1. Electrocardiogram (ECG) Basics interpretation
Manal Alramly, MSN, RN
Sondos Eqylan, MSN, RN
Adult (1) Clinical

2. Objectives By the end of this session the students will be able to:
Review Structures and Functions of Cardiovascular System, and conduction system
Recognize ECG different waves and segments.
Review ECG lead placement
Recall the 12 ECG leads, location and view of the heart wall
Analyze an ECG strip reporting: heart rate, rhythm, intervals, segments, and waves.
Define the characteristics of: normal sinus rhythm
Recognize sinus bradycardia, and sinus tachycardia.
Recognize significant ischemic myocardial changes as reflected on the ECG.

3. Structures and Functions of Cardiovascular System
Heart is located in the mediastinum area
Four chambers
Composed of three layers
1- Endocardium (endothelial tissue lines inside the heart and valves)
2- Myocardium (muscle fiber responsible of pumping action)
3- Epicardium (serous outer layer of the heart)
Pericardium (visceral and parietal)
Left ventricular wall 2-3 times thicker than right
Structures
The heart is a four-chambered hollow muscular organ normally the approximate size of a fist. It lies within the thorax in the mediastinal space that separates the right and left pleural cavities.
The heart is composed of three layers: a thin inner lining, the endocardium; a layer of muscle, the myocardium; and an outer layer, the epicardium.
The heart is covered by a fibroserous sac called the pericardium. This sac consists of two layers: the inside (visceral) layer of the pericardium (the epicardium) and the outer (parietal) layer.
A small amount of pericardial fluid (approximately 10 to 15 mL) lubricates the space between the pericardial layers (pericardial space) and prevents friction between the surfaces as the heart contracts.
The heart is divided vertically by the septum. The interatrial septum creates a right and a left atrium, and the interventricular septum creates a right and a left ventricle. The thickness of the wall of each chamber is different. The atrial myocardium is thinner than that of the ventricles, and the left ventricular wall is 2 to 3 times thicker than the right ventricular wall.

4. Cardiac Chambers and Valves
The four valves of the heart serve to keep blood flowing in a forward direction.
The cusps of the mitral and tricuspid valves are attached to thin strands of fibrous tissue termed chordae tendineae. Chordae are anchored in the papillary muscles of the ventricles. This support system prevents eversion of the leaflets into the atria during ventricular contraction.
The pulmonic and aortic valves (also known as semilunar valves) prevent blood from regurgitating into the ventricles at the end of each ventricular contraction.

5. Conduction System
The conduction system is specialized nerve tissue responsible for creating and transporting the electrical impulse, or action potential. This impulse starts depolarization and subsequently cardiac contraction.
The electrical impulse is normally started by the sinoatrial (SA) node (the pacemaker of the heart). Each impulse coming from the SA node travels through interatrial pathways to depolarize the atria, resulting in a contraction.
The electrical impulse travels from the atria to the AV node through internodal pathways. The excitation then moves through the bundle of His and the left and right bundle branches. The left bundle branch has two fascicles (divisions): anterior and posterior.
The action potential moves through the walls of both ventricles by means of Purkinje fibers. The ventricular conduction system delivers the impulse within 0.12 second. This triggers a synchronized right and left ventricular contraction.
The result of the cardiac cycle is the ejection of blood into the pulmonary and systemic circulation. It ends with repolarization, when the contractile fiber cells and the conduction pathway cells regain their resting polarized condition.
Cardiac muscle cells have a compensatory mechanism that makes them unresponsive or refractory to restimulation during the action potential. During ventricular contraction, an absolute refractory period occurs, during which cardiac muscle does not respond to any stimuli. After this period, cardiac muscle gradually recovers its excitability, and a relative refractory period occurs by early diastole.

6. Cardiac Conduction System

7. Primary Cardiac Cell Characteristics
Automaticity – ability of the cardiac cells to initiate an electrical impulse (spontaneous electrical conduction)
Excitability - ability to respond to electrical impulse
Conductivity – ability to transmit message or electrical impulse from one cell to another

8. Electrical and Mechanical activities
Depolarization: electrical activation of cell caused by influx of sodium into cell while potassium exits cell
Repolarization: return of cell to resting state by efflux of potassium outward cell.
Electrical contraction = Depolarization
Electrical relaxation= Repolarization
Mechanical contraction = systole
Mechanical relaxation = diastole

10. Willem Einthoven

13. ECG Paper measurement

16. ECG Paper measurement ECG Paper
ECG paper is traditionally divided into 1mm squares Vertically, ten blocks (small Box) usually correspond to 1 mV.
The horizontal axis of the paper speed is usually 25mm/s.
Each large square( Box) consists of five small squares.
Each large square ( Box) equals 0.2 second.
Each small square ( Box) equals 0.04 second.

