Efficacy of left cardiac sympathectomy in the treatment of patients with the long QT syndrome

Cardiac Sympathetic Denervation for the Management of Ventricular Arrhythmias

BACKGROUND

The autonomic nervous system contributes to the pathogenesis of ventricular arrhythmias (VA). Though anti-arrhythmic drug therapy and catheter ablation are the mainstay of management of VAs, success may be limited in patients with more refractory arrhythmias. Sympathetic modulation is increasingly recognized as a valuable adjunct tool for managing VAs in patients with structural heart disease and inherited arrhythmias.

RESULTS

In this review, we explore the role of the sympathetic nervous system and rationale for cardiac sympathetic denervation (CSD) in VAs and provide a disease-focused review of the utility of CSD for patients both with and without structural heart disease.

CONCLUSIONS

We conclude that CSD is a reasonable therapeutic option for patients with VA, both with and without structural heart disease. Though not curative, many studies have demonstrated a significant reduction in the burden of VAs for the majority of patients undergoing the procedure. However, in patients with unilateral CSD and subsequent VA recurrence, complete bilateral CSD may provide long-lasting reprieve from VA.

Updates in Ventricular Tachycardia Ablation

Sudden cardiac death (SCD) due to recurrent ventricular tachycardia is an important clinical sequela in patients with structural heart disease. As a result, ventricular tachycardia (VT) has emerged as a major clinical and public health problem. The mechanism of VT is predominantly mediated by re-entry in the presence of arrhythmogenic substrate (scar), though focal mechanisms are also important. Catheter ablation for VT, when compared to standard medical therapy, has been shown to improve VT-free survival and burden of device therapies. Approaches to VT ablation are dependent on the underlying disease process, broadly classified into idiopathic (no structural heart disease) or structural heart disease (ischemic or non-ischemic heart disease). This update aims to review recent advances made for the treatment of VT ablation, with respect to current clinical trials, peri-procedure risk assessments, pre-procedural cardiac imaging, electro-anatomic mapping and advances in catheter and non-catheter based ablation techniques.

Cardiac sympathetic denervation in patients with nonischemic cardiomyopathy and refractory ventricular arrhythmias: a single-center experience

INTRODUCTION

Cardiac sympathetic denervation (CSD) is an effective therapy for selected patients with drug refractory ventricular arrhythmias (VA). Data about the role of CSD in patients with structural heart disease and VAs are sparse. We herein present our experience of CSD in patients with nonischemic cardiomyopathy and VAs despite prior ablation procedure and/or antiarrhythmic drug (AAD) therapy.

METHODS

A total of ten patients (mean age 61.6 ± 19.6, mean LVEF 29.5 ± 12.1%) with nonischemic dilated cardiomyopathy (NICM) (n = 9) and hypertrophic cardiomyopathy (HCM) (n = 1) underwent CSD (left sided in six and bilateral in four patients) due to refractory VA despite multiple AADs (mean number of AADs was 1.6 ± 0.7) and prior VT ablation (mean number of procedures per patient was 1.5 ± 1.3).

RESULTS

Mean follow-up was 10.1 ± 6.9 months. The median number of VA and ICD shocks decreased significantly from 9.0 and 2.5 episodes 6 months prior to CSD to 0 and 0 episodes within 6 months after CSD (p = 0.012 and p = 0.011). Five patients remained free from sustained VA recurrences. Two patients experienced single ICD shock due to a polymorphic VT (triggered by severe hypokalemia in one patient) and one patient a single shock due to monomorphic VT. One patient had five episodes of slow VT under amiodarone therapy (three of them terminated by antitachycardia pacing) and underwent endo- epicardial re-ablation. Two patients died 1 month after CSD. One of them due to electrical storm and cardiogenic shock and the second one due to refractory cardiogenic shock, without recurrence of VAs though. No major complications of CSD occurred. No patient suffered from Horner syndrome.

CONCLUSION

In this study, CSD was effective for treatment of VAs in patients with structural heart disease refractory to antiarrhythmic drugs and catheter ablation. Further larger studies are required to confirm these findings.

Sympathectomy via a posterior approach after a failed trans-thoracic approach: a case of its use for arrhythmia

OBJECTIVE

Congenital long QT syndrome (LQTS) provides an opportunity for neurosurgical intervention. Medication and implantable cardiac defibrillator (ICD)-refractory patients often require left cardiac sympathetic denervation (LCSD) via anterior video-assisted thoracoscopic surgery (VATS). However, this approach has major pulmonary contraindications and risks, with a common concern in children being their inability to tolerate single-lung ventilation. At Oregon Health & Science University, the authors have developed a posterior approach-extrapleural, minimally invasive, T1-5 LCSD-that minimizes this risk.

