Sinus Mapping Research Articles

Endocardial, epicardial, and right atrial approach for catheter ablation of premature ventricular contractions from the inferoseptal process of the left ventricle.

Inferoseptal process of the left ventricle (ISP-LV) might be a source of idiopathic ventricular arrhythmias. In these cases, ectopic foci are accessible from the LV endocardium, epicardially from the middle cardiac vein as well as from the right atrium (RA). This study reports a series of patients with premature ventricular contractions (PVCs) arising from the ISP-LV that were successfully ablated following access from different structures. Five patients (4 males, age 61 ± 12.8 years) with PVCs arising from the ISP-LV were successfully ablated using three different approaches for ablation-endocardial, epicardial (through coronary sinus or its branches), and RA approaches. Endocardial LV mapping, RA, and coronary sinus (CS) mapping were performed in all five cases. PVCs demonstrated RBBB or LBBB-like morphology and left superior axis. The three patients ablated endocardially had a maximum deflection index (MDI) of 0.36, 0.43, and 0.54, whereas in the remaining 2 patients, MDI was 0.57 and both demonstrated QS morphology in the inferior leads. Local activation time at the successful ablation site was 35 ± 8.9 (26-55) msec pre-QRS. Pacemapping at the successful ablation site resulted in a good (11/12) or perfect (12/12) QRS match in all cases. Three of the patients demonstrated frequent monomorphic PVCs of another morphology suggesting a remote exit site. All patients remained arrhythmia-free after a mean follow-up of 21 ± 15 (6-36) months. Successful ablation of PVCs from ISP-LV may require access from the CS or even RA apart from LV endocardial approach. Not infrequently patients demonstrate additional PVC foci.

PO-05-001 TARGETING WAVEFRONT DISCONTINUITY LINES FOR SCAR-RELATED VENTRICULAR TACHYCARDIA ABLATION

Late activation mapping can identify wavefront discontinuities during functional substrate mapping. Automated visualization of wavefront discontinuity lines (WaDLs) representing conduction block or delay may be a suitable target for a focused VT ablation. To describe WaDLs in multiple types of cardiomyopathy undergoing VT ablation, with correlation to critical VT circuit sites and bipolar low voltage scar. Patients who underwent high density substrate ablation with late activation mapping in sinus or paced wavefront were retrospectively analyzed. An automated mapping algorithm was used to visually demarcate WaDLs by identifying adjacent points where mapped activation times were greater than a certain timing threshold (CARTO®,Biosense Webster) Extended Early Meets Late module). Timing threshold was set to 25-35% of the mapped activation time. The number, total length, and distance to critical VT site of WaDLs was compared at each threshold 34 patients (20 post-infarct, 10 dilated, 1 Chagas, 1 sarcoid, 1 ARVC, 1 lamin) with 46 endocardial or epicardial surface substrate maps (10 epicardial, 36 endocardial; mean 1898 points) were included. WaDLs were present in each cardiomyopathy and surface, and represented average timing discontinuities of 50-61 ms (25%-35% WaDL threshold) with no difference in number or length of WaDLs by the mapped chamber, cardiomyopathy type, or wavefront. Parallel WaDLs forming putative channels were present in 37.2% of mapped chambers. In 15 patients with a critical VT site identified, the median distance from critical site to nearest WaDL was 7.4 mm (IQR 2.2-18.6 mm), with shorter distances on the epicardial surfaces compared to endocardial (1.4 vs 13.9 mm at 30% WaDL, P = 0.015). Functional substrate ablation in this cohort covered a mean 26% of the bipolar low voltage scar area (< 1.5 mV). Automated WaDLs represent easily visualized significant discontinuities that correlate with clinical VT circuits, are present in a wide variety of cardiomyopathy types and both epicardial and endocardial surfaces. Targeting WaDLs requires a smaller ablation area than low voltage homogenization.

PO-665-06 ROLE OF WALL THICKNESS CHANNELS IN FUNCTIONAL SUBSTRATE ABLATION OF SCAR-RELATED VENTRICULAR TACHYCARDIA

In patients with scar-related VT from ischemic cardiomyopathy (ICM) undergoing VT ablation, CT-derived wall thickness channels (WTCs) may coincide with VT isthmuses. It is unknown if WTCs coincide with lines of block during mapping in sinus or paced rhythm. Furthermore, WTCs have yet to be characterized in patients with VT from non-ischemic cardiomyopathy (NICM).

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.

Systematic Evaluation of High-Resolution Activation Mapping to Identify Residual Endocardial and Epicardial Conduction Across the Mitral Isthmus.

This study sought to systematically evaluate the ability of a high-resolution mapping system (Rhythmia, Boston Scientific, Marlborough, Massachusetts) to rapidly and accurately localize residual endocardial and epicardial conduction after mitral isthmus (MI) ablation, facilitating MI block. Achieving conduction block across the mitral isthmus (MI) is challenging. Fifty consecutive patients undergoing MI ablation after pulmonary vein isolation were enrolled. After initial endocardial radiofrequency (RF) ablation across the lateral MI, high-resolution activation mapping of the MI with simultaneous coronary sinus (CS) mapping was performed to verify block or localize residual conduction across the MI during left atrial (LA) appendage and CS pacing. Propagation maps were used to identify residual conduction across the MI as endocardial, via the CS or Marshall tract. In all 50 patients, after the initial endocardial ablation across the MI, repeat high-resolution mapping of the LA and CS was obtained (median: 3,329 mapped points; 4.0min of mapping time). The initial endocardial MI ablation resulted in block in 9 of 50 patients (18%). In the remaining 41 patients, the propagation map identified residual conduction in 4 patterns: 1) only endocardial gap in 12 patients (29%); 2) only CS connection in 10 patients (24%); 3) both endocardial and CS connections in 14 patients (34%); and 4) Marshall tract connection in 5 patients (12%). In 8 patients, the propagation map revealed residual conduction, despite differential atrial pacing suggesting bidirectional block. Focal ablation at the identified residual conduction site (median: 0.7min of RF) resulted in block in 49 of 50 (98%) patients. High-resolution propagation maps of the LA/CS rapidly and accurately localize residual endocardial and epicardial conduction across the MI. Focal ablation with short RF time at the identified gap(s) achieved complete block across MI in 98% of cases.

Substrate mapping for unstable ventricular tachycardia

The primary goal of catheter ablation of scar-related ventricular tachycardia (VT) is the interruption of critical areas of slow conduction responsible for the development and maintenance of the reentrant VT circuit. Most patients with scar-related VT present with unstable arrhythmias that are not amenable to interrogation from multiple sites to define the VT circuit based on the intracardiac activation sequence and the response to entrainment mapping. In order to effectively target unstable VTs, a number of ablation approaches have been described with the aim of targeting the abnormal substrate defined with mapping in sinus or paced rhythm. Some of these strategies (eg, late potential and local abnormal ventricular activity ablation or scar homogenization) target the entire abnormal substrate harboring abnormal electrograms, defined with a variety of different criteria. Scar dechanneling, linear ablation through sites matching VT with pacing, and the core isolation approach focus on more discrete regions within the abnormal substrate that have been proven relevant to the clinical and/or inducible arrhythmias by means of physiologic maneuvers, although this does not necessarily translate to fewer radiofrequency lesions to achieve the procedural end-point. Observational studies evaluating different substrate-based ablation techniques have reported fairly uniform arrhythmia-free survivals at short- and mid-term follow-up, although direct comparisons between different techniques are lacking. In this article, we summarize the different state-of-the-art substrate mapping and ablation approaches for targeting unstable VT, with a particular focus on the relative merits and limitations of the described techniques.

Left Ventricular Lead Placement Targeted at the Latest Activated Site Guided by Electrophysiological Mapping in Coronary Sinus Branches Improves Response to Cardiac Resynchronization Therapy.

Electrophysiological mapping (EPM) in coronary sinus (CS) branches is feasible for guiding LV lead placement to the optimal, latest activated site at cardiac resynchronization therapy (CRT) procedures. However, whether this procedure optimizes the response to CRT has not been demonstrated. This study was to evaluate effects of targeting LV lead at the latest activated site guided by EPM during CRT. Seventy-six consecutive patients with advanced heart failure who were referred for CRT were divided into mapping (MG) and control groups (CG). In MG, the LV lead, also used as a mapping bipolar electrode, was placed at the latest activated site determined by EPM in CS branches. In CG, conventional CRT procedure was performed. Patients were followed for 6 months after CRT. Baseline characteristics were comparable between the 2 groups. In MG (n = 29), EPM was successfully performed in 85 of 91 CS branches during CRT. A LV lead was successfully placed at the latest activated site guided by EPM in 27 (93.1%) patients. Compared with CG (n = 47), MG had a significantly higher rate (86.2% vs. 63.8%, P = 0.039) of response (>15% reduction in LV end-systolic volume) to CRT, a higher percentage of patients with clinical improvement of ≥2 NYHA functional classes (72.4% vs. 44.7%, P = 0.032), and a shorter QRS duration (P = 0.004). LV lead placed at the latest activated site guided by EPM resulted in a significantly greater CRT response, and a shorter QRS duration.

Image Guided Frontal Sinus Mapping: Our Technique

Access to the frontal sinus is challenging and both external and endoscopic approaches are described in the literature. Where an external approach is indicated, a bicoronal osteoplastic flap procedure is generally preferred as this reduces fronto-ethmoidal recess stenosis and allows obliteration if required [11. Metson R, Ung F, Kountakis S (2005) Image-Guidance in Frontal Sinus Surgery. The Frontal Sinus Springer 22: 201-209. ]

Relation between projection positions and X-ray radiation doses during placement of the coronary sinus mapping electrode

To reduce X-ray radiation injury, we investigated the relation between projection positions and X-ray radiation doses when a coronary sinus mapping electrode was placed. There were 400 patients in whom a coronary sinus mapping electrode was placed for intracardiac electrophysiologic examination or radio-frequency catheter ablation in our hospital between 1 June 2008 and 31 May 2011. The doctors who placed the coronary sinus mapping electrode and the projection positions including posteroanterior, left anterior oblique 45°, and right anterior oblique 30° projection positions were randomly selected. X-ray doses were recorded when the coronary sinus mapping electrode was placed, and then, these were compared between the three projection positions. The X-ray dose was significantly lower in the right anterior oblique 30° projection position (50.01 ± 11.38 mGy) than in the posteroanterior projection position (68.05 ± 18.85 mGy, q = 12.924, p = 0.000) and the left anterior oblique 45° projection position (71.66 ± 16.95 mGy, q = 15.214, p = 0.000). There were no statistical significances in X-ray doses between the posteroanterior and the left anterior oblique 45° projection positions (p = 0.066) and different operators (p = 0.985). Based on the results of this study, we suggest that in placing the coronary sinus mapping electrode, the right anterior oblique 30° projection position should be first adopted because it can allow the electrode to be easily placed and reduce the X-ray radiation dose as much as possible.

Ablation of atrial tachycardia originating from the noncoronary sinus: case report and literature review

This report describes a patient with atrial tachycardia who underwent radiofrequency catheter ablation. Two applications of radiofrequency energy were received at different sites within 1 week. Initially, right atrium mapping indicated that the earliest activation site was located at the His-bundle region (HBR). However, the first application of radiofrequency near HBR appeared to be ineffective. Moreover, a degree III atrioventricular block and inferior ST-segment elevation was temporally observed during the therapy, which recovered after drug treatment. As later aortic sinus mapping showed that the activation site located at the noncoronary sinus (NCS) preceded the one at HBR, and this activation terminated at atrial tachycardia, a second application of radiofrequency was performed at NCS without any complications. In addition, a literature review of the clinical features of atrial tachycardia at the NCS is also summarized in the present report.

Successful Transseptal Catheter Ablation of Premature Ventricular Contractions Arising from the Mitral Annulus: A Case with a Pure Annular Origin

A 74-year-old man with symptomatic premature ventricular contractions (PVCs) with a right bundle branch block and right inferior axis QRS morphology underwent electrophysiologic testing. During the PVCs, coronary sinus mapping revealed ventricular prepotentials with the earliest activation in the distal great cardiac vein (GCV) where the local ventricular electrograms were smaller in amplitude than the atrial electrograms. The transaortic approach could not reach the earliest activation site within the GCV, but the transseptal catheter ablation successfully eliminated the PVCs on the mitral valve. With catheter ablation of ventricular arrhythmias with pure mitral annular origins, a transseptal approach may be necessary.

Identifying the Origin of Right and Left Ectopic Atrial Beats Triggering Atrial Fibrillation before Atrial Transseptal Procedure

Atrial premature depolarizations (APDs) triggering atrial fibrillation (AF) originate from mainly the pulmonary veins (PVs), but, in some cases, atrial ectopic beats (AEBs) triggering AF originate from the right atrium (RA) or the superior vena cava. Accurate identification of the origin of APDs in the PVs by means of RA and coronary sinus mapping is difficult. Purpose: The aim of this study was to identify the origin of AEBs triggering AF before transseptal catheterization. Electrode catheters were placed in the posteroseptal RA (PSRA), right pulmonary artery (RPA), left pulmonary artery (LPA), and esophagus in 10 patients with paroxysmal AF. We analyzed endocardial electrograms from the PSRA, RPA and LPA, and epicardial electrograms from the esophagus. The origin of the AEBs in the PVs was determined before PV ablation by mapping 4 PVs simultaneously. Four AEBs originated from the left superior PV (LSPV), 2 from the left inferior PV (LIPV), 4 from the right superior PV (RSPV), 2 from the RA or superior vena cava. In AEBs originating from the RA, the PSRA activation was the earliest and it proceeded in a cranial to caudal direction. In AEBs originating from the RUPV, RPA was the earliest. The esophageal activation sequence was in a cranial to caudal direction. In AEBs from the LSPV, LPA was the earliest and the esophageal activation sequence proceeded in a cranial to caudal direction. In AEDs from LIPV, LPA was the earliest, and the esophageal activation sequence was nearly simultaneous. Atrial activation sequences from the PSRA, RPA, LPA, and esophageal catheters can accurately identify the location of the initiating foci of AF before a transseptal procedure.

AB36-3: Iso-duration mapping during ventricular pacing as a tool to ablate unmappable ventricular tachycardia after remote myocardial infarction

VT after MI is usually due to reentry through a protected isthmus bounded by functional lines of block (LoB). When VT is not inducible or not tolerated (unmappable VT) there is a need to unmask the isthmus by sinus mapping or pacing maneuvers. Experimental data suggest that sinus rhythm electrograms (EGM) along the central common pathway have a short duration compared to longer EGMs along LoBs. Using Carto® we aimed at identifying these isthmus-related LoBs by mapping the EGM duration during RV pacing.

Entrainment mapping for rapid distinction of left and right atrial tachycardias

Distinguishing left from right atrial tachycardia is a critical step for guiding ablation. The purpose of this study was to develop and validate a simple algorithm predicting the location of macroreentrant atrial tachycardia (AT) circuits from limited entrainment mapping in right atrium (RA) and coronary sinus (CS). In 180 patients with organized reentrant AT, entrainment was performed at the high RA, proximal CS, and distal CS. The difference between the postpacing interval (PPI) and tachycardia cycle length (TCL) was calculated at each site. The location of the AT reentrant circuit was determined by mapping and ablation. An algorithm predicting AT regions was developed from 104 ATs in the first 90 patients (group I) and prospectively evaluated in a validation cohort of 106 ATs in the second 90 patients (group II). In group I, PPI-TCL difference <50 or >50 ms at the high RA distinguished RA from LA reentrant circuits. For RA tachycardias, PPI-TCL difference at the proximal CS distinguished common flutter from lateral RA circuits. For LA circuits, PPI-TCL difference at the proximal and distal CS distinguished perimitral reentry from reentry involving the right pulmonary veins and septum. In group II, an algorithm based on PPI-TCL difference >50 or <50 ms at the high RA, proximal CS, or distal CS had sensitivity of 94%, specificity of 88%, and predictive accuracy of 93% for predicting the successful ablation region. Limited entrainment from sites accessible from the RA can expeditiously suggest the AT location to guide more detailed mapping and potentially avoid unnecessary transseptal punctures in some patients.

Coronary sinus mapping to differentiate left versus right ventricular outflow tract tachycardias

Outflow tract ventricular tachycardia (OT-VT) can originate from several different segments of the outflow tract. Various ECG criteria have been proposed for localization of OT-VTs. We present two patients, one with left and one with right OT-VT. We used local ventricular electrograms in the coronary sinus to localize the focus of the OT-VT. Mapping of local ventricular electrograms in the coronary sinus may be a simple and effective method for differentiating right versus left ventricular outflow tract tachycardias. However, the diagnostic value and precision of this method should be evaluated in a series of patients before its implementation in the OT-VT ablation decision algorithm.

Why do patients with right bundle branch block benefit from cardiac resynchronization therapy?

Patients with right bundle branch block (RBBB) and heart failure (HF; LVEF <40%) benefit from cardiac resynchronization therapy (CRT), but mechanism is unclear. We postulated that RBBB+HF was accompanied by significant LV conduction delays (because HF affects cell-to-cell conduction). This was tested by measuring QRS duration (QRSd) and LV activation, during intrinsic conduction and right ventricular apical pacing (RVP), in RBBB+HF compared to pts with left bundle branch block (LBBB) +HF, and normals. Since terminal LV depolarization occurs in the posterolateral basal LV, we estimated LV activation time by interval from QRS onset to the end of the latest LV bipolar electrogram inscribed during coronary sinus mapping.

A Unipolar Coronary Sinus Mapping Study of Patients with Left-Sided Atrioventricular Accessory Pathways

So-called unipolar 'PQS pattern' is widely accepted as a hallmark of successful catheter ablation of the left-sided atrioventricular accessory pathway. However, the unipolar nature of the electrogram and the site-dependent appearance of this characteristic pattern are poorly understood. Therefore, unipolar coronary sinus (CS) mapping was performed using a multipolar fine electrode in patients with Wolff-Parkinson-White (WPW) syndrome associated with an antegrade left-sided accessory pathway (case group) and those with a concealed left-sided accessory pathway or atrioventricular nodal reentrant tachycardia (control group) under sinus rhythm and fixed high right atrial, CS ostial, and distal pacing. In both groups, the unipolar CS atrial electrogram showed intrinsic negative deflection (initial positive followed by negative parts) with considerable variation depending on the recording site. This unipolar configuration of the atrial electrogram was not influenced by different activation sequences during pacing at various sites. The case group exhibited a unipolar 'PQS pattern' at successful ablation sites for the left lateral to anterolateral accessory pathway. However, this was not true for the left posteroseptal accessory pathway, possibly because the negative part of the atrial electrogram distorted the 'PQS pattern' as an intervening dip. In conclusion, the site-dependent variations of the unipolar CS atrial electrogram underlie the limited usefulness of the 'PQS pattern' in left posteroseptal accessory pathway localization.

