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IDIOPATHIC LONG QT SYNDROME : THORACIC SYMPATHECTOMY
Stori Jr, WS1, Coelho, MS2
1. Wilson de Souza Stori Junior
Hospital Universitário Cajurú’s assistant doctor of the Thoracic Surgery Service and Respiratory Endoscopy. Thoracic surgery residence preceptor at Hospital Universitário Cajurú (PUC-PR). (PUC-PR’s Cajuru University Hospital).

2. Marlos de Souza Coelho
Headmaster of the thoracic surgery and respiratory endoscopy service of Hospital Universitário Cajurú of Pontifícia Universidade Católica do Paraná. (Cajuru University Hospital of Parana’s Pontificia Catholic University).


INTRODUCTION
Long QT Syndrome (LQTS) is a rare disease that has been progressively interesting a great number of researchers due to its peculiar aspects. One of these aspects is the dramatic manifestation of this disease, with syncope episodes that lead many times to cardiac arrest and sudden death when the patient is under physical or emotional distress conditions. Most of these cases occur with pediatric patients (1,2). Another aspect is that behind an infrequent disease there could be the key to the comprehension of mechanisms through which the anatomic function modulation can increase or prevent arrhythmia, a danger condition to the patient.

LQTS can be classified as idiopathic (congenital) and acquired. The idiopathic form is a congenital alteration that may be associated with sensoryneural deafness (Jervell and Lange Nielsen Syndrome, recessive autossomic) or with people with healthy audition (Roman-Ward Syndrome, dominant autossomic) (2,3). The non congenital form in people with normal audition is called sporadic form.

The acquired form has long QT interval induced by use of several drugs (quinidine, procainamide, amiodarone, fenotiazines, tricyclic antidepressives and other), metabolic disturbs (hypokalemia, hypomagnesemia), nutrition disturbs (anorexia, liquid diet), central nervous system (2, 3), severe bradycardia, mitral valve prolapse and cardiac ganglionitis(2).

Choice treatment for patients with idiopathic LQTS concerns the administration of B-blockers. This therapy form has success in 75-80% of the patients(1,4). For patients that despite of maximum dose use of B-blockers remain presenting syncope or cardiac arrest, left thoracic sympathectomy can be of great help(1,5).

Other kinds of treatment to this syndrome include specific therapy to genetic alteration (1,2,5,6), pacemarker and automatic defibrillator implant (1,2,5).
 
CLINICAL PRESENTATION 1. ELECTROCARDIOGRAM AND ECHOCARDIOGRAM
The maximum amount of time for the corrected QT interval (cQT) normal length is 0,44 seconds. However, recent data suggest that the normal cQT can be longer; 0,46 for men and 0,47 for women, with regular variation of +-15% of the average value.

The ventricular arrhythmia development that threats the life of the idiopathic LQTS patient, is most likely to be related to the cQT interval length (malign arritmies are more frequent in patients with cQT interval length bigger than 0,66 seconds)(1,2).

Polymorphic tachycardia with long QT interval are called “Torsade de Pointes”. In LQTS, recurrent syncopes and sudden death are secondary to ventricular tachycardia, that is frequently caused by “Torsade de Pointes”.(2,3).
 
ELECTROCARDIOGRAM CHARACTERISTICS
QT interval: cQT bigger than 0,46 seconds. The cQT interval between 0,41 and 0,45 seconds can be considered normal (7); b. QT interval dispersion: abnormal pattern of ventricular repolarization (1); c. T wave: polarity or amplitude T wave alteration can exist in resting for brief moments, but frequently appear during the physical or emotional tension and can precede “Torsade de Pointes”. The T wave can be biphasic, biphid or carved. When it is carved, it is suggestive of different repolarization times in different ventricular areas (1); d. U wave: appears preeminently in some patients. There can be an even greater sinusal bradycardia increase or it can be alternating after pauses. Accentuated expansion of the QT interval may be a very preeminent U wave (7); e. Sinusal pause: several patients with LQTS may present sudden pauses that exceed 1,2 seconds in the sinusal rhythm. These pauses are not preceded by cardiac frequency alteration. They can be important in the arrhythmias beginning in patients with LQTS and frequently precede the “Torsade de Pontes” beginning (1); f. Cardiac frequency: individuals with LQTS frequently present bradycardia during resting and during exercises. (1,7).
 
