Four-Year Experience with an Implanted '

PAUL M. ZOLL, M.D., HOWARD A. FRANK, M.D., ARTHUR J. LINENTHAL, M.D.

From the Aledical and Surgical Research Departnments, Bethi Israel Hospital, and the Departments of Medicine and Surgery, Harvard Aledical School Boston, Mlassachuisetts

LONG-TERM cardiac stimulation with im- rise of threshold except in association witlh plantable pacemakers and myocardial elec- sepsis at the implantation site in 3 early trodes has become established, since the cases. Tests in 5 patients during replace- early reports by ourselves 25 and others,=' 12 ment of early pacemakers 1 to 3 years after as a most effective means of preventing re- implantation have shoxvn thresholds of 1.5 current Stokes-Adams attacks and improv- to 4 volts and 1.3 to 6 milliamperes. ing in patients with Electrode Wires. Implanted electrodes block. The purpose of this paper is to sum- and wires are subjected several million marize our experience with the 77 patients times each month to mechanical stresses whom we have treated in this wvay since resulting from motion of heart, diaphragm, July 1960. and thoracic and abdominal walls. Break- age of the electrodes or of the connecting Pacemaker-Electrode System wires is a significant possibility in every Stimulus Threshold. Early attempts at type of pacemaker system and poses a prob- direct stimulation of the heart by electrodes lem that is still under study. Wire breakage placed in the myocardium at thoracotomy interrupts effective stimulation and carries failed within a few weeks because the the risk in these patients with Stokes-Adams threshold for stimulation rose progres- disease of repeated seizures or sudden sively.25 This difficulty resulted, not from death. Initially, we used short segments of polarization or other effects of the electric solid platinum wire as the active electrodes stimuli, but from tissue reaction to the for- (Table 1). They were welded to connect- eign body, which in effect separates the ing wires of 49 strands of stainless steel electrode from excitable myocardium. Tis- that were insulated with several coats of sue reaction at the implantation site is Teflon.25 Breaks occurred in the platinum minimized by the use of a nonreactive segment or in the adjacent wire (14 of 35 platinum electrode surface and by the patients) and were attributed to the weld- meticulous avoidance of contamination of ing process or differing flexibility of the the electrode and the site of implantation adjoining wires. Accordingly, the solid with foreign particles of any kind.; In the platinum electrode was discarded. Instead, nearly four vears of the present study, wNe the multistranded stainless steel wires were have not observed stimulus failure due to electroplated alternately with gold and platinum and were then insulated with Presented before the American Surgical As- Teflon, except for a 1-cm. bare segment to sociation, Hot Springs, Virginia, April 1, 1964. form the active electrode. When breaks oc- Aided by grants from the United States Public curred in these wires also (6 of 44 pa- Health Service, National Heart Institute (HE- tients), heavier wNires of 77 strands were 02208, HE-05108, HE-06316, and HE-01984), the MIark and Anna Davidson Linenthal Fund, and thc introduced (Fig. 1); to date, no break has Edward Swartz Fund. been observed in the 23 77-strand systems 351 ZOLL, FRANK AND LINENTHAL Annals of Surgery 352 September 1964 TABLE 1. Electrical Failure and Sepsis Patients Patients Number of with with Patients Pace- Wire or Patients Period of Pacemaker Electrodes in Each maker Electrode with Implantation Unit and Wires Phase* Failure Break Sepsis July 1960-May 1961 Early (metal-encased) 12 4 3 4 Platinum-solid June 1961-March 1962 23 1 11 2 April 1962-September 1963 Platinum-plated 44 0 6 0 Present (epoxy- 49-strand wires encased) September 1963-April 1964 Platinum-plated 24 0 0 1 77-strand wires

* 26 patients in more than one phase of the method. that we have implanted since September, in relation to the many years that patients 1963. This period, however, is still too short may need reliable systems. On the basis of to provide final evaluation of wire breakage radiographic study of the movement of im- planted wires, we have repeatedly revised the method of implantation to reduce points of fixation and flexion between the pace- maker unit and the heart. We know of no instance of electrode displacement in our series: the "in-line" electrode implanted in the myocardium provides a very stable arrangement. Pacemaker Unit. Reliability is the pri- mary consideration in the design of the pacemaker. For this reason we insist on a simple system with as few components as possible, a stimulus well above threshold, and no external components that might permit interruption of stimulation. The energy source of our pacemaker is 6 1.4- volt mercury batteries with an expected operating life span of 5 years. The output of the pacemaker is a 2-millisecond, 7.5- volt, 10 to 15-milliampere