The 'double transition': a novel electrocardiogram sign to discriminate posteroseptal accessory pathways ablated from the right endocardium from those requiring a left-sided or epicardial coronary venous approach.

AIMS: The precise localization of manifest posteroseptal accessory pathways (APs) often poses diagnostic challenges considering that a small area may encompass AP that may be ablated from the right or left endocardium, or epicardially within the coronary sinus (CS). We sought to explore whether the QRS transition pattern in the precordial lead may help to discriminate the necessary ablation approach. METHODS AND RESULTS: Consecutive patients who underwent a successful ablation of a single manifest AP over a 5-year period were included. Standard 12-lead electrocardiograms were reviewed. A total of 273 patients were identified. Mean age was 31 ± 15 years and 62% were male. Of the 110 identified posteroseptal AP, 64 were ablated from the right endocardium, 33 from the left endocardium, and 13 inside the CS. While a normal precordial QRS transition was most often observed, a subset of 33 patients presented an atypical 'double transition' pattern which specifically identified right endocardial AP. The combination of a q wave in V1 with a proportion of the positive QRS component in V1 < V2 > V3, predicted a right endocardial AP with a 100% specificity. In case of a positive QRS sum in V2, this 'double transition' pattern predicted a posteroseptal right endocardial AP with 99.5% specificity and 44% sensitivity. The positive predictive value was 97%. The only false positive was a midseptal AP. In the case of a negative or isoelectric QRS sum in V2, APs were located more laterally on the tricuspid annulus. CONCLUSION: The combination of a q wave in V1 with a double QRS transition pattern in the precordial leads is highly specific of a right endocardial AP and rules out the need for CS or left-sided mapping.

Diagnostic challenges of Brugada Syndrome in pediatric patients.

Although most cases of Brugada syndrome have been described in adults, pediatric patients with the disease have been reported since the original article from Josep and Pedro Brugada. Herein is presented the case series of Brugada syndrome in pediatric population of the National Institute of Cardiology Ignacio Chavez. One boy and two adolescent males had palpitations as clinical presentation of the disease. Atrial arrhythmias were documented in two, in the third case there was a high clinical suspicion and quinidine abolished symptoms. The aim of this report is to highlight the importance of performing a detailed clinical history as well as the usefulness of high precordial leads for the diagnosis of this entity.

POLYMORPHISMS IN ß-ADRENERGIC RECEPTORS ARE ASSOCIATED WITH INCREASED RISK TO HAVE A POSITIVE HEAD-UP TILT TABLE TEST IN PATIENTS WITH VASOVAGAL SYNCOPE.

BACKGROUND: Vasovagal syncope (VVS) is a frequent clinical condition in which a genetic background seems to be implicated. Considering that the adrenergic receptors (ARs) may play a role in VVS, the present study has as principal aim to determine if the α- and ß-AR (ADRA and ADRB) gene polymorphisms are associated with an increased risk to have a positive head-up tilt table (HUTT) test in patients with VVS. Methods: Nine polymorphisms in the ADRA1A (rs1048101, rs1383914, rs574584, and rs573542), ADRB1 (rs1801252 and rs1801253), ADRB2 (rs1042713 and rs1042714), and ADRB3 (rs4994) genes were analyzed using the 5' exonuclease TaqMan genotyping assay in a group of 134 patients with VVS. RESULTS: Under different models, the rs1801252 (OR = 8.63, 95% CI: 0.95-78.72, Precessive = 0.02), rs1042713 (OR = 1.94, 95% CI: 1.02-3.66, Padditive = 0.04), and rs4994 (OR = 2.46, 95% CI: 1.01-6.01, Pdominant = 0.042 and OR = 2.62, 95% CI: 1.04-6.63, Pover-dominant = 0.03) polymorphisms were associated with increased risk for a positive HUTT. All models were adjusted for statistically significant covariates. CONCLUSION: These results suggest that some polymorphisms of the ß-AR genes could contribute to a positive tilt test in patients with VVS.

Use of subcutaneous cardioverter-defibrillator. First cases reported from National Institute of Cardiology Ignacio Chávez-Mexico.

