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A preliminary evaluation of the effects of electrical pulp testers on dogs with artificial pacemakers
A preliminary evaluation of the effects of electrical pulp testers on dogs with artificial pacemakers
LeGrand H. Woolley, DD S, M S James Woodworth, M D Jeri L. Dobbs, BS, P o rtlan d, O re
T h e use of artificial p acem akers in p atien ts w ith heart disease has created a special typ e of p atien t m an ag em en t p ro blem fo r dentists. T h e ap p licatio n of electrical cu rren ts to such patients by th e use of pulp testers, desensitizing eq u ip m ent, electro su rgical instrum ents and so fo rth , as w ell as cu rren t leaks from o th e r electrical eq u ip m ent, can interfere with p ace m a ke r fu n c tio n and may co n stitute a ser ious health hazard. D entists should be aw a re of the effects of th e ap p licatio n of electrical cu rren t to th eir patients.
An electrical current of 0.2 ma (200 microam peres) applied directly to a healthy heart can in duce ventricular fibrillation.1 Because of the pro tective effects of its investing tissues, much greater currents (100 to 500 ma, 60 cycles per second, alternating current) are required to pro duce fibrillation in the heart in situ. Line currents are of sufficient magnitude under some circum stances and have been known to cause deaths in children. Currents of this strength are, of course, not applied to patients during dental procedures, and it is very unlikely that equipment such as pulp testers constitutes a hazard to healthy pa tients. (Guidelines regarding safety procedures for all electrical equipment in the dental office have been published.2) Individuals with artificial pacemakers present a special type of problem in patient management. Inasmuch as they rely on artificial cardiac stim ulation for pacing the heart, it is extremely im portant that the dentist refrain from performing any procedure that would interfere with pace maker function. Currents much less than those required to induce ventricular fibrillation will disrupt the function of some artificial pacemak ers. In addition, the presence of the pacemaker and its leads within the body bypasses some of the tissues that would ordinarily insulate the heart. Thus, electrical currents o f low magni tude, when applied to the body in the vicinity of the implanted pacemaker, could theoretically disrupt its function. If the disruption of function was sufficient to produce hypoxia of the myo cardium, ventricular fibrillation could ensue even though the interfering electrical current JADA, Vol. 89, November 1974 ■ 1099
T a b le ■ R esu lts o f tests. In s tru m e n t S . S . W h ite P u lp T e s t e r M o d el 2A R it t e r S e n s itr o n M odel A B u r to n V it a lo m e t e r M o d e l 205 M B P e lto n a n d C r a n e V it a p u lp M o d e l KO
M e t e r r e a d in g s a n d r e s u lts , c u r r e n t a p p lie d a s d ir e c t e d
M e te r r e a d in g s a n d r e s u lts , c u r r e n t a p p lie d o v e r p a c e m a k e r
2 0 f f ia , in t e r fe r e n c e
5 /fx a ,
M a x im u m , n o in t e r fe r e n c e
No. 8, setting interference
M a x im u m , n o in t e r fe r e n c e
No. 7, setting interference
M a x im u m , n o in t e r fe r e n c e
No. 8, setting interference
was not sufficient by itself. Cerebral hypoxia leading to syncope could also occur, and this might be misinterpreted by the dentist. Several warnings of possible interference with artificial cardiac pacemakers by electrical equip ment have recently appeared in the dental liter ature.3,4 However, no definitive answers have been given to two questions. Will the use of den tal equipment which applies a current directly to the patient (pulp testers, desensitizers, electrosurgical equipment) interfere with artificial pace m aker function in situ? Can electrical leaks from dental power equipment (power chairs, units, radiographic equipment) interfere with artificial pacemaker function in situ? The answers to these questions are important to dentists for obvious reasons. If the answers are yes, then it becomes important to determine the degree of the health hazard such interference constitutes. Because answers to the questions were not found in the dental literature, we decided to conduct a pilot experiment to give provisional answers and to determine possible experimental models for fur ther testing.
