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- 1. The electrocardiogram<br />ECG or EKG<br />The ECG is a measurement of the sum total of electrical activity generated by the heart measured from the surface of the body<br />An electrical record of the heart’s activity<br />It is one of the most valuable diagnostic tools for the recognition of a large variety of cardiac disorders <br />
- 2. Characteristics of the normal electrocardiogram<br />The normal electrocardiogram is composed of:<br />P wave: is caused by electrical potentials generated when the atria depolarizebefore atrial contraction begins<br />QRS complex: is caused by potentials generated when the ventricles depolarizebefore contraction<br /> The P wave and the components of the QRS complex aredepolarization waves<br />
- 3. T wave: is caused by potentials generated as the ventricles recover from the state of depolarization. the T wave is known as a repolarizationwave<br />The electrocardiogram is composed of both depolarization and repolarization waves. <br />
- 4. The atrial repolarization wave, known as the atrial T wave, is usually obscured by the much larger QRS complex. For this reason, an atrial T wave seldom is observed in the electrocardiogram<br />
- 5. The “PQRST”<br />P wave - Atrial depolarization<br /><ul><li>QRS - Ventricular depolarization
- 6. T wave - Ventricular repolarization</li></li></ul><li>Depolarization Waves Versus Repolarization Waves<br />In figure (A) depolarization, The first half of the fiber has already depolarized, while the remaining half is still polarized<br />The left electrode on the outside of the fiber is in an area of negativity, and the right electrode is in an area of positivity, this causes the meter to record positive<br />When depolarization has reached half way mark the record risen to maximum positive value<br />
- 7. Depolarization Waves Versus Repolarization Waves<br />In figure (B) depolarization has extended over the entire muscle fiber, and the recording to the right has returned to the zero baseline because both electrodes are now in areas of equal negativity. The completed wave is a depolarization wave because it results from spread of depolarization along the muscle fiber membrane<br />
- 8. Depolarization Waves Versus Repolarization Waves<br />In figure (C) shows halfway repolarization of the same muscle fiber, with positivity returning to the outside of the fiber. At this point, the left electrode is in an area of positivity, and the right electrode is in an area of negativity<br />Consequently, the recording, as shown to the right, becomes negative<br />
- 9. Depolarization Waves Versus Repolarization Waves<br />In figure (D) the muscle fiber has completely repolarized, and both electrodes are now in areas of positivity, so that no potential difference is recorded between them <br />This completed negative wave is a repolarization wave because it results from spread of repolarization along the muscle fiber membrane<br />
- 10. Relation of ventricle action potential to the QRS and T waves in the electrocardiogram<br />No potential is recorded in the electrocardiogram when the ventricular muscle is either completely polarized or completely depolarized<br />Only when the muscle is partly polarized and partly depolarized does current flow from one part of the ventricles to another part, and therefore current also flows to the surface of the body to produce the electrocardiogram<br />
- 11. The time of the onset of the P wave to the onset of the QRS complex is termed as PR interval. It represent the conduction time from the atrial to the ventricle<br />The time from the beginning of the Q wave to the end of the S wave is called the QRS interval. It indicates the time taken by the impulse to separate to the two ventricles<br />
- 12. The time from the beginning of the Q wave to the end of T wave is called the QT interval. It represent the total electrical activity of ventricles<br />The line between the QRS complex and T wave is called ST segment. It represent the time between completion of depolarization and onset of repolarization<br />
- 13. The time interval from the apex of one R wave to the next R wave is called R-R interval<br />R-R interval is related to the heart rate or rate of ventricular contraction <br />The time interval from the beginning of one P wave to the beginning of the next P wave is called P-P interval <br />
- 14. Vertical Axis = Voltage<br />Vertical axis represents voltage on the EKG<br />One small box (1 mm) represents 0.10 mV<br />
- 15. Horizontal Axis = Time<br />1 small (1 mm) box = 0.04 seconds (40 ms)<br />1 large (5 mm) box = 0.20 seconds (200 ms)<br />5 large(5 mm) boxes = 1 second (1000 ms)<br />15 large(5 mm) boxes = 3 seconds and is marked on EKG paper<br />
- 16. The ECG Paper<br />Horizontally<br />One small box - 0.04 s<br />One large box - 0.20 s <br />Vertically<br />One large box - 0.5 mV<br />
- 17. The ECG Paper <br />Every 3 seconds (15 large boxes) is marked by a vertical line.<br />This helps when calculating the heart rate.<br />NOTE: the following strips are not marked but all are 6 seconds long.<br />3 sec<br />3 sec<br />
- 18. Rhythm Analysis<br />Step 1: Calculate rate.<br />Step 2: Determine regularity.<br />Step 3: Assess the P waves.<br />Step 4: Determine PR interval.<br />Step 5: Determine QRS duration.<br />
- 19. Step 1: Calculate Rate<br />Option 1<br />Count the # of R waves in a 6 second rhythm strip, then multiply by 10.<br />Interpretation?<br />3 sec<br />3 sec<br />9 x 10 = 90 bpm<br />
- 20. Step 1: Calculate Rate<br />Option 2 <br />Find a R wave that lands on a bold line.<br />Count the # of large boxes to the next R wave. If the second R wave is 1 large box away the rate is 300, 2 boxes - 150, 3 boxes - 100, 4 boxes - 75, etc. (cont)<br />R wave<br />
- 21. Step 1: Calculate Rate<br />Option 2 <br />Interpretation?<br />300<br />150<br />100<br />75<br />60<br />50<br />Approx. 1 box less than 100 = 95 bpm <br />
- 22.
- 23. What is the heart rate?<br />
- 24. Step 2 : Determine Regularity<br />Regular: If the difference between the longest R-R interval in the ECG and the shortest R-R interval is less than 0.12 second<br />Irregular: If the difference between the longest R-R interval in the ECG and the shortest R-R interval is greater than 0.12 second<br />
- 25. Step 2: Determine regularity<br />Look at the R-R distances (using a caliper or markings on a pen or paper).<br />Interpretation?<br />R<br />R<br />Regular<br />
- 26. Step 3: Assess the P waves<br />Are there P waves?<br />Do the P waves all look alike?<br />Do the P waves occur at a regular rate?<br />Is there one P wave before each QRS?<br />Interpretation?<br />Normal P waves with 1 P wave for every QRS<br />
- 27. Step 4: Determine PR interval<br />Normal: 0.12 - 0.20 seconds.<br /> (3 - 5 boxes)<br />Interpretation?<br />0.12 seconds<br />
- 28. Step 5: QRS duration<br />Normal: 0.04 - 0.12 seconds.<br /> (1 - 3 boxes)<br />Interpretation?<br />0.08 seconds<br />
- 29. Rhythm Summary<br />Rate 90-95 bpm <br />Regularity regular<br />P waves normal<br />PR interval 0.12 s<br />QRS duration 0.08 s<br />Interpretation?<br />Normal Sinus Rhythm<br />

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