Types of Pacemakers and their Complications

Transcription

1 Types of Paemakers and their ompliations By DoRIs J. W. EsHER, M.D. Downloaded from by on November 3, 218 T HE THREE TYPE of artifiial ardia paemaker systems in ommon linial use are: 1. Implantable pulse generators with endoardial or myoardial eletrodes for long-term or permanent use. 2. External, miniaturized, transistorized, patientportable, battery-powered, pulse generators with exteriorized eletrodes for temporary transvenous endoardial or transthorai myoardial paing. 3. onsole battery- or A-powered ardiovertors, defibrillators, or monitors with high-urrent external transutaneous or low-urrent endoardial or myoardial iruits for temporary paing in asynhronous or demand modes, with manual or triggered initiation of paing. onsole Paemakers The simplest and fastest method of paing is external transutaneous stimulation by two eletrode plates or subutaneous needles applied to the skin of the hest.1 However, the high voltages required (75-15 v) to penetrate to the heart result in vigorous and painful ontrations of the musles of the hest wall, tolerable only under sedation. apture is unertain ill the obese or emphysematous patient, and skin burns may our as a result of insuffiient eletrode jelly or prolonged use. This route of paing, therefore, is reserved for brief emergenies or where no other means are available. The use of alternating urrent (A) powered onsoles for temporary endoardial or myoardial stimulation always arries the risk of malfuntion with the possibility, despite safeguards, of induing ventriular fibrillation by A leakage into the paing wires.2 Battery-powered onsoles eliminate this diret risk, but as paemakers they are bulky, limit mobility and ambulation, and are less onvenient and more expensive than miniaturized units. External Paemakers External, patient portable, battery-powered pulse generators are designed to provide a wide range of From the ardiology ervie Medial Division, Montefiore Hospital and Medial enter and the Albert Einstein ollege of Mediine, Bronx, New York. irulation, Volume LVII, May hoies in paing rate, urrent amplitude, and mode of ation. everal models are available (table 1). ommon features are that they are small in size (average 11.7 x 7.4 x 3.1 m), are light in weight (average 3. g), an be strapped to the patient's hest or limbs, are designed to aept, diretly or by adapters, all or almost all eletrodes likely to be utilized with them, are readily servied for battery hanges or leaning, are apable of gas autolaving for sterilization or ontamination ontrol, and are of inreasingly dependable reliability. These units operate in the asynhronous and R- wave inhibited modes over a wide range of rates. Their low trigger sensitivity may allow for their use in atrial as well as ventriular nonompetitive paing. The Vitatron Triplextern offers the additional feature of ventriular synhronous paing. This has a very useful speial appliation in treatment of paing failure of an implanted system operating in the fixed-rate mode with intermittent stimulus output or with regular output but intermittent apture. In these ases, where the implant emission annot be suppressed by external stimuli and indues ompetition with asynhronous external paing or suppression of R-wave inhibited external paing, synhronous paing loks to the timing of the implant emission and effets nonompetitive external supplemental paing. It is not preferable to ventriular-inhibited paing in routine use, as the stimulus artifat in the absolute refratory period deforms the eletroardiogram and may not be absolutely safe.3 The Triplextern also has a six-beat hysteresis in the R-wave inhibited node. The optional rate-doubler feature of the General Eletri External tandby is useful in the speial ase of rapid supraventriular tahyeardias where it permits apture and rate redution by overriding paing or the disruption of a rapid tahyardia or flutter by the bloking ation of brief appliation of very high rates.4' 5 Rapid fixed rate paing (to 4 beats/min), atrial and ventriular synhronous or stimulus-inhibited paing, and paired and oupled paing are otherwise available only in speialized instruments, suh as Medtroni Multiple Mode Researh Generator (5837) or the ordis ynhroor II.

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3 Downloaded from by on November 3, 218 TYPE OF PAEMAKER Any unipolar or bipolar temporary or implantable paemaker eletrode an be onneted to any of these external generators. The routes and tehnis of appliation and their speial utilities or problems are: (1) Perutaneous transthorai diret myoardial punture of the left ventrile by a needle eletrode or by a temporary needle inserter through whih a fine-wire or oil-spring eletrode is passed to the lumen.6 This tehni, reserved for the aute emergeny, an be lifesaving. ompliations are potentially grave and inlude the possibility of pneumothorax, damage to a oronary artery, tamponade, and, espeially if used during losed-hest massage, of unstable paing or eletrode displaement. (2) Myoardial wires inserted by thoraotomy after pulmonary or ardia surgery6' 7 In this appliation, an exposed segment of an otherwise insulated or braided-steel wire suture is stithed through the myoardium in suh a fashion that a light tug an remove it without diffiulty. Two wires are applied to the hamber to be paed (atrium or ventrile) for bipolar paing. In unipolar paing, one wire (the athode) is applied to the myoardium, and the seond "indifferent" wire (anode) is applied to the skin. ommon diffiulties are premature displaement