1. Electrocardiography for Healthcare Professionals
Chapter 2:
The Cardiovascular System

2. 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.

3. 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.

4. Learning Outcomes (Cont’d)
2.6a Identify each part of the ECG waveform. 2.6b Describe the heart activity that produces the ECG waveform.

5. 2.1 Circulation and the ECG
Transports blood
Muscular pump
Electrical activity
LO 2.1: Describe circulation as it relates to the ECG.
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Function of heart – pump blood to and from all the cells and tissues
Blood supplies nutrients & O2 and removes CO2 and waste products
Process of transporting blood is known as circulation
Circulation dependent upon the heart and its ability to contract or beat
The electrical activity of the heart causes the heart to contract
Each electrical activity of heart is recorded on the ECG
Knowledge of the heart, its functions, and what produces the ECG tracing will provide you with a clear understanding of the tasks you will be performing as an ECG healthcare professional

6. 2.1 Apply Your Knowledge
What is the function of the heart?

7. 2.1 Apply Your Knowledge What is the function of the heart?
Checkpoint questions
What is circulation? The process of transporting blood to and from the body tissues
What is recorded on the ECG strip? The electrical activity of the heart
ANSWER: To pump blood to and from body tissues

8. 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
LO 2.2: Anatomy of the Heart
2/3 of heart lies left of sternum

9. 2.2 Heart Statistics Average beats per minute = 72
Total output = 5 liters per minute
LO 2.2: Anatomy of the Heart powerful muscular pump
140 ml of blood per beat
Each day 1800 gallons enough to fill an average size bathtub about 36 times

10. 2.2 Heart Anatomy Pericardium Pericardial space Epicardium Myocardium
Endocardium
LO 2.2: Anatomy of the Heart
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Pericardium -Sack of tissue surrounding the heart
Two layers
Parietal layer is the tough outer layer
Visceral or epicardium layer is the inner layer and adheres closely to the heart
Purpose is to protect the heart from infection and trauma
Pericardial space
Between parietal and visceral layers of the pericardium
Contains approximately 10 to 20 mL of fluid
Serves to cushion the heart against trauma
Heart consists of three layers:
Epicardium – outer layer
Also known as the pericardium
Thin and contains the coronary arteries
Myocardium – middle, muscular layer, contracts the heart
Endocardium – inner layer
Lines the inner surfaces of the heart chambers and valves
Location of the Purkinje fibers is just below this layer

11. Click to Return to Last Screen Viewed
2.2 Heart Layers
LO 2.2: Anatomy of the Heart
Click to Return to Last Screen Viewed

12. 2.2 Heart Chambers Left Atrium Right Atrium Left Ventricle
LO 2.2: Anatomy of the Heart
Interventricular Septum
Varies in thickness
Thin in the atria
Thick in the Right ventricle
Thickest in the left ventricle
Thicker = stronger the muscular contraction of that chamber
Left ventricle sometimes know as the “workhorse of the heart”
Right Ventricle

13. 2.2 Heart Valves Tricuspid valve Mitral (bicuspid) valve
Semilunar valves
LO 2.2: Anatomy of the Heart
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Tricuspid valve – located between the right atrium and right ventricle
Mitral (bicuspid) valve – located between left atrium and left ventricle
Mitral and tricuspid valves also known as Atrioventricular (AV) valves prevent backflow of blood from the ventricles to the atria
The pulmonary artery and the aorta each have a semilunar valve
Half (semi)
Lunar (moon)
Semilunar valves prevent the backflow of blood into the ventricles
Flaps or cusps open to allow the blood to flow then close
AV valves open = semilunar valves closed

14. 2.2 Heart Vessels Vena cava Pulmonary artery Pulmonary veins Aorta
Coronary arteries
LO 2.2: Anatomy of the Heart
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Vena cava (largest vein in the body)
Superior vena cava returns blood from upper body to the heart
Inferior vena cava returns blood from lower body to the heart
Pulmonary artery
Carries deoxygenated blood from the right ventricle to the lungs
Pulmonary vein
Carries oxygenated blood from the lungs to the left atrium
Aorta
Carries blood from the left ventricle to the body
First branches from aorta are the coronary arteries
Coronary arteries
Supply blood to the heart muscle

15. 2.2 Heart Valves and Vessels
Aorta
Tricuspid Valve
Vena Cava
Bicuspid Valve
Aortic Valve
Pulmonary Artery
Pulmonary Valve
Pulmonary Veins
LO 2.2: Anatomy of the Heart
Click to Return to Last Screen Viewed
Using the on-screen pen, draw a line from the label to its location.

