Endocardial Mapping Research Articles

Importance of Ventricular Tachycardia Induction and Mapping for Patients Referred for Epicardial Ablation.

Many nonischemic cardiomyopathy (NICMP) patients referred for catheter ablation of ventricular tachycardia (VT) undergo an initial epicardial approach under general anesthesia (GA). However, GA may suppress inducibility and decrease tolerance of induced VT, leaving substrate modification as the sole ablation method. Determine the utility of a strategy of initial programmed electrical stimulation (PES) under light sedation in patients referred for epicardial ablation of VT. Of 68 NICMP patients referred for VT ablation, 25 were referred specifically for epicardial ablation. All patients underwent PES under conscious sedation, with conversion to GA and epicardial access only if VT morphology and/or endocardial mapping suggested an epicardial substrate. VT was induced with PES in 24 of 25 patients (mean age 52 years; 76% male; ejection fraction 38 ± 18%). VT was hemodynamically tolerated in 63% and unstable in 38% of patients. The noninducible/unstable VT patients underwent substrate modification based on voltage and pace mapping. Of the patients with stable VT, 73% were mapped and ablated endocardially (six right ventricle, three left ventricle, one left coronary cusp, one middle cardiac vein), and 33% were successfully ablated in areas of normal endocardial voltage. After ablation, the clinical VT was noninducible in all patients. After mean follow-up of 10 months, 80% were free of implantable cardioverter defibrillator shocks or sustained VT. An initial approach of PES and entrainment mapping under conscious sedation is critically important for patients with NICMP referred for epicardial ablation. Empiric ablation of endocardial/epicardial scar would have missed the clinical VT in 20% of patients.

Injection of cold saline for diagnosis of intramural ventricular arrhythmias

The failure to identify a successful target site for catheter ablation despite extensive endocardial and epicardial mapping is a common feature for an intramural site of origin of a ventricular arrhythmia. The purpose of this study was to assess whether transient suppression of premature ventricular complexes (PVCs) by injection of cold saline into the distal coronary venous system can identify an intramural focus. Cold saline (room temperature) was injected through an irrigated-tip catheter into the distal coronary venous system in a consecutive series of 26 patients with frequent PVCs referred for catheter ablation. PVCs were temporarily suppressed in 11 of 26 patients during injection of cold saline. Extensive mapping suggested the presence of an intramural site of origin in 9 of 11 patients with PVC suppression by cold saline but in only 1 of 15 patients in whom PVCs were not suppressed. The suppression of PVCs by cold saline was associated with the presence of an intramural PVC focus with an accuracy of 88% (sensitivity 90%, specificity 88%, positive predictive value 82%, negative predictive value 93%, P = .0002). Temporary suppression of PVCs by cold saline infused into the distal coronary venous system and the perforator veins strongly suggests the presence of an intramural septal focus of the PVCs.

A swine model of infarct-related reentrant ventricular tachycardia: Electroanatomic, magnetic resonance, and histopathological characterization

Human ventricular tachycardia (VT) after myocardial infarction usually occurs because of subendocardial reentrant circuits originating in scar tissue that borders surviving myocardial bundles. Several preclinical large animal models have been used to further study postinfarct reentrant VT, but with varied experimental methodologies and limited evaluation of the underlying substrate or induced arrhythmia mechanism. We aimed to develop and characterize a swine model of scar-related reentrant VT. Thirty-five Yorkshire swine underwent 180-minute occlusion of the left anterior descending coronary artery. Thirty-one animals (89%) survived the 6-8-week survival period. These animals underwent cardiac magnetic resonance imaging followed by electrophysiology study, detailed electroanatomic mapping, and histopathological analysis. Left ventricular (LV) ejection fraction measured using CMR imaging was 36% ± 6.6% with anteroseptal wall motion abnormality and late gadolinium enhancement across 12.5% ± 4.1% of the LV surface area. Low voltage measured using endocardial electroanatomic mapping encompassed 11.1% ± 3.5% of the LV surface area (bipolar voltage ≤1.5 mV) with anterior, anteroseptal, and anterolateral involvement. Reentrant circuits mapped were largely determined by functional rather than fix anatomical barriers, consistent with "pseudo-block" due to anisotropic conduction. Sustained monomorphic VT was induced in 28 of 31 swine (90%) (67 VTs; 2.4 ± 1.1; range 1-4) and characterized as reentry. VT circuits were subendocardial, with an arrhythmogenic substrate characterized by transmural anterior scar with varying degrees of fibrosis and myocardial fiber disarray on the septal and lateral borders. This is a well-characterized swine model of scar-related subendocardial reentrant VT. This model can serve as the basis for further investigation in the physiology and therapeutics of humanlike postinfarction reentrant VT.