of the loosely applied wires and/or marked inreases in threshold to pae. Less frequently, failure to pae is aused by touhing of exposed wires or their approximation in fluid pools, with short iruit of output or demand suppression of output by etopi (wire motion or interferene) signals. If the signals are rapid transients, they may not be seen on the peripheral eletroardiogram or even on the myoardial eletrogram but should appear on an osillisope with an expanded time and amplitude sale.8 (3) Perutaneous transvenous endoardial atheter eletrodes passed to the right ventrile or right atrium though the right or left sublavian vein by the infra- or supralaviular route and the right or left femoral. brahial, and external or internal jugular veins.9' 1 The eletrodes ommonly used are the United tates atheter and Instrument orporation (5651, 5652) and the Eletro-atheter ompany (Eleath 51-2, 351-2) 5F and 6F bipolar atheter eletrodes, usually passed under diret observation by fluorosopy, and the ordis orporation (37-11) and Eleath (561) semifloating 4F bipolar eletrodes, usually passed by indiret eletroardiographi ontrol. The heavier irulation, Volume LVII, May and stiffer eletrodes are more likely to stay in plae if they are positioned visually as well as eletrially. They are inserted in the jugular and brahial veins by diret utdown, and similarly in the femoral veins of hildren. In adults, they are passed routinely by perutaneous needle in the femoral vein and oasionally in all other veins. The semifloating eletrodes are almost always inserted by perutaneous needle, usually by the subelavian or brahial veins, and oasionally by any other vein. They an be monitored by eletroardiograph or -ray. A number of ompliations relate speifially to partiulars of appliation. The brahial route is assoiated with an inreased inidene of thrombophlebitis'1 and of motion displaement12 of any eletrode (espeially if the arm is lifted over shoulder level) with disruption of paing'3 and myoardial perforation.14 To a lesser degree, motion displaement ours with the femoral route when both knee and hip are flexed 9', but disruption of paing is muh less frequent (5-7%) and aidental perforation of the artery during insertion (3%) responds promptly and benignly to 5 min of loal pressure.9 15 The subelavian route is known to allow arterial punture (3%), pneumothorax (.7%), and rarely an extravasular, intrapleural eletrode passage. The relatively high freoueny of easilv orreted eletrode malposition (17%) is not a funtion of route but of positioning by eletroardiography rather than by diret vision. Bateremia (1%) and gross sinus infetion (2%) are problems ommon to all perutaneous insertions but fortunately of low inidene, espeially with good skin hygiene, and are promptly responsive to eletrode withdrawal and antibioti therapy.16 Most of the operating ompliations are inherent in the situation: the external eletrodes are temporarily onneted; the pulse generators are subjet to disruption and interferene beause they are exposed and mobile, with adjustable ontrols and short-life removable batteries; they are handled, mishandled, and servied by various personnel or even patients. Beause they are exposed, however, they an be inspeted, tested, repaired, or hanged with no trauma to the patient unless an eletrode has to be repositioned or replaed. The major problems are an inreased inidene of external damage, wetting, wire shorting, poor extermal eletrode ontat, gross eletrode displaement or internal eletrode malposition, battery

4 Downloaded from by on November 3, depletion, and the inreased risk of A interferene or indued fibrillation.2' 8 EHER Implanted Paemakers Implanted paemakers are of two basi types: (1) fully implanted; (2) radiofrequeny or eletromagnetially oupled semiimplants. In the semiimplanted group, the pulse generator, with replaeable batteries and variable rate and urrent-amplitude ontrols, is arried externally. Its paing stimulus is released through a primary-oil antenna taped to the patient's skin overlying an implanted seondary-oil reeiver. The implanted unit is a subutaneous seondary oil attahed to a standard implantable myoardial or endoardial eletrode urgery is not required for pulse generator replaement, and many threshold or rhythm problems an be handled by hanges of rate or urrent amplitude or the use of speially tailored pulse generators.22 The very small size of the reeiving apsule an be aommodated in the limited subutaneous tissue of infants or aheti adults eliminating the tumesene and pressure nerosis that an result in these patients even with "pediatri"-sized fully implantable pulse generators. The disadvantages are the bulk, onstant presene, and psyhologial pressure of the need to are for the external generator and relatively fragile antennae, the risk of aidental displaement or frature of the antennae (intrinsi to this system), and the fat that these systems operate only in the fixed-rate mode. In the United tates the relatively arefree fully implanted paemakers are preferred, and therefore the semiimplanted systems are very rarely used. Only one, the ordis orporation Transior, is available by speial order. In Europe, espeially England, they are in more prevalent use, even where ompetition ould be antiipated beause of their fixed-rate limitation Fully implanted paemakers are now manufatured in most nations with sophistiated tehnologies. Tables 2 and 3 list most instruments made or retailed in the United tates. Established produers and new firms (e.g., in the U..A., Edwards Laboratories) regularly introdue new