AF Ablation Using a Novel "Single-Shot" Map-and-Ablate Spherical Array Pulsed Field Ablation Catheter: 1-Year Outcomes of the First-in-Human PULSE-EU Trial.

BACKGROUND: During pulsed field ablation (PFA), electrode-tissue proximity optimizes lesion quality. Recently, a novel "single-shot" map-and-ablate spherical multielectrode PFA array catheter that is able to verify electrode-tissue contact was studied in a first-in-human trial of atrial fibrillation. OBJECTIVE: To report lesion durability data, safety and 12-months effectiveness outcomes. METHODS: The spherical PFA catheter, an all-in-one mapping and ablation system, was used to render anatomy and deliver biphasic pulses (ungated 1.7kV pulses; ∼40 sec/application). Ablation sites included pulmonary veins (PVs), and in selected patients, posterior wall (PW) and mitral isthmus (MI). Follow-up was invasive remapping at ∼3 months, ECGs, Holters at 6 and 12 months, and symptomatic and scheduled transtelephonic monitoring. The primary and secondary efficacy endpoints were acute PVI, PVI durability and atrial arrhythmia recurrence. RESULTS: In the 48-patient AF cohort (paroxysmal-48% / persistent-52%), lesion sets included PVI (n=48; 1.2 applications/PV), PW (n=20; 3.6 applications/PW) and MI (n=11; 2.9 applications/MI). Lesions were acutely successful for all 187 of 187 PVs (100%), 20 of 20 PWs (100%) and 10 of 11 MIs (91%). Pulse delivery time, LA catheter dwell time and procedure time was 61.5±32.8 seconds, 53.9±26.5 min and 87.8±29.8 min, respectively. Remapping (43 of 48 pts; 89.5%) revealed that 158 of 169 PVs (93.5%) were durably isolated. The only complication was a drug-responsive pericarditis. The 1-year Kaplan-Meier estimates of freedom from atrial arrhythmia were 84.2% (paroxysmal AF) and 80.0% (persistent AF). CONCLUSION: The single-shot spherical array PFA catheter can safely achieve durable lesions, translating into good clinical efficacy.

Pulsed Field Ablation to Treat Atrial Fibrillation: Autonomic Nervous System Effects.

BACKGROUND: During atrial fibrillation ablations using thermal energy, the treatment effect is attributed to not just pulmonary vein isolation (PVI), but also to modulation of the autonomic nervous system by ablation of cardiac ganglionated plexi (GP). OBJECTIVES: This study sought to assess the impact of pulsed field ablation (PFA) on the GP in patients undergoing PVI. METHODS: In the retrospective phase, heart rate was assessed pre- versus post-PVI using PFA, cryoballoon ablation, or radiofrequency ablation. In the prospective phase, a pentaspline PFA catheter was used in a protocol: 1) pre-PFA, high-frequency stimulation (HFS) identified GP sites by vagal effects; 2) PVI was performed assessing for repetitive vagal effects over each set of PF applications; 3) mapping defined PVI extent to identify those GP in the ablation zone; and 4) repeat HFS at GP sites to assess for persistence of vagal effects. RESULTS: Between baseline and 3 months, heart rates in the retrospective radiofrequency ablation (n = 40), cryoballoon (n = 40), and PFA (n = 40) cohorts increased by 8.9 ± 11.4, 11.1 ± 9.4, and -0.1 ± 9.2 beats/min, respectively (P= 0.01 PFA vs radiofrequency ablation; P= 0.01 PFA vs cryoballoon ablation). In the prospective phase, pre-PFA HFS in 20 additional patients identified 65 GP sites. During PFA, vagal effects were noted in 45% of first PF applications, persisting through all applications in 83%. HFS post-PFA reproduced vagal effects in 29 of 38 sites (76%) in low-voltage tissue. CONCLUSIONS: PFA has minimal effect on GP. Unlike with thermal ablation, the mechanism by which PFA treats atrial fibrillation is mediated solely by durable PVI.

PV Isolation Using a Spherical Array PFA Catheter: Application Repetition and Lesion Durability (PULSE-EU Study).

