Electrocardiography for Healthcare Professionals

Transcription

1 Electrocardiography for Healthcare Professionals Kathryn A. Booth Thomas O Brien Chapter 5: Rhythm Strip Interpretation and Sinus Rhythms

2 Learning Outcomes 5.1 Explain the process of evaluating ECG tracings and determining the presence of dysrhythmias. 5.2 Describe the criteria used to classify dysrhythmias, including rhythm, rate, P wave morphology, PR interval measurement, and QRS duration measurement. 5.3 Identify normal sinus rhythm using the criteria for classification, and explain how the rhythm may affect the patient, including basic patient care and treatment. 2

3 Learning Outcomes (Cont.) 5.4 Identify sinus bradycardia using the criteria for classification, and explain how the rhythm may affect the patient, including basic patient care and treatment. 5.5 Identify sinus tachycardia using the criteria for classification, and explain how the rhythm may affect the patient, including basic patient care and treatment. 3

4 Learning Outcomes (Cont.) 5.6 Identify sinus dysrhythmia using the criteria for classification, and explain how the rhythm may affect the patient, including basic patient care and treatment. 5.7 Identify sinus arrest using the criteria for classification, and explain how the rhythm may affect the patient, including basic patient care and treatment. 4

5 5.1 Rhythm Interpretation ECG is an important tool for diagnosing and treating various cardiac diseases. Determining cardiac dysrhythmia can be challenging. ECG analysis involves a systematic approach. 5

6 5.1 Apply Your Knowledge True or False: The best way to analyze an ECG recording is to gather the data and match it to specific rhythm criteria. ANSWER: True 6

7 5.2 Identifying the Components of the Rhythm Key Terms Bradycardia J point Morphology Tachycardia 7

8 5.2 Identifying Components of the Rhythm Five-step process Rhythm (regularity) Rate P wave morphology PR interval QRS duration and morphology Lead II used for rhythm evaluation 8

9 5.2 Identifying the Components of the Rhythm Step One Determining the ECG rhythm or regularity Atrial: Measure P-P wave interval Use calipers. Measure several intervals. Compare to determine whether rhythm is regular or irregular. 9

10 5.2 Identifying the Components of the Rhythm Step One (Cont.) Ventricular: Measure QRS complex intervals: R-R interval is usually easiest. If R wave is not present, use the Q and S wave junction. R-R Interval 10

11 5.2 Identifying the Components of the Rhythm - Step 2 Determining the atrial and ventricular rates Regular rhythm Arial rate: divide number of small boxes between P waves into 1,500 Ventricular rate divide number of small boxes between R waves into 1,500 Irregular rhythm Use the 6-second method 11

12 5.2 Identifying the Components of the Rhythm - Step 3 Identifying the P wave morphology Are shapes and waveforms all the same? Does each P wave have a QRS complex following it? 12

13 5.2 Identifying the Components of the Rhythm - Step 4 Measuring the PR interval Measure the distance from the start of the P wave to the start of the QRS complex, Normal range is 0.12 to 0.20 second, Calculate in multiples of 0.02 because the human eye cannot determine 0.01 second, 13

14 5.2 Identifying the Components of the Rhythm - Step 4 (cont.) 14

15 5.2 Identifying the Components of the Rhythm - Step 5 Measuring the QRS duration and analyzing the morphology Helps in discriminating between different dysrhythmias Normal limits second Measure from beginning of QRS complex to J point 15

16 5.2 Identifying the Components of the Rhythm - Step 5 (cont.) J Point QRS Duration 16

17 5.2 Identifying the Components of the Rhythm - Step 5 Important QRS questions Are all QRS complexes of equal duration? What is the actual measurement, and is it within normal limits? Do all QRS complexes look alike? Are unusual QRS complexes associated with ectopic beat? 17

18 5.2 Apply Your Knowledge What are the five steps in rhythm data gathering? ANSWER: Rhythm Rate P wave configuration PR interval QRS duration and morphology 18

19 5.2 Apply Your Knowledge What is the normal range for the PR interval? ANSWER: second 19

20 5.3 Rhythms Originating from the Sinus Node Key Terms Cardiac output Stroke volume 20

21 5.3 Rhythms originating from the Sinus Node Normal sinus rhythm Sinus bradycardia Sinus tachycardia Sinus dysrhythmia Sinus arrest 21

22 5.3 Normal Sinus Rhythm Criteria Originates at the SA node Rhythm: Intervals between two P and two R waves occur in a consistent pattern. 22

23 5.3 Normal Sinus Rhythm Criteria Rate: bpm (atrial and ventricular) P wave morphology Uniform shape Upright deflection P wave appears prior to every QRS complex. 23

24 5.3 Normal Sinus Rhythm Criteria (cont.) PR interval second Same appearance, without variations QRS duration and morphology second Morphology consistent, without variations 24

25 5.3 Normal Sinus Rhythm: What You Should Know This is the normal, desired rhythm. Rhythm is typical of patient with normal cardiac output. If patient has returned to sinus rhythm from another dysrhythmia: Check for low cardiac output If patient is pale or breathing rapidly, cardiac output may be low If symptoms of low cardiac output are present, inform a licensed practitioner. 25

