Magnetic Electroanatomic Mapping Research Articles

Abstract 13934: Ventricular Pulsed Field Ablation Using a Focal Lattice-Tip Catheter: The Impact of Repetitive Applications

Introduction: Pulsed field ablation (PFA) is being increasingly studied for catheter ablation of atrial arrhythmias. However, there is little published on the efficacy of ventricular PFA. Recently, a 7.5-Fr ablation catheter with a 9mm compressible lattice-tip linked to a magnetic electroanatomical mapping system has been introduced (Sphere-9 and HexaMap, Prism-1, respectively; Affera, Inc). In contrast to radiofrequency ablation, there is little understating how to create an adequate lesion depth on the myocardial using PFA. Accordingly, we assessed the feasibility and effectiveness of repetitive PFA pulses in creating ventricular lesions using the lattice-tip catheter in porcine preclinical studies. Methods: Under general anesthesia, low dose 1-sec PFA pulses were delivered in 4 healthy swine ventricles using lattice-tip catheter and its compatible PF generators (HexaPulse, Affera, Inc). Three strategies were assessed: 2, 3 or 4 applications at each location. Pulses were repeated at 10-15 sec intervals. After survival for ~ 24 hrs, swine were sacrificed humanely, and TTC staining was performed to ascertain lesion dimensions on gross pathology. Results: Discrete PFA lesions (n=51) were successfully delivered: 24 in the RV and 27 in the LV. Dimensions were obtained for 49 of 51 discrete lesions. Transmurality was observed in 9 of 23 (39%) RV and 1 of 26 (4%) LV lesions. Significantly larger ventricular lesions were noted with the 4-application strategy: length 17.6±3.9 mm, width 13.4±1.8 mm and depth 6.1±2.1 mm (see Figure ). The myocardium was trabeculated at 40 of 49 lesion locations: all lesions projected uniformly into the tissue without surface gaps. No sustained ventricular arrhythmias were observed during PFA. Conclusion: Focal PFA using a lattice-tip ablation catheter revealed clinically-relevant ventricular lesions without complications; repetitive applications significantly increase lesion dimensions.

P1010Association between left atrial fibrosis detected by cardiac magnetic resonance and endocardial electroanatomic mapping in the evaluation of the electrophysiological substrate in atrial fibrillation

Abstract Background Atrial fibrillation (AF) is related to left atrial fibrosis, but its identification by late magnetic resonance imaging (LGE) with gadolinium (LGE) persists in controversy due to heterogeneous results in its correlation with the electroatomic map (EAM) and the difficulty of perform histological studies in humans. Purpose We try to examine the point-by-point association between high density EAM and LGE-MRI using an automatic and reproducible method. Methods A LGE-MRI was performed in 16 patients prior to ablation. Three different areas were established depending on the intensity of normalized enhancement for each patient according to their blood group with the image intensity ratio (IIR) (healthy <1.20, border area (BZ) ≥1.20 <1.32 and scar ≥1.32). The high density electroanatomic maps of the left atrium (LA) were projected onto the MRI, obtaining an automatic correlation point by point. Results The study obtained significant differences (p < 0.001) between voltage (mV) and CV (mm/ms) among healthy, BZ and scar areas, as well a significant inverse correlation (p < 0.001) between voltage and IIR (R=-0.39). It obtained too a significant correlation between CV and IIR (R=-0.24), but this showed a greater correlation in those patients who have the least dilated LA (p = 0.02). Conclusions LGE-MRI and EAM showed good correlation in delineating potential pathologic substrate in AF, but left atrium dilation could reduce the performance of the CMR in this task. Conduction velocity could be more sensitive than voltage and LGE-MRI to detect incipient substrate in AF. Voltage and conduction velocity values Area /IIR Velocity (mm/ms) Voltage (mV) I / <.20 1.036(0.913-1.158) 1.593(1.489-1.696) 2 / ≥1.20 and <1.32 0.722(0.590-0.850) 0.792 (0.649-0,935) 3 / ≥1.32 0.623(0.473-0,733) 0.444(0.245-0.642) Voltage and conduction velocity values in the three areas of the LGE-RMN. Abstract Figure. Correlation among voltage, VC and LA

Three dimensional ultra-high-density electro-anatomical cardiac mapping in horses: methodology.

