Download Pediatric pre-excitation: Say “no” to drags?

Editorial
MARK
Comment
H. SCHOENFELD.
MD. FACC
Sixty years have passed since the first drxrlprmn zf the
Wolff-Parkinson-White syndrome (I). Durmg this time rig
nilicant strides have been made bmh m elucidating the
electrophyrmlogic basis for tschyarrhylhmia: obscrbed m
this syndrome and in defining therapeutic ~itrategi:\ for
tiicted
patients (2). particulxly
adolescents and older
adults. For the pediatric patient with evidence ci preexcitation, however. both the optimal managsmeni and the
ultimate prognosis remain unclear.
To treat or not
As whh any
hythmic dwrder.
two conditions dictate the need for specific treatment of the
patient with Wolff-Parkinson-White syndwme: the presence
bf refractory symptoms or art inordinately high risk of
sodden cardiac death, or both. (For the pediatric patient the
potential impact of the pre-excitation syndrome oo the
chilii’s development may also be a factor.! In the youngcrt of
patients an accurate assessment of symptoms is highly
aroblematic. Certainlv the sickest infants will uruallv be
seen with heart failure (3.4) but the tree incidence of less
severe epiwdes of tachycardia is difficult to gauge. Soalled
natural history studies suggest tm overall benign prognosis
for pre-excitation syndromes detected in infancy. although
in the majority of rewrted cases the patients were maintained on some form of drug therapy G-5). Therefore.
ore&e determinants of sudden death risk for the umreated
~ttdividual are as yet undefined and benignity in this syndrome continues to he a retrospective diagnosis. On the
other hand, the well intentioned practitioner eager to initiate
totreat.
I
The presrnt hJy.
In th,s tswe of thr Journid Pcr~ and
Garxn 17~ offer a porsible >ohmon to the quandary of
whether wx! when to treat. In oerhaus the lilrwf rwos~cclwe wx\ IO date, they report on the clinical cour~c of 140
paticnl\ wrh rhe Wolff-Parkinson-White syndrome whose
~niudl rachywrdia was diagnosed before age 16 yean. Four
Qerwlcnt &hycardia: 3) 3i QPUC~ISwho experienced recurrenl tach!cardia >6 monlhn after initial prerentauon; and
41 Lh Qatwnrs with neither rewrrence nor pewrtence of
tach!cardia. thm is. total disappeamnce after rhe imtial
rpivlde The rubgroup of 37 paurnts with recurrent tachycnrdra after 6 months was of grear interr&t because the mean
;?gcof recurrence was not influenced by whether or not the
patient srl) being given antiarrhythrmc drugs. In hct. alrhough m rhe majority of infants (excluswe of group I)
tschycardia ceased by age 8 months, one third had II
priun rlv b,zr rrrclrgcrrrdirr-Jwu bucrvnl wpwdlerp of tirr
~~SPIII’P w rrhswre of dnr,e !lwrrrp? wit,, arrhylhmia recurrence iii .L mean age of S years Furthermore. age at
recurrence was not influenced by the presence or absenceof
concormtant rtructural heart disease. accessory w~,t location or the persistence of the pre-excitatton pattern on the
electrocardiogram (ECG). Only two deaths were observed.
neilher atwbuted to tachyarrhythmia.
Perry and Carson (7) propose rhat speciric aaiarrhythms
agents may be avoided for extended periods aflel ,:?itial
presentntion in infanls with the WM.Parkinson-White syndrome. iiowevcr. the majority of patients whose tachyardis
IS present after age 5 years warrant ongoing pharmacologic
or surgical therapy becsuse their tachycardia is usually
persistent. The concept of inlermittent drug therapy in vhich
atxiarrhythmic agents are administered only at the onset of
an at rhythmic episode has been advocated hy some (61 as a
mans of successfully treating infrequent symptoma.ic recurrences of tachycardia. This”cocktail” approach obviates
problems asrociatLd with long-term main!enance dru: there
ttpy sod may apply to the early childhood years of the patient
wdh pre-ewtation.
