High-Density Substrate Mapping Research Articles

Optimal cardiac rhythm during substrate mapping in scar-related ventricular tachycardia: Significance of wavefront direction on identifying critical sites

BackgroundA rotational activation pattern (RAP) around the localized line of a conduction block often correlates with sites specific to the critical zones of ventricular tachycardia (VT). The wavefront direction during substrate mapping affects manifestation of the RAP and line of block. ObjectiveThe purpose of this study was to investigate the most optimal cardiac rhythm for identifying RAP and line of block in substrate mapping. MethodsWe retrospectively evaluated 71 maps (median 3205 points/map) in 46 patients (65 ± 15 years; 33% with ischemic cardiomyopathy) who underwent high-density substrate mapping and ablation of scar-related VT. Appearance of a RAP during sinus, right ventricular (RV)-paced, left ventricular (LV)-paced, and biventricular-paced rhythms was investigated. ResultsRAP was identified in 24 of 71 maps (34%) in the region where wavefronts from a single direction reached but not in the region where wavefronts from multiple directions centripetally collided. The probability of identifying the RAP depended on scar location; that is, anteroseptal and inferoseptal, inferior and apical, and basal lateral RAPs were likely to be identified during sinus/atrial, RV-paced, and LV-paced rhythms, respectively. In 13 patients, the RAP was not evident in the baseline map but became apparent during remapping in the other rhythm, in which the wavefront reached the site earlier within the entire activation time. ConclusionThe optimal rhythm for substrate mapping depends on the spatial distribution of the area of interest. A paced rhythm with pacing sites near the scar may facilitate the identification of critical VT zones.

Long-term success of a multi-electrode substrate mapping and ablation strategy versus a classic single tip mapping and ablation strategy for ventricular tachycardia ablation in patients with ischemic cardiomyopathy.

Over the past years, mapping and ablation techniques for the treatment of ventricular tachycardia (VT) have evolved rapidly. High Density (HD) substrate mapping is now routine and pre-procedural imaging is increasingly used. The additional value of these techniques for long-term VT-free survival is not clear. We compared baseline and procedural characteristics, procedural success, safety and outcome of mapping and ablation of ventricular tachycardia in patients with ischemic heart disease between two groups. (1) Low Density (LD) group: VT mapping and ablation with a 4mm single tip catheter (2) HD group: HD substrate mapping with the Pentaray (Biosense Webster, USA) or HD Grid (Abbott, USA) catheter and ablation with a 4mm single tip catheter. VT ablation was performed in 133 patients (71 patients in LD group and 62 patients in HD group). The median follow-up was 5.0 years in LD group and 2.0 years in HD group. One-, two-, and five-year VT recurrence rates were 47%, 56%, and 65% in the LD group versus 39%, 50%, and 55% in the HD group (log-rank test for VT recurrence p=.70). One-, two-, and five-year ICD shock recurrence rates were 14%, 18%, and 24% in the LD group versus 8%, 15%, and 19% in the HD group (log-rank test for ICD-shock p=.79). All-cause mortality, cardiac (non-arrhythmic), and arrhythmic death, were similar in both groups. Severe procedural complications (tamponade, stroke, or procedural death) occurred in four patients (5%, 1 vascular, 3 tamponade) in the LD group versus two patients (3%, both tamponade) in the HD group (NS). In univariate and multivariable analysis, only a higher LVEF was significantly associated with VT-free survival. HD mapping was not significantly associated with VT-free survival. Anterior infarct location and age were significantly associated with ICD recurrent shock in both univariate and multivariable analyses. In patients with ischemic cardiomyopathy, a HD substrate mapping, and ablation strategy did not lead to higher VT-free survival and shock-free survival compared to a single tip mapping and ablation strategy. In this study, only LVF is an independent predictor for VT recurrence. Anterior infarct location and age predict recurrent ICD shocks.

