(Received Jul 1;accepted for publication October 17, 1968).
ADDRESS: (AR-C.
)
Hospital de Ni#{241}os, Servicio de Cardiologia, Buenos Aires, Argentina.ADDRESS FOR REPRINTS: (RAM.) Cook County Children’s Hospital, 700 5. Wood Street, Chicago, Illinois 60612.
Pr.mAmIcs, Vol. 43, No. 3, March 1969
430
ACCELERATED
NODAL
PACEMAKER
Alberto Rodriguez-Coronel, M.D., and Robert A. Miller, M.D.
Department of Pediatric Cardiology, Cook County Hospital and the Department of
Pediatrics, University of illinois College of Medicine, Chicago
ABSTRACT. Acceleration of the nodal pacemaker
can occur in children as a result of inflammation,
drug toxicity, or trauma. The rapid nodal rate
leads to A\T dissociation which may persist for
days. In acute rheumatic fever a persistent nodal
rate in excess of 80 per minute seems to be a
highly specific indication of carditis often preced-ing other evidence of cardiac involvement. This ar-rhythmia is frequently seen after cardiac surgery, particularly when the atrial or the ventricular sep-turn is the site of the operation. An accelerated nodal Lacemaker can also occur due to (ligitalis
toxicity. Hypokalemia appears to make children
with congenital heart disease more susceptible to
this arrhythmia. The A-V dissociation caused by an accelerated nodal pacemaker must be differentiated from the A-V dissociation seen in normal children with sinus arrhythmia. The cardiac surgeon should recognize that, although there may be complete A-V dissociation, he can separate this entity from surgically induced heart block because the nodal rate is over 80 per minute. Pediatrics, 43:430,
1969, ARRHYTHMIA, NODAL TACHYCARDIA, A-V
DIS-SOCIATION.
CCELERATED iiodal pacemaker is an
ar-rhythmia produced by stimulation of
the A-V node resulting in A-V dissociation with an abnormally fast nodal rate. The ar-rhythmia is associated with specific condi-tions in childhood, usually acute rheumatic carditis, an episO(le of digitalis toxicity, or cardiac surgery. This entity has been ann-lyzed in detail by Pick and Dominguez,1 who
described it as non-paroxysmal A-V nodal
tachycardia in order to differentiate it from
tile usual paroxysmal tachycardias. This
dif-ferentiation is important since the acceler-ated nodal pacemaker is always associated
with underlying pathology, whereas the par-oxysmal supraventricular tachycardias
usu-ally occur in normal children.
This type of nodal tachycardia has been reviewed by Castellanos and Lemberg2 and
by Dreifus and co-workers,3 and it has been
experimentally produced by Fisch and associates.4 Although this arrhythmia is fre-quently seen in sick children, information available to pediatricians concerning its diagnosis and significance is inadequate and somewhat confusing.
The marked sinus arrhythmia of normal
children is not infrequently associated with
brief periods of A-V dissociation. The long
period between P waves allows the A-V node to discharge, producing a ventricular contraction. The next normal sinus P wave
may find the ventricle refractory, and
be-fore the following P wave arrives the node
may escape agam. The child has thus had
an episode of nodal rhythm or A-V
dissocia-tion. The rate of these nodal beats is
usu-ally between 50 and 60, never faster than
70 to 75 in normal infants. This study is
concerned with those children whose nodal rate has been accelerated
(
over 80 per mm-ute)
by disease, drugs, or surgical traumausually resulting in A-V dissociation which
persists for days.