BACKGROUND: Preclinical studies have revealed that pulsed field ablation (PFA) lesion dimensions increase with repetitive applications at a similar electric field. OBJECTIVES: This study investigated whether pulmonary vein isolation (PVI) durability varies with single vs repetitive pulsed field (PF) applications. METHODS: Atrial fibrillation patients underwent PVI using a spherical multielectrode array PFA catheter delivered with a 19-F deflectable sheath under intracardiac echocardiographic guidance. Esophagogastroduodenoscopy and brain magnetic resonance imaging were performed within 1 to 3 days, and invasive remapping at ∼2 to 3 months. RESULTS: The patient cohort (n = 21; age 63 ± 11 years; 67% women) underwent PVI in either of 2 groups: group 1 (n = 11)-single PF application/PV; and group 2 (n = 10)-3 PF applications/PV. In both groups, PVI was acutely successful in all (100%) patients. Despite significantly longer pulse delivery times (75.2 ± 7.4 s/patient vs 24.5 ± 5.5 s/patient) the procedure times (73.2 ± 13.7 minutes vs 93.7 ± 18.5 minutes) were shorter with group 2 vs group 1. There was no stroke/transient ischemic attack, pericardial effusion, phrenic nerve injury, or esophageal complications. Esophagogastroduodenoscopy was normal in both groups of patients (n = 9). Screening brain magnetic resonance imaging revealed asymptomatic cerebral lesions (diffusion weighted imaging+/fluid attenuated inversion recovery-) in 3 of 16 (18.7%) patients. PV remapping revealed durable PVI in 62.5% PVs in group 1 (n = 10), compared with all 100% PVs in group 2 (n = 9); this translates to all PVs being durably isolated in 30% vs 100% (P < 0.05) of patients in groups 1 and 2, respectively. CONCLUSIONS: In his first-in-human trial, the "single-shot" spherical array PFA catheter was shown to safely isolate PVs. Repetitive PF application is key for lesion consolidation to maximize PVI durability.

Coronary Arterial Spasm During Pulsed Field Ablation to Treat Atrial Fibrillation.

BACKGROUND: Pulsed field ablation (PFA) has a unique safety profile when used to treat atrial fibrillation, largely related to its preferentiality for myocardial tissue ablation, in particular, esophageal sparing. A pentaspline catheter was the first such PFA system studied clinically for atrial fibrillation ablation; in these initial regulatory trials, the catheter was used for pulmonary vein isolation and left atrial posterior wall ablation. Since its regulatory approval in Europe, in clinical practice, physicians have ablated beyond pulmonary vein isolation and left atrial posterior wall ablation to expanded lesion sets in closer proximity to coronary arteries. This is an unstudied important issue because preclinical and clinical data have raised the potential for coronary arterial spasm. Herein, we studied the vasospastic potential of PFA lesion sets, both remote from and adjacent to coronary arteries. METHODS: During routine atrial fibrillation ablation using the pentaspline PFA catheter, coronary angiography was performed before, during, and after pulsed field applications. The lesion sets studied included: (1) those remote from the coronary arteries such as pulmonary vein isolation (n=25 patients) and left atrial posterior wall ablation (n=5), and (2) ablation of the cavotricuspid isthmus (n=20) that is situated adjacent to the right coronary artery. RESULTS: During pulmonary vein isolation and left atrial posterior wall ablation, coronary spasm did not occur, but cavotricuspid isthmus ablation provoked severe subtotal vasospasm in 5 of 5 (100%) consecutive patients, and this was relieved by intracoronary nitroglycerin in 5.5±3.5 minutes. ST-segment elevation was not observed. However, no patient (0%, P=0.004) had severe spasm if first administered parenteral nitroglycerin, either intracoronary (n=5) or intravenous (n=10), before treatment. CONCLUSIONS: Coronary vasospasm was not provoked during PFA at locations remote from coronary arteries, but when the energy is delivered adjacent to a coronary artery, PFA routinely provokes subclinical vasospasm. This phenomenon is attenuated by nitroglycerin, administered either post hoc to treat spasm or as prophylaxis.

Automated Noncontact Ultrasound Imaging and Ablation System for the Treatment of Atrial Fibrillation: Outcomes of the First-in-Human VALUE Trial.