ECHOCARDIOGRAM CHARACTERISTICS
Echocardiogram alterations can be found in some individuals with LQTS. These abnormalities include two aspects:

a) increase in the thickness degree in the initial contraction phase; b) slow movement presence in the late thickness and Plato morphology phase, sometimes, this is joined by a second peak.

This was the first evidence of a cardiac abnormality associated with high syncope or cardiac arrest risk in LQTS (1). 2.
 
CLINICAL CHARACTERISTICS
In a young individual with long QT interval detected by electrocardiogram, the typical presentation of LQTS is syncope or premature cardiac arrest by adrenenergic stimulation (physical or emotional tension, or auditive stimulus). But, the clinical presentation of this condition is not always so clear and sometimes diagnosis becomes difficult (1,2,8,9). Some of these patients can be wrongly diagnosed as epilepsy carriers(2,8,9).

Moss and cols. (1991) made a prospective study on 328 families with affected individuals. The ones who had long QT interval and high cardiac frequency had a bigger syncope or cardiac arrestment risk than the ones with normal QT interval and those with low cardiac frequency. Syncope was associated to physical and emotional tension or to auditive stimulus (for instance, the ringing of an alarm clock). When compared to male patients, female patients presented a discrete increase in the risk of developing cardiac symptoms (8).

Any patient that has ever presented syncope or cardiac arrestment episodes has great risk of presenting new episodes, including sudden death (1,2,7,8). This is true fact at any age, but during adolescence has special importance because in this phase, the mortality probably is bigger (7, 8).

Asymptomatic individuals with long cQT interval on electrocardiogram that never presented syncope, have cardiac symptomatology low risk in the future. The syncope incidence in this group is approximately of 0,5% per year, and rarely the first episode is fatal. These generalizations are valid to asymptomatic individuals with cQT interval expansion identified during the familiar evaluation of symptomatic LQTS people or when the cQT interval expansion is unexpected during a routine exam.

There is a small number of LQTS families that have several sudden death episodes in young individuals in different generations. Families with high risk to develop such episodes can be related to congenital deafness (Jervell and Lange-Nielsen Syndrome) or to very long cQT interval with bizarre configuration of the T wave.

Patients with idiopathic LQTS that have greater sudden death risk include those with family members that suddenly died when young and those with previous syncope episode.

Recently, sindactily was described as a congenital form in some patients (2).

In a comparative study between patients treated with antiadrenergic therapy (-blockers and sympathectomy) and the ones that were not getting treatment or treated with non antiadrenergic therapy. The mortality in three years after the first syncope was of 6% in the antiadrenergic treated patients group and of 26% in the group of patients treated with other treatments of not treated at all. Fifteen years after the first syncope, mortality among treated patients was of 9% and of 53% in the other group of patients (1, 10, 11).
 
3. GENETIC ALTERATIONS
The hypothesis that idiopathic LQTS results of left sympathetic tonus preponderance was altered by genetic information obtained in different families with this syndrome. The genes associated to this syndrome are located in chromosomes 11 (LQT1 – LQTS associated to chromosome 11), in chromosome 7 (LQT2 – LQTS associated to chromosome 7) and in chromosome 3 (LQT3 – LQTS associated to chromosome 3). The gene for LQT1 is called KVLQT1 and seems to be connected to the K+ channels. The gene for LQT2 received the name of HERG and is also connected to the potassium canals. The gene for LQT3 was called SCN5A and is a gene linked to heart’s Na+ channels (1).

The three different mutations seem to produce distinguished alteration on electrocardiogram. Different T wave forms are in patients with LQT1, LQT2 and LQT3. There are attempts of correlating the several mutations and clinical responses to the different interventions, however, the results must be observed with proper care due to the small number of studied individuals.

The sodium canal blocker produces reduction of QT interval in patients with LQT3; the same did not happen in patients with LQT2 and LQT1. The cardiac frequency increase reduces the QT interval in patients with LQT3, this effect was less evident in patients with LQT2 and LQT1(1). Because of this, probably patients with LQT3 have less risk of presenting syncope during physical exercise. These patients may be the ones who are less protected with -blockers, which would decrease the frequency and would prevent its increase during exercise. It has been possible to observe also the association between physical or emotional tension and syncope in patients with LQT2. Patients with LQT3 seem to be more propense to risk during rest or sleep (1, 6).