stimulus, which is delivered at a fixed rate, usually about 70 per minute. The electrical components are triply sealed in epoxy resin to prevent movement, short circuit, or fluid seepage. FIG. 1. The cardiac pacemaker-electrode sys- The external case, which measures 6.5 x tem includes the pacemaker unit, the Teflon bag, 2 electrode wires, a length of Silastic tubing enclos- 6.0 x 1.7 cm., is molded of an epoxy resin ing the proximal 6 inches of the wires, the bare that is nonirritative and is tolerated well electrode segments (arrow and insert), and needles at the ends of the wires. by human tissues. The pacemaker unit has Volume 160 IMPLANTED CARDIAC PACEMAKER Number 3 353 functioned perfectly in all but 1 of the 55 the subcutaneous unit or the external bat- patients in whom it has been implanted tery must be large. In either case, an ordi- since its revision to the present design in nary bath or shower, for example, is dif- June 1961 (Table 1).* So far the longest ficult. Furthermore, preoccupation with the period an individual pacemaker unit in our equipment creates a psychologic hindrance series has been functioning is 30 months. to normal activity. Some of the early units had an expected The practical difficulty in maintaining battery life of only 2 years and have been uninterrupted stimulation appears to us to replaced. The methods for subcutaneous be the primary objection to systems with replacement of a pacemaker unit with at- external components. There are many strik- tachment by crimp connectors to the origi- ing examples of the marked unpredictabil- nal electrode wires have proved to be sim- ity and lethal potentiality of Stokes-Adams ple and effective.25 attacks when stimulation is interrupted To avoid the need for surgical replace- even momentarily. Deliberate interruption ment of the unit when the batteries wear of stimulation when atrioventricular con- out it is possible to use batteries in the im- duction returns has even been recom- planted pacemaker that can be recharged mended;1 this is equally hazardous since periodically from a radio receiver or sec- complete and ventricular stand- ondary induction coil activated from an still may supervene suddenly. Implantable external power source. Such a pacemaker pacemaker systems have been developed has been developed and used clinically.21 that permit variation of the rate of stimula- The output of the instrument, however, was tion.6' 1 The added complexity of the in- only 2 volts, and it failed in several cases. struments and the requirement for sub- This approach, therefore, cannot be con- cutaneous or external manipulation seem sidered ready for clinical application. both unnecessary and undesirable to us. Energy in the form of electric stimuli Our patients with a fixed rate of 70 to 75 can also be transmitted across the skin by per minute can carry out normal activity, radio-frequency 11 or by induction 1 from exercise, and other stresses without diffi- external sources with easily replaceable culty. Cardiac output is not altered signif- batteries. Such approaches have the addi- icantly by change in rate between 60 tional advantages of requiring relatively and 80 per minute.2 Rates about 70 are also small implanted components and of per- usually effective in preventing recurrent mitting ready external variations in rate of ventricular tachycardia and ; stimulation. Furthermore, in some modifica- rates of 60 or less may not be reliable for tions the receiver has been fixed directly this purpose.29 to the myocardium with the idea of elimi- Several workers have suggested the de- nating possible breakage of wires between sirability of driving the ventricles at the the myocardial electrodes and the re- variable sino-atrial rate and with a normal ceiver.4 23 Unfortunately, breakage of the atrioventricular sequence rather than at an stiff myocardial pin electrodes remains a fixed rate with atrio- problem. The energy requirements of all arbitrary complete these systems are such that either the ex- ventricular dissociation.9' 18, 22 The ventricu- ternal source must be in close apposition to lar rate would then vary in response to physiologic stimuli and would provide ap- * Pacemaker system made by the Electrodyne propriate changes in cardiac output, as dur- Company, Norwood, Massachusetts; batteries made by the Mallory Battery Company, North Tarry- ing sleep, exercise, and fever. Furthermore, town, New York. the normal sequence and timing of atrio- 354 ZOLL, FRANK AND LINENTHAL Annals of Surgery September 1964

FIG. 2. Tissue sites one year after implanta- tion. A. Surface of the left , showing minimal reaction at the site of electrode implanta- tion (arrows). B. Section of left ventricular wall (enlarged), showing min- imal reaction in the myo- cardial tunnel. C. Ex- ternal surface of pace- maker unit, showing loose ingrowth of fatty areolar tissue into the Teflon mesh. D. Internal surface of the Teflon bag, show- ing the smooth and glis- tening membrane ap- posed to the pacemaker.