METHODS

A 9-year-old girl with LQTS type III presented to the emergency department while experiencing ventricular tachycardia (VT) and ventricular fibrillation (VF) with multiple ICD firings. Medical management failed to resolve the VF/VT. VATS was attempted but could not be safely performed due to respiratory insufficiency. The patient was reintubated for dual-lung ventilation and repositioned prone. Her respiratory insufficiency resolved. Using METRx serial dilating tubes under the microscope, the left T1-5 sympathetic ganglia were sectioned and removed.

RESULTS

Postoperatively, the patient had no episodes of VF/VT, pneumothorax, hemothorax, or Horner syndrome. With mexiletine and propranolol, she has remained largely VF/VT free, with only one VT episode during the 2-year follow-up period.

CONCLUSIONS

Minimally invasive, posterior, extrapleural, T1-5 LCSD is safe and effective for treating congenital LQTS in children, while minimizing the risks associated with VATS.

Cardiac sympathectomy for the management of ventricular arrhythmias refractory to catheter ablation

BACKGROUND

Catheter ablation is now a mainstay of therapy for ventricular arrhythmias (VAs). However, there are scenarios where either physiological or anatomical factors make ablation less likely to be successful.

OBJECTIVE

The purpose of this study was to demonstrate that cardiac sympathetic denervation (CSD) may be an alternate therapy for patients with difficult-to-ablate VAs.

METHODS

We identified all patients referred for CSD at a single center for indications other than long QT syndrome and catecholaminergic polymorphic ventricular tachycardia who had failed catheter ablation. Medical records were reviewed for medical history, procedural details, and follow-up.

RESULTS

Seven cases of CSD were identified in patients who had failed prior catheter ablation or had disease not amenable to ablation. All patients had VAs refractory to antiarrhythmic drugs, with a median arrhythmia burden of 1 episode of sustained VA per month. There were no acute complications of sympathectomy. One of 7 patients (14%) underwent heart transplant. No patient had sustained VA after sympathectomy at a median follow-up of 7 months.

CONCLUSION

Because of anatomical and physiological constraints, many VAs remain refractory to catheter ablation and remain a significant challenge for the electrophysiologist. While CSD has been described as a therapy for long QT syndrome and catecholaminergic polymorphic ventricular tachycardia, data regarding its use in other cardiac conditions are sparse. This series illustrates that CSD may be a viable treatment option for patients with a variety of etiologies of VAs.

Video-Assisted Thoracoscopic Left Cardiac Sympathetic Denervation in Patients with Hereditary Ventricular Arrhythmias

BACKGROUND

Left cardiac sympathetic denervation (LCSD) has been underutilized in patients with hereditary ventricular arrhythmia syndromes such as congenital long QT syndrome (LQTS) and catecholaminergic polymorphic ventricular tachycardia (CPVT). The purpose of this study was to investigate the safety and efficacy of video-assisted thoracoscopic (VATS) LCSD in such patients.

METHODS

Fifteen patients (four men, 24.6 ± 10.5 years old) who underwent VATS-LCSD between November 2010 and January 2015 for hereditary ventricular arrhythmia syndromes at Kyungpook National University Hospital were enrolled in this study. The safety and efficacy of VATS-LCSD were evaluated by periprocedural epinephrine tests and assessing the development of complications and cardiac events during follow-up.

RESULTS

Fourteen patients with LQTS and one patient with CPVT underwent VATS-LCSD. Six and one patients developed ventricular tachyarrhythmia during preprocedural and postprocedural epinephrine test, respectively (P = 0.063). No serious complications such as Horner syndrome, pneumothorax, or bleeding developed after LCSD. Mean hospital stay after VATS-LCSD was 3.7 ± 1.5 days. During a mean follow-up of 927 ± 350 days, one LQTS patient and one CPVT patient, neither of whom manifested tachyarrhythmia during post-LCSD epinephrine test, developed torsades de pointes and syncope, respectively. The annual event rates of six patients who were symptomatic during the period preceding LCSD decreased from 0.97 to 0.19 events/year (P = 0.045).

CONCLUSIONS

VATS-LCSD was a safe, and effective procedure for patients with hereditary ventricular tachycardia syndrome, with no serious adverse events and with short hospital stay.

