INDICATIONS FOR CARDIAC PACEMAKING Paul C. Adkins, M.D. and William S . Byers, ,rM.D. Artificial pacing of the heart, although a relatively new therapeutic tool, is by no means a new concept. In 1819, Aldini’ reported on attempts to stimulate the hearts of executed criminals by electric shock. However, it was not until 1951, that Callahan and Bigelow* were able to artificially pace the heart of an intact animal. In 1952, ZolP was successful in restarting an arrested human heart by applying an electrical stimulus across the chest wall. Furnam? in 1958, passed a catheterelectrode across the tricuspid valve into the right ventricle where he showed that a much lower voltage was required to depolarize the heart. In 1960, Chardack and associates 6, inserted the first permanent implantable pacemaker for long-term stimulation of the heart. In the past ten years great advances have been made in techniques of cardiac pacemaking. Perhaps in no other field of endeavor have the talents of physicians and electronic engineers been so successfully combined.7, 8, 9. 10 In order to discuss the indications for pacing of the heart, it is convenient to divide them into two categories-temporary and permanent. Paul C. Adkins, M.D., is a graduate of Johns Hopkins School of Medicine, Baltimore. He is presently professor of surgery at the George Washington School of Medicine, Washington, D. C. This paper was presented by Dr. Adkins at the Southeastern Surgical Conference in Washington, D. C. William S. Byers, M.D., is a graduate of the University of Maryland School of Medicine. He has been a Fellow in cardiology at George Washington University Hospital where he is presently chief resident in medicine.
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TEMPORARY CARDIAC PACING Temporary pacing of the heart generally implies that the underlying rhythm disturbance is transitory ; consequently, pacing is needed only during the acute phase of the cardiac status. In temporary pacing, the pulse generator or power source is located outside the body. The most common situation in which temporary pacing is needed is for patients with acute myocardial infarctions who develop arrhythmias in the post-infarction period. The most serious of these rhythm disturbances are asystole and third-degree heart block. However, other rhythm disturbances are potentially dangerous and may be the harbinger of a more serious or fatal arrhythmia. Our indications for temporary transvenous pacemaker insertion following an acute myocardial infarction are as follows: second.de. gree heart block, third-degree heart block, sinus arrest, frequent premature beats either unifocal or multifocal when not suppressed by drugs, sinus bradycardia, asystole, and recurrent tachyarrhythmias uncontrolled by drugs. When any of these rhythm disturbances occur in the post-infarction period, a temporary transvenous pacemaker catheter is inserted into the right ventricle for “continuous” or “demand” pacing as the situation requires. This approach is not accepted by all. Some physicians attempt to control arrhythmias and heart block solely with drug therapy. They reserve the use of pacemakers for rhythm disturbances complicated by congestive heart failure, hypotension or shock, mental aberra-
AORN Journal
tions or syncope and do not employ pacemakers on a “stand-by” basis. It is our belief that when any of these rhythm disturbances occur, the insertion of a pacemaker electrode as a prophylactic or therapeutic measure affords better control of the arrhythmia. The electrode is introduced into a peripheral vein and under fluoroscopic control is advanced through the superior vena cava, the right atrium and into the right ventricle where it is positioned to make good contact with the endocardium. In an extreme emergency when there is not time to pass a catheter in this manner, the electrode may be introduced percutaneously through the anterior chest wall or through the subxiphoid area. Another situation in which temporary pacing may be required is in the immediate postoperative period following open heart surgery. This is particularly true after valve replacement, and many surgeons routinely place epicardial electrodes during the operation. These electrodes are led out through the chest wall and attached to a stand-by external pacemaker. If arrhythmias occur in the postoperative period producing a low cardiac output, the pacemaker is used to increase the heart rate. Recently Dr. Albert Star+ and his group at the University of Oregon have utilized both atrial and ventricular electrodes in order to produce synchronized pacing in the postoperative period which they feel is more effective than simply ventricular pacing. The use of external electrodes placed on the skin of the chest wall to stimulate the heart has been abandoned. This technique had two great disadvantages; first, producing extremely uncomfortable muscle stimulation from the electrodes and second, being essentially ineffective in pacing the heart. PERMANENT CARDIAC PACING Certain conditions may cause irreversible injury to the conduction system producing various forms of chronic heart block. It is in these patients that the use of a permanent im-