Mechanisms of Long-Duration Ventricular Fibrillation in Human Hearts and Experimental Validation in Canine Purkinje Fibers

ObjectivesThis study sought to determine the characteristics of human LDVF, particularly as it contrasts with short-duration VF (SDVF), and evaluate the role of Purkinje fibers in its maintenance. BackgroundThe electrophysiological mechanisms of long-duration ventricular fibrillation (LDVF) have not been studied in the human heart. MethodsVF was induced in 12 human Langendorff hearts, and the hearts were examined from initiation to LDVF (10 min). Endocardial, epicardial, and transmural plunge needle mapping were performed on the hearts. Simulated LDVF was studied in canine hearts to determine the potential role of Purkinje fiber automaticity. ResultsThe mean age at transplant was 48 ± 20 years, and the mean ejection fraction was <20%. The mean cycle length of local activation times on the endocardium was 252 ± 66 ms in SDVF and 441 ± 80 ms in LDVF (p = 0.0002). On the endocardium and the epicardium in LDVF, cycle length was 441 ± 80 ms and 590 ± 88 ms, respectively (p = 0.0002). No endocardial to epicardial activation frequency gradient was seen in SDVF. Simultaneous transmural needle activation was most common in SDVF, whereas endocardial to epicardial activation was most common in LDVF (47.7% and 38.8% of activations, respectively [p = 0.031]). Re-entry was less common in LDVF, and over time, wave break (i.e., nontransmural propagation of wave fronts) developed. Isochronal maps of the left ventricular endocardium in LDVF identified Purkinje potentials as preceding and predominating endocardial activations. In explanted canine heart preparations, rapid pacing led to spontaneous Purkinje fiber activity that was dependent on pacing rate and duration. ConclusionsLDVF in human hearts is characterized by focal endocardial activity with mid-myocardial wave break and not by re-entry. This arrhythmia is modulated by rapid activations in early VF that lead to spontaneous Purkinje fiber activity.

Endovascular catheter ablation of ventricular tachycardia in a patient with a surgically repaired congenital left ventricular aneurysm.

We present a patient with a congenital left ventricular aneurysm who visited our outpatient clinic for a routine check-up and, during this visit, lost consciousness due to sustained ventricular tachycardia. In our patient, endocardial mapping revealed extensive conduction abnormalities, and successful ablation was accomplished at the endocardial surface.

Temporal-component analysis of diastolic electrograms in ventricular tachycardia differentiates nonvulnerable regions of the circuit.

Successful activation mapping of ventricular tachycardia (VT) is dependent on the identification of a region of diastolic conduction by use of point-by-point sequential mapping. It is important to identify the site of transition from diastolic conduction to systolic activation of healthy myocardium (exit site) and differentiate this from nonvulnerable regions of the circuit. We sought to determine the temporal and component characteristics of exit-site electrograms using simultaneous multielectrode endocardial mapping and to differentiate them from bystander sites during activation mapping. Sixteen VTs induced in 12 patients with ischemic cardiomyopathy who underwent multielectrode mapping during VT performed with a custom-made 112-bipolar-electrode endocardial array were analyzed retrospectively. The activation sequence in systole and diastole was annotated, and the timing at exit and bystander sites of the near-field component was characterized in relation to surface electrocardiogram activation and to the far-field component. Spectral content of bipolar electrograms recorded at these sites was additionally analyzed to identify the near-field to far-field interval. The mean activation time at exit sites was 60.0 ± 31.5 ms (range 21-113 ms) ahead of surface QRS but was not significantly different from bystander sites (72.0 ± 55.0 ms, P = .63). However, the time delay from local to far-field activity was significantly lower at exit sites than at bystander sites (24.9 ± 15.6 vs. 86.6 ± 92.0 ms, P = .003), which was confirmed by spectral analysis (10.0 ± 13.1 vs. 89.0 ± 64.5 ms, P = .003). Our analysis suggests that temporal-component analysis of diastolic electrograms during activation mapping of VT provides a practical method to differentiate nonvulnerable sites from the exit site without the need for pacing maneuvers.

