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A 12-lead patient cable for electrocardiographic exercise testing
A 124ead patient electrocardiographic
cable for exercise
testing
I. Martin Grais, M.D.* Donald E. Campbell, E.E. Robert J. Adolph, M.D. Cincinnati
Ohio
In the absence of a generally accepted protocol for treadmill exercise testing, we have designed a cable which is simple and inexpensive to construct and is adaptable to any of the more commonly utilized protocols employing partial’ or full 12lead’ electrocardiographic recordings either before, during, or after exercise. Commercially available cables were found to be either inflexible, unnecessarily heavy, too short, unshielded, or limited to only one chest lead. The electrode8 designed to be used with these cables were unsuitable for secure attachment to the patient. The patient cable to be reported is adaptable to any single or multiple channel electrocardiographic recorder and permits the pre-exercise application of all ten electrodes. The purpose of this paper is to report the design, fabrication, and results of the first 16 months’ experience with such a cable. Methods
Design considerations. In the operation of the standard electrocardiographic recorder the technician switches to seven different lead positions: I, II, III, aV,, aV, aV, and V. With the switch in the V position, a suction cup electrode Froin the Univereity
Division of Cardiology, of Cincinnati Medical
Supported by United and HE-6446. Additional Aseocation. Received Reprint Laboratory, 45229.
support
States
Public
is acknowledged
for publication requests H/3
June
to: Dr. Cincinnati
*Dr. Grain wae supported Grant T&ZOO.
Department of Internal Medicine, Center, Cincinnati, Ohio. Health
Service
Grants
from
Southwestern
HE-6307 Ohio
Heart
6, 1973. Robert J. General
by the Veterans
Adolph, Hoepital,
Cardiac Reeearch Cincinnati, Ohio
Administration
February, 1974, Vol. 87, No. 2, pp. 203-208
Training
is moved manually through the six precordial positions. Using the cable described in this report, the operator can switch rapidly “through” six pre-attached V leads. That is, with the six precordial electrode8 in place, each electrode lead wire has a separate position in the cable. A selector switch has been interposed in the cable and conveniently attached to the recorder so that when the recorder selector switch is. in the V position the additional cable switch dials each precordial lead The circuit design for the cable is shown in Fig. 1 and the component parts in Table I. The finiahed cable, which coats approximately 32 dollars for parts, is illustrated in Fig. 2 and was constructed as fOllOW8. Cable constructbon. Align ten 17-foot length8 of color-coded number 28 stranded wire (Table I). Strip one-half inch of insulation from one end of each wire. Twist and solder the stripped ends together. Solder the twisted ends to a pull wire (Table 11 with a lap joint so as to minimize its bulk. Tie the u&ripped ends to a solid structure such as a door knob, making sure that each lead wire is taut. A working space of at least 34 feet in length and in a straight line is required Insert a scriber or awl point in the end of the 24 foot flat braided shield (Table I) to form a hole and bunch the braided shield to maximum diameter and minimum length. Slide the braided shield over the pull wire and over the ten lead wires until the end nearest the pull wire covers only one inch of the pull wire near the solder joint. Hold the braided shield at this point with tape and pull the shield so that it covers the ten lead wires tightly over their entire length. Untie the unsoldered ends of the ten strands. Remove the tape and unsolder the ten lead wires from the
American Heart Journal
203
Grab,
Campbell,
and
Table I. Materials
Adolph
for cable construction I
Item Rubber tubing Wire Switch Box Connector Braided shield Connector Connector Connector Connector Connector Grommet Knob Lacing cord Pull wire Lubricant
I
I
I
C&&Zntity 17 feet 170 feet One One One 20 feet One One One One Six TWO
One 10 feet 20 feet As needed
Description Neoprene tubing 3116 I.D., 1132 wall Number 28 stranded, vinyl insulation 12 position, one pole 2” X 2” X 1 l/r” with cover Flat braided shielding White tip jack Red tip jack Black tip jack Green tip jack Brown tip jack Rubber grommet Bakelite Flat Number 12 solid copper Wire pulling lubricant
l 17 feet each of the following colors: black, brown, red, orange, yellow, tFor Hewlett-Packard 1511A EKG single channel recorder.