PO-05-065 HIGH DENSITY PACE-MAPPING TO IDENTIFY FUNCTIONAL ARRHYTHMOGENIC SUBSTRATE IN SCAR-MEDIATED VENTRICULAR TACHYCARDIA

The location of conduction abnormality including activation slowing and wavefront discontinuity, which often corresponds to the critical zones of reentrant circuit in scar-mediated ventricular tachycardia (VT), is affected by the wavefront direction during substrate mapping. We hypothesized that an abrupt change in paced-QRS morphologies may occur at the region with conduction abnormality. This study assessed the conduction velocity in substrate mapping during at least two rhythms at the region where an abrupt change in paced-QRS morphologies was obtained. In a retrospective review of 57 patients who underwent functional substrate mapping for scar-mediated VT, 21 patients underwent it during multiple rhythms, that is intrinsic rhythm and paced rhythm with high-density pace-mapping in the area of interest. In 10 of these patients, those critical sites, as determined by direct termination during ablation (4 VTs, 33%) or pace-mapping findings (8 VTs, 67%) were identified in a total of 12 VTs. Conduction velocities during an intrinsic rhythm or paced rhythm at the isthmus area were assessed based on the difference of local activation time between two sites along the site where pace-mapping scores changed abruptly. Pace-mapping scores, which were obtained at two adjacent sites along the presumed isthmus, showed 92% [interquartile range [IQR] 89-96%] at the exit side and 48% [IQR 41-56%] at the adjacent entrance side. Ten patients (71±9 years, 9 (90%) male, 6 (60%) nonischemic) underwent high-density substrate mapping during multiple rhythms, that is intrinsic rhythm including sinus rhythm (n=7) or right ventricular pacing (n=5) and paced rhythm including right (n=5) or left ventricular pacing (n=7). Conduction velocity during intrinsic rhythm at the location of abrupt pacemap change was 0.37m/sec [IQR 0.19-0.43 m/sec], which was no slower than 0.25 m/sec, defined as activation slowing in previous studies. However, conduction velocity at abrupt pacemap change site that was faster in one of the multiple rhythms, was significantly slowed down when changing to the other rhythm (0.41 m/sec [IQR 0.25-1.05 m/sec] vs. 0.09 m/sec [IQR0.07-0.22 m/sec], P<0.01) (Fig.1). The abrupt change in paced-QRS morphology in a novel high-density pace-mapping strategy, which is shown independent of wavefront direction during substrate mapping, can identify the high-yield regions with conduction abnormality being critical for reentry.

High-density substrate mapping of the left ventricle as a guide for endomyocardial biopsy: an omnipolar, bipolar, and cardiac magnetic resonance imaging perspective

Abstract Funding Acknowledgements Type of funding sources: None. Background The recent introduction of Omnipolar Technology (OT) has the potential to improve ventricular substrate characterization. In fact, the amplitude of omnipolar electrograms is less dependent of the propagation direction of the recorded wavefront than that of bipolar electrograms, potentially increasing the sensitivity for the detection of viable myocardium by electroanatomical voltage mapping (EVM). Purpose To assess the presence and extension of dense scar regions and low-voltage areas in omnipolar voltage (OV) maps of the left ventricle (LV) as compared to standard bipolar endocardial maps and cardiac magnetic resonance (CMR)-derived pixel signal intensity (PSI) maps, among patients undergoing EVM-guided endomyocardial biopsy (EMB). Methods The study included 10 patients undergoing LV substrate mapping and EVM-guided EMB at our institution using the Advisor HD Grid mapping catheter. Before the procedure, contrast enhanced-CMR was obtained for each patient and PSI maps were derived from late gadolinium enhancement sequences with the ADAS-VT software. Scar core and border zone areas were measured in PSI endocardial (10-40% of wall thickness) maps and compared to dense scar regions (&amp;lt;0.5 mV) and low-voltage areas (0.5-1.5 mV) measured by standard bipolar endocardial mapping and OV endocardial mapping, respectively. Continuous variables were checked for normality with the Shapiro-Wilk test, and are reported as mean±standard deviation or median [1st-3rd quartile], as appropriate. Statistical comparisons among the three types of mapping (PSI mapping, standard bipolar, and OV) were performed with Friedman test with post-hoc sign test, as appropriate. P values&amp;lt;0.05 were considered statistically significant, and all analyses were performed with the software RStudio. Results The indication for EVM-guided EMB was a clinical suspicion of arrhythmogenic or inflammatory cardiomyopathy in all cases. Dense scar regions and low voltage areas detected by OV (dense scar: 2.2 [1.2-6.9] cm2; low voltage areas: 8±3.8 cm2) and standard bipolar mapping (dense scar: 3.4 [2.3-9.6] cm2; low voltage areas: 8.4±4 cm2) were similar to scar core and border zone areas shown by PSI maps (scar core: 1.6[0.6-2.9] cm2; border zone: 3.9[3.7-7.6] cm2; all p=NS). However, dense scar regions were less widespread with OV mapping that with standard bipolar mapping (Friedman test p=0.07; adjusted p=0.006, Figure). The diagnostic yield of EMB measured 80%, whereas mean procedural and fluoroscopy times were 136±30 min and 11±4 min, respectively. Conclusion OV mapping allowed a refinement of endocardial substrate maps of the LV as compared to standard bipolar mapping, by reducing the dependency of electrogram amplitude on the direction of propagation, thus allowing the detection of viable myocardium even in bipolar scar regions. Therefore, OV mapping may soon become a preferred approach for EVM-guided EMB.

Structure and function of the ventricular tachycardia isthmus.

Catheter ablation of postinfarction reentrant ventricular tachycardia (VT) has received renewed interest owing to the increased availability of high-resolution electroanatomic mapping systems that can describe the VT circuits in greater detail, and the emergence and need to target noninvasive external beam radioablation. These recent advancements provide optimism for improving the clinical outcome of VT ablation in patients with postinfarction and potentially other scar-related VTs. The combination of analyses gleaned from studies in swine and canine models of postinfarction reentrant VT, and in human studies, suggests the existence of common electroanatomic properties for reentrant VT circuits. Characterizing these properties may be useful for increasing the specificity of substrate mapping techniques and for noninvasive identification to guide ablation. Herein, we describe properties of reentrant VT circuits that may assist in elucidating the mechanisms of onset and maintenance, as well as a means to localize and delineate optimal catheter ablation targets.

Rotational Activation Pattern During Functional Substrate Mapping: Novel Target for Catheter Ablation of Scar-Related Ventricular Tachycardia.

Recent advancements in a 3-dimensional mapping system allow for the assessment of detailed conduction properties during sinus rhythm and thus the establishment of a strategy targeting functionally abnormal regions in scar-related ventricular tachycardia (VT). We hypothesized that a rotational activation pattern (RAP) observed in maps during baseline rhythm was associated with the critical location of VT. We retrospectively examined the pattern of wavefront propagation during sinus rhythm in patients with scar-related VT. The prevalence and features of the RAP on critical VT circuits were analyzed. RAP was defined as >90° of inward curvature directly above or at the edge of the slow conductive areas. Forty-five VTs in 37 patients (66±15 years old, 89% male, 27% ischemic heart disease) were evaluated. High-density substrate mapping during sinus rhythm (median, 2524 points) was performed using the CARTO3 system before VT induction. Critical sites for reentry were identified by direct termination by radiofrequency catheter ablation in 21 VTs or by pace mapping in 12 VTs. Among them, RAP was present in 70% of the 33 VTs. Four VTs had no RAP at the critical sites during sinus rhythm, but it became visible in the mappings with different wavefront directions. Six VTs, in which intramural or epicardial isthmus was suspected, were rendered noninducible by radiofrequency catheter ablation to the endocardial surface without RAP. RAP had a sensitivity and specificity of 70% and 89%, respectively, for predicting the elements in the critical zone for VT. The critical zone of VT appears to correspond to an area characterized by the RAP with slow conduction during sinus rhythm, which facilitates targeting areas specific for reentry. However, this may not be applicable to intramural VT substrates and might be affected by the direction of wavefront propagation to the scar during mapping. Graphic Abstract: A graphic abstract is available for this article.

P1037Relationship between left atrium low voltage areas and atrial fibrillation radiofrequency ablation success-rate: preliminary results of the SMOP study

Abstract Background radio frequency catheter ablation (CA) is an effective therapy for atrial fibrillation (AF). Some authors have described a potential relationship between the presence of areas of fibrosis in the left atrium (LA) and the success of CA, nevertheless there is a lack of multicenter studies in this field. Objective the aim of our study was to assess the relationship between the of presence of low voltage areas of the LA detected during subtrate mapping at the time of the procedure and recurrences of AF after CA. Methods we analyzed 214 patients of the SMOP-AF (Substrate Mapping as Outcome Predictor in Atrial Fibrillation Ablation), a prospective multi-centric study enrolling patients with both paroxysmal and persistent AF undergoing a first radio-frequency CA procedure. High-density mapping was performed in sinus rhythm using the CARTO system before performing pulmonary vein isolation. Areas with less than 0,5 mV on mapping were defined as low voltage zone (LVZ), while between 0,5 mV and 1,5 mV intermediate voltage zone (IVZ). IVZ and LVZ were expressed as a percentage of the LA surface. Comparisons were made by Pearson correlation, cross-tables and Chi-square test or Student T test. Results the mean age of the enrolled population was 59±9 years, left ventricular ejection fraction was 59±9%, 86.4% of the pts had tested at least one anti-arrhythmic drug. Persistent atrial fibrillation was present in 10.3% of patients. The rate of documented AF recurrence at 3 months was 15,3% (n=29). There was a statistical significant correlation between the presence of IVZ and the rate of recurrences at 3 months (r=0.16, p value 0.03). Patients with IVZ greater than 4% of the left atrium surface showed a higher risk of recurrences (19.5% vs. 8,7%, p value 0.04). No statistical difference was observed in other procedural variables (number of lesions, contact force, force-time integral) among patients with or without recurrences. Conclusion Our study showed a relationship between CA short-term success rate and the presence of areas of intermediate voltage zone detected with high-density substrate mapping at the time of the procedure. The presence of areas of intermediate voltage zone greater than 4% of the LA determines a 2.5 folds increased risk of short-term recurrence. Our data needs to be confirmed in a longer follow-up.

