Ventricular fibrillation induction and diffuse abnormal ST-segment response to ajmaline in a patient with apparent pre-existing dynamic right bundle branch block.

OBJECTIVE: ST-segment elevation in the right precordial electrocardiography (ECG) leads in Brugada syndrome (BS) can be unmasked by class I anti-arrhythmic drugs (sodium channel blockers) administration. It is still debated whether this ECG pattern is better explained by abnormal repolarization or ventricular conduction and depolarization. Conduction diseases can conceal type 1 BS-like ECG in standard V1-V3 leads. ECG alterations were found also in alternative leads. The role of electrophysiology study (EPS) in sudden cardiac death risk stratification remains controversial, and could depend on the phenotypic expression of the cardiac sodium channels disease. CASE REPORT: We describe unmasked diffuse J-point and ST-segment anomalies in peripheral and precordial ECG leads and ventricular fibrillation (VF) induction by EPS after ajmaline administration in a patient with pre-existing atypical right bundle branch block (RBBB) concealing subtle anomalies in standard V1-V3 leads. RBBB was influenced by the underlying BS-like ECG associating repolarization anomaly and pre-existing conduction disease. EPS induced VF when RBBB was associated with BS-like ECG, and failed to induce VF when RBBB was present alone. CONCLUSIONS: BS phenotype heterogeneity requires further studies to improve the knowledge of its pathophysiological mechanisms associated with conduction diseases in order to better identify an individual therapy and prognostic stratification.

Exercise testing in children with Wolff-Parkinson-White syndrome: what is its value?

This study was conducted to evaluate the accuracy of exercise testing for predicting accessory pathway characteristics in children with Wolff-Parkinson-White (WPW) syndrome. The study enrolled 37 children with WPW syndrome and candidates for invasive electrophysiologic study (EPS). Exercise testing was performed for all the study participants before the invasive study. Data from the invasive EPS were compared with findings from the exercise testing. The sudden disappearance of the delta (Δ) wave was seen in 10 cases (27 %). No significant correlation was found between the Δ wave disappearance and the antegrade effective refractory period of the accessory pathway (AERP-AP) or the shortest pre-excited RR interval (SPERRI). The sensitivity, specificity, and positive and negative predictive values of Δ wave disappearance, based on AERP-AP as gold standard, were respectively 29.4, 80, 71.4, and 40 %. The corresponding values with SPERRI as the gold standard were respectively 23.8, 71.4, 71.4 and 23.8 %. Exercise testing has a medium to low rate of accuracy in detecting low-risk WPW syndrome patients in the pediatric age group.

Extracardiac minimal invasive implantation of cardioverter defibrillator in young children.

Implantable cardioverter defibrillator (ICD) placement in young children remains a challenge due to device-patient size mismatch and the important choice between an endovenous or an epicardial approach for lead implantation. We treated three children, with respectively Long QT-syndrome, Brugada syndrome and Brugada syndrome with sick sinus syndrome, ranging from 9 months to 7 years with a subxyphoidal ICD and extracardiac lead implantation by minimally invasive techniques. In all cases the thresholds were excellent. The devices could be properly placed in the preperitoneal space without discomfort to the patients. The clinical course was uneventful and results were excellent.

Hypertrophic cardiomyopathy and planned in vitro fertilization. Genetic testing and clinical evaluation.

Hypertrophic cardiomyopathy (HCM) is often transmitted to the offspring of affected individuals. This case report describes the role of genetic screening in a 39-year-old woman with a family history of sudden cardiac death. The patient wished to become pregnant and was seeking medical consultation. In addition to electro- and echocardiograms, genomic DNA was isolated and direct sequencing was employed to screen the patient for some of the most common genes that cause HCM. A pathogenic heterozygous mutation c.700 g > a p.Arg186Gln in TNNI3 was identified, which was not found in 200 normal control chromosomes. Mutation-specific genetic testing was also performed in four family members, and the same mutation was absent. Genetic screening appears cost effective in familiar members with a known mutation, provides important information about the affected individual, and can facilitate the future management of family members and offspring.

Propofol-induced coved-type electrocardiogram during catheter ablation of paroxysmal atrial fibrillation. A case of Brugada syndrome?

We report a case of a young man with paroxysmal atrial fibrillation, in whom a characteristic coved-type Brugada pattern developed during catheter ablation performed under sedation with propofol. After immediate discontinuation of the propofol infusion, coved-type ST-segment elevation gradually resolved and no ventricular arrhythmias occurred. An ajmaline challenge failed to unmask a coved-type electrocardiogram and genetic testing was negative for ion channel mutations related to Brugada syndrome.