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plantable pacemaker is necessary. Prior to the development of pacemakers, the majority of these people died from sudden arrhythmias induced by their slow ventricular rate and low cardiac output. But with the use of pacemakers many such individuals now lead a fairly normal life. Occasionally a permanent implantable pacemaker is required for patients with congenital heart block. Although congenital heart block may occur in the absence of other developmental anomalies, it is rather uncommon as an isolated finding. Usually it is associated with congenital abnormalities such as the tetralogy of Fallot or an interatrial septa1 defect of the ostium primum type. Infants with congenital heart block are potential candidates for implantation of a permanent pacemaker since they may die suddenly. Acquired heart block usually is due to changes in the conduction system which may be isolated or may be the result of disease processes such as myocarditis, endocarditis, uremia or sclerosis of the fibrous skeleton of the heart. As mentioned previously, myocardial infarction may cause heart block, but it rarely is permanent. The most common dysrhythrnia associated with this type heart disease is third-degree heart block. Other rhythm disturbances include second-degree heart block, sinus arrest and occasionally sinus bradycardia. There is some difference of opinion regarding the indications for artificial pacing in chronic (including congenital) forms of heart block. Some physicians do not advocate insertion of pacemakers unless there is a history of at least one Adams-Stokes attack. Adams-Stokes attack or Adams-Stokes syndrome refers to a sudden episode of syncope with or without convulsions. This is most frequently caused by failure of ventricular contraction in third-degree heart block due either to ventricular asystole, ventricular fib-
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Figure 1 : Top: Electrocardiogram showing third-degree heart black in a patient with Adams-Stokes attacks. Bottom: Electrocardiogram after insertion of a fixed-rate pacemaker.
rillation or a combination of both. (Figure breathing becomes normal and the patient 1) Adams-Stokes attacks also may occur dur- regains consciousness. Non-fatal attacks rareing the transition from a normal sinus rhythm ly exceed 60 seconds. Adams-Stokes attacks have been reported in to second-degree or third-degree heart block when there is a prolonged delay (five to ten 35 to 70 per cent of cases of third-degree seconds) in establishing an idioventricular heart block studied in various series.12*l8 rhythm. Occasionally, a very slow sinus The duration of life following the onset of bradycardia (less than 20 per minute) may complete heart block or Adams-Stokes atprecipitate an Adams-Stokes attack. The syn- tacks is difficult to determine because the cope is due to cerebral ischemia caused by data is still inadequate and inconsistent. ineffective ventricular output. Obviously, syn- It is well established that complete heart cope occurs more readily in the standing or block, particularly when complicated by Adams-Stokes attacks carries a grave progsitting positions than during recumbency. In an Adams-Stokes attack, the patient sud- nosis. Prior to the use of permanent pacedenly becomes pale, loses consciousness and makers, 100 patients with Adams-Stokes atcollapses. If the attacks are protracted (15 tacks were studied at the Mt. Sinai H0spita1.l~ to 20 seconds or longer), cyanosis ensues, They were treated with drugs, external pacthe breathing becomes stertorous and a gen- ing and defibrillation during acute attacks. eralized convulsive seizure may occur. With Of the 100 patients, 50 were dead within one the return of effective ventricular contraction year, 34 dying within six months, 24 were and increased cardiac output, the seizure known to be alive and 20 were lost to folstops, the pulse returns, cyanosis disappears, low-up. Not included in the numerous statis-
