J. ELECTROCARDIOLOGY 12 (2), 1979, 217-219
Annotation A Scale for ECG Rhythm Analysis BY JOSEPH WARTAK, M.D.*
vice has been published elsewhere 2 while a second much improved version is presented here. The concept employed in the construction of the overlay is depicted in Fig. 1 and can be described as follows. Vertical solid and dotted lines for various heart rates are printed on a transpartent plastic chart. The distance bet w e e n a d j a c e n t solid l i n e s is e q u a l and matches the length of the RR (or PP) interval at a given heart rate. The distance between the inside solid line and the inward dotted line is 15% shorter than the distance between the pair of solid lines; the distance between the inside solid line and the outward dotted line is 15% longer than the distance between the pair of solid lines. The distance between the inward and outward dotted line represents _ 15% tolerance or the difference in the interval length which is acceptable in a regular rhythm. The scale shown in Fig. 2 has 38 rows of vertical lines described above and illustrated in Fig. 1. By selecting the row appropriate for a given heart rate and by proper positioning of the lines over the P-QRS complexes it is possible to determine quickly and accurately whether the RR (or PP) intervals are equal or if they differ by less than 15% or more than 15%. When the difference between two adjacent intervals is not more t h a n 15%, i.e., one of the intervals is not more than 15% shorter or longer t h a n t h e other, t h e r h y t h m is regular. In order to evaluate the regularity of the RR (or PP) interval, the transparency should be laid over the tracing in such a manner that
SUMMARY A simple scale, w h i c h allows the E C G r e a d e r to assess the r e g u l a r i t y o f the R R (or P P ) interval and to detect the P wave train, has been presented. The evaluation of rhythm in the ECG strip record should follow a c e r t a i n logical sequence in order to be efficient, accurate and complete. The first logical steps in rhythm analysis should include the evaluation of the heart rate, morphology of the QRS complex and regularity of the RR interval. The heart rate (HR) can be determined on the basis of simple formulas (e.g., H R = 60/RR interval in seconds). The QRS complex morphology is apparent on inspection of the tracing. The regularity of the RR interval, however, can be evaluated only with the help of some devices. The most popular device is a caliper or a rule having a slide with a projecting foot. A less popular method employs a prescription blank or a similar size piece of paper and a pencil or pen I Still another device for evaluating the regularity of the RR interval is a transparent overlay with a p r e p r i n t e d scale. The first somewhat primitive version of this new de-
*Director, Medical Education Systems, Kingston, Ontario, Canada. The costs of publication of this article were defrayed in part by the payment of page charges, This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. w 1734 solely to indicate this fact. Reprint requests to: Joseph Wartak, M.D., RO. Box 1417, Kingston, Ontario, Canada, K7L 5C6.
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the peaks of the second and third R (or P) waves in lead L2 (or any other lead) will correspond to the middle solid lines in one of the rows. Such positioning allows the interpreter to assess the regularity of the first three RR (or PP) intervals. If the peaks of the first and fourth R (or P) waves coincide with the outside solid lines in the same row, all three RR (or PP) intervals are equal. If the peaks of the first and fourth R (or P) waves do not coincide with the outside solid lines but they fall between the dotted lines, all three RR (or PP) intervals are not equal but they are still regular. If the peak of the first and/or fourth R (or P) wave falls outside the dotted lines, the RR (or PP) intervals in question are irregular. By shifting the scale to the right, all other RR (or PP) intervals in the tracing can be evaluated. The scale shown in Fig. 2 can also be used to search for the P wave t r a i n in cases where the atrial activity for some beats is absent or superimposed on the QRS complex, the ST s e g m e n t or the T wave. To d e t e r m i n e the P wave train, t h e first two consecutive P waves in the tracing should be found and matched with the middle solid lines in the appropriate row. Then the search for a n y sign of atrial activity within the dotted lines in the same row begins. If a normal or p a r t i a l l y buried P wave is found, the scale should be moved in such a m a n n e r t h a t the proximal line of the middle pair will coincide with t h a t P wave and the search for any sign of atrial
Fig. 1. Diagram to depict the concept of rhythm analysis. Described in text.
activity within the dotted lines should be continued. If no sign of atrial activity is found w i t h i n the dotted lines, t h e n the patient's record under the outside solid line should be m a r k e d as t h e l o c a t i o n of t h e e x p e c t e d P wave. Next, the scale should be moved in such a m a n n e r t h a t the proximal line of the middle pair will coincide with t h a t expected P wave and the search within the dotted lines should be continued. In a similar m a n n e r the rest of the tracing can be searched for the presence of the P wave. Finally, the scale can be used to determine the heart rate. This can be accomplished by finding the pair of solid lines which coincide with the peaks of two consecutive R waves and reading off the number in the same row. It would appear t h a t the new scale described here is more versatile t h a n calipers because it can be used to determine the heart rate, to search for the P wave train and to establish the regularity of the RR (or PP) intervals. It is obvious t h a t calipers can only d e t e r m i n e equality of the RR (or PP) intervals but cannot determine their regularity. REFERENCES 1. RISEMAN,J E F AND SAGAL, E L: Cardiac Arrhythmias. MacMillan Co., New York, 1963. 2. WARTAK,J: Companion Guide to Electrocardiogram and Vectorcardiogram Interpretation, Chart 8. Medical Education Systems, Kingston, Ontario, 1977 J. ELECTROCARDIOLOGY, VOL. 12, NO. 2, 1979
A SCALE FOR ECG RHYTHM ANALYSIS
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Fig. 2. Scale for ECG rhythm analysis preprinted on a transparent plastic chart. Approximately same size as that of the working model. Described in text.
J. ELECTROCARDIOLOGY, VOL. 12, NO. 2, 1979