Analysis During Sinus Rhythm of Critical Sites in Reentry Circuits of Postinfarction Ventricular Tachycardia

Background: Critical sites within reentry circuits of postinfarction ventricular tachycardia (VT) were identified during sinus rhythm (SR) and VT to determine whether electrogram characteristics during SR may be helpful in identifying successful ablation sites. Methods: In 33 patients (mean age 67 ± 11 yrs) with prior infarction, mapping and radiofrequency (RF) catheter ablation of 57 hemodynamically-tolerated VT's (cycle length 478 ± 96) were performed. The morphologies of electrograms (EGM) at sites of concealed entrainment (CE) were compared during SR and VT. RF energy was delivered at 94 sites (51 successful and 43 unsuccessful ablation sites). Results: During SR, isolated potentials (IP), but not late potentials (LP) recorded via the mapping catheter, were associated with successful ablation. At 29/39 sites with an IP during sinus rhythm, an isolated diastolic potential (IDP) also was present during VT, whereas at 4 sites IP's were present only during SR (p < 0.001). At 11/29 sites where isolated potentials were present during SR and VT, the morphology of the isolated potential during VT and SR was similar; and all but one of these sites were successful ablation sites (p = 0.01). The EGM amplitude during VT correlated with the amplitude during SR (R = 0.9, p < 0.001). An identical pacemap was present during SR at 33/94 sites; this was not associated with successful ablation. Conclusion: SR mapping may be helpful in identifying critical sites of reentry in postinfarction VT. At sites within the reentry circuit, characteristics of sinus rhythm EGM's that are associated with successful ablation include the presence of IP's, but not the presence of LP's.     

Localization of the isthmus in reentrant circuits by analysis of electrograms derived from clinical noncontact mapping during sinus rhythm and ventricular tachycardia

INTRODUCTION: New methods for electrogram analysis accurately estimated reentrant circuit isthmus location and shape in a canine model. It was hypothesized that these methods also would locate reentrant circuits causing clinical ventricular tachycardia (VT). METHODS AND RESULTS: Intracardiac electrogram recordings, obtained with a noncontact mapping system, were analyzed retrospectively from 14 patients with reentrant VT who had undergone successful radiofrequency ablation for prevention of VT initiation. Unipolar electrograms from 256 uniformly distributed endocardial sites were reconstructed by mathematical transformation. Twenty-seven tachycardias were mapped; 15 (in 11 patients) had a complete endocardial reentrant circuit with a figure-of-eight conduction pattern. During sinus rhythm, the location and axis of the slowest and most uniform conduction in the region of latest endocardial activation (the primary axis), the limits of which were defined as boundaries with >15 ms difference in electrogram duration between contiguous recordings, identified the location and shape of the reentrant circuit isthmus with a mean sensitivity compared with activation mapping of 79.3% and a mean specificity of 97.6%. The midpoint of a theoretical "estimated best ablation line" drawn perpendicular to the primary axis of activation, spanning the estimated isthmus location was within 1.3 +/- 0.2 cm (mean distance +/- SD) of the actual ablation site that terminated tachycardia. Analysis of VT electrograms, based on time shifts in the far-field component of the local electrogram when cycle length changed (piecewise linear adaptive template matching [PLATM] method) in 5 of the cases, accurately estimated the time interval between activation at the recording site and the circuit isthmus slow conduction zone where the effective ablation lesion had been placed, which is proportional to the distance between the two locations (mean difference compared with activation mapping: +/-37.3 ms). CONCLUSION: In selected patients with VT who have a complete endocardial circuit, isthmus location and shape can be discerned by analysis of sinus rhythm or tachycardia electrograms, and an effective ablation site can be predicted without the need to construct activation maps of reentrant circuits.     

