Fernando E.S. Cruz

Reversibility of tachycardia-induced cardiomyopathy after cure of incessant supraventricular tachycardia

Seven of 17 patients with incessant supraventricular tachycardia caused by an accessory pathway with a long retrograde conduction time were seen with symptoms or echocardiographic signs of a tachycardia-induced cardiomyopathy. Three patients were in New York Heart Association functional class II with dyspnea and four were in class III. Eight patients (six with tachycardia-induced cardiomyopathy) underwent surgery because of failure of medical treatment (including one patient in functional class I) and one underwent direct current catheter ablation of the atrioventricular (AV) node. In six patients echocardiograms recorded before and after the procedure were available. Before surgery or direct current ablation the mean left ventricular ejection fraction was 36.3 +/- 8.7%, the left ventricular end-diastolic diameter 55.7 +/- 7.6 mm and the left ventricular end-systolic diameter 44.3 +/- 7.8 mm. A mean of 21.6 +/- 6.8 months after the procedure the mean left ventricular ejection fraction increased to 58.6 +/- 8.0%, the left ventricular end-diastolic diameter decreased to 49.0 +/- 3.6 mm and the left ventricular end-systolic diameter decreased to 32.2 +/- 2.7 mm; all six patients were in functional class I. These results confirm that control of incessant tachycardia leads to a regression of symptoms and signs of cardiomyopathy and progressive normalization of the dimensions of the heart. Because of these findings, surgery should be considered early in patients with an accessory AV pathway and incessant tachycardia. The presence of a tachycardia-induced cardiomyopathy should therefore be an indication for surgery rather than a contraindication.

Clinical and electrophysiologic characteristics of patients with antidromic circus movement tachycardia in the Wolff-Parkinson-White syndrome

Antidromic circus movement tachycardia was documented in 36 of 345 consecutive patients with Wolff-Parkinson-White syndrome undergoing detailed electrophysiologic evaluation. Twenty-six patients were men and 10 were women (mean age +/- standard deviation 26 +/- 12 years [range 12 to 45]). Multiple accessory pathways were identified in 12 of these 36 patients (33%). Ten of the patients (67%) with clinically documented antidromic tachycardia had multiple accessory pathways. Dizziness and syncope occurred in 61 and 50% of patients with antidromic circus movement tachycardia. Six patients had clinical documentation of atrial fibrillation, and 4 patients (11%) were resuscitated from ventricular fibrillation. In the 36 patients, 56 distinct antidromic tachycardias were recorded and several different pathways were observed. Orthodromic tachycardia was the most frequently associated arrhythmia (72%). Dual atrioventricular nodal pathways were present in 12 patients (33%); however, atrioventricular nodal tachycardia could be initiated in only 2 of them. Interruption of the accessory pathway was successfully performed in all 20 patients undergoing surgery.

Longitudinal dissociation of atrioventricular accessory pathways

Unusual properties of atrioventricular (AV) accessory pathways were found during electrophysiologic investigations in four patients (three men and one woman). Anterograde longitudinal dissociation of the accessory pathway was observed in two patients and retrograde longitudinal dissociation in two others. Two patients had an accessory pathway with a slow conduction time, one in anterograde direction and one in retrograde direction. These observations further expand our knowledge of the spectrum of electrophysiologic properties of accessory AV pathways.

An Artificial Neural Network to Localize Atrioventricular Accessory Pathways in Patients Suffering from the Wolff‐Parkinson‐White Syndrome

DASSEN, W.R.M., ET AL. An Artificial Neural Network to Localize Atrioventricular Accessory Pathways in Patients Suffering from the Wolff‐Parkinson White Syndrome. The electrocardiographic localization of atrioventricular accessory pathways has been extensively described in the literature by a number of well‐known electrophysiologists and surgeons. These descriptions, often represented as decision trees, are useful, but do not apply in all cases. To formalize the process of determining the proper localization, this expert human knowledge could be represented in an expert system. But since reasoning is partly based on the use of heuristic knowledge, and are often not represented in the written description of the human expert, the results will be suboptimal. On the other hand, by using a self‐learning neural network approach, the causal relations between input (polarity of the delta waves) and output (the correct localization) do not have to be defined by the expert. It is derived by the neural network, by analyzing a learning set of cases consisting of the ECG plus the corresponding correct localization. In our set of 60 cases, 2 hours of training were required to learn how to localize all cases correctly. From a control set of 25 cases, 23 were interpreted by the system satisfactorily. Conclusion: the neural network approach can be useful in situations where causal relations between the electrocardiogram and underlying mechanism are partly undefined.