BACKGROUND: Catheter ablation for atrial fibrillation (AF) using point-by-point radiofrequency energy or single-application one-shot balloons is either technically challenging or have limited ability to accommodate variable patient anatomy to achieve acute and durable pulmonary vein (PV) isolation. A novel ablation system employs low intensity collimated ultrasound (LICU)-guided anatomic mapping and robotic ablation to isolate PVs. In this first-in-human, single-center, multioperator trial, VALUE trial (VytronUS Ablation System for Treatment of Paroxysmal Atrial Fibrillation; NCT03639597) in patients with paroxysmal atrial fibrillation, this LICU system was evaluated to determine its safety, effectiveness in PV isolation, and freedom from recurrent atrial arrhythmias. METHODS: In the enrolled 52 patients with paroxysmal atrial fibrillation, ultrasound M-mode-based left atrial anatomies were successfully created, and ablation was performed under robotic control along an operator-defined lesion path. The LICU system software advanced over the course of the study: the last 13 patients were ablated with enhanced software. RESULTS: Acute PV isolation was achieved in 98% of PVs-using LICU-only in 77.3% (153/198) of PVs and requiring touch-up with a standard radiofrequency ablation catheter in 22.7% (45/198) PVs. The touch-up rate decreased to 5.8% (3/52) in patients undergoing LICU-ablation with enhanced software. Freedom from atrial arrhythmia recurrence was 79.6% (39/49 patients) at 12 months or 92.3% (12/13 patients) with the enhanced software. Major adverse events occurred in 3 patients (5.8%): one had transient diaphragmatic paralysis, one vascular access complication, and one had transient ST-segment elevation from air-embolism, without sequelae. CONCLUSIONS: In this first-in-human study, low- intensity collimated ultrasound-guided anatomic mapping and robotic ablation allows PV isolation with good chronic safety; PV isolation success is improving with device enhancements. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03639597.

Ablation of Atrial Fibrillation With Pulsed Electric Fields: An Ultra-Rapid, Tissue-Selective Modality for Cardiac Ablation.

OBJECTIVES: The authors report the first acute clinical experience of atrial fibrillation ablation with PEF-both epicardial box lesions during cardiac surgery, and catheter-based PV isolation. BACKGROUND: Standard energy sources rely on time-dependent conductive heating/cooling and ablate all tissue types indiscriminately. Pulsed electric field (PEF) energy ablates nonthermally by creating nanoscale pores in cell membranes. Potential advantages for atrial fibrillation ablation include: 1) cardiomyocytes have among the lowest sensitivity of any tissue to PEF-allowing tissue selectivity, thereby minimizing ablation of nontarget collateral tissue; 2) PEF is delivered rapidly over a few seconds; and 3) the absence of coagulative necrosis obviates the risk of pulmonary vein (PV) stenosis. METHODS: PEF ablation was performed using a custom over-the-wire endocardial catheter for percutaneous transseptal PV isolation, and a linear catheter for encircling the PVs and posterior left atrium during concomitant cardiac surgery. Endocardial voltage maps were created pre- and post-ablation. Continuous and categorical data are summarized and presented as mean ± SD and frequencies. RESULTS: At 2 centers, 22 patients underwent ablation under general anesthesia: 15 endocardial and 7 epicardial. Catheter PV isolation was successful in all 57 PVs in 15 patients (100%) using 3.26 ± 0.5 lesions/PV: procedure time 67 ± 10.5 min, catheter time (PEF catheter entry to exit) 19 ± 2.5 min, total PEF energy delivery time <60 s/patient, and fluoroscopy time 12 ± 4.0 min. Surgical box lesions were successful in 6 of 7 patients (86%) using 2 lesions/patient. The catheter time for epicardial ablation was 50.7 ± 19.5 min. There were no complications. CONCLUSIONS: These data usher in a new era of tissue-specific, ultrarapid ablation of atrial fibrillation.

Temperature-Controlled Radiofrequency Ablation for Pulmonary Vein Isolation in Patients With Atrial Fibrillation.

BACKGROUND: Saline irrigation improved the safety of radiofrequency (RF) ablation, but the thermal feedback for energy titration is absent. OBJECTIVES: To allow temperature-controlled irrigated ablation, a novel irrigated RF catheter was designed with a diamond-embedded tip (for rapid cooling) and 6 surface thermocouples to reflect tissue temperature. High-resolution electrograms (EGMs) from the split-tip electrode allowed rapid lesion assessment. The authors evaluated the preclinical and clinical performance of this catheter for pulmonary vein (PV) isolation. METHODS: Using the DiamondTemp (DT) catheter, pigs (n = 6) underwent discrete atrial ablation in a temperature control mode (60°C/50 W) until there was ∼80% EGM amplitude reduction. In a single-center clinical feasibility study, 35 patients underwent PV isolation with the DT catheter (study group); patients were planned for PV remapping after 3 months, regardless of symptomatology. A control group included 35 patients who underwent PV isolation with a standard force-sensing catheter. RESULTS: Porcine lesion histology revealed transmurality in 51 of 55 lesions (92.7%). In patients, all PVs were successfully isolated; no char or thrombus formation was observed. Compared with the control group, the study cohort had shorter mean RF application duration (26.3 ± 5.2 min vs. 89.2 ± 27.2 min; p < 0.001), shorter mean fluoroscopic time (11.2 ± 8.5 min vs. 19.5 ± 6.8 min; p < 0.001), and lower acute dormant PV reconduction (0 of 35 vs. 5 of 35; p = 0.024). At 3 months, 23 patients underwent remapping: 39 of 46 PV pairs (84.8%) remained durably isolated in 17 of these patients (73.9%). CONCLUSIONS: This first-in-human series demonstrated that temperature-controlled irrigated ablation produced rapid, efficient, and durable PV isolation. (ACT DiamondTemp Temperature-Controlled and Contact Sensing RF Ablation Clinical Trial for Atrial Fibrillation [TRAC-AF]; NCT02821351).

Single-site access robot-assisted epicardial mapping with a snake robot: preparation and first clinical experience.

CardioARM, a highly flexible "snakelike" medical robotic system (Medrobotics, Raynham, MA), has been developed to allow physicians to view, access, and perform complex procedures intrapericardially on the beating heart through a single-access port. Transthoracic epicardial catheter mapping and ablation has emerged as a strategy to treat arrhythmias, particularly ventricular arrhythmias, originating from the epicardial surface. The aim of our investigation was to determine whether the CardioARM could be used to diagnose and treat ventricular tachycardia (VT) of epicardial origin. Animal and clinical studies of the CardioARM flexible robot were performed in hybrid surgical-electrophysiology settings. In a porcine model study, single-port pericardial access, navigation, mapping, and ablation were performed in nine animals. The device was then used in a small, single-center feasibility clinical study. Three patients, all with drug-refractory VT and multiple failed endocardial ablation attempts, underwent epicardial mapping with the flexible robot. In all nine animals, navigation, mapping, and ablation were successful without hemodynamic compromise. In the human study, all three patients demonstrated a favorable safety profile, with no major adverse events through a 30-day follow-up. Two cases achieved technical success, in which an electroanatomic map of the epicardial ventricle surface was created; in the third case, blood obscured visualization. These results, although based on a limited number of experimental animals and patients, show promise and suggest that further clinical investigation on the use of the flexible robot in patients requiring epicardial mapping of VT is warranted.

Direct comparison of percutaneous circulatory support systems in specific hemodynamic conditions in a porcine model.

BACKGROUND: Several percutaneous circulatory support systems have been recently introduced into clinical practice for the treatment of cardiogenic shock or refractory nontolerated ventricular tachycardia, in support of high-risk catheter interventions and, occasionally, cardiopulmonary resuscitation. To date, however, a direct comparison of the available systems has not been performed. METHODS AND RESULTS: Adult female pigs (weight 50-60 kg) were used throughout the experiment. Under deep anesthesia and mechanical ventilation, 3 percutaneous circulatory support systems were compared: (1) right atrium-aorta, extracorporeal membrane oxygenation (n=4); (2) left atrium-aorta, TandemHeart system (n=4); (3) left ventricle-aorta, Impella 2.5 system (n=4), and (4) left ventricle-aorta with norepinephrine at 0.1 µg/kg per minute (n=4). Hemodynamic efficacy (mean arterial pressure) was measured at 3 specific conditions: ventricular pacing at 200 and 300 beats per minute, and ventricular fibrillation. Although no or only nonsignificant differences were found among the systems at ventricular pacing of 200 and 300 beats per minute, under ventricular fibrillation, the right atrium-aorta system was significantly the most efficacious, followed by the left atrium-aorta system and the left ventricle-aorta system (P<0.001). However, the left ventricle-aorta system with norepinephrine still maintained mean arterial pressure comparable with the left atrium-aorta system. CONCLUSIONS: Differences were seen in the hemodynamic efficacy of available percutaneous circulatory support systems, particularly under the most severe hemodynamic condition, ventricular fibrillation.

Incomplete occlusion of the left atrial appendage with the percutaneous left atrial appendage transcatheter occlusion device is not associated with increased risk of stroke.

BACKGROUND: Percutaneous approaches to left atrial appendage (LAA) closure are being developed for stroke prophylaxis in atrial fibrillation patients as an alternative to warfarin. Non-randomized clinical trials suggested that the first of these devices, the percutaneous left atrial appendage transcatheter occlusion (PLAATO) device, is safe and reduces stroke risk. Percutaneous closure has the potential limitation of incomplete exclusion of LAA from the systemic circulation, which could potentially lead to thrombus formation and stroke. This study investigated the interaction between residual blood flow in the LAA after percutaneous closure with PLAATO and risk of stroke. METHODS AND RESULTS: Data from the PLAATO trial current as of July 2010 was used for this analysis (n = 22). Mechanical occlusion using the PLAATO device was used in 22 patients (age 68 ± 5, CHADS(2) score = 3.03 ± 0.6). Warfarin and clopidogrel were stopped during follow-up in all but one patient due to development of pulmonary emboli. After an average follow-up of 58 ± 9 months, four out of 22 patients (16.7%) developed a new ischemic stroke/TIA, translating to an annualized embolic rate of 3.63%. There were no differences in the demographics (age, sex, and CHADS(2) score) among patients with and without stroke. Cardiac CT documented peri-device leak in three out of four patients with stroke and in seven out of nine (75% vs. 77%, p = 0.706) patients without stroke that agreed to have a follow-up cardiac CT (Chi squared with Yates correction for this interaction = 0.012, p = 0.912). TEE corroborated these results but failed to identify peri-device leak in three patients without stroke. CONCLUSIONS: The main finding of our analysis suggests that in long-term follow-up, residual flow after LAA occlusion with the PLAATO device, as documented by cardiac CT, is ubiquitous but is not associated with an increased risk of stroke.

Initial clinical experience with a novel visualization and virtual electrode radiofrequency ablation catheter to treat atrial flutter.

BACKGROUND: Linear ablation lesions are used to treat a variety of cardiac arrhythmias. However, successful long-term outcome is hampered by both the uncertainty of catheter-tissue contact for any individual lesion and the difficulty in ensuring point-to-point lesion contiguity. OBJECTIVE: A novel virtual electrode radiofrequency ablation catheter equipped with an endoscope to directly visualize the target tissue was used to ensure tissue contact and lesion contiguity along the cavotricuspid isthmus (CTI) to treat typical atrial flutter. METHODS: In this feasibility study of five patients with drug-resistant CTI-dependent atrial flutter, catheter ablation was performed using the visualization virtual electrode radiofrequency ablation catheter. After standard femoral access, the ablation catheter was advanced to the tricuspid annulus under fluoroscopic and intracardiac echocardiography guidance. In three of five patients, the ablation procedure was performed during atrial flutter; the other two ablations were during coronary sinus pacing. RESULTS: Conversion to sinus rhythm was noted after the delivery of 12 ± 7 lesions. Bidirectional CTI conduction block was successfully achieved in all patients. Initial, transient CTI block was first observed after delivering 19 ± 13 lesions; ultimately, 34 ± 18 lesions were required to achieve permanent bidirectional CTI block. The mean ablation and procedure times were 72 ± 42 and 151 ± 17 minutes. The mean fluoroscopy times for the ablation alone and the entire procedure were 13 ± 8 and 17 ± 7 minutes, respectively. CONCLUSIONS: This study introduces the clinical feasibility of a novel paradigm for contiguous linear ablation: virtual electrode ablation under direct endoscopic visualization.

Evaluation of catheter ablation of periatrial ganglionic plexi in patients with atrial fibrillation.

Recent data suggests that the cardiac autonomic nervous system has an important role in the initiation and maintenance of atrial fibrillation (AF). This study investigated (1) the feasibility of identifying and targeting these autonomic ganglia using endocardial radiofrequency stimulation and ablation, respectively; (2) the efficacy of endocardial ablation to completely eliminate the vagal response elicited from epicardial stimulation; and (3) the effect of autonomic ablation on the acute inducibility of AF. The study included 18 patients referred for catheter ablation of suspected vagal-mediated AF. The endocardial left atrial surface was stimulated at high frequency (20 to 50 Hz) to elicit a vagal response. In selected patients (n = 5), pericardial access was obtained using a subxyphoid puncture to permit epicardial stimulation. Catheter ablation of the putative autonomic ganglionic sites was performed from the left atrial endocardium using irrigated radiofrequency energy. After ablation of all identifiable autonomic ganglia, high-frequency pacing was repeated to induce AF. In all patients, stimulation at certain endocardial sites elicited a vagal response. Endocardial ablation abrogated this vagal responsiveness. Furthermore, for sites accessible from the pericardium, the vagal response elicited using epicardial stimulation was also eliminated. Despite successful ablation of these ganglia, AF was still inducible in 17 of 18 patients. In conclusion, successful ablation of autonomic ganglia from an endocardial approach can be reliably achieved using an irrigated catheter. In addition, ablation of these structures in patients with vagal-mediated AF is insufficient to prevent its acute reinduction with high-frequency atrial stimulation.

Balloon catheter ablation to treat paroxysmal atrial fibrillation: what is the level of pulmonary venous isolation?

BACKGROUND: Unlike the initial balloon ablation catheters that were designed to deliver ablation lesions within the pulmonary veins (PVs), the current balloon prototypes are fashioned to deliver lesions at the PV ostia. OBJECTIVE: Using electroanatomical mapping, this study evaluates the actual location of ablation lesions generated by cryo-based, laser-based, or ultrasound-based balloon catheters. METHODS: In a total of 14 patients with paroxysmal atrial fibrillation, PV isolation was performed using either a cryoballoon catheter (8 patients), laser catheter (4 patients) or ultrasound balloon catheter (2 patients). Patients underwent preprocedural computed tomographic/magnetic resonance imaging. An intracardiac ultrasound catheter was used to aid in positioning the balloon catheter at the PV ostium/antrum. In all patients, sinus rhythm bipolar voltage amplitude maps (using either CARTO with computed tomographic/magnetic resonance image integration or NavX mapping) were generated at baseline and after electrical PV isolation as confirmed by use of a circular mapping catheter. RESULTS: Electrical isolation was achieved in 100% of the PVs. Electroanatomical mapping revealed that after ablation with any of the 3 balloon catheters, the extent of isolation included the tubular portions of each PV to the level of the PV ostia. However, the PV antral portions were left largely unablated with all 3 balloon technologies. CONCLUSION: Using the current generation of balloon ablation catheters, electrical isolation occurs at the level of the PV ostia, but the antral regions are largely unablated.

Prophylactic catheter ablation for the prevention of defibrillator therapy.

BACKGROUND: For patients who have a ventricular tachyarrhythmic event, implantable cardioverter-defibrillators (ICDs) are a mainstay of therapy to prevent sudden death. However, ICD shocks are painful, can result in clinical depression, and do not offer complete protection against death from arrhythmia. We designed this randomized trial to examine whether prophylactic radiofrequency catheter ablation of arrhythmogenic ventricular tissue would reduce the incidence of ICD therapy. METHODS: Eligible patients with a history of a myocardial infarction underwent defibrillator implantation for spontaneous ventricular tachycardia or fibrillation. The patients did not receive antiarrhythmic drugs. Patients were randomly assigned to defibrillator implantation alone or defibrillator implantation with adjunctive catheter ablation (64 patients in each group). Ablation was performed with the use of a substrate-based approach in which the myocardial scar is mapped and ablated while the heart remains predominantly in sinus rhythm. The primary end point was survival free from any appropriate ICD therapy. RESULTS: The mortality rate 30 days after ablation was zero, and there were no significant changes in ventricular function or functional class during the mean (+/-SD) follow-up period of 22.5+/-5.5 months. Twenty-one patients assigned to defibrillator implantation alone (33%) and eight patients assigned to defibrillator implantation plus ablation (12%) received appropriate ICD therapy (antitachycardia pacing or shocks) (hazard ratio in the ablation group, 0.35; 95% confidence interval, 0.15 to 0.78, P=0.007). Among these patients, 20 in the control group (31%) and 6 in the ablation group (9%) received shocks (P=0.003). Mortality was not increased in the group assigned to ablation as compared with the control group (9% vs. 17%, P=0.29). CONCLUSIONS: In this randomized trial, prophylactic substrate-based catheter ablation reduced the incidence of ICD therapy in patients with a history of myocardial infarction who received ICDs for the secondary prevention of sudden death. (Current Controlled Trials number, ISRCTN62488166 [controlled-trials.com].).

Substrate-based catheter ablation of epicardial ventricular tachycardia related to an anomalous coronary artery.

Delayed enhancement magnetic resonance imaging is known for its ability to identify scarred myocardial tissue. This case report describes the use of MR imaging to define the location and transmural extent of infarcted tissue in a 45-year-old woman with an anomalous right coronary artery and hemodynamically unstable ventricular tachycardia. By demonstrating a predominantly epicardial infarct, MR imaging indicated that the pericardial approach was necessary for successful substrate-based ventricular tachycardia ablation.