Ultra-high-density cardiac mapping allows very accurate characterisation of atrial and ventricular electrophysiology and activation timing. To describe the technique and evaluate the feasibility of magnetic electro-anatomical mapping of the equine heart. In vivo experimental method development. A mapping system using an 8.5F bidirectional deflectable catheter with a deployable mini-basket (3-22mm) containing 64 electrodes divided over eight splines was evaluated. Based upon predefined beat acceptance criteria, the system automatically acquires endocardial electrograms and catheter location information. Electro-anatomical maps were acquired from four horses in sinus rhythm under general anaesthesia. All endocardial areas within each chamber could be reached. Access to the left atrium required the use of a deflectable sheath. With the exception of the left atrial map of horse 1, all four chambers in all four horses could be mapped. Optimisation of the beat acceptance criteria led to a reduction in manual correction of the automatically accepted beats from 13.1% in the first horse to 0.4% of the beats in the last horse. Only a limited number of horses were included in the study. Ultra-high-density 3D electro-anatomical mapping is feasible in adult horses and is a promising tool for electrophysiological research and characterisation of complex arrhythmias.

P4652Magnetic resonance and electroanatomical guided endomyocardial biopsy as a diagnostic tool in the clinician's box: a 5 year experience

Abstract Background Percutaneous endo-myocardial biopsy (EMB) is an invasive diagnostic test used to reach or confirm a diagnosis when structural or substrate anomalies are suspected, such as in cardiomyopathies or myocarditis evaluation. In recent years, cardiac magnetic resonance imaging (MRI) and endo-cavitary electro-anatomical mapping (EAM) have been used to localize the most significant myocardial area to sample, therefore increasing EMB overall effectiveness and reliability. Purpose To describe and characterize safety, feasibility and anatomical findings of a large cohort of patients (pts) undergoing diagnostic EMB and to assess its impact on the treatment decision making algorithm. Methods A cohort of all pts undergoing a percutaneous EMB at our Institution from January 2014 to January 2019 was analyzed. All EMB procedures were guided by a pre-procedural cardiac MRI radiological alteration analysis and an endo-cavitary EAM. Intra-cardiac echography (ICE) was used in all procedures, to directly visualize the sample area and to evaluate in real time post-EBM complications. Demographics, clinical data, MRI data, pathological EMB features, and peri-procedural data were systematically retrieved. Results One-hundred and eleven pts were enrolled (78% male, 47±4 y.o., 33% athletes). EMB indication was abnormal MRI findings in 94 (85%), pathological EMB voltages in 10 (9%) and clinical suspect and patient history in 7 (6%) pts. EMB sample area was determined by both MRI and EAM pathological area analysis in 92 (83%) pts, while by EAM alone in 19 (17%) pts (n=6 pathological unipolar EAM; n=13 bipolar and unipolar pathological EAM). The sample site was the right ventricle in 89 (80%), the left ventricle in 20 (18%), and both in 3 (2%) pts. In 103 (93%) pts a concomitant electrophysiological induction study was performed (40% positive for sustained ventricular arrhythmias) and 35 (32%) pts underwent a trans-catheter ablation (TCA) (n=8 epicardial TCA; n=2 endo-epicardial TCA; n=25 endocardial ATC). Only 2 (2%) peri-procedural adverse events were witnessed, specifically femoral pseudo-aneurysms, requiring surgical repair. EMB analysis allowed to confirm 58 (52%) pre-procedural diagnosis and to reach 32 (29%) new diagnosis, while resulting inconclusive or non-specific in the diagnostic process only in 21 (19%) cases [Figure1]. A total of 33 (30%) intra-cardiac devices (ICDs) were implanted contextually in the cohort, of which 9 (8%) solely upon EMB indication; in 4 (4%) other patients, biopsy represented a strong decisional factor in the multi-modality decision process for abstaining from ICD implant. Dashed lines: diagnosis changed upon EMB Conclusion MRI and EAM guided EMBs allowed to finely define a large cohort of patients by representing a disease defining parameter in over 80% of the enrolled pts while and a decision shifting parameter in ICD implant algorithm in a high % of pts.