ventricular excitation and contraction would increased complexity with consequent in- restore the contribution of atrial to creased risk of component failure and of ventricular output. Ventricular output is increased power requirement with conse- said to increase 10 per cent or more due quent shorter life of the instrument must to increase in initial intraventricular ten- be balanced against the small and ordinarily sion and to normal closure of the atrio- inconsequential increase in cardiac output ventricular valves. As demonstrated by But- and refinement in physiologic function. It terworth and Poindexter,3 atrial impulses should be kept in mind that the primary can be made by electronic means to stimu- purpose of artificial pacemakers is to pro- late the ventricle. These systems involve vide completely reliable prevention of two sets of wires on the myocardium (atrial Stokes-Adams attacks; this basic objective and ventricular) and many additional com- should not be compromised for secondary ponents in the unit. The disadvantages of gains. Volume 160 IMPLANTED CARDIAC PACEMAKER Number 3 355 Electrical Failure. Electrical difficulties electrode may be used before and during in our pacemaker-electrode system may be surgery and may save some time at the manifested by variation in the rate of the outset of the operation.10 It involves addi- pacemaker, which usually is constant within tional hazards, however, that we ordinarily 5 per cent, as well as by ineffective stimula- prefer to avoid. We have used catheter tion. Depletion of the batteries does not electrodes in 13 patients to determine the accelerate the rate, which might be danger- usefulness of a pacemaker for the particular ous, but rather slows it and then produces patient and its optimal rate, and to control intermittently or completely ineffective cardiac action during necessary delays in stimulation. Trouble in the timing circuit surgery when drugs were unsatisfactory. might lead to dangerous acceleration of the Complications occurred in eight patients: rate; stimulation should be interrupted perforation in 1; intermittently ineffective promptly and the pacemaker replaced if the stimulation in three, one of whom died; rate accelerates progressively beyond 10 staphylococcal septicemia in two; and clots per cent. Ineffective stimulation and rate on the catheter tips in two. changes may also result from breaks in the Technical Considerations. The technic of wires or in their insulation: increased elec- implantation has not changed greatly since trical resistance, such as may be produced our previous description.25 Pre-operatively, by a wire break, speeds up the rate; de- the skin is cleansed several times each day creased resistance, which may be produced for several days and monitor electrodes on by loss of insulation, slows the rate. the chest are shifted frequently to reduce skin irritation. Despite its inconvenience we Implantation Method continue to use beta-propriolactone for Control of Cardiac Action. Continuing sterilizing the pacemaker system because experience reaffirms the need for constant it is quick and effective at room tempera- control of cardiac action during all phases ture.25 of surgical procedures in patients with The retropectoral site remains our first heart block of any degree. Most of our pa- choice for pacemaker implantation. Our tients have had ventricular standstill or patients, male and female, have found this fibrillation during the procedure. Adequate position comfortable for daily activity, control requires continuous observation and heavy work, and sports. We enclose the readiness to stimulate, to countershock, to pacemaker unit in Teflon mesh prior to carry out cardiac massage, and to ad- implantation (Fig. 1) and coapt the tissues minister dilute solutions of isoproterenol or snugly about it without sewing the mesh. epinephrine intravenously.25 The adequate Pliable areolar tissue invades the mesh and management of the cardiac rhythm in these forms a smooth mold that prevents migra- patients is especially difficult during sur- tion of the unit and permits replacement gery and requires undivided expert atten- without exciting new reaction (Fig. 2). tion. Prophylactic antibiotic therapy has not usu- Stokes-Adams attacks are usually pre- ally been employed in either primary or vented pre-operatively by intravenous ad- ministration of dilute solutions of epi- secondary operations. As the two wires emerge from the pace- nephrine or isoproterenol. In the operating are enclosed in Silastic room ability to stimulate the heart at all maker unit, they times is obtained first by precordial sub- tubing for mechanical stability and sup- cutaneous needle electrodes, and later by a port. We have shortened the Silastic tube, pericardial wire.25 An intracardiac catheter however, so that it does not go through the ZOLL, FRANK AND LINENTHAL Annals of Surgery 356 September 