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ECG Basics

ECG Basics. Dr. Taj. Outline. Review of the conduction system ECG waveforms and intervals ECG leads Determining heart rate Determining QRS axis. The Normal Conduction System. What is an ECG?. The electrocardiogram (ECG) is a representation of the electrical events of the cardiac cycle.

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ECG Basics

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  1. ECG Basics Dr. Taj

  2. Outline • Review of the conduction system • ECG waveforms and intervals • ECG leads • Determining heart rate • Determining QRS axis

  3. The Normal Conduction System

  4. What is an ECG? The electrocardiogram (ECG) is a representation of the electrical events of the cardiac cycle. Each event has a distinctive waveform, the study of which can lead to greater insight into a patient’s cardiac pathophysiology.

  5. What types of pathology can we identify and study from ECGs? • Heart rate • Heart Rhythem • Myopathies • Electrolyte disturbances (i.e. hyperkalemia, hypokalemia) • Drug toxicity (i.e. digoxin and drugs which prolong the QT interval)

  6. Waveforms and Intervals

  7. ECG Leads Leads are electrodes which measure the difference in electrical potential between either: 1. Two different points on the body (bipolar leads) 2. One point on the body and a virtual reference point with zero electrical potential, located in the center of the heart (unipolar leads)

  8. ECG Leads The standard ECG has 12 leads: 3 Standard Limb Leads 3 Augmented Limb Leads 6 Precordial Leads The axis of a particular lead represents the viewpoint from which it looks at the heart.

  9. Standard Limb Leads

  10. Precordial Leads Adapted from: www.numed.co.uk/electrodepl.html

  11. Summary of Leads

  12. Graph paper calibration

  13. Determining the Heart Rate Take the number of “smallest boxes moved by the machine per minute” i.e. (1500) , and divide by the number of boxes between adjacent “R”-”R” waves.

  14. Rule of 1500 Take the number of “smallest boxes moved by the machine per minute” i.e. (1500) , and divide by the number of boxes between adjacent “R”-”R” waves.

  15. What is the heart rate? www.uptodate.com (1500 / 30) = 50 bpm

  16. What is the heart rate? www.uptodate.com (1500 / ~18) = ~ 83 bpm

  17. What is the heart rate? (1500 / 8) = 187 bpm

  18. The Rule of 300 It may be easiest to memorize the following table:

  19. Practice Heart Rate & Axis

  20. Practice Heart Rate & Axis

  21. Rhythm The rhythm of the heart can be regular or irregular.

  22. THE END

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