|Publication number||CA2107147 C|
|Application number||CA 2107147|
|Publication date||27 Jan 1998|
|Filing date||28 Sep 1993|
|Priority date||23 Oct 1992|
|Also published as||CA2107147A1, DE69322592D1, DE69322592T2, EP0594271A2, EP0594271A3, EP0594271B1, US5269298|
|Publication number||CA 2107147, CA 2107147 C, CA 2107147C, CA-C-2107147, CA2107147 C, CA2107147C|
|Inventors||John M. Adams, Clifton A. Alferness, Kenneth Ross Infinger, Yixuan Jin|
|Applicant||John M. Adams, Clifton A. Alferness, Kenneth Ross Infinger, Yixuan Jin, Incontrol, Inc., Cardiac Pacemakers, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Classifications (5), Legal Events (2)|
|External Links: CIPO, Espacenet|
2~71 ~7 PATENT
~4407-120 ~p~AT-9~0~ L~ FOR P~uv 8r~Rn D~T-~YRn CA~DIO~8ION
8~ ~v O~ ~8 ~ ON
The present invention generally relates to an atrial defibrillator and method for applying cardioverting electrical energy to the atria of a human heart in need of cardioversion. The present invention is more particularly directed to a fully automatic implantable atrial defibrillator which exhibits i~vv~d safety by reducing the potential risk of in~ e~
ventricular fibrillation which may result fro~ the mistimed deli~ery of cardioverting electrical energy to the atria. More spPcifically, the atrial defibrillator and method of th~ prQsent invention guards ~ga ~ ~ct applying cardioverting electrical energy to the atria under conditions believed to contribute to. 1~ ,o~
Atrial fibrillation is~probably the mo~t co~on cardiac arrhythmia. Although it is ~ot usually a li~8 threatening arrhythmia, it i~ a~sociated with ~trokes thought to be caused by blood clots forming in ar~a~ o~ :
stagnant bloo~ flow a3 a result of prolonged atrial fibrillation. In add~tion, pati~nts a~flictQd with atrial fibrillation gonerally exp~rience palpitation~ of ., .
7 1 ~ 7 the heart and may even experience dizzines~ or even 1088 of consciousnes~.
Atrial fibrillation occurs su~enly and ~an~ -times can only b~ corrected by a discharge of electricial energy to the heart through the skin of the patiQnt by way of an external defibrillator o~ the type ~ell known in the art. This treatmsnt i~ c~ ~nly referred to a~
synchronized cardiovQrsion and, as its na~a impli~s~
involves applying electrical defibrillating ener~y to tha heart in syn~hronism with a d~tected ventricular electrical activia~ion (R wave) of the heart. The tr~atment is very painful and, unfortunately, most o~ten only results i~ temporary relie~ ~or patients, lastlng but a f ew weeks.
Drugs are available for reducing the ~na~
of atrial fibrillation. ~ v~r, these drugs hav~ ~any side effect~ and many patient~ are re~i~te~t to th2m which greatly re~u~s their therapeutic e~fect.
Implantable atrial defibrillators hav~ b~n proposed to provide patientC suffering from o~ l.c~
o~ atrial fibrillation with relief. Unfortunately, to the detriment of such patients, none of thes atrial de~ibrillators hav~ becom~ a co~erclal reality.~ .
Implantabl~ atrial defibrillator~ o~ in the past:have exhibited a number of disadvantiage3 which ~.
: probably has precluded these defibrillators from beco~ing ':
~ 071 ~7 a com~ercial reality~ Two such proposed defibrillators, although represented as being implantable, were not *ully automatic, requiring human in~eraction ~or cardioverting or de~ibrillatinq the heart. Both of these proposed de~ibrillators re~uire the patient to recognize the ~ympto~s of atrial ~ibrillation with one defibrillator requiring a visit to a physician to activate the defibrillator and the other defibrillator re~uiring the patient to activate ths defibrillator from external to the patient's skin with a magnet.