Experimental model A n unanesthetized, 65-lb black Labrador re triever (registered by the American Kennel Club) was used in this procedure. Artificial complete heart block had previously been established.5 A ventricular tracking standby pacemaker* and endocardial lead* had been implanted 19 months before the experiment. An electrocardiographt was used to monitor heart activity continuously. Four instruments were tested: S. S. White Pulp Tester no. 2-A,$ using line current and de livering up to 0.1 ma; Ritter Sensitron model A,§ using line current and delivering up to 0.1 ma; Burton Vitalometer model 205 MB ,11 using line current; and Pelton & Crane Vitapulp model KO,** using a 7-v battery power source. The electrical characteristics of the Vitalometer and Vitapulp instruments were recently described in the literature.6 1100 ■ JADA, Vol. 89, November 1974
interference
Testing procedures and results Each pulp tester was applied as recommended by the manufacturer and also to the skin overlying the implanted pacemaker. Recordings of settings were made for each test and correlated with heart action as shown by the electrocardio graph. The results are shown in the Table. When used as directed, only the S. S. White instrum ent caused interference and modified the normal pacemaker function at settings producing 20/xa or more. When applied to the skin overlying the implanted pacemaker, all instruments caused interference and modified the normal pacemaker function with a current to as low as 5/ta. Of particular interest was an incident that oc curred while the Sensitron was being used. One of us (L.H.W .) inadvertently touched the dog with one hand while holding the Sensitron in the other. Although the instrument was turned off, a current leak was registered on the electrocar diograph. We decided to test this leak although we could not measure its magnitude and found that it was sufficient to cause interference and modify normal pacemaker function if a person’s hand was placed in the vicinity of the pacemaker. Obvious leaks were not apparent in the other instruments tested, and so no further evaluation of this potential hazard was carried out. It was determined, however, that future experimen tation should include this important area for evaluation.
Discussion It is evident that, under the conditions of this experiment, currents of the magnitude of 5fia to 20/xa arc sufficient to modify normal pace maker function. Currents of this magnitude are commonly applied to patients by dentists through the use of pulp testers, electrodesensitizing equipment, and electrosurgical instruments. The answer to the question, “ Will the use of dental equipment which applies an electrical current
I
Electrocardiograph tracing showing
interference with
normal pacemaker function characterized by the loss of one beat. When stimulation continued, pacemaker shifted into fixed rate.
5 pa -4 ---------------------------------------------------------------------------------
d u r a t i o n of the s t i m u l u s directly to the patient interfere with artificial pacemakers in situ?” seems to be yes. It cer tainly interfered with the pacemaker in our dog. Furthermore, the answer to the question con cerning electrical leaks also seems to be yes. Al though we did not test dental chairs, units, and radiographic equipment, the leak present in the Sensitron was sufficient to modify normal func tion of the pacemaker. It is possible that an elec trical leak such as the one described constitutes a greater hazard to patients than directly applied currents from pulp testers since the leak may be entirely unsuspected by the dentist. If the den tist should touch the patient (who is in turn grounded through the dental chair) in the area of the implanted pacemaker, interference might occur. Starmer and co-workers1 pointed out some of the hazards of the use of electrical equipment in hospitals. These hazards are especially distinct when two pieces of electrical equipment, such as an electrocardiograph attached to a patient in a power hospital bed, are used simultaneously. If the patient touches the metal frame of the bed that is grounded through its legs or through an attendant, the patient can be introduced into the power-line ground circuit. Situations compar able to this exist in the average dental office; the patient sits in a powered dental chair while the dentist might use a leaky electrically powered instrument in treatment. This pilot experiment simply confirms previ ous suspicions about the possibility of interfer ence with artificial pacemakers. It does not an swer those questions dealing with the extent of the hazards that might be created by such inter ference. Such hazards depend on other factors such as the condition of the patient’s heart and the type of pacemaker used. The pacemaker used in this experiment is designed in such a way that
its normal function is modified into a fixed-rate pace when electrical interferences are detected (illustration). Some other types of pacemakers might be shut off for the duration of the interfer ing stimulus. Obviously, the latter type of pace maker could constitute a greater hazard. Future work in this field is needed to determine the ex tent of dental office hazards, not only for pa tients with pacemakers but for other patients with cardiac conditions as well.
