Differential Responses of the Septal Ventricle and the Atrial Signals During Ongoing Entrainment: A Method to Differentiate Orthodromic Reciprocating Tachycardia Using Septal Accessory Pathways From Atypical Atrioventricular Nodal Reentry.

BACKGROUND: Differential diagnosis between tachycardia mediated by septal accessory pathways (AP) and atypical atrioventricular nodal reentry can be challenging. We hypothesized that an immediate versus delayed pace-related advancement of the atrial electrogram, once the local septal parahisian ventricular electrogram (SVE) has been advanced, may help in this diagnosis. METHODS AND RESULTS: We focused on differential timing between SVE and atrial signals at the initiation of continuous right ventricular apical pacing during tachycardia. SVE advancement preceding atrial reset was defined as SVE advanced by the paced wave fronts while atrial signal continued at the tachycardia cycle. We analyzed 51 atypical atrioventricular nodal reentry (45% posterior type) and 80 AP tachycardias (anteroseptal [10], parahisian [18], midseptal [12], and posteroseptal [40]). SVE advancement preceding atrial reset was observed in 98% of atrioventricular nodal reentries during 4±1.1 cycles; this phenomena was observed in 6 (8%) of the atrioventricular reentrant tachycardia mediated by septal AP (P<0.001; sensitivity 98%; specificity 93%; positive predictive value 90%; negative predictive value 99%) and lasted 1 single cycle (P<0.001). Right posteroseptal AP tachycardias were distinctly characterized by atrial reset preceding SVE advancement (with ventricular fusion; specificity 100%; positive predictive value 100%). In 11 cases, it was impossible to achieve sustain entrainment. In all of them, the differential responses at the entrainment attempt allowed for appropriate diagnosis. CONCLUSIONS: The differential response of the SVE and the atrial electrogram at the initiation of continuous right ventricular apical pacing during tachycardia effectively distinguishes between atypical atrioventricular nodal reentry and atrioventricular reentrant tachycardia mediated by septal APs.

Clinical impact of defibrillation testing at the time of implantable cardioverter-defibrillator insertion.

BACKGROUND: Ventricular fibrillation is routinely induced during implantable cardioverter-defibrillator insertion to assess defibrillator performance, but this strategy is experiencing a progressive decline. We aimed to assess the efficacy of defibrillator therapies and long-term outcome in a cohort of patients that underwent defibrillator implantation with and without defibrillation testing. METHODS: Retrospective observational series of consecutive patients undergoing initial defibrillator insertion or generator replacement. We registered spontaneous ventricular arrhythmias incidence and therapy efficacy, and mortality. RESULTS: A total of 545 patients underwent defibrillator implantation (111 with and 434 without defibrillation testing). After 19 (range 9-31) months of follow-up, the death rate per observation year (4% vs. 4%; p = 0.91) and the rate of patients with defibrillator-treated ventricular arrhythmic events per observation year (with test: 10% vs. without test: 12%; p = 0.46) were similar. The generalized estimating equations-adjusted first shock probability of success in patients with test (95%; CI 88-100%) vs. without test (98%; CI 96-100%; p = 0.42) and the proportion of successful antitachycardia therapies (with test: 87% vs. without test: 80%; p = 0.35) were similar between groups. There was no difference in the annualized rate of failed first shock per patient and per shocked patient between groups (5% vs. 4%; p = 0.94). CONCLUSIONS: In this observational study, that included an unselected population of patients with a defibrillator, no difference was found in overall mortality, first shock efficacy and rate of failed shocks regardless of whether defibrillation testing was performed or not.

Comparison of the safety and feasibility of arrhythmia ablation using the Amigo Robotic Remote Catheter System versus manual ablation.

The aim of this study is to evaluate the safety and feasibility of using the Amigo Remote Catheter System (RCS) in arrhythmia ablation procedures. Because Amigo allows the physician to operate all catheter function outside of the radiation field, operator exposure time was also evaluated. This is a nonrandomized, prospective clinical trial conducted at 1 site (identifier: NCT01834872). The study prospectively enrolled 50 consecutive patients (mean age 59 ± 15 years, 72% men) with any type of arrhythmia (23 atrial fibrillation ablation, 12 common atrial flutters, 10 patients with other supraventricular tachycardia, 4 ventricular tachycardia, and 1 patient with palpitations with no arrhythmia induced) referred for catheter ablation, in which we used RCS. Fifty matched ablation procedures (mean age 57 ± 14 years, 70% men) performed during the same time period, without RCS, were enrolled into the control group. Acute ablation success was 96% with RCS and 98% in the manual group. In only 2 cases, the physician switched to manual ablation (1 ventricular tachycardia and 1 accessory pathway) to complete the procedure. There were no complications related to the use of RCS. No differences were observed in total procedure time, total fluoroscopy time, or total radiofrequency delivery compared with the manual group. In procedures performed with RCS, the operator's fluoroscopy exposure time was reduced by 68 ± 16%. In conclusion, arrhythmia ablation with RCS is safe and feasible. Furthermore, it significantly reduces operator's exposure to radiation.