Improved atrial de~ibrillators and lead sys~ems which ~h;~it ~oth automatic operation and ~ , o~ed ~a~e~y are fully described in cop~n~ing U.S. Applications, Serial h~ . 07/685,130, ~iled April 12, 1~1, in ~h~ name~ o$ ~ohn M. Adams and Cli~ton A. ~lfernes8 for IMPROVED ATRIAL DEFT~TT-T~ToR AND ..~n~ and Serial Numb2r 07f856,514 ~iled March 24, l~g2, in ~he nam~ o~ John M~ Adams, Cli~ton A. Alferness, and Paul E. Krey~n~g~n for ~ kv~u ~TRTAT
DEFT~RTT~T~OR, LEAD ~Y~ , A~D HET~OD wh~ch applications are assigned to the assigne~ o~ the pre~ent inven~ion. A~ di~closed in tne aforementioned re~erenced appllcations, ~ynchronizing t~e delivery of the de~ibrlllating or cardioverting electrical energy to the atria with a ventri~ular electrical ~Ętivation ~ wav~) of the heart ~as been con~id~red important to avoi~
:,, . , ,, ,, , ,,, . " , . . . . ~ . .. ... . . . .. . .
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' ' ' ' '' , ' ' . ' ":', ' ' '' . ' . ' ', ' ' ' ': " ' ' ' : , l ' :
cardioverting the heart during the heart's vulnerabl~
period or T wave to thus prevent induced ventricular fibrillation. Ventricular fibrillation i~ a ~atal arrhythmia which can be cau~ed by electrical energy beln~-deli~ered to the heart at the wrong ti~e in the cardiaccycle, such as during the T wav~ of the cycl~. Th~
atrial defibrillators of the aforementionQd re~5~n~Q~
applications exhibit improved safety from tn~tt~in~
ventricular fibrillation by sansing ventricular lQ activation~ of the heart in a manner which avoids detecting noise as ventricular elactrical activations for generating reliable ~yll~hLo~ization signals. HenGQ~
these implantable atrial defibrillator~, by pro~ldi~g~ -such noise i ~ty in R wavQ detection assur~ r~l~Ahl~
Another mea ure for reducing the ri~k of inducing ventricular fibrillation during the deli~xy of cardioverting electric~1 en~rgy to the atria of the haart employed by the deflbrillator~ of the af~- ~ Lt~d referenced applications i5 the reduc~ion of th~ amount o~
the electrical energy which i~ pa~s~ through thQ
ventricles during cardioversion of the atria. Thi~
achieved by locating the cardioverting electrode~ in or near the heart to provide a cardio~erting energy path :25 which con~in~s substantially all of the cardiov~rting electrical energy to the atria of ths heart.
~ ~7~ f~7 It has also been obser~ed that during epi~e~
of atrial fibrillation, the cardiac rate increases to a high rate and/or becomes extremely variable. At high cardiac rates, the R wave of each cardlac cycl~ b~co~s~
closely spaced from the T wav~ o~ the imm~diat~ly preced1n~ cardiac cycle. This create3 a condition known in the art as an "R on T" con~ition which is beli~v~d to contribute to induced ventricular fibrillation i~ th~
atria are cardioverted in synchronism with thQ R wav~
close to the prece~i n~ T wave. For highly variabl~
cardiac rates, a long cardiac cy~le can be followed by a relatively short cardiac cycle. Thi~ condition i~
believed to cause disper~ion o~ r~ractoriness and al~o can result in a vulnerable R on T condition~ For a more complete understanding of the aforementioned highly variable cardiac rate and the conseql~e~c~R ther20f, rPference may be had to an article entitled El-Sheri~ ~t al., Reentrant Vsntricu1~r Arrhyth~ias in the ~ts Myocardia1 Infarction Period: N~chanism by ~h~ah a Short-Long-Short Cardlac Sequence F~cilitat~s th~
Inductlon o~ Reentry, Circulation, g3(1):26~ 8 (1991).
It ha3 been further ob~er~ed t~at a~
ventricular activation~ propagate through th~ heart~ th~
riqht ventricle apex activates slightly prior to the superior left ventricle. Hence, if the atria ar~
cardioverted in synchronis~ with an activation of th~
; 5 .
?:~ ~71 /~
right ventricular apex, the activation of th~ ~uperior left ventricle may not be completed. Recent studie3 have shown that cardioverting the atria when the ventricular activation is not fully completed may contr~buts t~
induced ventricular fibrillation.