Identification of successful catheter ablation sites in patients with ventricular tachycardia based on electrogram characteristics during sinus rhythm

BACKGROUND: Zones of slow conduction facilitate reentry, the major mechanism of ventricular tachycardia (VT) after myocardial infarction (MI). Identification of these zones during sinus rhythm (SR) is desirable for radiofrequency (RF) catheter ablation of VT. Local conduction velocity may correlate with electrogram duration. OBJECTIVES: The purpose of this study was to revise the definition of normal electrogram characteristics and to reevaluate the significance of low-amplitude, long-duration electrograms recorded during SR to select RF catheter ablation sites in patients with VT. METHODS: Electroanatomic mapping was performed during SR in 10 control patients with normal left ventricles (LVs) and in 10 patients with stable VT after MI. From the controls, reference values for electrogram amplitude, duration (first peak to last peak distance), and fragmentation (positive deflection) were derived. In patients after MI, areas with signals exceeding these values were annotated and related to successful ablation sites. RESULTS: Ninety-five percent of normal LV electrograms were > or =1.0 mV and < or =28 ms (range 5-39 ms) and all had < or =4 deflections. Based on these results, cutoff values were set at 1 mV, four deflections, and 40 ms. In infarcted hearts, 653 electrograms (44%) were <1.0 mV and of these, 303 were > or =40 ms with >4 deflections and restricted to circumscribed areas. Twenty-seven of 28 targeted VTs remained noninducible after RF catheter ablation within these areas, resulting in 86% sensitivity and 94% specificity for low-amplitude, long-duration electrograms predicting successful ablation sites. CONCLUSION: Identification of successful RF target areas during SR in patients with VT is feasible with high sensitivity and specificity using a mapping strategy based on voltage and duration criteria.     

Characteristics of Local Electrograms with Diastolic Potentials: Identification of Different Components of Return Pathways in Ventricular Tachycardia

Background:Diastolic potentials are often sought as a possible site for catheter ablation in post-infarct ventricular tachycardia. However, delivery of energy at such sites is often unsuccessful. The purpose of this study was to determine the characteristics of local electrograms with diastolic potentials and to identify activation pattern which might indicate the critical portion of the return path of the ventricular tachycardia reentry circuit.Methods: In 17 patients with post-myocardial infarction ventricular tachycardia, 30 ventricular tachycardias were mapped with an 112 bipolar endocardial balloon at the time of surgery. Diastolic mapping of the return tract in ventricular tachycardia was performed. Four activation patterns were observed (15 figure 8 patterns, 2 circular patterns, 2 biregional patterns and 11 monoregional patterns). Of 3,360 local electrograms, 207 (6.2%) demonstrated a diastolic potential in ventricular tachycardia. They were classified into following four categories, based on the appearance and timing of the systolic component. Type A-1 electrogram: systolic activation was of low amplitude (<2 mV) and was prolonged (100 msec), but preceded the onset of the surface QRS in ventricular tachycardia. Type A-2 electrogram: systolic activation was of low amplitude, was prolonged, but followed the onset of the surface QRS. Type B electrogram: systolic electrogram was fractionated, but relatively normal amplitude (2.0–3.6 mV). Type C electrogram: systolic electrogram was almost normal.Results: Of all electrograms with diastolic potentials, three type A-1 electrograms (1.4%) were located at the exit of the return pathway, 11 type A-1 electrograms (5.3%) were located at the pre-exit site. No type A-1 was found at an entrance/bystander area. 21 type A-2 electrograms (10.1%) were at the pre-exit and 83 type A-2 electrograms (40.2%) were located at the entrance/bystander area, but such electrograms were never found at the exit site. 71 type B electrograms (34.3%) and 18 type C electrograms (8.7%) were located at the entrance/bystander area. To distinguish the type A-2 electrograms at the pre-exit site from those at the entrance/bystander area, the diastolic potential to QRS interval was measured. This interval at the pre-exit was significantly shorter than that at the entrance/bystander area (–47.2 ± 10.7 vs –96.3 ± 31.3 msec, p = 0.0001).Conclusion: Type A-1 electrograms indicated the exit or pre-exit site of return pathway. Type A-2 electrograms with diastolic potential to QRS interval <–50 msec indicated the pre-exit site. However, the other types of local electrograms with diastolic potential did not indicate the critical portion of the ventricular tachycardia circuit. These observations may be helpful during catheter mapping and ablation of patients with post-infarct ventricular tachycardia.Condensed Abstract. Diastolic potentials are often sought to direct catheter ablation in post-infarct ventricular tachycardia. We investigated the characteristics of local electrograms showing diastolic activity in an attempt to determine whether critical portions of the ventricular tachycardia circuit could be identified by a typical signature. In 17 patients with a remote myocardial infarction, 30 ventricular tachycardias were mapped with 112 bipolar endocardial balloon at the time of surgery. Diastolic potentials in association with low amplitude (<2 mV) and prolonged (100 msec) systolic electrograms preceding the onset of QRS were found at the exit site and pre-exit site of return pathway. A similar systolic electrogram occurring after QRS onset with a diastolic potential to QRS interval of <–50 msec was found at the pre-exit site. However, other local electrograms with diastolic activity were at sites remote from the exit or pre-exit of the return pathway. These observations may be helpful during catheter mapping and ablation in patients with ventricular tachycardia.     

