Comportamiento del tiempo de conducción retrógrada al momento de la inducción de las taquicardias supraventriculares y su rol en el diagnóstico diferencial / Behavior of Retrograde Conduction Time at Supraventricular Tachycardia Induction and its Role in Differential Diagnosis

RESUMEN Antecedentes : El diagnóstico diferencial entre la taquicardia reentrante ortodrómica (TRO) y la taquicardia por reentrada nodal atípica (TRNa) puede ser dificultoso. Nuestra hipótesis es que las TRNa tienen más variabilidad en el tiempo de con ducción retrógrada al comienzo de la taquicardia que las TRO. Nuestros objetivos fueron evaluar la variabilidad en el tiempo de conducción retrógrada al inicio de la taquicardia en TRNa y TRO, y proponer una nueva herramienta diagnóstica para diferenciar estas dos arritmias. Métodos : Se midió el intervalo ventrículo-auricular (VA) de los primeros latidos tras la inducción de la taquicardia, hasta su estabilización. La diferencia entre el intervalo VA máximo y el mínimo se definió como delta VA (ΔVA). También contamos el número de latidos necesarios para que se estabilice el intervalo VA. Se excluyeron las taquicardias auriculares. Resultados : Se incluyeron 101 pacientes. Se diagnosticó TRO en 64 pacientes y TRNa en 37. El ΔVA fue 0 (rango intercuartílico, RIC, 0-5) milisegundos (ms) en la TRO frente a 40 (21-55) ms en la TRNa (p < 0,001). El intervalo VA se estabilizó significativamente antes en la TRO (1,5 [1-3] latidos) que en la TRNa (5 [4-7] latidos; p < 0,001). Un ΔVA < 10 ms diagnosticó TRO con 100% de sensibilidad, especificidad y valores predictivos positivo y negativo. La estabilización del intervalo VA en menos de 3 latidos predijo TRO con buena precisión diagnóstica. Los resultados fueron similares considerando sólo vías accesorias septales. Las TRN típicas tuvieron una variación intermedia. Conclusión : Un ΔVA < 10 ms es un criterio simple, que distingue con precisión la TRO de la TRNa, independientemente de la localización de la vía accesoria.

ABSTRACT Background : Differential diagnosis between orthodromic reentrant tachycardia (ORT) and atypical nodal reentrant tachy cardia (ANRT) can be challenging. Our hypothesis was that ANRT presents more variability in retrograde conduction time at tachycardia onset than ORT. Objectives : The objectives of this study were to assess retrograde conduction time variability at the start of tachycardia in ANRT and ORT, and postulate a new diagnostic tool to differentiate these two types of arrhythmias. Methods : The ventriculoatrial (VA) interval of the first beats after tachycardia induction was measured until stabilization. The difference between the maximum and minimum VA interval was defined as delta VA (ΔVA), and the number of beats needed for VA interval stabilization was also assessed. Atrial tachycardias were excluded. Results : In a total of 101 patients included in the study, ORT was diagnosed in 64 patients and ANRT in 37. ΔVA interval was 0 (interquartile range [IQR] 0-5) milliseconds (ms) in ORT vs. 40 (21-55) ms in ANRT (p <0.001). The VA interval significantly stabilized earlier in ORT (1.5 [1-3] beats) than in ANRT (5 [4-7] beats) (p<0.001). A ΔVA <10 ms diagnosed ORT with 100% sensitivity, specificity, and positive and negative predictive values. Ventriculoatrial interval stabilization in less than 3 beats predicted ORT with good diagnostic accuracy. The results were similar considering only accessory septal pathways. Typical NRTs presented an intermediate variation. Conclusion : Presence of DVA <10 ms is a simple criterion that accurately differentiates ORT from ANRT, independently of the accessory pathway localization.

Variability of the VA interval at tachycardia induction: a simple method to differentiate orthodromic reciprocating tachycardia from atypical atrioventricular nodal reentrant tachycardia.