Analytic Reviews: Electrophysiologic Testing in the Intensive Care Unit

The role of electrophysiologic concepts and procedures in managing patients with potentially life-threatening ar rhythmias in the intensive care unit is discussed. These patients may be survivors of sudden cardiac arrest or myocardial infarction or may be admitted for syncope or sustained or nonsustained ventricular tachycardia. The value of electrophysiologic testing is discussed in terms of the distinction between wide QRS complex tachycardias that are supraventricular or ventricular in origin and those in which preexcitation syndromes may be important. Drug-induced ventricular arrhythmias are discussed, with specific emphasis on torsades de pointes. Finally, the use of His bundle recordings in pa tients with atrioventricular conduction disturbances is discussed. The methodology of electrophysiologic test ing, including stimulation protocols and interpretation of results, is described.

Minimal Access Posterior Approach for Extrapleural Thoracic Sympathectomy: A Cadaveric Study and Cases

OBJECTIVE

Operatively, video-assisted thoracoscopic sympathectomy (VATS) involves pleural entry and poses risk in small children and patients with pulmonary disease. A conventional posterior sympathectomy is more invasive than VATS. We investigated a cadaveric feasibility study of a minimal access posterior approach for endoscopic extrapleural sympathectomy and discuss this minimal approach in children with cardiac sympathectomy.

METHODS

A posterior endoscopic extrapleural approach for thoracic sympathectomy was performed using lightly embalmed cadavers; surgical corridor depth, width, and associated pleural violation were recorded. Two pediatric cases undergoing secondary prevention for breakthrough cardiac dysrhythmias using this approach are discussed: case 1, a 9-year-old girl with refractory long QT syndrome; and case 2, a 13-year-old boy with hypertrophic cardiomyopathy.

RESULTS

The cadaveric study supported 100% identification of a craniocaudal-oriented sympathetic chain using an 18-mm tubular retractor, and a 10% pleural violation rate. There were no clinically significant pneumothoracies in either proof of concept cases.

CONCLUSIONS

Minimal access posterior extrapleural sympathectomy is feasible to expose the sympathetic chain in the thoracic region with good visualization using either endoscopic or microscopic magnification. Single-position bilateral thoracic sympathectomy can be performed in pediatric patients with life-threatening ventricular arrhythmias. Based on the cadaveric study and the 2 preliminary cases, we believe that a posterior minimal access approach allows safe and effective access to the thoracic sympathetic chain for causes requiring sympathectomy using single positioning, with minimal risk of pneumothorax or Horner syndrome.

Neuraxial modulation for refractory ventricular arrhythmias: value of thoracic epidural anesthesia and surgical left cardiac sympathetic denervation

BACKGROUND

Reducing sympathetic output to the heart from the neuraxis can protect against ventricular arrhythmias. The purpose of this study was to assess the value of thoracic epidural anesthesia (TEA) and left cardiac sympathetic denervation (LCSD) in the management of ventricular arrhythmias in patients with structural heart disease.

METHODS AND RESULTS

Clinical data of 14 patients (25 to 75 years old, mean+/-SD of 54.2+/-16.6 years; 13 men) who underwent TEA, LCSD, or both to control ventricular tachycardia (VT) refractory to medical therapy and catheter ablation were reviewed. Twelve patients were in VT storm, and 2 experienced recurrent VT despite maximal medical therapy and catheter ablation procedures. The total number of therapies per patient before either procedure ranged from 5 to 202 (median of 24; 25th and 75th percentile, 5 and 56). Eight patients underwent TEA, and 9 underwent LCSD (3 patients had both procedures). No major procedural complications occurred. After initiation of TEA, 6 patients had a large (> or =80%) decrease in VT burden. After LCSD, 3 patients had no further VT, 2 had recurrent VT that either resolved within 24 hours or responded to catheter ablation, and 4 continued to have recurrent VT. Nine of 14 patients survived to hospital discharge (2 TEA alone, 3 TEA/LCSD combined, and 4 LCSD alone), 1 of the TEA alone patients underwent an urgent cardiac transplantation.

CONCLUSIONS

Initiation of TEA and LCSD in patients with refractory VT was associated with a subsequent decrease in arrhythmia burden in 6 (75%) of 8 patients (68% confidence interval 51% to 91%) and 5 (56%) of 9 patients (68% confidence interval 34% to 75%), respectively. These data suggest that TEA and LCSD may be effective additions to the management of refractory ventricular arrhythmias in structural heart disease when other treatment modalities have failed or may serve as a bridge to more definitive therapy.

Thoracoscopic sympathectomy for palmaris hyperhidrosis

INTRODUCTION

Palmaris hyperhidrosis is a disorder mediated by the sympathetic nervous system. It causes excessive sweating. This study evaluated the safety, efficacy, and outcome after thoracoscopic sympathectomy in patients with palmaris hyperhidrosis.