Abnormalities in chromosome 3 are related with bigger cQT interval length and delay in the T wave beginning, while alteration in chromosome 7 results in low amplitude T wave. It is this way probably that intrinsic alteration in cardiac repolarization increases premature post-depolarization which expands the QT interval and produces “Torsade de Pointes” (1, 2).
 
TREATMENT
Most of the arrhythmia episodes that put the patient life in risk happen due to a sudden increase of the sympathetic activity, frequently mediated by left sympathetic cardiac nerves. And as expected, adrenergic therapy supplies the greatest protection degree to these patients (1). Table 1.
 
TABLE 1: LQTS(1) PATIENT MANAGEMENT
a. Choice treatment: b-blockers (propanolol or nadolol);
b. If the b-blocker treatment fails or is contra-indicated: left thoracic sympathectomy;
c. Bradycardia evidence or pauses that induce malign arrhythmias: pacemarker + b-blocker
d. If the three treatments above fail (b-blockers + sympathectomy + pacemarker):

1. Automatic cardiac defibrillator implant;
2. Attempt of treatment with blockers of the calcium entrance, pentiosmides or a-blockers;
3. In exceptional cases (high cardiac frequency and syncope although b-blockers and left thoracic sympathectomy), right thoracic sympathectomy should be considered.
 
A. ANTIADRENERGETIC THERAPY
A study made in 1985 by Schwartz and Locati which included 233 patients with symptoms and detailed clinical information of the first syncope episode time, showed great improvement in the patients survival, which were submitted to antiadrenergic therapy (pharmacologic and surgical) when compared to patients that received other kind of treatment or that did not receive treatment at all. Mortality 15 years after the first syncope was of 9% in the group that received antiadrenergic treatment (b-blockers, sympathectomy or both) and of 53% in the group of people that did not receive any kind of treatment and of people that received non b-blockers kinds of treatment (10).
 
A. 1 b-BLOCKERS
This is the major form of treatment to symptomatic patients with syncope or cardiac arrest history and for some asymptomatic patients with LQTS that are members of high risk families (1,2,4,5,9,11). Propanolol keeps being the drug frequently more used and its diary dose varies from 2-3mg/kg. This drug has the disadvantage of needing multiple diary management and is contra-indicated to patients with asthma. Another drug that is often used is nadolol. This has a longer average life than propanolol and can be managed only twice a day (1). b-blockers are effective, specially when mutation involve genes linked to K+ (potassium) channels (LQT1 and LQT2)(1). Its efficiency is not so clear in patients with SCN5A mutation, which is linked to the Na+ (sodium) channel (LQT3)(1,5,6).

The b-blocker dose must be maximum to assure the proper competitive block of the b-adrenergic receptors in the myocardium. Several patients have subjacent sinusal bradycardia, and if the b-blocker treatment produces deep bradycardia or significant sinusal pauses that take more than two seconds, the concomitant use of pacemarker is indicated(1,5).
 
A.2 THORACIC SYMPATHECTOMY
This procedure is indicated basically for patients that present refractory symptoms (syncope and cardiac arrest episodes) to the b-blocker treatment or that have contra-indication to b-blocker use (1,2,4,8,9,10,11).

There are reports of several cardiac denervation forms. The left stellectomy consists on the left stellate-ganglion ablation. This ganglion is formed by the fusion of the eighth cervical ganglion with the first thoracic ganglion. This procedure produces Horner Syndrome and only one limited cardiac denervation (1,4).

The left cervicalthoracic sympathectomy consists on the total left stellectomy and resection of the first four or five thoracic ganglions. This procedure produces adequate sympathetic cardiac denervation , but with associated Horner syndrome (4).

High left thoracic sympathectomy involves the resection of the inferior part of the left stellate-ganglion along with the first four or five thoracic ganglions. This procedure produces adequate cardiac denervation, which is rarely associated to Horner Syndrome. It is useful to remind that Horner Syndrome results from the interruption of the nervous fibers directed to the ocular region that cross the superior part of the stellate-ganglion. These ocular fibers are spared with high thoracic sympathectomy and Horner Syndrome is avoided or minimized (4).