Relative Timing of Isolated Potentials During Postinfarction Ventricular Tachycardia and Sinus Rhythm

BACKGROUND: In postinfarction patients, isolated potentials separated by an isoelectric segment from the ventricular electrogram indicate areas of block. Isolated potentials can be recorded during both sinus rhythm and ventricular tachycardia (VT). In an attempt to differentiate bystander pathways from critical sites within a reentry circuit, we compared the relative timing of isolated potentials during VT and sinus rhythm. METHODS: In 19 patients (mean age 68 +/- 6 years) with postinfarction VT who were referred for VT ablation, mapping was performed in the presence and absence of VT. Forty-three sites at which there was concealed entrainment during 35 VT's (mean cycle length 469 +/- 74 ms) displayed an isolated potential separated from the main portion of the ventricular electrogram by an isoelectric segment of >/=30 msec in the presence and absence of VT. The interval between the ventricular electrogram and the isolated potential was measured during VT and baseline rhythm, and the absolute difference (DeltaIPI) was calculated. The DeltaIPI was significantly greater at effective ablation sites (119 +/- 69 ms) than at ineffective ablation sites (30 +/- 28 ms, p < 0.001). The positive predictive value of a DeltaIPI > 85 ms for an effective ablation site was 100%. CONCLUSION: At sites of concealed entrainment, an absolute difference >85 ms between the isolated potential intervals during sinus rhythm and VT is highly specific for a critical area of the VT reentry circuit in post-infarction patients.     

Focal atrial tachycardia originating from the left atrial appendage: electrocardiographic and electrophysiologic characterization and long-term outcomes of radiofrequency ablation

Introduction: This study sought to investigate electrophysiologic characteristics and radiofrequency ablation (RFA) in patients with focal atrial tachycardia (AT) arising from the left atrial appendage (LAA).
Methods: This study included seven patients undergoing RFA with focal AT. Activation mapping was performed during tachycardia to identify an earlier activation in the left atria and the LAA. The atrial appendage angiography was performed to identify the origin in the LAA before and after RFA.
Results: AT occurred spontaneously or was induced by isoproterenol infusion rather than programmed extrastimulation and burst atrial pacing in any patient. The tachycardia demonstrated a characteristic P-wave morphology and endocardial activation pattern. The P wave was highly positive in inferior leads in all patients. Lead V₁ showed upright or biphasic (±) component in all patients. Lead V₂–V₆ showed an isoelectric component in five patients or an upright component with low amplitude (<0.1 mV) in two patients. Earliest endocardial activity occurred at the distal coronary sinus (CS) ahead of P wave in all seven patients. Mean tachycardia cycle length was 381 ± 34 msec and the earliest endocardial activation at the successful RFA site occurred 42.3 ± 9.6 msec before the onset of P wave. RFA was acutely successful in all seven patients. Long-term success was achieved in seven of the seven over a mean follow-up of 24 ± 5 months.
Conclusions: The LAA is an uncommon site of origin for focal AT (3%). There were consistent P-wave morphology and endocardial activation associated with this type of AT. The LAA focal ablation is safe and effective. Long-term success was achieved with focal ablation in all patients.     

