Sinus Tachycardia

Basic EKG Rhythm Analysis Guide The ECG tracing provides a variety of clues as to what is happening within the heart. These clues include heart rate, regularity or irregularity of the rhythm, interval measurements and characteristics of each individual waveform. Think of the ECG strip as a unique fingerprint in which you are the detective conducting the investigation. Like a detective, you will need to pay attention to details. In addition to a detailed analysis, you will also need a “recipe” for ECG interpretation, just like a cook needs a recipe for a complex dessert. If you follow the interpretation “recipe” each time you analyze a strip, your skills will grow and your interpretations will be consistently accurate. Remember to print a 6 second strip (or longer) each and every time you begin an interpretation. Follow the six basic steps (your recipe) for rhythm interpretation. When looking at a cardiac rhythm ask yourself the following questions. 1. Calculate heart rate Calculate both the atrial and ventricular rates. Normally the atrial rate is the same as the ventricular rate. Is this true in the ECG strip you are analyzing? Remember the normal heart rate for most individuals falls between the range of 60-80 beats/minute. Normal Findings: Ƈ7KH+5VKRXOGEHEHWZHHQ-80 beats/minute. Abnormal Findings: Ƈ+HDUWUDWHVOHVVWKDQEHDWVPLQXWHDUH typically labeled as slow or bradycardic. Ƈ7KHDWULDOUDWHVKRXOGEHWKHVDPHDVWKH ventricular rate. Ƈ+HDUWUDWHVJUHDWHUWKDQEHDWVPLQXWHDUH typically labeled fast or tachycardic. 2. Regularity of the rhythm The assessment of the regularity of the rhythm - Is the rhythm regular or is it irregular? To assess the regularity, you will need to place the legs of your calipers on two consecutive R waves. This is your “R to R” or “R-R” interval. Without moving the width of the calipers, march through the rhythm as you travel from R wave to R wave. If you do not have calipers, another method to determine regularity is to make a small mark on a piece of paper over two consecutive R waves, then move the paper to the next R wave and see if the dots line up/march out. Do the R waves follow a regular pattern? If so, the ventricular rhythm is called regular rhythm. Normal ECG rhythms are regular in their pattern. If the R-R interval varies in the number of ECG small boxes between them, you are dealing with an irregular rhythm. Do the same type of assessment with the atrial rhythm. Put your calipers at the beginning (or upslope) of a P wave. Put the other end of your caliper at the beginning of the next P wave or make a small mark on a piece of paper over two consecutive P waves. This is the P-P interval. Lift your calipers and begin marching through the strip looking for the pattern of regularity of the P waves. If the SA node is firing at a constant beat, the P-P interval will be regular. Do not estimate. Use an EKG caliber or paper. Normal Findings: The R-R intervals are regular. The P-P intervals are regular. There is one P for every QRS. Regular rhythm Abnormal Findings: The R-R intervals are irregular The P-P intervals are irregular. There is more than one P for each QRS. Irregular Rhythm Very few rhythms are irregular. For example, atrial fibrillation is always irregular (more on this rhythm later). Therefore, if your rhythm is regular it cannot be atrial fibrillation. 3. Examine P wave First, you must go on a “P hunt” and find the P waves. Once you have identified them, assess their characteristics. Normal Findings: P waves should be regular (march out the P-P intervals with your calipers). P waves have a symmetrical shape, usually upright and rounded P waves should all look alike (uniform) and should point in the same direction There should be one P for every QRS (or a 1:1 relationship). The QRS associated with P-waves Abnormal Findings: A P wave is not followed by a QRS complex. There are more P waves than QRS complexes. completely dissociated The QRS complexes are completely dissociated from P wave 4. Measure PR interval Remember that the P to R interval represents the time it takes an impulse to travel from the atria through the AV node. The P to R interval is measured from the beginning of the P wave to the beginning of the QRS complex. This is a bit confusing as you might think it is a measurement from the beginning of the P wave to the beginning of the R wave.... but it is actually only measured from the beginning P to the beginning of the Q wave. Think of it as a “P to Q measurement” despite the fact that it is called a PR interval. x Normal Findings: The PR interval (or time travel from SA to AV nodes) is between 0.12 to 0.20 seconds. The PR intervals are constant throughout the rhythm. Abnormal Findings: The PR interval is > .20 seconds (this might indicate delayed travel time from SA to AV node). The PR interval is irregular in measurement (irregular or varying PR intervals may indicate some type of SA-AV conduction problem and possible conduction heart block). 5. Measure QRS Complex The QRS complex represents ventricular depolarization. The QRS complex consists of three waves: the Q wave, the R wave, and the S wave. It is measured from the beginning of the Q wave to the end of S wave. Normal ventricular conduction and depolarization takes no more than .12 seconds. Normal Findings: All the QRS complexes have uniformity throughout (the same size, shape and direction). All QRS complexes are of equal duration or width. The R to R interval between each QRS is regular. Abnormal Findings: The QRS complexes vary in shape, width and direction. The QRS complex is >.12 seconds wide. The R to R interval between each QRS is irregular. 6. Examine ST segment (should be isoelectric) & Examine T wave (upright, flat, inverted, spiked) Normal Findings: The ST segment should be electrically neutral (or near neutral) and should be sitting on the isoelectric baseline (no greater than 1 mm above or below the isoelectric line is normal). The T wave is upright whenever the R wave is upright. The T wave deflects downward when the R wave is downward. Abnormal Findings: There is > 1mm ST segment elevation or depression from the isoelectric line. The T wave is in the opposite direction than the R wave. Rhythm Interpretation Believe it or not, after completing Step 6, you are ready to make an educated decision on naming the correct rhythm. Remember to correlate information obtained in Steps 1-6 along with your understanding of the heart’s electrophysiology. Rather than pure memorization, if you can integrate the electrophysiology with the rhythm interpretation your patient care priorities and potential treatments will make a lot more sense. Six Basic Steps for Rhythm Interpretation Summary 1. Rate (Calculate the heart rate (HR) or note the HR from the 2. Regularity (Measure the regularity or rhythm of the R waves) 3. P-wave Examination. Is there one P wave before each QRS? (there should be) 4. P to R interval (Measure the P to R interval - Is it within normal limits? It is consistent?) 5. QRS width (Measure the duration of the QRS complex) 6. Rhythm interpretation