Understanding rhythm strips

1. Understanding Rhythm Strips

2. Waveforms and Components of The ECG Pattern A waveform A positive or a negative defection that begins and ends at the baseline It is an electrical representation of depolarization and repolarization occurring in the heart When there is NO electrical activity is detected, a straight line (isoelectric or base line) is recorded The waveforms produced by the heart’s electrical conduction system are called P QRS T May or may not be a U Wave

3. ECG Waveforms P wave Occurs when the right and left atria are stimulated QRS complex Occurs when the right and left ventricles are stimulated T wave Represents electrical recovery or return to a resting state for the ventricles U wave If see, is thought to represent the repolarization of the Purkinje fibers

4. ECG Waveforms P wave Normally an upright and rounded waveform QRS complex Usually the largest of all the waveforms and is spike shaped and narrow in appearance T wave Appears as a slightly asymmetric upright waveform It is usually larger than the P wave and smaller than the QRS

5. ECG Waveform

6. EGC Waveform

7. ECG Segments Segment Length of baseline between two waves PR segment Represents the delay of the impulse in the AV node ST segment Represents the early part of repolarization of the right and left ventricles

8. ECG Intervals Interval is defined as the combination of a wave or several waves and a segment By measuring time intervals on the ECG, it can be determined how long the electrical wave takes to pass through the heart

9. ECG Intervals PR interval P wave & PR segment Corresponds to the spread of the electrical impulse through the atria and the delay of the impulse in the AV node before it travels to the ventricular muscle tissue QT interval QRS complex & ST segment & T wave Represents electrical stimulation and recovery of the ventricles

10. ECG Segments & Intervals

11. ECG Paper and Measurements ECG paper Graph paper used to measure rates of impulse formation and the duration of the electrical events that occur in the heart Vertical and horizontal lines, which from large and small boxes Vertical lines Measure voltage in millivolts Horizontal lines Measure time in seconds

12. ECG Paper and Measurements By counting the small or large boxes from the beginning to the end of the ECG waveforms and intervals, we can calculate the time it takes for the electricity to travel through certain parts of the heart and the rate at which impulses occur

13. ECG Paper and Measurements Time Equivalents of Small Boxes 1 small box = 0.04 second 2 small boxes = 0.08 second 3 small boxes = 0.12 second 4 small boxes = 0.16 second 5 small boxes = 0.20 second Time Equivalents of Large Boxes 1 large box = 0.20 second 5 large boxes = 1 second 15 large boxes = 3 seconds 30 large boxes = 6 seconds

14. Normal ECG Pattern and Measurements P Wave : Upright, smooth and rounded, and no more than 2.5 mm in height

15. Normal ECG Pattern and Measurements PR Interval : Measure 0.12 to 0.20 second wide or 3 to 5 small boxes

16. Normal ECG Pattern and Measurements QRS : Narrow in appearance, upright in Leads I, II, and III. Measures 0.04 to 0.11 second wide or 1 to 2 ½ small boxes

17. Normal ECG Pattern and Measurements ST Segment : Isoelectric

18. Normal ECG Pattern and Measurements T Wave : Slightly asymmetric, upright, and less than half the height of the QRS complex or 5 mm in height or less

19. Normal ECG Pattern and Measurements QT interval : QT interval is less than half the R-R interval or 0.36 to 0.44 seconds or 9 to 11 small boxes The duration of the QT interval varies according to age, gender, and heart rate As the heart rate increases QT interval decreases As the heart rate decreases QT interval increases

20. Normal ECG Pattern and Measurements QT Interval Fast heart rate Small QT interval Slow heart rate Large QT interval

21. Normal ECG Pattern and Measurements U Wave : Upright and rounded. Usually less than 2 mm in height and smaller than that of the preceding T wave

22. Abnormal Characteristics of the ECG Pattern Abnormal P wave Wide or notched -Left atrial enlargement or ectopic impulse from atria Tall and pointed (peaked) – Right atrial enlargement or ectopic impulse from atria Negative (Inverted) - ectopic pacemaker in the AV junction

23. Abnormal Characteristics of the ECG Pattern Wide or notched Tall and pointed (peaked) Negative (inverted)

24. Abnorma l Characteristics of the ECG Pattern Abnormal PR Interval A PR interval greater than 0.20 second wide is abnormal This may be seen in AV blocks Hypothyroidism Digitalis toxicity