Correlation of scar localization between cardiac magnetic resonance imaging and electro-anatomic mapping at electrophysiology study in patients with cardiac rhythm management devices

Background Cardiac magnetic resonance imaging (CMR) can accurately delineate myocardial scar for substrate guided ventricular tachycardia (VT) ablation. Susceptibility artifact from cardiac rhythm management device (CRMD) generator and leads can significantly affect image quality limiting the evaluation of myocardial scar and foci of VT. We conducted a retrospective study to correlate scars from CMR to the voltage mapping obtained at electrophysiology study (EPS).

Initial Experience With a Multielectrode Catheter Equipped With the Single‐Axis Sensor Technology for High‐Density Electroanatomical Mapping in a Swine Model

magnetic-based electroanatomical mapping systems are widely used during catheter ablation. Currently, the size of the sensor incorporated in the catheter to allow its localization is large, prohibiting the placement of more than one sensor on any single catheter. As a result, multielectrode catheters cannot be tracked by the magnetic-based mapping systems. Single-axis sensors (SAS) are new generation sensors that are significantly smaller in size. The small size of these new sensors allows the placement of more than one sensor on each catheter, allowing the tracking of multielectrode catheters. The objective of this study is to test the feasibility of creating high-density magnetic electroanatomical maps using a new generation multielectrode catheter equipped with the SAS technology. anatomical reconstruction of cardiac chambers and the aorta, together with activation mapping of the right atrium during both sinus rhythm and pacing-induced premature atrial contractions (PACs), were performed in 5 swine using both a conventional mapping catheter and the novel multielectrode catheter equipped with SAS. The multielectrode mapping provided a detailed definition of cardiac anatomy while requiring shorter acquisition times. In addition, mapping of PACs origin was significantly faster using the multielectrode catheter. the novel multielectrode catheter equipped with the SAS technology can be used in combination with magnetic electroanatomical mapping systems to generate high-density anatomical reconstructions and activation maps.

Combined Ventricular Endocardial and Epicardial Substrate Mapping Using a Sonomicrometry‐Based Electroanatomical Mapping System

Substrate mapping using a magnetic electroanatomical mapping system (MEAM) has been shown to accurately delineate the location/extent of scarred myocardium. This study examined the ability of a sonomicrometry-based electroanatomic mapping system (SEAM) to render endocardial and epicardial substrate maps of infarcted ventricular myocardium. In 7 swine with healed myocardial infarctions, combined epicardial and endocardial left ventricular (LV) substrate maps were created with both SEAM and MEAM mapping systems using 246+/-68 and 244+/-44 points respectively. Scarred myocardium was identified based upon bipolar electrogram amplitude < 1.5 mV, and radiofrequency ablation lesions were delivered to the scar border as defined by the sonomicrometry mapping system. The LV endocardial chamber volume as defined by SEAM (125+/-46 ml) correlated well with that defined by the MEAM (137+/-45 ml, r=0.77, p < 0.05). The area of infarcted tissue as determined by SEAM was highly correlated with that determined by gross pathology (r=0.96 for endocardial scar and r=0.92 for epicardial scar p < 0.05). The scar area calculated by the SEAM system also correlated well with the scar area determined by the MEAM system (0.91 for endocardial scar and 0.90 for epicardial scar p < 0.05). Finally, the sonomicrometry-based system was able to guide the placement of radiofrequency ablation lesions to the borders of the scar. This study demonstrates that the sonomicrometry-based mapping can accurately reconstruct three-dimensional voltage maps of the endocardial and epicardial ventricular surfaces and guide the placement of ablation lesions along the scar border zone.

A Case Study on Cardiac Imaging in Patients with Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy-A Comparison between 64-Slice Computed Tomography, Magnetic Resonance Imaging and Electroanatomical Mapping-

A Case Study on Cardiac Imaging in Patients with Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy-A Comparison between 64-Slice Computed Tomography, Magnetic Resonance Imaging and Electroanatomical Mapping-

Identification of distinct electrocardiographic patterns from the basal left ventricle: Distinguishing medial and lateral sites of origin in patients with idiopathic ventricular tachycardia

Idiopathic ventricular tachycardias (IVTs) can originate from the basal left ventricle (LV). To determine if using magnetic electroanatomic mapping (MEAM) for accurate localization (1) unique ECG morphologies on pace maps from medial and lateral sites in basal LV could be identified and (2) this ECG information would facilitate VT localization. In 12 patients with structurally normal hearts undergoing ablation for IVT, detailed MEAM of LV was constructed in sinus rhythm and pace-mapping was done from the septal-parahisian (S-P) region, aortomitral continuity (AMC), and superior, superolateral, and lateral mitral annular (MA) locations. Pace maps were analyzed for ECG morphologies in limb leads and transition patterns in precordial leads. Medial pacing sites (S-P and AMC) compared with lateral sites (superolateral and lateral MA) demonstrated narrower QRS complexes (134 +/- 24 msec vs. 182 +/- 18 msec; P < .05) with initial negative forces in lead V1 and predominantly positive forces in lead I (amplitude 0.59 +/- 0.27 mV vs. 0.16 +/- 0.34 mV; P < .05). The ratio of QRS complexes in leads II and III was >1 for all (12 of 12) S-P pace maps and 11 of 12 lateral MA pace maps but remained < or =1 for pace maps from 10 of 12 AMC locations, 11 of 12 superior MA locations, and 10 of 11 superolateral MA locations. Using these ECG criteria, a blinded reviewer was able to accurately localize the site of origin (SOO) of clinical arrhythmia (successful ablation site on MEAM) in 10 of 12 cases (83%) of IVT originating from basal LV. Pace maps from basal LV endocardium manifest site-dependent ECG morphologies that can help differentiate medial from lateral locations and can predict the SOO of clinical arrhythmias from this region.

Favorable effect of pulmonic vein isolation by partial circumferential ablation on ostial flow velocity

Objectives The aim of this study was to determine the effect of electrical isolation of pulmonic vein (PV) on flow velocity. Background We report our experience with electrical isolation of PV by partial circumferential ablation and its effect on ostial peak flow velocity as assessed by phased-array ultrasound catheter imaging. Methods Sixty-two patients participated in the study. Magnetic electroanatomic mapping, ultrasound catheter imaging, and Lasso mapping catheter were used. Electrical isolation was achieved by delivering radiofrequency ablation (RFA) lesions proximal to Lasso mapping catheter bipoles showing PV entry. Following this, the number of RFA lesions/PV and their segment-wise distribution (maximum 4/PV) were assessed. Results Fifty right superior, 51 left superior, 32 left inferior, and 17 right inferior PVs were isolated. RFA involved 4 segments in 42 PVs, 3 segments in 61 PVs, and ≤2 segments in 47 PVs. Electrical isolation augmented ostial peak flow velocity (55 ± 15 cm/s to 96 ± 26 cm/s). This net increase was higher for superior versus inferior PVs (43 ± 23 cm/s and 34 ± 18 cm/s; P = .02). For ≤2, 3, and 4 segments ablated per vein, the net increase in peak flow velocity was 33 ± 22 cm/s, 42 ± 23 cm/s, and 46 ± 23 cm/s, respectively ( P = .02). Over a mean follow-up of 16 ± 7 months, freedom from atrial fibrillation (AF) or >90% reduction in AF burden, either with or without previously ineffective antiarrhythmic agents, was achieved in 54 patients (87%). Conclusions In the majority of PVs (72%), electrical isolation can be achieved by partial circumferential ablation (targeting ≤3 segments/PV) with lower acute increase in ostial peak flow velocity and good AF control.

Rapid magnetic electroanatomic mapping of typical atrial flutter using a novel multielectrode catheter.

Rapid magnetic electroanatomic mapping of typical atrial flutter using a novel multielectrode catheter.

Unusual Intraatrial Reentry Following the Mustard Procedure Defined by Multisite Magnetic Electroanatomic Mapping

This report describes a patient with d-TGA post Mustard repair who presents with atrial arrhythmias. Two distinct intraatrial reentrant tachycardias were discovered and successful catheter ablation was performed in a unique atrial location not previously described. This case also explores the use of magnetic electroanatomic mapping in guiding catheter ablation.

Characterization of the electroanatomic substrate for monomorphic ventricular tachycardia in patients with nonischemic cardiomyopathy.

Ventricular arrhythmias are common in the setting of nonischemic cardiomyopathy. The etiology for the cardiomyopathy is frequently not identified and the label of "idiopathic" is applied. Interstitial fibrosis with conduction system involvement and associated left bundle branch block characterizes the disease process in some patients and the mechanism for monomorphic ventricular tachycardia is commonly bundle branch reentry. However, most patients with nonischemic cardiomyopathy have VT due to myocardial reentry and demonstrate marked myocardial fibrosis and electrogram abnormalities. Although patient specific, the overall distribution of electroanatomic abnormalities appears to be equal on the endocardium and epicardium. The extent of electrogram abnormalities appears to parallel arrhythmia presentation and/or inducibility. Patients with sustained uniform morphology VT have the most extensive endocardial and epicardial electrogram abnormalities. Magnetic electroanatomic voltage mapping provides a powerful tool to characterize the location and extent of the arrhythmia substrate. Basal left ventricular myocardial involvement, as indexed by the location of contiguous electrogram abnormalities, is common in patients with sustained VT and left ventricular cardiomyopathy. The relatively equal distribution of electrogram abnormalities on the endocardium and epicardium, and the results of mapping and ablation attempts, suggest that critical parts of the reentrant circuit may be epicardial. Unique features of the electroanatomic substrate associated with cardiomyopathy due to Chagas' disease, sarcoidosis, and arrhythmogenic right ventricular dysplasia are also discussed.

The differences between posteroseptal and the other atrioventricular accessory pathways: the coronary sinus morphology and the conduction over accessory pathways

62.2±4.5 mV, p<0.0t), maximal diastolic potential (80.4±2.2 vs. 58.7±5.4 mV, p<0.05), dV/dt (156.6±12.7 vs. 26.4±6.5 V/sec, p<0.05), and ADPg0 (208.3±7.2 vs. 145.2±7.4 ms, p<0.01), consistent with slow conduction and unidirectional block occurred in the BZ. In conclusion, sustained monomorphic VTs developed after MI were due to functional spiral wave reentry or anatomic macroreentry around the infarction area. Both types of reentries involved in the BZ with delayed conduction and unidirectional block. Background: Increased left atdal volume (LAV) is associated with a higher risk of recurrent atdal fibdllation (AF) and atdal arrhythmias. Two-dimensional (2-D) transthorecic echocardio- graphy is validated as a reliable method by which to assess LAV compared to cine-computed tomography (cine-CT). Using the biplane method of disks, LAV measured by transthoracic echocardiography is well correlated with that obtained by cine-CT, but under estimates the LAV by 20-32%. Magnetic electroanatomic mapping (MEAM) is valuable for defining the ana- tomic location of catheter-based electrophysiologic recordings by creating a detailed shell of the endocardial anatomy in three-dimensional that can help guide focal AF ablation. We sought to validate the accuracy of volume measurements by MEAM by compadng MEAM LAV measurements against those measured by two-dimensionaJ transthoracic echocardiogrephy. Methods: Forty-seven patients underwent 2-D echocardiography and detailed MEAM of the left atdum (LA). The entire LA was mapped with 78-224 distinct points (mean 126 ± 37) acquired dudng atdal end-diastole, MEAM measurement of LAV was computed by using the built-in volume function of the Biosense TM system. The LAV was assessed using 2-D tran- sthoraclc echocardiography by the biplane methods of disks. The endocardial outlined was digitally traced in the apical 4-chamber and 2-chamber views at end-atrial diastole with exclu- sion of the pulmonic veins and appendage. Results: The LAV by 2-D echocardiography was 92.7 + 25.9 cc versus the LAV by MEAM which was 125.4 + 28,4 cc. There is good correlation between the results of echocardio- graphy and MEAM (r=0.90, p<0.001) for LAV, although the average value obtained by echocardiography is about 26% lower than that obtained by MEAM. Conclusions: Magnetic electroanatomic catheter mapping appears to be a retiable method by which to assess LAV. The results of MEAM correlate well with the echocardiographic assessments of LAV. Echocardiography underestimates LAV by a similar percentage when compared to MEAM as it does when compared to cine-CT. MEAM may prove useful in track- ing LAV with repeat mapping procedures and helping to plan post.ablative management. Bmckorounds: There were few reports about the differences between posteroseptal and the other atdoventdcular accessory pathways lAPs) in anatomy and electrophysiology. Methods: The size and shape of coronary sinus (CS) were measured in 21 patients with posteroseptal APs (11 right and 10 Jeff posteroseptal wall), 83 with the other APs (63 left lateral, 13 right lateral, 7 right anteroseptal wall) and 25 control subjects after CS angiogra- phy. CS diameter and morphoiogic features were measured. In 38 patients with APs, we investigated the electrophysiological charactedstics about anterograde and retrograde con- duction over APs, Rssults: The proximal CS in patients with posteroseptal APs was larger than in those with the other APs and the control (13.8 +/- 1.3 mm vs. 10.9 +/- 2.1 mm (p < 0.001) and 9.7 +/- 1.5 mm (p < 0.001), respectively). At a distance of 5 mm from the CS ostium, the CS mea- sured 10.8 +/- 0.8 mm, compared with 8.9 +/- 1.9 mm (p < 0.05) and 8.2 +/- 1.8 mm (p < 0.01). The dilatation persisted 10 mm into the CS, with the measurement of 8.6 +/- 1.2 mm, compared with 7.5 +/- 1.8 mm (p<0.05) and 7.2 +/- 1.7 mm (p<0.05). There were no differ- ences in these distal diameter, tn 67% of patients with posteroseptal APs, the proximal CS had the wind-cone appearance. This morphology was found in 16% of patients with the other APs. In all of control subjects and 84% of patients with the other APs, the CS was the tubular. Only 1 patient with a posteresaptal AP had retrograde and anterograde decremen- tal conduction over the AP. Three patients with postereseptal APs, 2 with left lateral, 2 with dght rataral and 1 with anteroseptal had only retmgrada conduction. Posteroseptal APs with dacramental conduction were located only in the right side. C.onclusions: The larger size of proximal CS was a structural characteristics in patients with posterosaptal APs. The appearance of proximal CS was like a wind-cone in these patients. Right posteroseptal APs were prone to have the high incidences of decremental conduction. These findings may have a clue to trace arrthythmia pathogenesis to its origin.

A comparison of left atrial volume measured by magnetic endocardial catheter mapping versus two-dimensional transthoracic echocardiography

