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Resting ECG

Resting ECG. An overview. Electrocardiogram (ECG). Graphic recording of the electrical activity (impulses) generated by the heart Placement of electrodes on the body will allow for detection of these impulses. ECG.

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Resting ECG

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  1. Resting ECG An overview

  2. Electrocardiogram (ECG) • Graphic recording of the electrical activity (impulses) generated by the heart • Placement of electrodes on the body will allow for detection of these impulses

  3. ECG • Generally standard procedure to monitor and record the ECG during a graded exercise test (GXT)

  4. ECG • Equipment • adhesive silver-silver chloride electrodes with electrolyte gel or paste • electrical wires • amplifier • monitor • recording apparatus • computer to program the treadmill

  5. Twelve views of the heart • Lead - two or more electrodes placed on the body in designated anatomical locations • 1. Standard Limb Leads (3) • 2. Augmented Limb Leads (3) • 3. Chest Leads (6) • Use 10 electrodes

  6. Anatomical Locations of Leads • Right Arm (RA) - right shoulder below the clavicle but above the border of pectoralis • Left Arm (LA) - left shoulder below the clavicle but above the border of pectoralis (in deltoid fossa)

  7. Anatomical Locations • Right Leg (RL) - halfway between the costal margin (ribs) and the iliac crest (hip bone) • Left Leg (LL) - halfway between the costal margin and the iliac crest

  8. Anatomical Locations • V1 – right of sternum • V2 – left of sternum • V3 - midway between positions for V2 and V4 • V4 - left midclavicular line

  9. Anatomical Locations • V5 - Horizontal level of V4 at left anterior axillary line • V6 – horizontal level of V4 at left midaxillary line

  10. Standard Limb Leads • Lead 1 - *Left Arm (LA) - Right Arm (RA) angle 0 • Lead 2 - *Left Leg (LL) - Right Arm (RA) angle 60 • Lead 3 - *Left Leg (LL) - Left Arm (LA) angle 120 • * indicates positive electrode

  11. Augmented Limb Leads • Augmented – need to amplify the voltage to get a tracing of the same magnitude as Leads 1,2,3

  12. Augmented • aVR - Augmented Voltage Right Arm • *RA and (LA-LL) angle -150 • aVL - Augmented Voltage Left Arm • *LA and (RA-LL) angle -30 • aVF - Augmented Voltage Left Foot • *LL and (RA-LA) angle +90

  13. Leads • II, III, and AVF - inferior lead • view of inferior surface of heart • I and AVL - left lateral leads • view of left lateral wall of heart • AVR - loner

  14. Structures of the Heart • SA Node • Atria • AV Node • Common Bundle • Right and Left Bundle Branches • Purkinje fibers • Ventricles

  15. Electrical Events • 1. Sinus Node in the atrium • 2. Depolarization left, inferior, and anterior through right atrium • 3. Spreads through left atrium • 4. AV node and Bundle of His • 5. Left and Right Bundle Branches

  16. Electrical Events • 6. Impulse crosses the intraventricular septum from left to right • 7. Depolarization of ventricles simultaneously

  17. ECG Waverforms • P - atrial depolarization • PR interval - an interval encompasses at least one wave plus the connecting line • time from start of P wave to beginning of QRS • time for depolarization of the atria to beginning of ventricular depolarization

  18. Waves • QRS - ventricular depolarization • first deflection down is Q • first deflection up is R • first downward deflection following an upward deflection is S

  19. Waves • ST segment - a straight line connecting two waves • ventricular isoelectric period • time from end of ventricular depolarization to the start of ventricular repolarization • T wave - ventricular repolarization

  20. Depolarization • Positive deflection - a wave of depolarization moving toward a positive electrode • Negative deflection - a wave of depolarization moving away from a positive electrode • biphasic - wave moving perpendicularly to the positive electrode (positive deflection precedes negative)

  21. Repolarization • Positive deflection - a wave of repolarization moving away from a positive electrode • Negative deflection - a wave of repolarization moving toward a positive electrode • biphasic - wave moving perpendicularly to the positive electrode (negative deflection precedes positive)

  22. PHASES OF THE RESTING ECG

  23. Leads and the P wave • Atrial Depol wave moving toward leads I, AVL, II, and AVF  positive deflection • Lead III biphasic • Lead AVR  negative deflection

  24. Normal ECG Responses to Exercise • Minor and significant changes in P-wave • Superimposition of the P and T waves of successive beats • Increases in Q wave amplitude • Slight decreases in R wave amplitude • Increases in T wave amplitude

  25. Normal Responses • Minimal shortening of the QRS duration • Depression of the J point • Rate-related shortening of the QT interval

  26. Time and Voltage • Duration - seconds • Amplitude - millivolts • Configuration - shape and appearance

  27. EKG Paper • Light Lines (small squares)- 1mm x 1mm • Dark Lines (large squares) - 5mm x 5mm • Small square - .04 s and/or .1 mV • Large Square - .2 s and/or .5 mV

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