Discussion:
Long QT syndrome can be congenital or acquired. Congenital long QT
syndrome is associated with refractory ventricular arrhythmias, Torsade
de pointes, ventricular fibrillation and even sudden cardiac death.
Among the various options available to prevent sudden cardiac death,
beta-blocker therapy is the first-line mainstay
treatment3. However, not all patients respond to this
treatment and responders still carry risk of sudden cardiac death4. In those patients who are intolerable or
refractory, other options include LCSD), permanent pacemaker insertion
and Implantable Cardioverter Defibrillator (ICD) implantation5.
Although every management is associated with its own risks and benefits,
currently ICD implantation is widely accepted as an adjuvant to
beta-blocker therapy. However, ICD implantation is suitable mainly in
high-risk adult patients. ICD implantation in pre pubertal, young and
active patients is associated with device malfunction (inappropriate
shocks), infection and psychological problems 6.
Furthermore, it necessitates life-long and routine device replacement in
young patients. The efficiency of ICD is further limited to its
ineffectiveness in terminating tachyarrhythmias of polymorphic
ventricular tachycardia (VT), bidirectional VT, and electrical storm7. Availability of appropriate size AICD is another
concern in pediatric patients. Frequent shocks can initiate
hyperadrenergic storm, and can lead on to VT storm. Many episodes of TDP
could be self-terminating, but may be subjected to cardioversion.
The other treatment options in these subsets of patients include LCSD
and pacemaker implantation which have been studied earlier and proved
their efficacy in reducing the number of significant events culminating
in death. Whatever may be the form of treatment, beta-blockers are must
as they prevent the development of torsades by reducing the heart rate,
shortening QT and sympatholysis. Hence, decisions regarding the correct
course of treatment are consequently challenging 8.
LCSD is a well-established procedure with large and multicentric studies
reporting consistent efficacy in reducing cardiac events, albeit it’s an
underutilized technique 8. Its main applications are
in those children with β-blocker intolerance or refractoriness, high
risk of sudden death on β-blockers, frequent ICD shocks, as a bridge to
ICD implantation in infants and small children9,10. In
such patients, asynchronous cardiac sympathetic denervation and
ventricular refractoriness will prevent the occurrence of
torsade’s11. LCSD prevents norepinephrine release in
the heart and raises the threshold for ventricular fibrillation without
impairing myocardial contractility or reducing heart rate12,13. It is especially effective in patients with
poor compliance to β-blockers. Also, reduces the number of shocks in
patients with frequent shocks thereby improving quality of life.
Surgical techniques for LCSD :
Left stellectomy and left cervicothoracic sympathectomy were two
initially described techniques of LCSD. These techniques were associated
with Horner’s syndrome and hence high thoracic left sympathectomy was
introduced. In this lower half of the stellate ganglion and the first
four or five left thoracic sympathetic ganglia are removed. Resection of
the lower half of the stellate ganglion is considered necessary for the
anti-fibrillatory effect 10.
Conventional approaches include left posterolateral thoracotomy,
supraclavicular extra pleural approach. Both the approaches carry same
risks; however, thoracotomy was preferred in our institute as it
resulted in completeness of surgical procedure, access and moreover in
infants, it is preferred technique. We have also placed epicardial
permanent pacemaker in these patients. Recently developed technique was
VATS – LCSD which employs minimally invasive video thoracoscopic
techniques to perform LCSD 14. Even though, various
benefits of VATS-LCSD are established over conventional thoracotomy, its
role in small children and in conjunction with epicardial PPI remains to
be well documented 15.
In the largest series of LCSD in long QT syndrome patients, 46% of
patients were asymptomatic, with cardiac event rate dropped by 91%.
Also observed was reduction in the number of shocks experienced by
95%16. In the recent guidelines, it has been
recommended to perform LCSD as class I and IIa
indication17. Although majority of studies reported
decrease in the number of cardiac events, 20-50% remain symptomatic.
Hence, LCSD should be considered as an event-attenuating procedure, and
should not be viewed as curative or alternative to ICD placement.
Pacemaker therapy has a complementary role, at least theoretically, when
used along with LCSD in children. QTc shortens further on high heart
rate. LGL phenotype is known to have sinus bradycardia,18 and two of our cases had low heart rate. This gets
more pronounced with addition of beta blockers. Last but not the least,
these devices can reliably identify the cardiac rhythm during future
episodes of syncope, if any, and guide further therapy in them. The
importance of pacing therapy is being relooked recently with available
mounting evidence 19,20
Hence, in patients where ICD implantation is not an optimal therapy
possible (reasons provided earlier), epicardial PPI is an effective
alternative. The beneficial effects of pacing in high-risk LQTS patients
probably relate to the prevention of bradycardia, pauses, and the
shortening of long QT intervals -factors that are known to be
arrhythmogenic in this syndrome 3. Permanent cardiac
pacing reduces the rate of recurrent syncopal events in high-risk LQTS
patients, but it does not provide complete protection. It’s called as
anti-bradycardia pacing 21. Permanent pacing may be
efficacious by decreasing the dispersion of refractoriness.
The efficacy of LCSD should be judged only on the development of
symptoms or cardiac events during the follow-up period. Patients with
only syncope and a post-LCSD QTc < 500ms were at a very low
risk of adverse events 11.
In patients with LQTS, episodes of torsade’s de pointes are usually
adrenergic dependent, but spontaneous or beta-blocker-induced
bradycardia may act as a provocative agent for episodes of torsade de
pointes in these patients22. Permanent pacing plays an
obvious role in alleviating bradycardia-related symptoms induced by
beta-blocking drugs. Hence, permanent pacing and beta-blocker therapy
can control these arrhythmias.
In our series, three management strategies were employed to control
arrhythmias and to bridge for ICD implantation later in their life post
pubertal age. All our patients were on β-blocker therapy
pre-operatively, and continued to develop symptoms despite therapy. All
the patients were offered LCSD and additional procedure of epicardial
PPI in high-risk patients (two children) and Implantable Loop recorder
in borderline high-risk patient (one child). Even post-operatively,
β-blocker has to be initiated as early as possible. In our series,
patient two developed ventricular tachycardia and impending arrest in
the immediate post-operative due to late re-introduction of β-blocker,
which reflects its importance. This combination prevents adrenergic
dependent torsade’s, β-blocker therapy reduces heart rate and PPI helps
in preventing bradycardia induced torsades and also pauses. Altogether,
there will be significant decrease in cardiac events till bridge to ICD
implantation if deemed necessary.
All four children are asymptomatic
since hospital discharge with no episodes of syncope or presyncope, or
device-detected ventricular tachyarrhythmia.