Catheter Ablation Technology Research Articles

Letter by Haines Regarding Article, “Direct Measurement of the Lethal Isotherm for Radiofrequency Ablation of Myocardial Tissue”

To the Editor: Myocardial injury with hyperthermic catheter ablation technologies (radiofrequency electric current, microwave radiation, laser irradiation, or ultrasound) is both time and temperature dependent. The isotherm of irreversible injury is defined as the temperature at the border zone transition between viable and nonviable tissue. Ultimately, there is necrosis of that tissue and replacement by collagen scar, rendering that area electrically silent. Previous investigations have calculated the lesion isotherm …

Pharmacotherapy of Atrial Fibrillation: A Pathophysiological Perspective and Review

Atrial fibrillation (AF) is one of the most common arrhythmia encountered in clinical practice. Although AF is due to the structural and electrophysiological alterations in the atria, its sustainability is multifactorial, and the actual mechanisms are still not clear. Despite the recent advances in catheter ablation technology and techniques, pharmacotherapy still remains the first-line therapy for the management of AF. Current pharmacotherapy targets ion channel alterations that in fact represent only one aspect of the management of this complex arrhythmia. Successful pharmacological treatment of AF and restoration of sinus rhythm is limited and is in part due to its potential deleterious side effects. Newer agents having diverse mechanisms acting on the recently uncovered pathophysiological processes are on the horizon. These include atrial repolarization delaying agents, newer class III agents, Na(+)-Ca(2+) channel blockers, stretch receptor blockers, I(KACH) blockers, gap junction modifiers, upstream therapies, and agents targeting ischemia-induced AF. Gene- and cell-specific therapies including 'tailored nanopharmacy,' newer rate control medications with minimal side effects and the emergence of novel drugs targeting multiple areas of AF arrhythmogenesis in tandem with electrical therapy may be the future direction in the management of AF.

Atrial flutter: a focus on treatment options for a common supraventricular tachyarrhythmia

Atrial flutter (AFl), a re-entrant atrial tachycardia, is a cardiac rhythm disturbance that arises in the upper chambers of the heart. This usually non-life-threatening condition can be treated by a number of medical intervention strategies, which include electrical cardioversion, pharmacological therapy, and catheter ablation. These options have been available in clinical practice for a number of years. However, catheter ablation, in the form of radiofrequency catheter ablation and cryo catheter ablation, is increasingly utilised as a first-line treatment option for AFl in certain patients. The purpose of this review article is two-fold: first, to briefly present an overview of AFl and the more familiar treatment options for this arrhythmia, and second to provide more in-depth coverage of catheter ablation technologies as a treatment option for patients with AFl. As part of the latter objective, recent clinical studies documenting the use of radiofrequency catheter ablation and cryo catheter ablation for AFl are presented and their results briefly discussed.

Percutaneous catheter ablation of atrial fibrillation

Atrial fibrillation is the most common arrhythmia and is associated with important morbidity and mortality. Antiarrhythmic therapy is recommended as initial therapy but is associated with modest efficacy and significant side effects. Over the past several years, catheter ablation has been demonstrated to provide effective and safe curative therapy for atrial fibrillation. Future investigations will assess advances in catheter ablation technology and will help to define the precise role of catheter ablation relative to alternative therapies, such as rate-control and antiarrhythmic therapy.

Images in cardiovascular medicine. Early appearance of an edematous tissue reaction during left atrial linear ablation using intracardiac echo imaging.

Left atrial linear ablation is difficult and sometimes impossible to achieve using currently available catheter ablation technology. Left isthmus ablation (between the lateral mitral annulus and left inferior pulmonary vein) is a promising strategy for achieving “substrate modification” as, analogous to the right (cavotricuspid) isthmus, the creation of a relatively short lesion results in electrical transection of the left atrium as demonstrated by differential pacing …

Use of different catheter ablation technologies for treatment of typical atrial flutter: acute results and long-term follow-up.

We report the acute success and long-term follow-up in consecutive patients undergoing catheter ablation of typical right atrial flutter (AFL) using different ablation technologies. One hundred and two patients presenting for treatment of AFL to our laboratory were included in the study. Based on availability and physician preference, ablation was performed with either a cooled-tip catheter (39 patients, group I), an 8- or 10-mm tip catheter connected to a high-power radiofrequency (RF) generator (25 patients, group II), or a 4- or 5-mm tip catheter (38 patients, group III). Acute ablation success was achieved in all group II and group III patients. Among the 38 patients undergoing ablation with the conventional catheter tip (group I), crossover to an 8-mm tip or a cooled tip ablation catheter was required in 11 patients (29%). The mean fluoroscopy time was significantly higher in group I (54.3 +/- 26.4 minutes) when compared to group II (39.6 +/- 19.6 minutes; P < 0.05) and group III (40 +/- 16 minutes; P = 0.0.5). After a mean follow up of 20 +/- 5 months no patient in group II experienced recurrence of AFL, whereas 18.4% (7 of 38 patients; P < 0.05) in group I and 10% (4 of 39 patients; P < 0.05) in group III had recurrence of AFL. Ablation technologies designed to obtain larger size lesions appeared to be more effective in achieving acute ablation success of AFL and in limiting the long-term recurrence rate of this arrhythmia.