High-Density Substrate Mapping in Brugada Syndrome: Combined Role of Conduction and Repolarization Heterogeneities in Arrhythmogenesis

High-Density Substrate Mapping in Brugada Syndrome: Combined Role of Conduction and Repolarization Heterogeneities in Arrhythmogenesis

Letter by Santangeli et al Regarding Article, “High-Density Substrate Mapping in Brugada Syndrome: Combined Role of Conduction and Repolarization Heterogeneities in Arrhythmogenesis”

To the Editor: In their article on high-density substrate mapping in Brugada syndrome, Lambiase and colleagues reported striking endocardial conduction delays in such patients predominantly in the anterolateral right ventricular outflow tract.1 Complex and interesting electrophysiological data are presented, giving new insights into Brugada syndrome features. However, we feel that some methodological flaws in patient characterization, mapping procedure, and data interpretation give different perspectives to their conclusions. It is clear that concealed myocardial diseases, such as arrhythmogenic …

Response to Letter Regarding Article, “High-Density Substrate Mapping in Brugada Syndrome: Combined Role of Conduction and Repolarization Heterogeneities in Arrhythmogenesis”

We thank Dr Santangeli et al for their kind interest in our article describing the electrophysiological features of Brugada syndrome. The authors are concerned that we have not excluded structural heart disease, which they propose requires magnetic resonance imaging and cardiac biopsy. However, the early manifestations of arrhythmogenic right ventricular cardiomyopathy (ARVC) are electrocardiographic and arrhythmic, not structural, anomalies. None of these patients had electrocardiographic or arrhythmic manifestations indicative of ARVC. Moreover, there was no evidence of ARVC in first-degree relatives screened in the clinic, and a contrast echo with detailed right ventricular views was normal in all of the patients with …

High-Density Substrate Mapping in Brugada Syndrome

Two principal mechanisms are thought to be responsible for Brugada syndrome (BS): (1) right ventricular (RV) conduction delay and (2) RV subepicardial action potential shortening. This in vivo high-density mapping study evaluated the conduction and repolarization properties of the RV in BS subjects. A noncontact mapping array was positioned in the RV of 18 BS patients and 20 controls. Using a standard S(1)-S(2) protocol, restitution curves of local activation time and activation recovery interval were constructed to determine local maximal restitution slopes. Significant regional conduction delays in the anterolateral free wall of the RV outflow tract of BS patients were identified. The mean increase in delay was 3-fold greater in this region than in control (P=0<0.001). Local activation gradient was also maximally reduced in this area: 0.33+/-0.1 (mean+/-SD) mm/ms in BS patients versus 0.51+/-0.15 mm/ms in controls (P<0.0005). The uniformity of wavefront propagation as measured by the square of the correlation coefficient, r(2), was greater in BS patients versus controls (0.94+/-0.04 versus 0.89+/-0.09 [mean+/-SD]; P<0.05). The odds ratio of BS hearts having any RV segment with maximal restitution slope >1 was 3.86 versus controls. Five episodes of provoked ventricular tachycardia arose from wave breaks originating from RV outflow tract slow-conduction zones in 5 BS patients. Marked regional endocardial conduction delay and heterogeneities in repolarization exist in BS. Wave break in areas of maximal conduction delay appears to be critical in the initiation and maintenance of ventricular tachycardia. These data indicate that further studies of mapping BS to identify slow-conduction zones should be considered to determine their role in spontaneous ventricular arrhythmias.