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Direct electrical cardiac stimulators
By SaM E. ST~.':J,mcasox, J~. It. V~ALSttE in 1862 ~ s u g g e s t e d that ex~2rnal control of c a r d i a c rate . might b e feasible in the future, Zo]l a n d eo-wolkers . in t h e early part of t h e lmSt d e c a d e ploncelwd the c o n c e p t of external e x t r a c a r d i a c paccmakir~g " n t s to s h o c k s o f v a r i a b l e v o l t a g e apphe< bv. s u b j e c t i n g the p a t m ' " l across t h e intact Chest w a l l f r o m e x t e r n a l e l e c ~ o d e s .
This method
is i n v a l u a M e in s o m e
cases but if p r o l o n g e d p a c e m a k i n g is r e q u i r e d t h e r e is a n e e e s s a W s t e p - u p in voRage which m a y at times reach s u ~ c i e n t m a g n i t u d e to c a u s e t e t a n i e c o n tractions o f t h e entire b o d y muscle mass associated w i t h e a c h s y s t o l e . Zoll a n d c o - w o r k e r s ~ h a v e f a i l e d to d e m o n s t r a t e a n y d e l e t e r i o u s effects o n the h e a ~ f r o m t h e e×ternal p a c e m a k i n g . T h e y d o state t h a t skin e r o s i o n s u n d e r
the electrodes m a y pose a p r o b l e m b u t this can be h a n d l e d satisfactorily b y frequent changes of e l e c t r o d e position. l:~eiff et al., r" however, have r e p o r t e d t h e deveto~mOntl ~ of a p e r i e a r d i a l h'iclion r u b and imtops 5 findings of p e r | c a r d | a t a n d e p i c a r d i a l injnry followh~g external stimulation, Bose a n d \Vartomik': also describe miM pcriearditis in a patient who h a d |)eez~ st im~llate(t i n t e r m i t t e n t l y for 46 days. I t is not lhe p ~ r p o s e of t|~is papox, how(~.-,'er, to deal with tim use c,f external p a e e m a k i n g t h r o u g h the intact chest. A c o m p l e t e review of t|ds as.i~eet of the p r o b l e m is given by Zolld Snf~ee it to s a y tlmt as vet w e do nc~t h a v e the complete a n s w e r as to w l w t h e r sti~ml|ation {hro~gh the intact chest or b y d i t t o , my~cardial electrodes will be the final answer. It wo~tld seem nt the pr(,senl time tha~ each me/lind has its distinct area for applica~hm. llecenl a d v a n c e s in the field ~ff direct electrical s t i m u l a t i o n througt~ elee~r~dc,s in or on ~he h(,art h a v e r e m e d i e d s o m e of t i~:• ddBc~ltms " ' " i n h e r e n t with external 0leclrodes but have created a n o t h e r g r o u p of p r o b l e m s wl-,ich wil| b e ¢tise~ssed i~ m o r e detail later. T h e r e are at pres~,nt ~wo large groups, of p a t i e n t s u p o n w h o m intermitten~ ~r sl~;n'~ term c a r d i a c I a c e m a k m ~ may. be lifesaving. T h e s e are patients s~tffering from the Stokes-Adams s y n d r o m e mid post-extracorpc~real p c r f u s i o n Datient~. especially those patients (~porated f~r t e t r a l o g y of Fallot or intervm~tricnlar septa| deh,ets, w h o r e surgical m a n i p u l a t i o n s have c a u s e d a com~I~,t~, a~rioventricu|ar dissociation. T}wre is e v e r y indication that a l i t t l e r a n d m o r e v a n e d ~ r o u p of ~alients will |)e c a n d i d a t e s for e x t r a e a r d i a e s t i m u l a t i o n in tim f~ture arid t h e r e f o r e er~deavors in this fi~,lrl will prr~hal~|), hav~, a veider area r~f a oplica tirm. This discussion will deal with dir~,et electrical stim~dation of the }tem't b y the variety r)f m e a n s now a v a i l a b l e clinically, and experimenta|tv.~ T h e a'~lv a n t a g e s and s h o r t c o m i n g s of each p a r t i e t d a r t y p e eft s t i m u l a t i o n will })e disr'~ssed ,ruder the respective headings. Frfm~ the S. I|udotph Idght l..aboratt~r!t Jor F,ur~ic~d ltv~.arch. D,'~mrtment o/ Nur~er!t.
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m a y i n t e r f e r e w i t h r e s p i r a t o r y f u n c t i o n b y t r i g g e r i n g tim d i a p h r a g m a n d hilly a c t u a l l y rectch t h e stal:c, whicl~ t h e p a t i e n t m a y b e u n d e r g o i n g a t.etanic seiz~lrc w i t h e a c h v e n t r i c u l a r c o n t r a c t i o n . T h i s res,dts in r a t h e r r a p i d cxhau...,ticm of t h e p a t i c n L T}mse d i s a d v a n t a g e s a r e not p r e s e n t , h o w e v e r , in all t h e a p p l i c a tions b u t b e c o m e m o r e p r o n o u n c e d as t h e l e n g t l t of s t i m u l a t i o n or n u m b e r of episodes of s:timulation increase. There appears both experimentally and clinically decreasing responsivenes~ of t h e m y o e a r d i , l m to s t i m u l a t i o n w i t h e i t h e r d i r e c t or i n d i r e c t c¢;rltrol. "l'ltis necc.ss ty to i n c r e a s e .stimtilatir,~-,,.._. v ~ l i a g e s t h e n is a p r o h l e m of ~,xtracardiac p a c e m a k i n g regardlc'ss {~f t h e m e t I m d e m p l o y e d . T h e a d v ; u l l a g ~ of d i r e c t ~dccti-ical s t i m u l a t i o n is thai< t i m e l e c t r i c a l f o r c e Caiil 1)Onsider i r t d i v i d u a l t v . 7"111"(7~ot)f lhf.sf~- ltiCtill)(is dopon~t ~m the f*lll|)iric/il ~.~lli-lr<)l Of c a r d i l i c r a t e l)v an a r b i t r a r y s e t l i i l g o f {tie +):ci:illatc~r clrc~lil Mild ~tilfer l ) r i l i l l i r i l v ill t h e inelh~ i|it: tliVti('ill'ditlill+ "]'}i¢" f