17. 2.2 Apply Your Knowledge
Which valve of the heart lies between the left atrium and the left ventricle?

18. 2.2 Apply Your Knowledge
Which valve of the heart lies between the left atrium and the left ventricle?
ANSWER: The mitral or bicuspid valve

19. 2.2 Apply Your Knowledge
Name the three layers of the heart.

20. 2.2 Apply Your Knowledge Name the three layers of the heart.
Checkpoint Questions LO 2.2
What is the name of the middle layer of the heart (the muscular layer)? Myocardium
Which valve is located between the left atrium and left ventricle? Bicuspid or mitral valve
ANSWER: The endocardium, myocardium, and epicardium

21. 2.3 Principles of Circulation
Pulmonary
Systemic
Coronary
L.O 2.3: Principles of Circulation

22. 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
L.O. 2.3: Principles of Circulation
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Pulmonary Circulation:
Deoxygenated blood enters the right atrium from the superior and inferior venae cavae.
Blood travels through the tricuspid valve into the right ventricle.
The right ventricle pumps the blood through the pulmonary semilunar valve into the pulmonary artery, then into the lungs. In the lungs, the blood is oxygenated.
The blood returns to the heart through the pulmonary veins into the left atrium. The left atrium is the last step of pulmonary circulation.

23. 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
L.O 2.3: Principles of Circulation
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Oxygenated blood enters the left atrium and travels through the mitral valve into the left ventricle.
The left ventricle pumps the blood through the aortic semilunar valve into the aorta.
After traveling through the body, the deoxygenated blood returns to the heart through the superior and inferior venae cavae.

24. 2.3 Coronary Circulation A
L.O. 2.3: Principles of Circulation

25. 2.3 Coronary Circulation B
L.O. 2.3: Principles of Circulation

26. 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
L.O. 2.3: Principles of Circulation
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Oxygenated blood from the left ventricle travels through the aorta to the coronary arteries.
Two main coronary arteries-left main and right main.
These arteries branch to supply oxygenated blood to the entire heart.
The left main artery has more branches because the left side of the heart is more muscular and requires more blood supply.
The deoxygenated blood travels through the coronary veins and is collected in the coronary sinus, which empties the blood directly into the right atrium.
The Heart as a Pump
Each ventricle pumps 70 mL of blood during contraction – this volume of blood that is ejected with each contraction is referred to as stroke volume
This amount varies depending on gender, level of fitness, disease state, or genetics
The volume of blood pumped each minute is referred to as cardiac output
Average cardiac output is approx. 5 liters/min.
Volume of blood decreases = heart rate decreases
Contractile force decreases = cardiac output decreases
Decreased output causes pallor, confusion, low blood pressure, nausea, and dizziness.
Cardiac output is estimated by multiplying heart rate by stroke volume HR x SV = CO

27. 2.3 Apply Your Knowledge Great!
Which vessels transport blood from the lungs to the left atrium?
Great!

28. 2.3 Apply Your Knowledge Great!
Which vessels transport blood from the lungs to the left atrium?
ANSWER: The pulmonary veins
Checkpoint questions(2.3):
What are the first vessels to branch off the aorta known as? Coronary arteries
Describe the three types of circulation.
The pathways for pumping blood to and from the lungs are known as pulmonary circulation.
The pathways for pumping blood throughout the body and back to the heart are known as systemic circulation.
The circulation of blood to and from the heart muscle is known as coronary circulation.
What is cardiac output? The volume pumped each minute is referred to as cardiac output.
Great!