Position of totally thoracoscopic surgical ablation in the treatment of atrial fibrillation: an alternative method of conduction testing.

Recent advances in surgical techniques and understanding of the pathophysiology of atrial fibrillation has led to the development of a less invasive thoracoscopic surgical treatment including video-assisted bilateral pulmonary vein isolation using bipolar radiofrequency ablation clamps. More recently, the same operation became possible via a totally thoracoscopic approach.In this paper we describe technical aspects of the thoracoscopic approach to surgical treatment of AF and discuss its features, benefits and limitations. Furthermore, we present a new alternative technique of conduction testing using endoscopic multi-electrode recording catheters.An alternative electrophysiological mapping strategy involves a multi-electrode recording catheter designed primarily for percutaneous endocardial electrophysiologic mapping procedure. According to our initial experience, the recordings obtained from the multi-electrode catheters positioned around the pulmonary veins are more accurate than the recordings obtained from the multifunctional ablation and pacing pen.The totally thoracoscopic surgical ablation approach is a feasible and efficient treatment strategy for atrial fibrillation. The conduction testing can be easily and rapidly performed using a multifunctional pen or multi-electrode recording catheter.

(576) - Detailed Endocardial Mapping Around the Left Ventricular Assist Device Inflow Cannula Facilitates Successful Ablation of Ventricular Tachycardia

Ventricular tachycardia (VT) is an important cause of morbidity after left ventricular assist device (LVAD) implantation. We sought to demonstrate feasibility and efficacy of VT ablation in this population, and to determine how often ablation is required around the LVAD inflow cannula.

Combined analysis of unipolar and bipolar voltage mapping identifies recurrences after unmappable scar-related ventricular tachycardia ablation.

Scars causing ventricular tachycardia can extend deep to and beyond bipolar low-voltage areas (LVAs) and they may be a reason for endocardial ablation failure. Analysis of endocardial unipolar voltage maps has been used to detect scar transmurality and epicardial scar. We hypothesized that endocardial unipolar LVA around the overlying bipolar LVA may predict endocardial ablation recurrence in patients with structural heart disease undergoing substrate modification. Twenty consecutive patients with structural heart disease (11 ischaemic and 9 non-ischaemic cardiomyopathy) and undergoing substrate modification due to unmappable ventricular tachycardia (VT) (18 males, 51 ± 11 age, LVEF: 36 ± 7%) were retrospectively reviewed. Bipolar LVA defined as <1.5 mV and unipolar LVA defined as <8.3 mV, respectively, on electro-anatomic mapping system. Peripheral unipolar LVA (pUni-LVA) surrounding bipolar LVA was measured and compared patients with and without VT recurrence at 6-month follow-up period. : Mean unipolar voltage and mean bipolar voltage was 6.26 ± 4.99 and 1.90 ± 2.30 mV, respectively. Bipolar voltage and unipolar voltage in corresponding points were correlated (r = 0.652, P = 0.0001). In all patients, unipolar LVAs were larger than the bipolar LVAs. Bipolar LVA (91.1 ± 93.5 vs. 87.5 ± 47.5 cm(2), P = 0.91) and unipolar LVA (148.1 ± 96.3 vs. 104.7 ± 44.2 cm(2), P = 0.21) were similar in patients with and without VT recurrence, respectively. Peripheral unipolar LVA was significantly larger in patients with VT recurrence than without (57.0 ± 40.4 vs. 17.2 ± 12.9 cm(2), P = 0.01). In patients with structural heart disease and unmappable VT, pUni-LVA surrounding bipolar scar predicts recurrence of VT ablation. The results of this pilot study highlight the importance of intramural/epicardial substrate on endocardial VT ablation outcome.