1964 nosis should be looked for before each holding tie is completed. We have not ob- served evidence of surgical damage to coronary branches in our cases. We turn back the distal wires in J-shape (Fig. 3A), and hold them with several superficial sutures of fine silk before cutting off the needles and redundant wire. The wires are led from the implantation site along the long axis of the heart. The implantation site and distal wires are covered as the is closed, but we no longer fix the proximal wires to the pericardial edge. Instead, a cross-incision in the peri- is left open around the wires (Fig. 3B) in order to avoid transmission of the small motion between myocardium and pericardium with each beat. From the heart, the two wires are led in a smooth curve upward along the mediastinum, an- terior to the lung root but separated from the chest wall by the anterior margin of the FIG. 3. Diagram of electrode implantation. A. lung, and then forward in the upper chest The implantation tunnels are aligned toward the to the site of emergence in the second or obtuse margin of the heart and the wires toward the base; the needles have been cut away and the third interspace anteriorly. In an abdominal distal wires turned back; all fixing sutures are wall implantation, the wires are also led distal to the tunnels. B. The pericardium is closed leaving an aperture about the wires; the wires upward from the ventricle to the base of are not sutured to the pericardium but are held in the heart before being looped anteriorly course by a flap of extrapericardial fat; the phrenic nerve has been displacecd posteriorly. and downward to the costophrenic sulcus. This course minimizes flexion with cardiac chest wall and therefore can not act as a and diaphragmatic motion. The wires may conduit for infection to the pericardium. be kept in their course by flaps of medias- Broad exposure of the left ventricle is de- tinal pleura or fat, but they are not sutured sirable to permit optimal placement of the so as to rub together or flex sharply. They electrodes. Their position is not critical for are never grasped in a clamp or other bare effective stimulation: the main considera- instrument that may injure the strands or tions are the stability of the implanta- the insulation. tion, the avoidance of injury to coronary The phrenic nerve may be stimulated by branches, and an alignment of the wires conduction through myocardium and peri- that minimizes flexion stresses. The im- cardium, and should therefore be mobilized plantation tunnels are aligned in parallel if necessary, and placed well anterior or and somewhat obliquely downward and posterior to the implantation site. outward toward the lateral border of the Secondary operations may be required ventricle, to minimize buckling of the wire for specific problems. When a wire is as the ventricle contracts (Fig. 3A). The broken within its insulation, stimulation fixing sutures must avoid even small, hidden may be intermittently or completely inef- coronary branches. Local myocardial cya- fective. A single electrode in the myo- Volume 160 CARDIAC PACEMAKER Number 3 IMPLANTED 357 cardium with a distant indifferent one is trunk for two or three weeks prior to op- satisfactory and, indeed, is used in some eration. The new surgical field is carefully systems; 8, 20 we do prefer two myocardial separated from the old. If the initial in- electrodes, however, to provide a factor of cision has been anterior or anterolateral, safety in case of a broken wire or a high the secondary incision is kept posterolateral threshold. Consequently, the electrical cir- and lower. The course of the initial wires cuit may be re-established and effective is avoided, and the second electrodes are stimulation restored by baring a proximal placed in the posterior rather than the segment of this wire and fixing it in contact anterior aspect of the ventricle. The pace- with the soft tissue of the chest wall. maker unit is then usually placed in the Muscle twitch from local stimulation may abdominal wall, anteriorly or in the flank. become painful and may be corrected by With these precautions, we have obtained relocation of the bared wire. Both wires clean healing of all secondary implantations may need to be bared before the broken and have then in subsequent procedures one is identified; the unbroken one must successfully removed the infected systems. be carefully re-insulated by silicone ad- hesive * within a crimp connection or a Clinical Experience Silastic tube. This simple procedure, car- Our series consists of 77 patients. There ried out under local anesthesia, should al- is a 2-to-1 sex ratio, with 52 men and 25 ways be considered before a complete pace- women. One third (24) was under 60 maker system is replaced because of a wire years of age and one sixth (13) was 75 to break. Two of our patients have been satis- 89 years old. Many were desperately