Dr. Woolley is associate professor of pathology, University of Oregon Dental School, and associate professor of dentistry, University of Oregon Medical School. His address is University of Oregon Dental School, 611 SW Campus Dr, Portland, 97201. Dr. Woodworth is a clinical associate in the department of med icine, University of Oregon Dental School, and clinical instruc tor in medicine and associate professor of dentistry, University of Oregon Medical School. Mr. Dobbs is assistant professor of cardiopulmonary surgery and director, cardiac surgical research laboratory, University of Oregon Medical School. ‘ Model 8114 pacemaker and model 8204 endocardial lead, Starr-Edwards, Edwards Laboratories, Santa Ana, Calif 92705. tModel EK4, Burdick Corp., Milton, Wis 53563. tS. S. White Div., Pennwalt Corp., Philadelphia, 19102. §Ritter Co., Rochester, NY 14611. HBurton Div., Cavitron Corp., Van Nuys, Calif 91401. “ Pelton & Crane Co., Charlotte, NC 28203. 1. Starmer, C.F.; McIntosh, H.D.; and Whalen, R.E. Electrical hazards and cardiovascular function. New Engl J Med 284:181 Jan 28, 1971. 2. Council on Dental Materials and Devices, Schram, P. J. Guidelines for electrical safety in the dental office. JADA 85:365 Aug 1972. 3. Letters to the editor. Clarke, A.M., and others. Danger to pa tients. JADA 85:232 Aug 1972. 4. Council on Dental Materials and Devices. Possible electro magnetic interference with cardiac pacemakers from dental in duction casting machines and electrosurgical devices. JADA 86: 426 Feb 1973. 5. Stiner, C., and Kovalik, A.T.W. A simple technique for pro duction of chronic complete heart block in dogs. J Appl Physiol 25:631 No. 5, 1968. 6. Civjan, S.; Barone, J.J.; and Vaccaro, G.J. Electric pulp vi tality testers. J Dent Res 52:120 Jan-Feb 1973.
Woolley—Woodworth— Dobbs: PULP TESTERS AND ARTIFICIAL PACEMAKERS ■ 1101
LeGrand H. Woolley, DD S, M S James Woodworth, M D Jeri L. Dobbs, BS, P o rtlan d, O re
T h e use of artificial p acem akers in p atien ts w ith heart disease has created a special typ e of p atien t m an ag em en t p ro blem fo r dentists. T h e ap p licatio n of electrical cu rren ts to such patients by th e use of pulp testers, desensitizing eq u ip m ent, electro su rgical instrum ents and so fo rth , as w ell as cu rren t leaks from o th e r electrical eq u ip m ent, can interfere with p ace m a ke r fu n c tio n and may co n stitute a ser ious health hazard. D entists should be aw a re of the effects of th e ap p licatio n of electrical cu rren t to th eir patients.
An electrical current of 0.2 ma (200 microam peres) applied directly to a healthy heart can in duce ventricular fibrillation.1 Because of the pro tective effects of its investing tissues, much greater currents (100 to 500 ma, 60 cycles per second, alternating current) are required to pro duce fibrillation in the heart in situ. Line currents are of sufficient magnitude under some circum stances and have been known to cause deaths in children. Currents of this strength are, of course, not applied to patients during dental procedures, and it is very unlikely that equipment such as pulp testers constitutes a hazard to healthy pa tients. (Guidelines regarding safety procedures for all electrical equipment in the dental office have been published.2) Individuals with artificial pacemakers present a special type of problem in patient management. Inasmuch as they rely on artificial cardiac stim ulation for pacing the heart, it is extremely im portant that the dentist refrain from performing any procedure that would interfere with pace maker function. Currents much less than those required to induce ventricular fibrillation will disrupt the function of some artificial pacemak ers. In addition, the presence of the pacemaker and its leads within the body bypasses some of the tissues that would ordinarily insulate the heart. Thus, electrical currents o f low magni tude, when applied to the body in the vicinity of the implanted pacemaker, could theoretically disrupt its function. If the disruption of function was sufficient to produce hypoxia of the myo cardium, ventricular fibrillation could ensue even though the interfering electrical current JADA, Vol. 89, November 1974 ■ 1099
T a b le ■ R esu lts o f tests. In s tru m e n t S . S . W h ite P u lp T e s t e r M o d el 2A R it t e r S e n s itr o n M odel A B u r to n V it a lo m e t e r M o d e l 205 M B P e lto n a n d C r a n e V it a p u lp M o d e l KO