MATERIALS AND METHODS
Fifty-four cases have been reviewed. The
age range of the children was from a few
days to 15 years. In each child serial
elec-trocardiograms were performed permitting evaluation of tile duration and evolution of this arrhythmia. From previous data on
congenital A-V i)lOck from this
depart-mellt,5 it ‘as determined that the rate of
ARTICLES
11. 2- 65
11-4-65
Ftc. 1. Child with acute rheumatic fever. The atrial rate is 123 per minute. The node is accelerated to
103. There are no ventricular captures, even when the P wave occurs at a good interval from the QRS.
Two (lay’s later, when the acceleration of the node is no longer present, sinus rhythni is I)resent with first
degree A-V block (PR, .26 Ild ). The first degree block explains the previous lack of captures.
vith a range from 32 to 60, and that exer-cise or excitement
(
e.g., crying)
increases this rate by an average of no more than 10 to 15 beats per minute. Even in the infant who is crying vigorously, the basal rate of the normal nodal pacemaker was neverfaster than 70 to 75 beats per minute.
Pre-vious experience ill adults sets this limit for
the normal nodal rate at approximately 70
beats per minute. We consider a nodal rate
above 80 as abnormally accelerated, as
have others.
Of the total 54 cases, 15 occurred during an episode of acute rheumatic fever. The findings in these cases
(
Group I)
are sum-marized in Table I. The onset of the ar-rhythmia was very early in the attack ofrheumatic fever. The patients almost
al-ways arrived at the hospital with the
ar-rhythmia already present. The duration was relatively brief and averaged 4 days, with a range of 1 to 8 days. In 9 of the 15 cases, tile appearance of an accelerated nodal pacemaker preceded specific evidence of rheumatic carditis. With a few exceptions, these patients later developed murmurs of acute valvular involvement
(
Fig. 1).0 Tables II, III, and IV are included in tile
re-print of this article.
Group 11* consisted of 22 patients in
whom acceleration of the nodal pacemaker
was associated with digitalis therapy. In five of these patients, clinical evidence of severe digitalis toxicity was present. In nine others there was evidence that digi-talis had been given in some degree of
ex-cess
(
Fig. 2)
. However, eight of thepa-tients, all with important congenital heart
disease, had therapeutic doses of digitalis or even less than the usual dose. Three of the Group II patients were found to have hypokalemia. Eleven of the 22 had some manifestation of A-\7 nodal block in addi-tion to the accelerated nodal rate. Two of the patients had atrial fibrillation.
Group lIP consisted of 15 patients in
whom an accelerated nodal pacemaker
ap-peared following cardiac surgery. In the majority of cases, the atrial or the ventricu-lar septum was the site of the operation, usually for the closure of a septal defect. In one patient an atrial septotomy
(
Blalock-Hanlon)
was the surgical procedure, and in one case of congenital mitral stenosis the mitral valve was approached through the atrial septum. One patient had a right yen-triculotomy only, followed by an explora-tion of a single ventricle. Except for oneTABLE I
Gitou i 1-ActITE RhEUMATIC FEVER AND ACCELERATED NoDAI PAcEMAKER
Age Atria! Venir. PR D,,ration
,
. . ‘ .I,aocialedCase L( G Mauzfeslatlo?L ( (luse.? ‘
(yr) Rale Rale Interrat (da) Findzng.