ill, factorily controlled in this way for more some almost moribund; many were worn than a year. If stimulation is not restored out by repeated, harrowing Stokes-Adams by contact of either wire with tissue, they attacks, others by refractory congestive should be cut; then the threshold for stimu- heart failure. Serious illnesses in addition lation and the output of the pacemaker may to the heart block itself were frequent; be determined. The former is done by con- they included coronary heart disease, necting an external pacemaker to the distal aortic and mitral valvular disease, chronic wire and to a temporary indifferent elec- pulmonary disease, cerebral and peripheral trode. For the latter, the proximal wires are vascular disease, obstructive uropathy and connected to a calibrated oscilloscope. If chronic renal disease, lupus erythematosus, the thresholds are high or if there is any sarcoidosis, diabetes mellitus, and severe question about the integrity of the myo- arthritis. The primary indication for sur- cardial electrodes, a new system is needed. gery in most of the patients was Stokes- The pacemaker alone must be replaced if Adams disease, in 5 it was congestive heart its output is low; the new one can be failure, and in one it was angina pectoris. slipped into the old Teflon envelope and Many of the patients had multiple indica- connected to the myocardial wires by crimp tions for opertion; and several had in- adequate cerebral or renal function as connectors.25 manifestations of reduced cardiac output When the primary sites are infected, ex- without obvious congestive failure. treme care must be taken to avoid con- All but one of our patients had atrio- tamination of the secondary field. Skin ventricular block: in most the block was sterilization is carried out over the entire complete and fixed, but in 32 patients A-V * Medical Adhesive type A, Dow Coming conduction of some degree, even com- Corp., Midland, Mich. pletely normal, was observed at least in- ZOLL, FRANK AN]D LINENTHAL Annals of Surgery 358 September 1964 TABLE 2. Duration of Treatment with all these patients has been recently con- Implanted Pacemakers firmed by us. Ntumber of Patients Mortality. There was one early postop- erative death in the 155 surgical procedures Treatment Period Alive Dead performed; this was due to respiratory in- sufficiency in an obese woman with severe (months) thoracic spondylitis. 0-i1 25 12 12-23 23 2 There were 16 late deaths, months to 24-40 12 3 years after initial implantation. Eight pa- Total 60 17 tients died of obvious causes other than Stokes-Adams attacks. They were conges- tive heart failure from severe aortic re- termittently. In none of our patients was the gurgitation and from severe cor pulmonale; heart block of a transient nature, resulting sepsis due to exteriorized wires early in our from a reversible cause such as acute myo- series; unexplained hypotension; acute myo- cardial infarction or digitalis toxicity. One cardial infarction; renal failure associated patient suffered repeated episodes of ven- with lupus erythematosus; pneumonia; and tricular standstill due to sino-atrial arrest; brain tumor. since he never showed A-V block of any The remaining eight patients died sud- degree, strictly speaking he is classified as denly. In one, a broken wire was found having cardiac syncope but not Stokes- which presumably caused death from a Adams disease.'19 28 Stokes-Adams attack when stimulation be- The etiology of the heart disease in these came ineffective. In three, all with severe patients was varied; in most cases it was coronary artery disease, ventricular fibrilla- unknown. In some, coronary artery dis- tion appeared to be the cause of death. ease, hypertensive heart disease, or valvular Fibrillation was observed as the terminal disease, mitral or aortic, was clearly present. mechanism in one of these patients; he had Congenital A-V block was present in 1 pa- shown no recent A-V conduction or spon- tient, aged 26 at operation; sarcoid in an- taneous ventricular activity and the electric other, aged 72 at operation; and dissemi- pacemaker was functioning well just before nated lupus erythematosus in a third. the sudden and at postmortem. In several patients additional unrelated The other two patients had frequent, multi- procedures were carried out during the focal ventricular beats, singly or in short primary thoracotomy: reduction of a large runs, despite stimulation about 70 per incarcerated diaphragmatic hernia, seg- minute and administration of quinidine; mental resection of lung, lung biopsy, and although these patients showed A-V con- mediastinal lymph node biopsy. These pro- duction, the ectopic activity was never in cedures were all tolerated well. initiated by an effective stimulus the Twenty-nine of the 77 patients required vulnerable period. Important in this regard are three addi- one The entire more than