The atrial defibrillator and method Or th~
present invention greatly re~ he ri~k o~ ~ n~ n~
ventricular fibrillation during atrial cardiov~r3ion or defibrillation by assuring that the card~overting electrical ener~y is not applied to the atria during both an R on T condition and a not yet completed ventri~ular activation. As will be seen hereinafter, this is acc~mplished by d~laying the application o~ ~h~ : .
cardioverting or defibrillating Ql~ckrical en~r~y ~ntil a predeter~ined delay time has elapsed after detecting a ventricular aativation. The delay timĘ is chosen to b~
o~ suf f icient duration to a~sure thzt the ventricul~r activation has fully complet~d and of insu~icient duration to avoid applying the cardioverting el~ctrlc~l energy to the atria during the T wave i~med~ately following the detected ven~ricular activation. A~ a result, a reduced risk of i.n~ e~ ventricu~ar ~ibrillation is assured be~aus~ the cardiovor~ing electrical energy will not be applied to fhe atria during an R on T condition, during an llnr , leted ve~ $cl~
activa~ion, or during a vulnerabla period of the he~r~.
~ ~ ~ i7 ~ ~ 7 S~A~ OF ~ NV~ ON
The pr~sent invention therefore provide~ atrial defibrillator for providing cardioverting elsctrical energy to the atria of a human heart. The atrial defibrillator includes detecting means for dQtecting ventricular activations of the heart, cardioverting m~n3 for applying the cardioverting electrical en~rgy to the atria of the heart, and d~lay m~an~ L~o~,~iva to th~
detecting means ~or causing the cardioverting ~e~n~ to apply the cardioverting electrical energy to the atria o~
the h2art a predetermined delay time a~ter the ~irst detecting mean~ detects one ~f the ventricular activations and before khe T wave of thQ heart ; le~iately followlng one of the ventricular act~vation~.
The present invention also provides an implantable atrial defibrillator for providing cardioverting electrical energy to the atria of a hu~a~
heart in need o~ cardiover~ion. The atrial defibrillator include~ first detecting ~ean~ ~or dQtecting ventricular ZO activations of the heart and second detecting mean~ ~or d~ecting atrial activity of the heart. ~he ~tri l de~ibrillator further includes atrial defibrillation detecting mean~ respons ve to the second detecting mean~
~or deteL i~i~g when the atria of the heart are in nee~
of cardioversion and cardiovert1ng mean~ for applying the cardioverting ~lectrical en~xgy to the atria o~ the heart .
.. , . . ~ , ., ~ . . ~ . . . . . .. .
~ ~7~ ~7 when the atria of the heart are in need of cardioversion.
The atrial defibrillator further includes delay me2ns responsive to the fir~t det~cting means for causiD~ th~
cardioverting means to apply the cardioverting electric~L
energy to the atria of the heart a predetermined d~lay tim~ after the first detecting mean~ detects one of th~, ventricular activations and before ths T wava o~ th~
heart ~ tely following the one o~ the ventri~ula~:
The present invPntion further provide~ a m~thod of applying cardioverting electrical energy to th~ atria of a human heart in need of cardiover~ion. Ths ~thod include~ the steps o~ detectin~ ventricular activ~t~Q~
o~ the heart, detecting atrial activity of the heart, and determining, responsive to the detected atrial acti~ity of the heart, when ths atria of the heart are in ne~d 9 cardioversion. The method further include~ the st~p o~
applying the cardioverting electrical energy to thQ atria of the heart when the atria of the heart are in nQ~d 0~
cardioversion and a predQtermined delay tim~ a~t~r detecting one of the ventricular activation~ and b~or~-~
the T wav~ of the heart i ~di~ely following the ona og :~
th~ ventricular activations.
' -..,' :
9~E~ DE~Ca~PT~ON OF ~H~ D~INa8 The features of the present invention which ara believed to be novel are set forth with particularity in the appended claims. The invention, togethQr ~ith further objects and advantages thereof, may b~st b~
understood by maklng reference to the following-description tak~n in con-Junction witb the accompanying~
drawing, in the sole fiqure of which like r~f~a~c~
numerals identify identlcal elements, and wherein the sole Figure is a schematic block diagram of a ~ully implantable atrial dePibrillator e~bodying ths ~
invention for applying defibrillating electrical ~n~ ~y to the atria of a human heart and which i3 shown in association with a human heark in need oP atrial fibrillation monitoring and potential cardiovers~on of the atria.