II 115 100
,
16 1 Iiitermitt.eiit A-V disso- Acute rheumatic Mild mitral iiisuflicieneyelation carditis during acute stage; no
longer present
chru-cally
3 15 96 10.5
,
16 5 Incomplete A-V dissocia- Acute rheumatic Mild mitral insufficiencytion carditis
5 9 81 81 RP .04 3 Non-paroxysmal nodal Acute rheumatic Aortic insufficiency tachycardia with retro- carditis
grade conduction to the atria
7 5 Ave. 94 .14 8 Intermittent A-V disso- Acute rheumatic Mitral insufficiency
mur-115 ciation carditis mur detected days
after arrhythmia started
8 10 105 86’
,
to .40 1 Second degree A-V block Acute rheumatic Mitral insufficiency(when con- and accelerated rate of carditis
(luCted) nodal escapes (recurrence)
II 11 IO 103 6 Complete A-V dissocia- Acute rheumatic Transient mitral
insufli-tion due to accelerated carditis ciency nodal pacemaker and
A-V block
15 13 F1.5 Ill
,
14 4 Intermittent A-V disso- Acute rheumatic Mitral insufficiencymur-ciation carditis mur during acute stage
(recurrence)
19 13 Ave. 86 .18 3 Intermittent A-V disso- Acute rheumatic Mild. transient mitral
in-90 ciation carditis sufficiency; no murmur
at present
Ql 13 150 FtO .16 1 Incomplete A-V dissocia- Acute rheumatic Mitral insufficiency and
tion carditis aortic insufficiency
de-tected first in third week after onset
13 83 83 0 2 Non-paroxysmal nodal
tachycardia with
retro-grade conduction to
theatria
I 53 83 0 6 Intermittent A-V disso- Acute rheumatic No valvuhtr involvement
ciation carditis
14 90 100 .12 Not recog- Incomplete A-V dissocia- Acute rheumatic No valvular involvement
ni-ted tion carditis
(recurrence)
4 10 90 Ave. 0, 18 Not recog- Sinus arrhythmia with Acute rheumatic Mitral insufficiency
81 niied first degree A-V block carditis
with accelerated rate of nodal escapes
45 13 Ave. 100 .3 3 A-V dissociation due to Acute rheumatic Chores, no valviilar
in-80 accelerated nodal pace- carditis volvement
maker, some degree of (recurrence)
A-V block
45 13 lii Ill RP .14 Nodal tachycardia with
retrograde conduction to atria
46 8 88. Not reeog- Sinus arrhythmia with Acute rheumatic Subsequent mitral
insuffi-llLied accelerated rate of nod- carditis ciency
alescapes
48 11 111 Ill 0 Not recog- Non-paroxysmalA-Vnud- Acute rheumatic Mitral insufficiency
mur-nized al tachycardia with earditis mur detected 4 days
retrograde conduction later
to atria
+-death; Atrial rate-beats per minute; Ventr. rate-beats per minute; RP or PR intervals-seconds; ‘a-not conducted sinoatrial
.
I
.;#{149}1
I. :1$ I L I I
I
-±---:---,----±H4-H--4--t---
- -Ji
P±4
4
IIIiILI±I1I1iTi1I
1IT:1II:III::::
- - .-_i_-l--:--._LH_._ -4-+-
H-
---c
E
Ftc. 2. Case 9. Lead II in a patient who had digitalis toxicity’. The drug was withdrawn four days
be-fore this tracing. Intermittent A-V dissociation is seen when the second to the fifth P wave fail to conduct and the nodal pacemaker escapes repetitively at an accelerated rate of 83 per minute. The sixth P wave is able to capture the ventricle after delayed A-V conduction (PR interval .28 second because it falls in the relative refractory period of the A-V junction ). The following atrial impulse conducts with a PR of
.16 seconds.
with accelerated nodal pacemaker had
some surgery or trauma affecting the atrial or ventricular septum. In each of these
chil-dren the accelerated nodal pacemaker was found to be present immediately following the onset of regular cardiac action. Since the acceleration of the pacemaker usually resulted in a complete A-V dissociation, it
was important to differentiate the
arrhyth-mia promptly from surgically produced
atrioventricular block. The ventricular rate ranged from 83 to 160, with an average of
107. Duration of the acceleration of the
node ranged from 1 day to 14 days, with an average of 5 days. There was only one case in this group in which atrioventricular block was present. The pacemaker in this case appeared to be an idioventricular one, which was considered to be accelerated.
Group IV consisted of eight patients in
which the acceleration of the nodal
pace-maker was associated with various or
Un-known causes
(
Table IV) . Three patients inthis group had congenital heart disease and
an accelerated nodal pacemaker which oc-curred spontaneously with no apparent
cause. In another, the arrhythmia appeared
following electrical countershock used to terminate paroxysmal tachycardia. The
ac-celeration of the node lasted for only 30
minutes. Two cases began during or follow-ing cardiac catheterization. There were two in which an electrolyte imbalance was
pres-ent.
