6 Interpretation of an EKG Strip

Anatomy of the Heart Objectives Describe the basic approach to interpretation of EKG strips Explain the five steps used in interpretation of EKG strips Explain how to calculate heart rate, given a 6-second strip Name four causes of artifact

General Rules First and most important, look at your patient Read EVERY strip from left to right, starting at the beginning of the strip Apply the five-step systematic approach that you will learn in this chapter Avoid shortcuts and assumptions

General Rules A quick glance at a strip will often lead to an incorrect interpretation Ask and answer each question in the five-step approach in the order that is presented here… this is important for consistency Master the accepted parameters for each dysrhythmia and apply them to each of the five steps when analyzing the strip

The Five-Step Approach This five-step approach, in order of application, includes analysis of the following Step 1: Heart rate Step 2: Heart rhythm Step 3: P wave Step 4: PR interval Step 5: QRS complex

Step 1: Heart Rate Number of electrical impulses as represented by PQRST complexes conducted through the myocardium in 60 seconds (1 min) Atrial rate Counting the number of P waves noted Ventricular rate Counting the number of QRS complexes noted

Heart Rate SA node discharges impulses at a rate of 60-100 times per minute Bradycardia Heart rate less than 60 bpm Tachycardia Heart rate greater than 100

Heart Rate Determination Two methods of determination of the heart rate 1. The 6-second method Denotes a 6-second interval on EKG strip Strip is marked by 3-or 6-second tick marks on the top or bottom of graph paper Count the number of QRS complexes occurring within the 6-second interval and then multiply that number by 10

Sample of 6-Second Method

Two Methods to Determine Heart Rate Two methods of determination of the heart rate 2. Second method is the R-R interval method Most accurate if heart rate is regular An estimation of the heart rate Look at QRS complex that falls on a heavy line on the strip, count number of large boxes between this R wave and the next R wave Divide this number into 300 Or use small boxes and divide by 1500

Sample Strip for R - R Method

STEP 2: Heart Rhythm Rhythm Classified as Sequential beating of the heart as a result of the generation of electrical impulses Classified as Regular pattern Interval between R waves are regular Irregular pattern Interval between R waves are not regular

Regular Rhythm Measure the intervals between P to P waves or R to R waves If the intervals vary by less than 0.06 seconds or 1.5 small boxes, we can consider the rhythm to be regular

Irregular Rhythm If the intervals between the P to P waves or R to R waves are variable by greater than 0.06 seconds (1 ½ boxes), rhythm is considered irregular Regularly irregular Irregular rhythms that occur in a pattern Occasionally irregular Intervals of only one or two R to R are uneven

Irregular Rhythm If the intervals between the P to P waves or R to R waves are variable by greater than 0.06 seconds, rhythm is considered irregular Irregularly irregular R to R intervals exhibit no similarity

Practice Strip for Rate and Rhythm Analysis Pg 63 top

Practice Strip for Rate and Rhythm Analysis Pg 63 bottom

STEP 3: The P Wave P wave is produced when the right and left atria depolarize First deviation from the isoelectric line Should be rounded and upright P wave is SA node pacing or firing at regular intervals This pattern is referred to as a sinus rhythm

P Wave: Five Questions to Ask Step 1: Are P waves present? Step 2: Are P waves occurring regularly? Step 3: Is there one P wave present for each QRS complex present and/or is there a QRS for each P wave present? Step 4: Are the P waves smooth, rounded,and upright in appearance, or are they inverted? Step 5: Do all P waves look similar

P Wave Practice Strip

STEP 4: The PR Interval Measures the time interval from the onset of atrial contraction to onset of ventricular contraction Measured from onset of P wave to the onset of the QRS complex Normal interval is 0.12-0.20 seconds (3-5 small squares)

PR Interval: 3 Questions to Ask 1. Are PR intervals greater than 0.20 seconds? 2. Are PR intervals less than 0.12 seconds? 3. Are the PR intervals constant across the EKG strip?

PR Interval Practice Strip

STEP 5: The QRS Complex Represents depolarization or contraction of the ventricles Q wave First negative or downward deflection of this large complex R wave First upward or positive deflection following the P wave (tallest waveform) S wave The sharp, negative, or downward deflection that follows the R wave

QRS Complex: 3 Questions to Ask 1. Are QRS intervals greater than 0.12 seconds (wide) or are they less than 0.12 secs (Narrow)? 2. Are the QRS complexes similar in appearance across the EKG strip?

Sample QRS Rhythm Strip

The ST Segment Begins with the end of the QRS complex and ends with the onset of the T wave (consistent with isoelectric line) J-point Point at which the QRS complex meets the ST segment If ST segment is elevated or depressed, myocardial ischemia or injury may be indicated

The T Wave Produced by ventricular repolarization or relaxation Commonly seen as the first upward or positive deflection following the QRS complex

The U Wave Usually not visible on EKG strips Cause or origin not completely understood Typically follows the T wave Appears much smaller than T wave, rounded, upright, or positive deflection if they are present

Artifact EKG waveforms from sources outside the heart Interference seen on a monitor or EKG strip 4 causes Patient movement Loose or defective electrodes (fuzzy baseline) Clean your pt…… Improper grounding (60 cycle interference) Faulty EKG apparatus

Sample Rhythm Strip of Artifact