DETAI~D DB8CRIP~ION O~ ~B PR~E~R~D ~M~ODI~E~.
Prior to re~erring to the sole Figur~, a ~eneral description of a typical or normal cardiac cycla m~y be helpful in underst~n~ing th~ operation and varlou~
aspQcts of the present invention. The beginni n~ 0~ a Gardiac cycle is ini~iated by a P wave which is nor~ally a snall positive wave. The P wave in~ucps depolarization of the a~ria of the heart. Following the P wav~ th-r~ i~
a cardiac cycle portio~ which is substantially con~tant : ~ g ~ n7~ 7 have a time duration on the order of, for exampl~, 120 milliseconds.
The QRS complex of the cardiac cycla then normally occurs after the substantially c~nstant portion.
The ~ ting feature of th~ QRS complex i~ tha R wav~
which is a rapid positive or negative de~lection. Thc R wave ge~erally ha~ an amplitude gr~ater than any other wave of the cardiac cycle and will have a spik~d qh~pe o~
relatively short duration with a ~harp rise, a peak amplitude, and a sharp decline. The R wave i3 the : :
depolarization o~ the ventricle~ and hence, as us~d herein, the term "ventricl~ activation~l' denote~ R Wa~B
o~ the heart cardiac cycle. As previously m~ntion~d, a~
ventricular activations propagate through the he~rt, th~
right ventricle ap~x is generally depolartzed 81ig~1y prior to the depolarization of the supsrior le~t ve~tricle. :
Following the QRS complex, the cardiac cyaln i~
completed with the T wave whic~ eparated from th~ QR~
complex by about 250 milli~econ~. The T ~av~ is relatively long in duration o~, for example, on the order oP 150 ~ conA~0 It i~ during thQ T wav~ that the heart i5 most vulnerable to in~c~ ventricular fibrillation should the heart be cardiovert~d during th~s ~eriod. The next ~ardiac cycle begins with th~ n~xt ' "- 2.~ 7 P wave. The duration of a cardiac cycle may be on thei order of 800 milliseconds.
As will be appreciated hy those skilled in the art, thei characteristics of a cardiac cyclG of a h~a~t experiencing atrial fibrillation will be di~tinctly differ~nt than described above for a normal cardiac cycle~ During atrial fibrillation, there gsnerally are no discernable P waves because the atria are in a~
unstable or fibrillating condition. Also, the cardiac rate may be extremely high and highly variable which result~ in the previously referred to R on T condition where the ventricular acti~ation (R wave) of one cardiac cycle i5 closiely adjacent in time to the T wave o~ th~
i -~iately preceding cardia~ cycle.
Referring now to the sole Figure, it illustrates a fully implantable atrial deflbrillator 30 embod~ing the present invention shown in association wit~
a schematically illustrated human heart 10 in neQd o~
atrial fibrillation monitoring and potential cardioversion of the atria. The portion~ of the heart 10 illustrated in Figure 1 are the right ventricle 12, the le~t ~entricle 14, the right atrium 16, the left atrium 18, the superior vena cava 20, the ccronary sinus ~h~n~l 21 which, as used herein, deno es the coronary sinu$ 22 and the great cardiac vein 23, th~ coronary sinus ost~um 11 - ' ~ .
. J1 7 or opening 24, the left ventricular free wall 26 and th~
inferior vena cava 27.
The atrial defibrillator 30 gensrally incl~des an enclosure 32 for hermetically sealing the inter~al circuit elaments of the atrial defibrillator to bo described her~inaft~r, an endocardial first lead 34, and an intravascular seco~ lead 36. The enclosur~ 32 and.
first and second leads 34 and 3C are arranged to be implanted beneath the skin of a pati~nt so as to L~n'~
the atrial defibrillator 30 fully i~plantable.
The en~oc~rdial first lead 34 pre~rably comprise~ a endocardial bi-polar lead having ele~trod~
38 and 40 arranged for establj~h~n~ electrical cont~t with the right ventricle 12 o~ th~ heart 10. Th~
electrodes 38 and 40 permit bi-polar sen~ing o~
ventricular activation in the right ventricl~. A~
illustrated, th~ lead 34 is fed ~hrough the ~uperior vQna cava 20, into the right atrium 16, and then in~o th~ : :
right ventricle 12.