INTRODUCTION: The transvenous implantable cardioverter defibrillator (ICD) is the treatment of choice for the prevention of sudden cardiac death (SCD). Its use could be restricted when device-related infections occurs or in the pediatric population. In the later, an ICD represents a challenge, due to the minimal dimensions of the venous system in children, the length of the electrodes, the size of the generator, as well as the anatomical complexity in cases with associated congenital heart disease. OBJECTIVE: This article presents the first Mexican patients with a subcutaneous ICD (SC-ICD) implant as a therapy for the prevention of SCD. METHODS: The first four cases were implanted at the Ignacio Chávez National Institute of Cardiology with a SC-ICD (Emblem, Boston Scientific, USA), three of them were pediatric patients, including the first implant of this type of device in a pediatric patient in Latin America. The 3-incision and 2-incision techniques were used under general anesthesia. RESULTS: A successful implantation was obtained with the 3-incision technique in the first 2 cases and the last 2 with the 2-incision technique. Proper functioning of the device was corroborated in the operating room with proof of appropriate therapy (65 J) for ventricular fibrillation induced with 50 Hz stimulation. No immediate complications were observed. One patient had appropriate shocks two months after the implant. During follow-up, one child developed skin erosion at the level of the curve of the electrode on the sternum, with no signs of infection. In the operating room, the damaged skin was resected, the barrel and the fixation silk were removed, surgical lavage was performed, and the skin was closed again, thus avoiding removal of the system. CONCLUSIONS: The SC-ICD is an alternative therapy to the transvenous ICD. It can be considered first choice in subjects who do not require ventricular pacing, including pediatric patients. Skin complications can occur but do not pose a threat as venous complications of conventional ICDs.

INTRODUCCIÓN: El desfibrilador automático implantable (DAI) transvenoso es el tratamiento de elección para la prevención de muerte súbita (MS) cardiaca por arritmias ventriculares malignas. Su uso se puede ver limitado cuando existe infección del sistema de estimulación o en población pediátrica donde representa un reto por diversas razones, incluyendo: las mínimas dimensiones del sistema venoso de los niños, la longitud de los electrodos, el tamaño del generador, así como por la complejidad anatómica en casos de cardiopatía congénita asociada. OBJETIVO: El presente artículo tiene por objetivo presentar la primera serie de casos de pacientes mexicanos a los cuales se les implantó un DAI subcutáneo (DAI-SC) como terapia para la prevención de MS. MÉTODOS: Se presentan los cuatro primeros casos que fueron implantados en el Instituto Nacional de Cardiología Ignacio Chávez con un DAI-SC (Emblem, Boston Scientific, EE.UU.), tres de ellos eran pacientes pediátricos, incluyendo el primer implante de este tipo de dispositivo en un paciente pediátrico en América Latina. Las técnicas de tres y dos incisiones fueron empleadas bajo anestesia general. RESULTADOS: Se realizó el implante exitoso con técnica de tres incisiones en los dos primeros casos y con técnica de dos incisiones en los dos últimos casos. Se corroboró el adecuado funcionamiento del dispositivo en sala, con la verificación de terapia apropiada (65 J) de la fibrilación ventricular inducida mediante estimulación a 50 Hz. No hubo complicaciones inmediatas. Un paciente presentó descargas apropiadas a los dos meses del implante. En el seguimiento, un niño desarrolló erosión de la piel a nivel de la curva del electrodo en el esternón, sin datos de infección. En quirófano se resecó la piel dañada, se retiró el barril y la seda de fijación, se realizó lavado quirúrgico y se volvió a cerrar la piel, logrando así evitar el retiro del sistema. CONCLUSIONES: El DAI-SC es una terapia alternativa al DAI endovenoso y puede ser considerado de primera elección en aquellos casos que no requieran de estimulación ventricular, incluyendo pacientes pediátricos. Pueden ocurrir complicaciones cutáneas, pero no representan una amenaza como las complicaciones venosas de los DAI convencionales.

Validation of qrs-polarity algorithm with special emphasis in parahisian pathways.

BACKGROUND: In 1996 Iturralde et al. published an algorithm based on the QRS polarity to determine the location of the accessory pathways (AP), this algorithm was developed before the massive practice of invasive electrophysiology. PURPOSE: To validate the QRS-Polarity algorithm in a modern cohort of subjects submitted to radiofrequency catheter ablation (RFCA). Our objective was to determinate its global accuracy and its accuracy for parahisian AP. METHODS: We conducted a retrospective analysis of patients with Wolff-Parkinson-White (WPW) syndrome who underwent an electrophysiological study (EPS) and RFCA. We employed the QRS-Polarity algorithm to predict the AP anatomical location and we compared this result with the real anatomic location determined in the EPS. To determine accuracy, the Cohen's kappa coefficient (k) and the Pearson correlation coefficient were used. RESULTS: A total of 364 patients were included (mean age 30 years, 57% male). The global k score was 0.78 and the Pearson's coefficient was 0.90. The accuracy for each zone was also evaluated, the best correlation was for the left lateral AP (k of 0.97). There were 26 patients with a parahisian AP, who showed a great variability in the ECG features. Employing the QRS-Polarity algorithm, 34.6% patients had a correct anatomical location, 42.3% had an adjacent location and only 23% an incorrect location. CONCLUSION: The QRS-Polarity algorithm has a good global accuracy; its precision is high, especially for left lateral AP. This algorithm is also useful for the parahisian AP.