pull wire. Then solder the end of the shield to the pull wire after wrapping a bit of bare wire around the braided shield end where it covers the pull wire so as to minimize bulk. Tie the unsoldered end of the braided shield to a door knob; an assistant pulls on the free end of the pull wire making the braided shield taut. Apply a liberal quantity of wire-pulling lubricant to both the pull wire and the braided shield. Insert the pull wire into the rubber tubing which will have to be alternately pushed and pulled over the pull wire. When the rubber tubing covers the pull wire the assistant again pulls the wire so as to ,achieve minimum diameter of the braided shield and allow the rubber’ tubing to be moved gradually onto the braided shield. This cannot be accomplished without lubricant or with the wrong size shield or rubber tubing. If the tubing is pushed too vigorously it will telescope; if it is pulled too hard it will “neck down.” The best procedure is to move the tubing gradually over the braided shield a section at a time with a peristaltic motion, alternately pushing and pulling. Cut the cable from the pull wire, trim the ends, and connect to the switch box which in turn is then connected to the recorder connector according to the schematic diagram (Fig. 1). Using diagonal wire cutters, make two oppositely directed cuts resulting in a small dia-
Manufacturer
and No.
Wright R 841-18 Alpha 1852 Centralab PSA 201 LMB M-018 Switchcraft 12BL6Mt Alpha 1230 Johnson 105-701 Johnson 105-702 Johnson 105-703 Johnson 105704 Johnson 105-708 General Cement 7566 Km-z-Kaech S-647-3L Ludlow N6 Belden 8011 Ideal 31-350
green, blue, violet, grey, white.
mond-shaped hole in the rubber tubing at a point 14 inches from the patient end of the cable. Care must be taken to avoid cutting the braided shield which will be exposed through the l/8 inch hole made in the tubing. Use a scriber to spread the shield and expose the wires. By moving the scriber sideways, individual wires can be identified and the desired one selectively extracted. Extract one inch of the black wire through one hole. Repeat the procedure with the white wire. Cut each wire at the point where it re-enters the patient end of the cable. This will result in one inch leads extending from the hole in the cable and will leave the unconnected wires in the last 14 inches of the cable. The unconnected wires will maintain the diameter of the cable and give support for the jacks which will be laced to the cable. Repeat these steps for the other wires in the cable as follows: brown and violet wires at 11 inches, orange and yellow wires at 8 inches, gray and blue wires at 5 inches, and red and green wires at 2 inches. Solder the appropriate color tip jack (Fig. 1) to each of the leads coming out of the cable and tie them tightly to the cable with lacing cord running between the body of the jack and its shell (Fig. 2). Screw the shell tightly after the cord is tied. The jack can be held more securely if a shallow groove is turned on each shell near the wire end
February,
1974, Vol. 87, NO. 2
Twelve-lead patient cable for ECG exercisetesting
JACK COLOR
ELECTRODE JACKS
CABLE WIRES
CABLE
SELECTOR SWITCH
PIN CONNECTION
0 Brown
VI
0
Brown
v2
0
Brown
v3
0
brown
04
violet
0 0
:
0 orange
0 0
Brown
v4
0
yellow
0
Brown
v5
o
gray
0
Brown
V6
Green
RL
Red
LL
Black
LA
White
RA
0
blue
white shield ---------I-----------
6 0
Fig. 1. Schematic representation cable is on the right.
of the cable
circuitry.
and another loop of lacing cord tied around the cable and in this groove. The tips of some fluid column electrode leads may fit too tightly in these jacks. This can be remedied by drilling out the solid metal length of the jack hole with a number 44 drill. The depth to be drilled is 3/32 inch, as drilling deeper into the contact area will damage the jack. Each jack is then labelled. Patient application. Meticulous technique in skin preparation and application of electrodes is recommended in order to obtain optimal recordings. The skin is prepared according to the general method of SheffieldzThe patient’s skin electrode sites are cleaned with acetone and then marked with a broad tipped permanent ink felt pen. Each site is dermabraded using a Busch and Company No. 6 round dental finishing burr*with a straight hand piece. The burr is held in a model 270 series 66-2 Dremel Moto-too1.t The spinning burr ie applied with just enough pressure to clear a spot of ink a few millimeters in diameter. In %ingst
and Co., Inc., 62 Cooper Square, New York,
tDremel
Manufacturing
Co., Racine, Wise.