26 5.3 Apply Your Knowledge What does normal cardiac output mean? ANSWER: The heart is beating adequately, pumping blood to the body s vital organs to maintain normal function. 26

27 5.4 Sinus Bradycardia Originates from the SA node Atrial and ventricular rates are the same and are less than 60 beats per minute. 27

28 5.4 Sinus Bradycardia Criteria Criteria for rhythm, P wave morphology, PR interval, and QRS duration and morphology are the same as for normal sinus rhythm. 28

29 5.4 Sinus Bradycardia: What You Should Know Patient may or may not exhibit signs of low cardiac output. If symptoms of low cardiac output are present, inform a licensed practitioner. Rhythm may require medication or pacemaker. 29

30 5.4 Apply Your Knowledge What characteristic differentiates sinus bradycardia from normal sinus rhythm? ANSWER: The heart rate is less than 60 bpm. (Only). All other criteria are within normal range. 30

31 5.4 Apply Your Knowledge What treatment may be required in a patient who has sinus bradycardia? ANSWER: Medication or pacemaker 31

32 5.5 Sinus Tachycardia Key Term Palpitations 32

33 5.5 Sinus Tachycardia Originates from the SA node. Atrial and ventricular rates are the same and are between 100 and 150 beats per minute. 33

34 5.5 Sinus Tachycardia Criteria Criteria for rhythm, P wave morphology, PR interval, and QRS duration and morphology are the same as in sinus rhythm and sinus bradycardia. 34

35 5.5 Sinus Tachycardia: How Patient Is Affected Increased heart rate could be normal response to recent exercise. Sinus tachycardia can cause low cardiac output. Patient may complain of heart fluttering or palpitations. 35

36 5.5 Sinus Tachycardia: What You Should Know Sinus tachycardia may be life-threatening in patients with recent myocardial infarctions. If symptoms of low cardiac output are present, inform a licensed practitioner immediately. Medication may be necessary. 36

37 5.5 Apply Your Knowledge What characteristic differentiates sinus tachycardia from other sinus rhythms? ANSWER: The heart rate is between 100 and 150 bpm. 37

38 5.6 Sinus Dysrhythmia Key Term Vagal tone 38

39 5.6 Sinus Dysrhythmia Originates from the SA node Irregular rhythm is caused by pressure on the heart from respiratory cycle and variations of vagal tone. Overall rate is beats per minute. 39

40 5.6 Sinus Dysrhythmia: Criteria Criteria for P wave morphology, PR interval, and QRS duration and morphology are the same as in sinus rhythm. 40

41 5.6 Sinus Dysrhythmia: What You Should Know Patient usually shows no visible signs. Severe rhythm irregularity may cause dizziness or palpitations due to slow rate. Place copy of rhythm strip in patient s record for documentation. 41

42 5.6 Apply Your Knowledge What characteristic distinguishes sinus dysrhythmia from other sinus rhythms? ANSWER: The rate is irregular; the P-P and R-R intervals widen progressively, then narrow, following vagal tone and the patient s breathing pattern. 42

43 5.7 Sinus Arrest Key Terms Hypotension Ischemia Syncope 43

44 5.7 Sinus Arrest SA node stops firing, causing a pause in electrical activity. During the pause, atrial and ventricular contractions do not occur. 44

45 5.7 Sinus Arrest: Criteria Rhythm: Regular before and after sinus arrest period, but considered irregular because of the pause. Rate: Atrial and ventricular rates are the same, but rate varies depending on electrical activity from SA node. Criteria for P wave morphology, PR interval, and QRS duration and morphology are the same as in sinus rhythm. 45

46 5.7 Sinus Arrest: Criteria (Cont.) Length of pause Measure the R-R interval around the pause. Multiply number of small boxes by Note frequency of pauses. Pause of 6 seconds or more is medical emergency. Frequency of pauses 46

47 5.7 Apply Your Knowledge A condition in which the SA node stops firing, causing a pause in electrical activity, is known as: ANSWER: Sinus arrest 47

48 Chapter 5 Summary Evaluating an ECG requires basic knowledge of the components of the rhythm. The process of evaluating an ECG tracing includes determining the rhythm, rate, P wave morphology, PR interval, and QRS duration and morphology. Rhythms that originate from the SA node include normal sinus rhythm, sinus bradycardia, sinus tachycardia, sinus dysrhythmia, and sinus arrest. 48

49 Chapter 5 Summary (Cont d) In normal sinus rhythm, all characteristics are within normal parameters. In sinus bradycardia, all characteristics are within normal parameters except heart rate, which is slower than 60 beats per minute. In sinus tachycardia, all characteristics are within normal parameters except heart rate, which is between 100 and 150 beats per minute. 49

50 Chapter 5 Summary (Cont d) In sinus dysrhythmia, the rate is irregular due to the influence of vagal tone. In sinus arrest, activity in the SA node stops for short periods, causing contractions to stop; except during the pauses, the patient may be in normal sinus rhythm or may have another dysrhythmia. Sinus arrest is considered a medical emergency if the pause lasts for 6 seconds or more. 50