The second lead 36 generally include~ a ~ir~t or tip electrode 44 and a second or proximal ele~ 0~2 46. As illustrated, the s~cond lead 36 is ~ ;hl~ and arranged to be passed down the superior vena ca~a 20, into the right atrium 15, into the coronary sinus ostium 24, and advanced into th~ coronary sinu~ ~h~nn~l 21 of the heart near the le~ side thereof ~o that the ~lr~t or .
tip electrode 44 i~ within the coronary sinus ch~el 21 either within the coronary sinus 22 adjacent the left ventricle 14 and beneath the l~t atrium 18 or mo~t preferably within the yreat cardiac vein 23 adjacent t~
left ~entricle 14 and beneath the left atrium 18. Th~
electrodes 44 and 46 are paced apart such that when thQ
first electrode 44 is positioned a~ described abovQ~ the second electrode 46 is in the right atriu~ 16. Tha fir~t electrode 44 together with the second electxod~ 4«
provide bi-polar sensing o~ heart activity in tha a~ria 16 and 18. The first electrode 44 and the RecQ~
electrode 46 further provide ~or khe deliv~y of defibrillating electrical energy to the atria. B~a~l~~~
the first el2ctrode 44 i~ locat~d beneath the l~t ~trium 18 near the left ventricle 14 and the ~econd ~le~L~o~e 46 is within the right atrium 16, the electrical ~ y applied between these electrodes will be substantially con~ined to the atr~a 16 and 18 o~ the heart 10. A~ a re~ult, the electrical energy applied to the rig~t ventricle 12 and left ventricle 14 when the atria are cardioverted or de~ibrillated will be minimized. This greatly re~uce~ the potential for ventricular fibrillation of the he~rt to be in~uce~ as a reeu~ o~ -the application o~ defibrillating ~lectrical en~r~y o~
the atria of the heart~
: ~ ~3 Within ~he enclosure 32, the atrial defibrillator 30 includes a first sense amplifier 50, an R wave detector 52, and a second ~ense amplifier 54~ The first sen~e amplifier 50 and the R wave de~ector 52 ~or~
a first detecting ~eans which toge her with ele~L~.7~F 38 and 40 of the ~irst lead 34 to which sense ampli~i~r 50-is coupled, sense~ ventricular activations o~ the right ventricle 12. The second sense ampliSier 5~ ~orms ~
~econd detecting means which, together with th~ ~irst electrode 44 and second electrode 46 of th~ secn~ lead ~ -36 to which it is coupled detects atrial activity o~ th~
The output of the ~irst sense amplifier 50 18 coupled to the R wave detector 52. ~he R wave dets~tor 52 is ~f the type well known in the art which provide3 an output pulse upon the oc~ ence of an R wav~ bQing sensed during a cardiac cycle of the heart. Th~ ~u~y~
of the second ~ense amplifier 54 i~ coupled to an ~log ~ -to digital convQrter 60 which converts the analog ~i~n~
representative of the atrial activi~y of th~ heart being detected to digita1 samples ~or ~urther proce~3ing in a manner to be dascribed hereinafter. .:.
ThQ enclosure 32 of the atrial de:fibrillator 39 further include~ ~ mioLe~oc2ssor 62. The mi~Lo~ o~e~o~
62 is preferably imple~ented in a manner a~ disclos~d ln : the aforementioned copending U.S~ Applications, S~Eial :.
~: , : ~ 14 Numbers 07/685,130 and U7/856,514 and ~urther a~
dascribed hereinafter. The implementation of th~
microprocessor 62 in accordance with this ~ ho~;r~t o~
the present invention results in a plurality o~
functional stages. The stage~ include a synchronization detector 64, a delay timer stage 66, a comparator ~tage 68, a time delay set stage 70, an atrial arrhythmia detector in the form of an atrial fibrillation dQtQctor 72, and a charge delivery and energy control stage 74.
