The Vecto rcard iogra phic Findings in Patie nts with Artificial Pacem akers * M.o·t OLGA ZONERA ICH, M.D.,** SMIL ZONERA IGH, .C.G,P.~ F M.o" AS, DOVGL H. AND ALBERT
Jamaica, New York
M
METHO DS AND 1IATER IALS
A:-IY REFERE NCES ARE FOUND IN PUB-
The Frank lead system was used in this study. The chest electrodes were placed at the level of the fifth intercostal space and the recordings were made with the subjects in a su p i n e position. Fronta l, horizontal and right sagitta l vectorc ardiog rams were displayed on the Cambr idge-V ector Dual Scalar screen, photog raphed on film with the Polaroid camera throug h a BeattieColeman Polexa adapte r. The vectorcardio~raphic loops were interru pted at the rate of 4-00 times per second , In all tracings, the inscription was interru pted hy the large end of the time dash,
lications which analyze clinical and electrocardiographic data in patients with artificial pacemakers, but only one study' has been done concerning the vectorcardiographi c findings in these patients. The purpose of this paper is to present t~c vect~rcardiographic findings in 20 patients WI t h artificial, intravenous, or implanted pacemakers. *F I rom the pcpartm~nt of Medicin e, The Long Hosplta l-Quecns Hospital Center !\sfJl~I'~d ro.J,·wlsh n, •
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**:\ssist~nt Visiting Physician. tA~SOl'lalt· Director of Medicin e . ~1)lreCtor of Medicin e.
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I . .... d hi ard ' ld man with ASHD, I : EI{'ctroc vect orcardIOgraphic findings III a 56 .year·o an IC ' 109rap I Z axis \" • k I . aortic In ffi' . .> 1 su IClt'ne}' an d cnlarg e d Ie [ t vcn tr .rc Ie. ECG ( top) shows complet e ;\. \i b oc , X. I ant ' th taken aft the P wa ve between er pacemak ous synchron the of spike e th shows a'nd ORScr, c ract·!ptk t.r was illse~ted to thc right , arucr iorly and infcriorly and displays illitiaf and c~~np .ex'l 1( - dvec~orca rdlOgral/l is oriented tion is C ,W, in the frontal plane and horiz ontal plane dircc of Sense delay, w '.,rullnha c,,~ ulcllon a n d C "C , III I c sagnta plane, FlOt'RI';
43(i
V" lu"," H, N " . .\
F I ~ I> I ~ (; S I~ I'ATIE:"\T S WITH ,\ J{T I F IC I ,\ L PACEMAKERS
April. l \l6K
Standard 12 lead electrocardiograms were recorded and also scalar tracings of the X, Y and Z orthogonal leads. The reference frame is formed bv a transverse coordinate axis which exte~ds from o point (the observer's right ) on the left of the reference frame to 180· on the right. The upper half is marked off in a counterclockwise direction in -30· segments and the lower half in a clockwise dire ction in + 30· segments. The orientations of the different vectors in the planar projections of the vectorcardiogram were ex pressed in terms of reference to the zero point; situated to the left in the frontal and horizontal planes, and anteriorly in the right sagittal plane. Thus, the + 90· is located inferiorly in the frontal and sagittal planes and anteriorly in the horizontal plane. The study group consists of 20 patients (ten men and ten women), who ranged in age from 56 to 81 years. They had either arteriosclerotic heart disease (ASHD ) or hypertensive cardiovascular disease \
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( H e \ 'D ) with repeated attacks of AdamsStoke s s yndrome before insertion of the pacemaker. Five had angina pectoris for man y year s; onl y two gave a clinical history of myocardial infarction, One had carcinoma of the larynx with possible involvement of the ca rotid sinus; severe brad ycardia, nodal rhythm and severc Adams-Stokes attacks. The vectorca rdiograms were recorded as earl y as two days after insertion of an artificial pacemaker, and as late as two and one-ha lf years after its insertion . For intravenous pacing , Ch ardack bipolar electrodes were placed at the apex of the right ventricle (nine pat ients ) , In 11 patients, the electrodes were implanted at the apex of the left ventricle as close as possible to one another, The distance between the two electrod es was 1.0-1.5 em, A synchronous type of pacemaker (Atriocor) was used in two patients, An asynchronous type of pacemaker, Chardack or Medtroni c, was used in nine patients.