American Heart Journal
Patient
end of the cable
is on the left; recorder
end of the
this way, only the keratin layer is removed, reducing akin resistance ten- to fifteenfoldS Ten Hewlett-Packard patient electrodes No. 14067C* with double stick electrode adhesive discs (part no. 14029A) are filled with electrode paste. The electrode wells are filled with paste using a disposable syringe without needle. Complete and clean filling can be assured by slightly overfilling the well and then turning the electrode upside down on a flat, hard, absorbent surface and rubbing in a forward direction once or twice. The limb and chest leads were applied in the anatomical positions recommended by Mason and colleagues4+ arm leads in the infraclavicular fossae, leg leads on the lower abdominal quadrants above the iliac crests, and the six precordial leads in the standard positions. We have applied the leg electrodes with the patient supine, but the others with the patient sitting. Electrode position can change dramatically between these two postures and movement of thick skin folds or breasts can cause significant electrode displacement.
N. Y. ‘Hewlett
Packard,
Waltbarn,
Mass.
206
Grab,
Campbell,
and Adolph
Fig. 2. Photograph
The electrode leads are fitted into their respective jacks on the cable which is attached to the recorder. The center of the cable can be looped over an overhead ceiling hook to avoid tension on the electrodes. Partial or full la-lead electrocardiograms with the patient at rest or exercising in the supine, sitting, or standing postures can then be obtained. When recording from the precordial leads, the recorder selector switch must be moved to a neutral position before moving the intra-cable selector switch to successive precordial leads. In this way the stylus never moves from the baseline position between leads.
This cable was tested in more than 230 graded treadmill exercise tests in the Cardiac Research Laboratory at the University of Cincinnati during a 16 month period The flexible shielded cable haspermitted a baseline which has been flat and artifact has been eliminated except for conditions of extreme body, arm, or hand motion or severe muscle tremor. The tracings obtained even during running on the treadmill have been interpreted easily by simple inspection (Fig. 3A) . Each patient also had supine and standing control electrocardiograms with and without hyper-
206
of the cable-electrode
system.
ventilation. No baseline wander occurred even with deep excursions of the chest. Use of the low noise electrode-cable system permitted easy evaluation of ST segments .during exercise in all patient studies. Prior application of all ten electrodes to the patient improved the diagnostic sensitivity of the treadmill test. An example of an abnormal ST segment depression which disappeared immediately after exercise is illustrated in Fig. 3B; this example would have been missed without continuous monitoring. Two exercise tests were stopped because of ST elevation in the inferior leads (Fig. 3C 1. Not infrequently exercise was stopped because of ventricular arrhythmias (Fig. 30 1. The cable has been sturdy and reliable. No repair has been necessary. Discussion
The value of submaximal and maximal exercise testing in predicting the presence of signi& cant coronary artery disease in asymptomatic subjects and in patients with atypical chest pain has been emphasised.6J Both the sensitivity of the test which is a function of developed heart rate, and the safety of the procedure require online monitoring and recording of technically
February, 1974, Vol. 87, No. 2
Turelve-lead
patient
cable for ECG exercise testing
3, A through D. A, The left-hand panel is a control electrocardiogram (Lead Va). The right-handpanel illustrates a recording taken while the normal subject was running on the treadmill at 4.2 m.p.h. and 16 per cent grade (Bruce Stage 4). IIf,These recordings were obtained from a patient with angiographically documented significant coronary artery disease. The left-hand panel demonstrates an in-exercise positive test (Lead V6). A single ventricular premature contraction was recorded. There was rapid reversion to normal immediately postexercise (right-bond pane& C, Significant coronary artery disease was documented by coronary angiography in this patient. The Ieft panel shows a positive response at four minutes of exercise (Lead Vs). Two ectopic beats were recorded. The middle panel (Lead V,) demonstrates reversion of the pattern to normal shortly thereafter, an apparent example of the “walk-through phenomenon.” An inferior lead recording (Lead aVr) taken at the same time as the middle panel (Lead Va) showed significant ST elevation, however (right par&. The test was terminated although the patient did not develop angina pectoris. D, An example of coupled multifocal premature ventricular contractions which immediately terminated the exercise in this 24-year-old woman with the late systolic click syndrome. All recordings at a paper speed of 50 mm. per second. F&