Specificity of electrocardiographic criteria for the differential diagnosis of wide QRS complex tachycardia in patients with intraventricular conduction defect.

BACKGROUND: In patients with organic intraventricular conduction defects (IVCDs), (1) QRS morphology during sinus rhythm frequently meets ventricular tachycardia (VT) morphological criteria and (2) there are further rate-related changes in QRS morphology. OBJECTIVE: To search for the best morphological criteria in this context. METHODS: We prospectively studied 69 patients, in sinus rhythm, with QRS duration ≥120 ms. Continuous rapid atrial pacing (RAP) trains were introduced at increasing rates in order to mimic supraventricular tachycardia. We analyzed the specificity of VT criteria during RAP. Finally, we used the criteria with a specificity of ≥0.9 in a "test sample" of 53 patients with preexisting IVCD and wide complex tachycardia to confirm their validity. RESULTS: Only 10 of the 20 analyzed criteria had a specificity of ≥0.9 during RAP at the highest rate. The specificity of these 10 criteria was confirmed in the test sample. The best accuracy to diagnose VT was obtained: for an isolated criterion: "R-wave peak time (RWPT) ≥50 ms at lead II" (specificity = 0.97; sensitivity = 0.67); for an algorithm: the combination of 2 criteria "RWPT ≥50 ms at lead II" and "absence of RS patterns in precordial leads" (specificity = 0.97; sensitivity = 0.88). CONCLUSIONS: In patients with IVCD, (1) specificity of most VT criteria is low during RAP, suggesting a limited applicability of many of these criteria in case they develop supraventricular tachycardia, and (2) the superior accuracy to diagnose VT was observed with "RWPT ≥50 ms at lead II" and for an algorithm with the combination of "RWPT ≥50 ms at lead II" and "absence of RS patterns in precordial leads."

Differentiation of atrioventricular nodal reentrant tachycardia from orthodromic reciprocating tachycardia by the resetting response to ventricular extrastimuli: comparison to response to continuous ventricular pacing.

BACKGROUND: The usefulness of ventricular entrainment to differentiate AV nodal reentrant tachycardia (AVNRT) from orthodromic reciprocating tachycardia (ORT) by substracting the corrected postpacing interval (cPPI) from the tachycardia cycle length (TCL) or the ventriculoatrial interval during stimulation (SA) from that during tachycardia (VA) have been widely validated. However, some tachycardias are interrupted by pacing trains but may not be so by ventricular extrastimuli resulting in resetting. OBJECTIVES: To validate prospectively the diagnostic yield of cPPI-TCL and SA-VA measurements after resetting and to determine the proportion of AVNRT and ORT that can be entrained and/or reset from the right ventricular apex (RVA). METHODS: 223 consecutive patients with inducible AVNRT or ORT underwent pacing trains and single extrastimulus (also double extrastimuli if singles did not reset tachycardia) at the RVA. We calculated cPPI-TCL and SA-VA during entrainment and resetting. RESULTS: Entrainment could not be achieved in 15.2% of tachycardias because of consistent tachycardia interruption by pacing; resetting was observed in 99.5%. Values of cPPI-TCL and SA-VA > 110 milliseconds after resetting identified AVNRT as accurately as after entrainment. Values for cPPI-TCL/ SA-VA were: sensitivity: 98/100%; specificity: 96/98%; positive predictive value: 98/99%; negative predictive value: 98/100%. CONCLUSIONS: Determinations of cPPI-TCL and SA-VA after resetting with single or double RVA extrastimuli are useful maneuvers to differentiate AVNRT from ORT and can be used for nearly every inducible AVNRT or ORT, even if they are interrupted by ventricular trains.

High-rate pacing-induced atrial fibrillation effectively reveals properties of spontaneously occurring paroxysmal atrial fibrillation in humans.