METHODS

We reviewed the medical records of 18 patients (10 male) who underwent bilateral thoracoscopic sympathectomy between July 1998 and June 2001.

RESULTS

The patients' mean age was 34 years. No conversions to thoracotomy occurred. Three 2- to 5 mm trocars were used. The thoracic sympathetic chain was resected from ganglia T2-T4, except in one patient with axillary hyperhidrosis requiring resection to T5. The mean operating time was 112 minutes, the mean blood loss was 50 ml, and the mean postoperative hospital stay was 1.2 days. Two patients had a unilateral pneumothorax requiring tube thoracostomy; one patient developed a chest wall hematoma at a trocar site that resolved without treatment, and one patient developed a transient unilateral Horner's syndrome. There have been no hospital readmissions. After a mean follow-up period of 14 months, 11 patients (56%) reported compensatory sweating. Sixteen patients (89%) were satisfied with their outcomes. One patient was dissatisfied because of excessive compensatory sweating, and another continues to have mild unilateral sweating on one hand and compensatory sweating of the face.

CONCLUSION

Thoracoscopic sympathectomy is a safe and effective alternative treatment for palmaris hyperhidrosis. Compensatory sweating occurs in more than 50% of patients but is tolerable in most. The majority of patients are satisfied with their short-term outcomes.

Holter changes resulting from right-sided and bilateral infrastellate upper thoracic sympathectomy

BACKGROUND

We tested the hypothesis that no right-sided dominance exists after infrastellate surgical upper-thoracic sympathectomy. We aimed to confirm whether a significant bradycardia was constant and only dependent on the right side.

METHODS

We performed 24-hour Holter electrocardiographic recordings in 12 patients referred for bilateral sympathectomy. Surgery was performed at two distinct times allowing for the study of the consequences of unilateral right and bilateral sympathectomy.

RESULTS

Heart rate was 77 +/- 8 beats per minute before surgery on the 24-hour recording and significantly decreased after bilateral (67.8 +/- 6.5 beats per minute; p < 0.05) but not after unilateral right sympathectomy. Consistently spectral analysis variables significantly changed after bilateral surgery but showed no right-sided dominance. Little effect of sympathectomy was found on the QT interval, which tended to decrease after bilateral sympathectomy.

CONCLUSIONS

Patients should be informed of the bradycardia resulting from sympathectomy. No right-sided dominance can be found consistently with the random distribution of substellate cardiac fibers reported in anatomic studies.

Long QT Syndromes

The clinical phenotype of the long QT syndrome (LQTS) is quite variable, with the frequency and type of life-threatening arrhythmias influenced by the specific genotype and a spectrum of genetic and environmental factors that are not well characterized. Patients with a history of recurrent syncope or aborted cardiac arrest are at increased risk of experiencing malignant ventricular arrhythmias, but such arrhythmias may also occur in affected individuals who previously have been asymptomatic. Beta-adrenergic drugs serve as the foundation for treatment of symptomatic patients with a history of syncope or aborted cardiac arrest and as primary prophylactic therapy in asymptomatic subjects with LQTS. Beta-blockers reduce the frequency of syncopal events, but they do not absolutely prevent the occurrence of sudden cardiac death, even in those who are compliant in taking full doses of beta-blockers. Pacemaker therapy is moderately effective in reducing the number of cardiac events in patients with inappropriate bradycardia. The implantable cardioverter-defibrillator (ICD) has functioned well as a fail-safe back-up therapy in high-risk patients, especially those with documented malignant arrhythmias or an aborted cardiac arrest. Left cervicothoracic sympathetic ganglionectomy should be reserved for patients with LQTS who are intolerant of beta-blockers or have recurrent syncope that is refractory to beta-blockers and who for one reason or another are not candidates for ICD therapy. Pharmacologically tailored gene-specific therapy for specific ion-channel disorders is in its infancy, and no specific recommendations can be made for the use of this therapy at this time.

Arrhythmias in the congenital long QT syndrome: how often is torsade de pointes pause dependent?

OBJECTIVE

To determine the frequency and predictors of pause dependent torsade de pointes among patients with the congenital long QT syndrome and spontaneous ventricular tachyarrhythmias.

DESIGN

The literature on the "congenital long QT" was reviewed. Articles with illustrations demonstrating the onset of spontaneous polymorphic ventricular arrhythmias in the absence of arrhythmogenic drugs were included.