起源于左主动脉窦的室性心律失常的心电生理特点和消融治疗

目的报道21例起源于左主动脉窦的室性心律失常的心电生理特征和射频消融疗效。方法分析术前体表心电图(ECG)和Holter心电图室性早搏(VPB)或室性心动过速(VT)的形态特点,测量V1导联r波振幅和时限,计算r与QRS波的振幅和时限比值。术中在自发VPB或VT时标测主动脉窦,以局部室波最早部位放电消融,并进行冠状动脉造影,测量消融靶点距左冠状动脉口的距离。结果21例均有频发VPB,8例有反复短阵VT。VPB或VT在Ⅱ、Ⅲ、aVF导联为高大R波,V1导联r波振幅为QRS波的1/3或以上,r波时限87.5±9.5 m s,为QRS波时限的1/2以上。V3导联多为R s形,V5、V6导联无S波。有效消融靶点局部电图室波明显超前ECG的QRS波(36.2±12.2 m s),距左冠状动脉口部1 cm左右。有效靶点放电2~8 s VPB消失或VT终止。结论起源于左主动脉窦的VPB或VT其Ⅱ、Ⅲ、aVF导联为高大R波,V1导联r波振幅高(≥1/3QRS波),时限宽(≥1/2QRS波);主动脉窦激动顺序标测可安全有效地指导消融治疗。     

Catheter Ablation of Idiopathic Left Ventricular Tachycardia with Multiple Breakthrough Sites Guided by an Electroanatomical Mapping System

Idiopathic ventricular tachycardia (VT) has been considered to be amenable to radiofrequency catheter ablation guided by Purkinje potentials. However, there appear to be various types of reentrant circuits associated with this VT deduced from the results of the successful radiofrequency catheter ablation cases. We describe in this report a patient with idiopathic left ventricular tachycardia which was electrically inducible and verapamil sensitive. Multiple earliest ventricular activation sites during tachycardia were detected with electroanatomical mapping using the CARTO system. Multiple applications at these sites failed to eliminate the VT. The earliest Purkinje potential was recorded at least 1.5[emsp4 ]cm away from the earliest ventricular activation sites, and the radiofrequency current application at this site resulted in the complete abolition of this VT. The reentrant circuit of this tachycardia seemed to have multiple breakthrough sites to the ventricular myocardium, which were distant from the requisite part of the reentrant circuit of this VT involving the Purkinje fiber network conduction system.     

Mechanism of Ventricular Tachycardia Termination by Pacing at Left Ventricular Sites in Patients with Coronary Artery Disease

Objective: The mechanism by which pacing terminates ventricular tachycardia (VT) may depend on the location of the pacing site relative to the reentry circuit. The purpose of this study was to compare the mechanisms by which pacing terminates VT at left ventricular (LV) sites with and without concealed entrainment (CE) in patients with prior myocardial infarction. Methods and Results: LV mapping was performed in 29 patients (26 men, 3 women, mean age 67±11 years, ejection fraction 0.28±0.11) with 55 hemodynamically-tolerated VTs (mean cycle length 478±92 msec). A total of 408 pacing trains were delivered at 102 sites with CE. Radiofrequency catheter ablation was successful in 41 of 55 VT's. At sites with concealed entrainment, VT was terminated by pacing at 17/41 (41%) successful and at 4/61 (7%) unsuccessful ablation sites (p<0.01). Termination without global ventricular capture was the most frequent termination mode (10/21), followed by termination with orthodromic (4/21) and non-orthodromic capture (7/21). Conclusion: In patients with prior myocardial infarction, pacing at sites of CE during VT usually terminates VT either without global capture or by orthodromic capture. Termination of VT by pacing without global capture or with orthodromic capture at sites of CE suggests that the site is within a critical area of the reentry circuit.     

Catheter ablation of ventricular arrhythmias arising from the right ventricular septum close to the His bundle: features of the local electrogram at the optimal ablation site

Ablation of Para‐Hisian Ventricular Arrhythmias . Introduction: The characteristics of the local electrogram at the optimal ablation site of ventricular arrhythmias (VAs) originating from the right ventricle close to the His bundle (HB) region have rarely been described. Methods and Results: Among 190 consecutive patients with idiopathic VAs with left bundle branch block morphology and inferior‐axis deviation, 16 were found to have successful ablation site in the right ventricle close to the HB region (para‐Hisian group). The electrophysiologic data were compared between the patients in the para‐Hisian group and those with VAs arising from the right ventricular (RV) outflow tract (RVOT group). The distal bipolar electrogram at the successful ablation sites in the para‐Hisian group exhibited a significantly greater R‐wave duration, lower R‐wave amplitude, and slower upright deflection of the initial R wave than did those in the RVOT group (all P < 0.001). In the para‐Hisian group, a total of 56 radiofrequency (RF) energy applications were delivered, of which the local electrograms at 16 successful and 40 unsuccessful ablation sites were reviewed. High‐frequency R‐wave potentials of the bipolar electrogram were present in 14 (88%) of the successful ablation sites. An R‐wave duration of greater than 34 ms had a discriminatory power for indicating the site of a successful ablation (area under the receiver–operator characteristics curve 0.90, sensitivity 94%, specificity 80%). Conclusions: The successful ablation site of the para‐Hisian VAs had distinctive local electrogram characteristics. A longer R‐wave duration of the bipolar electrogram with high‐frequency potentials could be a novel predictor of a successful ablation. (J Cardiovasc Electrophysiol, Vol. 22, pp. 878‐885, August 2011)     