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I. "['IiANNf;IUT:%.Nt-;()t~S I)IIII~(:T .~-~'I'I).IULATIC)="; T h e e a r l y w o r k o f i r r i p l a n t i r i g w i r e e h : c l r o d e a a n d i i t i l i z i i i g an ~,xtei'nat ] ) a c e I i l ; l k / ' r ~.vils pif)noer,.'{l l~V \ V e h ' i c t l ~ "tvflrkill~ w i t h f A l l e l l e i ' s igro,tp al t]u- ( ' t l i . v('rsitv, ill" ~.[inrl(,Sf)lii+ P r e l i i l / i r l ; i r v rosll]ts o|" this illl)~ro;ictl were: t'lros~,~l,'d at if t llo (;'lilii{~lil (,l)ll~riiNN f:lf tilt' A l l l l ' r i ( ' i i i l (.,olh'gl" ,if ~ttr~l:#tlts irt .I ,{I57. "l'tiis w o r k w a s ~ r i g i n i t l l v tllid<-l-titk(,ll li) lrf2~ll l ) O S l s l i r ~ i c a l lit,art l t t o c k f,.tlb>wing ,ll)t'li ('ili'(titilL{llliV. "I=he rl;.~iills tl'lJl't" illllStaiTl(liilg w i t h llu" s a h ' i l g e (~f a lar~,;" ~ I t i i l | i '>{ i m t h , , l i s xvlio ,:¢cri' s l i l n u h i t c i l frolrl p e r i o d s of ii f e w |loi,r~ i,i ~ ) l l i ' tri~,ltllt T h i s lilt;lilt>el i)f COl:ill'O] , , t i l i z e d t i m ilrtpla~ilali<~lt t)ir ii si,i~],' illSllJlill-~| ttir~' ~,h'~.tr~l~h" ili ltit, vi,iilric-til~ir l~lvocar{lilliifl ailtll ilia: ~lll;i(-}illil,lil ~lt ~l Lrr~t~iil~t ~.lt,cll'o(h~" to lhl'. Cilia'st w a l l . A {~:oirimerciltllv a v a i l a b h : |);,i(:f}ll~i;lkl'r i;'a tilt'it ~tll;lc, h o d IO these: l n l v i n ~ eleetr<~des a n d v f ~ l t t r i c l l | a r r a t e set b y t}i¢~ p l i ) ' s i c i a l / . T l i i s ili)i)r(iglch rl'SliilS iltl il w e l l ll>cali~.od i m p u t s c {,if r+,ialivl-ly I~,w l l l ; i ~ l l i l l i f i t : (,I-:2'I v~tll~) ;111¢1 it is ]t!lssibh" ] i v iltl:rlqisillt~ till" v~>lla~e b y .~lila!l i i l t ' r t ' l l l l ' I t l ~, l l i l i i a i l i l i l i l l " s | i l l i l l t l i l i t l l t }iv tliis rllal'llit'r ill) l~l trOllr %vf,l'k~ ; l l l l i l)t,~sibh" ~t l i l l l , ' l(m~er. t
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T h i s b a s i c w o r k ~ i~tchlded cx) e1r i m e n t a t . evahiatio~'t of t h e l I m l h o d olJ a'~lireals. P e r i p h e r a l l>ressure a n d c a r d i a c outl?tit xver¢~ cte.ternfincd a n d il w a s d e m o n s t r a t e d t h a t a ~ ) - 5 o p e r cent r e d i l c t i o n irJ c . u t h , m {mtpl~t o c c t i r r e d w i t h surgicvll d i v i s i o n of the m a i n e o n e h m t i o n p a t h w a y s . T h e c a r d i a c outp~lt couh:! q u i c k l y b e r e v e r t e d to 95 p e r cent to 167 per cent of n o r m a l b y d i r e c t stilnillation in t h e r a n g e of 90 s t i m l i l i a r e | m i t e ilt spih~ of the: fact t'hat t h e a n i m a l s " p r e b l o c k p u l s e rate h a d b e e n c o n s i d e r a b l y h i g h e r , l,lt, an a ! t e r i a l p r e s s l i r e w a s also fom~d t . . t ~ p r 0 a e l J n o r m a l w i t h s t i m u l a t i o n t h r o u g h t h e s e i m p l a n t e d w i r e electrodes. If o n e c o n s i d e r s t h e u h h n a t e il, d e s i g n of a c h r o n i c e x t e r n a l s t h m i h i t o r t h e s h o r t c o m i n g s of this m e t h o d a r e r e a d i l y a p p a r e n t . ( 1 ) A n i n l y i n g e l e c t r o d e t x a v e r s i n g t h e skin b a r ~ e r . ( 2 ) T h e p o s s i b i l i t y of b r e a k in c o n t a c t B e t w e e n e l e c t r o d e a n d p a c e m a k e r from p a t i e n t m o v e m e n t . ( 3 ) P o w e r failure. ( 4 ) I n a b i l i t y to a e c o r n o d a t e o u t p u t hyperpyrexia, and ambuia~on. ( 5 ) F i b r o s i s cff t h e r n v o c a r d i u m at tim site of eleeir¢~r]e p l a c e m e n l . 11. ]:,l!'l.aX'rlT:O PAf:I:2%IAKt:~Ii ]7]NI~:fIGIZF.I) tlY I;]X'I'I{ItlNAL POVi'l~ll ~IIgLI) S!.,nning *' avid t h e g l x n i p ilt S t o c k h o l m d e v e l o p e d a n o t h e r il]gelll()llS m e t h o d +>f d i r e c t s t i m u l a t i o n , it s m a l l transi;stor tlnil w a s d e v e l o p e d w h i c h Xv ~iS - , ;tttacli~.'tt If) the }i~etirt l~y tvh'(, +~h:etrodes and was iml)hintod, s u b e l i t a n c o t i s l y iri til(~ epigastriuii'i. T h i s ill|it is then ermr~izel] by ari e x t e r n a l l y l)[aved p o w e r field f r o m iiri in(liiction coi| ilicorporate{t irl a lJ~,lt w h i c h earl }}~:, i}lace{l a r o u n d tim p a t i e n t . li is r~:ported that this m e t h o d was u t i l i z e d in a single c l i n i c a l case w i t h %Iflll]ll;f SflCI21t-SS. Tile: d i f f i c u l t i e s i l i h e r e r l l w i l | l all rrietliods l i t i l i z i r l g d i r e c t w i r ( : ~:|ectr+~¢tes sool~ l)i2ciilrtt..> a p p a r e n l h o w e v e r . T h e lll2/t,~;llr(titllll t)f'(:f)I~{::g !)rfl~rvssively irl:-;elisitivt* 1¢1 s t i m ~ i l n t i o n nrld x'olta~('s lrlust t)e iric-reas¢:~l. \ V i l h this p a r t i c t l l a r nrralll~eErlellt,, u l i l i z i n ~ lira e,'xt(,rihl|, * p o w e r field, the pli/i¢.n! tl~itfis t~ rt,spoitd iri l,.'tlol~: tf) th~ s l i r i / l i i l i s as vo|tat{os ~irf~ iricreased. T h e r v b; a d i s l i r i c t ; i l l V a l t l a ~ f ' ill /his typf: , d s l i i l i l l l a t i O l i , }tow~vcr. ilt lhat lli¢~r~e is rio break in tht, .';ki~ t } a r r i o r alitl t h e p o s s i h i l i t y We I :]X'I+I,;II."JA 1. ']'lte% ?,;S XI IT*I+t-;II (;1¢.~Itli
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rt)lindpd b y a c o l l e c t i o n of c r e a m y m u t e r i a l wlfich w a s fc.it~tt to b~- sterile (m ~-~dturc'. "llte stimlll~tting v()ltages art: ot low rlt;,~idt~(h: ar,d ar~, al>plie(l (tirv(.t-. ly It* t h e }le;trt, "I'ltt: i i ] c r e a s i n g r~esislarlc~, o| Ill,- ~lix'o(:ar(litiirl | o stimtllatiol~ ti)r()~,~ti t | l e irtll)lar, t(:t[ w i t , . i.'~ pre.~,.i~l wilt* |hi.', r r w t l , ~ d i~'; w i t l l ~ltllers. }itixv0 vLq-. C e r l a i n m o ( i i f i c a t i ( m in e l e c t r o d e e~n,s/ril(:tir>li iri ;,ss()¢:ialit)t, w i t l l t h i s ~l~it ar~" ~ifiv.; } ] e i t i ~ e v l i h i a l e l ] })v Nlliiti'o. "|'lit'S(' ~il't' ~l('siKl.'(, Iil)erat(~'d at lli(~' l . i ( . c l n i ( h . . l i r c o c a r ( l i ; l l iilii(-li(>ii. " l i i i ~ "l~h,.ckink~" (.h..ctrt~dv w o r k s well ill $]tort f('rlll l.-.|)(,riill~.lil~ i>,ii ;t~ vt-t l . i s li<,i b(.~.lt f , , l l v l.-¢;ihililp(l fJrl ~t i o l t < ~ t('l+lll illisif;, l:: IV.