ANTECEDENTES: En 1996 Iturralde y colaboradores publicaron un algoritmo basado en la polaridad del QRS para determinar la ubicación de las vías accesorias (VA), este algoritmo fue desarrollado antes de la práctica masiva de la electrofisiología invasiva. OBJETIVO: Validar el algoritmo de la polaridad del QRS en una cohorte moderna de sujetos sometidos a ablación con catéter por radiofrecuencia (ACRF). Nuestro objetivo fue determinar su precisión global y su precisión para las VA parahisianas. MÉTODOS: Realizamos un análisis retrospectivo de pacientes con síndrome de Wolff-Parkinson-White (WPW) a los que se les realizó estudio electrofisiológico (EEF) y ACRF. Empleamos el algoritmo de la polaridad del QRS para predecir la ubicación anatómica de la VA y comparamos este resultado con la ubicación anatómica real determinada en el EEF. Para determinar la precisión se utilizaron el coeficiente kappa de Cohen (k) y el coeficiente de correlación de Pearson. RESULTADOS: Se incluyeron un total de 364 pacientes (edad media 30 años, 57 % varones). La puntuación k global fue de 0,78 y el coeficiente de Pearson de 0,90. También se evaluó la precisión para cada zona, la mejor correlación fue para las VA laterales izquierdas (k de 0.97). Hubo 26 pacientes con VA parahisianas, que mostraron una gran variabilidad en las características del ECG. Empleando el algoritmo de la polaridad del QRS, el 34,6 % de los pacientes tenía una ubicación anatómica correcta, el 42,3 % tenía una ubicación adyacente y solo el 23 % una ubicación incorrecta. CONCLUSIÓN: El algoritmo de la polaridad del QRS tiene una buena precisión global; su precisión es alta, especialmente para VA lateral izquierdo. Este algoritmo también es útil para la VA parahisiana.

Guide to identify specific characteristics in cardiac pacing devices by radiological figure.

This guide provides help for medical doctors systematically identifying each commercial brand of pacemakers by thoracic radiography through their electronic components (electrode connectors, logic circuit, and battery); this is crucial for watching the pacemaker after being implanted. We aimed to describe the different cardiac stimulation devices, electrodes, and programming modes more frequently used.

Esta guía propone brindar una ayuda a todos los médicos para la identificación metódica de cada marca comercial de marcapasos por radiografía simple de tórax, por medio de sus componentes electrónicos (conectores de electrodos, circuito lógico y batería), siendo necesario para la interrogación de dispositivos de marcapasos posterior a su implante. Se describirán los diferentes tipos de marcapasos, electrodos y modos de programación más frecuentemente utilizados.

Corrected sinus node recovery time as a screening test in patients with typical atrial flutter post-ablation to predict pacemaker implantation.

OBJECTIVE: The objective of the study was to establish the prognostic value of CSNRT regarding the necessity for pacemaker implantation in patients with atrial flutter (AFL) post-ablation. METHODS: This prospective cohort study, conducted at the National Institute of Cardiology "Ignacio Chavez" in Mexico City, assessed patients who had undergone ablation procedures to correct AFL, posterior to which an autonomic blockade was performed, and CSNRT was measured. RESULTS: The sample for this investigation was 40 patients. These were subdivided into two study groups depending on their requirement of pacemaker implant post-ablation (Pacemaker P, No Pacemaker NP). Sinus node (SN) dysfunction was diagnosed in 13 (32.5%) of the 40 participants, 10 (71.43%) of which required a pacemaker implant, while only 4 participants (28.57%) with normal SN function required pacemakers. Ten out of the 14 patients (71.43%) who required a pacemaker had an elevated CSNRT > 500 ms (p ≤ 0.01). Post-ablation CSNRT mean was 383.54 ms ± 67.96 ms in the NP group versus 1972.57 ms ± 3423.56 ms in the P group. Furthermore, SN pause in the P group had a mean of 1.86 s ± 0.96 s versus the NP group with 1.196 s ± 0.52 s. CONCLUSION: CSNRT has the potential to be a quantitative prognostic tool for the assessment of future pacemaker implants in patients with AFL post-ablation. This could aid in the timely diagnosis of sinus node dysfunction, which could, in the long run, result in the reduction of cardiac functional capacity loss due to cardiac remodeling.