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tical studies are patients with asymptomatic as the bundle of His. In patients with high third-degree heart block and patients in whom ventricular-septa1defects, the bundle lies quite the first Adams-Stokes attack was fatal. Vari- close to the inferior medial margin of the deants of the Adams-Stokes syndrome may oc- fect and usually is located closer to the left cur during brief periods of asystole (two to side of the ventricular septum than to the five seconds) manifested by fleeting weakness, right. Consequently, in repair of ventricular dizziness, or faintness, but without actual loss septa1 defects, it is imperative to place the of consciousness. sutures so that they wiII not involve the Considering the high incidence of Adams- bundle of His. Most surgeons, when working Stokes attacks associated with third-degree near this area, place the sutures parallel to heart block and the fact that the first attack the direction of the bundle and closer to the may result in death from ventricular fibrilla- right ventricular surface than the left. Altion or asystole, we believe that any patient though in the earlier days of open heart surwith this rhythm disturbance is a candidate gery, heart block was a frequent occurrence for a permanent implantable pacemaker un- following the repair of ventricular-septa1 defects, most surgeons now are sufficiently acless the ventricular rate is unusually rapid. Some patients with third-degree heart block quainted with the anatomy to be able to avoid manifest signs of congestive heart failure. the bundle. In addition, many will keep the This is due to a low cardiac output associated heart beating during repair of this area in with the slow ventricular rate. Such patients order to ascertain whether there has been inmay never have had an Adams-Stokes attack; jury to the bundle. As a result, the incinevertheless, they will receive a double bene- dence of heart block in most series of repairs fit from the insertion of a permanent pace- of ventricular-septa1 defects is now less than maker. First there is safety from sudden death two per cent. Prior to the development of permanently during an Adams-Stokes attack and second, the symptoms of congestive failure frequently implantable pacemakers, if heart block ocwill disappear once the ventricular rate is in- curred at the time of operation, the mortality rate was 30 per cent or more. At the present creased by the pacemaker. time, if there is evidence of heart block or concern about it at the time of surgery, epiPOSTOPERATIVE HEART BLOCK The anatomic location of the conduction cardial electrode wires are placed and brought bundle in the heart renders it susceptible to out through the chest wall. A pacemaker may injury during operations to repair cardiac be utilized if heart block occurs. Not infreabnormalities. The atrioventricular (A-V) quently the block will be temporary and will node is located in the floor of the right atri- revert to a normal sinus rhythm in a period um. It is in the septum between the medial of several days to a week. If, however, the leaflet of the tricuspid valve and the point of heart block continues for three weeks, it is entry of the coronary sinus into the right advisable to insert a permanent pacemaker. atrium. Consequently, in the repair of a large Injury to the conduction system may occur atrial-septa1 defect, particularly of the ostium during aortic valve insertion due to the close primurn type, and in surgical replacement of proximity of the sino-atrial (S-A) node to the tricuspid valve, the close proximity of this the aortic root. Here again, temporary epinode to the point of placement of sutures cardial electrode wires are placed and if the makes heart block a hazard. The conduction heart block persists for a period of three bundle continues into the ventricular septum weeks, a permanent pacemaker is inserted.
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SELECTION OF PACEMAKER There are three types of permanently implantable pacemakers which are currently available. These are the fixed-rate pacemaker, the variable-rate or synchronized pacemaker, and the demand pacemaker. Although there is not unanimous agreement about the selection of each of these types for individual cases, each would appear to have certain advantages and disadvantages.