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S 2: Electrocardi ographic and vectorcardiographic findings in a 71-year-old man with ASHD and normal sized heart. EC( ; ( to p ) befor e the impla nta tion of an ~synch ron"lIs pa cem aker, sho ws cOlllpl ele A- V bl ock . X , \' an d Z lead s ( lo p left ) taken simull alll'ollsl)', wlt!1 the \-enorc a nho!-:ran~ s~uw th e ma xim al QRS ve ct or to he d irec ted to the r ig ht , an teriorly a nd J,nfcr! orJy. The QRS. loop IS similar 10 th at seen in Fig I except for d isplacement uf the J po in t. T he sag it tal plane was. ~Illpl..ficd (b ottom lr-ft }. Thl' vector or th r- artificial impulse is very well illustrated in all threr pla nes, I'h e init ial cond uc tion dela y ( delt a wave ) foll uws the artificial vec tor. FIGURE
Diseases l)f
ZONERAICH. ZONERAICH A:-II> DOUGLAS RESULTS
Table 1 summarizes the electrocardiographic and vectorcardiographic findings in group 1 (the patients with intravenous pacemakers ) . In six, the electrocardiogram showed a complete A-V block and right bundle branch block (RBBB) pattern before insertion of the pacemaker. One had a complete A·V block and incomplete RBBB, another had an electrocardiogram w hie h showed a regular sinus rhythm interrupted ~>. prolonged diastolic pauses suggestive of sinus arrest as the mechanism of the AdamsStokes attacks. A marked bradycardia with nodal rhythm was recorded in one patient with carcinoma of the larynx . The chest x-ray film in six patients showed moderate to significant enlargement of the heart . Vectorcardiograms: The no rm al initial deflection of the QRS loop to the right and
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anteriorly was absent in all the vectorcar, diograms. It was recorded to the left, supe, riorly and posteriorly in six cases; to the left, posteriorly and inferiorly in one cas~ ; to the left, anteriorly and superiorly in tWa cases. Orientation of the Maximal QRS Vec. tor: The maximal QRS vector in the fron, tal plane was oriented between + 15° anQ -100°. In the horizontal plane, it w~ oriented between -40· and -90·, and it) the right sagittal plane the maximal QRS vector was oriented between -105· and
+170°.
Inscription of the QRS Loop: In th~ frontal plane the QRS loop had a counter. clockwise inscription in four cases and C\ figure of eight configuration in the remaining five. In one of the cases a distorted loop with a double figure of eight configuration was recorded. In the horizontal plane, the QRS loo}:>
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F'Gl'RE ~ ; Electrocardiogra hi I . and normal si~~d heart Aft P .c an<. vectorcardIOgraphic findings in a 7 I -year-old woman with ASHD mal QRS veni;r dirr'ct"'c! t Jns?rtlon of t~e pacemaker, X, Y and Z leads (bottom) show the maxio r dirc('!j'>!l is C C' w. : t r!ght, postcnorl}' and superiorly. The QRS I<)OP is v..ry di storted. Sense . """ In t rc onzomal plane and C.W. in the sag ittal plane.
('h 'i h
Volume n, No.4 April, 1968
1'1:-:D1N<;S I~ PATIENTS \\'IT1I ARTIFICIAL PACEMAKERS
was displayed as a figure of eight config-
uration in five cases. In three of these, the direction of inscription was clockwise-counterclockwise. One had a clockwise inscription. In the remaining cases, the direction was counterclockwise. In the right sagittal plane, the QRS loop showed a clockwise direction in eight cases and was projected as a figure of eight, with counterclockwise-clockwise direction in one case, Conduction delay was manifested in the QRS loop by closely spaced time dashes. It was found in the initial portion in some instances, and in the terminal portion in most. The findings are summarized in Tahle 1. SoT l.T ector: In four cases, the QRS loop failed to close, indicating the presence of an SoT vector directed to the right, anteriorly and inferiorly. Patients with Lmplanted Pacemakers ( 11 cases): Table 2 summarizes the electrocarL
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d i 0 g I' a phi c and vectorcardiographic findings of this group. The electrocardiograms before implantation of the pacemaker showed complete :\ _\' block in all the patients. Six showed a pattern of right bundle branch block ~nd in three, the QRS complex had a duration less than 0.10 seconds. In two cases a left bundle branch block pattern was present. One (Case 18) had electrocardiographic findings compatible with subendocardial infarction. The vectorcardiograrns showed minimal displacement of the J point in seven, The maximal QRS vector was oriented in the frontal plane between -85· and + 120·; in the horizontal pl a n e between -80· and +150·; in the right sagittal plane between -130· and + 145·. Direction of Inscription: In the frontal plane, there was clockwise direction in f~ur cases and in three cases the vectorcardlO-
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F ,~: Electrocardiographic and \'cctorcardiogr:lphic findings , after insertion of a synchron ous pac~ maker, in a 67-year-old woman with ASHD and c1l1~rgcd hc~rt. . The .~ ll1kc of the artificial stimulus IS evident fullowing each P wave , Thc vectorcardiogram IS \'';1")' dl~lollcd." !tl~ .u n us~ul dlSJllaccmel~t of till' .T point. The initial vectors point first tu the left and posteriorI )'. I'h ere IS init ial , middle and terminal delay.