AIMS: Research on paroxysmal atrial fibrillation (AF) assumes that fibrillation induced by rapid pacing adequately reproduces spontaneously occurring paroxysmal AF in humans. We aimed to compare the spectral properties of spontaneous vs. induced AF episodes in paroxysmal AF patients. METHODS AND RESULTS: Eighty-five paroxysmal AF patients arriving in sinus rhythm to the electrophysiology laboratory were evaluated prior to ablation. Atrial fibrillation was induced by rapid pacing from the pulmonary vein-left atrial junctions (PV-LAJ), the coronary sinus (CS), or the high right atrium (HRA). Simultaneous recordings were obtained using multipolar catheters. Off-line power spectral analysis of 5 s bipolar electrograms was used to determine dominant frequency (DF) at recording sites with regularity index >0.2. Sixty-eight episodes were analysed for DF. Comparisons were made between spontaneous (n = 23) and induced (n = 45) AF episodes at each recording site. No significant differences were observed between spontaneous and induced AF episodes in HRA (5.18 ± 0.69 vs. 5.06 ± 0.91 Hz; P = 0.64), CS (5.27 ± 0.69 vs. 5.36 ± 0.76 Hz; P = 0.69), or LA (5.72 ± 0.88 vs. 5.64 ± 0.75 Hz; P = 0.7) regardless of pacing site. Consistent with these results, paired analysis in seven patients with both spontaneous and induced AF episodes, showed no regional DFs differences. Moreover, a left-to-right DF gradient was also present in both spontaneous (PV-LAJ 5.71 ± 0.81 vs. HRA 5.18 ± 0.69 Hz; P = 0.005) and induced (PV-LAJ 5.62 ± 0.72 vs. HRA 5.07 ± 0.91 Hz; P = 0.002) AF episodes, with no differences between them (P = not specific). CONCLUSION: In patients with paroxysmal AF, high-rate pacing-induced AF adequately mimics spontaneously initiated AF, regardless of induction site.

Implantable defibrillator electrograms and origin of left ventricular impulses: an analysis of regionalization ability and visual spatial resolution.

INTRODUCTION: The implantable cardioverter-defibrillator (ICD) electrogram (EG) is a documentation of ventricular tachycardia. We prospectively analyzed EGs from ICD electrodes located at the right ventricle apex to establish (1) ability to regionalize origin of left ventricle (LV) impulses, and (2) spatial resolution to distinguish between paced sites. METHODS AND RESULTS: LV electro-anatomic maps were generated in 15 patients. ICD-EGs were recorded during pacing from 22 ± 10 LV sites. Voltage of far-field EG deflections (initial, peak, final) and time intervals between far-field and bipolar EGs were measured. Blinded visual analysis was used for spatial resolution. Initial deflections were more negative and initial/peak ratios were larger for lateral versus septal and superior versus inferior sites. Time intervals were shorter for apical versus basal and septal versus lateral sites. Best predictive cutoff values were voltage of initial deflection <-1.24 mV, and initial/peak ratio >0.45 for a lateral site, voltage of final deflection <-0.30 for an inferior site, and time interval <80 milliseconds for an apical site. In a subsequent group of 9 patients, these values predicted correctly paced site location in 54-75% and tachycardia exit site in 60-100%. Recognition of paced sites as different by EG inspection was 91% accurate. Sensitivity increased with distance (0.96 if ≥ 2 cm vs 0.84 if < 2 cm, P < 0.001) and with presence of low-voltage tissue between sites (0.94 vs 0.88, P < 0.001). CONCLUSIONS: Standard ICD-EG analysis can help regionalize LV sites of impulse formation. It can accurately distinguish between 2 sites of impulse formation if they are ≥2 cm apart.

Mechanisms of fractionated electrograms formation in the posterior left atrium during paroxysmal atrial fibrillation in humans.