BACKGROUND: The differential diagnosis between orthodromic atrioventricular reentry tachycardia (AVRT) and atypical AV nodal reentrant tachycardia (aAVNRT) is sometimes challenging. We hypothesize that aAVNRTs have more variability in the retrograde conduction time at tachycardia onset than AVRTs. METHODS: We aimed to assess the variability in retrograde conduction time at tachycardia onset in AVRT and aAVNRT and to propose a new diagnostic tool to differentiate these two arrhythmia mechanisms. We measured the VA interval of the first beats after tachycardia induction until it stabilized. The difference between the maximum and minimum VA intervals (∆VA) and the number of beats needed for the VA interval to stabilize was analyzed. Atrial tachycardias were excluded. RESULTS: A total of 107 patients with aAVNRT (n = 37) or AVRT (n = 64) were included. Six additional patients with decremental accessory pathway-mediated tachycardia (DAPT) were analyzed separately. All aAVNRTs had VA interval variability. The median ∆VA was 0 (0 - 5) ms in AVRTs vs 40 (21 - 55) ms in aAVNRTs (p < 0.001). The VA interval stabilized significantly earlier in AVRTs (median 1.5 [1 - 3] beats) than in aAVNRTs (5 [4 - 7] beats; p < 0.001). A ∆VA < 10 ms accurately differentiated AVRT from aAVNRT with 100% of sensitivity, specificity, and positive and negative predictive values. The stabilization of the VA interval at < 3 beats of the tachycardia onset identified AVRT with sensitivity, specificity, and positive and negative predictive values of 64.1%, 94.6%, 95.3%, and 60.3%, respectively. A ∆VA < 20 ms yielded good diagnostic accuracy for DAPT. CONCLUSIONS: A ∆VA < 10 ms is a simple and useful criterion that accurately distinguished AVRT from atypical AVNRT. Central panel: Scatter plot showing individual values of ∆VA in atypical AVNRT and AVRT. Left panel: induction of atypical AVNRT. The VA interval stabilizes at the 5th beat and the ∆VA is 62 ms (maximum VA interval: 172 ms - minimum VA interval: 110 ms). Right panel: induction of AVRT. The tachycardia has a fixed VA interval from the first beat. ∆VA is 0 ms.

[Treatment of pulmonary vein stenosis secondary to radiofrequency ablation]. / Tratamiento de estenosis de venas pulmonares secundaria a ablación por radiofrecuencia.

Isolation of the pulmonary veins by applying radiofrequency is an effective treatment for atrial fibrillation. One of the potential complications with higher clinical compromise utilizing this invasive technique is the occurrence of stenosis of one or more pulmonary veins. This complication can be treated by angioplasty with or without stent implantation, with an adequate clinical improvement, but with a high rate of restenosis.

Tratamiento de estenosis sintomática de venas pulmonares secundaria a ablación por radiofrecuencia

El aislamiento de las venas pulmonares mediante la aplicación de radiofrecuencia es un tratamiento efectivo de la fibrilación auricular. Una de las complicaciones potenciales y de mayor compromiso clínico de esta técnica invasiva es la estenosis de una o varias venas pulmonares. Esta complicación puede ser tratada mediante angioplastia con o sin colocación de stent, logrando una adecuada mejoría clínica, aunque con un alto índice de recurrencia por re-estenosis.

Isolation of the pulmonary veins by applying radiofrequency is an effective treatment for atrial fibrillation. One of the potential complications with higher clinical compromise utilizing this invasive technique is the occurrence of stenosis of one or more pulmonary veins. This complication can be treated by angioplasty with or without stent implantation, with an adequate clinical improvement, but with a high rate of restenosis.

Tratamiento de estenosis sintomática de venas pulmonares secundaria a ablación por radiofrecuencia

El aislamiento de las venas pulmonares mediante la aplicación de radiofrecuencia es un tratamiento efectivo de la fibrilación auricular. Una de las complicaciones potenciales y de mayor compromiso clínico de esta técnica invasiva es la estenosis de una o varias venas pulmonares. Esta complicación puede ser tratada mediante angioplastia con o sin colocación de stent, logrando una adecuada mejoría clínica, aunque con un alto índice de recurrencia por re-estenosis.(AU)

Isolation of the pulmonary veins by applying radiofrequency is an effective treatment for atrial fibrillation. One of the potential complications with higher clinical compromise utilizing this invasive technique is the occurrence of stenosis of one or more pulmonary veins. This complication can be treated by angioplasty with or without stent implantation, with an adequate clinical improvement, but with a high rate of restenosis.(AU)

Tratamiento de estenosis de venas pulmonares secundaria a ablación por radiofrecuencia. / [Treatment of pulmonary vein stenosis secondary to radiofrequency ablation].