DISCUSSION
In 1957 Pick and Dominguezt described
the non-paroxsymal forms of tachycardias
as due to a pathological enhancement or acceleration of an otherwise naturally occur-ring or “passive” rhythm. The electrocar-diographic features are usually clearly
de-fined, but they may vary with associated disturbances in sino-atrial impulse forma-tion, the presence of atrial fibrillation, or al-terations in atrioventricular conduction, and with the presence of other ectopic pace-makers.
There are many ways in which the ac-celerated nodal pacemaker may be mani-fested in clinical electrocardiography:
434
80 per minute
)
in children with sinusar-rhythmia
(
Fig. 1)
. It should beremem-bered that nodal escapes can appear in nor-mal children when the sinus rate slows in
sinus arrhythmia. 1)tlt these nodal escapes
occur at a much slower rate than in the
children considered here.
2. Incomplete A-V dissociation
(
without I)lOCk)
; this is a slightly more severemaui-festation, in viiih the accelerated node is
coiisistentlv faster than tile sinus rate dll(l
tilus tile nodal rIlVthlfl persists since tile
5illUS 1)acerndker cannot i)reak in to capture
tile ventricle. It is called incomplete A-V
dissociation because occasional sinus beats
are able to capture tile ventricle.
:3.
Complete A-V dissociation(
with block)
. Here no captures are seen andthere is coIl-l1)lete (lissociation because of
12
2-17-64
the persistent acceleration of the nodal
pacemaker. It may occur even though the i)lOck is not complete, since captures may later l)e demonstrated when the
accelera-tion has disappeared.
4. Non-paroxsymal nodal tacilvcardia vith retrograde conduction to the atria
(
Fig. 3)
. Here the nodal impulse issimulta-neously conducted to tile ventricle and
ret-rograde to the atria. Tile P wave is seen following the QRS or simultaneous with it.
There is no evidence of A-\ dissociation
since I)Otil chambers are obeying the one
pacemaker.
Although most cases of accelerated nodal
pacemaker in cilildren follow these simple
I)ltter1lS and are easily recognized, it
should be rememl)ered that, under certain
circumstances. the arrhvtiiniia may be quite
A
AV
V
12
A
AV
V
s\\ s
S
\\\
S
s\\
2- 26-64
Fi;. 3. Cast’ 10 following digitalization ( 2/ 17/64 ). Uneven atrial rhythm, probabl- sinus arrest. Tht few P ‘-a\-es are normally colldtlcte(l (no A-V block ). Some P waves vitli unustial contour are trout ,tn
t’t.’topic .ttrhtl pa(’emakt’r (represented as (lotted arrows ). During sinus arrest the Ilode escaies it ,tti celerated rate of 100. Nine (lays later ( 2/26/64 ) with tile patient still or’ digitalis, the nodal tachvcar(lia (‘OtltiIltIeS, vitli retrograde (-on(luction to the atria. The R-P interval is slightly prolonged (retrograde first degree A-V block ). In this figure as in Figure 4, A is the sinus impulse, A’s7 is the atrioventricular
complex, particularly when the acceleration of the node is associated with atrial ectopic rhythm, sino-atrial block, atrioventricular block in a retrograde as well as in an anterograde direction, the presence of
anonl-alous A-V conduction, the presence of ventricular ectopic foci, and the various manifestations of concealed conduction.
In patients with rheumatic fever, the presence of the accelerated nodal pace-maker seems to be a highly specific
indica-tion of tile presence of carditis often
preceding other evidence of cardiac in-volvement. In some patients with fever,
ar-thraigia, and positive acute phase reactants, tile accelerated nodal pacemaker strongly suggested the diagnosis of carditis prior to the appearance of the major criteria of rheumatic fever and carditis. In the pa-tients of Group I with rheumatic carditis, A-V block, first or second degree, was
pres-ent only in three cases.
The presence of an accelerated nodal pacemaker was not related to the severity
of the carditis. A typical case of this ar-rhythmia occurring in a patient with acute
rheumatic carditis is demonstrated in a child in Figure 1. In the upper tracings the ventricular rate is 103 and the atrial rate is
120. There is complete A-V dissociation due
to the acceleration of the nodal pacemaker and there is also some degree of A-V block.