Circular mapping and ablation of thepulmonary vein for treatment of atrial fibrillation: Impact of different catheter technologies

ObjectivesWe conducted this study to compare the efficacy and safety of different catheter ablation technologies and of distal versus ostial pulmonary veins (PV) isolation using the circular mapping technique. BackgroundElectrical isolation of the PVs in patients with atrial fibrillation (AF) remains a technical challenge. MethodsTwo hundred eleven patients (163 men; mean age 53 ± 11 years) with symptomatic AF were included in this study. In the first 21 patients (group 1), distal isolation (≥5 mm from the ostium) was achieved targeting veins triggering AF. In the remaining 190 patients (group 2), ostial isolation of all PVs was performed using 4-mm tip (47 patients), 8-mm tip (21 patients), or cooled-tip (122 patients) ablation catheters. ResultsDistal isolation was able to eliminate premature atrial contractions (PACs) and AF in six of 21 patients (29%) and 10 of 34 PVs. After a mean follow-up time of 6 ± 4 months, no patients treated with the 8-mm tip catheter experienced recurrence of AF, whereas 21% (10 of 47 patients) and 15% (18 of 122 patients) of the patients ablated with the 4-mm tip and the cooled-tip ablation catheters experienced recurrence of AF after a mean follow-up of 10 ± 3 and 4 ± 2 months, respectively. Significant complications including stroke, tamponade, and severe stenosis occurred in 3.5% (8/211) of patients. ConclusionsCatheter technologies designed to achieve better lesion size appeared to have a positive impact on procedure time, fluoroscopy time, number of lesions, and overall efficacy. Although distal isolation can be achieved with fewer lesions, ostial isolation is required in the majority of patients to eliminate arrhythmogenic PACs and AF.

Mapping for ventricular tachycardia.

Mapping strategies for ventricular tachycardia (VT) have evolved significantly in the past 2 decades. This review discusses mapping techniques that can help in successful VT ablation. The electrocardiogram (ECG) remains a vital component of VT mapping and can help to identify the chamber of origin of VT. The ECG morphology of VT, however, is influenced by orientation of heart and location of the scar. Activation mapping during VT is an important technique that can help in further localization. Care has to be exercised to ensure that small signals are not ignored and far-field signals are recognized. Pace-mapping to mimic the VT is another way to map exit site for scar based reentrant VT or the site of origin of triggered and automatic VT in the absence of structural heart disease. For the latter group, this technique is widely used in determining the site of ablation. It is important to ensure a complete ECG match (12 out of 12 leads) of the pace-map to the clinical arrhythmia in these patients. In patients with structural heart disease, entrainment mapping remains the gold standard for defining the protected isthmus and other components of the VT circuit. Using this technique, successful ablation of reentrant VT can be achieved in 60-90% of patients. In order to perform entrainment mapping, the VT has to be hemodynamically tolerated; this is not the case in 25% of pts with scar based reentrant VT. The development of 3-dimensional mapping systems allows for more anatomically based linear ablation in patients with poorly tolerated uniform VT. Despite these advances, there are still about 10-20% VTs that cannot be ablated successfully with the above described techniques, especially in patients with structural heart disease. Other recent advances such as percutaneous closed chest epicardial mapping technique and cooled tip ablation catheter technology have the potential to enhance mapping and successful ablation of VT.

Use of different catheter ablation technologies for typical atrial flutter: Acute results and follow-up Robert Schweikert, Andrea Natale, Mina K. Chung, Patrick Tchou, Walid Saliba, Lon Castle, Logan Kanagaratnam, Mark Niebauer, Stephen Pavia, Cathy Lam, Alejandro Perez-Lugones. Cleveland Clinic Foundation, Cleveland

Use of different catheter ablation technologies for typical atrial flutter: Acute results and follow-up Robert Schweikert, Andrea Natale, Mina K. Chung, Patrick Tchou, Walid Saliba, Lon Castle, Logan Kanagaratnam, Mark Niebauer, Stephen Pavia, Cathy Lam, Alejandro Perez-Lugones. Cleveland Clinic Foundation, Cleveland

