Cardiac electrophysiologic procedures - A ten years' experience at National Institute of Cardiovascular Diseases, Karachi.

OBJECTIVE: To review 10 years of clinical practice of cardiac electrophysiology study and radiofrequency catheter ablation in the treatment of supraventricular tachycardia. METHODS: The retrospective chart review was conducted at the National Institute of Cardiovascular Diseases, Karachi, and comprised records of all patients who underwent electrophysiological study and / or radiofrequency catheter ablation from January2007 to December 2016. SPSS 21 was used for data analysis. RESULTS: Of the 627 patients, 335(53.4%) were females. The overall mean age was 40.99}13.59 years. The major indication for procedure was supraventricular tachycardia 376(59.97%). Final electrophysiological study diagnosis was typical slow fast atrioventricular nodal re-entrant tachycardia in 303(48.3%) patients. The overall success rate was 472(75.3%). Procedure-related complications were reported in 25(4%) patients, and there was 1(0.15%) mortality. CONCLUSIONS: Cardiac electrophysiology studies and radiofrequency catheter ablation were found to be an effective and safe method for diagnosis and treatment of supraventricular tachycardia.

Ablación con catéter no guiada por fluoroscopia. Resultados de un registro prospectivo multicéntrico / Nonfluoroscopic catheter ablation. results from a prospective multicenter registry

Introducción y objetivos: La ablación con catéter sin guía fluoroscópica es factible en la mayoría de los casos. El objetivo de nuestro registro es evaluar la factibilidad y la seguridad de la ablación no guiada por fluoroscopia en varios centros españoles. Métodos: Once hospitales incluyeron prospectivamente a, al menos, 20 pacientes afectados de un sustrato arrítmico cuyo procedimiento de ablación, a juicio de cada operador, se podía abordar sin fluoroscopia durante todo el procedimiento. No se incluyó a pacientes portadores de dispositivos intracardiacos. Electrofisiólogos de plantilla, becarios y residentes participaron en cada procedimiento de forma habitual. Resultados: Se incluyó a un total de 247 pacientes (n = 247). Se realizó ablación en 235 casos (95,2%), y en 2 casos que no se incluyeron en el análisis la fluoroscopia se utilizó como primera intención. En el 99,15% (231/233) de los procedimientos analizados el sustrato arrítmico abordado se localizaba en cavidades derechas. Se requirió fluoroscopia en 24 (10,3%), se obtuvo éxito en el 96,4% de los procedimientos y hubo complicaciones graves en 2 pacientes (0,85%). Las variables relacionadas con la necesidad de fluoroscopia fueron el centro realizador (máximo, 33,3%; mínimo, 0; p = 0,001) y el fracaso del procedimiento (el 13 frente al 2,4%; p < 0,05). Conclusiones: El registro multicéntrico muestra que la ablación sin escopia de sustratos localizados en cavidades derechas es factible en la mayoría de los procedimientos. Se necesitan estudios aleatorizados para confirmar su seguridad. La necesidad de fluoroscopia es mayor en los procedimientos sin éxito y es variable en los centros realizadores (AU)

Introduction and objectives: Nonfluoroscopic catheter ablation is feasible in most procedures. The aim of our registry was to evaluate the safety and feasibility of a zero-fluoroscopic approach to catheter ablation in several Spanish centers. Methods: Eleven centers prospectively included a minimum of 20 patients. Patients with an arrhythmic substrate deemed suitable by the operator for a zero-fluoroscopic approach throughout the procedure were recruited. Patients with intracardiac devices were not included. Attending electrophysiologists, fellows, and resident physicians participated in each procedure, as in usual care. Results: The study included 247 patients. Ablation was performed in 235 patients (95.2%). In 2 patients, who were not included in the analysis, fluoroscopy was performed as the first-line treatment. The arrhythmic substrate was located in the right chambers in most of the procedures (231 of 233 [99.15%]). Fluoroscopy was used in 24 procedures (10.3%). Catheter ablation was successful in 96.4% of the procedures and severe complications occurred in 2 patients (0.85%). Two variables were related to the need for fluoroscopy: the performing center (minimum 0% vs maximum 30.3%; P = .001) and procedural failure (13% vs 2.4%; P < .05). Conclusions: The Spanish multicenter registry reveals that a zero-fluoroscopic approach is feasible in most right-sided catheter ablation procedures. Randomized trials are necessary to confirm the safety of this approach. The need for fluoroscopy was related to procedural failure, with significant differences among performing centers (AU)

Pathophysiology of ventricular tachyarrhythmias : From automaticity to reentry.