Schwartz and cols. (1991) studied in 85 patients the three cardiac denervation techniques described above. Ten patients were submitted only to left stellectomy and four of these patients were taken to an even longer second surgery, to resect the third and fourth thoracic ganglions because these still presented important symptoms. The left cervicalthoracic sympathectomy was performed in 29 patients, and the high left thoracic sympathectomy was performed in 41 patients. The extrapleural supraclavicular access was the more frequently used. There were no major complications or deaths during the surgery. In few patients, ventricular tachyarrhythmias and long periods of assistoly occurred during the procedure. A patient presented ventricular fibrillation just after the anesthesial induction, but it regressed with cardioversion and this did not interfere on the surgery’s accomplishment. A port-operatory death occurred and two patients presented chronic hyperemia of the left eye. Right after the surgery, Horner’s Syndrome was present in most of the patients, but almost every time it decreased or disappeared later (4). Other clinical characteristics of LQTS patients before and after sympathectomy are on the following table:
 
Table 2: pre and post-operatory clinical characteristics of patients with LQTS (Schwartz and cols., 1991)(4):
 
Ouriel and Moss (1995) studied 10 patients that were submitted to high left thoracic sympathectomy, in which through a supraclavicular access, two inferior thirds of the stellate ganglion and three or four first thoracic ganglions were dried out. No patient presentet intra-operatory cardiac arrhythmia. Horner Syndrome was detected in 90% of the patients, but none complained of incapability due to the syndrome, and 90% remained completely free of symptoms during the post operatory observation, which lasted approximately 1,3 years. A patient suddenly died 10 months after the surgery. The frequency of ventricular arrhythmias decreased 92% and the frequency of syncope episode decreased 98%. Epstein and cols. (1996) studied left posterior thoracic sympathectomy. The sympathetic chain is achieved through a posterior paravertebral thoracic access followed by resection of the posterior portion of the second and third ribs and by the transversal process of the second and third thoracic vertebras. With a needle connected to a coaxial bipolar stimulator and with the monitorized patient, alterations on electrocardiogram and blood pressure were checked during the stimulation of the second to fourth thoracic ganglion. After the demonstration of QT interval expansion, U or T wave alteration, ventricular arrhythmias, cardiac frequency increase or blood pressure elevation, the sympathetic chain was dried out in the local or right above the level in which occurred most apparent response to the stimulus. In all patients, with exception of one, the resection involved the second, the third and the fourth thoracic ganglions. In a patient, the resection involved the sympathetic chain above the third thoracic ganglion and the sympathetic chain between the third and fourth thoracic ganglion. No Horner Syndrome occurred and the results were satisfactory in all patients (12). Although the tension of the anaesthesical and surgical procedure can lead to ventricular fibrillation in patients with idiopathic LQTS, only in 1997, Nagakura and cols. reported the first case in english literature of an individual with age superior to 20 years that died after its submission to surgery. It was a 50 years old female patient, holder of Jervel and Lange-Nielsen Syndrome, and which was submitted to surgery to ressect a congenital coledocal cyst. The surgery was performed under general anesthesia and eleven hours after, the patient suddenly died by ventricular fibrillation (13).
 
A. 2.1. THORACIC SYMPATHECTOMY THROUGH VÍDEO ASSISTED THORACIC SURGERY
Advance in technique and materials of videothoracoscopy surgery lead to an important reducing of morbidity and mortality, and nowadays thoracic surgery video assisted became an effective and safe procedure. Thoracic sympathectomy through videothoracoscopy generally is avoided by patients previously submitted to thoracic surgery or with pulmonary infections because they have dense adherences, what can avoid the proper visualization of the sympathetic chain.

This procedure is performed under general anesthesia, with the use of orotracheal intubation cannula of double lumem, and the patient is sustained in lateral decubit (14).

Surgery –
1. The optics is introduced through a small incision in the fifth intercostals space over the median axilary line to permit better visualization of the superior thoracic cavity. Other two incisions are made under visualization: one in the fifth intercostal space, next to the inferior angle of the scapula or over the posterior axilary line and other in the third intercostal space, over the anterior axilary line.

2. The lung must be released of all its adherence with the use of cauterization, so it can be completely collapsed. The pleura can become opaque, what can detain the visualization of the sympathetic chain. This kind of alteration frequently occurs in the elderly.

3. With the collapsed lung, the sympathetic chain can be viewed. The first till the fourth ribs and the correspondent vertebral bodies are identified. The sympathetic chain is located next to the vertebral bodies, crossing the posterior heads of the ribs.