electrocardiograms in several leads. A protocol for electrocardiographic stress testing which is applicable to all circumstances
good
single
has not been described. For the test to be useful to the busy practitioner with one technician and limited office space, the requirements are different from those of the exercise physiologist with a well-equipped and staffed laboratory. This cable is applicable to both situations. The cable has several advantages not available with commercial products. Application of all ten electrodes to the patient prior to exercise enhances the diagnostic sensitivity of the test. Any or all of the 12 leads can be recorded before, during, and after exercise as well as monitored
American
Heart Journal
by oscilloscope. It has been our practice to begin a recording just prior to stopping the treadmill so as to obtain a continuous tracing while the patient assumes a sitting or lying position. Prior application of electrodes and cable frees the physician to observe the patient while the technician obtains the tracings. If the Master two-step test is employed, the usual postexercise delay due,to reattaching electrodes and the electrocardiograph cable connection is obviated. The true heart rate response can be determined and some false negative tests can be eliminated. Abnormal ST segment shifts may disappear soon after exercise is stopped and may be missed because of even a brief delay in recording (Fig. 3B). There
207
Grab,
Campbell,
and Adolph
are advantages in multiple lead monitoring. We stopped two exercise tests because of ST elevation in the inferior leads (Fig. 30, and several were discontinued because of ventricular arrhythmias (Fig. 3D). The tracings are of good quality during strenuous exercise and even during running (Fig. 3A). Precise in-exercise heart rate becomes easy to determine from the low noise tracing. A cardiotachometer would not be triggered by false signals. A low noise electrode system without additional cable artifact simplifies identification of diagnostic ST segment changes. The cable can be applied to any type of conventional exercise test and protocol, using either a standard l%-lead system or any modification of this lead system. The cable can be adapted to any electrocardiographic recorder so that available existing electrocardiographic recording equipment can be utilized In view of general interest in extending the use of submaximal exercise testing to areas such as rehabilitation of patients following myocardial infarction, functional capacity determination, therapy evaluation, and arrhythmia diagnosis this multipurpose cable could have increasing application.
208
summary A simple electrocardiographic cable for use with exercise testing has been developed which has proved to have many advantages over commercially available cables used with standard single-channel recorders. It can be adapted easily for multiple channel equipment. REFERENCES
1. Blomqvist , C. G.: Use of exercise testing for diagnostic and functional evaluation of patients with arteriosclerotic heart disease, Circulation 44:1120, 1971. 2. Sheffield, L. T.: Personal communication. 3. Shackel. B.: Skin-drillina: A method of diminishinn galvanic’skin-potentials, Am. J. Psychol. 72:114,195< 4. Mason, R. E., and Likar, I.: A new system of multiplelead exercise electrocardiography, AM HEAR+ J. 71:196.1966. 5. Mason, R. E., Likar, I., Biern, R. O., and Ross, R. S.: Multiple-lead exercise electrocardiography: Experience in 107 normal subjects and 67 patients with angina pectoris, and comparison with coronary cinearteriography in 84 patients, Circulation 36:517,1967. 6. Sheffield, L. T., Roitman, D., and Reeves, J. T.: Submaximal exercise testing, J.S.C. Med. Assoc. 8Msuppl. 1): 18, 1969. 7. McDonough, J. R., and Bruce, R. A.: Maximal exercise testing in assessing cardiovascular function, J. S. C. Med. Assoc. BMsuppl. 025, 1969.