Isolation of the pulmonary veins by applying radiofrequency is an effective treatment for atrial fibrillation. One of the potential complications with higher clinical compromise utilizing this invasive technique is the occurrence of stenosis of one or more pulmonary veins. This complication can be treated by angioplasty with or without stent implantation, with an adequate clinical improvement, but with a high rate of restenosis.

Safety, long-term results, and predictors of recurrence after complete endocardial ventricular tachycardia substrate ablation in patients with previous myocardial infarction.

Conduction channels and electrograms with isolated component/late potentials are sensitive markers of the substrate of post-myocardial infarction sustained monomorphic ventricular tachycardia (VT). Ablation of all conduction channels and isolated component/late potentials (complete endocardial VT substrate ablation [CEVTSA]) during sinus rhythm could simplify and facilitate the ablation procedure, mainly in patients without references for clinical VT substrate identification. The aim of this study was to assess the safety, efficacy, and predictors of VT recurrence after CEVTSA. Electroanatomic mapping and CEVTSA were performed in 59 post-myocardial infarction patients (mean age 67 ± 9 years, mean left ventricular ejection fraction 30 ± 11%), 24 of whom did not have clinical VT substrate references. The mean areas of scar (≤1.5 mV) and dense scar (≤0.5 mV) were 76 ± 42 and 34 ± 24 cm(2), respectively; isolated component/late potentials and conduction channels were identified and ablated in 97% and 83% of patients (mean ablation area 14 ± 10 cm(2)). No life-threatening complications occurred during the procedure. After 1 year and at the end of follow-up (mean 39 ± 21 months), 81% and 58% of patients were free of VT. No differences were observed between patients with and without specific clinical VT substrate identification. Univariate analysis identified the left ventricular ejection fraction, VT cycle length (VTCL), infarct location (inferior vs anterior), and dense scar area as predictors of VT recurrence, and Cox analysis identified VTCL (hazard ratio 0.42, p <0.001) and dense scar area (hazard ratio 2.65, p <0.0006) as independent predictors. No patients with dense scar area ≤25 cm(2) and VTCL >350 ms had recurrences. In conclusion, CEVTSA is safe and effective, even in patients without clinical VT substrate identification. Scar area and VTCL are valuable predictors of VT recurrence.

Differences in ventriculoatrial intervals during entrainment and tachycardia: a simpler method for distinguishing paroxysmal supraventricular tachycardia with long ventriculoatrial intervals.

INTRODUCTION: Usefulness of the interval between the last pacing stimulus and the last entrained atrial electrogram (SA) minus the tachycardia ventriculoatrial (VA) interval in the differential diagnosis of supraventricular tachycardias with long (>100 ms) VA intervals has not been prospectively studied in a large series of patients. Our objective was to assess the usefulness of the difference SA-VA in diagnosing the mechanism of those tachycardias in patients without preexcitation. The results were compared with those obtained using the corrected return cycle (postpacing interval-tachycardia cycle length-atrioventricular [AV] nodal delay). METHODS AND RESULTS: We included 314 consecutive patients with inducible sustained supraventricular tachycardias with VA intervals >100 ms undergoing an electrophysiologic study. Atrial tachycardias were excluded. Tachycardia entrainment was attempted through pacing trains from right ventricular apex. The SA-VA difference and the corrected return cycle were calculated for every patient. Electrophysiologic study revealed 82 atypical AV nodal reentrant tachycardias (AVNRT) and 237 AV reentrant tachycardias (AVRT) using septal (n = 91) or free-wall (n = 146) accessory pathways (APs). A SA-VA difference >110 ms identified an atypical AVNRT with sensitivity, specificity, positive and negative predictive values of 99%, 98%, 95%, and 99.5%, respectively. Similarly, these values were 88%, 83%, 77%, and 92% for SA-VA difference <50 ms in identifying AVRT through a septal versus free-wall AP. The SA-VA difference showed higher accuracy in septal AP identification than that obtained using the corrected return cycle. CONCLUSION: The difference SA-VA provides a simpler electrophysiologic maneuver that reliably differentiates atypical AVNRT from AVRT regardless of concealed AP location.