Ventricular arrhythmias are a heterogeneous group of arrhythmias and may arise in patients with cardiomyopathy or structurally normal hearts. The electrophysiologic mechanisms responsible for the initiation and maintenance of ventricular tachycardia include enhanced automaticity, triggered activity, and reentry. Differentiating between these three mechanisms can be challenging and usually requires an invasive electrophysiology study. Establishing the underlying mechanism in a particular patient is helpful to define the optimal therapeutic approach, including the selection of pharmacologic agents or delineation of an ablation strategy.

Number needed to entrain: a new criterion for entrainment mapping in patients with intra-atrial reentrant tachycardia.

BACKGROUND: Measuring postpacing intervals (PPIs) is the standard maneuver for localizing reentrant tachycardia circuits. However, changes or termination of the tachycardia during entrainment pacing, or difficulties in defining the correct local activity, limit the use of PPIs. METHODS AND RESULTS: We hypothesized that the number of pacing stimuli needed to entrain (NNE) was useful for mapping intra-atrial reentrant tachycardias. First, 10 patients with typical atrial flutter were studied to characterize the NNE. Next, 317 entrainment attempts in 30 patients with 76 intra-atrial reentrant tachycardias were analyzed to determine the efficacy of the NNE. The NNE was small at sites within the reentrant circuit (median 2) and large at remote sites during typical atrial flutter. The NNE depended on the pacing cycle length and coupling interval of the initial paced beat, where the NNE became smaller at shorter pacing cycle lengths and coupling intervals. The NNE highly correlated with the difference between the PPI and tachycardia cycle length (r = 0.906; P<0.001). When the pacing cycle length and coupling interval were 16 to 30 ms below the tachycardia cycle length, a NNE ≤2 and >3 predicted a PPI-tachycardia cycle length ≤20 and >20 ms, respectively, with 100% accuracy. Thirty-six (11%) entrainment attempts changed or terminated intra-atrial reentrant tachycardia. Importantly, the NNE remained valid in those cases. Furthermore, the NNE provided additional information in cases with some difficulties with PPI measurements. CONCLUSIONS: The NNE is a simple and reliable criterion, which facilitates mapping intra-atrial reentrant tachycardia. CLINICAL TRIAL REGISTRATION URL: http://www.clinicaltrials.gov. Unique identifier: NCT001747.

An anterior ablation line is preferred for perimitral flutter after heart transplant.

Perimitral atrial flutter in cardiac allograft recipients is uncommon. In general, mitral isthmus ablation can be quite challenging in all patients with perimitral flutter, including the subset of patients who present following left atrial ablation for atrial fibrillation. We report 2 cases where an anterior ablation line was easily performed to eliminate perimitral flutter and produce bidirectional block.

Suppression of intra-atrial reentrant tachycardia in patients with atrial overdrive pacing.

BACKGROUND: Intra-atrial reentrant tachycardia (IART) is a common arrhythmia in adult patients with palliated congenital heart disease (CHD). Traditional treatment methods such as antiarrhythmic drugs (AADs) or radiofrequency ablation are often unsuccessful or cause side effects. These patients often require frequent cardioversion and anticoagulation. The purpose of this study is to evaluate the success of overdrive atrial pacing for the suppression of IART in CHD. METHODS: Single center, investigational review board approved, retrospective review of nine patients with CHD and documented, recurrent IART. Patients served as their own historical controls for this study. Phase I was defined as the period 2 years prior to atrial pacing intervention, and Phase II was defined as > or =13 months with atrial pacing; enabled or implanted rate responsive or dynamic overdrive A pacing. During Phase II, the patients' rhythm was monitored by either symptom reporting, ECG, Holter monitoring or pacer diagnostics every 2 months. RESULTS: Cardioversion post A pacing decreased: from 25 to 3, P < .003, patients requiring cardioversions 9 to 1, P < .001, no. AADs 18 to 7, P < .02. CONCLUSIONS: Overdrive atrial pacing, > or =70 ppm, is a viable treatment option to suppress recurrent IART. With the suppression of IART, the need for cardioversion, and AAD can be significantly reduced.

Ablación de la taquicardia intranodal: cuando la fisiología cuenta en la era de la anatomía / Intranodal tachycardia ablation: when physiology is important in the era of anatomy

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Experimental ablation study using a new long linear probe in isolated porcine hearts.