4. The superior portion of the sympathetic chain and all the dissection extension must be identified.

5. The disection begins with a pleural incision, the pleura covers the sympathetic chain at level of the fourth thoracic ganglion, right below the fourth rib.

6. The parietal pleura must be opened until the inferior part of the stellate ganglion, right above de second rib.

7. Through delicate maneuvers, the sympathetic chain is immobilized from its bed. The communicant branches of the sympathetic ganglions of T2 and T4 are cut without the use of cauterization or clips to avoid lesions in the adjacent intercostals structures.

8. The ganglions and its communicant branches must be carefully dissected and spread of the intercostals vases to avoid bleeding.

9. The dissection is done in superior direction until the inferior portion of the stellate ganglion and until the identification of the Kuntz nerve. This, which is the great T1 branch and that runs laterally to the sympathetic chain tree, at level of the inferior portion of the stellate ganglion. The Kuntz nerve helps on the T1 identification, inferior part of the stellate ganglion.

10. The sympathetic chain is sectioned at level of the inferior third of the stellate ganglion (T1), together with any branch that courses taking to the caudal region or in lateral direction (14). The T1 ganglion must be carefully dissectated and any fiber that courses in superior direction must be sustained.

11. The stellate ganglion and any branch that courses in superior direction must be preserved without any damage. Lesion or traction of the stellate ganglion’s superior portion should be avoided in order to minimize the Horner’s Syndrome risk of development (1,12,14,15).

12. The authors do not hold a clear position about the best inferior level for cardiac denervation. Few indicate to sectionate the sympathetic chain right below the third ganglion (1,4,11). Most of them advise the section below the fourth(1,4,11,12,15) or fifth thoracic ganglion(1,4,11,15,16).

13. Revise the sympathetic chain’s resection bed in case of a possible bleeding; input of a thoracic drainage devise under water seal, this will be sustained for approximately 24 hours (or until the lung expansion)(14). There are some simplification attempts of the video assisted thoracic surgery. Woing and cols. (1996) performed a cauterization of the sympathetic chain through videothoracoscopy in a patient that presented herself as refractory to the b-blockers treatment and to other kinds of therapy. A cauterization was performed in the inferior half of the left stellate ganglion, this procedure was also performed in the second, third and fourth thoracic ganglions of the same side. The patient presented Horner’s Syndrome at left and left hand anidrosis. The QT interval was smaller in the post surgery electrocardiogram. Two months after the surgery, the patient had a new syncope episode and the whole procedure was redone just like on the first surgery.

The patient continued asymptomatic during the 10 month control(17). We contra indicated the T1 cauterization because the nerve is a good heat and electricity conductor what might lead to C8 lesion, with consequent Caulde-Bernard-Horner’s Syndrome. It must be dissected and dried up with endoscopic scissors.
 
B. SPECIFIC GENETIC THERAPY
Via oral treatment with mexiletine (Na+ channel blocker), reduces the QT interval and regularizes the T wave morphology in LQT3. The same does not occurs in patients with LQT2 and LQT1. K+ infusion associated to spironolactone corrects abnormalities in the repolarization’s period and in the T wave morphology in LQT2. There still are not available information whether the specific genetic therapy in long term is safe or if it prevents arrhythmias(1,5).
 
C. PACEMARKER
Pacemarker is indicated in idiopathic LQTS patients when they present atrial-ventricular blocking and whenever there is evidence of malign arrhythmias pause dependents(1). The combination of therapy with b-blocker and cardiac pacemarker seems to be very effective in the prevention of recurrent arrhythmias that put the LQTS patients’ life in danger. The pacemaker’s good effect in high risk patients is related to bradycardia and pauses prevention, factors that induce arrhythmia in this syndrome (5).
 
D. AUTOMATIC CARDIAC DEFIBRILLATOR
Automatic cardiac transvenous defibrillators are indicated only when the patient remains symptomatic despite the use of b-blockers in maximum dose and of having being submitted to thoracic sympathectomy (1,5).
 
E. CARDIAC TRANSPLANT
Klein and cols. (1996) performed a heart implant in a child with idiopathic long QT syndrome that developed dilated miocardiopathy induced by high frequency produced by the pacemarker. The only effective drug after the birth was isoproterenol and on the third day of life, a pacemarker was implanted that only with a frequency superior to 110 beats per minute was able to inhibit the arrhythmias. At the age of 12, the child developed dilated miocardiopathy and was submitted to cardiac transplant. Under control for 5 years, it has been using only imunosupressor drugs and remains asymptomatic (18).
 
