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A simple method of checking the ECG paper speed
J. ELECTROCARDIOLOGY, 8 (4) 369-371
Annotation:
A Simple Method of Checking the ECG Paper Speed BY HERMAN N. UHLEY, M.D.*
SUMMARY
influence t h e r a t e derived. I t is t h e p u r p o s e of t h i s p a p e r to d e m o n s t r a t e a s i m p l e t e c h n i q u e b y w h i c h t h e e x a c t speed of p a p e r m o v e m e n t c a n be e a s i l y m e a s u r e d a n d u s e d to d e t e r m i n e t h e precise r a t e of a n i m p l a n t e d p a c e m a k e r .
A simple method of determining accurate rates on ECG machines has been described. A short-wave radio, capable of tuning station WWV (5, 10 or 15 MHz) and a telephone amplifier may be used to place the precise 1 second interval pulses on the ECG, from which exact paper speed is determined. This information may then be used to calculate the precise rate of an implanted pacemaker stimulus for evaluating pacemaker battery life.
MATERIALS AND METHODS The need is to provide standard pulses occurring precisely one second apart. A simple technique consists of utilizing the radio signals from the National Bureau of Standards which provide the necessary one second identification m a r k e r s . 1 These signals are used by navigators in the calculation of longitude and are broadcast on radio station WWV from Fort Collins, Colorado on 5, 10 and 15 megahertz. A standard short wave radio capable of receiving station WWV is tuned for the best signal on 5, 10 or 15 megahertz. The output of the receiver is attenuated and fed into the ECG input. The short wave receiver and ECG may be separated and the same determination can be made over long distances with the use of a telephone system and an ordinary telephone amplifier with two wires from the speaker connected to the ECG input (Fig. 1). The output of the amplifier must be kept very low to prevent the amplifier signal from overdriving the ECG galvanometer. The technique used consists of recording the signal generated at precisely one sec intervals and simply counting the number of millimeters encompassed by two successive corresponding points. Thus the speed of the paper in mm/sec can be obtained.
T h e h e a r t r a t e c a n be d e t e r m i n e d by seve r a l d i f f e r e n t m e t h o d s f r o m t h e i n s c r i p t i o n of t h e QRS c o m p l e x e s on t h e e l e c t r o c a r d i o g r a m (ECG). However, the accuracy of rate d e t e r m i n a t i o n is d e p e n d e n t on t h e d r i v e m o t o r m o v i n g t h e p a p e r a t a c o n s t a n t speed ( u s u a l l y 25 mm/sec). I f t h e p a p e r m o v e s s l o w e r or f a s t e r , t h e d e t e r m i n a t i o n of t h e h e a r t r a t e will be altered. O r d i n a r i l y s l i g h t v a r i a t i o n s in t h e r a t e a r e of no clinical i m p o r t a n c e ; h o w e v e r , w h e n s l i g h t c h a n g e s in t h e r a t e a r e u s e d to d e t e r m i n e t h e p o s s i b i l i t y of i m p l a n t e d pacemaker battery failure, it b e c o m e s e s s e n t i a l for t h e clinician to recognize e r r o r in his r e c o r d i n g m a c h i n e w h i c h w o u l d in t u r n
Speed of paper =
mm between 2 pulses sea.
Dividing the number of millimeters into one gives the time required to move the paper one millimeter. 1 Time in seconds required = to move paper 1 mm mm between pulses. *In Charge, Department of Electrocardiography and Coronary Care Unit, Mount Zion Hospital and Medical Center, San Francisco, California. Reprint requests to: H e r m a n N. Uhley, M.D., Mount Zion Hospital and Medical Center, P.O.B. 7921, San Francisco, CA 94120.
For example, if the time between the one sec pulses is 25 mm, then 25 mm = 1 sec 1 mm = 1/25 sec = .04 sec (times required to move paper 1 mm).
369
370
UHLEY
EKG M~chine
Fig. 1. Method for recording precise 1 second t i m e i n t e r v a l s from radio s t a t i o n W W V on a r e m o t e strip recorder.