RESULTS

Illustrations of 62 spontaneous episodes of torsade de pointes among patients with congenital long QT syndrome were found in the literature. The majority (74%) of documented arrhythmias were "pause dependent"; 82% of these pauses were longer than the basic cycle length by > 100 ms. Age and sex correlated with the mode of arrhythmia initiation. Arrhythmias in infants (</= 3 years old) were not pause dependent, while female sex correlated with pause dependent torsade. Using multivariate analysis, age was the only independent predictor of the mode of onset of torsade de pointes.

CONCLUSION

Available data suggest that the majority of spontaneous arrhythmias in the congenital long QT syndrome are pause dependent. Torsade de pointes that is not preceded by pauses appears to be limited to patient subgroups with severe forms of the disease, like symptomatic infants. These findings have important implications regarding the use of cardiac pacing for arrhythmia prevention.

Long QT syndrome

In conclusion, much has been learned in the past several years regarding the molecular biology of LQTS, and this information has been directly applicable to the clinical care of patients with this syndrome. The knowledge also has been of considerable importance for understanding the molecular basis of arrhythmias in general and is providing insights into potential molecular-based therapies for arrhythmias.

Vasomotor and sudomotor function in the hand after thoracoscopic transection of the sympathetic chain: implications for choice of therapeutic strategy

The degree of sympatholysis achieved by thoracoscopic transection of the sympathetic chain (sympathicotomy) was evaluated by measuring sudo- and vasomotor function in the hands before and after surgery in 12 patients with palmar hyperhidrosis. Our results show a marked reduction in sweat production and a cutaneous vasodilatation which remained unchanged during the 6 months follow-up, whereas sudo- and vasomotor reflexes normalized within this time. Skin temperature variations did not correlate to skin perfusion changes. Since all subjects reported dry and warm hands throughout the follow-up period, our results indicate that recording reflex responses to sympathoexcitatory stimuli does not adequately reflect clinical outcome of subtotal sympatholytic procedures performed for hyperhidrosis. Monitoring of clinical outcome should therefore include measurement of baseline sweat production and skin perfusion. However, the normalized reflex responses highlight the incomplete sympatholysis achieved by thoracoscopic sympathicotomy, which may be beneficial in some pathological conditions (such as hyperhidrosis) but detrimental in others.

Polymorphic ventricular tachyarrhythmias in the absence of organic heart disease: classification, differential diagnosis, and implications for therapy

Different polymorphic ventricular tachyarrhythmias may cause syncope or cardiac arrest in patients with no heart disease: (1) Catecholamine-sensitive polymorphic ventricular tachycardia (VT) presents during childhood: the hallmark is the reproducible provocation of atrial and polymorphic ventricular arrhythmias during exercise, despite a normal QT. Beta-blockers are the treatment of choice. (2) In the long QT syndromes (LQTS), malfunction of ion channels leads to prolonged ventricular repolarization, early afterdepolarizations, and triggered ventricular arrhythmias. Therapeutic options include: beta-blockers, genotype-specific therapy, cardiac sympathetic denervation, and implantation of pacemakers or defibrillators. (3) The "short-coupled variant of torsade de pointes" is a malignant disease that shares several characteristics with idiopathic ventricular fibrillation. Although verapamil is frequently recommended, mortality rates remain high. (4) Idiopathic ventricular fibrillation (VF) with normal electrocardiogram (ECG) strikes young adults of both genders. In contrast to other polymorphic tachyarrhythmias, idiopathic VF is not generally related to stress. Also, familial involvement is rare. Therapeutic options include implantation of defibrillators and therapy with class 1A drugs. (5) The "Brugada syndrome" and the "syndrome of nocturnal sudden death" strike males almost exclusively. Right bundle branch block (RBBB) with ST elevation in the right precordial leads-the "Brugada sign"--is seen in the ECG of both patient populations. Implantation of defibrillators is recommended.

Management of patients with the hereditary long QT syndrome

The hereditary long QT syndrome is an inherited ion channel disorder with QT prolongation, morphologic changes in the T waves, and a relatively high frequency of syncope, T wave alternans, torsades de pointes-type ventricular tachycardia, and sudden death. Monotherapy with beta blockers is the treatment of first choice. In patients with recurrent syncope despite therapy with beta blockers, pacemakers and/or ganglionectomy may be useful in selected cases, with an implantable cardioverter defibrillator used as a fail-safe approach in high-risk patients.