Previous sardfes. These have reported (3-j) a good prog_
nosis asbocmted whh pre-excitation syndromes seen in infants and young children. with eventcsl resolution of symptoms in mat patients. However. because the overwhelming
nujonty of patients have been maintained on drug therapy,
a true assessment of the nalwsl history of the condition is
not pow%
Interestingly. digoxin has been the mamsmy of
treatmtnr dcspire rhe koown potential hazards of ils use in
older pu~er,ts (9). Recurrcoc~; of tachycardia are rare in the
reported series (3-9. In COIIIKI~I,in an early series of iofmtts
wilh paroxysmal tachycardia of all forms. Lundberg (IO)
noted that tachycardia recurrence in later childhood was
substantial (46%) in those initially seen with a pre-excitation
ECG pattern. In a more recent series Deal et al. (II) also
noted an appreciable recurrence rate in patients >I year old
(33%). Tachycardia was significantly more likely to recur in
patients with a Rose~baum type B pattern of pre-excitation
and in petients who required more than one drug to maintain
sinus rhythm when initially seen. The last two studies (IO, I I)
corroborate the findings of Perry and Garson (7). namely.
that recurrent tachycardia m later childhood is not uncommon for the infant with pre-excitation. Previously unreported. however. were the timing of such recurrences and
the observation that such timing is uniquely independent of
the presence or absence of concomitant drug therapy (7).
Possible explanations for the recurrence-free interval. One
of the continuing frustrations for the electmphysiologist is
the inability to predict the timing of both the initial and the
subsequent episodes of an arrhythmic disorder. For example, in patients with clinically stable coronary artery disease
and prior myocardial infarction, the long-term reproducibility of responses TV prognlmmed cardiac stimulation is great
and hence the arrhythmic substrate is relatively constant
(12). Despite this observation. it remains impossible to
predict if and when a patient will spontaneously experience
recurrent ventricular tachycardia. In the case of the WolffParkinson-White syndmme, the long-term constancy of the
electrical milieu is less clear. In fact, many older asymptomatic patienls lose the capacity for anterograde conduction
over their accessory pathways when studied longitudinally
in the electrophysiology
laboratory (13). Loss of preexcitation has also been observed in infants (4,5,lO,l I) and
the phenomenon ofintermittent pre-excitation. thought to be
associated with a good prognosis, has long been appreciated
(14-16).
Anatomic factors, such as postnatal resorption of accessory atriovcntricular connections (17) or the development of
fibrosis demonstrated pathologically (18). may be related to
the loss of pre-excitatmn; this would not. however, explain
the observation that the most dangerous pre-excited arrhythmias are often associated with the smallest pathologically
demonstrated bypass tracts (Bhara!i S, personal communication, June 1990). The primacy of cholinergic innervation
during early cardiac development (17) and the enhancement
of ventricular prc-excitation with increased isgal tone
0,14,15) may explain the loss lfthc pre-excitation pattern in
many infants and the low atrhythmic mortality generally
attributed to rapid pre-excited atrial fibrillation (19). However, none of the aforementioned serve to explain the
disappearance and subsequent reemergence of orthodromic
tachycardia many years later independent ofthe presence or
absence of the pre-excitation pattern (7.1 I).
Limitations of the pres-nt study. The report by Perry and
Garson (7) is a retrospective analysis of a large se+es of
patients studied over a long period during which the avail-
ability of eleclrophysiologic techniques and newer antiarrhythmic agents was not uniform and, hence, a systematic
method for determining the need for and selection of therapy
was not employed for the population as a whale. Furthermore, tke method of follow-up was not standardized and
asymptomatic recurrent tachycardias may thus have been
missed. The potential impact of amiarrhythmic drugs on
decreasingthe likelihood of arrhythmia recurrence cannot be
ignored in the group 4 patients without recurrent tachycardia
because most received drug therapy: it is also not clear
whether this last group was preselected on the basis of other
factors that may have favorably influenced outcotne.
Pre.excitalion pattern versus syndrome. If it is not clear
how long, if at all. we can forestall treatment in the onetim:
symptomatic patient with a pre-excitation syndrome. it IE
even less apparent bow to counsel the asymptomatic child
with an ECG pattern of pre-excitation alone. Electrophvsiologic variables. such as anterograde bypass tract refractory
periods and shortest pre-excited RR intervals during atrial
fibrillation. may serve to stratify risk in the adult (18) but
these variables have not been examined in the child. The
clinical and electraphysiologic detemdnams of outwme in
thL young patient with pre-excitation require urgent prospeclive dclinition. The success of the pediatrician in dealing
with the question of whether to treat will later enable the
adult cardiologist to wrestle with the same dilemma in the
postadolescent patient he or she inherits.