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l"h~, o t / - . r a p p r . . c h 1o l h e p r . l ~ l e m ~Jt" c~mtl:,let~" tsearl l ) h . : k has l.,('n lh~~llili~..;tlicm o f l|i(" ; ~ l r i c ~ d a r p -.v~lve to l r i ~ g ( ' r a n d l i m e an p-.ien~.~| ~ l i m i d a h ~ r . T h i s m e i l . M w a s firsl r e p o r t e d b v l ' ~ d k m a . ;,lid ~.V;ttkflls ~ :rod ;~ c:,ri;~,~l ~ t tllis b y l l - " , , l h o r ' s g r , u p ~:~ ( f i g . I "~. t r e a h n e t t | ~if l|i¢" i d i o v ~ . . i d r i c l i | i i r r l w l | m t ~tf ] w a r l i ) | , c k . . ~ merry |~l~}~i~d~ic;~l ( < t t l l r ~ l (~i tll~- ~.;trdilw r i d e . . v , l i l d b~. l~referabI~ ". "I'l~i~ w~.~l~t p~.rniit ;t v;~ri:~bl, c a r d i a c o l l l l ~ i i l ilt n ' l a l i o i l to I ~ h v s i ~ l ~ k i d . t~if~ell~.mic:ll ;~ll(I l~h>~i~--I ~1~'~..~-~ ~ f pt~.~/of->eraliv~, r e e ~ w e r v ~md n o r t n a I (.:;ercise~ coml>li~:;fled a n d r e q l d r t : s t h e ; l ( l d i i i n n ~)f ~m ; m r i c l d ; t r r h . c i r o d e . T h e i m l m l s e f r o n i tli~: a i i r i c | e in f e d i n t o a m u s c l e p o l e n t i a l a m p l i f i e r w h i c h hz, s p r e v i o l l s l y b e t : n dr..scribed ~-~7 a n d , , s e d t o t r i g g e r ~ ¢orwe.rititm;,l s l i m u l a t t . . Experimtmh,] e v . h . l l i o n h~s bet,li r e p o r t e d b y lin :~ nlltl h:ts l . ' . ' , t(.~.+l f,, qitleklv r e s t o r e t.:mttdy~i.~mfie t.quilibrium (fig. 2), At tltv |)re~;,,ltt fillip ;I lr~lmiishlriz~'t| !rail is | ) t ' i l i l ~ ;~,.! d ~ t , . h t
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l:ig. 2 . ~ C ( m l p a r i s o n b e t w e e n p-wave and c o n v e n t i o n a l sthnuh~tor in regard t~ cardiac o l l [ l ) U l s o b t a i n e d after surgieaIly d e s t r o y e d e o , d , e t i o i t system.
sdv~* ~hc pr(~blen~ (~f ~he i~I~it being p~-'t~t}~h' ~mtl :,~na]l et~(~l~gl~ l~ fit hi the path,m'~ shh't |mcl,:et T h e llse of the al~ric'ldar h~I>l|lsc tn irim~t.r ar~ external .qim~dahn" tins t~.t~) lIm~k~Jlt b y s~mle (o lx" imlmlelical d ~ e to t|lc ~lnricutm" ladrvca,di;m thai acc o m p a n i e s an idiovei~tric-uhlr r h y t h m . \ V e have f o u n d tllrc)ugl~ experimt, l~lal applicati(m thal the a u r i c u l a r rale r a p i d l y lt,v(~rls [o n o r m a l with adeq~mie ventric~llar slimulalitm. ()rio possible c()n~l)licati()l~ ()I" this m c t l l o d ()f stim~llaIion .eolthl be the dev<.lopmer~t of am'ic~llar fibrill;il:ioli w i t h rcsultm~t faiai m ' r l } v t h m i a . For this rcas(m a blocking circlli( is ~" n c•l ~ ( 1.t.~ l in the ,,nit to t m ' ve~lt s t i l m d a t i . n from (~ccurring m o r e r a p i d I y than l.i0 p e r m i n u t e . A m a s t e r r~scilhtm" is ;~lsr) i n c l m h ' d in case ¢~f t'lti]llr(, o[ th(' allriclllar pick-.l~, Tills unil as previoiisly descrilxxl in tile lilcratm'e lind the s a m e d i s a t l v a n t a g c as (~[her metht~ds 1)ut at the present time is apl'died v.itliollI th¢' direct s~blr(" (~f ('hcliod(.' • " .s tf:~ lho mvocardium.. By passing<, a do~bl¢: e l e c t r o d e c a t l . , l e r llmjug)~ a peripht, ral vein i/lit) the ri,Rl-lt a i r i m n with tlw tip e x t e n d i n g thrt)ugi~ the trie~ispid valve into tile right ventric~llar c.ix"":t'~ '~, p i c k - u p :rod sliinlilalion caii t . , ac(..(mlI~lisl-led. This rneth()d ¢If ( . h ' d r ( . l e phlc(~menI uIilizcs Ihe norl~ial rh.ctrical c ( m d u c l i v i t y of Ihe blo{~d a n d in lhe eXlX~rin~elltal a n i m a l s }l~s noI giv(,~l rise I~ e n d o e a r d i a l tl|)rosis, tliromb(~sis . r l i e . ~ o l y s i s . T h e ~ls(' o f ;t similar single ¢~theh.r has l)ren n T m r t e d b y lh~rm;m a n d S e h w e d e l . t''
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D ~sct~ss i o~ F r o m tim p r e c e d i n g d c s c r i p t i o r i s of t h e p r e s e n t a p p r o , c h c - s to dirct:t card iltc' stimutalio~) o n e is i m p r e s s e d b y t h e il)got~Jotls d e v i c e s tidal can l)~. dex.'clCq)ed to so|w: a pg, r t i m d a r problerr} t h a t c o n f r o n t s ~ts as p h y s i c i a n s . . M o s t ()f timse : t p p r o a c l m s h a v e t)een ~nadc possit)h: only lhr(,tgf] tim c-()Ol}crative eliortx ~I the pltysiologist, m e d i c a l e l e c t r o n i c s e n g i n e e r ;in(1 the pt~ysician. .iettrtt~cr i n s t r t t m e n t a t i o n in this fiehl is rapidly" b e i n g devclopc¢l tllrottgl~ tlmsc tcarl~... of r e s e a r c h invest:igators. At t h e t i m e of w r i t i n g of this s t u n m a r y the o n l y u n i v e r s a l l y a v a i l a b l e t y p e of s t i m u l a t i o n is t h e e x t e r n a l u n i t w h i c h can b e c o n n e c t e d to the m v o c a r d i u m b y o n e of t h e v a r i o u s t y p e s of e l e c t r o d e s . T h o ~ g h t h e o t h e r units have. all b e e n a p p l i e d clinically most are still ~ n d e r g o i n g f u r t h e r e x p e r i m e n t a l evn]lmtion. T h e a v a i l a b l e c o m m e r c i a l units can b e a p p l i e d t h r o u g h t h r e e m e t h o d s r.~f e l e c t r o d e p l a c e m e n t . If t h e c h e s t is o p e n an e l e c t r o d e c a n b e s u t ~ r c d d i r e c t l y to t h e m y o e a r d i u m . T h e t y p e o f e l e c t r o d e c a n b e citl~cr at co~n~wricatllv availa b l e (mc w i t h a s w e d g e d - o n needh.." a n d a l r e a d y ins~date(l; ~,r ~)~(. ,.:an I,~~ shrtp l y c c m s l r u c t e d f r o m s t a i n l e s s steel (:al~h.."w i r e m~tur¢' i~sil~g fine l)(dyethvle~(" ot teflon t u b i n g for i n s u l a t i o n . In t h e s('a'ir~l]slv ill p a t i e ~ t ..vlwr¢. tl~,r:~cot(,r~v w~n~ld l~e p o o r l y t o l e r a t e d a 16 Io 18 ~;tR,r r,~.~.