A new system for catheter ablation of atrial fibrillation

Increased attention is now being focused on developing new technologies to cure atrial fibrillation using catheter ablation techniques. The performance of a MAZE-type procedure using standard catheter ablation technologies is arduous and is associated with an unacceptable risk of complications. The Guidant Heart Rhythm Technologies Linear Ablation System was developed to create long transmural linear lesions. Unique features of this system include the availability of different preshaped multi-electrode steerable ablation catheters, the use of phased radiofrequency (RF) energy, and the control of RF output by varying the duty cycle. A prospective multicenter clinical trial to evaluate the safety and efficacy of a right atrial ablation procedure using this technology to treat atrial fibrillation is currently underway. To date, 15 patients have been enrolled and the procedure was acutely effective in 14 of 15 patients with no complications. Atrial fibrillation has recurred during short-term follow-up in 12 of 15 patients, a not surprising result, because this initial phase of testing involved only right-sided ablation. The early results of the phase I clinical trial confirm the findings of others that successful ablation of chronic atrial fibrillation is likely to require a left atrial approach. This clinical trial, as well as others that are currently underway, will be invaluable in the continuing development of catheter ablation of atrial fibrillation and, ultimately, in determining if the routine use of this therapeutic tool can become a reality.

Introduction: Changing Trends in Antiarrhythmic Therapy: Worldwide Experience With Class III Agents

T approaches to cardiac arrhythmias continue to change rapidly, as indicated by the recent acceptance of a number of revolutionary concepts. These include (1) the recognition that time-honored antiarrhythmic drugs that act essentially by slowing cardiac conduction (class I agents) may increase mortality despite suppressing cardiac arrhythmias. The result has been a shift to agents that act largely by prolonging cardiac repolarization (class III agents); (2) the realization that radiofrequency catheter ablation may produce permanent cures in many forms of arrhythmia, especially those of supraventricular origin; and (3) the introduction and refinement of the implantable cardioverter-defibrillator (ICD), which has the potential for prolonging survival by terminating ventricular tachycardia and fibrillation (VT/VF). The changing trends in the use of pharmacologic agents and advances in catheter ablation and ICD technology are profoundly impacting how physicians are deciding to terminate and/or prevent specific types of arrhythmia, not only to reduce or eliminate symptoms but also to prolong survival by reducing the probability of arrhythmic death. It has, however, become increasingly clear that survival in patients with arrhythmias cannot always be measured accurately by quantifying presumed arrhythmic deaths. The outcome that best indicates improved survival on antiarrhythmic therapy is the decrease in all-cause or total mortality, now the decisive endpoint of all mortality trials, whether they involve ICDs or antiarrhythmic drugs. For the most part, progress in antiarrhythmic drug therapy has been driven by data generated by randomized, controlled From the Division of Cardiology and the Department of Medicine, Veterans Affairs Medical Center of West Los Angeles, and the Department of Medicine, University of California, Los Angeles School of Medicine, Los Angeles, California. Address for reprints: Bramah N. Singh, MD, PhD, Division of Cardiology (111E), Veterans Affairs Medical Center of West Los Angeles, 11301 Wilshire Boulevard, Los Angeles, California 90073.

The anatomical determinants for the design of intracardiac mapping and ablation catheters.

An important factor in the efficient and successful completion of the ablation procedure is the design characteristics of the mapping/ablation catheters. These procedures are often hampered by the inability to maneuver the catheter to the desired location, in part because the catheters only have a single plane deflection capability and are not designed for the specific cardiac anatomical structures that contain the arrhythmogenic substrate. Single and Biplane Deflectable Catheters: Using measurements taken from six normal human cadaver hearts, ablation catheter design characteristics are presented for posterior, posterior septal, lateral, and posterior lateral pathways for retrograde and transseptal approaches. Three catheter designs based on anatomical characteristics were also evaluated. Pigtail Catheter: This catheter adapts to the atrial side of the mitral ring and improves positioning and stability for mapping and ablation of left-sided accessory pathways. Loop Catheter: This catheter is positioned at the perivalvular tricuspid ring and provides simultaneous mapping and ablation capabilities without the need to move the catheter or the need for additional catheters. Rotating Tip Catheter: The tip of this catheter is made up of three elongated teeth, which were curved 120 degrees apart into the rotating tip electrode. This electrode was designed to negotiate the surfaces of the atrial and intraventricular chambers. It is capable of discrete movements and has a large electrode-tissue contact area for the ablation of atrial and ventricular arrhythmias. Catheter designs presented in this article are based on the ability of the catheter to adapt to the anatomical location of the arrhythmogenic tissue as well as the maneuverability of the catheter's mapping and ablation electrodes. An anatomical approach to the design of ablation catheter technology is likely to reduce the x-ray radiation exposure for patient and operator, and may further increase the success rate of the procedure.