We studied a new technique for creating long linear lesions in hearts using a custom-made linear probe. Radiofrequency (RF) energy applications using a 25-mm long stainless steel linear probe and a corresponding 500-kHz energy generator were tested, creating 90 lesions in isolated porcine hearts. The RF current was applied between the linear probe and a large patch electrode attached to the back of the specimen. Three parameters, comprising the power of the delivered energy, the pressure of contact between the probe and the specimen, and the duration of energy delivery were changed independently and the size of the resulting lesions was measured. All 90 lesions were transmural, well demarcated and created by a single stationary RF application. Lesion length and width increased with: 1) increasing power, when the other two parameters were maintained at constant levels, 2) increasing contact pressure, when the other two parameters were maintained at constant levels, and 3) increasing duration of energy delivery when the other two parameters were maintained at constant levels. The maximum width of the lesions was 3.7 mm. No overheating of any of the specimens was observed. In conclusion, the new original long linear probe used in this study was effective for creating transmural linear lesions, presenting the possibility of a worthwhile contribution to the maze surgical procedure applied to atrial fibrillation.

Taquicardia paroxística supraventrictular con disociación ventrículo auricular: a propósito de un caso / Supraventricular paroxysmal tachycardia with ventriculo-atrial dissociation: report of one case

Nodal reentrant supraventricular paroxysmal tachycardia corresponds to a reentry circuit established between fibers with different conduction relocities and refractory periods in the atrioventricular mode. These are the slow and fast nodal pathways. That ventricular tissue does not form part of the circuit of this arrbythmia is accepted nowadays, and the involvement of atrial tissue is discussed. We report a 57 years old male with a nodal reentrant tachycardia. In the electrophystological study be presented an atrial and ventricular dissociation during the tachycardia. These findings allow a better undestanding of the electrophysiological substrae of this arrhytmia

The ongoing influence of staff training on the performance of radiofrequency catheter ablation.

The aim of this study was to assess whether the performance of RF catheter ablations continues to improve by further staff training once an initial success rate of > 90% has been achieved. Two hundred and ninety-five procedures of SVT catheter ablation using RF energy were studied. Atrial tachycardia and atrial flutter substrate ablations were not included. The procedures were performed during a 4-year period by the same physician and nurse, who had previous training in these procedures. The 4-year period was subdivided into four consecutive 1-year periods in which 69, 72, 68, and 86 procedures were performed. The outcome, recurrence rate, and duration of the curative procedure were compared among the four periods. There was no significant difference in the initial success rate among the four periods. The recurrence rate decreased from 21.74% to 13.95% (P < 0.05). The duration of the curative procedure decreased from 93.7 +/- 78.4 minutes to 39.1 +/- 32.2 minutes (P < 0.001), and the fluoroscopic time decreased from 25.5 +/- 22.3 minutes to 11.3 +/- 8.2 minutes (P < 0.001). These results were similar when accessory pathway and selective AV nodal pathways ablations were separately evaluated. Following the initial staff training, during which the expected 80%-90% success rate is achieved, additional training will reduce the recurrence rate and the duration of the procedures at a similar level of success.

Late endocardial pacing lead body migration compromising Fontan physiology.

Migration of intracardiac transvenous pacing leads may occur. There is a known risk of intrapulmonary ventricular pacing lead migration in patients with endocardial lead systems. In the current report we present the late intrapulmonary migration of an endocardial atrial pacing lead body. The patient had undergone antitachycardia pacemaker placement to control recurrent atrial tachyarrhythmias following the Fontan procedure. Although the lead electrode remained in place and continued to pace, the lead body migrated, causing severe obstruction to blood flow. This resulted in severe cardiac decompensation, which was ultimately ameliorated by lead repositioning.

[Supraventricular tachycardias: mechanism, diagnosis and therapy]. / Supraventrikuläre Tachykardien: Mechanismen, Diagnostik und Therapie.

Most of the paroxysmal forms of supraventricular tachycardia are reentry tachycardias in origin with either an AV-nodal reentry (AVNRT; approx. 50%) or an AV reentry circuit via accessory pathway (AVRT; approx. 30%) as the anatomical basis of tachycardia. The therapeutic options include either drug therapy or transcatheter radiofrequency ablation. In asymptomatic patients, where supra-ventricular tachycardia or WPW syndrome was documented incidentally, an expectative approach without therapy is usually recommended. However, if frequent tachycardia recurrences or severe clinical symptoms (syncope, pre-syncope make treatment mandatory, medical therapy with either betablockers, calcium antagonists or digoxin should be tried if AV-nodal reentry tachycardia is the mechanism (no evidence of WPW syndrome on the 12-lead ECG). In patients with symptomatic WPW syndrome or drug refractory AV-nodal reentry tachycardia, transcatheter radiofrequency ablation with its good results and low complication rate is the therapy of choice. The treatment modality is particularly indicated in young patients who otherwise would need lifelong drug therapy. In contrast, supraventricular tachycardias with badly defined anatomical substrate, such as multifocal atrial tachycardias or atrial fibrillation, should in the first place be treated medically and not by radiofrequency ablation.