OBJETIVO: Establecer el valor pronóstico del TRNSC basado en la necesidad de marcapasos en pacientes diagnosticados con aleteo atrial, pos-ablación. MÉTODOS: Este cohorte prospectivo, realizado en el Instituto Nacional de Cardiología "Ignacio Chávez" en la Ciudad de México, evaluó pacientes sometidos a ablación para corregir el aleteo atrial; se midió el TRNSC post bloqueo autonómico. RESULTADOS: La muestra de 40 pacientes se subdividió en 2 grupos según su requerimiento de marcapasos posterior a la ablación (P y NP). Se diagnosticó disfunción del nodo sinusal en 13 participantes (32.5%), de los cuales 10 (71.43%) requirieron marcapasos en comparación a 4 (28.57%) con función normal. En el grupo P la pausa del nodo sinusal post-ablación tuvo una media de 1.86 ± 0.96 s versus el grupo NP con 1.196 ± 0.52 s. En relación con el TRNSC, el grupo NP tuvo una media de 383.54 ± 67.96 ms vs. 1972.57 ± 3423.56 ms en el grupo P. 10 pacientes (25%) obtuvieron un TRNSC > 500 ms, de los cuales 100% requirieron marcapasos; de los 14 pacientes que requirieron marcapasos 10 (71.43%) tenían un TRNSC elevado (p ≤ 0.01). CONCLUSIONES: El TRNSC tiene el potencial de ser una herramienta de pronóstico cuantitativo para la necesidad de futuros implantes de marcapasos en pacientes con disfunción del nodo sinusal, resultado de aleteo atrial pos-ablación. Esto podría ayudar a diagnosticar más temprano una disfunción del nodo sinusal, resultando en la reducción de la pérdida a largo plazo de la función cardíaca como efecto de la remodelación.

[Left bundle branch stimulation in diffuse electrical heart disease in a pediatric patient]. / Estimulación de rama izquierda en enfermedad eléctrica difusa cardiaca en una paciente pediátrica.

Left bundle branch stimulation is a second-line strategy in patients where His bundle stimulation is not optimal. Currently, no cases of left bundle branch stimulation have been reported in patients with diffuse electrical cardiac disease or in the pediatric population.

Acute and long-term success of ventricular tachycardia ablation in patients with ischemic heart disease in a Mexican center.

Objective: . To report the results of ventricular tachycardia (VT) catheter ablation in ischemic heart disease (IHD), and to identify risk factors associated with recurrence in a Mexican center. Materials and methods: . We made a retrospective review of the cases of VT ablation performed in our center from 2015 to 2022. We analyzed the characteristics of the patients and those of the procedures separately and we determined factors associated with recurrence. Results: . Fifty procedures were performed in 38 patients (84% male; mean age 58.1 years). Acute success rate was 82%, with a 28% of recurrences. Female sex (OR 3.33, IC 95% 1.66-6.68, p=0.006), atrial fibrillation (OR 3.5, IC 95% 2.08-5.9, p=0.012), electrical storm (OR 2.4, IC 95% 1.06-5.41, p=0.045), functional class greater than II (OR 2.86, IC 95% 1.34-6.10, p=0.018) were risk factors for recurrence and the presence of clinical VT at the time of ablation (OR 0.29, IC 95% 0.12-0.70, p=0.004) and the use of more than 2 techniques for mapping (OR 0.64, IC 95% 0.48-0.86, p=0.013) were protective factors. Conclusions: . Ablation of ventricular tachycardia in ischemic heart disease has had good results in our center. The recurrence is similar to that reported by other authors and there are some factors associated with it.

Impact of the coronavirus disease-19 pandemic on electrophysiological procedures at a national referral center.

INTRODUCTION: The coronavirus disease (COVID-19) pandemic has generated serious repercussions on the health system, reducing the number of all cardiology procedures worldwide. OBJECTIVES: Describe the impact of the COVID-19 pandemic on the procedures performed by the electrophysiology department in a national referral center. METHODS: We made a retrospective review of our data base and we compared procedures made in the past 3 years since 2017-2019 with the procedures made in the 2020. We divided the procedures into two large groups: Cardiac Implantable Electronic Devices (CIED) related procedures and electrophysiological procedures (EP) which included conventional and complex ablations. RESULTS: There was a significant reduction in all the procedures, the average of procedures performed in the last 3 previous years was 467, while in 2020, we performed only 319 (p = 0.01); this represents a reduction of 33.4% in the total number of procedures. There was no statistical difference regarding the CIED related procedures, the average of procedures in the past 3 previous years was 174, and in 2020 we performed 190 procedures (p = 0.46). Regarding the EP, the average of the past 3 previous years was 293, while in 2020, we performed only 129 procedures (p < 0.01). The reduction in the EP was 55.97%. The most affected months were April, May, and June. CONCLUSIONS: The COVID-19 pandemic considerably affected the number of the procedures in our center, reducing it by 33.4%. The reduction of procedures fundamentally affected the ablations, with a reduction of 55.97%. The number of CIED related procedures was not affected.