In the lower tracing the rate has decreased and sinus arrhythmia is present at an aver-age of approximately 80. The first degree
A-V block is now apparent.
\Ve have divided the patients of Group
II, those in which the arrhythmia is asso-ciated with the presence of digitalis, into those with obvious toxicity, those where the drug has been used in excess, and those in whom an ordinary dosage of digoxin were associated with the accelerated nodal pace-maker. The association of nodal tachycardia with digitalis excess is well-known, and the appearance of this arrhythmia is an
indica-tion for discontinuing the drug. Potassium is always of therapeutic value in these pa-tients whether or not hypokalemia is
pres-ent. Dreifus and co-workers3 have observed
that hypokalemia is not necessary for the
appearance of an accelerated nodal pace-maker with digitalis use, but it does seem to
make it easier for this arrhythmia to
ap-pear.
In infants and children with congenital heart disease, an accelerated nodal
pace-maker occasionally is seen as a
sponta-neously occurring arrhythmia, or after small
or usual doses of digitalis. In these patients,
particularly when congestive heart failure requires it, digitalis need not be stopped
when the accelerated nodal pacemaker is the only manifestation of digitalis action,
although the child should be carefully
watched. Rarely, this nodal arrhythmia is a
long-persisting
(
over 3 years)
one, and we have used digitalis as needed without diffi-culty.The recognition of accelerated nodal
pacemaker during or after open heart surgery#{176} is important because the A-V
dis-sociation which accompanies it is often con-fused with surgically produced heart block. A number of reported cases of surgically
produced block which reverted to normal rhythm 1 or 2 weeks following surgery are actually instances of acceleration of the node to rates above 80, preventing normal sinus conduction. When the nodal rate slows, normal sinus rhythm reappears and the patients “complete heart block” has dis-appeared. It is of some interest that acceler-ation of the node occasionally follows the
atrial septotomy operation for transposition of the great vessels
(
Blalock-Hanlon), but this particular arrhythmia has not been a problem following the balloon septotomy(
Rashkind ). It may be that trauma to the A-V node occurs during the atriotomy,whereas the balloon procedure, involving only the foramen ovale region, spares the
node.
The simultaneous occurrence of A-V 1)loCk and acceleration of the A-V node4’#{176}
(
Fig. 4)
was seen frequently in our cases. This recalls the studies of Hoffman andA
AV
V
42
y2j42
:
,4O460
j
70 60 706
60 70
Ftc. 4. Case :35. Second (legree atrioventricular block Type I vith \\‘enkebach cycles producing 1)Seudo-i)igemini. Tile diagram tinder lead II indicates that, in fact, otll\- one atrial impulse is conducted and this is tile second. The first atrial impulse \Vllicll starts the cycle is blocked, not b depressed atrioven-tricular conduction but b interference pro(ltlce(l by’ the no(lal escape. Tile third atrial iillpulse is not conducted because of the block and leads to a “dropped” beat. This pattern has also been called ‘reversed bigemini.” It is an atteml)t at 3:2 conduction ratio, but in tiliS case the node is accelerated (rate of 86
ptr minute ) and, therefore, escapes preventing tile formation of tile tpical Wenkehach patterti.
l)OrtiOfl of tile atrioventiicii iar julictiollal
tissue. The acceleration may be due to an
injury or disturbance of the lowest
(
yen-tricular
)
1)ortion. The transient nodaltachv-cardia seen during cardiac catheterization
is a less COIllulOfl occurrence than
altera-tions ill A-V conduction and is most likely
due to traullia to the lower A-V junctional
tissue.
The importance of electrolyte
distur-bances on the nodal rate in these children
is difficult to evaluate. In a recent review
Surawicz1#{176} noted that all increase in
extra-cellular potassium decreases the velocity of
diastolic depolarization, which in turn de-pressed automaticity, but also decreases the threshold potential, which counteracts the
foregoing action. If this threshold
poten-tial decrease predominates, acceleration of
the node results. This may be an
explana-tion of the non-paroxysmal nodal
tachycar-dias r0dluce(l 1))’ Fisch and co-vorkers
using rapid injectioll of I)otassiulli Ill clogs.