February, 1974, Vol. 87, No. 2
cable for exercise
testing
I. Martin Grais, M.D.* Donald E. Campbell, E.E. Robert J. Adolph, M.D. Cincinnati
Ohio
In the absence of a generally accepted protocol for treadmill exercise testing, we have designed a cable which is simple and inexpensive to construct and is adaptable to any of the more commonly utilized protocols employing partial’ or full 12lead’ electrocardiographic recordings either before, during, or after exercise. Commercially available cables were found to be either inflexible, unnecessarily heavy, too short, unshielded, or limited to only one chest lead. The electrode8 designed to be used with these cables were unsuitable for secure attachment to the patient. The patient cable to be reported is adaptable to any single or multiple channel electrocardiographic recorder and permits the pre-exercise application of all ten electrodes. The purpose of this paper is to report the design, fabrication, and results of the first 16 months’ experience with such a cable. Methods
Design considerations. In the operation of the standard electrocardiographic recorder the technician switches to seven different lead positions: I, II, III, aV,, aV, aV, and V. With the switch in the V position, a suction cup electrode Froin the Univereity
Division of Cardiology, of Cincinnati Medical
Supported by United and HE-6446. Additional Aseocation. Received Reprint Laboratory, 45229.
support
States
Public
is acknowledged
for publication requests H/3
June
to: Dr. Cincinnati
*Dr. Grain wae supported Grant T&ZOO.
Department of Internal Medicine, Center, Cincinnati, Ohio. Health
Service
Grants
from
Southwestern
HE-6307 Ohio
Heart
6, 1973. Robert J. General
by the Veterans
Adolph, Hoepital,
Cardiac Reeearch Cincinnati, Ohio
Administration
February, 1974, Vol. 87, No. 2, pp. 203-208
Training
is moved manually through the six precordial positions. Using the cable described in this report, the operator can switch rapidly “through” six pre-attached V leads. That is, with the six precordial electrode8 in place, each electrode lead wire has a separate position in the cable. A selector switch has been interposed in the cable and conveniently attached to the recorder so that when the recorder selector switch is. in the V position the additional cable switch dials each precordial lead The circuit design for the cable is shown in Fig. 1 and the component parts in Table I. The finiahed cable, which coats approximately 32 dollars for parts, is illustrated in Fig. 2 and was constructed as fOllOW8. Cable constructbon. Align ten 17-foot length8 of color-coded number 28 stranded wire (Table I). Strip one-half inch of insulation from one end of each wire. Twist and solder the stripped ends together. Solder the twisted ends to a pull wire (Table 11 with a lap joint so as to minimize its bulk. Tie the u&ripped ends to a solid structure such as a door knob, making sure that each lead wire is taut. A working space of at least 34 feet in length and in a straight line is required Insert a scriber or awl point in the end of the 24 foot flat braided shield (Table I) to form a hole and bunch the braided shield to maximum diameter and minimum length. Slide the braided shield over the pull wire and over the ten lead wires until the end nearest the pull wire covers only one inch of the pull wire near the solder joint. Hold the braided shield at this point with tape and pull the shield so that it covers the ten lead wires tightly over their entire length. Untie the unsoldered ends of the ten strands. Remove the tape and unsolder the ten lead wires from the
American Heart Journal
203
Grab,
Campbell,
and
Table I. Materials
Adolph
for cable construction I
Item Rubber tubing Wire Switch Box Connector Braided shield Connector Connector Connector Connector Connector Grommet Knob Lacing cord Pull wire Lubricant
I
I
I
C&&Zntity 17 feet 170 feet One One One 20 feet One One One One Six TWO
One 10 feet 20 feet As needed
Description Neoprene tubing 3116 I.D., 1132 wall Number 28 stranded, vinyl insulation 12 position, one pole 2” X 2” X 1 l/r” with cover Flat braided shielding White tip jack Red tip jack Black tip jack Green tip jack Brown tip jack Rubber grommet Bakelite Flat Number 12 solid copper Wire pulling lubricant
l 17 feet each of the following colors: black, brown, red, orange, yellow, tFor Hewlett-Packard 1511A EKG single channel recorder.
