Describe circulation as it relates to the ECG.
2.2 Recall the structures of the heart.
2.3 Differentiate between the pulmonary, systemic and coronary circulation.
2.4 Explain the cardiac cycle, and relate the difference between systole and diastole.
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Learning Outcomes (Cont’d)
2.5a Describe the parts and function of the conduction system.
2.5b Recall the unique qualities of the heart and their relationship to the cardiac conduction system.
2.5c Explain the conduction system as it relates to the ECG.
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Learning Outcomes (Cont’d)2.6a Identify each part of the ECG waveform.
2.6b Describe the heart activity that produces the ECG waveform.
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2.1 Circulation and the ECG Transports blood
Muscular pump
Electrical activity
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2.1 Apply Your Knowledge
What is the function of the heart?
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2.1 Apply Your Knowledge
What is the function of the heart?
ANSWER: To pump blood to and from body tissues
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2.2 Anatomy of the Heart
Lies in center of chest Under sternum Between the lungs The size of your fist Weighs 10.6 oz or 300
grams
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2.2 Heart Statistics
Average beats per minute = 72
Total output = 5 liters per minute
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2.2 Heart Anatomy Pericardium Pericardial space Epicardium Myocardium Endocardium
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2.2 Heart Layers
Click to Return to Last Screen Viewed
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2.2 Heart Chambers
Left Ventricle
Left Atrium
Right Ventricle
Right Atrium
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2.2 Heart Valves
Tricuspid valve Mitral (bicuspid) valve Semilunar valves
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2.2 Heart Vessels Vena cava Pulmonary artery Pulmonary veins Aorta Coronary arteries
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2.2 Heart Valves and Vessels
Click to Return to Last Screen Viewed
Using the on-screen pen, draw a line from the label to its location.
Vena Cava
Aorta
Pulmonary Veins
Pulmonary Artery
Tricuspid Valve
Bicuspid Valve
Aortic Valve
Pulmonary Valve
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2.2 Apply Your KnowledgeWhich valve of the heart lies between the left atrium and the left ventricle?
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2.2 Apply Your KnowledgeWhich valve of the heart lies between the left atrium and the left ventricle?
ANSWER: The mitral or bicuspid valve
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2.2 Apply Your Knowledge
Name the three layers of the heart.
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2.2 Apply Your Knowledge
Name the three layers of the heart.
ANSWER: The endocardium, myocardium, and epicardium
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2.3 Principles of Circulation
Pulmonary Systemic Coronary
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2.3 Pulmonary Circulation Enters right atrium
Blood passes through the tricuspid valve to the right
ventricle
Right ventricle pumps to the lungs
Blood returns into the left atrium
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2.3 Systemic Circulation Enters the left atrium and passes through into the left
ventricle The left ventricle pumps to the aorta From the aorta, blood circulates throughout the body Deoxygenated blood returns to the heart
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2.3 Coronary Circulation A
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2.3 Coronary Circulation B
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2.3 Coronary Circulation
Oxygenated blood travels from left ventricle to the
coronary arteries
Coronary arteries supply entire heart
Deoxygenated blood returns to the right atrium
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2.3 Apply Your Knowledge
Which vessels transport blood from the lungs to the left
atrium?
Great!
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2.3 Apply Your Knowledge
Which vessels transport blood from the lungs to the left
atrium?
ANSWER: The pulmonary veins
Great!
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2.4 The Cardiac Cycle
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2.4 The Cardiac Cycle (Cont’d)
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2.4 Diastole – Relaxation Phase Blood returns to the heart via the superior and inferior
vena cava Blood flows from the right atrium into the right ventricle Blood from the pulmonary veins flows from the left atrium
into the left ventricle
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2.4 Systole – Contraction Phase Contraction creates pressure, opening the pulmonary
and aortic valves Blood from the right ventricle flows to the lungs Blood from the left ventricle flows through the aorta to
the body
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2.4 Apply Your Knowledge
The relaxation phase of the cardiac cycle is known
as:
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2.4 Apply Your Knowledge
The relaxation phase of the cardiac cycle is known as:
ANSWER: Diastole
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2.5 Unique Qualities of the Heart
Automaticity
Conductivity
Contractivity
Excitability
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2.5 Regulation of the Heart Autonomic Nervous System
Speeds up or slows down the heart rate
Sympathetic branch can increase the heart rate
Parasympathetic branch can decrease the heart rate
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2.5 Pathways for Conduction
SA node AV node Bundle of His Bundle branches Purkinje fibers
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2.5 Sinoatrial (SA) Node Located in upper right portion of right atrium
Initiates the heartbeat
Pacemaker of the heart (60-100 beats per minute)
Normal conduction begins in SA node
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2.5 Atrioventricular (AV) Node Located on the floor of the right atrium
Causes delay in the electrical impulse, allowing for blood
to travel to ventricles
Can act as pacemaker if SA node is not working (40-60
bpm)
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2.5 Bundle of His (AV bundle) Located next to the AV node
Transfers electrical impulses from the atria to the
ventricles via bundle branches
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2.5 Bundle Branches
Split the electrical impulse down the right and left side From interventricular septum, the impulse activates
myocardial tissue, causing contraction Contractions occur in left-to-right pattern
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2.5 Purkinje Fibers Electrical pathway for each cardiac cell
Impulse activates left and right ventricles simultaneously
Produce an electrical wave
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2.5 Conduction System
Identify each part of the conduction system (A to H), then view the next slide for the answers.