Quantification of the transmural dynamics of atrial fibrillation by simultaneous endocardial and epicardial optical mapping in an acute sheep model.

Therapy strategies for atrial fibrillation based on electric characterization are becoming viable personalized medicine approaches to treat a notoriously difficult disease. In light of these approaches that rely on high-density surface mapping, this study aims to evaluate the presence of 3-dimensional electric substrate variations within the transmural wall during acute episodes of atrial fibrillation. Optical signals were simultaneously acquired from the epicardial and endocardial tissue during acute fibrillation in ovine isolated left atria. Dominant frequency, regularity index, propagation angles, and phase dynamics were assessed and correlated across imaging planes to gauge the synchrony of the activation patterns compared with paced rhythms. Static frequency parameters were well correlated spatially between the endocardium and the epicardium (dominant frequency, 0.79 ± 0.06 and regularity index, 0.93 ± 0.009). However, dynamic tracking of propagation vectors and phase singularity trajectories revealed discordant activity across the transmural wall. The absolute value of the difference in the number, spatial stability, and temporal stability of phase singularities between the epicardial and the endocardial planes was significantly >0 with a median difference of 1.0, 9.27%, and 19.75%, respectively. The number of wavefronts with respect to time was significantly less correlated and the difference in propagation angle was significantly larger in fibrillation compared with paced rhythms. Atrial fibrillation substrates are dynamic 3-dimensional structures with a range of discordance between the epicardial and the endocardial tissue. The results of this study suggest that transmural propagation may play a role in atrial fibrillation maintenance mechanisms.

Late gadolinium enhancement on cardiac magnetic resonance represents the depolarizing and repolarizing electrically damaged foci causing malignant ventricular arrhythmia in hypertrophic cardiomyopathy.

The presence of a myocardial scar detected by late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) has been described as a predictor of all-cause mortality in hypertrophic cardiomyopathy (HCM). However, the detailed spatial relationship between LGE site and electrical abnormality is unclear in high-risk HCM with malignant arrhythmia. The purpose of this study was to elucidate the detailed relationship between the site on CMR imaging and the electrically damaged site, a potential origin of ventricular arrhythmias in patients with HCM. Fifty consecutive HCM patients underwent contrast-enhanced CMR. Of those patients, 18 patients with ventricular tachycardia underwent electrophysiology study including endocardial mapping of the left ventricle (LV). The LGE area was calculated at 12 different LV sites: anterior, lateral, posterior, and septal segments of the basal, middle, and apical portions. At each LV site, the bipolar electrogram, effective refractory period (ERP), and monophasic action potential were recorded. LGE-positive segments demonstrated a significantly lower amplitude (4.0 ± 2.8 mV vs 7.3 ± 3.6 mV; P < .001), longer duration (54.7 ± 17.8 vs 40.6 ± 7.8 ms; P < .001), longer ERP (320 ± 42 ms vs 284 ± 37 ms; P = .001), and longer monophasic action potential duration measured at 90% repolarization (321 ± 19 ms vs 283 ± 25 ms; P < .001) than did LGE-negative segments. The LGE area negatively correlated with the amplitude (r = -0.59; P < .001) and positively correlated with the duration (r = 0.64; P < .001), ERP (r = 0.44; P < .001), and action potential duration measured at 90% repolarization (r = 0.63; P < .001). All the observed VTs originated from LGE-positive segments. The spatial distribution of LGE significantly correlates with depolarizing and repolarizing electrical damage in high-risk HCM with malignant ventricular arrhythmia.

Correlation of scar in cardiac MRI and high-resolution contact mapping of left ventricle in a chronic infarct model.

