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.