pull wire. Then solder the end of the shield to the pull wire after wrapping a bit of bare wire around the braided shield end where it covers the pull wire so as to minimize bulk. Tie the unsoldered end of the braided shield to a door knob; an assistant pulls on the free end of the pull wire making the braided shield taut. Apply a liberal quantity of wire-pulling lubricant to both the pull wire and the braided shield. Insert the pull wire into the rubber tubing which will have to be alternately pushed and pulled over the pull wire. When the rubber tubing covers the pull wire the assistant again pulls the wire so as to ,achieve minimum diameter of the braided shield and allow the rubber’ tubing to be moved gradually onto the braided shield. This cannot be accomplished without lubricant or with the wrong size shield or rubber tubing. If the tubing is pushed too vigorously it will telescope; if it is pulled too hard it will “neck down.” The best procedure is to move the tubing gradually over the braided shield a section at a time with a peristaltic motion, alternately pushing and pulling. Cut the cable from the pull wire, trim the ends, and connect to the switch box which in turn is then connected to the recorder connector according to the schematic diagram (Fig. 1). Using diagonal wire cutters, make two oppositely directed cuts resulting in a small dia-
Manufacturer
and No.
Wright R 841-18 Alpha 1852 Centralab PSA 201 LMB M-018 Switchcraft 12BL6Mt Alpha 1230 Johnson 105-701 Johnson 105-702 Johnson 105-703 Johnson 105704 Johnson 105-708 General Cement 7566 Km-z-Kaech S-647-3L Ludlow N6 Belden 8011 Ideal 31-350
green, blue, violet, grey, white.
mond-shaped hole in the rubber tubing at a point 14 inches from the patient end of the cable. Care must be taken to avoid cutting the braided shield which will be exposed through the l/8 inch hole made in the tubing. Use a scriber to spread the shield and expose the wires. By moving the scriber sideways, individual wires can be identified and the desired one selectively extracted. Extract one inch of the black wire through one hole. Repeat the procedure with the white wire. Cut each wire at the point where it re-enters the patient end of the cable. This will result in one inch leads extending from the hole in the cable and will leave the unconnected wires in the last 14 inches of the cable. The unconnected wires will maintain the diameter of the cable and give support for the jacks which will be laced to the cable. Repeat these steps for the other wires in the cable as follows: brown and violet wires at 11 inches, orange and yellow wires at 8 inches, gray and blue wires at 5 inches, and red and green wires at 2 inches. Solder the appropriate color tip jack (Fig. 1) to each of the leads coming out of the cable and tie them tightly to the cable with lacing cord running between the body of the jack and its shell (Fig. 2). Screw the shell tightly after the cord is tied. The jack can be held more securely if a shallow groove is turned on each shell near the wire end
February,
1974, Vol. 87, NO. 2
Twelve-lead patient cable for ECG exercisetesting
JACK COLOR
ELECTRODE JACKS
CABLE WIRES
CABLE
SELECTOR SWITCH
PIN CONNECTION
0 Brown
VI
0
Brown
v2
0
Brown
v3
0
brown
04
violet
0 0
:
0 orange
0 0
Brown
v4
0
yellow
0
Brown
v5
o
gray
0
Brown
V6
Green
RL
Red
LL
Black
LA
White
RA
0
blue
white shield ---------I-----------
6 0
Fig. 1. Schematic representation cable is on the right.
of the cable
circuitry.
and another loop of lacing cord tied around the cable and in this groove. The tips of some fluid column electrode leads may fit too tightly in these jacks. This can be remedied by drilling out the solid metal length of the jack hole with a number 44 drill. The depth to be drilled is 3/32 inch, as drilling deeper into the contact area will damage the jack. Each jack is then labelled. Patient application. Meticulous technique in skin preparation and application of electrodes is recommended in order to obtain optimal recordings. The skin is prepared according to the general method of SheffieldzThe patient’s skin electrode sites are cleaned with acetone and then marked with a broad tipped permanent ink felt pen. Each site is dermabraded using a Busch and Company No. 6 round dental finishing burr*with a straight hand piece. The burr is held in a model 270 series 66-2 Dremel Moto-too1.t The spinning burr ie applied with just enough pressure to clear a spot of ink a few millimeters in diameter. In %ingst
and Co., Inc., 62 Cooper Square, New York,
tDremel
Manufacturing
Co., Racine, Wise.