BackgroundEndocardial mapping for scars and abnormal electrograms forms the most essential component of ventricular tachycardia ablation. The utility of ultra‐high resolution mapping of ventricular scar was assessed using a multielectrode contact mapping system in a chronic canine infarct model.MethodsChronic infarcts were created in five anesthetized dogs by ligating the left anterior descending coronary artery. Late gadolinium‐enhanced magnetic resonance imaging (LGE MRI) was obtained 4.9 ± 0.9 months after infarction, with three‐dimensional (3D) gadolinium enhancement signal intensity maps at 1‐mm and 5‐mm depths from the endocardium. Ultra‐high resolution electroanatomical maps were created using a novel mapping system (Rhythmia Mapping System, Rhythmia Medical/Boston Scientific, Marlborough, MA, USA) Rhythmia Medical, Boston Scientific, Marlborough, MA, USA with an 8.5F catheter with mini‐basket electrode array (64 tiny electrodes, 2.5‐mm spacing, center‐to‐center).ResultsThe maps contained 7,754 ± 1,960 electrograms per animal with a mean resolution of 2.8 ± 0.6 mm. Low bipolar voltage (<2 mV) correlated closely with scar on the LGE MRI and the 3D signal intensity map (1‐mm depth). The scar areas between the MRI signal intensity map and electroanatomic map matched at 87.7% of sites. Bipolar and unipolar voltages, compared in 592 electrograms from four MRI‐defined scar types (endocardial scar, epicardial scar, mottled transmural scar, and dense transmural scar) as well as normal tissue, were significantly different. A unipolar voltage of <13 mV correlated with transmural extension of scar in MRI. Electrograms exhibiting isolated late potentials (ILPs) were manually annotated and ILP maps were created showing ILP location and timing. ILPs were identified in 203 ± 159 electrograms per dog (within low‐voltage areas) and ILP maps showed gradation in timing of ILPs at different locations in the scar.ConclusionsUltra‐high resolution contact electroanatomical mapping accurately localizes ventricular scar and abnormal myocardial tissue in this chronic canine infarct model. The high fidelity electrograms provided clear identification of the very low amplitude ILPs within the scar tissue and has the potential to quickly identify targets for ablation.

Innovative techniques in atrial fibrillation therapy

Pulmonary vein isolation (PVI) is the established cornerstone in most catheter-based ablation treatment strategies for atrial fibrillation (AF); however, it is still a challenge to create contiguous, transmural and permanent ablation lesions using radiofrequency current in combination with three-dimensional mapping systems. To overcome these limitations, innovative spiral mapping and ablation catheters as well as balloon-based ablation catheters incorporating alternative energy sources, such as cryoenergy and laser were developed and evaluated and have proved their potential for safe and clinically effective PVI. In addition, novel ablation strategies, such as identification and ablation of AF-inducing foci and/or AF-perpetuating rotors using either endocardial or epicardial mapping systems were introduced and are currently under clinical evaluation. The identification and modulation of atrial ganglionic plexi (GP) and, therefore, of the autonomous nervous system is another additive ablation approach which requires further clinical evaluation.

Distribution of abnormal potentials in chronic myocardial infarction using a real time magnetic resonance guided electrophysiology system.

BackgroundIdentification of viable slow conduction zones manifested by abnormal local potentials is integral to catheter ablation of ventricular tachycardia (VT) sites. The relationship between contrast patterns in cardiovascular magnetic resonance (CMR) and local electrical mapping is not well characterized. The purpose of this study was to identify regions of isolated, late and fractionated diastolic potentials in sinus rhythm and controlled-paced rhythm in post-infarct animals relative to regions detected by late gadolinium enhancement CMR (LGE-CMR).MethodsUsing a real-time MR-guided electrophysiology system, electrogram (EGM) recordings were used to generate endocardial electroanatomical maps in 6 animals. LGE-CMR was also performed and tissue classification (dense infarct, gray zone and healthy myocardium) was then correlated to locations of abnormal potentials.ResultsFor abnormal potentials in sinus rhythm, relative occurrence was equivalent 24%, 27% and 22% in dense scar, gray zone and healthy tissue respectively (p = NS); in paced rhythm, the relative occurrence of abnormal potentials was found to be different with 30%, 42% and 21% in dense scar, gray zone and healthy myocardium respectively (p = 0.001). For location of potentials, in the paced case, the relative frequency of abnormal EGMs was 19.9%, 65.4% and 14.7% in the entry, central pathway and exit respectively (p = 0.05), putative regions being defined by activation times.ConclusionsOur data suggests that gray zone quantified by LGE-CMR exhibits abnormal potentials more frequently than in healthy tissue or dense infarct when right ventricular apex pacing is used.

