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Resting ECG An overview. Electrocardiogram (ECG) n Graphic recording of the electrical activity (impulses) generated by the heart n Placement of electrodes.

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Presentation on theme: "Resting ECG An overview. Electrocardiogram (ECG) n Graphic recording of the electrical activity (impulses) generated by the heart n Placement of electrodes."— Presentation transcript:

1 Resting ECG An overview

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

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

4 ECG n 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 n Lead - two or more electrodes placed on the body in designated anatomical locations n 1. Standard Limb Leads (3) n 2. Augmented Limb Leads (3) n 3. Chest Leads (6) n Use 10 electrodes

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

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

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

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

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

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

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

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

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

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

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

17 ECG Waverforms n P - atrial depolarization n 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 n QRS - ventricular depolarization –first deflection down is Q –first deflection up is R –first downward deflection following an upward deflection is S

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

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

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

22 PHASES OF THE RESTING ECG

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

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

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

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

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


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