Self-learning neural networks in electrocardiography

The study described in this paper evaluated new tools for facilitating the development of criteria for ECG interpretation. Computer interpretation of the electrocardiogram (ECG) requires that numerous criteria related to diagnostic statements be defined. In the past, statistical techniques have been applied to derive and evaluate new criteria. More recently, some attempts have been made to incorporate artificial intelligence (AI) techniques such as expert systems in the computer interpretation of ECGs. In these systems the knowledge of the expert (facts, relations, heuristics) is stored in the knowledge base. With the help of the so-called inference engine this knowledge can be applied by a novice user. For instance, expert systems have been applied to improve arrhythmia detector performance in noise. ’ Such programs have also been used to evaluate the knowledge of human experts in determining the location of the accessory pathway in patients with Wolff-Parkinson-White syndrome.2 This study analyzed interpretation of guidelines given by five well respected authors for localization of the accessory pathway. The study demonstated that the information represented in these papers was incomplete, especially in regard to a frequent lack of heuristic information that distinguishes the expert from the novice user. In addition, the causal relationship between ECG measurements and the diagnosis was sometimes unknown.

Contribuição de eletrocardiografia dinâmica pelo sistema Holter na avaliação de pacientes com a síndrome congênita do QT longo

PURPOSE: The purpose of this study was to evaluate the value of ambulatory electrocardiogram as a clinical tool to assess ventricular repolarization in patients with the congenital long QT syndrome. METHODS: The study population comprised six patients and their data were compared to a control group of six patients matched in age and gender. The QT interval (ms), corrected by the heart rate, was measured in the first minute of each hour using two monitoring leads, with the mean of six consecutives complexes. The data obtained include the morphologic pattern of T wave, the mean 24-h QTc interval, relation between QT and cardiac cycle, QTc variability (assessed calculating hourly standard deviation of the interval and then obtaining the global 24-h mean), QTc dispersion (difference between the longest and shortest QTc interval). RESULTS: In all patients abnormal patterns of T waves were detected with frequent episodes of T wave alternans. Mean 24-h QTc - patients: 598.2±73.8ms; controls: 436.1±8.9ms (p=0.000). Linear correlation and regression between QT and heart rate - patients: r= 0.812; controls: r= 0.967 (p=0.000). QTc variability - patients: 36.9±17.2ms; controls: 14.7±2.1ms (p=0.01). QTc dispersion - patients: 168.3±70.2ms; controls: 53.3±8.1ms (p=0.000). CONCLUSION: The data showed increased hourly QTc variability, QTc dispersion and worse correlation between QT and heart rate. This data may reflect an abnormally augmented ventricular vulnerability.

Sudden death of athletes: a new fact?

Mailing address: Nabil Ghorayeb • Rua Safira, 326/181 Aclimacao 01532-010, Sao Paulo, SP Brazil E-mail: ghorayeb@cardiol.br; nghorayeb@terra.com.br Manuscript received October 07, 2007; revised manuscript received October 9, 2007; accepted October 9, 2007. A recurring theme, a phenomenon of globalized media, deja vu, no matter what terms are used to describe the sudden cardiac death of athletes, they tend to draw attention away from the main theme the seeming paradox of the sudden death of young and apparently healthy people in the course of professional or even amateur leisure sports activities.