Unusual capture of a capture beat. Lessons learned from the 12-lead electrocardiogram.

In a 63-year-old woman, several capture beats were documented during a slow, right bundle-branch block tachycardia. These occur whenever retrograde conduction is lacking due to ventriculoatrial Wenckebach block. The 12-lead electrocardiogram suggested a ventricular origin in the area of the left posterior papillary muscle which was confirmed by endocardial activation mapping. The focal ventricular tachycardia was successfully ablated, and the patient has remained arrhythmia-free during follow-up.

Monitoring the safety of antiepileptic medication in a child with Brugada syndrome.

We report the case of an 8 year old boy presenting with episodes of decreased consciousness. As the boy's father died of a sudden cardiac death (SCD) at the age of 31 years, among other causes a Brugada syndrome (BS) was suspected. The boy was further examined at the UZ Brussels Heart Rhythm Management Center. The intravenous administration of ajmaline confirmed a BS without ventricular arrhythmias. Syncope in children can be an imminent sign of BS. BS is a life threatening condition that can deteriorate into SCD. The boy presented with episodes of lowered consciousness, transpiration and paleness. Readmission for further investigation was required. Clinical observation and continuous registered EEG during sleep showed multiple epileptical incidents. Hence the child was diagnosed with new onset epilepsy. For initiation of antiepileptic therapy, the patient was admitted at the pediatric intensive care unit (PICU). Close clinical observation and cardiovascular monitoring with continuous 12-lead ECG registration were performed during orally administered sodium valproic acid. During this anticonvulsive treatment in a child with documented BS no significant alterations in ECG-findings were observed. In this particular patient sodium valproic acid treatment can be estimated as a safe anticonvulsive therapy.

Brugada syndrome: the prognostic dilemma and value of sincope.

Since its first description in 1992 as a new clinical entity, the Brugada syndrome has stimulated great interest among physicians and basic scientists. In 2002 and 2005, two consensus conferences have respectively defined the diagnostic criteria for the syndrome. Currently the diagnosis of Brugada syndrome is based on a combination of clinical events (syncope and/or sudden cardiac death due to malignant ventricular arrhythmias) and electrocardiographic features (pathognomonic ST-segment elevation morphology). In the last years, many advances have been done in the knowledge about the genetic basis, the cellular mechanisms responsible for the typical electrocardiography features, susceptibility to ventricular arrhythmias and risk stratification. The implantable cardioverter defibrillator remains the only therapeutic option of proven efficacy for primary and secondary prophylaxis of sudden cardiac death. Identification of high risk subjects is one of the major goals in clinical decision-making. Syncope is ubiquitously recognized as a bad prognostic marker in Brugada syndrome. However, young individuals with this disease may suffer from vaso-vagal instead of arrhythmic syncope. The prognostic significance of syncope in patients with Brugada syndrome is discussed in this review.

The Brugada syndrome: update 2006.

Over the last 14 years - since the Brugada syndrome was first recognized as a distinct clinical/electrocardiographical entity - a considerable number of papers have been published on its various aspects. It has been defined as the combination of a typical ST-segment elevation in the right precordial leads and a predisposition for malignant ventricular arrhythmias occurring in the absence of structural heart disease. From the outset, controversy arose about the diagnostic criteria to be applied. This issue has been clarified since the announcement of a first (2002) and second (2005) consensus report. Our review will discuss the clinical characteristics and different possible pathophysiological mechanisms underlying the specific ECG-abnormalities and susceptibility for malignant arrhythmias. Nowadays, the main issue of discussion revolves essentially around its prognostic features, especially in asymptomatic patients. This review will compare the results of different follow-up studies and yields a possible explanation for the differences in event rates and in the identification of useful sudden-death predictors. Finally, the most recent data concerning new diagnostic techniques, gene identification and future therapeutic options will also be discussed.

What evidence do we have to replace in-hospital implantable cardioverter defibrillator follow-up?