The microproc~or 62 is arranged to operats in conjunction with a memory (not shown) which may bQ
coupled to the microprocessor 62 by a ml~ltiple-bit addres bu~ (not shown) and a bi-directional mult~p~e bit databus (not shown). This permits the mi~ opioces~r 62 to address desired memory locations within the me~ory ~or executing write or read operations. During a write operation, the mi~ o~,oce~or ~tores data, such a~ tim~
intervals or operating parameter~ in the memory at th~
addresse~ defined by multiple-bit addresse~ co.lYeye~ over the addres~ bu~ and co~eya the data to the - ~ 92 ov~r the multiple-bit data bus. During a read operation, the microprocessor 62 obtains data ~ro~ the memory a~ th~
storage locations identified by the multipl~-~it addresses provided over the addres~ bus and receive~ th~
~5 data from the ~ over the b~-directional data bu~.
~ ~97~ ~
For entering operating parameters into the miGroproCesSOr 62, as for example the time delay re~erred to hereinafter into time delay set stage 70, th~
microprocessor 62 receive~ programmable ~ ing parameters f rom an external controller 100 wh~ch ~
external to the skin of the patient. The ext~rnal cor.L,oller 100 i5 arranqed to communicat~ w1th a receiver/transmitter 102 within enclosura 32 which ~
coupled to the microproc~ssor 62 ov~r a bi-directional bus 104. The receiver/transmitter 102 may b~ o~ th~ typ~
well known in the art for conveying various inform~tion which it obtains from the micropro~essor 62 to the external controller 100 or for receiving progra~lng parameters from the external col,~Loller 100 whioh the receiver/transmitter 102 then conveys to thQ
mi~u~ocsssor 62 for ~torage in internal memory, ~uch a~
in time delay set stage 70, or in the a~oreman~i~ne~
external me~ory within enclosure 32.
The receiver/transmitter 102 include~ a transmitting coil 106 so that the receiver/tr~itt~r 102 and coil 106 form a communication means. Such communication means are well known in the art and may be utilized a3 noted above for receivin~ ro~
external to the implantable enclosuxe 32 and ~or transmi~ing data to the external con~oller ~00 ~ro~ the 1~
7 1 ~ 7 implanted enclosure 32. One such c lication sy~t~m i~
disclosed, for example, in U.S. Patent No. 4,586,508.
To complete the identification of the variou~
structural elements within the enclosure 32, the atr~l de~ibrillator 30 further includQ~ a charger and ~tosag2-capacitor circuit 76 o~ the type well known in th~ art which charge~ a storage capacitor to a predet~x~in~d voltage lev~l and a dischargQ circu.~t 78 for ~t~eh~r~ing.
the storage capacitor wi hin circuit 76 by a predetermined amount to provide a c~ .olled ~ q~
out~u~ of electrical energy when required to the atri~ o~
the heart. To that end, the ~ h~rge circuit 7~ i~
coupled to the first electrodQ ~4 and th~ ~o~S-~A"
el~ctrode 46 of the ~acond lead 36 for applying the cardioverting or defibril~ating electrical energy to th~
atria. Lastly, the defibrillator 30 include~ a depletable power source 80, such a lithium batte~y, ~or providing power to the electrical components o~ th~
atrial def~brillator 30.
The sense ampli~ier 50 and the R wave d~t~ctor 52 continuously detect ~he oc~ ence o~ ventr~c~
activations of the right ventricle 12. As ~isa~o~ed in the a~ore~entioned cop~n~ing U.S. Applicatlon~ S~r~al Numbers 07/685,1~0 and 07/856,514, her~in incorporat~d ~y.
25 : ref~rence, when the tim~ intervals between i~media~ely ~ sucoessive R waves indicate the probability o~ an epi~ode :: 17 7 1 ~ 7 of atrial fibrillation, the microprocessor 62 enable3 the atrial fibrillation detector 72, sense ampli~ier 54, and the analog to digital converter 60. If the atrial ~ibrill~tion detector 72 determines that the atria 16 and ~8 are in fibrillation and thus in need of cardiover~lon, the charge delivery control 74 cause the charg~r and storage capacitor circuit 76 to charge the ~tor~g~
capacitor within c~rcuit 76. The atrial de~lbrillator 30 is then ready to apply cardioverting electrical el~e~y~ to the atria 16 and 18 at the a~r~ iate time in a manner described hereinafter.