[Management of heart failure with His bundle pacing in right bundle branch block: case report]. / Manejo de la insuficiencia cardiaca con estimulación hisiana en bloqueo de rama derecha: reporte de caso.

La terapia de resincronización cardiaca mediante estimulación hisiana ha demostrado ser efectiva en pacientes con bloqueo de rama izquierda del haz de His e insuficiencia cardiaca. Paciente masculino, con 47 años de edad, con insuficiencia cardiaca, fracción de expulsión del 17% y miocardio dilatada idiopática, electrocardiograma en ritmo sinusal, bloqueo auriculoventricular de 1.er grado, intervalo PR 400 ms, bloqueo completo de rama derecha del haz de His, bloqueo del fascículo anterior de la rama izquierda del haz de His, duración del QRS 200 ms. Se decidió realizar estimulación selectiva del haz de His. La resincronización cardiaca biventricular convencional en pacientes con presencia de bloqueo completo de la rama derecha del haz de His no está indicada debido a la pobre respuesta al tratamiento. La estimulación hisiana permite reclutar la rama bloqueada y reestablecer la conducción a través de ella, de tal forma que, en ausencia de necrosis, se logre sincronía biventricular. En el caso presentado el reclutamiento de la rama derecha mediante estimulación hisiana se reflejó en el restablecimiento de la sincronía biventricular, medida por rastreo de marcas (speckle tracking) e incremento significativo de la fracción de expulsión del ventrículo izquierdo del 17 al 36.6%, con un incremento absoluto del 19.6%.Cardiac resynchronization therapy has proven to be an effective therapy in patients with left bundle branch block and heart failure. Male, 47 years old, heart failure with a left ventricle ejection fraction of 17%, idiopathic heart failure. ECG with sinus rhythm, 1st degree AV block, PR 400 ms, complete right bundle branch block, anterior hemi-fascicle of the left bundle of His, and QRS duration 200 ms. We decided to perform a selective His bundle pacing. In patients with right bundle branch block the biventricular cardiac resynchronization is not indicated due to low treatment response. His bundle pacing allows recruiting the blocked branch and restoring conduction throughout it, therefore, in the absence of necrosis the biventricular synchrony is achieved. We presented a case of His bundle pacing with recruitment of the right bundle branch, which reestablish biventricular synchrony measured by speckle tracking, and with a significant increase of the left ventricle ejection fraction from 17 to 36.6%, with an absolute increase of 19.6%.

Cardioinhibitory syncope: from pathophysiology to treatment-should we think on cardioneuroablation?

Vasovagal syncope (VVS) is the most common type of syncope; the lone cardioinhibitory syncope represents only a small group of patients; however, the "cardioinhibitory component" is highly prevalent in reflex syncope and can be severe enough to produce asystole, lasting for a few seconds followed by a recovery to sinus beats. The environment in which syncope occurs can compromise life, and in-depth knowledge of the disease can prevent deaths and guide the appropriate management. The therapeutic cornerstone is general measures (increase water and salt) followed by pharmacologic therapy; for cardioinhibitory syncope, both treatments fail most of the time, and the next therapeutic option is pacemaker implantation. However, although the pacemaker causes a reduction in syncope, recurrence is high, and a one-time, effective, and safe intervention would be ideal. Cardioneuroablation (CNA) therapy has been proposed as a pacemaker alternative with these characteristics. CNA has shown a high reduction or even complete syncope elimination during 3 years of follow-up in some studies. Patients also reported prolonged prodromal periods, which allowed them enough time to abort the syncope. Invasive therapies like CNA require further extensive cohort studies, randomized clinical trials, and more substantial follow-up to evaluate adverse side effects. This review highlights syncope pathophysiology, dividing it into a central theory and a peripheral theory, the diagnosis explaining the head-up tilt test protocols, and treatments like CAN, representing it with figures for a simplified understanding.

[Electroanatomic mapping and radiofrequency catheter ablation of focal atrial tachycardias]. / Ablación con catéter de las taquicardias auriculares focales guiada por mapeo electroanatómico.

Focal atrial tachycardia is defined as supraventricular tachycardia originating from discrete sites from which activation spreads to both atrial. In most clinical series, atrial tachycardia account for about 5% of all supraventricular arrythmias. This tachycardia can occur in children or adults within and without structural heart disease. Three potential mechanisms are described for its origin: abnormal automaticity, triggered activity or microreentry. Catheter ablation has an important role in the management of focal atrial tachycardia and is now considered to be a first line therapy, can be improved with electroanatomical mapping system (CARTO) that allows reconstruction of the chamber geometry and allow visualization of the activation sequence; and can to improve the efficacy of catheter ablation.

[Recent advances in the pathophysiology of atrial fibrillation]. / Avances recientes en la fisiopatología de la fibrilación auricular.