Adhering to the principles of surgical ablation.

The surgical treatment of atrial fibrillation (AF) has evolved since Dr James Cox introduced the maze procedure in 1987. The advent of innovative technologies for endocardial and epicardial ablation endeavouring to replicate Cox-maze III surgical lesions has ushered in a new era of innovative operations to address AF. The current report by Fengsrud et al. [1] elegantly demonstrates the technique of right monolateral thoracoscopic creation of an isolated pulmonary vein encircling box lesion using the Cobra Adhere XL radiofrequency device (Estech, Inc., San Ramon, CA, USA). In their preliminary experience with 10 stand-alone cases for AF of varying type and duration, they had no mortality, 1 re operation for bleeding and an average length of stay of 5.6 days. They performed guideline-directed Holter monitoring in 8 patients. Though 7 of 10 were free of AF at 12 months, only 4 were free from antiarrhythmic medications. The development of this technique started nearly a decade ago with the introduction of microwave epicardial ablation [2], demonstrating excellent safety and short-term efficacy. However, late results revealed that these outcomes were not effective in sustaining curative intent [3]. The result was the abandonment of the ablation technology but not the approach. Several others have replicated and modified the epicardial thoracoscopic procedure by making this a monolateral right-sided procedure. Initial experience with the epicardial Cobra Adhere XL vacuum-assisted radiofrequency ablation (Estech, Inc.) revealed good outcomes [4]. Applying rigorous monitoring, this technique demonstrated respectable freedom from paroxysmal AF and helped establish a hybrid approach to ablation that includes a secondary percutaneous endocardial mapping and ablation with an electrophysiology partnership [5–7]. The challenge with right mono-lateral approaches is the inability to surgically address the left atrial appendage (LAA). Though the necessity of LAA exclusion or excision is debated by authors of the current report [1], many surgeons and cardiologists continue to feel that addressing the LAA is a fundamental principle in the surgical approach to AF [8]. As we innovate with different ablative technologies, can we adhere to the principles of surgical ablation? Though definitions may evolve over time, these include a low morbidity procedure that durably restores sinus rhythm documented by Holter or continuous monitoring over 1 year, one that enables freedom from antiarrhythmic medications and one that mitigates the occurrence of stroke and improves quality of life. This latter point often relates to patients safely stopping anticoagulation. This is often not possible for several months or longer when the LAA remains intact post-ablation. Non-sternotomy approaches to treat AF include monoor bilateral thoracosopic or mini-thoracotomy, on-pump endocardial or off-pump epicardial surgical ablation. Each approach has demonstrated clinical effectiveness in several excellent centres worldwide [7]. However, a recent comparison between mini-right thoracotomy open Cox-maze, epicardial ablation and epicardial hybrid ablation with percutaneous treatment revealed that operations most closely following the full Cox-maze procedure may afford the best long-term results [9]. Regardless of the surgical approach or institutional expertise, when innovating with surgical ablation, being dedicated to the rigours of monitoring, follow-up, drug-free morbidity reduction and complete ablation, should be among the principles we adhere to for our patients and our specialty.

Accessory atrioventricular pathways refractory to catheter ablation: role of percutaneous epicardial approach.