models. Fully implanted paemakers are ategorized primarily on the basis of their pulse-generator funtion as asynhronous, atrial synhronous, ventriular synhronous, and ventriular inhibited. The latter three, with sensing iruits, are also known as triggered paemakers. The ventriular synhronous and ventriular inhibited units, variously termed demand or standby paemakers, are both nonompetitive instruments. Implanted paemakers are further ross ategorized by whether they are unipolar or bipolar, transvenous endoardial or transthorai myoardial systems and whether they are paing the ventrile or the atrium. Asynhronous Paemakers These are defined as "pulse generators in whih the repetition rate is independent of the eletrial and/or mehanial ativity of the heart."26 Their stimulus repetition rate usually is set at 6-7 beats/min for adults and 8-1 beats/min for hildren, and they disharge at this rate regardless of the underlying rate or rhythm of the patient. They have the simplest onstrution and are the most stable and long lasting of all implants. Without a urrent-utilizing, ontinuously operating sensing iruit they have fewer omponents to fail, no nonpaing battery drain,27 28 and little or no response to eletromagneti interferene.29 They even have a somewhat lower inidene of problems with their eletrodes, beause they exlude those related to failure to sense or to the delivery of false signals as may our in triggered systems.27 The major defet of asynhronous paing is ompetition if there are interpolated spontaneous beats or tahyarrhythmias. Patients often find the resultant "palpitations" disquieting. Physiian disquiet foresees ompetition-indued ventriular fibrillation. The degree of risk of this ourring is disputed but is probably low in healthy patients and inreases if there is tissue anoxia or injury, eletrolyte imbalane, or drug toxiity.3-32 Atrial ynhronous Paemaker Historially the first implantable triggered system,33 it is "a ventriular stimulating pulse generator, the repetition rate of whih is diretly determined by the atrial rate"26 (table 3). It senses the atrial ontration voltage and, following a simulated P-R interval, emits a ventriular stimulus. It utilizes two eletrodes, atrial sensing and ventriular stimulating. These are usually sutured to the left atrium and ventrile, when implantation is by thoraotomy. The atrial potential to the sensor is mv.34 Right-sided transvenous atrial synhronous paing is muh less reliable as atrial eletrode stability is diffiult to maintain and the atrial signal is only.5-3. mv If the atrial signal is lost, beomes subthreshold, or slows below the base rate (lower esape rate), these paemakers are programed to drop into asynhronous paing at 6-7 beats/min for adults, 7-9 for hildren. An upper irulation, Volume LVII, May 1973

5 TYPE OF PAEMAKER 1123 E ~~~~~~~~~~~~~~~.= the o d * -. -o ḍ _ ~. - 5 Q - d E e E:: 3-- g;, oe e ) V ) 4 ) 4 o e- -o o O GO L[n to li ol o~ o - -o o~ 12 Downloaded from by on November 3, 218 eq, 1 44 Ẉ n p ax D 1.:>.b 4- bp (/7 N ' - o; 1 1 I. 1 r 1 q 1 LO - L^,= ooo ~1~ o Ln 111 ~ 1 q - ~4 N- N- ~ N N 1 s..t o - - o Q _ t-_ Gm _ m 1<, - -14L r q o o) m P- (2 oo 1> oo o o L < L 1, < LO Le L, >- 6 - N l.l I..O.~ L N- n.... It m GO Z~ O6 O O6 GO l) d 1 x 2 * ) N 1 GO 1 GO m DJ po N 1~ ] IO ID ed ep e&d 1 :, ~ o t- - t- - t- t--- r- m + +F o ' ṟ P- " ~ O O O1 _ I. in O O dnf 1. d ri q 1, l] xx + O O O -. 1 NNm ' VV t- t M I s s ls t- m O s O xxx P to L _- q Y... Fx- YL. Y. F-._4 ~ 4*-4.-4 : P4.5 E 3 -..) rn ) O m ) -o ) _ 44 Q~, :" : "; d. 5 Ft1 ~ -e._ -) _4 W _1 a~ ) 2._ O, L.o Q, W pp ;J75-1b._ o - -; P ^ sp *- ) n= s; Q Q= l..5 n ++o o 1 o: V i9fdat.o,z, Volume LVII, May 1973

6 1124 EHER a~~~~~~~~~~~~~~~~~e W o r_ * d U? o U e = d4 blj m 5 5 ~~~~~~~~~ ~~~o5 ) a~~~~~~~~~55a ~~4_ ) (d W ~~~~~~~~ * a 4 I)- * M. ) e , 6 ~~~~~1-4 ' L'- e ~ ~ ).7:5 ep, ~ ~ ~~~~ ~~~~~~~~~~~~~~~- - ) N ) * V) ;. awj Qd-..4 e ) ) ) o ) Downloaded from by on November 3, 218 I- 4.. a a ) Q) ~).... ) OD )'- or).5 +k. ) o) - a ) ~5( a 1 ) m ) 2 - ) +4f ai -a ) a O - ~~~~-;~ ++. ~~~~. -a n o * 6 o6 r )i,^ lit O.. O O O 1 n 1 OLt: q,] i. _ 1 _ H OQ 1E- to O ` L i 6 P'-o t in. Id 6d L.OD ) sw ' L4 'In. n O 6 D eop._ a 1q - = OOa - '- '-o O~ Ol 1. M +4 O~~~~~L ZOO Z Z e-ioi zo Zo ~o ---W O 6d 6 O t 'i t'- -~~~~~~e m +4F 3 t- t- W M" Ad~~~V' _ O- _ Vl = --4 Al Al ilo t' I- pi ' -- - O - Ō. L'1 6dI-l ' ~6. ' Q6 11' t6 1 L6 O t O O9D ) o; P4 ) m -- b -.5 ta t bid n - *- A~~~~~~~~a E E tsa t~~d3 a a ) t- W V2 3) O~~~_)9 t. n. >- ) ~ Ea N ) 1. 5 r 2 : o;q d b~ _Og a - 56'f O* (L (D)" 'a, ) > 4 O * ~ -a ~~~~a~ *be ~ ~..a ~~~~+ a~ -~ ~ Q ~*5 ' -I ) ) *_, W a W -W -; a._ 1 ) ) ȧ) P- a al) ;. *_ a._. E) a _.). P._ i W.) - Ita irulation, Volume LVII, May

7 TYPE OF PAEMAKER 1125 esape limit protets the ventrile against diret stimulation in anl atrial tahyardia by initiating a 2:1, 3:1, or 4:1 blok. A poststimulation refratory period to sensing or paing protets against reativation of the paemaker by its own eletrode apaitane and against an early atrial premature ontration releasing a ompetitive stimulus on the T wave of the preeding QR. The ompliationis of atrial synhronous paing inilude the following: (1) Diffiulty in positioning and maintaining transvenous atrial eletrodes for stable sensing despite newly designed eletrodes or speial tehnis for transvenous36, 3 or mediastinal insertion.38 A Thoraotomy, whih does provide stable positioninig, is aeptable in the young, diffiult for the old, and obligates repeat thoraotomy if there are initrathorai eletrode problems. With loss of atrial