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Cardiovascular Monitoring Electrocardiogram

Cardiovascular Monitoring Electrocardiogram. Dr. noha elsayed. Electrocardiography. Electrical activity is recorded by electrocardiogram (ECG) P wave corresponds to depolarization of SA node QRS complex corresponds to ventricular depolarization

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Cardiovascular Monitoring Electrocardiogram

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  1. Cardiovascular MonitoringElectrocardiogram Dr.nohaelsayed

  2. Electrocardiography • Electrical activity is recorded by electrocardiogram (ECG) • P wave corresponds to depolarization of SA node • QRS complex corresponds to ventricular depolarization • T wave corresponds to ventricular repolarization • Atrialrepolarization record is masked by the larger QRS complex Cardiovascular System: Intrinsic Conduction System , Cardiovascular System

  3. Electrocardiography Figure 18.16 Chapter 18, Cardiovascular System

  4. Isoelectric line No electrical activitybaseline

  5. EKG Records 1. Amount of voltage generated by ht – vertical scale 2. Time required for voltage to travel thru ht – horizontal scale

  6. ECG Interpretation What is your approach to reading an ECG? Rate Rhythm Axis P wave PR interval QRS complex QT interval ST segment – T wave

  7. EKG Interpretation: 8criteria • 1. What is the rate? • Quick estimate: • Count # R waves in a 6 second strip x 10 • 6 second strip = 3 “tic” marks Square Counting: 300-150-100-75-60-50-42A

  8. Role of 300 Take the number of “big boxes”between neighboring QRS complexes, and divide this into 300. The result will be approximately equal to the rate Although fast, this method only works for regular rhythms.

  9. 10Second Rule As most EKGs record 10 seconds of rhythm per page, one can simply count the number of beats present on the EKG and multiply by 6 to get the number of beats per 60 seconds. This method works well for irregular rhythms.

  10. Rythm • 2. Is rhythm regular or irregular? • Measure distance between RR interval • Measure throughout full 6 second strip

  11. Axis 3.Left or right axis deviation? Look at limb leads I and aVF. Normal: I +, aVF + LAD: I +, aVF – RAD: I -, aVF +

  12. Axis Deviation

  13. QRS-axis

  14. 4-P Wave • First component of a normal ECG • Represents the spread of electrical activity over the atrium, atrial depolarization. The normal depolarization begins at the sinoatrial (SA) node near the top of the atrium. Because of the top-to-bottom, right-to-left path, the P wave is normally largest in Lead II • Configuration: usually rounded and upright in all leads except R • Amplitude is usually 2-3 mv in any lead

  15. Are P waves present? • Should be 1:1

  16. Abnormal rhythms with P waves

  17. 5. What is the PR Interval? PRI

  18. PR Interval • Measured from the beginning of the P wave (atrial depolarization) to the beginning of the QRS complex (ventricular depolarization) • Represents the time it takes for an impulse to travel from the SA node through the atria and the AV node • Normally between 0.12 to 0.20 seconds in duration • If prolonged, > 0.20 seconds • indicates conduction delay through the AV node • and is called a 1st degree AV block

  19. 6. What is the width of QRS complex? Normal QRS duration is 0.06 to 0.12 seconds

  20. QRS Complex • Represents activation of the ventricles, ventricular depolarization • Special conducting bundles spread the wave of depolarization rapidly over the bundles • May have one, two or all three components : Q R S • Q wave is the first negative wave after the P wave and before the R wave. The Q wave represents activation of the ventricular septum • R wave is the first positive wave after the P wave. • Most of the ventricle is depolarized during the R wave. • S wave is the negative wave after the R wave. • Lengthening of the QRS indicates some blockage of the electrical conduction system either due to ischemia, necrosis of the conducting tissue, electrolyte imbalance or hypothermia

  21. Sinus Rhythm Impulse originates in SA node (normal pacemaker site) • Normal Sinus Rhythm - NSR • Regularity – regular • Rate - 60 – 100 / minute • P waves = 1:1 • PRI = .12 - .20 • QRS = .12 or <

  22. 7-Q-T Interval • QT interval represents total ventricular activity. It is the summation of ventricular depolarization to repolarization • Can vary with heart rate • Measured from the beginning of the Q wave to the end of the T wave • Corrected QT interval (QTc) takes heart rate into account and provides various normal values based on the rates • Rule of thumb – QT interval should be less than half the preceeding R-R interval • The U wave represents repolarization of the Purkinje fibers but isn’t always seen on paper. A prominent U wave may be caused by hypercalcemia or hypokalemia

  23. 8.ST segment & T wave

  24. Normal Values • PR interval: 0.12-0.21 s • QRS complex: 0.06-0.1 s • QT interval: < 0.44 s - HR dependent, cave: long QT syndrome! • ST segment changes: - significant if > 1mm in limb leads, > 2mm in precordialleads • Q waves: • significant if > 1/3 of total QRS complex

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