Reproducibility of Bipolar Endocavitary Electrogram Measurements at sites of Radiofrequency Energy Delivery in Patients with the Wolff-Parkinson-White Syndrome

Background: Radiofrequency ablation of atrioventricular accessory pathway is widely used to cure patients with the Wolff-Parkinson-White syndrome. The site of successful ablation is determined using electrophysiological parameters, endocavitary bipolar electrogram measurements being the most commonly used. Interobserver reproducibility of these measurements may limit the reliability of ablation criteria based upon bipolar measurements only but, to our knowledge, this reproducibility has not been evaluated so far. Such was the aim of this study.Methods: Three independent observers reviewed the bipolar electrograms recorded at sites were radiofrequency energy was delivered (successfully or not) in 28 consecutive patients with the Wolff-Parkinson-White syndrome. In each tracing, 4 intervals were measured: (1) A0V0 (onset of the atrial electrogram to onset of the ventricular electrogram), (2) AaVa (activation time of the atrial electrogram to activation time of the ventricular electrogram), (3) V0-QRS (onset of the ventricular electrogram to onset of delta wave on the surface ECG) and (4) Va-QRS (activation time of the ventricular electrogram to onset of delta wave on the surface ECG).Results: The interobserver reproducibility was low since only 50% of A0V0 intervals were measured with an interobserver difference lower than 10ms and up to 43% of Va-QRS intervals were measured with an interobserver difference greater than 30ms. The reproducibility of interval measurement was graded from the highest to the lowest as follows: A0V0, AaVa, V0-QRS and Va-QRS (Chi-square statistic, 2= 71.72, p < 0.0001). Kappa values were lower than 0.40, indicating a poor interobserver reproducibility.Conclusions: Our study suggests that interobserver reproducibility ofonly bipolar electrograms interval measurements at sites of radiofrequency ablation of atrioventricular accessory pathway is poor, which limits the reliability of bipolar criteria to predict a successful ablation site.     

Endocardial and Epicardial Ablation Guided by Nonsurgical Transthoracic Epicardial Mapping to Treat Recurrent Ventricular Tachycardia

Nonsurgical Epicardial Ablation. Introduction : An epicardial site of origin of ventricular tachycardia (VT) may explain unsuccessful endocardial radiofrequency (RF) catheter ablation. A new technique to map the epicardial surface of the heart through pericardial puncture was presented recently and opened the possibility of using epicardial mapping to guide endocardial ablation or epicardial catheter ablation. We report the efficacy and safety of these two approaches to treat 10 consecutive patients with VT and Chagas' disease.
Methods and Results : Epicardial mapping was carried out with a regular steerable catheter introduced into the pericardial space. An epicardial circuit was found in 14 of 18 mapable VTs induced in 10 patients. Epicardial mapping was used to guide endocardial ablation in 4 patients and epicardial ablation in 6. The epicardial earliest activation site occurred 107 ± 60 msec earlier than the onset of the QRS complex. At the epicardial site used to guide endocardial ablation, earliest activation occurred 75 ± 55 msec before the QRS complex. Epicardial mid-diastolic potentials and/or continuous electrical activity were seen in 7 patients. After 4.8 ± 2.9 seconds of epicardial RF applications, VT was rendered noninducible. Hemopericardium requiring drainage occurred in 1 patient; 3 others developed pericardial friction without hemopericardium. Patients remain asymptomatic 5 to 9 months after the procedure. Interruption during endocardial pulses occurred after 20.2 ± 14 seconds (P = 0.004), hut VT was always reinducible and the patients experienced a poor outcome.
Conclusion : Epicardial mapping does not enhance the effectiveness of endocardial pulses of RF. Epicardial applications of RF energy can safely and effectively treat patients with VT and Chagas' disease.     