sensing, fixed-rate paing supervenes, ompetitive if there is an underlying spontaneous rhythm. Oasionally, the sensor responds to a ventriular instead of an atrial signal, and the paing stimulus is emitted at the end of the QR or start of the T wave. This is probably not dangerous as long as the impulse is delivered early enough in the -T area to avoid the vulnerable zone (fig. l. (2) Heart failure or angina with stimulated ventriular rates of 1-12 or beats/min, V Y ::..: ::.. :...,. T : w!a- Downloaded from by on November 3, 218 Y, -- JE _4m.t. h.g -fl 4 :7- : I; 2,2t t: t - 1~~i I- lv- _:~ 9t' *.; -:-7- A-- :1 Figure 1 (a.) Atrial synhronous paing () with an asynhronotus paed beat (A) and ventriular triggering (V). (b.) Atrial synhronous paing with intruding ventriular extrasysotles. This artifat may be ventriwzzar synhronized and triggered; if it were not sensed it would fall on the apex of the T wave asynhronously. (.) Rate aeleration of triggered paemakers by external interferene. (d.) Ventriular synhronous paing with late sensing (third and fifthqr) and triplets (third and fifth beats and fifth to seventh beats), beause of early unsensed extrasystoles. (e.) Bifoal paing with atrial and ventriular stimulation with response to an extrasystole. (f.) Inadequate sensor signal. The differene between the large distal and proximal intraardia bipolar signal (left and middle omplex, respetively) is so little that the bipolar signal generated between them is barely 2 mw (right omplex). irulation, Volume LVII, May 1973

8 Downloaded from by on November 3, in response to the sensed rapid atrial rates of sinus tahyeardias, multiple atrial extrasystoles, or atrial flutter or fibrillation with inadequate blok. Digitalis does not affet the bloking mehanism in these ases, and these upper esape rates, designed to aommodate to a sinus response to exerise, are too high for the patient with a diseased myoardium, protheti valve, or oronary narrowing. In a oarse atrial fibrillation, signals of trigger amplitude may result in irregular ventriular tahyarrhythmias interspersed with fixed-rate paing. Here, digitalis may onvert a oarse fibrillation to a finer more rapid ation, less likely to eliit synhrony. (3) Failure to sense or aommodate to ventriular extrasystoles whih produe an effetive ventriular tahyardia if they intrude between sinus paed beats and ompetition if the sueeding atrially triggered stimulus falls on the vulnerable period of their T wave (fig. lb). ( useptibility to eletrial or eletromagneti interferene whih in the physiologi rate range trigger simulated atrial premature ontrations when the signals are disrete or drive the pulse generator to its upper limit of performane if repetitive. At supraphysiologi rates, inluding 5-6 yle alternating urrent, the pulse generators blok to asynhronous paing usually at their lower esape rates (table 3). The risk of ompetition engendered is less than that of a sustained upperlimit tahyardia (fig. l). Ventriular ynhronous Paemaker This paemaker is one with "a ventriular stimulating pulse generator delivering its output synhronously with the natural ventriular ativity and asynhronously in the absene of natural ventriular ativity"26 (table 3). Ventriular synhronous paemakers are modifiations of atrial synhronous paemakers. They have a similar upper and lower safeguard esape rate, but utilize a single ventriular eletrode for sensing and stimulation, have a lower trigger sensitivity, an almost immediate response to a trigger stimulus, logi to differentiate the QR from the P and T waves, a refratory period of about 4 mse, and a magneti-swith asynhronous mode. They are nonompetitive with ventriular ativity exept in very rare instanes and insensitive to nontransmitted atrial ativity.39 4 peial problems or defiits assoiated with their use inlude the following. (1) During sustained synhronous stimulation, the threshold to pae is unertain, and its adequay EHER must be heked periodially by overdrive stimulation or magneti onversion to asynhronous paing. (2) Failure to sense (eletrode malposition, battery depletion, or signal derement) results in fixed-rate paing and, if the paing threshold is sustained, ompetition with spontaneous rhythms.4' 42 (3) The synhronous-paer artifat onsistently distorts the eletroardiogram even during sinus rhythm. Magneti mode paing allows oasional breakthrough of unpaed spontaneous beats if the rhythm is at or over the esape rate, but this engenders ompetition and is avoided when the need to see a true omplex is the highest, i.e., during an aute oronary. ( Extrasystoles that ome within the refratory period of a paed beat are not sensed, and the next paed beat, yling at the esape rate from the previous paed beat, results in a tahyeardi triplet. Prolongation of the refratory period enhanes this effet and allows the paed "esape" beat to ome unomfortably lose to the T wave of the "missed" spontaneous beat These mixtures of spontaneous and etopi beats, with synhronous and paed beats, are diffiult to interpret and often alarming to the uninitiated (fig. ld). (5) A wide variety of transient "interferene" urrents, inluding those produed by the magneti or radiofrequeny tripping of the magneti swith, wire breaks, faulty onnetions, short iruits, whipping atheter motions, and tall T waves, are equated with QR signals by the sensor iruit.44 This results in an errati, frequently ompetitive, paing output. With repetitive stimuli, however, the response rate annot exeed the top design output of the paemaker (a fail-safe feature) (fig. l).45 A positive effet of this interferene sensitivity is that these pulse generators may be externally triggered to overdrive rates (to their upper esape limits), whih is useful in the treatment of postimplantation multifoal extrasystoles or intermittent tahyarrhythmias. (6) Late synhronization oasionally ours with the stimulus late in the QR. Rarely, it reahes the vulnerable zone and initiates early or repetitive ontrations.46 In right-sided transvenous paing, it has been asribed to origination of the ontration on the left with delayed ondution to the right (RBBB). There may also be a speifi lateny, with either ventrile, partiularly in reent infartion (fig. Id). (7) Impulses driven into the "absolute refratory" period may sensitize to lesser, later impulses. irulation, Volume LVII, May 1973