I
Fig. 2. E x a m p l e s ot t h e t]me pulses recorded on different E C G machines.
d. ELECTROCARDIOLOGY, VOL. 8, NO. 4, 1975
CHECKING ECG PAPER SPEED
Accordingly, in determining the rate recorded with a given ECG machine, the distance between the corresponding points of two successive QRS complexes (or pacemaker stimulus spikes) is measured. The number of mm are then multiplied by the time in sec required by the given ECG machine to move the paper 1 mm as determined by the signal from radio station WWV. The product is the cycle length in sec from which the rate in beats per minute may be obtained. 60 Frequency in beats/min = cycle length (sec)
RESULTS Figure 2 is a photograph of the signals received from the radio station WWV recorded on different ECG machines. Ten ECG machines were used in this study and the results are as follows: Machine: A B C D E F G H I J
Paper speed mm/sec.: 27.8 25.7 25.0 24.9 25.0 23 (22-24) 25,5 26,2 26.1 26.0
Seconds for 1 mm movement: 0.036 0.039 0.040 0.040 0.040 0.043 (0,045-0,042) 0.039 0.038 0.038 0.038
DISCUSSION Various methods of evaluating pacemaker battery life have been emphasized. However, the most widely used means of predicting bat-
J. ELECTROCARDIOLOGY, VOL. 8, NO. 4, 1975
371
tery failure is the determination of the exact pacemaker rate. Precision methods of rate determination may require a frequency meter, oscilloscope or other costly equipment. Telephone transmission of signals to a remote center with sophisticated rate measuring equipment has also been used. The technique of counting the 60 Hertz interference artifact may be useful, 2 particularly if the recording device is not limited to 25 mm/sec, where it is difficult to count the very close pulses. With the method described in this paper, the practicing physician can determine the motor speed and evaluate the accuracy of his rate determinations. This study shows t h a t in random selection of 10 ECG machines, 2 machines would have recorded the rate precisely, 6 would have recorded the rate slowly and 2 machines would have recorded the rate faster t h a n the actual rate. Since slight changes in rate have been used as criteria for p a c e m a k e r b a t t e r y failure, knowledge of a paper speed error is import a n t , especially if serial p a c e m a k e r r a t e determinations are made on different ECG machines.
REFERENCES 1. BOWDITCH, N: American Practical Navigator. H O Publication No. 9, U S Navy Hydrographic Office, U S Government P r i n t i n g Office, Washington, D C, 1966, p. 492 2. KOSTIS, J B AND FEARN, W: Accurate electrocardiographic measurement of the rate of artificial pacemakers. Ann Int Med 78:711, 1973
Annotation:
A Simple Method of Checking the ECG Paper Speed BY HERMAN N. UHLEY, M.D.*
SUMMARY
influence t h e r a t e derived. I t is t h e p u r p o s e of t h i s p a p e r to d e m o n s t r a t e a s i m p l e t e c h n i q u e b y w h i c h t h e e x a c t speed of p a p e r m o v e m e n t c a n be e a s i l y m e a s u r e d a n d u s e d to d e t e r m i n e t h e precise r a t e of a n i m p l a n t e d p a c e m a k e r .
A simple method of determining accurate rates on ECG machines has been described. A short-wave radio, capable of tuning station WWV (5, 10 or 15 MHz) and a telephone amplifier may be used to place the precise 1 second interval pulses on the ECG, from which exact paper speed is determined. This information may then be used to calculate the precise rate of an implanted pacemaker stimulus for evaluating pacemaker battery life.
MATERIALS AND METHODS The need is to provide standard pulses occurring precisely one second apart. A simple technique consists of utilizing the radio signals from the National Bureau of Standards which provide the necessary one second identification m a r k e r s . 1 These signals are used by navigators in the calculation of longitude and are broadcast on radio station WWV from Fort Collins, Colorado on 5, 10 and 15 megahertz. A standard short wave radio capable of receiving station WWV is tuned for the best signal on 5, 10 or 15 megahertz. The output of the receiver is attenuated and fed into the ECG input. The short wave receiver and ECG may be separated and the same determination can be made over long distances with the use of a telephone system and an ordinary telephone amplifier with two wires from the speaker connected to the ECG input (Fig. 1). The output of the amplifier must be kept very low to prevent the amplifier signal from overdriving the ECG galvanometer. The technique used consists of recording the signal generated at precisely one sec intervals and simply counting the number of millimeters encompassed by two successive corresponding points. Thus the speed of the paper in mm/sec can be obtained.