FIGURE
.1--'1.0
Disease s of the Chest
ZONERAICH. ZONERAICH AXD DOUGLAS
gram displayed a figure of eight configuration. In the horizontal plane, a figure of eight was recorded in four cases. Clockwise inscription was present in two cases and counterclockwise in one. In the sagittal plane the sense of direction was clockwise in four vectorcardiograms; figure of eight in two; and counterclockwise direction in the last one. Conduction delay Was present on the afferent limb in four vectorcardiograms. The last ~hrec cases manifested a significant conduction delav. on th e miiddie temporal segment of the QRS loop. The .T loop is opposite the mean QRS vector m all these cases. A. quantitative analysis of the T loop
o~)tamed with higher magnification will be
dIscussed elsewhere.
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The mechanism in the production of the vectorcardiographic pattern in patients with artificial pacemakers can probably be reduced to the abnormal depolarization of the mvocardium, Th~ sequence of myocardial activation of the right and left ventricle with com-
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The vectorcardiograms m the last four cases showed an unusual displacement of the J point. The maximal QRS vector could not be determined because of the unusual pattern of these loops. The QRS loop was located mainly in the right antero-inferior quadrant in three cases and in the right postero-inferior in one case. The sense of direction was clockwise in all three planes except for the sagittal plane (Case 19), where the QRS loop was very distorted.
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'; ~ 5: Electrocardio ra ihic enlarged hcart. X. Y and ~ lead and ve~torcardiographic findin gs in a 70-year.old man with ASHD and shows the maximal ORS veer s taken. slInultaneously with the vee after insertion of an I-V pacemaker as a figure of l'i~ht i~l the f ort bedtre<:ted to the It'lt supe riorly and posteriorly. The vee is recorded tion delay in (h~ afferent anrdo n far an l,oflzo n ta1 planes. The QRS 1001> fails to close . There is cond uce crent imbs. FI(; I'R F.
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Volume H . N... Al'ril , 1968
.j
FIi':DI N (:S IN PA TIENT S "VITH ARTIFI CIAL PACEMAKERS
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FIGt:R~ 6 : Ele~trocardiographic and vectorcardi ogra phic find in gs in a 71-yea r-old woman with HCVD and wit h a considerably enlarged heart. The ECG ( top ) be for e in sertion of ~he I-V pa cemake r s~ows com plete A-V block: X , Y and Z axis takcn sim u lta neo usly with the \'cctorcardlUgram show. the maximal QRS \,,·~·tor to be d irected post ero-superiorly and to the left. Not e the ball ooned QRS loop III t~c f':Ont~1 and horizontal planes and the co nd uction delay in it s aflcrr-nt lhu b and mid-portion. Sense of dlrecllo.n IS C.C.W . In till" fro.mal and ho rizontal planes and C .W. in th e sagittal plane. Horizontal and sagittal planes recorded With double magn ification .