9 Downloaded from by on November 3, 218 TYPE OF PAEMAKER This suggests reexamination of the use of the ventriular synhronous mode and may be a soure of problem in ompetition.3' 46 (8) The ventriular synhronous paemaker has the shortest mean longevity of battery life due to onstant paing, often above the esape rate, and the additional urrent drain of the sensing iruit.27 Ventriular-Inhibited Pulse Generator This is "a ventriular stimulating pulse generator whih suppresses its output in response to natural ventriular ativity, and produes an output asynhronously in the absene of natural ventriular ativity"26 (table 3). It is a nonompetitive paemaker with an esape rate below whih it paes asynhronously (6-7 beats/min in the adult) and above whih stimulus output is suppressed, leaving the patient and eletroardiogram unaffeted.47 The refratory times are foreshortened ( mse) to allow early response to etopi ativity. All models have magneti swithes to onvert onduted or other spontaneous rhythms to fixed paing exept the disontinued Medtroni This enables testing for the ability to pae in a patient, normally in the inhibited mode, and ounting of the output rate for battery follow-up. The General Eletri, Medtroni 5843 and Vitatron have a rate-hysteresis apability. everal are ased in metal as a radiofrequeny interferene deterrent and/or to exlude moisture. Ventriular-inhibited paing is the most popular mode in use. The lak of artifat output during spontaneous rhythm leaves the eletroardiogram lear and also is battery sparing, with signifiant improvement in longevity.27' 3 The inability to aelerate rate by triggering (exept in the General Eletri A772 and disontinued Medtroni 5841) is disounted. ompliations of use inlude the following: (1) The major problem of etopi (non-qr) suppression of output, indued by a variety of signals: (A) elf-inhibition, beause the short refratory period of several paemakers allows feedbak of undissipated stimulus afterpotential (apaitane) from the eletrode tissue interfae. If the urrent is of trigger magnitude, it is not differentiated from a QR and reinhibits output for another yle. In the Medtroni 5841 and Amerian Optial DB7 or DM7, one reyle always ours after a paed beat making the paed-to-paed R-R interval longer than the spontaneous-to-paed R-R interval irulation, Volume LVII, May by the length of one refratory period. Oasionally, stimulation is markedly delayed when a short refratory period, a low trigger sensitivity, and a high paer output or apaitane ombine to reyle these pulse generators from one to four times.27' 43 (B) Partial sensing with inomplete inhibition and rate irregularities from a marginal signal or borderline reeption of a normal signal in a narrow zone between the refratory and alert period. These low signals, observed primarily in Medtroni 5841 and 5842 and Amerian Optial paemakers, ause inomplete saturation of the output iruit and partial, rather than omplete, reyling.48 They may our with other equipment. () Reyling by large P or T waves (partiularly if superimposed), whih may result in a bradyardia from T-wave sensitivity or asystole from repetitive P-wave stimuli.27' These marginal urrents also may indue partial reyling. (D) Inhibition by loal nonpropagated ventriular urrents (onealed extrasystoles), whih trigger the sensor but not a ontration. They are unseen on a peripheral eletroardiogram, appear as transients on an intraardia eletrogram, and may be suppressed by antiarrhythmi mediation or overdrive paing.5 (E) False signals (transient urrents) from any type of inomplete wire break, sheath interruption, intermittent short iruit, wetting, loose onnetion, ontat with an adjaent seond eletrode (ative or inative), or whipping resistane altering or atheter motion whih may be the soure of errati sensing. This is often assoiated with intermittent failure to pae without evidene of battery depletion (F) uppression by alternating urrents, or radiofrequeny, eletromagneti, and magneti interferene. Weak alternating urrent leaks from poorly grounded equipment have no diret route to fibrillate the heart. If of magnitude enough to affet the paemaker, they will be sensed, and the ontat is usually severed before serious effet. Radiofrequeny and eletromagneti signals are silent. The patient may appreiate palpitations in synhronous paemakers, but inhibited paemakers suppress funtion without warning and may kill a dependent patient. The signal soures that have been desribed or tested inlude various types of eletri motors (tools, household, garden) automobile ignition systems, aring television sets, eletri onoff swithes (all spark-gap soures), eletri razors, diathermy, eletri autery, mirowave ovens,