Of interest in this regard is our Case 40, a
4-year-old boy w-ith uremia and a low
serum potassiuni level. Soon after
ptas-5iU1fl was started intravenously. an
electro-cardiographic pattern of Ilvperkalemia
ap-peared. The QRS complexes were wide,
and there was a short QT interval and
rather tall T waves. There were no P
waves. A nodal tachycardia with a rate of
128 per minute was present.
Although an accelerated nodal i;tce-maker has diagnostic and physiologic
im-portance, it should be reassuring for pedia-tricians and surgeons to recognize it, since it lasts only a few days and has none of the
threatening aspects of arrhythmias, for
which it is sometimes mistaken.
SUMMARY
The nodal pacemaker can be accelerated
WHAT CHILDREN IN 1844 READ ABOUT THEIR LIFE EXPECTANCY IN A WIDELY USED SCHOOLBOOK OF THAT PERIOD
cardiac surgery, and by other clinical
events.
This llodal tachycardia usually appears
as 50lflC form of A-V dissociation with a
ventricular rate faster than 80 per minute.
This accelerated nodal escape rate makes these arrhythmias easy to differentiate from complete heart block in which the nodal
rate is usually 32 to 60 per minute. In 9 of 15 patients with acute rheumatic fever and this arrhythmia, the accelerated nodal pacemaker preceded any other
clini-cal sign of carditis.
REFERENCES
1. Pick, A., and Dominguez, P.: Non-paroxysmal
A-V nodai tachycardia. Circulation, 16:1022,
1957.
2. Castellanos, A., Jr., and Lemberg, L. : The re-lationship between digitalis and A-V nodal
tachycardia with block. Amer. heart J.,
66:605, 1963.
3. Dreifus, L. S., Katz, M., Watanabe, Y., and
Likoff, W. : Clinical significance of disorders of inl)ulse formation and conduction in tile
atrioventricular junction. Amer. J. Cardiol.,
11:384, 1963.
1. Fisclt, C., Feigeni)aum, 11., and Bowers, J. A.:
Non-paroxysmal A-V nodal tachycardia (Inc
to PotassiUm. Amer. J. Cardiol., 14:357,
1964.
5. Miller, R. A., and Rodriguez-Coronel, A. :
Con-genital atrioventricular block. In Moss, A.,
and Adams, F., ed. : Heart Disease in
In-fants, Children and Adolescents. Baltimore:
Williams and Wilkins Company, pp.
1039-1071, 1968.
6. Rabbino, M. D., Dreifus, L. S., and Likoff,
w.
: Cardiac arrhythmias followingintracar-diac surgery. Amer. J. Cardiol., 7:681, 1961.
7. Hoffman, B. F., Paes De Carvaiho, B. S.,
Mello, W. C., and Cranefleld, P. F. :
Eiectri-cal activity of single fibers of the
atrioven-tricular node. Circ. Res., 7: 11, 1959.
8. Paes De Carvaiho, A., and De Almeida, D. F.:
Spread of activity through the
atrioventricu-lar node. Circ. Res., 8:801, 1960.
9. Pick, A., Langendorf, R., and Katz, L. N. : A-V
nodal tachycardia with block. Circulation,
24:12, 1961.
10. Surawicz, B.: Role of electrolytes in etiology
and management of cardiac arrhythmias,
Part II. Progr. Cardiov. l)is., 8:364, 1966.
In Mrs. Jane Taylor’s popular, small,
paper-back schoolbook entitled, Physiology frr
Chil-dren, the length of life in the 1800’s was given
as follows:
Do most people live to be old? No, one half die
before tiley are eight years old. Only one out of
three lives to fourteen, and but one in four lives to
see twenty-one.1
NOTED BY T.E.C., JR., M.D.
REFERENCE
1. Taylor, J.: Physiology for Children. New York:
