Endocardial Ablation to Eliminate Epicardial Arrhythmia Substrate in Scar-Related Ventricular Tachycardia

OBJECTIVES We evaluated the feasibility and safety of epicardial substrate elimination using endocardial radiofrequency (RF) delivery in patients with scar-related ventricular tachycardia (VT). BACKGROUND Epicardial RF delivery is limited by fat or associated with bleeding, extra-cardiac damages, coronary vessels and phrenic nerve injury. Alternative ablation approaches may be desirable. METHODS Forty-six patients (18 ischemic cardiomyopathy [ICM], 13 non-ischemic dilated cardiomyopathy [NICM], 15 arrhythmogenic right ventricular cardiomyopathy [ARVC]) with sustained VT underwent combined endo- and epicardial mapping. All patients received endocardial ablation targeting local abnormal ventricular activities in the endocardium (Endo-LAVA) and epicardium (Epi-LAVA), followed by epicardial ablation if needed. RESULTS From a total of 173 endocardial ablations targeting Epi-LAVA at the facing site, 48 (28%) applications (ICM: 20/71 [28%], NICM: 3/39 [8%], ARVC: 25/63 [40%]) successfully eliminated the Epi-LAVA. Presence of Endo-LAVA, most delayed and low bipolar amplitude of Epi-LAVA, low unipolar amplitude in the facing endocardium, and Epi-LAVA within a wall thinning area at CT scan were associated with successful ablation. Endocardial ablation could abolish all Epi-LAVA in 4 ICM and 2 ARVC patients, whereas all patients with NICM required epicardial ablation. Endocardial ablation was able to eliminate Epi-LAVA at least partially in 15 (83%) ICM, 2 (13%) NICM, and 11 (73%) ARVC patients, contributing to a potential reduction in epicardial RF applications. Pericardial bleeding occurred in 4 patients with epicardial ablation. CONCLUSIONS Elimination of Epi-LAVA using endocardial RF delivery is feasible and may be used first to reduce the risk of epicardial ablation.

Radiofrequency catheter ablation of idiopathic ventricular tachycardia originating in the main stem of the pulmonary artery.

We report the case of a patient in whom successful radiofrequency catheter ablation of an idiopathic ventricular tachycardia (VT) originating in the main stem of the pulmonary artery was performed. After successful ablation of the index arrhythmia, which was an idiopathic right ventricular outflow tract VT, a second VT with a different QRS morphology was reproducibly induced. Mapping of the second VT revealed the presence of myocardium approximately 2 cm above the pulmonary valve. Application of radiofrequency energy at this site resulted in termination and noninducibility of this VT. After 6-month follow-up, the patient remained free from VT recurrences.

Frequent ventricular tachycardias: antiarrhythmic drug treatment or catheter ablation?

Antiarrhythmic drugs are used in at least 50% of patients who received an implantable cardioverter defibrillator (ICD). The potential indications for antiarrhythmic drug treatments in patients with an ICD are generally the following: reduction of the number of ventricular tachycardias (VTs) or episodes of ventricular fibrillation and therefore reduction of the number of ICD therapies, most importantly, the number of disabling ICD shocks. Accordingly, the quality of life should be improved and the battery life of the ICD extended. Moreover, antiarrhythmic drugs have the potential to increase the tachycardia cycle length to allow termination of VTs by antitachycardia pacing and reduction of the number of syncopes. In addition, supraventricular arrhythmias can be prevented or their rate controlled. Recently published or reported trials have shown the efficacy of amiodarone, sotalol and azimilide to significantly reduce the number of appropriate and inappropriate ICD shocks in patients with structural heart disease. However, the use of antiarrhythmic drugs may also have adverse effects: an increase in the defibrillation threshold, an excessive increase in the VT cycle length leading to detection failure. In this situation and when antiarrhythmic drugs are ineffective or have to be stopped because of serious side effects, catheter ablation of both monomorphic stable and pleomorphic and/or unstable VTs using modern electroanatomic mapping systems should be considered. The choice of antiarrhythmic drug treatment and the need for catheter ablation in ICD patients with frequent VTs should be individually tailored to specific clinical and electrophysiological features including the frequency, the rate, and the clinical presentation of the ventricular arrhythmia. Although VT mapping and ablation is becoming increasingly practical and efficacious, ablation of VT is mostly done as an adjunctive therapy in patients with structural heart disease and ICD experiencing multiple shocks, because the recurrence and especially the occurrence of "new" VTs after primarily successful ablation with time and disease progression have precluded a widespread use of catheter ablation as primary treatment.

Electroanatomic mapping of the endocardium. Implication for catheter ablation of ventricular tachycardia.

The electroanatomic mapping system Carto((R)) with its combination of anatomic and electrophysiologic information has substantially improved our understanding of arrhythmia mechanisms and substrates in patients with ventricular tachycardia (VT) and structural heart disease. Identification of the individual arrhythmogenic substrate and successful ablation guided by the combination of sinus rhythm voltage mapping and conventional electrophysiologic techniques like pace and activation/entrainment mapping are best described for patients with recurrent VT in remote myocardial infarction. In about 75-90% of the patients, the target VT can be ablated with acute success and the patients remain free of any VT recurrence in up to 75%. First results of electroanatomically guided ablation in patients with arrhythmogenic right ventricular dysplasia are promising. Data on ablation of VT in other structural heart diseases are very limited, since the arrhythmogenic substrate is very diffuse, e. g., in dilated cardiomyopathy, or there are only small patient numbers, e. g., for cardiac sarcoidosis or monomorphic VT after repair of congenital heart disease. In this article, the current status of electroanatomically guided endocardial mapping and ablation of VT in patients with structural heart disease is described.

Idiopathic ventricular outflow tract arrhythmias from the great cardiac vein: Challenges and risks of catheter ablation

INTRODUCTION Catheter ablation for idiopathic ventricular arrhythmia is well established but epicardial origin, proximity to coronary arteries, and limited accessibility may complicate ablation from the venous system in particular from the great cardiac vein (GCV). METHODS Between April 2009 and October 2010 14 patients (56 ± 15 years; 9 male) out of a total group of 117 patients with idiopathic outflow tract tachycardias were included undergoing ablation for idiopathic VT or premature ventricular contractions (PVC) originating from GCV. All patients in whom the PVC arose from the GCV were subject to the study. In these patients angiography of the left coronary system was performed with the ablation catheter at the site of earliest activation. RESULTS Successful ablation was performed in 6/14 (43%) and long-term success was achieved in 5/14 (36%) patients. In 4/14 patients (28.6%) ablation was not performed. In another 4 patients (26.7%), ablation did not abolish the PVC/VT. In the majority, the anatomical proximity to the left coronary system prohibited effective RF application. In 3 patients RF application resulted in a coronary spasm with complete regression as revealed in repeat coronary angiography. CONCLUSION A relevant proportion idiopathic VT/PVC can safely be ablated from the GCV without significant permanent coronary artery stenosis after RF application. Our data furthermore demonstrate that damage to the coronary artery system is likely to be transient.

Role of alternative interventional procedures when endo- and epicardial catheter ablation attempts for ventricular arrhythmias fail.