Electrophysiologic characteristics and radiofrequency catheter ablation in patients with multiple atrioventricular nodal reentry tachycardias.

Information about the mechanism and radiofrequency catheter ablation of multiple atrioventricular (AV) nodal reentry tachycardias is limited. Among the 550 consecutive patients with AV nodal reentry tachycardia, 36 with multiple forms of AV nodal reentry tachycardia were included in this study. Electrophysiologic characteristics, as well as the efficacy and safety of radiofrequency ablation, were evaluated. Results showed that anterograde dual pathways were seen in 32 patients and triple pathways in 2, and retrograde dual pathways were seen in 23 patients and triple pathways in 11. Twenty-two patients had 2 types, 7 had 3 types, 5 had 4 types, and 2 had 5 types of AV nodal reentry tachycardia and echoes. After delivering radiofrequency energy to the target sites, 32 patients had no induction of AV nodal reentry tachycardia and only 4 had induction of 1 echo. Furthermore, 22 patients (61%) had simultaneous elimination or modification of the slow and/or intermediate pathways in the anterograde and retrograde direction. During the follow-up period of 19 +/- 14 months, 2 patients had recurrence of tachycardia. Thus, multiple anterograde and retrograde AV nodal pathways were present in the human AV node and they constituted the substrates of reentry circuits. Radiofrequency catheter ablation was safe and effective in eliminating the slow and intermediate pathways for maintenance of multiple AV nodal reentry tachycardias.

Sinus node reentrant tachycardia.

This review article discusses the electrophysiological basis of sinus node reentry, clinical features of sinus node reentry, and the management of this uncommon tachycardia with drugs and ablative therapy. It also proposes the use of the term "sinoatrial reentrant tachycardia" for this form of tachycardia.

[Ablative methods, therapeutic alternative to medical treatment for junctional tachycardia]. / Les méthodes ablatives, alternative thérapeutique aux traitements médicamenteux pour les tachycardies jonctionnelles.

The clinical syndrome corresponding to junctional tachycardia is generally known as Bouveret's disease, but actually corresponds to two quite separate entities: 1) tachycardia related to a secondary atrioventricular pathway or Kent bundle; 2) intranodal tachycardia arising in the atrio-ventricular node. Until recently, anti-arrhythmics were used to treat most of the cases of accessory pathways. If this was unsuccessful or if the anti-arrhythmics induced adverse effects and in life-threatening cases affecting Kent bundles, surgical section was sometimes proposed, carrying a non-negligible risk of morbidity and mortality. Intranodal arrhythmia is not a serious, but may call for prophylactic antiarrhythmic treatment if it becomes too frequent and disabling. Before the advent of ablative treatment, there was no satisfactory alternative to antiarrhythmic treatment. Ablation of the accessory pathways or selection ablation of the slow pathway of the atrio-ventricular node (sometimes of the rapid pathway) is not achieved by applying a high-frequency current (radiofrequency), which has virtually replaced fulguration (destruction using a modified electrical current). In both types of tachycardia, a cure is obtained in 90% of cases with a low incidence of complications and virtually no risk of mortality, which contrasts favorably with long-term antiarrhythmic treatment (or surgical section of Kent bundles), which justifies the large-scale development of radiofrequency ablation.

[Ablation by radiofrequency in the treatment of atrial arrhythmia]. / L'ablation par radiofréquence dans le traitement des arythmies auriculaires.

Atrial arrhythmias resistant to medical therapy are still a common indication for ablation of the normal atrioventricular conduction pathway (Tawara node and His Bundle). However, the development of catheter techniques of intra-atrial ablation to destroy arrhythmogenic myocardial zones enables radical cure of the arrhythmias with the respect of the nodo-hisian pathway. With respect to common flutter, a number of series, including our own, show a 50 to 75% long-term success rate. We believe that a very high success rate in the ablation of flutter will probably be achieved in a reproducible manner but this will require a more accurate understanding of the tachycardia circuit and technological developments allowing controlled radio-frequency destruction of bigger atrial myocardial zone. Experience of radio-frequency ablation atrial of atrial extrasystoles is more limited than that of flutter and there are fewer published series. Globally, catheter ablation of atrial tachycardia remains a more difficult and a less well codified procedure than that of accessory pathways or of intra-nodal reentry. Radio-frequency ablation in this indication is not without danger in view of the thinness of the atrial wall. We believe that radio-frequency catheter ablation for atrial arrhythmias should, for the moment, be reserved for centres specialised in the techniques of electro-physiological investigation and ablation.