Epicardial mapping and ablation of accessory pathways through a subxiphoid approach can be an alternative when endocardial or epicardial transvenous mapping has failed. We reviewed acute and long-term follow-up of 21 patients (14 males) referred for percutaneous epicardial accessory pathway ablation. There was a median of 2 previous failed procedures. All patients were highly symptomatic, 8 had atrial fibrillation (3 with cardiac arrest) and 13 had frequent symptomatic episodes of atrioventricular reentrant tachycardia. Six patients (28.5%) had a successful epicardial ablation. Five patients (23.8%) underwent a successful repeated endocardial mapping, and ablation after epicardial mapping yielded no early activation site. Epicardial mapping was helpful in guiding endocardial ablation in 2 patients (9.5%), showing that the earliest activation was simultaneous at the epicardium and endocardium. Four patients (19%) underwent successful open-chest surgery after failing epicardial/endocardial ablation. Two patients (9.5%) remained controlled under antiarrhythmic drugs after unsuccessful endocardial/epicardial ablation. Two patients had a coronary sinus diverticulum and one a right atrium to right ventricle diverticulum. Three patients acquired postablation coronary sinus stenosis. There was no major complication related to pericardial access. Percutaneous epicardial approach is an alternative when conventional endocardial or transvenous epicardial ablation fails in the elimination of the accessory pathway. A new attempt by endocardial approach was successful in a significant number of patients. Open-chest surgery may be required in symptomatic cases refractory to endocardial-epicardial approach.

Necessity of epicardial ablation for ventricular tachycardia after sequential endocardial approach

BackgroundCatheter ablation (CA) of ventricular tachycardia (VT) is an important treatment option in patients with structural heart disease (SHD) and implantable cardioverter defibrillator (ICD). A subset of patients requires epicardial CA for VT. ObjectiveThe purpose of the study was to assess the significance of epicardial CA in these patients after a systematic sequential endocardial approach. MethodsBetween January 2009 and October 2012 CA for VT was analyzed. A sequential CA approach guided by earliest ventricular activation, pacemap, entrainment and stimulus to QRS-interval analysis was used. Acute CA success was assessed by programmed ventricular stimulation. ICD interrogation and 24h-Holter ECG were used to evaluate long-term success. ResultsOne hundred sixty VT ablation procedures in 126 consecutive patients (114 men; age 65±12years) were performed. Endocardial CA succeeded in 250 (94%) out of 265 treated VT. For 15 (6%) VT an additional epicardial CA was performed and succeeded in 9 of these 15 VT. Long-term FU (25±18.2month) showed freedom of VT in 104 pts (82%) after 1.2±0.5 procedures, 11 (9%) suffered from repeated ICD shocks and 11 (9%) died due to worsening of heart failure. ConclusionsDespite a heterogenic substrate for VT in SHD, endocardial CA alone results in high acute success rates. In this study additional epicardial CA following a sequential endocardial mapping and CA approach was performed in 6% of VT.Thus, due to possible complications epicardial CA should only be considered if endocardial CA fails.

Electrical storm induced by cardiac resynchronization therapy is determined by pacing on epicardial scar and can be successfully managed by catheter ablation.

The mechanism of cardiac resynchronization therapy (CRT)-induced proarrhythmia remains unknown. We postulated that pacing from a left ventricular (LV) lead positioned on epicardial scar can facilitate re-entrant ventricular tachycardia. The aim of this study was to investigate the relationship between CRT-induced proarrhythmia and LV lead location within scar. Twenty-eight epicardial and 63 endocardial maps, obtained from 64 CRT patients undergoing ventricular tachycardia ablation, were analyzed. A positive LV lead/scar relationship, defined as a lead tip positioned on scar/border zone, was determined by overlaying fluoroscopic projections with LV electroanatomical maps. CRT-induced proarrhythmia occurred in 8 patients (12.5%). They all presented early with electrical storm (100% versus 39% of patients with no proarrhythmia; P<0.01), requiring temporary biventricular pacing discontinuation in half of cases. They more frequently presented with heart failure/cardiogenic shock (50% versus 7%; P<0.01), requiring intensive care management. Ventricular tachycardia was re-entrant in all. The LV lead location within epicardial scar was significantly more frequent in the proarrhythmia group (60% versus 9% P=0.03 on epicardial bipolar scar, 80% versus 17% P=0.02 on epicardial unipolar scar, and 80% versus 17% P=0.02 on any-epicardial scar). Ablation was performed within epicardial scar, close to the LV lead, and allowed CRT reactivation in all patients. CRT-induced proarrhythmia presented early with electrical storm and was associated with an LV lead positioning within epicardial scar. Catheter ablation allowed for resumption of biventricular stimulation in all patients.