Clinical Value of the Postpacing Interval for Mapping of Ventricular Tachycardia in Patients with Prior Myocardial Infarction

Postpacing Interval. Introduction: The postpacing interval (PPI) has been used to discriminate bystander sites from critical sites within a ventricular tachycardia (VT) reentry circuit, with a PPI that is similar to the VT cycle length (CL) being indicative of a site within the reentry circuit. The purpose of this study was to assess the clinical value of the PPI for identifying effective target sites for ablation of VT at sites of concealed entrainment in patients with prior myocardial infarction.
Methods and Results: In 24 patients with coronary artery disease and a past history of myocardial infarction, 36 VTs with a mean CL of 483 ± 80 msec (± SD) were mapped and targeted for radiofrequency (RF) ablation. The only criterion used to select target sites for ablation was concealed entrainment. In a post hoc analysis, the PPI was measured at 47ineffective and 26 effective ablation sites. The mean PPI-VTCL difference at the 26 effective sites(114 ± 137 msec) did not differ significantly from the mean at the 47 ineffective sites (177 ± 161msec; P = 0.1). The sensitivity of a PPI-VTCL difference ≤ 30 msec for identifying an effective ablation site was 46%, the specificity 64%, the positive predictive value 41%, and the negative predictive value 68%.
Conclusion: The PPI-VTCL difference is not useful for discriminating between sites of concealed entrainment that are within or outside of a VT reentry circuit in patients with prior infarction. Therefore, in patients with prior infarction, the PPI is not clinically useful for identifying sites of concealed entrainment at which RF ablation should or should not beat tempted.     

Spatial resolution of pacemapping and activation mapping in patients with idiopathic right ventricular outflow tract tachycardia

BACKGROUND: The purpose of this study was to compare the spatial resolution of activation mapping and pacemapping in patients undergoing ablation of idiopathic ventricular tachycardia (VT) arising from the right ventricular outflow tract (RVOT). A direct comparison of the two techniques has not been undertaken. METHODS AND RESULTS: Electroanatomical activation maps of the RVOT were obtained during VT in 15 patients. Pacemaps were obtained from multiple sites, tagged on the activation map, and scored according the degree of concordance between the paced QRS configuration and that of VT. The site of successful ablation was considered the VT site of origin. Initial endocardial activation away from the site of origin was rapid; the mean area of myocardium activated within the first 10 msec (early activation area, EAA) was 3.0 +/- 1.6 cm(2) (range: 1.3-6.4 cm(2)). Best pacemap scores were always obtained adjacent to the site of origin. Pacemap concordance, and the probability of an exact pacemap match significantly decreased with increasing distance of the pacing site from the site of origin (P < 0.01). All patients had more than one pacing site yielding a best pacemap score. The greatest distance between such sites in an individual patient ranged from 11 to 26 mm (mean: 18 +/- 5 mm), and was strongly correlated with the size of the EAA (r = 0.77, P < 0.001). CONCLUSIONS: Pacemapping and activation mapping provide similar localizing information. The spatial resolution of each technique is modest, varies between patients, and may be optimized by three-dimensional data display.     

Dynamic changes in electrogram morphology at functional lines of block in reentrant circuits during ventricular tachycardia in the infarcted canine heart: a new method to localize reentrant circuits from electrogram features using adaptive template matching

INTRODUCTION: Fractionated, low-amplitude or long-duration electrograms have limited specificity for locating reentrant circuits causing ventricular tachycardia (VT). In this study a new method is described, adaptive template matching (ATM), based on the quantification of beat-to-beat changes in electrograms, for locating functional reentrant circuits that are relatively stable and cause monomorphic VT. METHODS AND RESULTS: Monomorphic VTs were induced in 4-day-old infarcted canine hearts by programmed stimulation and reentrant circuits mapped in the epicardial border zone with a 196 or 312 bipolar electrode array. For ATM analysis, a template electrogram from each electrode, during an early cycle, was matched with all subsequent (input) electrograms at the same site by weighting the inputs of amplitude, duration, average baseline, and phase lag. The mean square error (MSE) between template and input was the criterion used to adapt the weights, and was also a measure of changes in electrogram shape that occur from cycle to cycle. The variance of each of the weighting parameters at all electrode sites were plotted on a representation of the electrode array, and the location of the functional lines of block bounding the central common pathway of reentrant circuits with figure-of-eight characteristics, overlaid on the ATM map. Peaks of high variance were found to be coincident with functional lines of block during all tachycardia episodes. CONCLUSION: Specific beat-to-beat changes in electrograms occur at functional lines of block in reentrant circuits that can be quantified by ATM analysis, suggesting that these regions might be located without activation mapping. The method might be useful to guide ablation catheter position.     