INTRODUCTION: Due to the increasing number of patients with an implantable cardioverter defibrillator (ICD), new options for ICD patient follow-up management are required. METHODS: Patients with ICD indication according to the guidelines received an ICD with Home Monitoring technology. The devices enabled the transmission of the relevant episode, therapy, and system integrity data. Patients were followed for 12 months with routine controls every 3 months. The physician analyzed the Home Monitoring data before the routine follow-up visit (FU) and gave a forecast on the necessity of the pending FU, which was compared with the evaluation after the FU. Based on the derived forecast reliability, a patient management scheme was developed and its impact on patient safety was assessed retrospectively. RESULTS: A total of 271 patients were enrolled (40 f, mean age 62+/-12 years, mean LVEF 39+/-15%, 65% ischemic heart disease, 20% cardiomyopathy) and followed for 339+/-109 days. Of 908 pairs of Home Monitoring data and FU data evaluation, 129 there were false negative results for 92 patients. Safety concerns from false negative forecasts can be minimized with a patient management scheme containing the following elements: 1) never skip the first routine FU; 2) never skip a routine FU for a patient having already shown pacing threshold problems; 3) perform FU following hospitalizations; 4) perform FU following episode detection by the ICD; and 5) perform a routine FU if the patient reports symptoms. The retrospective analysis showed, that if the patients had been managed using this scheme, 503 of 1079 routine FU could have been skipped with only one safety concern, a three month delay in the detection of silent paroxysmal atrial fibrillation in one patient. CONCLUSIONS: Home Monitoring in ICD therapy over 12 months is feasible. The data transmitted relevantly contribute to a remarkable reduction of follow-up burden and enable the individualization of routine follow-up.

The Brugada Syndrome.

In 1992 a syndrome was described consisting of syncopal episodes and/or (resuscitated) sudden death in patients with a structurally normal heart and a characte ristic electrocardiogram (ECG) displaying a pattern resembling a right bundle branch block with ST segment elevation in leads V1 to V3. The disease is genetically determined with an autosomal dominant pattern of transmission in 50% of the familial cases. Several different mutations have been identified affecting the structure, function and trafficking of the sodium channel. The syndrome is ubiquitous. Its incidence and prevalence are difficult to estimate, but this disease may cause 4 to 10 sudden deaths per 10,000 inhabitants per year representing the most frequent cause of natural death in males younger than 50 in South Asia. The disease has been linked to the sudden infant death syndrome (SIDS) and to the sudden unexpected death syndrome (SUDS) by showing that the electrocardiogram and mutations are the same as in Brugada syndrome. The diagnosis is easily made by means of the ECG when it is typical. There exist, however, patients with concealed and intermittent electrocardiographic forms that make the diagnosis difficult. The ECG can be modulated by changes in autonomic balance, body temperature, glucose level and the administration of antiarrhythmic, neuroleptic and antimalaria drugs. Beta adrenergic stimulation normalizes the ECG. Loss of the action potential dome in right ventricular epicardium but not in endocardium underlies the ST segment elevation. Electrical heterogeneity within right ventricular epicardium leads to the development of closely coupled extrasystoles via phase 2 reentry that precipitate ventricular ,fibrillation. Antiarrhythmic drugs do not prevent sudden death in symptomatic or asymptomatic individuals. Implantation of an automatic cardioverter-defibrillator is the only currently proven effective therapy. Patients with frequent electrical storms may even need cardiac transplantation as last resort.

Unusual form of AV nodal Wenckebach block.

A 73-year-old man had a fast atrioventricular (AV) nodal pathway accidentally ablated 4 years before, while attempting to ablate a septally located concealed accessory pathway (AP). After initiation of treatment with beta-blockers, because of systemic arterial hypertension, the patient presented to the emergency room complaining of a markedly diminished exercise tolerance. The 12 lead ECG showed an interesting AV nodal Wenckebach sequence, interrupted by P waves retrogradely conducted through the AP. The mechanisms explaining the ECG are discussed.

Mode switching failure during atrial flutter: the '2:1 lock-in' phenomenon.

AIMS: To evaluate incidence and mechanism of a special form of automatic mode switching (MS) failure in patients with atrial flutter. METHODS AND RESULTS: Retrospectively the charts of 134 patients implanted with dual chamber pacemakers with MS algorithms were reviewed. Seven patients (5.2%) were identified that presented with sustained rapid ventricular pacing resulting from atrial flutter with failure of automatic MS. Since this form of MS failure implies 2:1 tracking of atrial flutter, it was coined '2:1 lock-in'. A theoretical timing model was developed to clarify the mechanism of this special form of MS failure. Prerequisites for the '2:1 lock-in' phenomenon are: (1). the sum of the AV delay and the post ventricular blanking (PVAB) must be longer than the cycle length of the atrial flutter, (2). the tachycardia detection rate must be higher than half the atrial flutter rate and (3). the maximum tracking rate (MTR) must be higher than half the atrial flutter rate. Recommendations for programming in order to avoid this specific form of MS failure are made accordingly and parallel algorithms for flutter detection are discussed. CONCLUSION: '2:1 lock-in' is a typical form of MS failure in patients with atrial flutter and the mechanism is closely linked to the typical atrial sensing windows.