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CHAPTER 14

CHAPTER 14. ECG Interpretation. Systemic Approach to ECG Interpretation. Table 14-1. Step One: General Inspection Step Two: Analysis of Ventricular Activity (QRS complexes) Rate Rhythm Shape Step Three: Analysis of Atrial Activity Rate Rhythm Shape.

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CHAPTER 14

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  1. CHAPTER 14 ECG Interpretation

  2. Systemic Approach to ECG Interpretation Table 14-1. Step One: General Inspection Step Two: Analysis of Ventricular Activity (QRS complexes) • Rate • Rhythm • Shape Step Three: Analysis of Atrial Activity • Rate • Rhythm • Shape

  3. Systemic Approach to ECG Interpretation Table 14-1. Step Four: The Assessment of Atrioventricular Relationship • Conduction ratio • Discharge sequence (P:QRS or QRS:P) • P-R interval Step Five: ECG Interpretation • Normal sinus rhythm • Cardiac dysrhythmias

  4. Step One • Does the general appearance of ECG tracing appear normal or abnormal? • Are there any abnormalities – in terms of appearance or duration – of the P waves, QRS complexes, ST segments, or T waves? • Do the complexes appear consistent from one beat to the next?

  5. Step One • Does the general appearance of ECG tracing appear normal or abnormal? • Does the rate appear too slow or too fast? • Does the rhythm appear regular or irregular? • Are there any extra beats or pauses?

  6. Step Two • Does ventricular activity (QRS Complexes) appear normal or abnormal? • Rate • When regular, the rate can be determined by counting the number of large squares between two consecutive QRS complexes, and then dividing 300 by the number of large squares.

  7. Step Two • Does ventricular activity (QRS Complexes) appear normal or abnormal? • For example, if there are three large squares between two QRS complexes, the ventricular rate would be 100 per minute (300 ÷ 3 = 100)

  8. ECG Recording • Fig. 14-1. ECG recording with markers denoting the number of large squares (blocks) between the QRS complexes (RR interval).

  9. Calculating Heart Rate by Counting Number of Large ECG Squares Fig. 14-1. ECG recording with markers denoting the number of large squares (blocks) between the QRS complexes (RR interval). Distance Between Two QRT Complexes Estimated Heart Rate (Number of Large Squares) (Per min.) 1 300 2 150 3 100 4 75 5 60 6 50

  10. When the Ventricular Heart Rate Is Irregular • This is done by counting the number of QRS complexes in a 6-second interval (two 3-second marks), and then multiplying this number by 10.

  11. When the Ventricular Heart Rate Is Irregular • For example, if seven QRS complexes are present in two 3-second intervals (6 seconds), the ventricular rate is about 70 beats per minute (7 x 10 = 70).

  12. Rhythm • Ventricular rhythm is determined by comparing shortest R-R intervals with the longest R-R.

  13. Rhythm • When the time variation between the shortest R-R interval and the longest R-R interval is greater than 0.12 second • Rhythm is irregular • Variation of 0.12 or less is a regular rhythm

  14. Shape • Finally, determine if the shape of the QRS complexes is identical from one complex to another. • Are the QRS complexes of the expected polarity, considering the monitoring lead?

  15. Shape • The shape as well as the duration of the QRS complex help to determine the origin of the ventricular depolarization. • Normal QRS duration is 0.10 second • 2 ½ little squares or less

  16. Step Three • Does the atrial activity appear normal or abnormal? • Similar to the assessment of the QRS complexes, the rate, rhythm, and shape of the atrial activity (P-waves) are evaluated. • Rate of the atrial activity is calculated in the same way as the QRS complexes.

  17. Step Three • Does the atrial activity appear normal or abnormal? • Normally, the P-wave rate and the QRS rate are the same.

  18. Step Three • Does the atrial activity appear normal or abnormal? • Atrial rhythm is calculated in the same way as the QRS rhythm • Except that in this case P-P intervals are used. • The shape of the P-waves is then evaluated.

