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Introduction to ECGs Terry White, RN.

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Presentation on theme: "Introduction to ECGs Terry White, RN."— Presentation transcript:

1 Introduction to ECGs Terry White, RN

2 Discussion Topics ECG Monitoring Basics Standardized Methods & Devices
Components & Measurements of the ECG Complex ECG Analysis

3 ECG Monitoring

4 ECG Monitoring Recording of Electrical Activity
Uses Bipolar or Unipolar leads The ECG DOES NOT provide a recording or evaluation of Mechanical Activity!!!

5 ECG Monitoring Bipolar Leads 1 positive and 1 negative electrode
RA always negative LL always positive Traditional limb leads are examples of these Lead I Lead II Lead III Provide a view from a vertical plane

6 ECG Monitoring Unipolar Leads 1 positive electrode
1 negative “reference point” calculated by using summation of 2 negative leads Augmented Limb Leads aVR, aVF, aVL vertical plane Precordial or Chest Leads V1-V6 horizontal plane

7 ECG Monitoring Einthoven’s Triangle
Each lead “looks” from a different perspective Can determine the direction of electrical impulses Upright electrical recording indicates electricity flowing towards the + electrode positive deflection

8 Standardized Methods & Devices

9 Standardized Methods & Devices
ECG Paper Device Paper Speed Device Calibration Electrode Placement Variations Do Exist!

10 Standardized Methods & Devices
ECG Graph Paper Vertical axis- voltage 1 small box = 1 mm = 0.1 mV Horizontal axis - time 1 small box = 1 mm = 0.04 sec. Every 5 lines (boxes) are bolded Horizontal axis - 1 and 3 sec marks

11 Standardized Methods & Devices
ECG Paper Examples Vertical Axis No. of mm in 10 small boxes? No. of small boxes in 2 mm? Horizontal Axis No. of seconds in 5 small boxes? No. of small boxes in 0.2 second? No. of small boxes in 1 second?

12 Standardized Methods & Devices
Paper Speed & Calibration Paper Speed - 25 mm/sec standard Calibration of Voltage is Automatic Both Speed and voltage calibration can be changed on most devices

13 Standardized Methods & Devices
Electrode Placement Standardization improves accuracy of comparison ECGs 3 Lead and 12 Lead Placement are most common Assure good conduction gel Prep area with alcohol prep Avoid Bone Large muscles or hairy areas Limb vs. Chest placement

14 Standardized Methods & Devices
Electrode Placement Poor placement or preparation Often results in artifact Stray energy from other sources can also lead to poor ECG tracings (noise) 60 cycle interference

15 Components of the ECG

16 Components of the ECG Complex
Components & Their Representation P, Q , R, S, T Waves PR Interval QRS Interval ST Segment

17 Components of the ECG Complex
P Wave first upward deflection represents atrial depolarization usually 0.10 seconds or less usually followed by QRS complex

18 Components of the ECG Complex
QRS Complex Composition of 3 Waves Q, R & S represents ventricular depolarization much variability usually < 0.12 sec

19 Components of the ECG Complex
Q Wave first negative deflection after P wave depolarization of septum not always seen

20 Components of the ECG Complex
R Wave first positive deflection following P or Q waves subsequent positive deflections are R’, R”, etc

21 Components of the ECG Complex
S Wave Negative deflection following R wave subsequent negative deflections are S’, S”, etc may be part of QS complex absent R wave in aberrant conduction

22 Components of the ECG Complex
PR Interval time impulse takes to move through atria and AV node from beginning of P wave to next deflection on baseline (beginning of QRS complex) normally sec may be shorter with faster rates

23 Components of the ECG Complex
QRS Interval time impulse takes to depolarize ventricles from beginning of Q wave to beginning of ST segment usually < 0.12 sec

24 Components of the ECG Complex
J Point point where QRS complex returns to isoelectric line beginning of ST segment critical in measuring ST segment elevation

25 Components of the ECG Complex
ST Segment early repolarization of ventricles measured from J point to onset of T wave elevation or depression may indicate abnormality

26 Components of the ECG Complex
T Wave repolarization of ventricles concurrent with end of ventricular systole

27 ECG Analysis

28 ECG Analysis Rate Rhythm/Regularity QRS Complex P Waves
Relationships & Measurements

29 ECG Analysis Ventricular Rate Triplicate method R-R method
R-R method divide 300 by # of large squares between consecutive R waves 6 Second method multiply # of R waves in a 6 second strip by 10 Rate meter unreliable!!!

30 ECG Analysis Rhythm Measure R-R intervals across strip
Should find regular distance between R waves Classification Regular Irregular Regularly irregular Irregularly irregular

31 ECG Analysis QRS Complex Narrow Wide
< 0.12 seconds (3 small boxes) is normal indicates supraventricular origin (AV node or above) of pacemaker Wide > 0.12 seconds is wide indicates ventricular or supraventricular w/aberrant conduction

32 ECG Analysis P Waves Present? Do they all look alike? Regular interval
Upright or inverted in Lead II? Upright = atria depolarized from top to bottom Inverted = atria depolarized from bottom to top

33 ECG Analysis Relationships/Measurements PR Interval
Constant? Less than 0.20 seconds (1 large bx) P to QRS Relationship P wave before, during or after QRS? 1 P wave for each 1 QRS? Regular relationship?

34 ECG Analysis A monitoring lead can tell you:
How often the myocardium is depolarizing How regular the depolarization is How long conduction takes in various areas of the heart The origin of the impulses that are depolarizing the myocardium

35 ECG Analysis A monitoring lead can not tell you:
Presence or absence of a myocardial infarction Axis deviation Chamber enlargement Right vs. Left bundle branch blocks Quality of pumping action Whether the heart is beating!!!

36 ECG Analysis An ECG is a diagnostic tool, NOT a treatment
No one was ever cured by an ECG!! Treat the PATIENT not the Monitor!!!


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