TI~' f o l l o w i n g tn~tline m a y lm h e l p f u l I(~ t l m s e lu,(l~,rlaki,~t{ ¢tir(,ct citr~tia(. ~timtdati~m. It is w i s e for caol~ .~rocq~ t¢~ ,.loci tl,,. t>'p~" of ¢,l~,ctro, h- ~)]=,(-,.m,'nl Io t~e ~,lilizod w | m n tll(: n e e d ~)f pacelt~akirJ~ |wcorno~ al)l)~lr¢'~t. "Fl..s~' el¢'cIr(~d('~;
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ft. Place the ground electrode t o the patient, preferably by . utm(,, and connect this to the pac-enaaker. 3. Attach active electrode to pacemaker which has b e e n warme(l up (stand: by position ). 4. Adjust voltage so that minimal voltage will cause ade(:luate• vel)tricular c o n t r a c t m , , . This can be determined b y the retma~ of adequate peripl~eral pressure. 5. Rate slmuld be set at 8 ~ 1 2 0 stim,0i per minute to maintaiI, -'--!equate pressure. 6. Attempts to wean the heart from the stimulator should be made frequently to determine whether the normal mechanism of rate has returned. O n e m u s t be conscious of the fact that after stimulation a c o m p e n s a t o r y asystole lasting from 2--5 s e c o n d s usuMIy occurs prior to the first v e n ~ i c u l a r complex. St.rM~tarty I. Direct cardiac p a c e m a k 6 n g can be a c c o m p l i s h e d b y a variety of m e a n s at the present Nine and can be lifesaving to a large group of patients. 2. ~ e available clinical and experimental a p p r o a ~ e s to direct stimulation have been described. 3. The ul~mate in pacemakers is not vet available but experimental work is underway to produce a more physiological transistorized m~til capable of reproducing all aspects of the ,mrmal electrocardiogram.
1.
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BEFERENCES \Valshe, XV. It.: A practicM treatise on disease |~e external eleclric stimu|adise:ases of tile, great vessels. Phila{iOn. J.A.~\I.A. 359:10!5, 1955. d d p h i a . B ! a n c h a r d a n d Lea, 1862. 7. Zol]. IL M.. Panl, Xl. H., Linenthal, A. Zotl. P_ M.: Resuscitation of d u heart J., N o r m a n , L. R-. a n d Gibson. "~V.: in ventriculur standstill b y t x t e r n a l T h e effects eft external ~ e c t r i c curelectric stinmlatkm. N { w gr, gland J. rents on t h e heart. CireJ.datkm 14: },led. 247:768. 1952. 745, 1956. ~ , Linenthal, A. J., (libson, \V.. Paul. 8. \Veirich. X\'. L.. Gott, V, L., and LiIle,M, H. a n d N o r m a n , L. It.: T e r m i n a hei, C. \V.: T r e a t m e n t of c o m p l e t e -tion eft ventricular fibr~lation in m a n heart block |~y c o m b i n e d usv of myob y exttwnally applied e | e e t r i c c~nmtcardial d e c t r o d c a n d artificial pac,,erslmek. 4New E n g l a n d .l.Med. 25-& maker. ,q.Kor~m~ 8:360, 1957. 727. 1956. ~k S e n n i n g , A.: Discussion of p a p e r by . a n d N o r m a n . L. R.: Treatme~lt SleDhenson e t a ! . J.Thorack~5¢ Cardioo o{ Stokes-Adams disease b y external vasmdarSurg. 38:638, 1959. electric stimulatim, of heart. Cirellla10 Glenn, "~V. L., ?}lauro, A., L o n g o . g.. lion 9:482, I954. Lavietes, P. H., and M a c k a y , F. J.: Reiff. T. R.. Oi~penheimer. J., and R m n o t e stimulation of the h e a r t by Ferguson, C.: Cardi:m injury preradio/requeney tra r~smission. New stmmbly d u e to ,,se of tile external g n N a n d J.Med. 261:948, 1959. electric cardiac p a c e m a k e r in Stoke.~11. M a u r o , A.: T e c k n i q n e for in situ stimAdant~ disease. Am.HenrtJ. 54:437, ulation. Yale Biophys.Bull. 1:2, 1948. 1957. 1:2. ~ , Wall, P. D., D a v e y , L. M., and Rose.. l.. 13. and ",Vartoniek, %V.: T r ~ t Salter, A. M,: C e n t r a l n e r v o u s ~timu. meat ~ff a ca~,, ~ff Stokes-Adam~ lalion hy i m p l a n t e d h i g h freqlleney
IH1H~CT ELECTI{I(~AL (;A!{DtAI~ STI.~,IUI.,A'I'OI~S
,edivcn. Fed.Prec. ,9:86, 1950. Persotaa| eommm~icatiou. N o v e m ber. 1959, l-l. FolkmmL M. J., and \Vatkin,~, E.: An artificial condtmtlm~ system for lilt: Inatl;lgemt;tlt Of coreD|ere heart h|ock. &Forum 8:331, J958. 15. Stephenson. S. E,, Jr,, Edwar(ls, \V. I'L, Jolly. P. C., and Scott, H. W., Jr.: Physiologic p-wave cardiac stimutat~ar. J.Tlmr. CardiovaseularSurg. 38: (~M, 1959. 16. ~ , Bats(m, R,, Nh)ntg~m~cry,. I.,. H., Ymmg, W,, Clark, S, L., and t)aniel, R. A., Jr.: PiLvsiMogical control of rfrspiration during experimental thor13, ~ :
~cotomv. BulLSoc.Interuat.Chir, I7: 32O, 1958. 17. Bats~m, R, Morag, mi~ry, L H., Beisd. L If.; McCrosky, 1)., and Clark, ,*g~ L.; Electronically vomrolled r~4pir.a* tor, Science t2{):815}, 1956. 18. Stephenson, S. E.. Jr., J,dly, P. C., Bailey, tl. \V, Edward~, \V. |t., a,~d Montgomery. L. [1.: Eva|~alkm at tht- p~wave exlernaI cardiac ~timulatot. S.l-'orun'~ IO:(~IE, It)60. l.q. Furman, S. and Sch~ede|. J. B.: A:~ infracardiac pacemaker f~r Stokt>. Adams seizures. New England J, Med,, 26I:9.13, 195.~J.