  19. Step Four • Does the atrioventricular (AV) relationship appear to be normal? • Is each P wave followed by a QRS complex? • Is each QRS complex preceded by a single P wave?

  20. STEP 5:WHAT IS THE ECG INTERPRETATION?

  21. Normal Sinus Rhythm P Wave: P waves are positive (upright) and uniform. A QRS complex follows every P wave. PR Interval: The duration of the PR interval is between 0.12 and 0.20 second and is constant from beat to beat.

  22. Normal Sinus Rhythm QRS Complex: The duration of the QRS complex is 0.10 second or less. A P wave precedes every QRS complex. QRS Rate: Between 60 and 100 beats per minute. QRS Rhythm: Regular

  23. ECG Tracing of a Normal Sinus Rhythm • Fig. 14-2. As ECG tracing of a normal sinus rhythm.

  24. Common Cardiac Dysrhythmias Table 14-3 Sinus Atrial Ventricular AV Conduction Mechanisms Mechanisms Mechanisms Defects Sinus Bradycardia Premature atrial Premature ventricular Sinus rhythm with first- Sinus Tachycardia contraction (PAC) Complex (PVC) degree AV block Sinus Arrhythmia Atrial bigeminy Uniform PVCs Sinus rhythm with Sinus Block Atrial tachycardia Multiform PVCs second-degree AV block Sinus Arrest Atrial flutter Paired PVCs Sinus rhythm with Atrial fibrillation Bigeminal PVCs complete AV block Trigeminal PVCs Ventricular tachycardia Ventricular flutter Ventricular fibrillation Asystole

  25. SINUS MECHANISMS

  26. Sinus Bradycardia P Wave: P waves are positive and uniform. Each P wave is followed by a QRS complex. PR Interval: PR interval has a normal duration between 0.12 and 0.20 second and is constant from beat to beat. QRS Complex: QRS complex duration is 0.10 second or less. P wave precedes every QRS complex. QRS Rate: Less than 60 beats per minute. QRS Rhythm: Regular

  27. ECG Tracing • Fig. 14-3. An ECG tracing showing the (+) P wave to the left of each QRS complex; the PR intervals are consistent and the heart rate is less than 60 bpm. This represents a sinus bradycardia.

  28. ECG Tracing Showing Sinus Bradycardia • Fig. 14-4. An ECG tracing showing sinus bradycardia in two leads from a physically fit adult.

  29. Sinus Tachycardia P Wave: P waves are positive and uniform. Each P wave is followed by a QRS complex. PR Interval: PR interval has a normal duration between 0.12 and 0.20 second and is constant from beat to beat. QRS Complex: QRS complex duration is 0.10 second or less. A P wave precedes every QRS complex. QRS Rate: Between 100 and 160 beats per minute. QRS Rhythm: Regular

  30. ECG Tracing from an Exercising Adult • Fig. 14-5. An ECG tracing from an exercising adult. Note there is a single (+) P wave to the left of each QRS complex; the rate is 150 bpm.

  31. Sinus Arrhythmia P Wave: P waves are positive and uniform. Each P wave is followed by a QRS complex. PR Interval: PR interval has a normal duration between 0.12 and 0.20 second and is constant from beat to beat. QRS Complex: QRS complex duration is 0.10 second or less. A P wave precedes every QRS complex. QRS Rate: Varies by more than 10 percent. It is helpful to report the rate range. QRS Rhythm: Irregular

  32. ECG Tracing of Sinus Arrhythmia 54 to 71 bpm • Fig. 14-6. An ECG tracing of sinus arrhythmia 54 to 71 bpm.

  33. Sinus (SA) Block P Wave: P waves are positive and uniform. However, there is an entire P-QRS-T complex missing. PR Interval: PR interval has a normal duration between 0.12 and 0.20 second and is constant from beat to beat, except for the pause when an entire cycle is missing. The PR interval may be slightly shorter after the pause.