American Heart Journal
Patient
end of the cable
is on the left; recorder
end of the
this way, only the keratin layer is removed, reducing akin resistance ten- to fifteenfoldS Ten Hewlett-Packard patient electrodes No. 14067C* with double stick electrode adhesive discs (part no. 14029A) are filled with electrode paste. The electrode wells are filled with paste using a disposable syringe without needle. Complete and clean filling can be assured by slightly overfilling the well and then turning the electrode upside down on a flat, hard, absorbent surface and rubbing in a forward direction once or twice. The limb and chest leads were applied in the anatomical positions recommended by Mason and colleagues4+ arm leads in the infraclavicular fossae, leg leads on the lower abdominal quadrants above the iliac crests, and the six precordial leads in the standard positions. We have applied the leg electrodes with the patient supine, but the others with the patient sitting. Electrode position can change dramatically between these two postures and movement of thick skin folds or breasts can cause significant electrode displacement.
N. Y. ‘Hewlett
Packard,
Waltbarn,
Mass.
206
Grab,
Campbell,
and Adolph
Fig. 2. Photograph
The electrode leads are fitted into their respective jacks on the cable which is attached to the recorder. The center of the cable can be looped over an overhead ceiling hook to avoid tension on the electrodes. Partial or full la-lead electrocardiograms with the patient at rest or exercising in the supine, sitting, or standing postures can then be obtained. When recording from the precordial leads, the recorder selector switch must be moved to a neutral position before moving the intra-cable selector switch to successive precordial leads. In this way the stylus never moves from the baseline position between leads.
This cable was tested in more than 230 graded treadmill exercise tests in the Cardiac Research Laboratory at the University of Cincinnati during a 16 month period The flexible shielded cable haspermitted a baseline which has been flat and artifact has been eliminated except for conditions of extreme body, arm, or hand motion or severe muscle tremor. The tracings obtained even during running on the treadmill have been interpreted easily by simple inspection (Fig. 3A) . Each patient also had supine and standing control electrocardiograms with and without hyper-
206
of the cable-electrode
system.
ventilation. No baseline wander occurred even with deep excursions of the chest. Use of the low noise electrode-cable system permitted easy evaluation of ST segments .during exercise in all patient studies. Prior application of all ten electrodes to the patient improved the diagnostic sensitivity of the treadmill test. An example of an abnormal ST segment depression which disappeared immediately after exercise is illustrated in Fig. 3B; this example would have been missed without continuous monitoring. Two exercise tests were stopped because of ST elevation in the inferior leads (Fig. 3C 1. Not infrequently exercise was stopped because of ventricular arrhythmias (Fig. 30 1. The cable has been sturdy and reliable. No repair has been necessary. Discussion
The value of submaximal and maximal exercise testing in predicting the presence of signi& cant coronary artery disease in asymptomatic subjects and in patients with atypical chest pain has been emphasised.6J Both the sensitivity of the test which is a function of developed heart rate, and the safety of the procedure require online monitoring and recording of technically
February, 1974, Vol. 87, No. 2
Turelve-lead
patient
cable for ECG exercise testing
3, A through D. A, The left-hand panel is a control electrocardiogram (Lead Va). The right-handpanel illustrates a recording taken while the normal subject was running on the treadmill at 4.2 m.p.h. and 16 per cent grade (Bruce Stage 4). IIf,These recordings were obtained from a patient with angiographically documented significant coronary artery disease. The left-hand panel demonstrates an in-exercise positive test (Lead V6). A single ventricular premature contraction was recorded. There was rapid reversion to normal immediately postexercise (right-bond pane& C, Significant coronary artery disease was documented by coronary angiography in this patient. The Ieft panel shows a positive response at four minutes of exercise (Lead Vs). Two ectopic beats were recorded. The middle panel (Lead V,) demonstrates reversion of the pattern to normal shortly thereafter, an apparent example of the “walk-through phenomenon.” An inferior lead recording (Lead aVr) taken at the same time as the middle panel (Lead Va) showed significant ST elevation, however (right par&. The test was terminated although the patient did not develop angina pectoris. D, An example of coupled multifocal premature ventricular contractions which immediately terminated the exercise in this 24-year-old woman with the late systolic click syndrome. All recordings at a paper speed of 50 mm. per second. F&