This method
is i n v a l u a M e in s o m e
cases but if p r o l o n g e d p a c e m a k i n g is r e q u i r e d t h e r e is a n e e e s s a W s t e p - u p in voRage which m a y at times reach s u ~ c i e n t m a g n i t u d e to c a u s e t e t a n i e c o n tractions o f t h e entire b o d y muscle mass associated w i t h e a c h s y s t o l e . Zoll a n d c o - w o r k e r s ~ h a v e f a i l e d to d e m o n s t r a t e a n y d e l e t e r i o u s effects o n the h e a ~ f r o m t h e e×ternal p a c e m a k i n g . T h e y d o state t h a t skin e r o s i o n s u n d e r
the electrodes m a y pose a p r o b l e m b u t this can be h a n d l e d satisfactorily b y frequent changes of e l e c t r o d e position. l:~eiff et al., r" however, have r e p o r t e d t h e deveto~mOntl ~ of a p e r i e a r d i a l h'iclion r u b and imtops 5 findings of p e r | c a r d | a t a n d e p i c a r d i a l injnry followh~g external stimulation, Bose a n d \Vartomik': also describe miM pcriearditis in a patient who h a d |)eez~ st im~llate(t i n t e r m i t t e n t l y for 46 days. I t is not lhe p ~ r p o s e of t|~is papox, how(~.-,'er, to deal with tim use c,f external p a e e m a k i n g t h r o u g h the intact chest. A c o m p l e t e review of t|ds as.i~eet of the p r o b l e m is given by Zolld Snf~ee it to s a y tlmt as vet w e do nc~t h a v e the complete a n s w e r as to w l w t h e r sti~ml|ation {hro~gh the intact chest or b y d i t t o , my~cardial electrodes will be the final answer. It wo~tld seem nt the pr(,senl time tha~ each me/lind has its distinct area for applica~hm. llecenl a d v a n c e s in the field ~ff direct electrical s t i m u l a t i o n througt~ elee~r~dc,s in or on ~he h(,art h a v e r e m e d i e d s o m e of t i~:• ddBc~ltms " ' " i n h e r e n t with external 0leclrodes but have created a n o t h e r g r o u p of p r o b l e m s wl-,ich wil| b e ¢tise~ssed i~ m o r e detail later. T h e r e are at pres~,nt ~wo large groups, of p a t i e n t s u p o n w h o m intermitten~ ~r sl~;n'~ term c a r d i a c I a c e m a k m ~ may. be lifesaving. T h e s e are patients s~tffering from the Stokes-Adams s y n d r o m e mid post-extracorpc~real p c r f u s i o n Datient~. especially those patients (~porated f~r t e t r a l o g y of Fallot or intervm~tricnlar septa| deh,ets, w h o r e surgical m a n i p u l a t i o n s have c a u s e d a com~I~,t~, a~rioventricu|ar dissociation. T}wre is e v e r y indication that a l i t t l e r a n d m o r e v a n e d ~ r o u p of ~alients will |)e c a n d i d a t e s for e x t r a e a r d i a e s t i m u l a t i o n in tim f~ture arid t h e r e f o r e er~deavors in this fi~,lrl will prr~hal~|), hav~, a veider area r~f a oplica tirm. This discussion will deal with dir~,et electrical stim~dation of the }tem't b y the variety r)f m e a n s now a v a i l a b l e clinically, and experimenta|tv.~ T h e a'~lv a n t a g e s and s h o r t c o m i n g s of each p a r t i e t d a r t y p e eft s t i m u l a t i o n will })e disr'~ssed ,ruder the respective headings. Frfm~ the S. I|udotph Idght l..aboratt~r!t Jor F,ur~ic~d ltv~.arch. D,'~mrtment o/ Nur~er!t.