I C und ucti o n Delay
TABLE
Max imal QRS Vect or Case F H S X o. Planes
Sense of D ire ction F S H Planes Fig of Fig of CW eig ht eight
_80 0
-90 0
-150·
2
-75·
-80·
-170 0
CCW
CW
CW
3
-30·
-50·
-135·
CCW
CW
4
-75·
-55·
-160 0
Fig of eight
F ig of eight Fig of eight
5
-100·
_90 0
-160·
6
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-40·
-135 0
7
-85·
- 80 0
-1 30·
8
+15 0
_ 70 0
+170·
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EC (; Findin gs Before Insertion of Pacemaker
RSR with long pauses due to sinus arrest Nodal rhythm. Initial and afferent limb QRS less than 0.10 seconds Gcn eralized Complete A-V blo ck with RBBB pattern Afferent an d Complete /I.-V block efferen t limb with RBBB pattern In itial and middle
Affere nt an d Complet e A-V block efTet'l'nt lim b with RBBB pattern Com ple te A-V bluck Fig of M iddl e and with RBBB pattern te n n in al eight ei~ht C om plete A-V block Init ial middl e CW CW/ an d n -rminal with RBBB pattern CCW Afferent and Complete A-V hlork F igof CW dTrrr nl lim b with RBBB pa ttern cicht ···C:C:\ V· -- C W ~f idtn~ Compl~i:r A-V l~·lork . n-rm inal incomplete REEB CCW/ CW Fi g of
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pa tt e rn
Heart Size by X- ra y Enlarged Normal Normal Lt·ft ventr icle slightly enlarged Enlarged Enlarged Enlarged No rm al
COl)~lerahl )~
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Ah h rcv ia tions : F=Frontal: H = H ori zon tal : S=Sal(ill al : C:\ V=CI(\rk ",i s(": CC W = Co lllltr rd oc k",isl': R SR = R,'glllnr si rrus rh yth m : RnnB=R i!:ht h und l.. hrauch block.
ZO:'\ERAICH . ZO:'\ERAICH A:'\O DOUGLAS
plete heart block has been carefullv studied ~)y many investigators. In an acute experInlCr: t on dogs, Lister et all paced the epicardial surface from different ectopic pacemaker .sites. Each pacemaker site produced a specific pattern of activation. In, patients with an artificial pacemaker, ~he Impulse generated by the pacemaker
unplanted at the apex of the left ventricle follows an ahnormal pathway and produces an .abnormal pattern of vectorcardiograms. It IS. known that the velocity of the con~uctlOn system is variable in the specific tissue. In the Purkinje system it is 2-4 Mj second, but in the muscle fiber it is only 0.5 to 1 M/second .3•• The amount 0 f muscle mas.'i "ctivated before the impulse reaches the "~p eCIif c conductIOn . . pathways WIU del a" and di h IStort t e usual vectorcar. : dlO!-{raphlc pattern. In Our p at i e t . h . n s WIt Implanted pacemakers , the vect orcardiiogram displays . two
TABLE
C a se No.
Maximal QRS Vector
F
H
Planes
S
10
+175'
11
+170'
12
+120' +150'
13
-140'
140'
130'
~ 100'
-80'
130'
-85'
-90'
-ur- 120'
130'
100'
165'
15
17
Sense of Direction
F
160' +150'
cw
140' +170'
CCW
+45'
CW
cw
2
S
Conduction Delay
cow
CW
Fig of eight
CW
Fig of eight
Initial and terminal Initial middle and terminal Afferent and efferent limb Middle and terminal Initial and middl e Initial middle and terminal
CCW
Generalized
c:w
CCW/ CCW CW CW Fig uf eight CW Figof eigh t Very Distorted loop
major patterns: (a) with the main QRS loop directed to the right, anteriorly and inferiorly, with minimal displacement of the J point ( Fig I), or with marked displacement of the J point ( Fig 2) ; (b) with the main QRS loop directed to the right and posteriorly (superiorly or inferiorly) (Fig 3 and 4). The findings in Group :\ arc different from the classic vectorcardiographic pattern of right bundle branch block. The vectorcardiograms presented in figures 2 and 3 are similar to those found in right ventricular hypertrophy wit h conduction dela y. ~ There is no ev ide n t explanation for the observation that in some cases with implanted pacemakers at the apex of the left ventricle, the QRS loop is displayed posteriorly (Fig 3 and 4). No previous myocardial infarction or chronic lung disease" was suspected in these patients. The manner in which the pre-existing conduction
H
Planes
cw
ccw
c:w CW
Di seases of the Chest
ECG Findings Before Insertion of Pacemaker
I Ieart Size hy X-ray
Complete A-V block, Nor mal with RBBB pattern Complete A-V block , Enlarged with LBBB pattern Complete A- V block. Enlarged with REEB pattern "'ft ven tric le Complete A-V block , :\lol'lnal with RHBE patll·".:..f1;.;,.I_--=--,--_~_ Complete A-V bluck . En larged with REBB pattern Complete A-V block, Enlarged left ventricle ORS less than ()~1O sec Complete A-V block. Enlargvd with RBBB pattern