Abstract 13804: Correlation between Electrocardiographic Features and Local Activation Pattern in Arrhythmogenic Right Ventricular Dysplasia

Background: Depolarization abnormalities in the terminal portion of the QRS are frequently seen in Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy (ARVD/C). The purpose of this study was to correlate the electroanatomic activation pattern of the RV endocardium and epicardium to the surface ECG. Methods: Thirty consecutive ARVD/C patients (Mean age 33.1 +/- 11.2 years, 16 (53%) men) underwent detailed endocardial and epicardial electroanatomical mapping (EAM). Local sinus rhythm activation was annotated at the sharpest intrinsic deflection of the bipolar electrogram, including late potentials. ECG features were classified into 5 major patterns; 1. Normal QRS (12 patients) 2. Epsilon wave (5 patients) 3. Incomplete RBBB (5 patients) 4. Atypical complete RBBB (6 patients) and 5. Prolonged terminal activation duration (TAD) (2 patients) Results: The earliest endocardial and epicardial RV activation occurred on the mid anteroseptal wall on all ECG patterns. Figure 1 represented activation area (purple) after the QRS or during the delayed depolarization phase. Nearly all endocardial and epicardial RV was activated well within the QRS duration in patients with normal QRS but was activated during R’ in patients with CRBBB. The delayed activation during Epsilon wave consistently occurred in basal anterior wall and basal angle of RV. In patients with TAD, the activation of RVOT and basal angle RV represented slurred S wave. Conclusion: ECG features in ARVD/C are correlated with late activation in specific regions of RV and total endocardial activation time. The delay activation of basal anterior wall and basal angle of RV represents the Epsilon wave in the right precordial ECG.

Abstract 12941: Disease Progression in Patients With Arrhythmogenic Right Ventricular Cardiomyopathy and Ventricular Tachycardia: A Longitudinal Study With Unipolar Voltage Mapping

Introduction: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is believed to result in progressive fibrofatty replacement of the RV myocardium with development of multiple ventricular tachycardia (VT) circuits. Endocardial unipolar voltage mapping has been shown to reliably identify epicardial and endocardial (epi-endo) scar in ARVC. Hypothesis: We studied the prevalence and mechanisms of disease progression in patients with ARVC and VT through longitudinal unipolar voltage mapping studies. Methods: Eighteen consecutive patients (age 38±14 years) who fulfilled the revised Task Force criteria for ARVC underwent two detailed sinus rhythm endocardial unipolar voltage maps (mean 348±118 points) performed a median of 36 months apart (interquartile range 21 to 36 months, minimum 9 months) as part of VT ablation procedures. Epi-endo scar was defined using established unipolar voltage cutoff (5.5 mV). The extent of RV scar and total RV volume was measured by a dedicated software. A &gt;5% increase in RV scar area or volume over follow-up was considered significant. Results: At baseline, all patients had evidence of epi-endo RV scar (mean 141±82 cm 2 ; 56±27% of the RV surface area). After a mean follow-up of 49±36 months, no significant progression of unipolar voltage scar was observed (mean 159±83 cm 2 , P=0.14; 63±27% of the RV surface area, P=0.07). Specifically, only 3 (17%) patients presented with progression of the RV scar &gt;5%. The RV volumes increased during follow-up (from 206±74 mL to 258±77 mL, P=0.0003), with the majority of patients (15/18, 83%) having a significant increase in the RV volume (mean increase = 38.9%). Only 3 (17%) patients had no change in both RV scar size and volume over time. Conclusions: In patients with ARVC and VT, progressive RV dilatation is almost uniformly observed, while rapid epi-endo scar progression is rare. These findings suggest that aggressive epi-endocardial substrate ablation should provide long-term VT control, and further research is needed to identify the mechanism(s) for and to prevent ongoing RV dilatation in these patients.