Investigation of ion channel gene variants in patients with long QT syndrome

FUNDAMENTO: A sindrome do QT longo (SQTL) e uma sindrome arritmica herdada com aumento do intervalo QT e risco de morte subita. Mutacoes nos genes KCNQ1, KCNH2 e SCN5A respondem por 90% dos casos com genotipo determinado, e a genotipagem e informativa para aconselhamento genetico e melhor manejo da doenca. OBJETIVO: Investigacao molecular e analise computacional de variantes genicas de KCNQ1, KCNH2 e SCN5A associadas a SQTL em familias portadoras da doenca. METODOS: As regioes codificantes dos genes KCNQ1, KCNH2 e SCN5A de pacientes com SQTL e familiares foram sequenciadas e analisadas utilizando o software Geneious ProTM. RESULTADOS: Foram investigadas duas familias com criterios clinicos para SQTL. A probanda da Familia A apresentava QTC = 562 ms, Escore de Schwartz = 5,5. A genotipagem identificou a mutacao G1714A no gene KCNH2. Foi observado QTC = 521 ± 42 ms nos familiares portadores da mutacao contra QTC = 391 ± 21 ms de nao portadores. A probanda da Familia B apresentava QTc = 551 ms, Escore de Schwartz = 5. A genotipagem identificou a mutacao G1600T, no mesmo gene. A analise dos familiares revelou QTC = 497 ± 42 ms nos portadores da mutacao, contra QTC = 404 ± 29 ms nos nao portadores. CONCLUSAO: Foram encontradas duas variantes genicas previamente associadas a SQTL em duas familias com diagnostico clinico de SQTL. Em todos os familiares portadores das mutacoes foi observado o prolongamento do intervalo QT. Foi desenvolvida uma estrategia para identificacao de variantes dos genes KCNQ1, KCNH2 e SCN5A, possibilitando o treinamento de pessoal tecnico para futura aplicacao na rotina diagnostica.BACKGROUND The long QT syndrome (LQTS) is an inherited arrhythmia syndrome with increased QT interval and risk of sudden death. Mutations in genes KCNQ1, KCNH2 and SCN5A account for 90% of cases with genotype determined, and genotyping is informative for genetic counseling and better disease management. OBJECTIVE Molecular investigation and computational analysis of gene variants of KCNQ1, KCNH2 and SCN5A associated with LQTS, in families with the disease. METHODS The coding regions of genes KCNQ1, KCNH2 and SCN5A in patients with LQTS and their family members were sequenced and analyzed using Geneious ProTM software. RESULTS Two families with clinical criteria for LQTS were investigated. The proband of Family A had QTC = 562 ms, Schwartz Score = 5.5. The genotyping identified the G1714A mutation in the KCNH2 gene. QTC = 521 ± 42 ms was observed in family members carrying the mutation against QTC = 391 ± 21 ms for non-carriers. The proband of Family B had QTc = 551 ms, Schwartz Score = 5.5. The genotyping identified the G1600T mutation, in the same gene. The analysis of family members revealed QTC = 497 ± 42 ms in mutation carriers, compared with QTC = 404 ± 29 ms in non-carriers. CONCLUSION Two gene variants previously associated with LQTS were found in two families clinically diagnosed with LQTS. The prolongation of the QT interval was observed in all family members carrying the mutations. A strategy was developed to identify variants of genes KCNQ1, KCNH2 and SCN5A, making it possible to train technical staff for future application to diagnosis routine.

Radiofrequency catheter ablation of an incessant supraventricular tachycardia initiated by a Hisian parasystole.

The coexistence of a pamsystolic focus, tachycardia dependent right bundle branch aberrancy, and an AV accessory pathway is reported here. This condition was present in a 40‐year‐old man, which led to an incessant AV reciprocating tachycardia. Further electrophysiological study revealed that the parasystolic focus was located somewhere in the His bundle; endocardial mapping disclosed a right posterior accessory pathway. Radiofrequency current was delivered at the atrial level of the right posterolateral AV groove and successfully ablated the accessory pathway, leading to a dramatic improvement in cardiac function. In conclusion, the recognition of the electrophysiological mechanism of incessant Supraventricular tachycardia was of crucial importance for the therapy decision. A definitive intervention using radiofrequency catheter ablation should be considered early and not postponed in patients with tachycardia‐induced cardiomyopathy.

Prognostic value of junctional recovery times and long-time follow-up of complete atrioventricular nodal block at a young age

Abstract The main purpose of clinical and electrophysiologic investigation in patients having complete atrioventricular (AV) nodal block is to differentiate between 2 different heterogeneous groups 1 : one presenting with syncope or other bradycardia/tachycardia-related symptoms 2 and the asymptomatic group. The data available at the present time do not allow us to conclude which criteria is the best to distinguish the patient at risk for syncope in the latter group. Even when the site of block is in the proximal part of the His bundle 1 with a good response to parasympathetic blockade 3 or to exercise, 4 the junctional rhythm may not be stable enough, and Adam-Stokes attacks may occur. 5 Some investigators believe that life-expectancy in symptomatic patients can be good. 6 However, others have recognized that life-threatening arrhythmias may develop, 7 and a prophylactic pacemaker should be implanted. 8