I. FIXED-RATE PACEMAKER This type of pacemaker sends an impulse through the electrode for stimulation of the heart at a fixed rate, generally set between 60 and 70 per minute. The rate of the pulse generator is pre-set at the factory, but in one unit, the Medtronic, the rate may be changed by inserting a Keith needle into a slot in the side of the pacemaker and turning a screw. This adjustment can be made even after the pacemaker has been implanted subcutaneously. In addition, the amount of current (milliamps) can be varied in order to achieve the optimal level of electrical stimulation of the heart by inserting a Keith needle into a separate slot in the pacemaker. In patients with complete heart block, a fixed-rate pacemaker will stimulate the heart to beat at a constant rate; consequently, the cardiac output or minute volume is essentially fixed. The majority of these patients are 70 years of age or older and lead a sedentary life. They rarely, if ever, engage in the type of activity which might necessitate an increased demand on the heart and an increased cardiac output. In this group of patients, since the level of activity remains about the same, a fixed-rate pacemaker is entirely satisfactory. The electronics of this type of pacemaker are less complicated than those of a variable rate or demand pacemaker and are less liable to fail. One disadvantage of the fixed-rate pacemaker is that a stimulus might fall in the vulnerable period of the cardiac cycle with the possibility of causing ventricular fibrillation. (To
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our knowledge, this theoretical possibility has not been a major problem in the clinical use of this pacemaker.) 11. SYNCHRONIZED OR VARIABLE-RATE PACEMAKER This type of pacemaker consists of an electrode attached to the atrium for conduction of atrial impulses (the P waves) to the pulse generator which in turn sends an electrical stimulus to the ventricle causing ventricular depolarization. Since patients with third degree heart block have an interference in the conduction mechanism, the ventricle beats at a slow, fixed rate unrelated to the atrial rate. The synchronized pacemaker enables the ventricle to beat in response to atrial contractions. Consequently, in persons in whom a variable amount of activity might be expected and because normally with increased activity there is an increase in heart rate, the synchronized pacemaker provides a variable ventricular rate synchronous with the atrial rate. Also, a theoretical advantage of the synchronized pacemaker is that the mechanical efficiency of the heart is improved when the atria are beating synchronously with the ventricles. In such a pacemaker a number of “builtin” safety features are necessary to make allowances for rapid atrial rates or failure of the atria to stimulate the ventricles. This pulse generator has a built-in mechanism to prevent tachycardias. If the atrial rate exceeds 110, a two-to-one block is set up reducing the ventricular rate to half the atrial rate. Thus, even with extreme atrial rates, the rate of ventricular stimulation never will exceed 110 per minute. In addition, if the electrical impulse of the atrium (the P wave) is insufficient to trigger the pulse generator, the rate of ventricular stimulation reverts to a fixed rate. Use of a synchronized pacemaker requires thoracotomy for placement of two electrode leads, one on the atrium and the other on the ventricle. (Figure 2) It is ap-
AORN Journal
Figure 2: Chest roentgenogram showing synchronized pacemaker in place.
parent that the electronics of this type of pulse generator are more complicated than those of the fixed-rate pacemaker.
111. DEMAND (STAND-BY) PACEMAKER The demand pacemaker is designed for the patient who has intermittent heart block while at other periods has a normal sinus rhythm. In addition, the demand pacemaker avoids competitive rhythm and eliminates the potential danger of pacer pulses falling during the heart’s vulnerable period. This may be accomplished in two ways. The first, is to have
September 1968
a blocking circuit in the pacemaker which
prevents the artificial stimulus if a spontaneous ventricular depolarization occurs. A theoretical disadvantage is that the pulse blocking circuit may be activated by external stimuli so that the pacemaker will fail to send impulses to the ventricle. Another method is to have the pacemaker issue an impulse which is superimposed upon the QRS complex. When the pacemaker impulse occurs during the QRS,it will not depolarize the ventricles. If, however, following a QRS complex and a measured duration of time, spon-