17. Always check the calibration voltage on the ECG, speed 25 mm per second The following image shows the normal 1mV calibration spike

18. Waves, Intervals, Segments

22. Waves, Intervals, Segments
P wave:
Represents atrial depolarization
Round, upward deflection
Duration =or< 0.11 seconds .
Amplitude =or< 2.5 mm high.

23. Waves, Intervals, Segments
PR interval:
Start at p wave to begin of QRS complex
Represents time for atrial depolarization( the duration of time required for an electrical impulse to spread from the SA node, through the atrial muscle and the delay of impulse in the AV node before ventricular depolarization.
Duration: second (3-5 small squares).

24. Waves, Intervals, Segments
Q wave: Duration <0.03sec.
Amplitude less than 25% of the R wave.
QRS complex:
Represents ventricular depolarization.
Duration : 0.06 – 0.10 second, less than 3 small squares
Narrow complex
Widening occurs when the ventricles become hypertrophied or when there is disease involving the bundle branches or their fascicles.

25. Waves, Intervals, Segments
T wave:
Represents ventricular Repolarization.
Deflection as the QRS complex direction.
T wave inversion indicate Myocardium Ischemia.
ST segment:
Early ventricular Repolarization
End of S to begin of T wave.
Normally on the isoelectric line
Isoelectric line: is a reference line extending horizontally between the bases of the P and T waves.

26. Waves, Intervals, Segments
QT Interval:
Total time for ventricular depolarization and repolarization.
From the beginning of the Q wave to the end of the T wave.
Vary with heart rate, faster heart rate leads to shorter QT.
QT interval: seconds.

27. Twelve Leads ECG
Electrodes placement: six limb leads (three standard and three augmented) and six precordial leads.
Twelve Leads .
- Six leads are chest leads from V1 to V6 extending across the pericordium.
Three standard bipolar limb leads which are : I, II, III.
Three augmented voltage unipolar limb leads which are: AVR, AVL, AVF.

28. Lead placement( pericardium)
V1: 4th Intercostal space at right sternal border
V2: 4th Intercostal space at left sternal border
V3: Midway between V2 and V4
V4: 5th Intercostal space at left Midclavicular line
V5: 5th Intercostal space at left anterior axillary line Anterior-axillary line
V6: 5th Intercostal space at left mid axillary line Mid-axillary line

30. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

31. Lead placement( limb lead)
Use the color for lead placement; Read= (red) right arm (AVR) Your= (yellow ) left arm (AVL) Green= (green) left foot (AVF) Book= (black) right foot (for grounding/earthing)

34. Lead placement( limb lead)
Lead I: will measure the electrical potential differences between AVR and AVL
Lead II: will measure the electrical potential differences between AVR and AVF
Lead III: will measure the electrical potential differences between AVL and AVF.

35. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

36. ECG leads and Anatomic Groups

40. Break

41. Assessment of Cardiac Rhythm
Regularity (Regular or Irregular)
Rate
P wave
QRS complex
P wave : QRS complex
T wave
P-R interval ( sec)
QRS complex width ( sec)
ST segment
Q-T interval ( sec)
When assessing a cardiac rhythm, use a consistent and systematic approach. One such approach includes the following:
1. Look for the presence of the P wave. Is it upright or inverted? Is there one for every QRS complex or more than one? Are there atrial fibrillatory or flutter waves present?
2. Evaluate the atrial rhythm. Is it regular or irregular?
3. Calculate the atrial rate.
4. Measure the duration of the P-R interval. Is it normal duration or prolonged?
5. Evaluate the ventricular rhythm. Is it regular or irregular?
6. Calculate the ventricular rate.
7. Measure the duration of the QRS complex. Is it normal duration or prolonged?
8. Assess the ST segment. Is it isoelectric (flat), elevated, or depressed?
9. Measure the duration of the Q-T interval. Is it normal duration or prolonged?
10. Note the T wave. Is it upright or inverted?
Additional questions to consider include the following:
1. What is the dominant or underlying rhythm and/or dysrhythmia?
2. What is the clinical significance of your findings?
3. What is the treatment for the particular rhythm?