BACKGROUND Ventricular tachycardia (VT) refractory to antiarrhythmic drugs and standard percutaneous catheter ablation techniques portends a poor prognosis. We characterized the reasons for ablation failure and describe alternative interventional procedures in this high-risk group. METHODS AND RESULTS Sixty-seven patients with VT refractory to 4±2 antiarrhythmic drugs and 2±1 previous endocardial/epicardial catheter ablation attempts underwent transcoronary ethanol ablation, surgical epicardial window (Epi-window), or surgical cryoablation (OR-Cryo; age, 62±11 years; VT storm in 52%). Failure of endo/epicardial ablation attempts was because of VT of intramural origin (35 patients), nonendocardial origin with prohibitive epicardial access because of pericardial adhesions (16), and anatomic barriers to ablation (8). In 8 patients, VT was of nonendocardial origin with a coexisting condition also requiring cardiac surgery. Transcoronary ethanol ablation alone was attempted in 37 patients, OR-Cryo alone in 21 patients, and a combination of transcoronary ethanol ablation and OR-Cryo (5 patients), or transcoronary ethanol ablation and Epi-window (4 patients), in the remainder. Overall, alternative interventional procedures abolished ≥1 inducible VT and terminated storm in 69% and 74% of patients, respectively, although 25% of patients had at least 1 complication. By 6 months post procedures, there was a significant reduction in defibrillator shocks (from a median of 8 per month to 1; P<0.001) and antiarrhythmic drug requirement although 55% of patients had at least 1 VT recurrence, and mortality was 17%. CONCLUSIONS A collaborative strategy of alternative interventional procedures offers the possibility of achieving arrhythmia control in high-risk patients with VT that is otherwise uncontrollable with antiarrhythmic drugs and standard percutaneous catheter ablation techniques.

Better outcome of ablation for sustained outflow-tract ventricular tachycardia when tachycardia is inducible.

AIMS In patients presenting with spontaneous sustained ventricular tachycardia (VT) from the outflow-tract region without overt structural heart disease ablation may target premature ventricular contractions (PVCs) when VT is not inducible. We aimed to determine whether inducibility of VT affects ablation outcome. METHODS AND RESULTS Data from 54 patients (31 men; age, 52 ± 13 years) without overt structural heart disease who underwent catheter ablation for symptomatic sustained VT originating from the right- or left-ventricular outflow region, including the great vessels. A single morphology of sustained VT was inducible in 18 (33%, SM group) patients, and 11 (20%) had multiple VT morphologies (MM group). VT was not inducible in 25 (46%) patients (VTni group). After ablation, VT was inducible in none of the SM group and in two (17%) patients in the MM group. In the VTni group, ablation targeted PVCs and 12 (48%) patients had some remaining PVCs after ablation. During follow-up (21 ± 19 months), VT recurred in 46% of VTni group, 40% of MM inducible group, and 6% of the SM inducible group (P = 0.004). Analysis of PVC morphology in the VTi group further supported the limitations of targeting PVCs in this population. CONCLUSION Absence of inducible VT and multiple VT morphologies are not uncommon in patients with documented sustained outflow-tract VT without overt structural heart disease. Inducible VT is associated with better outcomes, suggesting that attempts to induce VT to guide ablation are important in this population.

Application Of Laser Microdissection Icp-ms For High Resolution Elemental Mapping In Mouse Brain Tissue: A Comparative Study With Laser Ablation Icp-ms.

Mapping of elements in biological tissue by laser induced mass spectrometry is a fast growing analytical methodology in life sciences. This method provides a multitude of useful information of metal, nonmetal, metalloid and isotopic distribution at major, minor and trace concentration ranges, usually with a lateral resolution of 12-160 µm. Selected applications in medical research require an improved lateral resolution of laser induced mass spectrometric technique at the low micrometre scale and below. The present work demonstrates the applicability of a recently developed analytical methodology - laser microdissection associated to inductively coupled plasma mass spectrometry (LMD ICP-MS) - to obtain elemental images of different solid biological samples at high lateral resolution. LMD ICP-MS images of mouse brain tissue samples stained with uranium and native are shown, and a direct comparison of LMD and laser ablation (LA) ICP-MS imaging methodologies, in terms of elemental quantification, is performed.