29. 2.4 The Cardiac Cycle L.O 2.4: The Cardiac Cycle
Each beat has two phases – contraction and relaxation which together makeup the cardiac cycle
Relaxation = diastole – expanding and refilling
Contraction = systole – squeezing blood out

30. 2.4 The Cardiac Cycle (Cont’d)
L.O 2.4: The Cardiac Cycle

31. 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
L.O. 2.4: The Cardiac Cycle
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Blood from the upper body returns via the superior vena cava.
Blood from the lower body returns via the inferior vena cava.
The right atrium fills with blood, pushes open the tricuspid valve, and into the right ventricle.
Blood returns from the lungs via the pulmonary veins to the left atrium, then forces the mitral valve to open to allow blood flow to the left ventricle.

32. 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
L.O. 2.4: The Cardiac Cycle
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Blood is pushed into the lungs to exchange oxygen and carbon dioxide by the right ventricle.
Blood from the left ventricle is pushed through the aorta to be distributed through the body to provide oxygen for tissues and to remove carbon dioxide.
Listening with a stethoscope you will hear two sounds: “lubb” and “dupp” which are made by the opening and closing of the valves caused by the contraction of the heart
“Lubb” sound made during the systolic phase by the contraction of the ventricles and the closing of the mitral and tricuspid valves
“Dupp” sound is made during the diastolic phase. It is shorter and occurs during the beginning of ventricular relaxation.

33. 2.4 Apply Your Knowledge
The relaxation phase of the cardiac cycle is known as:

34. 2.4 Apply Your Knowledge
The relaxation phase of the cardiac cycle is known as:
ANSWER: Diastole
Checkpoint Questions (LO2.4)
What is the cardiac cycle? The contraction and relaxation of the heart together make up the cardiac cycle.
How are diastole and systole the same? They are both parts of the cardiac cycle.

35. 2.5 Unique Qualities of the Heart
Automaticity
Conductivity
Contractivity
Excitability
L.O. 2.5 a., b., c.: Conduction System of the Heart
Pumping cycle is controlled by electrical impulses – the impulses stimulate contraction of the heart muscle and absence of impulses allows the heart muscle to relax
Impulses are initiated by specialized pacemaker cells in the heart.
Impulses are transferred through the heart by the conduction system
The working cells respond by shortening, causing cardiac contraction and blood to flow
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Automaticity – heart’s ability to initiate an electrical impulse
Conductivity – ability of myocardial cells to receive and conduct (transmit) electrical impulses
Contractility – ability of the heart muscle to shorten in response to an electrical impulse
Excitability – ability of the heart to respond to an impulse or stimulus
Without these qualities the heart would not beat and would not be rhythmical

36. 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
L.O. 2.5 a., b., c.: Conduction System of the Heart
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In addition to automaticity, the heartbeat is controlled by the ANS, which is involuntary
Sympathetic branch can increase the heart rate in response to norepinephrine.
Happens when you are under stress or frightened
Normal rate of heart is 60 to 100 beats a minute
When sympathetic branch of ANS stimulated the heartbeat speeds up
Parasympathetic branch can decrease the heart rate via the vagus nerve.
Acts like the brake of the heart
Other factors can also affect the heart
Exercise, stress, or fever can increase the rate
The cardiac control center, in the brain, sends impulses to decrease the heart rate when the BP rises
Levels of potassium and calcium
Low potassium ions in the blood, heart rate decreases
High potassium ions causes abnormal heart rate or rhythm
Low calcium depresses heart actions
High calcium causes contractions that are longer then normal heart contractions

37. 2.5 Pathways for Conduction
SA node
AV node
Bundle of His
Bundle branches
Purkinje fibers
L.O. 2.5 a., b., c.: Conduction System of the Heart

38. 2.5 Sinoatrial (SA) Node
Located in upper right portion of right atrium
Initiates the heartbeat
Pacemaker of the heart ( beats per minute)
Normal conduction begins in SA node
L.O. 2.5 a., b., c.: Conduction System of the Heart
SA & AV nodes are small, round structures that consist of many specialized cardiac cells.
Automaticity of the fibers in the SA node produces the contraction of the right and left atria

39. 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)
L.O. 2.5 a., b., c.: Conduction System of the Heart

40. 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
L.O. 2.5 a., b., c.: Conduction System of the Heart
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The bundle branches are located along the left and right side of the interventricular septum.