operation. sys- tional patients who had sudden ventricular tem was replaced 22 times in 17 patients; tachycardia despite effective stimulation but 56 other secondary procedures were neces- who survived; they all had significant clini- sitated by pacemaker failure, wire break, cal coronary disease. One of these patients or sepsis, nearly all in the early phase of had frequent interpolated ectopic ventricu- the program (Table 1). The longest period lar beats which were not controlled by of treatment with implanted pacemakers is quinidine or procaine amide, or by rapid 40 months (Table 2). The cardiac status in stimulation up to 110 per minute by means Volume 160 IMPLANTED CARDIAC PACEMAKER Number 3 359 of a temporarily substituted variable rate these untoward experiences. The stimuli pacemaker. It seems, therefore, that effec- were long in one case (5 milliseconds), tive stimulation, even at rates of 70 per they were of spike form in two, and the minute or higher, does not completely intervals between beats were prolonged prevent ventricular irritability especially (0.9 to 1.8 seconds) in all three. All these in patients with severe coronary artery dis- features may increase the likelihood of ease. Consequently, they may suffer ven- repetitive responses."4 26 tricular fibrillation with syncope or sudden It must be recognized, nevertheless, that death just as they may even if they do not the threshold for repetitive responses may have A-V block. at times be lowered by factors such as local In the remaining four patients who died myocardial ischemia, so that this hazard suddenly the cause of death is not known. may not be entirely avoidable. Such ar- The pacemaker-electrode systems were rhythmias should be most infrequent with found to be functioning properly in the stimuli of short duration (2 milliseconds), two in whom autopsies were done: one had at rates that usually suppress ectopic ven- congenital aortic stenosis, which may ac- tricular activity (70 per minute or more), count for his sudden death. The other two and by careful placement of electrodes to patients were well with pacemakers that minimize myocardial damage. were observed to be functioning normally Postoperative Morbidity. Postoperative a few hours before death. morbidity has in general been mild, and Risk of Ventricular Fibrillation from most patients were discharged by the tenth Competition. The fear is often expressed postoperative day. Eight patients had clin- that electric stimuli may produce repetitive ically significant bronchitis, atelectasis, or responses and ventricular fibrillation when pneumonitis, one with transient septicemia. they fall in the vulnerable period after con- One patient showed extensive cerebral dam- ducted beats or ectopic ventricular beats. age postoperatively with subsequent slow As a result, A-V conduction of any degree recovery even though there had been no has even been suggested to be a contrain- fall in or pulse rate during dication to implantation. More than half of surgery. Another had a cerebral vascular our patients have had such competition be- accident with full recovery. An acute tran- tween the electric pacemaker and intrinsic sient fibrinolytic reaction occurred during pacemakers, either from conducted beats one secondary thoracotomy. There has been (32 patients) or ectopic ventricular beats. no recognized instance of myocardial in- In the intensive studies that we have car- farction or pulmonary embolization during ried out in these patients, we have never or immediately after surgery. observed repetitive responses or ventricular Four patients developed fever, chest pain, fibrillation from a stimulus in the vulner- and pericarditis or pleuritis with effusion, able period even though we have examined ten to 14 days after operation. No evidence thousands of such stimuli. Furthermore, of sepsis was found, and the diagnosis of ventricular fibrillation from stimulation in post-pericardiotomy syndrome was made. the vulnerable period can not explain most All manifestations subsided promptly with of the sudden deaths in our series. Of eight steroid administration but relapses oc- patients who died suddenly only three had curred when the drug doses were reduced had competition in the months before death. too quickly. Three cases are reported, however, in Sepsis. Primary infection around the pace- which repetitive responses to stimuli in the maker occurred in 3 of the early patients in vulnerable period did occur.7' 8,24 Some whom corrosion of the metal case led to features of the stimulation may explain severe local inflammation. Three other in- ZOLL, FRANK AND LINENTHAL Annals of Surgery 360 September 1964 fections resulted from the multiplicity of stances of malfunction due to wire break- the secondary operations needed to correct age, which are becoming more and more electrical failure of early pacemakers or infrequent, attacks due to ventricular