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As I ) r e v i o u s l y inenti~Iried, t h e mairl disadvarit3ige of e x t e r n a l electrod,: xtim, d a t i 0 n is t h e h i g l m r ~olt,tg(..s a n d ¢:urre,tt ru:eessary to p r o d a c e ".:v'rm-icldar s y s t o l e tliroug}'J t h e j l i t a c l c h e s t w l d l arm 1.~qricarditm:~. 11 is i,~tpossil.~h: t,,.~h,c;,l.iZ(e
{(1 [h{e "v'~f21|lrictll~tr lll}'t,J(~atl-(lii, lllt+ (2citlslff|tlt,ttll.v o ;.t~ v o l l a ~ e s rrmv n e e d to ]~c st:~:pl->ed Np tO r l m i n t a i n a~ adc~ tmtc c a r d i a c ~mt|~lit t h e a m o i m t o f ct,~llcnl . . . . . . . .,,~'~-(Io::
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m a y i n t e r f e r e w i t h r e s p i r a t o r y f u n c t i o n b y t r i g g e r i n g tim d i a p h r a g m a n d hilly a c t u a l l y rectch t h e stal:c, whicl~ t h e p a t i e n t m a y b e u n d e r g o i n g a t.etanic seiz~lrc w i t h e a c h v e n t r i c u l a r c o n t r a c t i o n . T h i s res,dts in r a t h e r r a p i d cxhau...,ticm of t h e p a t i c n L T}mse d i s a d v a n t a g e s a r e not p r e s e n t , h o w e v e r , in all t h e a p p l i c a tions b u t b e c o m e m o r e p r o n o u n c e d as t h e l e n g t l t of s t i m u l a t i o n or n u m b e r of episodes of s:timulation increase. There appears both experimentally and clinically decreasing responsivenes~ of t h e m y o e a r d i , l m to s t i m u l a t i o n w i t h e i t h e r d i r e c t or i n d i r e c t c¢;rltrol. "l'ltis necc.ss ty to i n c r e a s e .stimtilatir,~-,,.._. v ~ l i a g e s t h e n is a p r o h l e m of ~,xtracardiac p a c e m a k i n g regardlc'ss {~f t h e m e t I m d e m p l o y e d . T h e a d v ; u l l a g ~ of d i r e c t ~dccti-ical s t i m u l a t i o n is thai< t i m e l e c t r i c a l f o r c e Caiil 1)O
o.:
I. "['IiANNf;IUT:%.Nt-;()t~S I)IIII~(:T .~-~'I'I).IULATIC)="; T h e e a r l y w o r k o f i r r i p l a n t i r i g w i r e e h : c l r o d e a a n d i i t i l i z i i i g an ~,xtei'nat ] ) a c e I i l ; l k / ' r ~.vils pif)noer,.'{l l~V \ V e h ' i c t l ~ "tvflrkill~ w i t h f A l l e l l e i ' s igro,tp al t]u- ( ' t l i . v('rsitv, ill" ~.[inrl(,Sf)lii+ P r e l i i l / i r l ; i r v rosll]ts o|" this illl)~ro;ictl were: t'lros~,~l,'d at if t llo (;'lilii{~lil (,l)ll~riiNN f:lf tilt' A l l l l ' r i ( ' i i i l (.,olh'gl" ,if ~ttr~l:#tlts irt .I ,{I57. "l'tiis w o r k w a s ~ r i g i n i t l l v tllid<-l-titk(,ll li) lrf2~ll l ) O S l s l i r ~ i c a l lit,art l t t o c k f,.tlb>wing ,ll)t'li ('ili'(titilL{llliV. "I=he rl;.~iills tl'lJl't" illllStaiTl(liilg w i t h llu" s a h ' i l g e (~f a lar~,;" ~ I t i i l | i '>{ i m t h , , l i s xvlio ,:¢cri' s l i l n u h i t c i l frolrl p e r i o d s of ii f e w |loi,r~ i,i ~ ) l l i ' tri~,ltllt T h i s lilt;lilt>el i)f COl:ill'O] , , t i l i z e d t i m ilrtpla~ilali<~lt t)ir ii si,i~],' illSllJlill-~| ttir~' ~,h'~.tr~l~h" ili ltit, vi,iilric-til~ir l~lvocar{lilliifl ailtll ilia: ~lll;i(-}illil,lil ~lt ~l Lrr~t~iil~t ~.lt,cll'o(h~" to lhl'. Cilia'st w a l l . A {~:oirimerciltllv a v a i l a b h : |);,i(:f}ll~i;lkl'r i;'a tilt'it ~tll;lc, h o d IO these: l n l v i n ~ eleetr<~des a n d v f ~ l t t r i c l l | a r r a t e set b y t}i¢~ p l i ) ' s i c i a l / . T l i i s ili)i)r(iglch rl'SliilS iltl il w e l l ll>cali~.od i m p u t s c {,if r+,ialivl-ly I~,w l l l ; i ~ l l i l l i f i t : (,I-:2'I v~tll~) ;111¢1 it is ]t!lssibh" ] i v iltl:rlqisillt~ till" v~>lla~e b y .~lila!l i i l t ' r t ' l l l l ' I t l ~, l l i l i i a i l i l i l i l l " s | i l l i l l t l i l i t l l t }iv tliis rllal'llit'r ill) l~l trOllr %vf,l'k~ ; l l l l i l)t,~sibh" ~t l i l l l , ' l(m~er. t
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T h i s b a s i c w o r k ~ i~tchlded cx) e1r i m e n t a t . evahiatio~'t of t h e l I m l h o d olJ a'~lireals. P e r i p h e r a l l>ressure a n d c a r d i a c outl?tit xver¢~ cte.ternfincd a n d il w a s d e m o n s t r a t e d t h a t a ~ ) - 5 o p e r cent r e d i l c t i o n irJ c . u t h , m {mtpl~t o c c t i r r e d w i t h surgicvll d i v i s i o n of the m a i n e o n e h m t i o n p a t h w a y s . T h e c a r d i a c outp~lt couh:! q u i c k l y b e r e v e r t e d to 95 p e r cent to 167 per cent of n o r m a l b y d i r e c t stilnillation in t h e r a n g e of 90 s t i m l i l i a r e | m i t e ilt spih~ of the: fact t'hat t h e a n i m a l s " p r e b l o c k p u l s e rate h a d b e e n c o n s i d e r a b l y h i g h e r , l,lt, an a ! t e r i a l p r e s s l i r e w a s also fom~d t . . t ~ p r 0 a e l J n o r m a l w i t h s t i m u l a t i o n t h r o u g h t h e s e i m p l a n t e d w i r e electrodes. If o n e c o n s i d e r s t h e u h h n a t e il, d e s i g n of a c h r o n i c e x t e r n a l s t h m i h i t o r t h e s h o r t c o m i n g s of this m e t h o d a r e r e a d i l y a p p a r e n t . ( 1 ) A n i n l y i n g e l e c t r o d e t x a v e r s i n g t h e skin b a r ~ e r . ( 2 ) T h e p o s s i b i l i t y of b r e a k in c o n t a c t B e t w e e n e l e c t r o d e a n d p a c e m a k e r from p a t i e n t m o v e m e n t . ( 3 ) P o w e r failure. ( 4 ) I n a b i l i t y to a e c o r n o d a t e o u t p u t
t't Ill. l'~ iilt~,l"
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rt)lindpd b y a c o l l e c t i o n of c r e a m y m u t e r i a l wlfich w a s fc.it~tt to b~- sterile (m ~-~dturc'. "llte stimlll~tting v()ltages art: ot low rlt;,~idt~(h: ar,d ar~, al>plie(l (tirv(.t-. ly It* t h e }le;trt, "I'ltt: i i ] c r e a s i n g r~esislarlc~, o| Ill,- ~lix'o(:ar(litiirl | o stimtllatiol~ ti)r()~,~ti t | l e irtll)lar, t(:t[ w i t , . i.'~ pre.~,.i~l wilt* |hi.', r r w t l , ~ d i~'; w i t l l ~ltllers. }itixv0 vLq-. C e r l a i n m o ( i i f i c a t i ( m in e l e c t r o d e e~n,s/ril(:tir>li iri ;,ss()¢:ialit)t, w i t l l t h i s ~l~it ar~" ~ifiv.; } ] e i t i ~ e v l i h i a l e l ] })v Nlliiti'o. "|'lit'S(' ~il't' ~l('siKl.'(, Iil)erat(~'d at lli(~' l . i ( . c l n i ( h . . l i r c o c a r ( l i ; l l iilii(-li(>ii. " l i i i ~ "l~h,.ckink~" (.h..ctrt~dv w o r k s well ill $]tort f('rlll l.-.|)(,riill~.lil~ i>,ii ;t~ vt-t l . i s li<,i b(.~.lt f , , l l v l.-¢;ihililp(l fJrl ~t i o l t < ~ t('l+lll illisif;, l:: IV.