CONCLUSION
Treatment must be always started with b-blockers management, unless there is contra-indication. If the patient remains presenting syncope, despite the use of b-blockers in maximum dose, thoracic sympathectomy must be performed. Nowadays, the preferred access has been the video assisted thoracic surgery. This technique offers less morbidity, besides being a safe procedure of relative facility in its execution that gives good results. In specific cases, it is indicated the use of cardiac pacemarker. In 3-4% of the patients, refractory symptomatology to the antiadrenergic treatment (b-blockers and thoracic sympathectomy) can occur, with the possibility of pacemarker use(1).

Even that a complete protection against arrhythmia hasn’t been accomplished yet, great progress has been made, and the prognosis for patients with this syndrome has radically changed.
 
BIBLIOGRAPHIC REFERENCES
1. Schwartz PJ. The long QT syndrome. Curr Probl Cardiol 1997;22:299-351.

2. Zipes DP. Specific arrhythmias: diagnosis and treatment. In Braunwald E ed. Heart Disease. 5th ed. vol 1. Philadelphia-Toronto, W.B. Saunders Company 1997;685-86.

3. Vlay SC. Ventricular arrhythmias. In Vlay SC ed. A pratical approach to cardiac arrhythmias. 2nd ed. New York, Copyright 1995;148-83.

4. Schwartz PJ, Locati EH, Moss AJ et al. Left cardiac sympathetic denervation in the therapy of congenital long QT syndrome: a worldwide report. Circulation 1991;84:503-511.

5. Moss AJ. Clinical management of patients with the long QT syndrome: drugs, devices, and gene-specific therapy. PACE 1997;20:2058-60.

6. Schwartz PJ, Priori SG, Locati EH et al. Long QT syndrome patients with mutations of the SCN5A and HERG genes have differential responses to Na+ channel blockade and to increases in heart rate: implications for gene-specific therapy. Circulation 1995;92:3381-86.

7. Marriott HJL, Conover MB. Polymorphic ventricular tachycardia. In Marriott HJL, Conover MB eds. Advanced concepts in arrhythmias. 3rd ed. St Louis-Toronto, Copyright 1998;293-310.

8. Moss AJ, Schwartz PJ, Crampton RS et al. The long QT syndrome: prospective longitudinal study of 328 families. Circulation 1991;84:1136-44.

9. Moss AJ, Robinson J. Clinical features of the idiopathic long QT syndrome. Circulation 1992;85[suppl I]:I-140-I-144.

10. Schwartz PJ, Locati EH. The idiopathic long QT syndrome: pathogenetic mechanisms and therapy. Eur Heart J 1985;6[suppl D]:103-14.

11. Ouriel K, Moss AJ. Long QT syndrome: an indication for cervicothoracic sympathectomy. Cardiov Surg 1995;3:475-78.

12. Epstein AE, Rosner MJ, Hageman GR et al. Posterior left thoracic cardiac sympathectomy by surgical division of the sympathetic chain: an alternative approach to treatment of the long QT syndrome. PACE 1996;19:1095-104.

13. Nagakura S, Shirai Y, Yamai K, Hatakeyama K. Sudden perioperative death in an adult with undiagnosed Jervell and Lange-Nielsen syndrome. Surgery 1997;122:645-6.

14. Ahn SS, Ro KM. Thoracoscopic Sympathectomy. Ann Vasc Surg 1998;12:509-14.

15. Cheng TO. Left cardiac sympathetic denervation for long QT syndrome. Int J Cardiol 1997;62:281.

16. Chen L, Qin YW, Zheng CZ. Left cervicothoracic sympathetic ganglionectomy with thoracoscope for the treatment of idiopathic long QT syndrome. Int J Cardiol 1997;61:1-3.

17. Wong CW, Wang CH, Wen MS, Yeh SJ, Wu D. Effective therapy with transthoracic video-assisted endoscopic coagulation of the left stellate ganglion and upper sympathetic trunk in congenital long QT syndrome. Am Heart J 1996;132:1060-3.

18. Klein HO, Levi A, Kaplinsky E, Segni ED, David D. Congenital long QT syndrome: Deleterious effect of long-term high-rate ventricular pacing and definitive treatment by cardiac transplantation. Am Heart J 1996;132:1079-81.
 
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