A.
B.
C.D.
E. H.G.
F.
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2.5 Conduction System
A.
B.
C.D.
E. H.G.F.
A. SA nodeB. AV nodeC. AV bundleD. Purkinje fibersE. Interventricular septumF. Left bundle branchG. Right bundle branchH. Apex
Answers to Slide #44 above.
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2.5 Apply Your KnowledgeWhat is the ability of the heart to generate an electrical impulse called?
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2.5 Apply Your KnowledgeWhat is the ability of the heart to generate an electrical impulse called?
ANSWER: Automaticity
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Apply Your Knowledge
Which part of the conduction system is known as the pacemaker of the heart?
\
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Apply Your Knowledge
Which part of the conduction system is known as the pacemaker of the heart?
ANSWER: The sinoatrial or SA node
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2.6 Electrical Stimulation Depolarization
State of stimulation, preceding contraction
Electrical activation of heart cells
Causes the heart to contract
Most important electrical event
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2.6 Electrical Stimulation (Cont’d) Repolarization
State of cellular recovery, following contraction
Cell returns to a resting state
Heart relaxes, allowing for refilling of the chambers
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2.6 ECG Waveform
Recorded activity of depolarization and repolarization
Isoelectric line or baseline
Labeled P,Q,R,S,T
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2.6 ECG Waveform (Cont’d)
P wave
First positive deflection
Occurs when the atria depolarize
Small compared to other ECG waves
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2.6 ECG Waveform (Cont’d) QRS complex
Q wave Represents conduction of impulse down the
interventricular septum First negative deflection before the R wave Not always visualized on the ECG Less than 1/4 the height of the R wave
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2.6 ECG Waveform (Cont’d) QRS complex
R wave First positive wave of the QRS complex Represents conduction of electrical impulse to the
left ventricle Usually easiest to find
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2.6 ECG Waveform (Cont’d) QRS complex
S wave
First negative deflection after the R wave
Represents conduction of electrical impulse
through both ventricles
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2.6 ECG Waveform (Cont’d)
QRS complex Represents complete ventricular depolarization Reflects the time required for impulses to activate
the ventricular myocardium to contract
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2.6 ECG Waveform (Cont’d) ST segment
Measured from end of the S wave to the beginning of T wave
Indicates end of ventricular depolarization and beginning of ventricular repolarization
Elevated ST segment indicates myocardial damage
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2.6 ECG Waveform (Cont’d) T wave
Represents ventricular repolarization
Normal T wave is in same direction as R wave and P
wave
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2.6 ECG Waveform (Cont’d) U wave
Follows the T wave Represents repolarization of Bundle of His and
Purkinje fibers Not on all ECGs Presence can indicate an electrolyte imbalance
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2.6 ECG Waveform (Cont’d) PR interval
Measured from beginning of P wave to beginning of
QRS complex
Normal length of time is 0.12-0.20 second
Interval should be consistent
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2.6 ECG Waveform (Cont’d) QT interval
Time required for ventricular depolarization and repolarization to occur
Starts at beginning of QRS complex and ends at end of T wave
Includes QRS complex, ST segment, and T wave
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2.6 ECG Waveform (Cont’d) R to R interval
Measurement of time from start of one QRS complex to start of next QRS complex
Used to calculate heart rate Readily seen on ECG
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2.6 ECG Waveform (Cont’d) J point
Junction of the QRS interval and the ST interval
Represents end of the QRS complex and
ventricular depolarization
Important when measuring the length of the QRS
complex
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2.6 ECG Waveform (Cont’d)
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2.6 Apply Your Knowledge
Which wave on the ECG waveform represents
ventricular repolarization?
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2.6 Apply Your Knowledge
Which wave on the ECG waveform represents
ventricular repolarization?
ANSWER: T wave
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2.6 Apply Your Knowledge
What is the normal length of time for the PR interval?
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2.6 Apply Your Knowledge
What is the normal length of time for the PR interval?
ANSWER: 0.12 to 0.20 second
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Chapter Summary The heart consists of four chambers and four valves Blood travels through the pulmonary and systemic
circulation Coronary circulation supplies blood to the coronary
arteries
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Chapter Summary (Cont’d) The cardiac cycle consists of a contraction phase and a
relaxation phase
Diastole is known as the relaxation phase and systole is
the contraction phase
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Chapter Summary (Cont’d) The conduction system of the heart together maintains
electrical activity
The conduction system and conducting tissue have
qualities that control the heartbeat
The conduction system creates the electrical activity and
thus the ECG waveform
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Chapter Summary (Cont’d) Depolarization causes the heart to contract,
repolarization allows for cellular recovery
The ECG waveform includes the P wave, QRS complex,
T wave, U wave, PR interval, QT interval, and ST
segment
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Chapter Summary (Cont’d)
The ECG waveform is created by the various activities
of the conduction system