Long QTc and torsades de pointes in human immunodeficiency virus disease

Three patients with human immunodeficiency virus (HIV) infection presented with QT, prolongation (> 440 ms) and torsades de pointes. We sought to evaluate the etiology of the long QT syndrome in these patients without previously identified causes for QT, prolongation, and determine the prevalence among patients with HIV infection. The three index patients underwent: (1) left stellate ganglion block; (2) beta-blocker challenge; and (3) electrocardiographic stress testing. QTc interval was measured before and after intervention. We undertook a retrospective analysis of prevalence of QTC prolongation among all patients with computerized ECGs over a 6-month period at one institution and compared it to the prevalence in hospitalized patients with HIV disease. Thirty-four thousand one hundred eighty-one patients with computerized ECGs were screened for QTc prolongation. Forty-two hospitalized patients with HI disease had computerized ECG during the same 6-month period. In the three index patients, the QTc failed to shorten with left stellate ganglion blockade, beta-blocker challenge, or stress testing, suggesting an acquired form of the long QT syndrome in these patients with HIV disease. None had previously recognized acquired causes of QT, prolongation. Mexiletine hydrochloride was useful in preventing recurrences of torsades de pointes. We observed a 7.0% prevalence of QT, prolongation among all patients screened. Hospitalized patients with HIV disease (n = 42) during this same period, demonstrated an increased prevalence of QT, prolongation (28.6%, P = 0.002). Patients with HIV disease have a significantly higher prevalence of QTc prolongation than a general hospital-based population, may have an unrecognized acquired form of the long QT syndrome, and are at risk for torsades de pointes.

Clinical management of patients with the long QT syndrome: drugs, devices, and gene-specific therapy

The familial long QT syndrome (LQTS) is now recognized as a genetic channelopathy with a propensity to arrhythmogenic syncope and sudden death. Three genetic mutations have been identified that involve the slow and fast delayed potassium rectifier currents and the sodium current. Distinctive ECG-T wave phenotypes are associated with each of the three genotypes. Current day therapy includes: beta-adrenergic blocking drugs; pacemakers; left cervicothoracic sympathetic ganglionectomy; implanted cardioverter defibrillators; and possibly, drugs that improve mutant ionic channel dysfunction. LQTS has provided unique insight into the complex relationship between ionic channel dysfunction and ventricular tachyarrhythmias.

Mode of onset of torsade de pointes in congenital long QT syndrome

OBJECTIVES

We sought to describe the mode of onset of spontaneous torsade de pointes in the congenital long QT syndrome.

BACKGROUND

Contemporary classifications of the long QT syndrome (LQTS) refer to the congenital LQTS as "adrenergic dependent" and to the acquired LQTS as "pause dependent." Overlap between these two categories has been recognized, and a subgroup of patients with "idiopathic pause-dependent torsade" has been described. However, it is not known how commonly torsade is preceded by pauses in the congenital LQTS.

METHODS

We reviewed the electrocardiograms (ECGs) of all our patients with congenital LQTS evaluated for syncope or sudden death (30 patients). Documentation of the onset of torsade de pointes was available for 15 patients. All these patients had "definitive LQTS" by accepted clinical and ECG criteria.

RESULTS

Pause-dependent torsade de pointes was clearly documented in 14 of the 15 patients (95% confidence interval 68% to 100%). The cycle length of the pause leading to torsade was 1.3 +/- 0.2 times longer than the basic cycle length, and most pauses leading to torsade were unequivocally longer than the preceding basic cycle length (80% of pauses were > 80 ms longer than the preceding cycle length).

CONCLUSIONS

The "long-short" sequence, which has been recognized as a hallmark of torsade de pointes in the acquired LQTS, plays a major role in the genesis of torsade in the congenital LQTS as well. Our findings have important therapeutic implications regarding the use of pacemakers for prevention of torsade in the congenital LQTS.

Evidence of a long QT founder gene with varying phenotypic expression in South African families

We report five South African families of northern European descent (pedigrees 161, 162, 163, 164, and 166) in whom Romano-Ward long QT syndrome (LQT) segregates. The disease mapped to a group of linked markers on chromosome 11p15.5, with maximum combined two point lod scores, all generated at theta = 0, of 15.43 for the D11S922, 10.51 for the D11S1318, and 14.29 for the tyrosine hydroxylase (TH) loci. Recent studies have shown that LQT is caused by an Ala212Val mutation in a potassium channel gene (KVLQT1) in pedigrees 161 to 164. We report that the same mutation is responsible for the disease in pedigree 166. Haplotype construction showed that all the families shared a common haplotype, suggesting a founder gene effect. DNA based identification of gene carriers allowed assessment of the clinical spectrum of LQT. The QTc interval was significantly shorter in both carriers and non-carriers in pedigree 161 (0.48 s and 0.39 s, respectively) than the same two groups in pedigree 161 (0.52 s and 0.42 s, respectively). The spectrum of clinical symptoms appeared more severe in pedigree 162. The possible influence of modulating genetic factors, such as HLA status and sex of family members, on the expression of an LQT founder gene is discussed.