10 Downloaded from by on November 3, power generators, and television, radio, and radar transmissions.2-8' 29, Fortunately, atual aidents are so infrequent that virtually all are reported. Most small motors (tools and applianes) have too low an output to be dangerous unless they are held diretly over the paemaker (unlikely). Larger signals, suh as from on-off swithes or aring equipment (i.e. television sets), are short-term or intermittent and, exept in automobile ignitions or razors, not likely to inhibit the paemaker for more than a beat or two. peifiity further redues inidene, so that only some paemakers in some patients are affeted by some equipment. The greater degree of vulnerability that ould be antiipated with radiofrequeny reeivers (the semiimplants, the General Eletri generators with rate ontrols) has not, apparently, been an issue. In high-frequeny interferene, inhibition may be by the arrier wave or a lowfrequeny modulation, whih brings the impulse into the physiologi rate range (mirowave-oven fans). The most vulnerable environment, partiularly for external pulse generators, is the hospital with its diathermy, autery, ardioversion, and eletroshok therapy, monitoring equipment, mirowave ovens, eletri beds, and eletrial lifesupport equipment. A positive use of etopi inhibition is external hest wall stimulation to suppress the output of an implanted pulse generator and display the underlying rhythm. are must be taken to protet against asystole or esape arrhythmias (2) Low sensor signals or loss of sensor signal with failure of appropriate inhibition that results in fixed rate, sometimes ompetitive paing. The soures of initially poor signals inlude an underlying myoardial sar, inadequate myoardial or endoardial ontat (poor position), poor orientation of a bipolar eletrode with a less than 2-mv amplitude in the bipolar voltage (the trigger signal) (fig. lf), and abnormal signals that do not program appropriately. Abnormal signals inlude the splintered and disoordinate signals of severe myoardial disease with ondution disruption or tall R waves that rise in steps (seen only on an osillosope) and are misread by the paemaker as a series of subthreshold signals.64' 65 Late loss of sensor signal ours with partial wire break, insulation tear with urrent leak, malposition to a poor signal area (espeially in transvenous systems where it inludes myoardial perforation with or without phreni paing), a fresh oronary with loss of myoardial voltage, and growth of an insulating EHER sheath around the eletrode. In some radiofrequeny rate-ontrollable R-wave inhibited paemakers, a drop in output ours with an inrease in rate (the disontinued Medtroni External 584 and General Eletri implanted demand pulse generators). At threshold to pae this an result in loss of apture. The obsolete Medtroni 5841, however, may be boosted transiently to threshold by overdrive with its external ontrol (5855). This is speifi for this instrument with failure to pae from battery depletion.63 (3) Failure to pae. In an R-wave inhibited pulse generator this has speial signifiane, as it is totally unreognized in the patient in spontaneous rhythm until that rhythm fails and a bradyardia or asystole results. It is monitored by testing with periodi magneti fixed-rate paing. A-V equential Paemaker A speial paemaker in the R-wave inhibited ategory is the A-V sequential paemaker.66' 67 It uses two eletrodes to pae the atrium and/or ventrile but senses only in the ventrile. In sinus rhythm or onduted beats at a normal rate, all ativity is suppressed. Its sensing interval is from the last ventriular voltage to the next P wave. In atrial asystole, loss of signal, or sinus bradyardia, with a normal P-R interval and atrioventriular ondution, it senses the slow rate and paes the atrium. With P-R prolongation over a preset interval or atrioventriular blok, it senses a delay in ventriular response and paes the ventrile also, providing atrioventriular sequential stimulation (fig. le). Its magneti mode tests ability to pae (paes both atrium and ventrile at a higher rate with a shorter P-R interval) and provides a "ounting" rate for battery evaluation. The A-V sequential paemaker is an exellent onept but, in pratie, it is a omplex paemaker with an inreased potential for malfuntion and a relatively high inidene of trouble.67 ensing diffiulties, ompounded by a short refratory period, result in ompliated ompetition patterns, and selfinhibition (potentially lethal) may our, partiularly in transvenous installations where an atrial stimulus from a malpositioned eletrode may fail to pae the atrium and at the same time inhibit the ventriular stimulus. Battery drain is high (dualoutput iruits and a omplex sensing system), and trouble-free long-term paing is not yet a satisfatory linial reality. Temporary or implanted ventriular paing systems an and are used to pae the atrium irulation, Volume LVII, May 1973