Complete A-V block. Mod erarclv enlarged . QRS less than left ventricle 0.10 sec 18 c:w CW C\V Initial and Complete A-V block. Enlarged QRS less than O. I 0 terminal sec. subendocardial infarction 19 CW CW Afferent and Complete A-V bloc k. Moderat ely QRS less than r-nlann-d effr-renr limb 0.10 sec C:W CW CW Initial and COlli p)..tc A-V blo ck , EnJa r1-:l'd - "- - t('rminal with LBnR patlPfIl :\hlm'\'ialiolls ' F- Fr
cw
CW
Terminal
V"lumc 53. No. ·1 April. 1968
FlNm:'\'c:s 1:'-: PATIENTS WITH ARTIFICIAL PACEMAKERS
delay in the left or right bundle branch did influence the vectorcardiographic pattern after the insertion of the pacemaker, is difficult to ascertain, The unusual displacement of the J point, which we encountered in four of our cases was explained' on the basis of increased distance between the implanted electrodes. In our experience, there were large variations in the displacement of the J point even at a constant distance between the implanted electrodes. It is known that the conduction delay recorded on the afferent and efferent limbs is due to abnormal depolarization of the myocardium, We believe that the initial conduction delay (delta wave) recorded in five of our patients with implanted pacemakers and best seen in Fig 2 is due to initial slow conduction through the muscle mass until the artificial stimulus reaches the specific pathways, The vectorcardiographic pattern in patients with I-V pacemakers resembles the classical left bundle branch pattern1 (Fig 5), but in six of nine cases the maximal QRS vector was directed in the frontal plane between -70· and -100·, As is known, in left bundle branch block, the activation of the muscle fibers on the left septal surface is a direct result of excitation spreading from the subendocardial Purkinje network." Multiple accessible interventricular pathways, superficial as well as deep, will spread the electrical impulse to the left ventricle," The displacement of the maximal QRS vector closer to -90· in the patients described (Fig 5), can be explained by the location of the ectopic impulse (artificial pacemaker) at the apex of the right ventricle. It is pertinent to note the abnormal ballooned loop in the frontal and horizontal planes with marked conduction delay in the middle temporal segment of the QRS loop in one of the cases (Fig 6). This patient had a considerably enlarged heart. The size of the heart undoubtedly plays a role in determining the general configuration and
-1··'·1
direction of inscription of the vectorcardiogram. In the cases with a clinical history of myocardial infarction, only an anatomic co'rrclation can fully prove the role played hv mvocardial damage in the configuration of th~ vectorcardiographic pattern in patients with artificial pacemakers. SUMMARY
The vectorcardiographic findings in 20 cases with artificial pacemakers (intravenous or implanted) are presented. In patients with implanted pacemakers, the vectorcardiogram displays two major patterns: (a) the main QRS loop is dirccted to the right, anteriorly and inferiorly; (b) the QRS loop is located mainly in the right posterosuperior quadrant. There is marked displacement of the J point in several cases, In the patient w~th intravenous pacemakers, the vectorcardl?graphic pattern resembles that found III LBBB. The abnormal depolarization of the myocardium as a cause of this vectorcardiographic pattern is stressed. These data contribute to a better understanding of aberrant cond.uction because the origin of the impulse IS known. The authors. wish to, than~ DeSantis for her techl11caI aSSlStan~( ;ln~is acknowledge the secretarial assistance of MISS Adrienne Sugerman. :\CK;-';OWLElJGMENT:
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RES{;~(EN
Se presentan los resultados de la vectorcardio.. r'o casas g'1•• I.',en ?O _ . . , portadorcs de• reguladores del ritmo rardiaco (inlrawnosos 0 impluntados}. En los pacientes can regulador implallt.~d~ 1'1 vcctorcardiograma m u e sr ra dos c~l:a(:lCl'lstIC:~S , , less :(a) hacia pnnClpa , cl complejo . , QRS. dirigido . . la derechn, anterior e lnferiormente; (b) el (omlejo QRS situado lIlarOrll1ClllC :11 el ruadrante f,osterO-sll perior derccho. Ell varios casos 5t' Dbservo till desplazamiellto marcado del punto J. En los sujctos can rCl?;lIlador intra,venoso el trazado wClorcardiognlfico se ase111CJa al dd hloq ueo de rama izq uicrdo. o. , Se desraca el 1'01 dc 101 despolarizacion 011101'111:11 del miocardia C01110 causa de esie peculiar trazado vcctocardiognHico. Estas comprohacioncs contribuyen al mcjor entcudimicnto de las abcrracionos de conduccicn del miocardio, )';1 que el origcn dcl impulse es conocido.