Posterior left thoracic cardiac sympathectomy by surgical division of the sympathetic chain: an alternative approach to treatment of the long QT syndrome

Although high thoracic left sympathectomy via an anterior surgical approach is a highly efficacious treatment for refractory ventricular arrhythmias in patients with the long QT syndrome, the degree of sympathetic denervation has been variable, success of the operation is influenced by anatomical differences between patients, and Horner's syndrome may result. We hypothesized that interruption of sympathetic input to the heart could be accomplished using a posterior thoracic approach to this variable and often complex anatomy by division of the sympathetic chain rather than by direct destruction of the stellate and superior thoracic ganglia with the more conventional anterior, supraclavicular approach. In addition, the posterior approach should decrease the risk of Horner's syndrome by avoiding the ocular sympathetic efferent nerves. This posterior approach is described in five patients with the long QT syndrome and recurrent ventricular arrhythmias. After a mean follow-up of 18 +/- 12 months, all are alive without Horner's syndrome.

Abnormal cardiac sensory innervation associated with experimentally induced, electrocardiographic long QT intervals in chick embryos

Prolongation of the QT interval in the ECG can be induced in d 17 chick embryos by ablating the nodose placode on the right side on d 1 of development. The nodose placode contains the precursor cells which form the neurons of the nodose (inferior vagal) ganglion. Neurons in this ganglion provide sensory innervation to the heart and other viscera. In this study, we measured ganglion volume and neuron size and number in the right and left nodose ganglia in d 17 experimental and control embryos from whom electrocardiograms had been obtained. A significant reduction in the number of neurons present in the right nodose ganglion, relative to the left ganglion, was evident in all embryos with abnormally prolonged QT intervals. Embryos with prolonged QT, as well as lesioned embryos who demonstrated normal.QT on d 17, also had abnormally small neurons in both right and left nodose ganglia, indicating an additional nonspecific, perhaps permissive, effect of the lesion. These results suggest that abnormal development of the sensory innervation of the heart may be an important link in the chain of events leading to the developmental long QT syndrome expressed by these embryos.

Clinical relevance of cardiac arrhythmias generated by afterdepolarizations. Role of M cells in the generation of U waves, triggered activity and torsade de pointes

Recent findings point to an important heterogeneity in the electrical behavior of cells spanning the ventricular wall as well as important differences in the response of the various cell types to cardioactive drugs and pathophysiologic states. These observations have permitted a fine tuning and, in some cases, a reevaluation of basic concepts of arrhythmia mechanisms. This brief review examines the implications of some of these new findings within the scope of what is already known about early and delayed afterdepolarizations and triggered activity and discusses the possible relevance of these mechanisms to clinical arrhythmias.

Role of vagotony in sinus node dysfunction in children with symptomatic congenital long QT syndrome

The present study examined chronotropic dysfunction and the role of vagotony in congenital long QT syndrome, sinus node function and the effects of parasympathetic blockade. Six patients with congenital long QT syndrome were studied. The four males and two females, aged 1-15 years, had episodes of syncope and malignant ventricular arrhythmias. Congenital long QT syndrome was defined as a corrected QT interval greater than 0.45 s, T wave alternans and the age at diagnosis. The sinus heart rate measured from a 24 h electrocardiograph was abnormally low (< 50 min) in three patients (1, 4 and 5 years old) and did not increase sufficiently with the administration of atropine in five of the six patients with congenital long QT syndrome. From intracardiac electrophysiological studies, the corrected sinus node recovery time was prolonged in three patients and the total sinoatrial conduction time was prolonged in two patients. In most patients who had an abnormally long sinoatrial conduction time and corrected sinus node recovery time, these values returned to normal following atropine administration. In one patient, the corrected sinus node recovery time was prolonged paradoxically by atropine. Sinus node dysfunction in congenital long QT syndrome was affected by vagotony associated with a right sympathetic nerve system abnormality.