EGC diagnosis of paroxysmal supraventricular tachycardias in patients without preexcitation.

This review is aimed at discussing the diagnostic value of the different electrocardiographic criteria so far described in the differential diagnosis of the major forms of paroxysmal supraventricular tachycardias (PSVTs). The predictive value of different combinations of these independent electrocardiographic (ECG) signs in distinguishing atrioventricular reentrant tachycardias (AVRTs) through a concealed accessory pathway (AP) versus atrioventricular nodal reentrant tachycardias (AVNRTs) are discussed in detail. In addition, the adjunctive diagnostic value of simple, bedside clinical variables and their combinations to the ECG interpretation in differentiating both tachycardia mechanisms is also reviewed.

Noninvasive identification of ventricular tachycardia-related conducting channels using contrast-enhanced magnetic resonance imaging in patients with chronic myocardial infarction: comparison of signal intensity scar mapping and endocardial voltage mapping.

OBJECTIVES: We performed noninvasive identification of post-infarction sustained monomorphic ventricular tachycardia (SMVT)-related slow conduction channels (CC) by contrast-enhanced magnetic resonance imaging (ceMRI). BACKGROUND: Conduction channels identified by voltage mapping are the critical isthmuses of most SMVT. We hypothesized that CC are formed by heterogeneous tissue (HT) within the scar that can be detected by ceMRI. METHODS: We studied 18 consecutive VT patients (SMVT group) and 18 patients matched for age, sex, infarct location, and left ventricular ejection fraction (control group). We used ceMRI to quantify the infarct size and differentiate it into scar core and HT based on signal-intensity (SI) thresholds (>3 SD and 2 to 3 SD greater than remote normal myocardium, respectively). Consecutive left ventricle slices were analyzed to determine the presence of continuous corridors of HT (channels) in the scar. In the SMVT group, color-coded shells displaying ceMRI subendocardial SI were generated (3-dimensional SI mapping) and compared with endocardial voltage maps. RESULTS: No differences were observed between the 2 groups in myocardial, necrotic, or heterogeneous mass. The HT channels were more frequently observed in the SMVT group (88%) than in the control group (33%, p < 0.001). In the SMVT group, voltage mapping identified 26 CC in 17 of 18 patients. All CC corresponded, in location and orientation, to a similar channel detected by 3-dimensional SI mapping; 15 CC were related to 15 VT critical isthmuses. CONCLUSIONS: SMVT substrate can be identified by ceMRI scar heterogeneity analysis. This information could help identify patients at risk of VT and facilitate VT ablation.

Combined evaluation of bedside clinical variables and the electrocardiogram for the differential diagnosis of paroxysmal atrioventricular reciprocating tachycardias in patients without pre-excitation.