  34. Sinus (SA) Block QRS Complex: Except for the missing cycle, the QRS complex duration is 0.10 second or less, and a P wave precedes every QRS complex. QRS Rate: Rate may vary according to the number and position of missing P-QRS-T cycles. QRS Rhythm: Rhythm may be regular or irregular according to the number and position of missing P-QRS-T cycles.

  35. ECG Tracing Showing SA Block • Fig. 14-7. An ECG tracing showing SA block.

  36. Sinus Arrest P Wave: No P wave. PR Interval: PR interval has a normal duration between 0.12 and 0.20 second and is constant from beat to beat. QRS Complex: QRS complex duration is 0.10 second or less. After a sinus arrest, however, the QRS duration may be greater than 0.10 second when the escape rhythm is initiated by the AV node.

  37. Sinus Arrest QRS Rate: Normal sinus rhythm during non-sinus arrest periods. QRS Rhythm: QRS complexes before and after the sinus arrest are regular. The escape rate may be regular or irregular.

  38. ECG Tracing: 82-year-old Patient Showing Sinus Arrest • Fig. 14-8. An ECG tracing from an 82-year-old patient showing sinus arrest. The patient required insertion of an electronic pacemaker.

  39. THE ATRIAL MECHANISMS

  40. Premature Atrial Complex P Wave: P wave will appear different than a normal SA node induced P wave. When the PAC is early, the P may be hidden, or partially hidden, in the preceding T wave. P waves hidden in the T wave often distort, or increase the amplitude of the T wave. A PAC may not successfully into the ventricles if the AV node or bundle branches are in their complete refractory period. This is called a blocked or nonconducted PAC.

  41. Premature Atrial Complex PR Interval: PR interval may be normal or prolonged, depending on the timing of the PAC. Most often, however, the PR interval is different from the normal SA node rhythm. QRS Complex: Except for the cycle that is missing, the QRS complex duration is 0.10 second or less, and a P wave precedes every QRS complex. QRS Rate: Varies QRS Rhythm: Irregular

  42. ECG Tracing Showing a P Superimposed on T waves • Fig. 14-9. An ECG tracing showing a P superimposed on T waves (red arrows). The ECG interpretation would be sinus rhythm at 96 bpm with frequent PACs.

  43. Sinus Rhythm 75 bpm with Frequent, Nonconducted PACs • Fig. 14-10. The ECG interpretation would be sinus rhythm at 75 bpm with frequent, nonconducted PACs.

  44. Atrial Bigeminy • Present when every other beat is an ectopic atrial beat—a PAC • In other words: • ECG tracing shows a PAC, a normal sinus beat, a PAC, a normal sinus beat, and so on.

  45. Sinus Rhythm at 86 bpm with Atrial Bigeminy • Fig. 14-11. The ECG interpretation would be sinus rhythm at 86 bpm with atrial bigeminy.

  46. Atrial Tachycardia P Wave: Starts abruptly, at rates of 130 to 250 beats per minute. The P wave may or may not be seen. Visible P waves differ in configuration from the normal sinus P wave. At more rapid rates, the P is hidden in the preceding T wave and cannot be seen as a separate entity.

  47. Atrial Tachycardia PR Interval: PR interval has a normal duration between 0.12 and 0.20 second and is constant from beat to beat. The PR interval is difficult to measure at rapid rates.

  48. Atrial Tachycardia QRS Complex: The QRS complex duration is 0.10 second or less. A P wave usually precedes every QRS complex, although a 2:1 AV conduction ratio is often seen. The QRS complexes during atrial tachycardia may be normal or abnormal, depending on the degree of ventricular refractoriness and AV conduction time.

  49. Atrial Tachycardia QRS Rate: Very regular QRS Rhythm: Atrial tachycardia begins suddenly and is very regular.

  50. Onset of Atrial Tachycardia in Red Arrow • Fig. 14-12. An example of the onset of atrial tachycardia (red arrow).

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