Introduction to ecgs
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Introduction to ECGs. Terry White, RN. Discussion Topics. ECG Monitoring Basics Standardized Methods & Devices Components & Measurements of the ECG Complex ECG Analysis. ECG Monitoring. ECG Monitoring. Recording of Electrical Activity Uses Bipolar or Unipolar leads.

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Introduction to ecgs

Introduction to ECGs

Terry White, RN


Discussion topics

Discussion Topics

  • ECG Monitoring Basics

  • Standardized Methods & Devices

  • Components & Measurements of the ECG Complex

  • ECG Analysis


Ecg monitoring

ECG Monitoring


Ecg monitoring1

ECG Monitoring

  • Recording of Electrical Activity

  • Uses Bipolar or Unipolar leads

The ECG DOES NOT provide a recording or evaluation of MechanicalActivity!!!


Ecg monitoring2

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


Ecg monitoring3

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


Ecg monitoring4

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


Standardized methods devices

Standardized Methods & Devices


Standardized methods devices1

Standardized Methods & Devices

  • ECG Paper

  • Device Paper Speed

  • Device Calibration

  • Electrode Placement

  • Variations Do Exist!


Standardized methods devices2

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


Standardized methods devices3

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?


Standardized methods devices4

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


Standardized methods devices5

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


Standardized methods devices6

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


Components of the ecg

Components of the ECG


Components of the ecg complex

Components of the ECG Complex

  • Components & Their Representation

    • P, Q , R, S, T Waves

    • PR Interval

    • QRS Interval

    • ST Segment


Components of the ecg complex1

Components of the ECG Complex

  • P Wave

    • first upward deflection

    • represents atrial depolarization

    • usually 0.10 seconds or less

    • usually followed by QRS complex


Components of the ecg complex2

Components of the ECG Complex

  • QRS Complex

    • Composition of 3 Waves

      • Q, R & S

      • represents ventricular depolarization

      • much variability

    • usually < 0.12 sec


Components of the ecg complex3

Components of the ECG Complex

  • Q Wave

    • first negative deflection after P wave

    • depolarization of septum

    • not always seen


Components of the ecg complex4

Components of the ECG Complex

  • R Wave

    • first positive deflection following P or Q waves

    • subsequent positive deflections are R’, R”, etc


Components of the ecg complex5

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


Components of the ecg complex6

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 0.12 - 0.2 sec

    • may be shorter with faster rates


Components of the ecg complex7

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


Components of the ecg complex8

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


Components of the ecg complex9

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


Components of the ecg complex10

Components of the ECG Complex

  • T Wave

    • repolarization of ventricles

    • concurrent with end of ventricular systole


Ecg analysis

ECG Analysis


Ecg analysis1

ECG Analysis

  • Rate

  • Rhythm/Regularity

  • QRS Complex

  • P Waves

  • Relationships & Measurements


Ecg analysis2

ECG Analysis

  • Ventricular Rate

    • Triplicate method

      • 300-150-100-75-60-50

    • 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!!!


Ecg analysis3

ECG Analysis

  • Rhythm

    • Measure R-R intervals across strip

    • Should find regular distance between R waves

    • Classification

      • Regular

      • Irregular

        • Regularly irregular

        • Irregularly irregular


Ecg analysis4

ECG Analysis

  • QRS Complex

    • Narrow

      • < 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


Ecg analysis5

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


Ecg analysis6

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?


Ecg analysis7

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


Ecg analysis8

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!!!


Ecg analysis9

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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