41. 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
L.O. 2.5 a., b., c.: Conduction System of the Heart

42. 2.5 Purkinje Fibers Electrical pathway for each cardiac cell
Impulse activates left and right ventricles simultaneously
Produce an electrical wave
L.O. 2.5 a., b., c.: Conduction System of the Heart

43. 2.5 Conduction System A.
Identify each part of the conduction system (A to H), then view the next slide for the answers. B.
L.O. 2.5 a., b., c.: Conduction System of the Heart F. C. D. G. H. E.

44. 2.5 Conduction System A. B. C. D. E. H. G. F. SA node AV node
AV bundle
Purkinje fibers
Interventricular septum
Left bundle branch
Right bundle branch
Apex
Would recommend using Figure 2-9 on page 39 instead of current picture
Answers to Slide #44 above.

45. 2.5 Apply Your Knowledge
What is the ability of the heart to generate an electrical impulse called?

46. 2.5 Apply Your Knowledge
What is the ability of the heart to generate an electrical impulse called?
ANSWER: Automaticity

47. Apply Your Knowledge
Which part of the conduction system is known as the pacemaker of the heart? \

48. Apply Your Knowledge
Which part of the conduction system is known as the pacemaker of the heart?
Checkpoint Questions (LO 2.5a,b,c)
List the parts of the conduction system in the order the electrical impulse travels. Sinoatrial (SA) node (pacemaker), atrioventricular (AV) node, bundle of His (AV bundle), bundle branches, Purkinje fibers (network)
The ability of the heart muscle cell to respond to a stimulus is called Excitability
Where does the electrical impulse get delayed to allow all the blood to leave the atria before the ventricles contract? AV node
ANSWER: The sinoatrial or SA node

49. 2.6 Electrical Stimulation
Depolarization
State of stimulation, preceding contraction
Electrical activation of heart cells
Causes the heart to contract
Most important electrical event
L.O. 2.6 a., b., c.: Electrical Stimulation and the ECG Waveform
Polarization is the state during which the heart cells are at their peak resting energy.
During this portion of the cycle, the cells are electrically polarized.
This means the inside of the cell is negatively charge in relation to the outside of the cell
Depolarization is a state of cellular stimulation which precedes contraction. It is the electrical activation of the cells of the heart when the electrical charge is reversed across the cell membrane so the interior becomes positively charged. This rapid change in polarization is known as action potential
Most important electrical event in the heart—it causes the heart to contract and pump blood to the body

50. 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
L.O. 2.6 a., b., c.: Electrical Stimulation and the ECG Waveform

51. 2.6 ECG Waveform
Recorded activity of depolarization and repolarization
Isoelectric line or baseline
Labeled P,Q,R,S,T
L.O. 2.6 a., b., c.: Electrical Stimulation and the ECG Waveform
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Isoelectric line or baseline is when no electrical activity occurs.
Discovered by Einthoven.
Deflections, which appear as waves on the ECG tracing, indicate electrical activity in the heart Up = positive down = negative
U wave was added later. Each of the waves indicates specific activity in the heart
An ECG waveform contains intervals, segments, and complexes in addition to the waves – QRS complex, ST segment, the PR interval, and the QT interval

52. 2.6 ECG Waveform (Cont’d) P wave First positive deflection
Occurs when the atria depolarize
Small compared to other ECG waves
L.O. 2.6 a., b., c.: Electrical Stimulation and the ECG Waveform
During the delay of conduction that occurs at the AV node, a small baseline segment is seen on the waveform. There is no electrical activity occurring (depolarization or repolarization). It is during this time that atrial kick occurs. Atrial kick occurs when the blood is ejected into the ventricles by the atria.