OBJECTIVES: The aim of this study was to assess the independent predictive contribution to the electrocardiogram (ECG) of bedside clinical variables to distinguish the major forms of paroxysmal supraventricular tachycardias. BACKGROUND: Atrioventricular nodal re-entrant tachycardias (AVNRTs) and orthodromic reciprocating tachycardias (ORTs), through concealed accessory pathways, are major mechanisms of paroxysmal atrioventricular re-entrant tachycardias. METHODS: We prospectively included 370 consecutive patients undergoing an electrophysiologic study for paroxysmal, regular, narrow-QRS complex tachycardias without pre-excitation in sinus rhythm. A diagnostic interpretation of ECG recordings was performed by 2 observers blinded to invasive diagnosis used as gold standard. The independent diagnostic contribution of basic clinical variables from a 7-item questionnaire was analyzed alone and in combination with the ECG interpretation by stepwise logistic regression. RESULTS: AVNRTs and ORTs were demonstrated in 262 and 108 patients, respectively. Age at symptom onset (odds ratio [OR]: 1.27), presence of palpitations in the neck (OR: 3.54), and female sex (OR: 2.96) (all p = 0.0001) were the clinical variables with significant diagnostic power for AVNRT diagnosis. These variables were selected by the logistic model as predictors of the tachycardia diagnosis when the ECG interpretation was included in the analysis (C statistic = 0.81 vs. 0.75 with clinical variables alone; p = 0.003). Neck palpitation was the only predictor of AVNRT when positive ECG findings were lacking. CONCLUSIONS: Age at the onset of symptoms, sensation of rapid regular pounding in the neck during tachycardia, and female sex are the only significant clinical variables in the differential diagnosis of paroxysmal atrioventricular reciprocating tachycardias in patients without pre-excitation in sinus rhythm. Their consideration adds significant diagnostic information to the ECG.

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

Identification of conduction gaps in the ablation line during left atrium circumferential ablation: facilitation of pulmonary vein disconnection after endpoint modification according to electrogram characteristics.

BACKGROUND: Left atrium circumferential ablation (LACA) is a simple, effective treatment for atrial fibrillation (AF), but many pulmonary veins (PV) are not disconnected because of conduction gaps (CG) in the ablation line. OBJECTIVE: This study defined the electrogram characteristics at the CGs and at the PV- left atrium (LA) connection site and assessed the effect of modifying ablation endpoints at these sites. METHODS: Forty consecutive patients underwent LACA. Phase I: In 15 patients, electrogram characteristics at the LA-PV connection, CGs at the ablation line, and PV disconnection rate were evaluated during LACA with current ablation endpoints (80% reduction in electrogram amplitude or 0.1 mV). Phase II: 25 patients underwent LACA with modified endpoints according to the results of Phase I. RESULTS: Phase I: Fifty-five PVs were analyzed, 17 during sinus rhythm (SR) and 38 during AF. LA-PV connections were characterized by multicomponent electrograms (ME) without an isoelectric line (0.45 +/- 0.43 mV, 77 +/- 21 ms). After LACA, 55% of PVs were disconnected. In 85% of nondisconnected veins, ME (0.11 +/- 0.02 mV) were recorded at CGs where ablation caused PV disconnection. Phase II: Ninety-five PVs, 52 during AF and 43 during SR underwent LACA with modified ablation endpoints at ME sites: Disappearance of late component and voltage reduction to <0.05 mV. Eighty-five per cent of PV were disconnected (95% in SR and 77 % in AF, P <.01). CONCLUSION: MEs identify LA-PV connections and CGs. Modification of ablation endpoints at these sites should facilitate PV disconnection during LACA.

Rate-related changes in QRS morphology in patients with fixed bundle branch block: implications for differential diagnosis of wide QRS complex tachycardia.

AIMS: To analyse QRS morphology in response to rapid atrial pacing (RAP) and supraventricular tachycardia (SVT) in patients with pre-existing bundle branch block (BBB). METHODS AND RESULTS: We prospectively studied 59 patients in sinus rhythm (SR), with QRS > or = 120 ms, and no pre-excitation. Trains of RAP were introduced at increasing rates until atrioventricular block. QRS during SR and last QRS complex of each RAP train were compared on the 12-leads. Previously described criteria for minor and major configuration differences were used to identify QRS changes. During RAP minor QRS changes were seen in 22 (37%) and major changes in 23 (39%) subjects. One patient showed major axis shifts and no one showed a change to the contralateral BBB pattern. QRS changes were significantly and independently related to RAP rate and type of BBB (more frequent if right-BBB). Of 14 subjects (24%) with SVT, 13 displayed the same QRS changes during RAP. CONCLUSION: In patients with organic BBB, important changes in QRS morphology, except for a change in the contralateral BBB, can appear during RAP and SVT. Thus, in these patients, a change in QRS morphology during tachycardia does not necessarily imply that it is ventricular tachycardia.

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)