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l"h~, o t / - . r a p p r . . c h 1o l h e p r . l ~ l e m ~Jt" c~mtl:,let~" tsearl l ) h . : k has l.,('n lh~~llili~..;tlicm o f l|i(" ; ~ l r i c ~ d a r p -.v~lve to l r i ~ g ( ' r a n d l i m e an p-.ien~.~| ~ l i m i d a h ~ r . T h i s m e i l . M w a s firsl r e p o r t e d b v l ' ~ d k m a . ;,lid ~.V;ttkflls ~ :rod ;~ c:,ri;~,~l ~ t tllis b y l l - " , , l h o r ' s g r , u p ~:~ ( f i g . I "~. t r e a h n e t t | ~if l|i¢" i d i o v ~ . . i d r i c l i | i i r r l w l | m t ~tf ] w a r l i ) | , c k . . ~ merry |~l~}~i~d~ic;~l ( < t t l l r ~ l (~i tll~- ~.;trdilw r i d e . . v , l i l d b~. l~referabI~ ". "I'l~i~ w~.~l~t p~.rniit ;t v;~ri:~bl, c a r d i a c o l l l l ~ i i l ilt n ' l a l i o i l to I ~ h v s i ~ l ~ k i d . t~if~ell~.mic:ll ;~ll(I l~h>~i~--I ~1~'~..~-~ ~ f pt~.~/of->eraliv~, r e e ~ w e r v ~md n o r t n a I (.:;ercise~ coml>li~:;fled a n d r e q l d r t : s t h e ; l ( l d i i i n n ~)f ~m ; m r i c l d ; t r r h . c i r o d e . T h e i m l m l s e f r o n i tli~: a i i r i c | e in f e d i n t o a m u s c l e p o l e n t i a l a m p l i f i e r w h i c h hz, s p r e v i o l l s l y b e t : n dr..scribed ~-~7 a n d , , s e d t o t r i g g e r ~ ¢orwe.rititm;,l s l i m u l a t t . . Experimtmh,] e v . h . l l i o n h~s bet,li r e p o r t e d b y lin :~ nlltl h:ts l . ' . ' , t(.~.+l f,, qitleklv r e s t o r e t.:mttdy~i.~mfie t.quilibrium (fig. 2), At tltv |)re~;,,ltt fillip ;I lr~lmiishlriz~'t| !rail is | ) t ' i l i l ~ ;~,.! d ~ t , . h t
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sdv~* ~hc pr(~blen~ (~f ~he i~I~it being p~-'t~t}~h' ~mtl :,~na]l et~(~l~gl~ l~ fit hi the path,m'~ shh't |mcl,:et T h e llse of the al~ric'ldar h~I>l|lsc tn irim~t.r ar~ external .qim~dahn" tins t~.t~) lIm~k~Jlt b y s~mle (o lx" imlmlelical d ~ e to t|lc ~lnricutm" ladrvca,di;m thai acc o m p a n i e s an idiovei~tric-uhlr r h y t h m . \ V e have f o u n d tllrc)ugl~ experimt, l~lal applicati(m thal the a u r i c u l a r rale r a p i d l y lt,v(~rls [o n o r m a l with adeq~mie ventric~llar slimulalitm. ()rio possible c()n~l)licati()l~ ()I" this m c t l l o d ()f stim~llaIion .eolthl be the dev<.lopmer~t of am'ic~llar fibrill;il:ioli w i t h rcsultm~t faiai m ' r l } v t h m i a . For this rcas(m a blocking circlli( is ~" n c•l ~ ( 1.t.~ l in the ,,nit to t m ' ve~lt s t i l m d a t i . n from (~ccurring m o r e r a p i d I y than l.i0 p e r m i n u t e . A m a s t e r r~scilhtm" is ;~lsr) i n c l m h ' d in case ¢~f t'lti]llr(, o[ th(' allriclllar pick-.l~, Tills unil as previoiisly descrilxxl in tile lilcratm'e lind the s a m e d i s a t l v a n t a g c as (~[her metht~ds 1)ut at the present time is apl'died v.itliollI th¢' direct s~blr(" (~f ('hcliod(.' • " .s tf:~ lho mvocardium.. By passing<, a do~bl¢: e l e c t r o d e c a t l . , l e r llmjug)~ a peripht, ral vein i/lit) the ri,Rl-lt a i r i m n with tlw tip e x t e n d i n g thrt)ugi~ the trie~ispid valve into tile right ventric~llar c.ix"":t'~ '~, p i c k - u p :rod sliinlilalion caii t . , ac(..(mlI~lisl-led. This rneth()d ¢If ( . h ' d r ( . l e phlc(~menI uIilizcs Ihe norl~ial rh.ctrical c ( m d u c l i v i t y of Ihe blo{~d a n d in lhe eXlX~rin~elltal a n i m a l s }l~s noI giv(,~l rise I~ e n d o e a r d i a l tl|)rosis, tliromb(~sis . r l i e . ~ o l y s i s . T h e ~ls(' o f ;t similar single ¢~theh.r has l)ren n T m r t e d b y lh~rm;m a n d S e h w e d e l . t''
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D ~sct~ss i o~ F r o m tim p r e c e d i n g d c s c r i p t i o r i s of t h e p r e s e n t a p p r o , c h c - s to dirct:t card iltc' stimutalio~) o n e is i m p r e s s e d b y t h e il)got~Jotls d e v i c e s tidal can l)~. dex.'clCq)ed to so|w: a pg, r t i m d a r problerr} t h a t c o n f r o n t s ~ts as p h y s i c i a n s . . M o s t ()f timse : t p p r o a c l m s h a v e t)een ~nadc possit)h: only lhr(,tgf] tim c-()Ol}crative eliortx ~I the pltysiologist, m e d i c a l e l e c t r o n i c s e n g i n e e r ;in(1 the pt~ysician. .iettrtt~cr i n s t r t t m e n t a t i o n in this fiehl is rapidly" b e i n g devclopc¢l tllrottgl~ tlmsc tcarl~... of r e s e a r c h invest:igators. At t h e t i m e of w r i t i n g of this s t u n m a r y the o n l y u n i v e r s a l l y a v a i l a b l e t y p e of s t i m u l a t i o n is t h e e x t e r n a l u n i t w h i c h can b e c o n n e c t e d to the m v o c a r d i u m b y o n e of t h e v a r i o u s t y p e s of e l e c t r o d e s . T h o ~ g h t h e o t h e r units have. all b e e n a p p l i e d clinically most are still ~ n d e r g o i n g f u r t h e r e x p e r i m e n t a l evn]lmtion. T h e a v a i l a b l e c o m m e r c i a l units can b e a p p l i e d t h r o u g h t h r e e m e t h o d s r.~f e l e c t r o d e p l a c e m e n t . If t h e c h e s t is o p e n an e l e c t r o d e c a n b e s u t ~ r c d d i r e c t l y to t h e m y o e a r d i u m . T h e t y p e o f e l e c t r o d e c a n b e citl~cr at co~n~wricatllv availa b l e (mc w i t h a s w e d g e d - o n needh.." a n d a l r e a d y ins~date(l; ~,r ~)~(. ,.:an I,~~ shrtp l y c c m s l r u c t e d f r o m s t a i n l e s s steel (:al~h.."w i r e m~tur¢' i~sil~g fine l)(dyethvle~(" ot teflon t u b i n g for i n s u l a t i o n . In t h e s('a'ir~l]slv ill p a t i e ~ t ..vlwr¢. tl~,r:~cot(,r~v w~n~ld l~e p o o r l y t o l e r a t e d a 16 Io 18 ~;tR,r r,~.~.