OBJECTIVES: The aim of this paper was to study mechanisms of formation of fractionated electrograms on the posterior left atrial wall (PLAW) in human paroxysmal atrial fibrillation (AF). BACKGROUND: The mechanisms responsible for complex fractionated atrial electrogram formation during AF are poorly understood. METHODS: In 24 patients, we induced sustained AF by pacing from a pulmonary vein. We analyzed transitions between organized patterns and changes in electrogram morphology leading to fractionation in relation to interbeat interval duration (systolic interval [SI]) and dominant frequency. Computer simulations of rotors helped in the interpretation of the results. RESULTS: Organized patterns were recorded 31 ± 18% of the time. In 47% of organized patterns, the electrograms and PLAW activation sequence were similar to those of incoming waves during pulmonary vein stimulation that induced AF. Transitions to fractionation were preceded by significant increases in electrogram duration, spike number, and SI shortening (R(2) = 0.94). Similarly, adenosine infusion during organized patterns caused significant SI shortening leading to fractionated electrograms formation. Activation maps during organization showed incoming wave patterns, with earliest activation located closest to the highest dominant frequency site. Activation maps during transitions to fragmentation showed areas of slowed conduction and unidirectional block. Simulations predicted that SI abbreviation that heralds fractionated electrograms formation might result from a Doppler effect on wave fronts preceding an approaching rotor or by acceleration of a stationary or meandering, remotely located source. CONCLUSIONS: During induced AF, SI shortening after either drift or acceleration of a source results in intermittent fibrillatory conduction and formation of fractionated electrograms at the PLAW.

Dominant frequency differences in atrial fibrillation patients with and without left ventricular systolic dysfunction.

AIMS: The aim of this study was to determine the mechanisms of atrial fibrillation (AF) in patients with left ventricular systolic dysfunction (LVSD). METHODS AND RESULTS: Dominant frequency (DF) spatiotemporal stability was studied in 15 patients with persistent AF (PEAF) and LVSD (Group I), 15 with PEAF without LVSD (Group II), and 10 with paroxysmal AF (PAAF) without LVSD (Group III). Dominant frequencies were analysed at 536 sites at baseline (DF1) and 26 +/- 12 min later (DF2). A DF1-DF2 difference of

Utilidad diagnóstica de los electrogramas almacenados por el desfibrilador automático implantable / Diagnostic usefulness of the electrograms stored by implantable cardioverter–defibrillators

Los electrogramas almacenados por los desfibriladores implantables actuales permiten al clínico revisar las alteraciones eléctricas durante los eventos que conducen a la activación del desfibrilador, así como evaluar el resultado de la terapia administrada. En la mayoría de los pacientes, esta información permite efectuar un diagnóstico preciso del tipo de arritmia causante de la activación del dispositivo y, como resultado, optimizar el tratamiento de estos pacientes. Sin embargo, todavía es preciso establecer criterios de discriminación adicionales que nos permitan diferenciar con mayor precisión la etiología de los episodios detectados por el dispositivo. En este artículo se describen: a) los principios básicos para la discriminación de arritmias basado en el análisis del registro de los electrogramas intracavitarios (EGM) de los episodios; b) la utilidad del análisis de los EGM en el tratamiento de pacientes con arritmias ventriculares; c) las principales limitaciones de los métodos empleados, y d) finalmente, se presentan pruebas científicas de la utilidad de nuevos métodos de discriminación (AU)

The electrograms stored by present-day implantable cardioverter–defibrillators (ICDs) enable clinicians to review the electrical changes that occur during events leading to device discharge and to evaluate the effects of the therapy administered. In most patients, this information enables the type of arrhythmia responsible for ICD activation to be accurately determined and, consequently, treatment to be optimized. Nevertheless, additional discriminative criteria are needed to enable the etiology of the episodes detected by the device to be classified yet more accurately. This article considers: a) the basic principles for classifying arrhythmias on the basis of an analysis of stored intracardiac electrograms of arrhythmic episodes; b) the usefulness of intracardiac electrogram analysis for treating patients with ventricular arrhythmias; c) the main limitations of the classification methods currently used; and, finally, d) the evidence available on the usefulness of new classification methods (AU)

Tachycardia-related channel in the scar tissue in patients with sustained monomorphic ventricular tachycardias: influence of the voltage scar definition.

BACKGROUND: Endocardial mapping before sustained monomorphic ventricular tachycardia (SMVT) induction may reduce mapping time during tachycardia and facilitate the ablation of unmappable VT. METHODS AND RESULTS: Left ventricular electroanatomic voltage maps obtained during right ventricular apex pacing in 26 patients with chronic myocardial infarction referred for VT ablation were analyzed to identify conducting channels (CCs) inside the scar tissue. A CC was defined by the presence of a corridor of consecutive electrograms differentiated by higher voltage amplitude than the surrounding area. The effect of different levels of voltage scar definition, from 0.5 to 0.1 mV, was analyzed. Twenty-three channels were identified in 20 patients. The majority of CCs were identified when the voltage scar definition was < or =0.2 mV. Electrograms with > or =2 components were recorded more frequently at the inner than at the entrance of CCs (100% versus 75%, P< or =0.01). The activation time of the latest component was longer at the inner than at the entrance of CCs (200+/-40 versus 164+/-53 ms, P< or =0.001). Pacing from these CCs gave rise to a long-stimulus QRS interval (110+/-49 ms). Radiofrequency lesion applied to CCs suppressed the inducibility in 88% of CC-related tachycardias. During a follow-up of 17+/-11 months, 23% of the patients experienced a VT recurrence. CONCLUSIONS: CCs represent areas of slow conduction that can be identified in 75% of patients with SMVT. A tiered decreasing-voltage definition of the scar is critical for CC identification.