The congenital long QT syndromes in childhood

Twenty-three children and young persons with a congenital long QT syndrome were identified; the median age at the time of referral was 10 years (range 4 days to 19 years) and 14 patients (61%) had a family history of the syndrome. Among the 19 patients with symptoms, the initial symptom was syncope in 13 (69%), aborted sudden death in 5 (26%) and near drowning in 1 (5%). There were three deaths during a combined follow-up period of 67 patient-years (average annual mortality rate 4.5%). Patients who did not respond to therapy with a beta-adrenergic blocker and those who died were significantly younger than the remaining patients at the time of diagnosis (p less than or equal to 0.05 for both). Analysis of 44 treadmill exercise tests performed by 16 patients revealed significant prolongation of the median corrected QT (QTc) interval in response to exercise, with maximal prolongation present after 2 min of recovery (median QTc interval 0.52 s versus a baseline value of 0.47 s, p less than 0.001). Characteristic changes in T wave configuration were noted in 8 of 15 patients on at least one occasion during ambulatory Holter electrocardiographic monitoring, including T wave alternation in two patients, both of whom died shortly afterward. It is suggested that the congenital long QT syndrome is associated with a significant mortality rate in childhood despite the use of conventional therapy in symptomatic patients. Ambulatory Holter monitoring and treadmill exercise testing may be helpful, both in confirming the diagnosis of a long QT syndrome and in monitoring the adequacy of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Atenolol in children with ventricular arrhythmias

Twenty children and adolescents treated orally with atenolol for chronic paroxysmal ventricular tachycardia (n = 10) or Long QT Syndrome (n = 10) over a 5 year period were retrospectively evaluated to ascertain the efficacy of arrhythmia suppression, the effective dosage, the cardiovascular effects, and the incidence of adverse effects. Patients with paroxysmal ventricular tachycardia were classified by their response to exercise or catecholamines. Atenolol was effective in each patient (n = 5) whose tachycardia was precipitated or exacerbated by exercise or catecholamines when the patient was receiving a dosage of approximately 1.7 mg/kg/day. In those patients (n = 4) in whom exercise or catecholamines either suppressed or had no effect on the tachycardia, none were effectively treated in spite of receiving comparable dosages. Three of these four patients also had structural abnormalities or myocardial dysfunction. Atenolol was effective in treating 4 of 10 patients with long QT syndrome with a dosage of approximately 1.5 mg/kg/day. Six ineffectively treated patients received similar dosages, and four required either additional medication or surgical sympathectomy for persistent syncope. The other two patients died suddenly. Cardiovascular side effects included bradycardia in three patients and hypotension in one. Noncardiovascular effects included mild fatigue (four patients) headache (two), sleep disturbance (two), and difficulty concentrating (one). The medication was discontinued because of side effects in two patients. Atenolol is more likely to be effective in the suppression of paroxysmal ventricular tachycardia in children if the tachycardia is exacerbated by exercise or catecholamines and if the heart is otherwise normal.

Surgical treatment of dysrhythmias in infants and children

The recognition of medically refractory dysrhythmias in children has necessitated the use of more invasive nonpharmacologic therapies. The role of ablative surgery in the management of pediatric rhythm disturbances is presented.

Pharmacologic blockade of the left stellate ganglion using a drug-reservoir-pump system

Patients suffering from the long QT syndrome (LQTS) are threatened by sudden arrhythmic cardiac death. This case report describes a new therapeutic approach to ventricular tachyarrhythmias refractory to oral pharmacological treatment (propranolol + phenytoin) using a drug-reservoir-pump system for the pharmacologic blockage of the left stellate ganglion.

Scintigraphic detection of regional disruption of adrenergic neurons in the heart

Experiments were designed to detect regional disruptions of adrenergic neurons in the hearts of living dogs. The neuron disruption was achieved by the application of phenol to the epicardium of the left ventricle. Evidence for denervation was the reduction in endogenous norepinephrine (NE) concentrations in the myocardium beneath the region of phenol treatment and toward the apex. Radiolabeled meta-iodobenzylguanidine (MIBG) acts as an analog of NE and as such is concentrated in adrenergic nerve terminals. Following phenol application, MIBG labeled with 125I was found, 20 hours after injection, to be distributed within myocardium in patterns comparable to those of NE. However, left stellectomy did not alter the distributions of NE or 125I-MIBG in the myocardium and apparently did not disrupt adrenergic innervation. MIBG labeled with 123I enabled scintigraphic images of heart neurons in the living dog 3 and 20 hours after injection; these images portrayed the regions of adrenergic neuron disruption caused by phenol treatment. Concentrations of thallium-201 depicted on scintigraphic image and of triphenyltetrazolium observed on in vitro staining demonstrated no myocardial injury. Thus scintigraphy with 123I-MIBG will display regional adrenergic denervations in the heart.