25. Abnormal Characteristics of the ECG Pattern Abnormal QRS complex : A wide QRS (greater than 0.12 second wide) may be seen when an impulse originates from an ectopic site in the ventricular myocardium If there is a delay or block of the impulse in the bundle branches

26. Abnormal Characteristics of the ECG Pattern Abnormal ST segment Elevated ST segment Elevated more than 1 mm in the limb leads or 2 mm in the precordial leads Suggestive of myocardial injury infarction

27. Abnormal Characteristics of the ECG Pattern Abnormal ST segment Scoop ST depression May be caused by digitalis toxicity Depressed ST segment More than 1 mm Suggestive of myocardial ischemia

28. Abnormal Characteristics of the ECG Pattern Abnormal T wave Negative (inverted) Suggest myocardial ischemia or infarction

29. Abnormal Characteristics of the ECG Pattern Abnormal T wave Low, flattened T waves Can be seen with hypokalemia (low potassium)

30. Abnormal Characteristics of the ECG Pattern Abnormal T Wave Tall Tented T waves Suggestive of hyperkalemia (high potassium)

31. Abnormal Characteristics of the ECG Pattern Abnormal QT interval Prolonged (greater than 0.44 seconds) May be congenital or acquired i.e. medications, electrolyte abnormalities

32. Abnorma l Characteristics of the ECG Pattern Abnormal U Wave A U wave taller than 2 mm Electrolyte imbalance Medications Hyperthyroidism Central nervous system disease

33. Steps for Analyzing a Rhythm Strip A quick method for analyzing a rhythm strip There are several steps in analyzing a rhythm strip When analyzing a rhythm strip, don’t forget to check the patient

34. Steps for Analyzing a Rhythm Strip Step 1: Evaluate the P waves Look for the presence of P waves and compare the shape and size of all P waves All the P waves should be upright and rounded and uniform in appearance P wave should be present before each QRS

35. Steps for Analyzing a Rhythm Strip Step 2: Evaluate QRS Complexes All of the QRS’s should be uniform and narrow in appearance

36. Steps for Analyzing a Rhythm Strip Step 2: continued Measuring the QRS less than 0.12 Begin from the point where the first wave of the complex begins to deviate from the baseline and end where the complex returns to the baseline Count the number of small boxes and multiply by o.o4 seconds

37. Steps for Analyzing a Rhythm Strip Step 3: Calculate the Atrial and Ventricular Heart Rates There are a couple of methods to discuss One will only be used by an MST Six-Second Method

38. Steps for Analyzing a Rhythm Strip Step 3: continued A normal heart rate in the resting adult is between 60 and 100 A rate below 60 bradycardia A rate above 100 tachycardia The atrial rate should be the same as the ventricular rate

39. Steps for Analyzing a Rhythm Strip Step 3: continued Six-Second Method (can be used for regular or irregular rhythm patterns) Print off six seconds of ECG paper (use markers at the top or bottom of the paper Atrial Rate Count the number of P waves within a period of six seconds and multiply that number by 10 Ventricular Rate Count the number of QRS complexes within six seconds and multiply by 10

40. Steps for Analyzing a Rhythm Strip Step 3: continued Small Box Method (best used if the rhythm is regular, but may be used if the rhythm is irregular and a rate range is given) Atrial rate Count the number of small boxes between two P waves, and find the corresponding rate on the small box calculation chart Ventricular rate Count the number of small boxes between two QRS complexes and find the corresponding rate on the small box calculation chart

41. Steps for Analyzing a Rhythm Strip Step 4: Determine the regularity of the rhythm (pattern) Measure the distance between two consecutive QRS’s and compare that distance with the other R-R intervals If the rhythm is regular, the R-R intervals will be the same

42. Steps for Analyzing a Rhythm Strip Step 5: Measure the PR intervals Count the number of small boxes from the beginning of the P wave to the beginning of the QRS Multiply this number by 0.04 seconds The PR intervals should all be the same and measure 0.12 to 0.20 seconds

43. Steps for Analyzing a Rhythm Strip Step 6: Measure the QT interval Count the number of small boxes from the beginning of the Q wave to the end of the T wave Multiply this number by 0.04 seconds 0.36 to 0.44 seconds or 9 to 11 small boxes for normal range

44. Steps for Analyzing a Rhythm Strip Step 7: Compare your findings to what is normal for the patient