The synchronization detector 64, tha del~y timer 66, the comparator 68, and t~e time d~lay ~et ~tago ::
70 ~orm a delay mean~ 82 for delaying th~ application o~
the cardioverting electrical enerqy to t~e atria 16 and 18 of the heart 10 until after a predetermined delay ti~e ~ollowing ~he de~ection of a ventricular activation by the sensa amplifier 50 and the R wave detectox 52. The predetermined delay time is prevlously entered into th~
time delay set stage 70 ~rom the external contrcll~r 100 and through the transmitter/receiver 102 a~ pr~iou31y described. Also, he delay timer is reset wh~n the storage capacitor in circuit 76 reA~h~C full char~
The synchronization detector 64 pro~idQ a 25: pulse to the delay ti~er in re~po~ to ths pulse fro~
the R wave detector upon the detection of a ventricul~r :
~ 18 ' 7 1 ~ 7 activation. Prior to starting the delay timer h~
and in accordance with the a~or~mentioned cro~s referenced cop~in~ application~, Serial NumDers 07/68s,~30 and 07/856,514, ~ynchronization pulse counting may be employed wherein the synchronization dete~tor 64 first counts a predetermined numb~r, such as ~iVQ, consecutive R wave datect pulses from R wa~e det~ctor 52 to assure that therQ is still reliable detection o~ th~
lo Upon the gixth pulse from R wave det~ctor 52 (if such pulse counting is employed) or upon th~ ~irst pulse from R wave detector 52 (if such pulse counting i~
not employed), th~ ~ynchronization counter 64 provide~
its pulse to delay timer 66 to start the delay ti~r~
The comparator 68 then contlnuously compares th~ tl~e kept by the delay timer 66 to tha predeteL 1 n~ d~lay time stored in the timQ delay set ~tag~ 70. When the time kept by the delay timer 66 equals the stored delay time, the comparator 68 causes the charge delivery control 74 to provide a control signal t~ the di~charge circuit 78 for ~s~h~rging the cardiovertinq electrical energy stored in circuit 76 ~etween ele~o~es 46 and 44.
This applies the ~ardioverting electrical energy to tha ~ atria 16 and 18 of the heart.
: 25 As a result o~ the foregoing, ~he ~ardiovertin~ . .
electrical energy is applied to the atria when the atria . .
are in need of cardiovers.ion and a predetermined~d~lay time after one of the ventricular activation~
detected. The delay time i~ selected to be long t-,~ Jh to assure that the ventricular activation, whic~
ultimately ~tarts delay timer 66, is completed and ~hort enough so as to avoid cardioverting the atria during-th~
T wave which i ~l1~tely follows the v~lL~
activation in abo~t 250 millisecon~. A3 an exampl~, an~-without li~itations, the delay time m~y be in th~ rang~
of five to eighty mill1~eaQn~. Th~ rang~ of suit~blQ
delay times, o~ course, will dep~nd upon the par~qn heart physiology of a particular patient.
In co~trolling tha applica~ion or d~liv0xy o~
the cardio~erting electrical enerqy in the ~L~e~n~
r-nn~r~ it will be assured that th~ atria ~ not cardioverted during a partially completed ventricular activation, an R on T condition, or the vulnerabls p~r~od T wave of the heart. The present invention h~n~e-provide~ an improved atrial defibrillator and ~t~od wh$ch exhibits increased saPety in reducing the ri~k o~
inducing ventricular fibrillation wh~n cardioverting:th~
atria o~ the heart.
While a particular embodiment of th~ p~ t invention has been shown and described, modificatlon~ ~y be made. For examplb~ th~ delayed cardiov~rsion o~ th~
presen~ invention may be utilized to advanta~e in an 2~
7 ~ ~ 7 external atrial defibrillator wherein an ele~L.od~ or electrodes adhered to the sur~ace of th~ ski~ o~ a patient are e~ployed along with an R wav~ detector for detecting ventricular activations and sur~ac~ ~a~:
electrodes are utilized for applying th~ cardlovorting-i electrical energy to the atria of the heart. Such~
surface detecting and pad electrod~s are well known in~
the art. Hence, it i.~ therefore int~n~ed in the ~e-r~
claim~ to cover all su~h change~ and modification~ whi~h fall within the true spirit and ~cope o~ thQ inv~ntlon.
|Cooperative Classification||A61N1/3956, A61N1/3987, A61N1/395|