Determination of the Most Efficient Temperature for Radiofrequency Ablation of Renal Cells: A Prospective Study in Dogs

Background and Purpose: Radiofrequency (RF) ablation of renal tumors is a major technique for tumor cell destruction while preserving healthy renal parenchyma. There is no consensus in the literature regarding the optimal temperature, impedance, and time for RF application for effective cell destruction. This study investigated two variables while keeping time unchanged: Temperature for RF cell destruction and tissue impedance in dog kidneys. Materials and Methods: Sixteen dogs had renal punctures through videolaparoscopy for RF interstitial tissue ablation. A RF generator was applied for 10 minutes to the dog's kidney at different target temperatures: 80 degrees C, 90 degrees C, and 100 degrees C. On postoperative day14, the animals were sacrificed and nephrectomized. All lesions were macroscopically and microscopically examined. The bioelectrical impedance was evaluated at three different temperatures. Results: Renal injuries were wider and deeper at 90 degrees C (P < 0.001), and they were similar at 80 degrees C and 100 degrees C. The bioelectrical impedance was lower at 90 degrees C than at the temperatures of 80 degrees C and 100 degrees C (P < 0.001). Viable cells in the RF ablation tissue area were not found in the microscopic examination. Conclusion: The most effective cell destruction in terms of width and depth was achieved at 90 degrees C, which was also the optimal temperature for tissue impedance. RF ablation of renal cells eliminated all viable cells.

Ablation Rate and Morphology of Superficial and Deep Dentin Irradiated with Different Er:YAG Laser Energy Levels

Objective: In this study we evaluated the ablation rate of superficial and deep dentin irradiated with different Er:YAG laser energy levels, and observed the micromorphological aspects of the lased substrates with a scanning electron microscope (SEM). Background Data: Little is known about the effect of Er: YAG laser irradiation on different dentin depths. Materials and Methods: Sixty molar crowns were bisected, providing 120 specimens, which were randomly assigned into two groups ( superficial or deep dentin), and later into five subgroups (160, 200, 260, 300, or 360 mJ). Initial masses of the specimens were obtained. After laser irradiation, the final masses were obtained and mass losses were calculated followed by the preparation of specimens for SEM examination. Mass-loss values were subjected to two-way ANOVA and Fisher's least significant difference multiple-comparison tests (p < 0.05). Results: There was no difference between superficial and deep dentin. A significant and gradual increase in the mass-loss values was reached when energies were raised, regardless of the dentin depth. The energy level of 360 mJ showed the highest values and was statistically significantly different from the other energy levels. The SEM images showed that deep dentin was more selectively ablated, especially intertubular dentin, promoting tubule protrusion. At 360 mJ the micromorphological features were similar for both dentin depths. Conclusion: The ablation rate did not depend on the depth of the dentin, and an energy level lower than 360 mJ is recommended to ablate both superficial and deep dentin effectively without causing tissue damage.

Effect of Er:YAG Laser Parameters on Ablation Capacity and Morphology of Primary Enamel

Objective: The purpose of this study was to evaluate the ablation capacity of different energies and pulse repetition rates of Er:YAG laser energy on primary molar enamel, by assessing mass loss and by analyzing the surface morphology with scanning electron microscopy. Background Data: Previous studies have demonstrated the capacity of the Er:YAG laser to ablate enamel substrate. Methods: Forty-two sound primary molars were bisected in a mesiodistal direction. The enamel surfaces were flattened and their initial mass (in milligrams) was obtained. An area of 4 mm(2) was delimited. The specimens were randomly assigned to 12 groups according to the combination of energy (160, 200, 250, and 300 mJ) and pulse repetition rate (2, 3, and 4 Hz). Er: YAG laser irradiation was performed on each specimen for 20 sec. After irradiation, the final mass was obtained and specimens were prepared for examination with scanning electron microscopy. The data obtained by subtracting the final mass from the initial mass were statistically analyzed using ANOVA and the Tukey test (p < 0.05). Results: The pulse repetition rate of 4 Hz provided greater mass loss, different from that seen with 2 Hz, and similar to that seen with 3 Hz. The energy level of 300 mJ resulted in greater mass loss, similar to that seen with 200 and 250 mJ. Scanning electron photomicrographs showed that there was non-selective enamel removal, with fused and cracked areas in all specimens. Conclusion: The parameters of 200 mJ and 2 Hz produced a good ablation rate with fewer surface alterations in primary molar enamel.