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taneous electrical depolarization of the heart does not occur, then the pacemaker sends an electrical stimulus to the ventricles producing ventricular systole. Thus, the demand pacemaker will pulse at a fixed rate if no spontaneous depolarizations occur. ELECTRODE PLACEMENT There are three methods of implanting electrodes for stimulation of the heart. The first is the transthoracic passage of a needle electrode into the heart. This procedure is used only in extreme emergencies. The second is the myocardial electrode which is implanted directly into the ventricular myocardium by thoracotomy. A number of variations in the method of implantation are used including a standard antero-lateral thoracotomy, simple resection of one of the costal cartilages to gain access to the myocardium or insertion of the electrode by removal of the xiphoid and entry into the pericardial sac through the subxiphoid approach. The disadvantage of the myocardial electrode is that it does require a formal operative procedure for implantation. Consequently, in an age group where concomitant disease processes such as coronary artery disease, emphysema and many other manifestations of aging are present, the risk of such a formidable operative procedure is significant. In order to avoid the necessity of an operative procedure for insertion of the myocardial electrodes, a method of transvenous passage of the electrode has been developed. Using this method, the electrode is inserted into the superior vena cava via the external jugular vein, and less commonly by the internal jugular or the cephalic vein. Under fluoroscopic control, the electrode is passed through the right atrium, the tricuspid valve and into the right ventricle where the tip of the electrode is positioned at the apex of the right ventricle. The catheter-electrode is held in position by the trabeculations in the right Ventricular cavity. (Figure 3) Good contact
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generally is obtained between the endocardium and the tip of the electrode. The electrode then can be connected by a subcutaneous tunnel with the pulse generator under local anesthesia. In Medtronic units, the electrode is bipolar, whereas in the Cordis, the electrode is unipolar, the ground plate of the pulse generator being the positive electrode. PROCEDURE Once it has been determined that a patient is a candidate for a permanent implantable pacemaker, a temporary electrode is inserted transvenously into the right ventricle and attached to an external pulse generator. The patient can be paced in this manner until the time of insertion of the permanent pacemaker. This procedure usually is done in the cardiac catheterization laboratory where the electrode for the permanent pacemaker is inserted under fluoroscopic control and is attached to a temporary pulse generator to determine whether it will capture. Next a subcutaneous pocket is created in the pectoral region and connected to the site of insertion of the electrode. The electrode is then passed through the subcutaneous tunnel to this pocket and connected to the pulse generator. The wounds are closed and the patient is monitored to verify continued capture. The temporary external pacemaker is left in place 48 hours as a “standby” in case the permanent electrode catheter fails to capture the heart beat. Following this period of time, the temporary electrode is removed and the patient is ambulated. Patients are instructed to check their pulse rate twice daily and in the case of the fixed-rate or demand pacemakers, to report any variation in the rate. In the currently available types of pulse generators, the battery life is approximately 24-30months. Consequently, all patients are electively readmitted for change of pulse generator at about 26-28 months. This replacement can be accomplished under local anesthesia without reinserting a new electrode.
AORN Journal
Figure 3: Chest roentgenogram showing fized-rate pacemaker. Pulse generator is in right pectoral region and electrode tip is right in ventricle.
REFERENCES 1. Aldini, G., General Views on the Application of Galvanism to Medical Purposes: Principally in Cases of Suspended Animation, J. Callow, London, 1819. 2. Callahan, J. C. and Bigelow, W. G., “An Artificial Pacemaker for Standstill of the Heart,” Ann. Surg., 134: 8, 1951. 3. Zoll, P. M., “Resuscitation of the Heart in Ventricular Standstill by External Electric Stimulation,” New Eng. J . Med., 247: 68, 1952. 4. Funnan, S. and Robinson, G., “The Use of an Intracardiac Pacemaker in Correction of Total Heart Block,” Surg. Forum, 9: 745, 1958.
Septemher 1968
5. Chardack, W. M., Gage, A. A. and Greatbatch, W. A., “Transistorized Self-contained Implantable Pacemaker for the Long Term Correction of Complete Heart Block,” Surgery, 48: 643, 1960. 6. Chardack, W. M., Gage, A. A. and Greatbatch, W. A., “Correction of Complete Heart Block by SelfContained and Subcutaneously Implanted Pacemaker,” I. Thorac. Surg., 42: 814, 1%1. 7. Lillehi, C. W., Levy, M. J., Bonnabeau, R. C., Long, D. M. and Sellers, R. D., “Direct Wire Electrical Stimulation for Acute Post-Surgical and PostInfarction Complete Heart Block,” Ann. N . Y . Acad. sci., 3 : 938, 1964.