This review is a summary of the pathophysiology of atrial fibrillation (AF) and the progress in the understanding of this arrhythmia. The following factors should be considered in the genesis and maintenance of AF. The genetic factor is involved in cases of familial AF. Predisposing structural factors: atrial dilation, structural feature that allows the development of AF. Predisposing structural factors: the role of the Bachmann's bundle and frequency gradients between the left and right atrium. Electrophysiological factors: heterogeneous refractory periods favor the fibrillatory conduction. Triggers: abnormal electrical activity (ectopic foci). Modulating factors: autonomic nervous system. Increased vagal tone shortens atrial refractory periods, creating a greater dispersion of the refractory periods and the generation of reentries in the context of triggered activity. Finally, there are three types of atrial remodeling secondary to AF: structural, contractile, electrical. They are interrelated and contribute to maintaining the AF ("AF begets AF").

[Clinical predictors of ventricular arrhythmia storms in Chagas cardiomyopathy patients with implantable defibrillators]. / Predictores clínicos de tormenta arrítmica en pacientes con cardiomiopatía Chagásica con un desfibrilador automático implantable.

OBJECTIVES: To define the predictive factors of electrical storm (ES) in patients with Chronic Chagas Heart Disease (CCh) with an implantable cardioverter defibrillator (ICD). MATERIAL AND METHODS: We retrospectively studied 21 consecutive patients with CCh in whom an ICD was implanted between April 2005 and December 2008, with a mean follow up of 867 days. Patients were classified into two groups according to the presence of electrical storm episodes. We compared baseline characteristics, medical treatment and determinants of ventricular function. P values less than 0.05 were considered statistically significant. RESULTS: Of the 21 patients with CCh there were eight women (37%), mean age 61 years and an EF of 30%. It was noted at least one episode of arrhythmic storm in 9 cases (incidence of 43%). The total number of episodes of arrhythmic storm was 13 and the number of ventricular arrhythmias in each episode of arrhythmic storm was 15.6 (range 3-61). A trigger was identified in only two cases (pulmonary infectious process and decompensation of chronic heart failure). After analyzing the possible predictors of arrhythmic storm was found that a greater percentage of subjects with this complication had an EF <35% (89% vs. 50%, p = 0.01) and NYHA functional class III (66% vs. 8.3%, p = 0.001). In contrast, a lower percentage of subjects with arrhythmic storm were under beta-blocker treatment (55% vs. 100%, p = 0.01). CONCLUSIONS: In subjects with CCh with an ICD, the following variables are predictive of arrhythmic storm: EF <35%, NYHA functional class III-IV and absence of beta-blocker treatment.

[Case report: idiopathic ventricular tachycardia from the aortic sinus cusp]. / Informe de un caso: taquicardia ventricular idiopática en el seno de Valsalva izquierdo.

Idiopathic ventricular tachycardia is identified in 10% of the patients presenting with ventricular tachycardia, and they consist of various subtypes that can originate from different areas, including the aortic cusps which represent 0.7% of the total. Electrocardiographically, these ventricular tachycardias display a left bundle branch block pattern and inferior axis, and although rare, should be considered in the differential diagnosis with tachycardias originating from the septal region of the right ventricular outflow tract, which comprise 80% of the idiopathic ventricular tachycardias. Despite the vicinity of the left coronary artery ostium, radiofrequency catheter ablation can be curative in more than 90% of cases with a low risk (< 1% of serious complication). Therefore, it must be considered first-line therapy in patients who have failed or are intolerant to therapy with antiarrhythmic agents. The aim of this article is to describe the first case reported in Mexico of a successful ablation idiopathic ventricular tachycardia from the aortic sinus cusp in a patient with incessant ventricular tachycardia.

Association of congenital, diffuse electrical disease in children with normal heart: sick sinus syndrome, intraventricular conduction block, and monomorphic ventricular tachycardia.

INTRODUCTION: Rhythm disturbances in children with structurally normal hearts are usually associated with abnormalities in cardiac ion channels. The phenotypic expression of these abnormalities ("channelopathies") includes: long and short QT syndromes, Brugada syndrome, congenital sick sinus syndrome, catecholaminergic polymorphic ventricular tachycardia, Lènegre-Lev disease, and/or different degrees of cardiac conduction disease. METHODS: The study group consisted of three male patients with sick sinus syndrome, intraventricular conduction disease, and monomorphic sustained ventricular tachycardia. Clinical data and results of electrocardiography, Holter monitoring, electrophysiology, and echocardiography are described. RESULTS: In all patients, the ECG during sinus rhythm showed right bundle branch block and long QT intervals. First-degree AV block was documented in two subjects, and J point elevation in one. A pacemaker was implanted in all cases due to symptomatic bradycardia (sick sinus syndrome). Atrial tachyarryhthmias were observed in two patients. The common characteristic ventricular arrhythmia was a monomorphic sustained ventricular tachycardia, inducible with ventricular stimulation and sensitive to lidocaine. In one patient, radiofrequency catheter ablation was successfully performed. No structural abnormalities were found in echocardiography in the study group. CONCLUSION: Common clinical and ECG features suggest a common pathophysiology in this group of patients with congenital severe electrical disease.

