Steps in Rhythm Analysis Evaluation of ECG requires systematic approach to analyzing given rhythm –Numerous methods can be used for rhythm interpretation.

Steps in Rhythm Analysis Evaluation of ECG requires systematic approach to analyzing given rhythm –Numerous methods can be used for rhythm interpretation –Text uses method that first looks at QRS complex Most important observation in life-threatening dysrhythmias Followed by P waves and relationship between P waves and QRS Rate Rhythm P-R interval Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.1

Steps in Rhythm Analysis Questions paramedic must ask in any rhythm analysis to determine presence or potential for life-threatening rhythm disturbances –Is the patient sick? –What is the heart rate? –Are there normal looking QRS complexes? –Are there normal looking P waves? –What is the relationship between the P waves and QRS complexes? Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.2

Analyze the QRS Complex Analyze QRS complex for regularity and width –QRS complexes ≤ 0.10 second wide (less than three small squares) are supraventricular in origin These complexes are normal –Complexes ≥ 0.12 second wide may indicate conduction abnormality in ventricles May indicate that focus originates in ventricles and is abnormal Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.3

Analyze the P Waves Normal P wave in lead II is positive and smoothly rounded and usually precedes each QRS complex, indicating that pacemaker originates in SA node –Paramedic should observe the following five components when evaluating P waves Are P waves present? Are P waves occurring at regular intervals? Is there one P wave for each QRS complex, and is there a QRS complex following each P wave? Are P waves upright or inverted? Do they all look alike? (P waves that look alike and are regular are likely from same pacemaker.) Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.5

Analyze the Rate Analysis of heart rate may be done in a number of ways –Methods for calculating heart rate Heart rate calculator rulers Triplicate method R-R method 6-second count method Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.7

Analyze the Rate Determined by analyzing ventricular rate (QRS complex) –Normal adult heart rate is between 60 and 99 beats/minute If ventricular rate is less than 60 beats/minute, considered bradycardia If rate is greater than or equal to 100 beats/minute, considered tachycardia Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.8

Heart Rate Calculator Rulers Available from number of manufacturers –Follow directions that come with rulers –Are reasonably accurate if rhythm is regular –Mechanical device or tool should not be relied on solely to determine heart rate There will be occasions when device or tool is not readily available Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.10

Triplicate Method Requires memorizing two sets of numbers –300-150-100 –75-60-50 Numbers are derived from distance between heavy black lines (each representing 1/300 minute) Two 1/300-minute units = 2/300 minute = 1/150 minute, or heart rate of 150 beats/minute Three 1/300-minute units = 3/300 minute = 1/100 minute, or heart rate of 100 beats/minute Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.13

Triplicate Method Using triplicates, the paramedic can calculate heart rate as follows –Select an R wave that lines up with dark vertical line –Number next six dark vertical lines consecutively from left to right as 300-150-100 and 75-60-50 –Identify where next R wave falls with reference to six dark vertical lines If R wave falls on 75, heart rate = 75 beats/minute If R wave falls halfway between 100 and 150, heart rate is about 125 beats/minute Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.15

R-R Method May be used several different ways to calculate heart rate –Rhythm must be regular to obtain accurate reading –Method works equally well for slow rates Method 1. Measure distance in seconds between peaks of two consecutive R waves –Divide this number into 60 to obtain heart rate Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.16

R-R Method Method 2. Count the large squares between the peaks of two consecutive R waves –Divide this number into 300 to obtain heart rate Method 3. Count small squares between peaks of two consecutive R waves –Divide this number into 1500 to obtain heart rate Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.18

6-Second Count Method Least accurate method of determining heart rate –Useful for quickly obtaining an approximate rate in regular and irregular rhythms Short vertical lines at top of most ECG graph papers are divided into 3-second intervals when run at standard speed of 25 mm/second –Two of these intervals = 6 seconds –Heart rate is calculated by counting number of QRS complexes in 6-second interval This number is multiplied by 10 Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.21

Step 4: Analyze the Rhythm To analyze ventricular rhythm, compare R-R intervals on ECG tracing in systematic way from left to right –Measurement may be taken using ECG calipers or pen and paper –Using calipers, place one tip of caliper on peak of one R wave and adjust other tip so that it rests on peak of adjacent R wave –Use caliper to map distance of R-R interval to evaluate evenness and regularity P waves may be mapped for regularity in this same way Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.24

Step 4: Analyze the Rhythm In absence of calipers, use similar method of evaluating R-R interval using pen and paper –Place straight edge of paper near peaks of R waves and mark off distance between two other consecutive R waves –Compare this R-R interval with other R-R intervals in ECG tracing Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.25

Step 4: Analyze the Rhythm If distances between R waves are equal or vary by less than 0.16 second (four small squares), rhythm is regular –If shortest and longest R-R intervals vary by more than 0.16 second, rhythm is irregular –Irregular rhythms may be classified further –May be classified as regularly irregular Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.27

Step 4: Analyze the Rhythm In this case, irregularity has pattern, also called “group beating” Irregular rhythms also may be occasionally irregular –In this case, only one or two R-R intervals are unequal Irregular rhythms may be irregularly irregular –In this case, rhythm is totally irregular –No relationship is seen between R-R intervals Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.28

Step 5: Analyze the P-R Interval P-R interval indicates time it takes for electrical impulse to be conducted through atria and AV node –Interval should be constant across ECG tracing –Prolonged P-R interval (greater than 0.20 second) indicates delay in conduction of impulse through AV node or bundle of His –Delay is called atrioventricular block Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.30

Step 5: Analyze the P-R Interval Short P-R interval (less than 0.12 second) indicates impulse progressed from atria to ventricles through pathways other than AV node –Known as accessory pathway syndrome, most common of which is Wolff-Parkinson- White syndrome Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.31

Using Five Steps to Analyze Rhythm Normal sequence of atrial and ventricular activation as it relates to ECG tracing is as follows –Each P wave (atrial depolarization) is followed by normal QRS complex (ventricular depolarization) and T wave (ventricular repolarization) –All QRS complexes are preceded by P waves –P-R interval is within normal limits, and R-R interval is regular –Five steps in ECG rhythm interpretation can be applied to rhythm Copyright © 2012 by Mosby, an imprint of Elsevier Inc. All rights reserved.33

Steps in Rhythm Analysis Evaluation of ECG requires systematic approach to analyzing given rhythm –Numerous methods can be used for rhythm interpretation.

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Steps in Rhythm Analysis Evaluation of ECG requires systematic approach to analyzing given rhythm –Numerous methods can be used for rhythm interpretation.

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