M e t e r r e a d in g s a n d r e s u lts , c u r r e n t a p p lie d a s d ir e c t e d
M e te r r e a d in g s a n d r e s u lts , c u r r e n t a p p lie d o v e r p a c e m a k e r
2 0 f f ia , in t e r fe r e n c e
5 /fx a ,
M a x im u m , n o in t e r fe r e n c e
No. 8, setting interference
M a x im u m , n o in t e r fe r e n c e
No. 7, setting interference
M a x im u m , n o in t e r fe r e n c e
No. 8, setting interference
was not sufficient by itself. Cerebral hypoxia leading to syncope could also occur, and this might be misinterpreted by the dentist. Several warnings of possible interference with artificial cardiac pacemakers by electrical equip ment have recently appeared in the dental liter ature.3,4 However, no definitive answers have been given to two questions. Will the use of den tal equipment which applies a current directly to the patient (pulp testers, desensitizers, electrosurgical equipment) interfere with artificial pace m aker function in situ? Can electrical leaks from dental power equipment (power chairs, units, radiographic equipment) interfere with artificial pacemaker function in situ? The answers to these questions are important to dentists for obvious reasons. If the answers are yes, then it becomes important to determine the degree of the health hazard such interference constitutes. Because answers to the questions were not found in the dental literature, we decided to conduct a pilot experiment to give provisional answers and to determine possible experimental models for fur ther testing.
Experimental model A n unanesthetized, 65-lb black Labrador re triever (registered by the American Kennel Club) was used in this procedure. Artificial complete heart block had previously been established.5 A ventricular tracking standby pacemaker* and endocardial lead* had been implanted 19 months before the experiment. An electrocardiographt was used to monitor heart activity continuously. Four instruments were tested: S. S. White Pulp Tester no. 2-A,$ using line current and de livering up to 0.1 ma; Ritter Sensitron model A,§ using line current and delivering up to 0.1 ma; Burton Vitalometer model 205 MB ,11 using line current; and Pelton & Crane Vitapulp model KO,** using a 7-v battery power source. The electrical characteristics of the Vitalometer and Vitapulp instruments were recently described in the literature.6 1100 ■ JADA, Vol. 89, November 1974
interference
Testing procedures and results Each pulp tester was applied as recommended by the manufacturer and also to the skin overlying the implanted pacemaker. Recordings of settings were made for each test and correlated with heart action as shown by the electrocardio graph. The results are shown in the Table. When used as directed, only the S. S. White instrum ent caused interference and modified the normal pacemaker function at settings producing 20/xa or more. When applied to the skin overlying the implanted pacemaker, all instruments caused interference and modified the normal pacemaker function with a current to as low as 5/ta. Of particular interest was an incident that oc curred while the Sensitron was being used. One of us (L.H.W .) inadvertently touched the dog with one hand while holding the Sensitron in the other. Although the instrument was turned off, a current leak was registered on the electrocar diograph. We decided to test this leak although we could not measure its magnitude and found that it was sufficient to cause interference and modify normal pacemaker function if a person’s hand was placed in the vicinity of the pacemaker. Obvious leaks were not apparent in the other instruments tested, and so no further evaluation of this potential hazard was carried out. It was determined, however, that future experimen tation should include this important area for evaluation.
Discussion It is evident that, under the conditions of this experiment, currents of the magnitude of 5fia to 20/xa arc sufficient to modify normal pace maker function. Currents of this magnitude are commonly applied to patients by dentists through the use of pulp testers, electrodesensitizing equipment, and electrosurgical instruments. The answer to the question, “ Will the use of dental equipment which applies an electrical current
I
Electrocardiograph tracing showing
interference with
normal pacemaker function characterized by the loss of one beat. When stimulation continued, pacemaker shifted into fixed rate.