electrocardiograms in several leads. A protocol for electrocardiographic stress testing which is applicable to all circumstances
good
single
has not been described. For the test to be useful to the busy practitioner with one technician and limited office space, the requirements are different from those of the exercise physiologist with a well-equipped and staffed laboratory. This cable is applicable to both situations. The cable has several advantages not available with commercial products. Application of all ten electrodes to the patient prior to exercise enhances the diagnostic sensitivity of the test. Any or all of the 12 leads can be recorded before, during, and after exercise as well as monitored
American
Heart Journal
by oscilloscope. It has been our practice to begin a recording just prior to stopping the treadmill so as to obtain a continuous tracing while the patient assumes a sitting or lying position. Prior application of electrodes and cable frees the physician to observe the patient while the technician obtains the tracings. If the Master two-step test is employed, the usual postexercise delay due,to reattaching electrodes and the electrocardiograph cable connection is obviated. The true heart rate response can be determined and some false negative tests can be eliminated. Abnormal ST segment shifts may disappear soon after exercise is stopped and may be missed because of even a brief delay in recording (Fig. 3B). There
207
Grab,
Campbell,
and Adolph
are advantages in multiple lead monitoring. We stopped two exercise tests because of ST elevation in the inferior leads (Fig. 30, and several were discontinued because of ventricular arrhythmias (Fig. 3D). The tracings are of good quality during strenuous exercise and even during running (Fig. 3A). Precise in-exercise heart rate becomes easy to determine from the low noise tracing. A cardiotachometer would not be triggered by false signals. A low noise electrode system without additional cable artifact simplifies identification of diagnostic ST segment changes. The cable can be applied to any type of conventional exercise test and protocol, using either a standard l%-lead system or any modification of this lead system. The cable can be adapted to any electrocardiographic recorder so that available existing electrocardiographic recording equipment can be utilized In view of general interest in extending the use of submaximal exercise testing to areas such as rehabilitation of patients following myocardial infarction, functional capacity determination, therapy evaluation, and arrhythmia diagnosis this multipurpose cable could have increasing application.
208
summary A simple electrocardiographic cable for use with exercise testing has been developed which has proved to have many advantages over commercially available cables used with standard single-channel recorders. It can be adapted easily for multiple channel equipment. REFERENCES
1. Blomqvist , C. G.: Use of exercise testing for diagnostic and functional evaluation of patients with arteriosclerotic heart disease, Circulation 44:1120, 1971. 2. Sheffield, L. T.: Personal communication. 3. Shackel. B.: Skin-drillina: A method of diminishinn galvanic’skin-potentials, Am. J. Psychol. 72:114,195< 4. Mason, R. E., and Likar, I.: A new system of multiplelead exercise electrocardiography, AM HEAR+ J. 71:196.1966. 5. Mason, R. E., Likar, I., Biern, R. O., and Ross, R. S.: Multiple-lead exercise electrocardiography: Experience in 107 normal subjects and 67 patients with angina pectoris, and comparison with coronary cinearteriography in 84 patients, Circulation 36:517,1967. 6. Sheffield, L. T., Roitman, D., and Reeves, J. T.: Submaximal exercise testing, J.S.C. Med. Assoc. 8Msuppl. 1): 18, 1969. 7. McDonough, J. R., and Bruce, R. A.: Maximal exercise testing in assessing cardiovascular function, J. S. C. Med. Assoc. BMsuppl. 025, 1969.
February, 1974, Vol. 87, No. 2