444
2
3 4
5
Diseases 01 the Ch"Sl
ZONERAICH, ZONERAICH AND DOUGLAS
REFERENCES PESCADOR, V. L. AND GARCIA-FERNANDEZ , J. L .: Vektorkardiographische U nt<:nuchung des Herzens bei implantiertem Schrittmachcr (Pacemaker), Verhandl der Deutsch, Gesellshaft fur Kre islauff orsch, 30: 239, 1964. LISTER, J. W., KLOTZ, D. H., JOMAIN, S. L., STUCKEY, J. H. AND HOFFMAN, B. F.: Effect of pacemaker site on cardiac output and ventricular activation in dogs with complete heart block, Am. ]. Cardiol., 14:494, 1964. HOFFWAN, B. F.: Physiology of A-V transmission, Circulation, 24:506, 1961. SCHER, A. M. : The sequence of ventricular excitation, Am. ]. Cardiol., 14:287, 1964. BAYOAk, 1. D., WALSH, T . J. AND MASSIE, E.: A vectorcardiographic study of right bundle branch block with the Frank lead system, Am.
]. Cardiol., 15: 185, 1965.
6 BADARAU, G. AND ZONERAICH, 0 .: A vector-
cardiographic study in patients with right ventricular hypertrophy secondary to chronic Iu.ng d isease, Rum. Acad, Med.-lssay, I: 39, 1958_ 7 WAl.LACE, A. G., ESTES, E . H ., JR. AND ~I{c CALL, B. W .: The vectorcardiographic findinss in left bundle branch block, Am. Heart j..
63: 509, 1962.
!I VENEROSE, R. S., SEIDENSTEIN, M., STUCKEY, J. H. AND HOFFMAN, B. F.: Activation of su.benducardial Purkinje fibers and muscle fibers of the left septal surface before and after left bundle branch block, Am. Heart /., 63: 346.
1962. 9 SCHER, A. M. AND YOUNG, A. C . : Spread
of excitation during premature ventricular systoles, Cite. Res., 3 : 535, 1955.
f.'ur r~-prints. please \\'~ite: Dr. Zoneraich, Que-eo ns Hospital Center, JamaIca, New York.
CARDIAC MOTION Diagnostic ultrasound was used to record the movement of the anterior and posterior heart walls in 23 patients with proved pertcardtal effusion. Fltteen of these patients demonstrated heart-wall mouon that could not be distinguished from the normal pattern. Two patients with acute cardiac tamponade t'xh lbltcd markedly reduced cardiac motion. The ~It~asoundcardiograms In the remnlning six patients Ihdl.elltcd posterior displacement or the entire heart durmg systole. The extent or this cardiae displacement varied . f'ive of the six patients With excessive
cardiac motion hlld malignant perteardial effusion. and four of the six had clinical ev idence of cardiac tamponade. The results of this study SUbstantia 1;e the theory that excessive cardiac motion may OCCUr in som e patients with pericardlal effusion. Object! VI' ev idence Is also provided In support at the pOSitional etiology of the electrical alternatlon associated with pericardial effusion. FEr GJ,N lM lIM , H •• z,,,y. A . AND GRADHORN , l. L. : Card i a.,'
motion in p a t i e n t s with 34:611, 1967.
p~ri('ardia.l
effusion.
Cir~IIJa'i(;~~ .
CORONARY CINEANGIOGRAPHY Examlnatiun was made or sta ndard lead 111 of .t he eleetrocardlogr-dm rt'corded during selective right and. left coronary ar ter y Injections of dlntrteonte SO~ l u m IHypuque-M) 75 per cent In 107 patients. Ldt coronary artery Injection caused the mean frontal plane QRS vector to shUt transiently to the left and T wave vector to shift toward the right . Right coronary artery Injection caused shifts or the QRS lI.nd T wave vectors In the opposite directions. OcclUSIOn or one main COronary artery caused these
ECG changes to bc m in imal Or absent. Transien t sinus brndycardla was common with Injection 0 r either coronary nrterv. Serious arrhythmlaa were rare. The electrocardiogram recorded during setee-; tive coronary artl.'riol!ral,hy can !th'" InfornUltio~ useful during the procedure ItseH as well as durlnl;r the subsequent interpretation of the angiogram. MA<:ALP1N, R. N.. WEIDNER, W. A., KATTUS, A. A., JR._
A:-Ill HANAFEE, W. N . : EI'~lro<:ardiographic changes dUlInlo.:: selective coronary lineangiography, Circulation , ~4:6n, 19"- .