[Comparison of metoprolol vs clonazepam as a first treatment choice among patients with neurocardiogenic syncope]. / Comparación de metoprolol versus clonazepam como tratamiento de primera intención en pacientes con síncope neurocardiogénico.

OBJECTIVE: We compared the effects of a metoprolol and clonazepam in patients with neurocardiogenic syncope. METHODS: We compared the effects of a metoprolol and clonazepam in a prospective, randomised trial in 54 patients. Patients were randomly assigned to metoprolol (starting dose 50 mg bid) or clonazepam (starting dose 0.5 mg qd). We assessed a primary combined endpoint of syncope and pre-syncope on a follow-up of 12 months. RESULTS: The primary combined endpoint of syncope and presyncope occurred in the metoprolol group in 3, 4, and 10% of patients at 3, 6, and 12 months respectively. In the clonazepam group it was no recurrence in the first 6 months, and 5% recurrence at 12 months follow-up (nonsignificant differences between groups). Clinical symptoms commonly associated with neurally mediated syncope were decreased similarly in both treatment groups, in the metoprolol group from 5.2+/-2.5 to 1.9+/-2.1 (p < 0.001) and in the clonazepam group from 5.5+/-2.5 to 1.5+/-2.2 (p<0.001). CONCLUSIONS: Pharmacological treatment of neurocardiogenic syncope with metoprolol or clonazepam resulted in similar prevention of syncope and presyncope. Both treatments decreased clinical symptoms but complete symptomatic resolution was rarely observed.

Validation of qrs-polarity algorithm with special emphasis in parahisian pathways / Validación del algoritmo de la polaridad del qrs con especial énfasis en vías parahisianas

Abstract Background: In 1996 Iturralde et al. published an algorithm based on the QRS polarity to determine the location of the accessory pathways (AP), this algorithm was developed before the massive practice of invasive electrophysiology. Purpose: To validate the QRS-Polarity algorithm in a modern cohort of subjects submitted to radiofrequency catheter ablation (RFCA). Our objective was to determinate its global accuracy and its accuracy for parahisian AP. Methods: We conducted a retrospective analysis of patients with Wolff-Parkinson-White (WPW) syndrome who underwent an electrophysiological study (EPS) and RFCA. We employed the QRS-Polarity algorithm to predict the AP anatomical location and we compared this result with the real anatomic location determined in the EPS. To determine accuracy, the Cohen's kappa coefficient (k) and the Pearson correlation coefficient were used. Results: A total of 364 patients were included (mean age 30 years, 57% male). The global k score was 0.78 and the Pearson's coefficient was 0.90. The accuracy for each zone was also evaluated, the best correlation was for the left lateral AP (k of 0.97). There were 26 patients with a parahisian AP, who showed a great variability in the ECG features. Employing the QRS-Polarity algorithm, 34.6% patients had a correct anatomical location, 42.3% had an adjacent location and only 23% an incorrect location. Conclusion: The QRS-Polarity algorithm has a good global accuracy; its precision is high, especially for left lateral AP. This algorithm is also useful for the parahisian AP.

Resumen Antecedentes: En 1996 Iturralde y colaboradores publicaron un algoritmo basado en la polaridad del QRS para determinar la ubicación de las vías accesorias (VA), este algoritmo fue desarrollado antes de la práctica masiva de la electrofisiología invasiva. Objetivo: Validar el algoritmo de la polaridad del QRS en una cohorte moderna de sujetos sometidos a ablación con catéter por radiofrecuencia (ACRF). Nuestro objetivo fue determinar su precisión global y su precisión para las VA parahisianas. Métodos: Realizamos un análisis retrospectivo de pacientes con síndrome de Wolff-Parkinson-White (WPW) a los que se les realizó estudio electrofisiológico (EEF) y ACRF. Empleamos el algoritmo de la polaridad del QRS para predecir la ubicación anatómica de la VA y comparamos este resultado con la ubicación anatómica real determinada en el EEF. Para determinar la precisión se utilizaron el coeficiente kappa de Cohen (k) y el coeficiente de correlación de Pearson. Resultados: Se incluyeron un total de 364 pacientes (edad media 30 años, 57 % varones). La puntuación k global fue de 0,78 y el coeficiente de Pearson de 0,90. También se evaluó la precisión para cada zona, la mejor correlación fue para las VA laterales izquierdas (k de 0.97). Hubo 26 pacientes con VA parahisianas, que mostraron una gran variabilidad en las características del ECG. Empleando el algoritmo de la polaridad del QRS, el 34,6 % de los pacientes tenía una ubicación anatómica correcta, el 42,3 % tenía una ubicación adyacente y solo el 23 % una ubicación incorrecta. Conclusión: El algoritmo de la polaridad del QRS tiene una buena precisión global; su precisión es alta, especialmente para VA lateral izquierdo. Este algoritmo también es útil para la VA parahisiana.