Purkinje and ventricular contributions to endocardial activation sequence in perfused rabbit right ventricle

Interactions between peripheral conduction system and myocardial wave fronts control the ventricular endocardial activation sequence. To assess those interactions during sinus and paced ventricular beats, we recorded unipolar electrograms from 528 electrodes spaced 0.5 mm apart and placed over most of the perfused rabbit right ventricular free wall endocardium. Left ventricular contributions to electrograms were eliminated by cryoablating that tissue. Electrograms were systematically processed to identify fast (P) deflections separated by >2 ms from slow (V) deflections to measure P-V latencies. By using this criterion during sinus mapping (n = 5), we found P deflections in 22% of electrograms. They preceded V deflections at 91% of sites. Peripheral conduction system wave fronts preceded myocardial wave fronts by an overall P-V latency magnitude that measured 6.7 +/- 3.9 ms. During endocardial pacing (n = 8) at 500 ms cycle length, P deflections were identified on 15% of electrodes and preceded V deflections at only 38% of sites, and wave fronts were separated by a P-V latency magnitude of 5.6 +/- 2.3 ms. The findings were independent of apical, basal, or septal drive site. Modest changes in P-V latency accompanied cycle length accommodation to 125-ms pacing (6.8 +/- 2.6 ms), although more pronounced separation between wave fronts followed premature stimulation (11.7 +/- 10.4 ms). These results suggested peripheral conduction system and myocardial wave fronts became functionally more dissociated after premature stimulation. Furthermore, our analysis of the first ectopic beats that followed 12 of 24 premature stimuli revealed comparable separation between wave fronts (10.7 +/- 5.5 ms), suggesting the dissociation observed during the premature cycles persisted during the initiating cycles of the resulting arrhythmias.

Electroanatomic characterization of conduction barriers in sinus/atrially paced rhythm and association with intra-atrial reentrant tachycardia circuits following congenital heart disease surgery.

The electrophysiologic mechanism of intra-atrial reentrant tachycardia (IART) is generally thought to be a macroreentrant circuit revolving around a nonconductive or highly anisotropic barrier. However, the electrical and anatomic substrate that supports these circuits has been incompletely defined. Our objectives were to characterize the atria of patients with IART using electroanatomic mapping in sinus or atrially paced rhythm and to determine whether electrical barriers identified in sinus/atrially paced rhythm are associated with IART circuits. Eighteen patients with IART and a remote history of repaired or palliated congenital heart disease were studied [8 biventricular repair, 8 single ventricle palliation (7 Fontan), and 2 Mustard repair]. Thirteen patients had a right AV valve. In sinus/atrially paced rhythm, electrical evidence of a crista terminalis was identified in 11 patients, an atriotomy in 12, and > or = 1 right atrial free-wall scar in 11. In 26 IART circuits characterized, 12 used the right AV valve as a central obstacle, 6 used a right atrial free-wall scar, 3 used an atriotomy, 3 used the crista terminalis, and 2 circuits used an atrial septal scar. All central obstacles used by IART circuits were identified in sinus/atrially paced rhythm. The crista terminalis, atriotomy, and right atrial scars can be identified in patients with repaired congenital heart disease by electroanatomic mapping in sinus/atrially paced rhythm. These conduction barriers frequently function as the central obstacle for IART. Demonstration of such features may help focus investigational mapping without reliance on spontaneous initiation of the tachycardia.

Role of Epicardial Mapping in Catheter Ablation of Postmyocardial Infarction Ventricular Tachycardia

The role of epicardial mapping for radiofrequency (RF) catheter ablation of postmyocardial infarction monomorphic ventricular tachycardia (VT) is still under investigation. We present two septuagenarian patients with a history of myocardial infarction, poor left ventricular function, and drug-refractory monomorphic VT who were treated with RF catheter ablation. The first patient had a history of myocardial infarction, left ventricular aneurysm, and mitral valve replacement complicated by recurrent drug refractory VT and congestive heart failure. The second patient had ischemic cardiomyopathy and VT and was implanted with a cardioverter defibrillator and subsequently suffered repeated episodes of VT refractory to multiple antiarrhythmic drugs. In both patients, coronary sinus mapping was performed with a multipolar catheter as endocardial mapping did not reveal satisfactory sites for ablation. Epicardial catheter mapping provided stable electrograms and identification of areas of slow conduction during VT. RF lesions guided by epicardial mapping resulted in successful ablation of VT and no recurrence at long-term follow-up. This report emphasizes the potential usefulness of coronary sinus mapping as an adjuvant to endocardial mapping to guide VT ablation.