11 Downloaded from by on November 3, 218 TYPE OF PAEMAKER partiularly in atrial dysfuntion or where there is intat ondution, to overdrive the ventrile in a more physiologi, safer approah.687 When the atrial eletrode is applied by thoraotomy, and if, in triggered systems, a high-sensitivity paemaker is used, a stable effetive system results. In transvenous systems unstable eletrode positions for paing and sensing and low-strength trigger signals are the major ompliations for asynhronous or triggered systems.71 Atrial "J" shaped and "barbed" eletrodes are either diffiult to position or not fully immobile. Plaement at the mouth of the oronary sinus offers the best solution for stable paing and for sensing if ombined with an appropriately sensitive paemaker.68 7 ompliations of paing from the atrium inlude late development of atrioventriular ondution delay,68 eletrode displaement with loss of sensing or paing, and synhronization to a ventriular rather than supraventriular signal.69 When the eletrode is deep in the oronary sinus behind the left ventrile, sensing and paing may be of the left ventrile, and sometimes the diaphragm is paed. Two new paemakers, Medtroni 5931 with magnetially adjustable pulse duration and ordis Omniors with radiofrequeny-ontrolled ranges of rate (6-1 beats/min) and urrent (3-11 m, allow flexibility in use and onserve battery drain. oupled with small eletrode tips with low paing threshold, they will extend battery life. They are too reent to be evaluated for speifi ompliations. omments ompliations ommon to all paemakers inlude failure to pae beause of pulse generator power loss (rarely a omponent failure), wire break, or malposition (inluding myoardial perforation and phreni paing).7274 Battery depletion usually is signaled by a rate drop before loss of paing aompanied by hanges in artifat amplitude (drop), duration, and shape seen osillosopially but not on the EG.35 5 Wire breaks, usually aused by angulation or sutures, are very rare in the intravasular portion of transvenous eletrodes. Perforation ours only with transvenous eletrodes, often is signaled by loss of paing, oasionally by diaphragmati paing, and responds to replaement of the eletrode in the ventrile. Tamponade is rare. Paemaker damage by D shok (defibrillation or ardioversion), even of proteted models, may give rise to temporary errati performane Unproteted external units may fail. It is not always immediately possible to asertain whether the pulse irulation, Volume LVII, May generator or the patient's myoardium is responsible for the "malfuntion." It is of note that with all of these possibilities for ompliations most patients and their paemakers oexist in amity and, more important, survive with substantial suess and safety. Referenes 1. ZOLL PM, LINENTHAL AJ, NORMAN LR, PAUL MH, GIBON W: Treatment of unexpeted ardia arrest by external eletrial stimulation of the heart. New Eng J Med 254: 541, WHALEN RE, TARMER F: Eletri shok hazards in linial ardiology. Mod one ardiovas Dis 36: 7, ROGEL, HAIN Y: Inreased exitability of the heart indued by eletrial stimulation in the absolute refratory period. hest 6: HAFT JI, KoOWKY BD, LAU H, TEIN E, DAMATO AN: Termination of atrial flutter by rapid eletrial paing of the atrium. Amer J ardiol 2: 239, BAROLD, LINHART JW: Reent advanes in the treatment of etopi tahyeardias by eletrial paing. Amer J ardiol 25: 698, LILLEHEI W, MoRms TL, BONNABEAU R JR, LONG DM JR, ELLERs RD: Diret wire eletrial stimulation for aute postsurgial and postinfaretion omplete heart blok. Ann NY Aad i 111: 938, HARRI PD, MALM JR, BOWMAN FO JR, HOFFMAN BF, KAIER GA, INGER DH: Epiardial paing to ontrol arrhythmias following ardia surgery. irulation 38 (suppl II): II-178, PARKER B, FURMAN, EsHER DJW: Input signals to paemakers in a hospital environment. Ann NY Aad i 167: 823, EHER DTW, FURMAN, OLOMON N: Transvenous emergeny ardia paing. Ann NY Aad i 167: 582, KILLIP T, KIMBALL JT JR: Perutaneous tehniques for introduing flexible eletrodes for intraardia paing. Ann NY Aad i 167: 597, FABIs F, MOREA M, VINENZI M, FAOLI G, FONTANIN : Failures and ompliations observed in 34 patients treated with temporary and permanent eletri ardia stimulation. J ardiovas urg 8: 11, EHER DJW, FURMAN, OLOMON N, RUBENTEIN B, HWEDEL JB: ine roentgenographi studies on the stability of position maintained by transvenous ardia paemaker eletrodes. irulation 4 (suppl III): III-98, TANREDI RG, MALLITER BD, MANKEN HT: Temporary transvenous atheter-eletrode paing of the heart. irulation 36: 598, NATHAN DA, ENTER, PINA RE, MEDOW A, KELLER W: Perforation during indwelling atheter paing. irulation 33: 128, HANG TO: Perutaneous transfemoral venous ardia paing. hest 6: 73, 1971

12 Downloaded from by on November 3, AMPO I, GARFIELD G, EHER DJW, FURMAN : ompliations of paing by pervenous subelavian semi-floating eletrodes inluding 2 extra luminal insertions. Amer J ardiol 26: 627, WIDMANN WD, GLENN WWL, EIENBERG L, MAURO A: Radio frequeny ardia paemakers. Ann NY Aad i 111: 992, GRAI G, AMMILLI L, BUTTINI, Pozzi R: Radio frequeny ardia paing. Ann NY Aad i 167: 846, ABRAM LD: Indution paing. Ann NY Aad i 167: 964, BARR IM, YERUHALMI, BLIEDEN L, NEUFELD HN: Endoardial radiofrequeny paemaking. Israel J Med i 1: 118, GLENN WWL, FURMAN, ORDON AG, EHER DJW, VAN HEEKEREN DW: Radiofrequeny ontrolled atheter paemaker. New Eng J Med 275: 137, DAVIDON RM, WALLAE AG, EALY W, GORDON M: Eletrially indued atrial tahyardia with blok: A therapeuti appliation of permanent radio frequeny atrial paing. irulation 44: 114, LARK M, EVAN DW, MILTEIN BB: Long term paing with an indutive oupling system. Brit Heart J 33: 65, PILHER J, HEALY MK: The Birmingham (Luas) paemaker: An appraisal of its use. Brit Heart J 33: 375, REORD O, LEIGHT P, UNNING AJ, KENWORTHY- BROWN MJ, RIHING M: Treatment of hroni heart blok with the Luas indution oil paemaker. Brit Heart J 33: 938, GLOARY FOR IMPLANTABLE ARDIA PAEMAKER. J Ass Adv Med Inst 4: 132, FURMAN, EHER DJW, PARKER B: The failure of triggered paemakers. Amer Heart J 82: 28, OWTON E: urvey of long term stimulation tehniques in Great Britain. Ann ardiol Angiol 2: 295, FURMAN, PARKER B, KRAUTHAMER M, EHER DJW: The influene of eletromagneti environment on the performane of artifiial ardia paemakers. Ann Thora urg 6: 9, FURMAN, EHER DJW: hoie of ardia paemaker. Ann NY Aad i 167: 557, OWTON E: Artifiial paemaking and sinus rhythm. Brit