Early Brief Treatment with Losartan plus Mycophenolate Mofetil Provides Lasting Renoprotection in a Renal Ablation Model

Background: Inflammatory events antecede established renal injury in rats with 5/6 renal ablation (Nx), as indicated by the beneficial effects of early, uninterrupted treatment with mycophenolate mofetil (MMF). Angiotensin II also exerts a major pathogenic role at this initial phase. We investigated whether losartan (L) or L+MMF treatment, started early, and L+MMF treatment, started late, would exert lasting renoprotection in Nx even after being discontinued. Methods: Adult male Munich-Wistar rats underwent Nx and were divided into three groups: Nx (untreated), Nx(L) (given L), and Nx(LMMF) (given L and MMF). Protocol 1: treatments began on day 1, and ceased on day 30, after Nx. Protocol 2: L+MMF treatment began on day 30 and ceased on day 60. Results: Protocol 1: on day 30, hypertension, albuminuria and renal injury were strongly attenuated in Groups Nx(L) and Nx(LMMF). On day 120, these abnormalities were still attenuated in group Nx(LMMF). Protocol 2: on day 120, all parameters were similar between this late Nx(LMMF) group and untreated Nx. Conclusion: In Nx, temporary suppression of early, transitory hemodynamic/inflammatory phenomena affords relatively durable renoprotection even after treatment discontinuation. This effect is not obtained with similar temporary treatment initiated later in the course of renal disease. Copyright (C) 2010 S. Karger AG, Basel

Left Atrial Function After Ablation for Paroxysmal Atrial Fibrillation

Radiofirequency ablation of the pulmonary veins has been used to treat patients with paroxysmal atrial fibrillation (AF), and atrial damage after ablation is an issue of concern. To evaluate left atrial function shortly and midterm after ablation, 33 consecutive patients with paroxysmal AF were studied at baseline, 24 hours, and >= 6 months after ablation. Patients in sinus rhythm with normal ventricular function were included in the study. Echocardiographic measurements of left atrial volumes (Simpson`s rule) and transmitral and tissue Doppler myocardial (A`) velocities at the septal and lateral mitral annulus were undertaken at each time. Left atrial emptying fraction (EF; maximal - minimal left atrial volume/maximal left atrial volume) was used to express left atrial function. After 8 +/- 2 months, 30 of 33 patients returned (23 men, age 53 +/- 13 years), and all except 2 were in sinus rhythm. Shortly after ablation, left atrial minimal volumes increased (from 30 +/- 15 to 35 +/- 15 ml; p = 0.02), with maximal volumes unchanged, resulting in decreased left atrial EF (from 47 +/- 8 to 40 +/- 7 ml; p <0.05). Tissue Doppler septal A` velocities also decreased (from 8.2 +/- 1.8 to 6.9 +/- 2.0 cm/s; p <0.05). However, after midterm follow-up, both left atrial EF and septal A` velocities had slightly increased compared with shortly after ablation, although left atrial volumes remained similar to baseline. Septal A` velocity changes paralleled left atrial EF both shortly (r = 0.46, p = 0.02) and at midterm after ablation (r = 0.47, p = 0.01). In conclusion, after radiofrequency ablation, patients with paroxysmal AF experienced an initial impairment in atrial function, with improvement at longer term follow-up. (C) 2009 Elsevier Inc. All rights reserved. (Am J Cardiol 2009;103: 395-398)

Gastric hypomotility following epicardial vagal denervation ablation to treat atrial fibrillation

Gastric Palsy Following AF Vagal Ablation. We report a case of a 55-year-old man with vagal paroxysmal atrial fibrillation (AF) who was submitted to selective epicardial and endocardial atrial vagal denervation with the objective of treating AF. Radiofrequency pulses were applied on epicardial and endocardial surface of the left atrium close to right pulmonary veins (PVs) and also on epicardial surface close to left inferior PV. Following the procedure, patient presented with symptoms of gastroparesis, which was documented on CT scan and gastric emptying scintigraphy. Symptoms were transient and the patient recovered completely.