53. 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
L.O. 2.6 a., b., c.: Electrical Stimulation and the ECG Waveform
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The next three waves occur together as the QRS complex
QRS complex represents ventricular depolarization.

54. 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
L.O. 2.6 a., b., c.: Electrical Stimulation and the ECG Waveform

55. 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
L.O. 2.6 a., b., c.: Electrical Stimulation and the ECG Waveform

56. 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
L.O. 2.6 a., b., c.: Electrical Stimulation and the ECG Waveform
QRS complex represents ventricular depolarization and is reflective of the time it takes for the impulses to depolarize the interventricular septum down through the ventricular myocardium causing the ventricles to contract

57. 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
L.O. 2.6 a., b., c.: Electrical Stimulation and the ECG Waveform
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Normally on the isoelectric line.
The reason this segment is studied in a 12-lead ECG recording is to determine whether there is any ischemia or myocardial (heart) damage. Ischemia , which is lack of blood causing reduced oxygen to the heart muscle and either an elevation or depression of the segment depending upon the extent of the ischemia and the amount of damage to the cardiac cells.

58. 2.6 ECG Waveform (Cont’d) T wave Represents ventricular repolarization
Normal T wave is in same direction as R wave and P wave
L.O. 2.6 a., b., c.: Electrical Stimulation and the ECG Waveform
As repolarization occurs the ventricular muscles relax
The T wave look like a small mountain with one sloping side

59. 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
L.O. 2.6 a., b., c.: Electrical Stimulation and the ECG Waveform

60. 2.6 ECG Waveform (Cont’d) PR interval
Measured from beginning of P wave to beginning of QRS complex
Normal length of time is second
Interval should be consistent
L.O. 2.6 a., b., c.: Electrical Stimulation and the ECG Waveform
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This time interval represents the time the electrical impulse is initiated until
the ventricles are stimulated by the impulse to start the contraction.

61. 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
L.O. 2.6 a., b., c.: Electrical Stimulation and the ECG Waveform
Many variables such as the heart rate, coronary artery disease, electrolyte imbalance, and antidysrhythmic medications affect QT intervals
Longer than normal QT interval may indicate that the patient is at an increased risk for certain ventricular dysrhythmias and sudden cardiac death
If the heart rate exceeds 100 beats/min. the QT interval is of little clinical significance due to the intervals closing as a result of the increased heart rate.

62. 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
L.O. 2.6 a., b., c.: Electrical Stimulation and the ECG Waveform
R-R can only be used to calculate the heart rate if the rhythm is regular

63. 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
L.O. 2.6 a., b., c.: Electrical Stimulation and the ECG Waveform
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The J point is important when measuring the length of the QRS complex and
interpreting the ECG tracing. A normal QRS complex is 0.06 to 0.1 second.

64. 2.6 ECG Waveform (Cont’d)
L.O. 2.6 a., b., c.: Electrical Stimulation and the ECG Waveform

65. 2.6 Apply Your Knowledge
Which wave on the ECG waveform represents ventricular repolarization?

66. 2.6 Apply Your Knowledge
Which wave on the ECG waveform represents ventricular repolarization?
ANSWER: T wave

67. 2.6 Apply Your Knowledge
What is the normal length of time for the PR interval?

68. 2.6 Apply Your Knowledge
What is the normal length of time for the PR interval?
ANSWER: 0.12 to 0.20 second
Checkpoint Questions (LO 2.6a, b, c)
Which electrical event is represented by the cardiac contraction of the heart? Depolarization
Which wave represents the atrial depolarization? Ventricle repolarization? P wave (atrial), T wave (ventricular)
What is ischemia? Lack of blood causing reduced oxygen to the heart muscle; can result in a change in the ST segment.

69. 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

70. 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

71. 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

72. 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

73. Chapter Summary (Cont’d)
The ECG waveform is created by the various activities of the conduction system