stand- electrodes. Sepsis extending to the myo- still have been eliminated. Seizures due to cardial implantation site led to the loss of ventricular tachycardia or fibrillation have effective cardiac stimulation in several of also largely been prevented; these arrhyth- these patients. Since the introduction of mias were observed, however, despite ef- the present pacemakers embedded in epoxy fective stimulation in 6 patients with severe resin in June 1961, there has been only one coronary artery disease. instance of infection (Table 1). The artificial pacemaker has also been The surface materials now in use (Teflon, very valuable in improving congestive heart epoxy resin, Silastic, platinum) have proved failure. Other manifestations of diminished remarkably nonirritating. Re-operations in cardiac output were also significantly amel- uninfected cases have disclosed no inflam- iorated. In several patients improvements mation, fluid accumulation, or significant in cerebral function have been particularly scarring about electrodes, wires, or pace- striking: mental acuity and memory were maker unit (Fig. 2). When sepsis has oc- greatly improved; headache and confusion curred, however, it has with few exceptions to the point of dementia were relieved. Ob- persisted in spite of chemotherapy and jective measures of improved cardiac out- drainage, until the foreign bodies were re- put were also obtained in many patients: moved. Consequently, although sepsis has significant reductions were measured in been infrequent, each instance has led to , heart size, and systolic or prolonged morbidity and multiple opera- . tions. Since cardiac stimulation cannot be In view of the recent discussions of the interrupted safely in these patients, it is advantages of variable-rate or P-wave s vn- necessary to implant a complete new sys- chronized pacemakers,"' we have made a tem before the old system is removed. careful clinical analysis of the functional Late Complications. Some months after status of our patients after surgery. In par- operation, two patients developed a di- ticular, we wished to determine how many aphragmatic twitch, synchronous with car- patients had significant limitation of func- diac stimulation. This has not required cor- tion that might possibly have been im- rection in these patients, but we now dis- proved byr a variable rate. NMost of the pa- place the phrenic nerve routinely at the tients have been well and able to function time of implantation, even though no without cardiac symptoms at levels of ac- phrenic stimulation is observed. tivity compatible with their general physi- Six months after implantation one pa- cal condition. Unless prevented bv other tient noted the onset of a severe pectoral infirmity they have returned to work, house- muscle twitch due to a wire break; this was hold activity, and sports (golf, water skiing, corrected by connecting the broken wire swimming, hunting) without limitations. from the pacemaker to a long bare wire Only five patients had some congestive fail- which was placed subcutaneously well ure or weakness after recovery from sur- away from muscle. gery. In two, severe sepsis and anemia were adequate explanations for the symptoms; Results indeed, the congestive failure cleared when The implanted pacemaker has been a the sepsis was controlled. In the other three most effective means of preventing recur- patients extensive myocardial infarction, rent Stokes-Adams attacks. Except for in- marked cardiac hypertrophy, and pulmo- Volume 160 IMPLANTED CARDIAC PACEMAKER 361 Number 3 nary emphysema accounted for the conges- other manifestations of diminished cardiac tive failure and weakness. Many of the pa- output in patients with heart block and tients underwent severe stresses with re- slow ventricular rates. markably little circulatory difficulty: 11 had Stokes-Adams attacks, unless due to a serious infectious processes, 15 had major transient or reversible condition, are a com- surgery, four suffered the post-pericardi- pelling indication for implantation of a otomy syndrome, one suffered peripheral pacemaker. In view of the unpredictability vascular collapse from massive gastro-in- and lethal potentiality of the attacks and testinal hemorrhage, and one enjoyed a their uncertain prevention by drugs, even normal pregnancy and delivery without a single, mild episode calls for the assured difficulty. prevention of further seizures by a reliable Electric stimulation of the heart, both electric pacemaker. The low operative mor- external and direct, has provided oppor- tality and morbidity in our series, even tunities for physiologic and pharmacologic with elderly and desperately ill patients, studies, many of which have previously not indicate that there are few if any patients been possible in man, and has led to re- with Stokes-Adams disease to whom this vived interest in heart block and Stokes- treatment should not be