T h e h e a r t r a t e c a n be d e t e r m i n e d by seve r a l d i f f e r e n t m e t h o d s f r o m t h e i n s c r i p t i o n of t h e QRS c o m p l e x e s on t h e e l e c t r o c a r d i o g r a m (ECG). However, the accuracy of rate d e t e r m i n a t i o n is d e p e n d e n t on t h e d r i v e m o t o r m o v i n g t h e p a p e r a t a c o n s t a n t speed ( u s u a l l y 25 mm/sec). I f t h e p a p e r m o v e s s l o w e r or f a s t e r , t h e d e t e r m i n a t i o n of t h e h e a r t r a t e will be altered. O r d i n a r i l y s l i g h t v a r i a t i o n s in t h e r a t e a r e of no clinical i m p o r t a n c e ; h o w e v e r , w h e n s l i g h t c h a n g e s in t h e r a t e a r e u s e d to d e t e r m i n e t h e p o s s i b i l i t y of i m p l a n t e d pacemaker battery failure, it b e c o m e s e s s e n t i a l for t h e clinician to recognize e r r o r in his r e c o r d i n g m a c h i n e w h i c h w o u l d in t u r n
Speed of paper =
mm between 2 pulses sea.
Dividing the number of millimeters into one gives the time required to move the paper one millimeter. 1 Time in seconds required = to move paper 1 mm mm between pulses. *In Charge, Department of Electrocardiography and Coronary Care Unit, Mount Zion Hospital and Medical Center, San Francisco, California. Reprint requests to: H e r m a n N. Uhley, M.D., Mount Zion Hospital and Medical Center, P.O.B. 7921, San Francisco, CA 94120.
For example, if the time between the one sec pulses is 25 mm, then 25 mm = 1 sec 1 mm = 1/25 sec = .04 sec (times required to move paper 1 mm).
369
370
UHLEY
EKG M~chine
Fig. 1. Method for recording precise 1 second t i m e i n t e r v a l s from radio s t a t i o n W W V on a r e m o t e strip recorder.
I
Fig. 2. E x a m p l e s ot t h e t]me pulses recorded on different E C G machines.
d. ELECTROCARDIOLOGY, VOL. 8, NO. 4, 1975
CHECKING ECG PAPER SPEED
Accordingly, in determining the rate recorded with a given ECG machine, the distance between the corresponding points of two successive QRS complexes (or pacemaker stimulus spikes) is measured. The number of mm are then multiplied by the time in sec required by the given ECG machine to move the paper 1 mm as determined by the signal from radio station WWV. The product is the cycle length in sec from which the rate in beats per minute may be obtained. 60 Frequency in beats/min = cycle length (sec)
RESULTS Figure 2 is a photograph of the signals received from the radio station WWV recorded on different ECG machines. Ten ECG machines were used in this study and the results are as follows: Machine: A B C D E F G H I J
Paper speed mm/sec.: 27.8 25.7 25.0 24.9 25.0 23 (22-24) 25,5 26,2 26.1 26.0
Seconds for 1 mm movement: 0.036 0.039 0.040 0.040 0.040 0.043 (0,045-0,042) 0.039 0.038 0.038 0.038
DISCUSSION Various methods of evaluating pacemaker battery life have been emphasized. However, the most widely used means of predicting bat-
J. ELECTROCARDIOLOGY, VOL. 8, NO. 4, 1975
371
tery failure is the determination of the exact pacemaker rate. Precision methods of rate determination may require a frequency meter, oscilloscope or other costly equipment. Telephone transmission of signals to a remote center with sophisticated rate measuring equipment has also been used. The technique of counting the 60 Hertz interference artifact may be useful, 2 particularly if the recording device is not limited to 25 mm/sec, where it is difficult to count the very close pulses. With the method described in this paper, the practicing physician can determine the motor speed and evaluate the accuracy of his rate determinations. This study shows t h a t in random selection of 10 ECG machines, 2 machines would have recorded the rate precisely, 6 would have recorded the rate slowly and 2 machines would have recorded the rate faster t h a n the actual rate. Since slight changes in rate have been used as criteria for p a c e m a k e r b a t t e r y failure, knowledge of a paper speed error is import a n t , especially if serial p a c e m a k e r r a t e determinations are made on different ECG machines.
REFERENCES 1. BOWDITCH, N: American Practical Navigator. H O Publication No. 9, U S Navy Hydrographic Office, U S Government P r i n t i n g Office, Washington, D C, 1966, p. 492 2. KOSTIS, J B AND FEARN, W: Accurate electrocardiographic measurement of the rate of artificial pacemakers. Ann Int Med 78:711, 1973