The Electrocardiogram: Basic Concepts and Lead Monitoring Chapter 2 Robert J. Huszar, MD Instructor Patricia L. Thomas, MBA, RCIS

Electrical Basis of the Electrocardiogram Graphic record of magnitude and direction of electrical activities or current Graphic record of magnitude and direction of electrical activities or current Generated by Depolarization and Repolarization Generated by Depolarization and Repolarization

Components of the Electrocardiogram P-wave P-wave QRS wave QRS wave T wave T wave Segments Segments –PR –ST –TP Intervals Intervals –PR –QT –R-R J Point J Point

EKG PAPER Vertical Lines Vertical Lines –Dark lines are.20 second (5 mm) apart –Light lines are.04 second (1 mm) apart Horizontal Lines Horizontal Lines –Dark Lines are 5 mm apart –Light Lines are 1mm apart Large Square 5 x 5 mm Large Square 5 x 5 mm One Small Square 1x1 mm One Small Square 1x1 mm

Artifacts Tense or Nervous patients Tense or Nervous patients Shivering from cold Shivering from cold –Gives EKG finely or coarsely jagged appearance Poor electrical contact with skin Poor electrical contact with skin Dried electrode paste or jelly Dried electrode paste or jelly

Artifacts Improperly grounded Improperly grounded AC-operated ECG Machine AC-operated ECG Machine Obtained near high tension wires, transformers or electric appliances Obtained near high tension wires, transformers or electric appliances

Artifacts Signals are poorly received over a biotelemetry system Signals are poorly received over a biotelemetry system When transmitter’s power is low because or week batteries When transmitter’s power is low because or week batteries

Artifacts During CPR During CPR Causes regularly spaced, wide, upright waves synchronous with the downward compressions of the chest Causes regularly spaced, wide, upright waves synchronous with the downward compressions of the chest

12 Lead ECG Six Limb or Extremity Leads Six Limb or Extremity Leads –Three standards (bipolar) limb leads –Leads I, II & III Three Augmented (unipolar) Leads Three Augmented (unipolar) Leads –Leads aVR, aVL, & aVF Six Precordial (unipolar) Six Precordial (unipolar) –Leads V1, V2, V3, V4, V5 & V6

12 Lead ECG Lead I Lead I –Left arm (+) –Right arm (-) Lead II Lead II –Right arm (-) –Left leg (+) Lead III Lead III –Left arm (-) –Left leg (+)

12 Lead ECG Central Terminal Central Terminal –Formed by connecting the extremity electrodes together which is negative aVR aVR –Right arm (+) aVL aVL –Left arm (+) aVF aVF –Left leg (+)

12 Lead ECG V1 V1 –Right of sternum in the fourth intercostal space V2 V2 –Left of sternum in the fourth intercostal space V3 V3 –Midway between V2 & V4 V4 V4 –Midclavicular line in the fifth intercostal space V5 V5 –Anterior axillary line at the same level V6 V6 –Midaxillary line at the same level V5

THE END OF CHAPTER 2 Hauszar Robert, Basic Dysrhythmias, Interpretation & Management, Third Edition, Mosby, Inc. 2002, pp Bledsoe.Porter.Cherry.”Paramedic Care: Principles & Practice, Prentice-Hall, Inc. Volume Pp