5 pa -4 ---------------------------------------------------------------------------------
d u r a t i o n of the s t i m u l u s directly to the patient interfere with artificial pacemakers in situ?” seems to be yes. It cer tainly interfered with the pacemaker in our dog. Furthermore, the answer to the question con cerning electrical leaks also seems to be yes. Al though we did not test dental chairs, units, and radiographic equipment, the leak present in the Sensitron was sufficient to modify normal func tion of the pacemaker. It is possible that an elec trical leak such as the one described constitutes a greater hazard to patients than directly applied currents from pulp testers since the leak may be entirely unsuspected by the dentist. If the den tist should touch the patient (who is in turn grounded through the dental chair) in the area of the implanted pacemaker, interference might occur. Starmer and co-workers1 pointed out some of the hazards of the use of electrical equipment in hospitals. These hazards are especially distinct when two pieces of electrical equipment, such as an electrocardiograph attached to a patient in a power hospital bed, are used simultaneously. If the patient touches the metal frame of the bed that is grounded through its legs or through an attendant, the patient can be introduced into the power-line ground circuit. Situations compar able to this exist in the average dental office; the patient sits in a powered dental chair while the dentist might use a leaky electrically powered instrument in treatment. This pilot experiment simply confirms previ ous suspicions about the possibility of interfer ence with artificial pacemakers. It does not an swer those questions dealing with the extent of the hazards that might be created by such inter ference. Such hazards depend on other factors such as the condition of the patient’s heart and the type of pacemaker used. The pacemaker used in this experiment is designed in such a way that
its normal function is modified into a fixed-rate pace when electrical interferences are detected (illustration). Some other types of pacemakers might be shut off for the duration of the interfer ing stimulus. Obviously, the latter type of pace maker could constitute a greater hazard. Future work in this field is needed to determine the ex tent of dental office hazards, not only for pa tients with pacemakers but for other patients with cardiac conditions as well.
Dr. Woolley is associate professor of pathology, University of Oregon Dental School, and associate professor of dentistry, University of Oregon Medical School. His address is University of Oregon Dental School, 611 SW Campus Dr, Portland, 97201. Dr. Woodworth is a clinical associate in the department of med icine, University of Oregon Dental School, and clinical instruc tor in medicine and associate professor of dentistry, University of Oregon Medical School. Mr. Dobbs is assistant professor of cardiopulmonary surgery and director, cardiac surgical research laboratory, University of Oregon Medical School. ‘ Model 8114 pacemaker and model 8204 endocardial lead, Starr-Edwards, Edwards Laboratories, Santa Ana, Calif 92705. tModel EK4, Burdick Corp., Milton, Wis 53563. tS. S. White Div., Pennwalt Corp., Philadelphia, 19102. §Ritter Co., Rochester, NY 14611. HBurton Div., Cavitron Corp., Van Nuys, Calif 91401. “ Pelton & Crane Co., Charlotte, NC 28203. 1. Starmer, C.F.; McIntosh, H.D.; and Whalen, R.E. Electrical hazards and cardiovascular function. New Engl J Med 284:181 Jan 28, 1971. 2. Council on Dental Materials and Devices, Schram, P. J. Guidelines for electrical safety in the dental office. JADA 85:365 Aug 1972. 3. Letters to the editor. Clarke, A.M., and others. Danger to pa tients. JADA 85:232 Aug 1972. 4. Council on Dental Materials and Devices. Possible electro magnetic interference with cardiac pacemakers from dental in duction casting machines and electrosurgical devices. JADA 86: 426 Feb 1973. 5. Stiner, C., and Kovalik, A.T.W. A simple technique for pro duction of chronic complete heart block in dogs. J Appl Physiol 25:631 No. 5, 1968. 6. Civjan, S.; Barone, J.J.; and Vaccaro, G.J. Electric pulp vi tality testers. J Dent Res 52:120 Jan-Feb 1973.
Woolley—Woodworth— Dobbs: PULP TESTERS AND ARTIFICIAL PACEMAKERS ■ 1101