Los sistemas navegadores en la electrofisiología actual / Navigation systems in current electrophysiology

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[Non-fluoroscopic electroanatomical mapping (CARTO system) in the ablation of atrial tachycardias]. / La cartografía electroantómica no fluoroscópica (sistema CARTO) en la ablación de las taquicardias auriculares.

INTRODUCTION AND OBJECTIVES: The recent introduction of navigation systems has made substantial improvements in cardiac electrophysiological mapping. We present our experience with non-fluoroscopic electroanatomical mapping in patients with atrial tachycardias. PATIENTS AND METHOD: We studied 24 consecutive patients with atrial tachycardias (10 of whom had undergone previous radiofrequency ablation which failed). In all patients we performed electroanatomical mapping of the atria with the CARTO system, which combines electrophysiological and spatial information and allows visualization of atrial activation in a three-dimensional anatomical reconstruction of the atrial cavity. Mapping was performed during tachycardia (22 patients) or in sinus rhythm (2 patients), using a left atrial approach in 12 patients. Cooled-tip ablation was performed in 3 patients. RESULTS: Three-dimensional mapping distinguished clearly and rapidly between reentrant (9 patients) and focal mechanisms (15 patients). Radiofrequency catheter ablation was aimed at the critical isthmus of conduction (voltage maps) in patients with macroreentrant tachycardias. For focal tachycardias the catheter was re-navigated within the target area (activation maps) to the earliest focus of ectopic impulses. Acute success was obtained in 19 patients (79.2%), with early recurrence in 2 of them. Fluoroscopy time was 60 (21 min). CONCLUSIONS: Visualization of atrial activation in a three-dimensional reconstruction of the atria with the CARTO electroanatomical mapping system facilitated the integration of electrophysiological and anatomical information in patients with atrial tachycardias. This technique is potentially helpful in ensuring successful treatment of the substrate of tachycardia in this selected group of patients.

La cartografía electroanatómica no fluoroscópica (sistema CARTO) en la ablación de las taquicardias auriculares / Non-Fluoroscopic electroanatomical mapping (CARTO System) in the ablation of atrial tachycardias

Introducción y objetivos. La introducción de los sistemas navegadores ha supuesto un cambio sustancial en la cartografía electrofisiológica cardíaca. Presentamos nuestra experiencia con el uso de la cartografía electroanatómica no fluoroscópica en pacientes con taquicardias auriculares. Pacientes y método. Se incluye a 24 pacientes consecutivos con taquicardias auriculares (10 de ellos con intentos previos de ablación fallidos). En todos los casos se realizó una cartografía auricular electroanatómica mediante el sistema CARTO, que combina información electrofisiológica y espacial y permite la visualización de la activación atrial en una reconstrucción anatómica tridimensional de la aurícula. La cartografía se realizó durante taquicardia (22 pacientes) o en ritmo sinusal (2 pacientes), con abordaje en la aurícula izquierda en 12 pacientes. La ablación se efectuó con un catéter de punta irrigada en 3 pacientes. Resultados. La cartografía tridimensional permitió una clara y rápida distinción entre un mecanismo macrorreentrante (9 pacientes) y un origen focal (15 pacientes). Las aplicaciones de radiofrecuencia se dirigieron hacia el istmo crítico de conducción identificado en las macrorreentradas mediante mapas de voltaje de auriculogramas o hacia el área de mayor precocidad ectópica focal en los mapas de activación. El tratamiento se realizó con éxito en 19 pacientes (79,2 por ciento) y se produjo una recurrencia precoz en 2 de ellos. El tiempo de fluoroscopia fue de 60 ñ 21 min. Conclusiones. La cartografía electroanatómica con sistema CARTO permitió la visualización tridimensional de la activación auricular, evitando el esfuerzo de integración electrofisiológico y anatómico en estos pacientes con taquicardias auriculares. El apoyo iconográfico que supone podría facilitar el éxito de la ablación con radiofrecuencia en este seleccionado grupo de pacientes (AU)