Heart J 27: 311, BILLITH M, OBY R, AFFERKY EA: Ventriular fibrillation and ompetitive paing. New Eng J Med 276: 598, NATHAN DA, ENTER, WU, KELLER W: An implantable synhronous paemaker for the long term orretion of omplete heart blok. Amer J ardiol 11: 362, DODINOT BP, PETITIER A, GILGENKRATZ JM, FAIVRE GR: inial experiene with atrial synhronous paing. Ann NY Aad i 167: 138, FURMAN, EHER DJW: Priniples and Tehniques of ardia Paing. Hagerstown, Maryland, Harper & Row, 197 EHER 36. MYTH NP, BAU AP, BAO JM, MAUMI R, KEHIHIAN JM, BAKER NR: Permanent transvenous ardia paing. hest 59: 493, VOGEL I, DRELER L, WITTE J, WARNKE H, PORTMANN P, HALDAH M: Atrial synhronized paing using a new transvenous tehnique. Ann ardiol Angiol 2: 381, ARLEN E, JOHANON L, KARLOF I, LAGERGREN H: New method for atrial triggered paemaker treatment without thoraotomy. J Thora ardiovas urg 5: 229, FURMAN, EHER DJW: Ventriular synhronous and demand paing. Amer Heart J 76: 445, ATELLANO A JR, MAYTIN, LEMBERG L, BERKOVIT BV: Ventriular-triggered paemaker arrhythmias. Brit Heart J 31: 546, OHEN I, MORKIN E, AROETY J: ompetitive rhythms with synhronous standby (demand) paemakers. Amer Heart J 79: 332, BAROLD, GAIDULA JJ: Evaluation of normal and abnormal sensing funtions of demand paemakers. Amer J ardiol 28: 21, BAROLD : inial signifiane of paemaker refratory period. Amer J ardiol 28: 237, BERGER RA, Ross M, NATHAN DA: Paer premature beats: A manifestation of malfuntion. hest 61: 48, EHER DJW: The The treatment of tahyarrhythmia by artifial ardia paing. Amer Heart J 78: 829, ATELLANO A JR, BERKOVIT BV, Fox R: QR triggered paemaker and arrhythmias related to early systoli stimulation. Ann ardiol Angiol 2: 485, LEMIBERG L, ATELLANO A JR, BERKOVIT BV: Paemaking on demand in AV blok. JAMA 191: 12, BAROLD, GAIDULA JJ, LYON JL, ARROL M: Irregular reyling of demand paemakers from borderline eletrographi signals. Amer Heart J 82: 447, HENG TO, HAITHIRAPHAN, BALTAZAR A, HAEN MAZ: uppression by a prominent T-wave: An unusual ause of malfuntion of a transvenous demand paemaker. hest 6: 52, MAUMI RA, MAON DT, AMTERDAM EA, ALEL AF: Apparent malfuntion of demand paemaker aused by nonpropagated (onealed) ventriular extrasystoles. hest 61: 426, LAETER K, BUHANAN J, YAHONIs K: A mehanism for "false" inhibition of demand paemakers. irulation 42: 193, NEVIN MA, LANDAU, LYON L: Failure of demand paemaker sensing due to eletrode frature. hest 59: 11, WIDMIANN WD, MANGIOLA, LUBOW LA, DOLAN FM: uppression of demand paemakers by inative paemaker eletrodes. irulation 45: 319, OWTON E, GRAY K, PRETON T: Eletrial interferene in non-ompetitive paemakers. Brit Heart J 32: 626, 197 ir ulauion, Volume LVII, May 1973

13 Downloaded from by on November 3, 218 TYPE OF PAEMAKER 55. RYTAL RG, KATOR JA, DEANTrIs RW: Inhibition of disharge of an external demand paemaker by an eletri razor. Amer J ardiol 27: 695, WAJZZUK WJ, MowRY FM, DUGAN NL: Deativation of a demand paemaker by transurethral eletroautery. New Eng J Med 28: 34, PIKER BA, GOLDBERG MJ: Inhibition of a demand paemaker and interferene with monitoring equipment by radio frequeny transmissions. Brit Med J 2: 54, YATTEAU RF: Radar-indued failure of a demand paemaker. New Eng J Med 283: 1447, KING GR, HAMBURGER A, PARA E, HELLER R, ARLETON RA: Letter to the Editor: Effet of mirowave oven on implanted ardia paemaker. JAMA 193: 199, MEIBON J, ANDERON JD: Inhibition of demand paemaker by leakage urrent from eletroardiographi reorder. Brit Heart J 33: 326, MITHELL JD, RUTAN PL, FRAZER JW, HURT WD: Eletromagneti ompatibility of ardia paemakers. Pro IEEE. In press 62. TREVENO AJ, BELLER BM, TAILEY R, PUPILLO GA, LINHART JW: hest wall stimulation: A method of demand QR bloking paemaker suppression in the study of arrhythmias. Amer Heart J 81: 2, EHER DJW, FURMAN, PARKER B: Letter to the Editor: Emergeny management of failing paemakers. Amer Heart J 82: 717, HATTERJEE K, UTTON R, DAVI JG: Low intraardia potentials in myoardial infartion as a ause of failure of inhibition of demand paemakers. Lanet 1: 511, BAROLD, GAIDULA JJ: Failure of demand paemaker from low voltage bipolar ventriular eletrograms. JAMA 215: 923, ATILLO A, BERKOvITZ BV, ATELLANO A JR, LEMBERG L, ALLARD G, JUDE JR: Bifoal demand paing. hest 59: 36, FURMAN, REIHER-REI H, EHER DJW: Atrioventriular sequential paing and paemakers. hest. In Press 68. KRAMER DH, Moss AJ: Permanent pervenous atrial paing from the oronary vein. irulation 42: 427, DEANTI R: Diagnosti and therapeuti uses of atrial paing. irulation 43: 748, MYTH NPD, KEHIHIAN JM, BAO JM, MAUMI RA, FLETHER RD, BIOVIN MR: Permanent pervenous atrial paing. J Eletroardiol 4: 299, NATHAN DA, LITER JW, ATILLO R, KELLER WJ, GOELLIN A: urrent status of atrial paing. Ann ardiol Angiol 2: 451, OBY R, PENDo JRF, OTTON BH: atheter perforation of the ventrile after intraardia paing. Geriatris 22: 182, BmH LM, BERGER M, THOMA PA: ynhronous diaphragmati ontration: A ompliation of transvenous ardia paing. Amer J ardiol 21: 88, PELEKA B, BUDA J: timulation of the phreni nerve as a ompliation of implanted battery paemaker: Management without thoraotomy. J ardiovas urg 6: 477, FURMAN F, EHER DJW, PARKER B: The paemaker follow-up lini. Progr ardiovas Dis 14: 515, GIEDWOYN JO: Paemaker failure following external defibrillation. irulation 44: 293, PARONNET V: Letter to the Editor: Paemaker failure following external defibrillation. irulation 45: 1144, LAU FYK, BILLITH M, WINTROUB HJ: Protetion of implanted paemakers from exessive eletrial energy of D.. shok. Amer J ardiol 23: 244, 1969 irulation, Volume LVII, May 1973