62.2±4.5 mV, p<0.0t), maximal diastolic potential (80.4±2.2 vs. 58.7±5.4 mV, p<0.05), dV/dt (156.6±12.7 vs. 26.4±6.5 V/sec, p<0.05), and ADPg0 (208.3±7.2 vs. 145.2±7.4 ms, p<0.01), consistent with slow conduction and unidirectional block occurred in the BZ. In conclusion, sustained monomorphic VTs developed after MI were due to functional spiral wave reentry or anatomic macroreentry around the infarction area. Both types of reentries involved in the BZ with delayed conduction and unidirectional block. Background: Increased left atdal volume (LAV) is associated with a higher risk of recurrent atdal fibdllation (AF) and atdal arrhythmias. Two-dimensional (2-D) transthorecic echocardio- graphy is validated as a reliable method by which to assess LAV compared to cine-computed tomography (cine-CT). Using the biplane method of disks, LAV measured by transthoracic echocardiography is well correlated with that obtained by cine-CT, but under estimates the LAV by 20-32%. Magnetic electroanatomic mapping (MEAM) is valuable for defining the ana- tomic location of catheter-based electrophysiologic recordings by creating a detailed shell of the endocardial anatomy in three-dimensional space that can help guide focal AF ablation. We sought to validate the accuracy of volume measurements by MEAM by compadng MEAM LAV measurements against those measured by two-dimensionaJ transthoracic echocardiogrephy. Methods: Forty-seven patients underwent 2-D echocardiography and detailed MEAM of the left atdum (LA). The entire LA was mapped with 78-224 distinct points (mean 126 ± 37) acquired dudng atdal end-diastole, MEAM measurement of LAV was computed by using the built-in volume function of the Biosense TM system. The LAV was assessed using 2-D tran- sthoraclc echocardiography by the biplane methods of disks. The endocardial outlined was digitally traced in the apical 4-chamber and 2-chamber views at end-atrial diastole with exclu- sion of the pulmonic veins and appendage. Results: The LAV by 2-D echocardiography was 92.7 + 25.9 cc versus the LAV by MEAM which was 125.4 + 28,4 cc. There is good correlation between the results of echocardio- graphy and MEAM (r=0.90, p<0.001) for LAV, although the average value obtained by echocardiography is about 26% lower than that obtained by MEAM. Conclusions: Magnetic electroanatomic catheter mapping appears to be a retiable method by which to assess LAV. The results of MEAM correlate well with the echocardiographic assessments of LAV. Echocardiography underestimates LAV by a similar percentage when compared to MEAM as it does when compared to cine-CT. MEAM may prove useful in track- ing LAV with repeat mapping procedures and helping to plan post.ablative management. Rssults: The proximal CS in patients with posteroseptal APs was larger than in those with the other APs and the control (13.8 +/- 1.3 mm vs. 10.9 +/- 2.1 mm (p < 0.001) and 9.7 +/- 1.5 mm (p < 0.001), respectively). At a distance of 5 mm from the CS ostium, the CS mea- sured 10.8 +/- 0.8 mm, compared with 8.9 +/- 1.9 mm (p < 0.05) and 8.2 +/- 1.8 mm (p < 0.01). The dilatation persisted 10 mm into the CS, with the measurement of 8.6 +/- 1.2 mm, compared with 7.5 +/- 1.8 mm (p<0.05) and 7.2 +/- 1.7 mm (p<0.05). There were no differ- ences in these distal diameter, tn 67% of patients with posteroseptal APs, the proximal CS had the wind-cone appearance. This morphology was found in 16% of patients with the other APs. In all of control subjects and 84% of patients with the other APs, the CS was the tubular. Only 1 patient with a posteresaptal AP had retrograde and anterograde decremen- tal conduction over the AP. Three patients with postereseptal APs, 2 with left lateral, 2 with dght rataral and 1 with anteroseptal had only retmgrada conduction. Posteroseptal APs with dacramental conduction were located only in the right side.

Nonfluoroscopic magnetic electroanatomic mapping to facilitate focal pulmonary veins ablation for paroxysmal atrial fibrillation.

RF ablation of ectopic foci in the pulmonary veins (PVs) is a promising treatment for patients with paroxysmal AF. The aim of this study was to evaluate the feasibility of using nonfluoroscopic magnetic electroanatomic mapping of PV during spontaneous or induced ectopy to facilitate focal ablation procedure. The study included 35 patients with drug refractory paroxysmal AF who underwent focal RF ablation of the PV. In 10 (29%) patients, mapping and RF ablation procedures were performed using the nonfluoroscopic magnetic electroanatomic mapping system to enable automatic capture of the location and the timing of the ectopy. As a control, 25 patients underwent conventional endocardial activation mapping technique. There were no significant differences in the clinical characteristics between the two groups. Overall procedural duration was similar between them (199 +/- 52 vs 221 +/- 82 minutes, P > 0.05). However, the mean fluoroscopy time (25 +/- 6 vs 52 +/- 12 minutes, P = 0.01) and the mean number of RF applications (5 +/- 3 vs 12 +/- 9, P = 0.02) were significantly less in patients who underwent electroanatomic mapping. There were no significant differences between the two groups in the acute (90 vs 84%) and long-term success rate (60 vs 56%) after a mean follow-up of 12 +/- 9 months. In conclusion, RF ablation of ectopic foci using nonfluoroscopic magnetic electroanatomic mapping of PVs during spontaneous or induced ectopy is useful even in patients with a limited number of ectopy, and is associated with a similar success rate, but less fluoroscopy time and RF application compared to the conventional approach.