Desfibrilador subcutáneo. Primeros casos en el Instituto Nacional de Cardiología, incluyendo dos pacientes pediátricos / Use of subcutaneous cardioverter-defibrillator. First cases reported from National Institute of Cardiology Ignacio Chávez-Mexico

Resumen Introducción: El desfibrilador automático implantable (DAI) transvenoso es el tratamiento de elección para la prevención de muerte súbita (MS) cardiaca por arritmias ventriculares malignas. Su uso se puede ver limitado cuando existe infección del sistema de estimulación o en población pediátrica donde representa un reto por diversas razones, incluyendo: las mínimas dimensiones del sistema venoso de los niños, la longitud de los electrodos, el tamaño del generador, así como por la complejidad anatómica en casos de cardiopatía congénita asociada. Objetivo: El presente artículo tiene por objetivo presentar la primera serie de casos de pacientes mexicanos a los cuales se les implantó un DAI subcutáneo (DAI-SC) como terapia para la prevención de MS. Métodos: Se presentan los cuatro primeros casos que fueron implantados en el Instituto Nacional de Cardiología Ignacio Chávez con un DAI-SC (Emblem, Boston Scientific, EE.UU.), tres de ellos eran pacientes pediátricos, incluyendo el primer implante de este tipo de dispositivo en un paciente pediátrico en América Latina. Las técnicas de tres y dos incisiones fueron empleadas bajo anestesia general. Resultados: Se realizó el implante exitoso con técnica de tres incisiones en los dos primeros casos y con técnica de dos incisiones en los dos últimos casos. Se corroboró el adecuado funcionamiento del dispositivo en sala, con la verificación de terapia apropiada (65 J) de la fibrilación ventricular inducida mediante estimulación a 50 Hz. No hubo complicaciones inmediatas. Un paciente presentó descargas apropiadas a los dos meses del implante. En el seguimiento, un niño desarrolló erosión de la piel a nivel de la curva del electrodo en el esternón, sin datos de infección. En quirófano se resecó la piel dañada, se retiró el barril y la seda de fijación, se realizó lavado quirúrgico y se volvió a cerrar la piel, logrando así evitar el retiro del sistema. Conclusiones: El DAI-SC es una terapia alternativa al DAI endovenoso y puede ser considerado de primera elección en aquellos casos que no requieran de estimulación ventricular, incluyendo pacientes pediátricos. Pueden ocurrir complicaciones cutáneas, pero no representan una amenaza como las complicaciones venosas de los DAI convencionales.

Abstract Introduction: The transvenous implantable cardioverter defibrillator (ICD) is the treatment of choice for the prevention of sudden cardiac death (SCD). Its use could be restricted when device-related infections occurs or in the pediatric population. In the later, an ICD represents a challenge, due to the minimal dimensions of the venous system in children, the length of the electrodes, the size of the generator, as well as the anatomical complexity in cases with associated congenital heart disease. Objective: This article presents the first Mexican patients with a subcutaneous ICD (SC-ICD) implant as a therapy for the prevention of SCD. Methods: The first four cases were implanted at the Ignacio Chávez National Institute of Cardiology with a SC-ICD (Emblem, Boston Scientific, USA), three of them were pediatric patients, including the first implant of this type of device in a pediatric patient in Latin America. The 3-incision and 2-incision techniques were used under general anesthesia. Results: A successful implantation was obtained with the 3-incision technique in the first 2 cases and the last 2 with the 2-incision technique. Proper functioning of the device was corroborated in the operating room with proof of appropriate therapy (65 J) for ventricular fibrillation induced with 50 Hz stimulation. No immediate complications were observed. One patient had appropriate shocks two months after the implant. During follow-up, one child developed skin erosion at the level of the curve of the electrode on the sternum, with no signs of infection. In the operating room, the damaged skin was resected, the barrel and the fixation silk were removed, surgical lavage was performed, and the skin was closed again, thus avoiding removal of the system. Conclusions: The SC-ICD is an alternative therapy to the transvenous ICD. It can be considered first choice in subjects who do not require ventricular pacing, including pediatric patients. Skin complications can occur but do not pose a threat as venous complications of conventional ICDs.