TI~' f o l l o w i n g tn~tline m a y lm h e l p f u l I(~ t l m s e lu,(l~,rlaki,~t{ ¢tir(,ct citr~tia(. ~timtdati~m. It is w i s e for caol~ .~rocq~ t¢~ ,.loci tl,,. t>'p~" of ¢,l~,ctro, h- ~)]=,(-,.m,'nl Io t~e ~,lilizod w | m n tll(: n e e d ~)f pacelt~akirJ~ |wcorno~ al)l)~lr¢'~t. "Fl..s~' el¢'cIr(~d('~;
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ft. Place the ground electrode t o the patient, preferably by . utm(,, and connect this to the pac-enaaker. 3. Attach active electrode to pacemaker which has b e e n warme(l up (stand: by position ). 4. Adjust voltage so that minimal voltage will cause ade(:luate• vel)tricular c o n t r a c t m , , . This can be determined b y the retma~ of adequate peripl~eral pressure. 5. Rate slmuld be set at 8 ~ 1 2 0 stim,0i per minute to maintaiI, -'--!equate pressure. 6. Attempts to wean the heart from the stimulator should be made frequently to determine whether the normal mechanism of rate has returned. O n e m u s t be conscious of the fact that after stimulation a c o m p e n s a t o r y asystole lasting from 2--5 s e c o n d s usuMIy occurs prior to the first v e n ~ i c u l a r complex. St.rM~tarty I. Direct cardiac p a c e m a k 6 n g can be a c c o m p l i s h e d b y a variety of m e a n s at the present Nine and can be lifesaving to a large group of patients. 2. ~ e available clinical and experimental a p p r o a ~ e s to direct stimulation have been described. 3. The ul~mate in pacemakers is not vet available but experimental work is underway to produce a more physiological transistorized m~til capable of reproducing all aspects of the ,mrmal electrocardiogram.
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BEFERENCES \Valshe, XV. It.: A practicM treatise on disease |~e external eleclric stimu|adise:ases of tile, great vessels. Phila{iOn. J.A.~\I.A. 359:10!5, 1955. d d p h i a . B ! a n c h a r d a n d Lea, 1862. 7. Zol]. IL M.. Panl, Xl. H., Linenthal, A. Zotl. P_ M.: Resuscitation of d u heart J., N o r m a n , L. R-. a n d Gibson. "~V.: in ventriculur standstill b y t x t e r n a l T h e effects eft external ~ e c t r i c curelectric stinmlatkm. N { w gr, gland J. rents on t h e heart. CireJ.datkm 14: },led. 247:768. 1952. 745, 1956. ~ , Linenthal, A. J., (libson, \V.. Paul. 8. \Veirich. X\'. L.. Gott, V, L., and LiIle,M, H. a n d N o r m a n , L. It.: T e r m i n a hei, C. \V.: T r e a t m e n t of c o m p l e t e -tion eft ventricular fibr~lation in m a n heart block |~y c o m b i n e d usv of myob y exttwnally applied e | e e t r i c c~nmtcardial d e c t r o d c a n d artificial pac,,erslmek. 4New E n g l a n d .l.Med. 25-& maker. ,q.Kor~m~ 8:360, 1957. 727. 1956. ~k S e n n i n g , A.: Discussion of p a p e r by . a n d N o r m a n . L. R.: Treatme~lt SleDhenson e t a ! . J.Thorack~5¢ Cardioo o{ Stokes-Adams disease b y external vasmdarSurg. 38:638, 1959. electric stimulatim, of heart. Cirellla10 Glenn, "~V. L., ?}lauro, A., L o n g o . g.. lion 9:482, I954. Lavietes, P. H., and M a c k a y , F. J.: Reiff. T. R.. Oi~penheimer. J., and R m n o t e stimulation of the h e a r t by Ferguson, C.: Cardi:m injury preradio/requeney tra r~smission. New stmmbly d u e to ,,se of tile external g n N a n d J.Med. 261:948, 1959. electric cardiac p a c e m a k e r in Stoke.~11. M a u r o , A.: T e c k n i q n e for in situ stimAdant~ disease. Am.HenrtJ. 54:437, ulation. Yale Biophys.Bull. 1:2, 1948. 1957. 1:2. ~ , Wall, P. D., D a v e y , L. M., and Rose.. l.. 13. and ",Vartoniek, %V.: T r ~ t Salter, A. M,: C e n t r a l n e r v o u s ~timu. meat ~ff a ca~,, ~ff Stokes-Adam~ lalion hy i m p l a n t e d h i g h freqlleney
IH1H~CT ELECTI{I(~AL (;A!{DtAI~ STI.~,IUI.,A'I'OI~S
,edivcn. Fed.Prec. ,9:86, 1950. Persotaa| eommm~icatiou. N o v e m ber. 1959, l-l. FolkmmL M. J., and \Vatkin,~, E.: An artificial condtmtlm~ system for lilt: Inatl;lgemt;tlt Of coreD|ere heart h|ock. &Forum 8:331, J958. 15. Stephenson. S. E,, Jr,, Edwar(ls, \V. I'L, Jolly. P. C., and Scott, H. W., Jr.: Physiologic p-wave cardiac stimutat~ar. J.Tlmr. CardiovaseularSurg. 38: (~M, 1959. 16. ~ , Bats(m, R,, Nh)ntg~m~cry,. I.,. H., Ymmg, W,, Clark, S, L., and t)aniel, R. A., Jr.: PiLvsiMogical control of rfrspiration during experimental thor13, ~ :
~cotomv. BulLSoc.Interuat.Chir, I7: 32O, 1958. 17. Bats~m, R, Morag, mi~ry, L H., Beisd. L If.; McCrosky, 1)., and Clark, ,*g~ L.; Electronically vomrolled r~4pir.a* tor, Science t2{):815}, 1956. 18. Stephenson, S. E.. Jr., J,dly, P. C., Bailey, tl. \V, Edward~, \V. |t., a,~d Montgomery. L. [1.: Eva|~alkm at tht- p~wave exlernaI cardiac ~timulatot. S.l-'orun'~ IO:(~IE, It)60. l.q. Furman, S. and Sch~ede|. J. B.: A:~ infracardiac pacemaker f~r Stokt>. Adams seizures. New England J, Med,, 26I:9.13, 195.~J.