offered. Conges- Adams disease in the last decade. Such tive heart failure and other manifestations studies have included the relation of heart of diminished cardiac output in patients rate to cardiac output,2 effects of sympa- with slow ventricular rates constitute an thomimetic amines on ventricular rhythmic- additional indication for surgery. We do ity and atrioventricular conduction,27 de- not consider heart block alone in an asymp- pression of idioventricular pacemakers by tomatic patient to be an indication for rapid stimulation,16 delineation of refrac- treatment. tory and supernormal periods of ventricular excitability,"3 features of antegrade and Acknowledgments retrograde atrioventricular conduction,' We wish to acknowledge the assistance of Dr. and an analysis of fusion beats.'5 Advances L. R. N. Zarsky and Alan H. Belgard. in our knowledge of , particularly in relation to , must References surely come from such observations, which 1. Abrams, L. D., WV. A. Hudson and R. Light- have their origin in this electrical approach wood: A Surgical Approach to the Mlanage- to the treatment of this long-recognized, ment of Heart-block Usingt an Inductive uncommon, and still poorly un- Coupled Artificial Cardiac Pacemaker. Lan- somewhat cet, 1:1372, 1960. derstood disease. 2. Benchimol, A., Y-B Li and E. G. Dimond: Cardiovascular Dynamics in Complete Heairt Summary Block at Various Heart Rates. Effect of Ex- our with ercise at a Fixed . Circulation. In This report presents experiences press. long-term electric stimulation of the heart 3. Butterworth, J. S. and C. A. Poindexter: in 77 patients during the last four years. Fusion Beats and Their Relation to the Syn- Our implanted, fixed-rate pacemaker has drome of Short P-R Interval Associated with eliminated Stokes-Adams attacks due to a Prolonged QRS Complex. Am. Heart J., ventricular standstill and has also largely 28:149, 1944. to 4. Cammilli, L., R. Pozzi and C. Drago: Remote prevented seizures due ventricular tachy- Heart Stimulation by Radio Frequency for cardia or fibrillation. In addition, the arti- Permanent Rhythm Control in the Morgagni- ficial pacemaker has been very valuable in Adams-Stokes Syndrome. Surgery, 52;765, improving congestive heart failure and 1962, 362 ZOLL, FRANK AND LINENTHAL Annalsoe Surgery 5. Chardack, W. M., A. A. Gage and W. Great- in Atrioventricular Block. Abstract, Circula- batch: Correction of Complete Heart Block tion, 22:781, 1960. by a Self-contained and Subcutaneously Im- 17. Linenthal, A. J., P. M. Zoll, G. H. Garabedian planted Pacemaker. Clinical Experience with and K. Hubert: Retrograde Conduction to 15 Patients. J. Thoracic and Cardiovas. the Atria from Electric Stimulation of the Surg., 42:814, 1961. Ventricles in Man. Abstract, Circulation, 26: 6. Chardack, W. M., A. A. Gage, G. Schimert, 752, 1962. N. B. Thomas, C. E. Sanford and W. Great- 18. Nathan, D. A., S. Center, C-Y Wu and W. batch: Two Years' Clinical Experience with Keller: An Implantable, Synchronous Pace- the Implantable Pacemaker for Complete maker for the Long-term Correction of Heart Block. Dis. Chest, 43:225, 1963. Complete Heart Block. Circulation, 27:682, 7. Dittmar, H. A., G. Friese and E. Holder: 1963. Erfahrungen iiber die langfrigstige Elek- 19. Parkinson, J., C. Papp and XV. Evans: The trische Reizung des menschlichen Herzens. Electrocardiogram of the Stokes-Adams At- Z. f. Kreislaufforsch., 51:66, 1962. tack. Brit. Heart J., 3:171, 1941. 8. Elmquist, R., J. Landegren, S. 0. Pettersson, 20. Siddons, A. H. M.: Long-term Artificial Car- A. Senning and G. WVilliam-Olsson: Artificial diac Pacing: Experience in Adults with Heart Pacemaker for Treatment of Adams-Stokes Block. Annals Royal Coll. Surg., 32:22, 1963. Syndrome and Slow Heart Rate. Am. Heart 21. Siddons, A. H. M. and O'N. Humphries: J., 65:731, 1963. Complete Heart Block and Stokes-Adams At- 9. Folkman, M. J. and E. Watkins: Artificial tacks Treated by Indwelling Pacemaker. Conduction System for Management of Ex- Proc. Royal Soc. Med., 54:237, 1961. perimental Complete Heart Block. Surg. 22. Stephenson, S. E., Jr., W. H. Edwards, P. C. Forum, 8:331, 1958. Jolly and H. WV. Scott, Jr.: Physiologic P- J. Thoracic & 10. Furman, S., J. B. Schwedel, G. Robinson and wave Cardiac Stimulator. Use of an Intracardiac Pace- Cardiovasc. Surg., 38:604, 1959. E. S. Hurwitt: Experimental maker in the Control of Heart Block. Sur- 23. Stoeckle, H. and J. C. Schuder: a Pacemaker gery, 49:98, 1961. Experience with Micromodule Receiver Sutured Directly to the Left Ven- 11. Glenn, W. W. L., A. Mlauro, E. Longo, P. H. tricle. Circulation, 27:676, 1963. Lavietes and F. J. MacKay: Remote Stimu- 24. Tavel, M. E. and C. Fisch: Repetitive Ven- lation of the Heart by Radio Frequency tricular Arrhythmia Resulting from Artificial Transmission. Clinical Application to a Pa- Internal Pacemaker Stimulation. 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