Clinical characteristics and catheter ablation of left ventricular outflow tract tachycardia.

Left ventricular outflow tract (LVOT) tachycardia is an uncommon form of idiopathic ventricular tachycardia (IVT). The underlying mechanism of this arrhythmia appears to be cyclic AMP-medicated triggered activity. The tachycardia occurs in the absence of structural heart disease and is generally benign, presenting commonly as palpitations and presyncope. It can manifest either a right or left bundle branch block morphology with an inferior axis. Subtle variations in the QRS morphology in leads I, V1, and V2 can help in localizing the anatomic site of origin (SOO). The arrhythmia is typically responsive to a variety of pharmacologic agents (beta-blockers, calcium channel blockers, Class I and II agents). Radiofrequency catheter ablation of LVOT tachycardia SOO as determined by pace mapping is quite efficacious (success rates of 90%). Magnetic electroanatomic mapping augments this by permitting three-dimensional catheter mapping and reproducible localization of the SOO. Catheter ablation should be considered relatively early in patients who experience severe symptoms with their arrhythmia and have failed, or are reluctant to take medications for the disorder.

In-vivo electrophysiologic assessment of left atrial muscle sleeves in pulmonary veins with magnetic electroanatomic mapping in patients with paroxysmal atrial fibrillation Manisha S. Ashar, David J. Callans, Henry H. Hsia, Andrea M. Russo, Erica S. Zado, Francis E. Marchlinski. University of Pennsylvania Health Systems, Philadelphia, PA

In-vivo electrophysiologic assessment of left atrial muscle sleeves in pulmonary veins with magnetic electroanatomic mapping in patients with paroxysmal atrial fibrillation Manisha S. Ashar, David J. Callans, Henry H. Hsia, Andrea M. Russo, Erica S. Zado, Francis E. Marchlinski. University of Pennsylvania Health Systems, Philadelphia, PA

Magnetic electroanatomical mapping for ablation of focal atrial tachycardias.

Uniform success for ablation of focal atrial tachycardias has been difficult to achieve using standard catheter mapping and ablation techniques. In addition, our understanding of the complex relationship between atrial anatomy, electrophysiology, and surface ECG P wave morphology remains primitive. The magnetic electroanatomical mapping and display system (CARTO) offers an on-line display of electrical activation and/or signal amplitude related to the anatomical location of the recorded sites in the mapped chamber. A window of electrical interest is established based on signals timed from an electrical reference that usually represents a fixed electrogram recording from the coronary sinus or the atrial appendage. This window of electrical interest is established to include atrial activation prior to the onset of the P wave activity associated with the site of origin of a focal atrial tachycardia. Anatomical and electrical landmarks are defined with limited fluoroscopic imaging support and more detailed global chamber and more focal atrial mapping can be performed with minimal fluoroscopic guidance. A three-dimensional color map representing atrial activation or voltage amplitude at the magnetically defined anatomical sites is displayed with on-line data acquisition. This display can be manipulated to facilitate viewing from any angle. Altering the zoom control, triangle fill threshold, clipping plane, or color range can all enhance the display of a more focal area of interest. We documented the feasibility of using this single mapping catheter technique for localizing and ablating focal atrial tachycardias. In a consecutive series of 8 patients with 9 focal atrial tachycardias, the use of the single catheter CARTO mapping system was associated with ablation success in all but one patient who had a left atrial tachycardia localized to the medial aspect of the orifice of the left atrial appendage. Only low power energy delivery was used in this patient because of the unavailability of temperature monitoring in the early version of the Navistar catheter, the location of the arrhythmia, and the history of arrhythmia control with flecainide. No attempt was made to limit fluoroscopy time in our study population. Nevertheless, despite data acquisition from 120-320 anatomically distinct sites during global and more detailed focal atrial mapping, total fluoroscopy exposure was typically < 30 minutes and was as little as 12 minutes. The detailed display capabilities of the CARTO system appear to offer the potential of enhancing our understanding of atrial anatomy, atrial activation, and their relationship to surface ECG P wave morphology during focal atrial tachycardias.