Isolated potentials during sinus rhythm and pace-mapping within scars as guides for ablation of post-infarction ventricular tachycardia.

OBJECTIVES: The purpose of this study was to identify ventricular tachycardia (VT) isthmus sites by pace-mapping within scar tissue and to identify electrogram characteristics that are helpful in identifying VT isthmus sites during sinus rhythm (SR). BACKGROUND: Pace-mapping has been used in the scar border zone to identify the exit site of post-infarction VT. METHODS: In 19 consecutive patients (18 men, mean age 66 +/- 9 years, mean ejection fraction 0.24 +/- 0.12) with post-infarction VT, a left ventricular voltage map was generated during SR. Pace-mapping was performed at sites with abnormal electrograms or isolated potentials. Radiofrequency ablation was performed at isthmus sites as defined by pace-mapping (perfect pace-map = 12/12 matching electrocardiogram leads; good pace-map = 10/12 to 11/12 matching electrocardiogram leads) and/or entrainment mapping. RESULTS: A total of 81 VTs (mean cycle length 396 +/- 124 ms) were inducible. In 16 of the 19 patients, a total of 41 distinct isthmus areas of 41 distinct VTs were identified and successfully ablated. All but one displayed isolated potentials during SR. Furthermore, 22 of the 81 VTs (27%) for which no isthmus was identified became noninducible after ablation of a targeted VT. The 16 patients in whom > or =1 isthmus was identified and ablated were free of arrhythmic events during a mean follow-up of 10 months. CONCLUSIONS: During SR, excellent or good pace-maps at sites of isolated potentials within areas of scar identify areas of fixed block that are protected and part of the critical isthmus of post-infarction VT. Shared common pathways might explain why non-targeted VTs might become noninducible after ablation of other VTs.     

Signal-Aver aged Intracardiac Electrograms:

Signal Averaged Intracardiac Electrograms. Introduction : In patients with manifest accessory pathways, Kent potentials are often difficult to identify even at sites of successful catheter ablation, due largely to signal noise and catheter instability. We hypothesized that signal averaging the intracardiac electrogram recorded from the ablation catheter over a number of beats would improve the signal-to-noise ratio of the electrogram and aid in the detection of Kent potentials at accessory pathway locations.
Methods and Results : We retrospectively analyzed distal-pair electrograms recorded from 9 successful, 6 transiently successful, and 10 failed ablation sites in 10 patients with manifest accessory pathways who underwent catheter ablation. We developed custom software to finely align 20 to 30 consecutive sinus beats and compute the signal average of the electrogram (SAE) for each site. Kent potentials were classified as probable, possible, or absent in the raw ablation site electrogram and the SAE base on morphologic criteria. A measure of beat-to-beat signal instability, the variability quotient (VQ), was also computed for each site. Probable Kent potentials were found in the raw ablation site electrogram at only 2 of the 15 successful and transiently successful sites, but were found in the SAE at 10 of these sites (P = 0.008). Eight of the 9 successful sites had VQ < 0.2, suggesting stable catheter-tissue contact, while 3 of the 6 transiently successful sites had VQ > 0.2, indicating unstable contact.
Conclusions : Signal averaging the intracardiac ablation site electrogram enhances detection of Kent potentials at accessory pathway locations. Catheter instability can be quantified by signal variability analysis and, when high, may predict lack of successful ablation even at sites where Kent potentials are present.     