42. Criteria for Normal Sinus Rhythm (NSR)
1. Rhythm = Regular
2. Rate = beat / minute.
3. Presence of P, QRS, T in each cycle.
4. P : QRS ratio = 1 : 1
5. Normal shape, time of waves, segments and intervals
6. absence of Acute ST-T changes

44. Heart Rate Calculation
300 Large boxes = 60 seconds (1min.) 300/10 =60/10 30 Large boxes = 6 seconds 15 Large boxes =3 sec. 1- Regular ECG HR = 300/ number of large squares between R-R interval or HR = 1500/ number of small squares between R-R ( more precise ) HR = 1500/30 = 50 b/m ; HR = 300/6 = 50 b/m ( note R-R intervals are equal)

45. Heart Rate Calculation

46. Heart Rate Calculation
Irregular ECG
- Take a rhythm strip for 6 seconds which corresponds to 30 large squares.
- Count the number of R-R interval in the 6 second strip and multiply the number by 10
Example HR = 8*10 = 80 beat/minute .

48. Sinus Bradycardia Normal sinus rhythm except rate < 60 b\m
causes = athletes, myocardial infraction.

51. Sinus Tachycardia Normal sinus rhythm except rate > 100b\m
causes: exercise, stress, CHF, lung disease and hyperthyroidism.

54. Arrhythmias Definition of arrhythmias :
Any disturbance in the rate, regularity, site or origin, or conduction of cardiac electrical impulse. It can be single beat or sustained rhythm.
Clinical Manifestations:
Palpitation.
Light headedness and syncope R/T low cardiac output.
Angina R/T increased O2 demand.
Sudden death.

55. Causes: [ HISDEBS ] Arrhythmias H = Hypoxia. I = Ischemia.
S = Sympathetic stimulation.
D = Drugs.
E = Electrolyte disturbances.
B = Bradycardia.
S = Stretch = cardiac enlargement

56. ECG ischemic Changes
ECG ischemic Changes
* ST segment depression
* T inversion
* ST elevation
- Cardiac Ischemia: decreased coronary blood flow to the myocardium which could lead to tissue injury and necrosis ( tissue death ).

57. ST Depression (MORE THAN 1 mm FROM
Iso-Electric Line) or T inversion:
Myocardium Ischemia
ST Elevation (MORE THAN 1 mm FROM
Iso-Electric Line):
Myocardium injury
Iso-Electric Line) and pathological Q wave :
Myocardium Infarction

58. Changes Associated With Myocardial Ischemia
The isoelectric line is flat and represents those normal times in the cardiac cycle when the ECG is not recording any electrical activity in the heart. These times are as follows: (1) from the end of the P wave to the start of the QRS complex, (2) during the entire ST segment, and (3) from the end of the T wave to the start of the next P wave.
Note the changes in the above visual.
ST segment is depressed on left (note normal flat ST segment at same level of isoelectric line on right).
ECG on right depicts T wave inversion.
Patients with ischemia may display one or both changes.
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

59. Changes Associated With Infarction
Note the deep, wide Q wave, indicating the presence of a myocardial infarction.
T wave inversion related to MI occurs within hours following the event and may persist for months.
The ECG changes seen in injury and MI reflect electrical disturbances in the myocardial cells caused by a prolonged lack of blood and oxygen leading to necrosis.
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

60. ECG Changes Associated With Acute Coronary Syndrome (ACS)
Injury
ST-segment elevation occurs
Significant if >1 mm above the isoelectric line
If treatment is prompt and effective, may avoid or limit infarction
Absence of serum cardiac markers confirms no infarction
Infarction
Physiologic Q wave is the first negative deflection following the P wave
Small and narrow (<0.04 second in duration)
Pathologic Q wave is deep and >0.03 second in duration
Myocardial injury represents a worsening stage of ischemia that is potentially reversible but may evolve to MI.
The typical ECG change seen during injury is ST-segment elevation.
ST-segment elevation is significant if it is greater than or equal to 1 mm above the isoelectric line.
If treatment is prompt and effective, it is possible to restore oxygen to the myocardium and avoid or limit infarction.
The absence of serum cardiac markers confirms this.

62. ECG Finding With Anterolateral Wall MI
ECG findings with anterolateral wall myocardial infarction. Normally, leads I, aVL, and V1 to V3 have positive R wave. Note the pathologic Q waves in these leads and the ST-segment elevation in leads V2 to V5 (arrows).
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

63. You will see artifact on the monitor when leads and electrodes are not secure, or if there is muscle activity (e.g., shivering) or electrical interference.
Artifact is a distortion of the baseline and waveforms seen on the ECG.
Accurate interpretation of cardiac rhythm is difficult when artifact is present. If artifact occurs, check the connections in the equipment. You may need to replace the electrodes if the conductive gel has dried out.
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

66. Thank you