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8. 2011, P. M. and Linenthal, A. J., “Long Term
Electrical Pacemakers for Stokes-Adam Disease,” Circulation. 22: 341. 1%0. 9. Center, S., Nathan, D., Chang-Yu, Wu, Samet, P., and Keuer’ w’9 “The Implantable Synchronous Pacer in the Treatment of Complete Heart Block,” 1. Thorac. Cardw. Surg., %: 744, 1963. 10. Furman, S., Escher, D. J. W., Schwedel, J. B. and Solomon, N., “Transvenous Pacing,” Am. Heart J., 71: 408, 1%6.
11. Friesen, W. G., Woodson, R. D., Ames, A. W., Herr, R. H., Starr, A. and Kassebaum, D. G., “A Hemodynamic Comparison of Atrial and Ventricular Pacing in Postoperative Cardiac Surgical Patients,” J . Thorack. and ,-ardiovasc. surg., In press. 12. Friedberg, C. K., Diseases of the Heart, W. B. Sanders Co., Philadelphia and London, 1966. 13. Friedberg, C. K., Donoso, E. and Stein, W. G., “Nonsurgical Acquired Heart Block,” Ann. N . Y . Acad. Sci., 3 : 835, 1964. 14. Ibid.
CHARLES B. MOORE AWARD Ruth H . Bramhall, R.N. The Charles B. Moore Award will again, this year, pay $300.00 for an AORN member to attend the annual Congress. Local AORN chapters have been alerted to select a candidate “who has made an outstanding contribution toward improving nursing care in the operating room during the past five years.” I n June each chapter received a letter and forms to help select a winner for the Award. If your president has not brought it to your attention, please ask her about it. As the chairman of the committee, I would like to suggest that all chapters participate each year. Appoint a committee, a couple of people, or nominate an individual from your chapter. Have a member write up the form and submit it to the national committee. To be eligible for the Award, a candidate must be a member of AORN, actively engaged in OR nursing. She may be a chapter member or a member-at-large. She must be available to attend the Congress in Cincinnati. Nominations must include a biographical sketch and resume of the candidate’s contribution to OR nursing. You, as chapter members, start things rolling. We, as a committee, cannot work until you give us your recommendation. So, please, if you have not sent in your forms yet, get them on their way before October 24th, to Mrs. Ruth H. Bramhall, Rt. 4, Box 4582A, Gig Harbor, Washington 98335. The resumes of qualified nominees are sent to the chapter presidents after deletion of all identifying information. Chapter members have to choose the candidate they believe most qualified. Sister Mary Cyprian, R.S.M., ORS, St. Mary’s Memorial Hospital, Knoxville, Tennessee, was the 1968 Award winner. She was directly responsible for organizing and operating the first formal training program for OR technicians in the Knoxville area. She is continually looking for opportunities to further the education of her staff by sending them to workshops, institutes, and conventions. Sister is having an article published in the October, 1968 issue of the Journal. 1967’s winner was Mrs. Della Ruppert, who worked in the ten-room operating suite of University Hospital, Iowa. On the theory that communication brings about good staff relations, she set up a problem-solving committee of elected nurse representatives to discuss new ideas, some of which were successfully implemented in the OR suite. Mrs. Ruppert also designed a drape for abdominal-perineal resections, and’ with another nurse, she designed a “needle finder” made out of a magnet. She had an article published in the June, 1968 issue of the Journal. The award winners in the past have been very deserving, but I am asking for more to be submitted. As chapters you are to receive the resumes of ten nominees. Sometimes we do not get this many. So many of the nominees a r e supervisors, how about the general duty OR nurse, the right hand of so many supervisors . . . the organizer, helper, stabilizer, circulator and scrubber in the OR. Give it some good sound thought, then fill out the forms and send them in. The deadlines are fairly close, but workable. Thank you for your cooperation.
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