The effect of electrogram duration on quantification of complex fractionated atrial electrograms and dominant frequency

Introduction: Sites of complex fractionated atrial electrograms (CFAEs) and highest dominant frequency (DF) have been proposed as critical regions maintaining atrial fibrillation (AF). This study aimed to determine the minimum electrogram recording duration that accurately characterizes CFAE or DF sites for ablation without unduly lengthening the procedure.
Methods and Results: Fourteen patients with AF undergoing catheter ablation had high-density (498 ± 174 points) biatrial mapping performed during AF before ablation. At each point, 8-second electrograms were recorded. CFAE characterization using the NavX software provided a representation of electrogram complexity (CFE-mean). CFE-mean for each point from 7-, 6-, 5-, 4-, 3-, 2-, and 1-second subsamples were compared with the index 8-second CFE-mean. Offline spectral analysis defined DF as the frequency with greatest power, and DF of subsamples were compared with index DF. Index 8-second electrogram CFE-mean was 114 ± 20 ms for right atria and 102 ± 17 ms for left atria (P = 0.01); DF was 5.7 ± 0.8 Hz for right atria and 6.0 ± 0.8 Hz for left atria (P = 0.02). Means from shorter electrograms were nonsignificantly decreased for CFE-mean and overestimated for DF (P < 0.001). Mean absolute differences between subsampled and index values ranged from 3.3 to 20.1 ms for CFE-mean and 0.11 to 1.18 Hz for DF. Subsampled electrograms deviating >10% from index values ranged from 2.5 to 56% for CFE-mean and 3.5 to 41% for DF. Intraclass correlation coefficients ranged from 0.992 to 0.788 for CFE-mean and 0.897 to 0.233 for DF. Unacceptable differences from index values were found with CFE-mean and DF from electrograms <5 seconds.
Conclusion: Electrograms of ≥5-second duration are required to accurately characterize CFAE and DF sites for ablation.     

Transmural ventricular activation during consecutive cycles of sustained ventricular tachycardia associated with coronary artery disease

Although computerized mapping has enabled the intraoperative delineation of global ventricular activation from a single complex of ventricular tachycardia (VT), beat-to-beat reproducibility of isochronic maps has not been defined. To determine the reliability of single-beat analysis, epicardial and transmural ventricular electrograms during 6 consecutive VT cycles were analyzed in 10 patients during intraoperative mapping of sustained monomorphic VT. Bipolar electrograms were recorded simultaneously using sock and needle electrodes from up to 96 epicardial and 156 transmural sites. In each patient, at each electrode site, local activation time, electrogram duration and morphology were compared over 6 consecutive beats. A total of 9,816 electrograms were analyzed. For each patient, the isochronic activation map during VT was reproducible. Mean beat-to-beat variations in local epicardial and transmural activation times were only 1.7 +/- 1.7 and 2.04 +/- 1.9 ms, respectively (difference not significant). Moreover, electrogram duration did not vary significantly. Mean variations in epicardial and transmural electrogram durations were 2.1 +/- 1.8 and 1.4 +/- 1.9 ms, respectively (difference not significant). There were only 2 instances of 2:1 conduction failure; both occurred intramurally and adjacent to a site of VT origin. Thus, transmural ventricular activation during sustained monomorphic VT is reproducible regardless of electrode site or electrogram duration. These results demonstrate that analysis of a single beat of VT is a reliable and expedient method to delineate ventricular activation during intraoperative computerized mapping for the purpose of clinical decision-making in patients with sustained monomorphic VT.     

Possible intramural site of reentrant circuit in ventricular tachycardia of nonischemic cause. Pre and intraoperative mapping studies.

A patient with a drug-refractory sustained ventricular tachycardia (VT) of nonischemic cause was mapped for the site of VT origin. The intraoperative mapping showed the earliest site of activation of VT on the epicardial surface at which the initial deflection of the local electrogram preceded the onset of the QRS complex of VT by 45 msec. The endocardial mapping could not indicate the site at which the electrogram was found prior to the onset of the QRS complex of VT. However, at the earliest site of the endocardial mapping, VT was entrained without change in the configuration of the QRS complex. After cessation of the rapid pacing, VT resumed at the intrinsic rate and the first post-paced return cycle was identical to each paced cycle length. The interval from the stimulus to the orthodromically captured local electrogram at the pacing site was identical to the cycle length of VT. Catheter ablation from the endocardial side and a cryoablative procedure from the epicardial side failed to eradicate the VT. These findings suggest an intramural site of VT origin and reentrant circuit of which the exit and the entrance face the epicardial and the endocardial surfaces, respectively.