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Epicardial and Endocardial Hybrid Ablation for Atrial Fibrillation

Key Points Isolated catheter ablation of persistent and long-standing persistent atrial fibrillation demonstrates marginal long-term outcomes. Technological improvements and minimally invasive techniques enable surgical ablation without sternotomy or cardiopulmonary bypass, but outcomes fall short of the cut-and-sew maze procedure. The Hybrid approach combines medical, catheter, and surgical therapies either simultaneously or in a staged fashion. At a minimum, the therapeutic objectives are electrical isolation of the…

Ablation of Persistent and Long-Standing Persistent Atrial Fibrillation

Key Points Ablation of persistent and long-standing persistent atrial fibrillation (AF) is a potentially complex procedure, which carries a lower success rate than ablation for paroxysmal AF. Pulmonary vein isolation remains the cornerstone of AF ablation in every AF population with antral isolation having better outcomes than ostial ablation. Further adjunctive ablation comes in many forms. Currently we favor posterior wall isolation, careful attention to low-voltage…

Ablation of Atrial Fibrillation Drivers: Focal Impulse and Rotor Modulation

Key Points Mapping Localized atrial fibrillation (AF) drivers commonly exist in spatially defined regions that may fluctuate over time but in the similar defined region. Similar AF drivers have been mapped in optical maps of human AF and by other clinical mapping methods. Localized AF sources are distinct from disorganized activation in AF. Recent metaanalyses show overall benefits of AF driver ablation. Ablation Targets Rotational AF…

Substrate-Based Ablation for Atrial Fibrillation

Key Points Atrial substrate modification is required for a successful outcome in a minority of patients with paroxysmal atrial fibrillation (AF) and in most patients with persistent AF. Substrate modification is considered when AF persists despite effective elimination of pulmonary vein (PV) arrhythmogenicity by extraostial PV isolation (PVI), antral PVI, or wide area circumferential ablation. Substrate modification strategies are linear ablation, ablation guided by complex fractionated…

Ablation of Nonpulmonary Vein Triggers

Key Points Nonpulmonary vein (non-PV) “triggers” can be identified in 10% to 33% of unselected patients with atrial fibrillation (AF). Compared with paroxysmal AF, the incidence of non-PV foci is higher in patients with persistent AF. Ablation of non-PV triggers is also important for patients with persistent AF and for those patients who undergo repeat ablation procedures in whom all PVs are found to be isolated.…

Pulmonary Vein Isolation by Cryoballoon Catheter

Key Points Mapping Pulmonary vein antral positioning of the cryoballoon with proximal-seal method Pulmonary vein potential recording for time-to-isolation with Achieve Mapping Catheter Postablation voltage map (optional) Ablation Targets Pulmonary vein antral modification and pulmonary vein isolation Special Equipment Cryoballoon ablation system: Flexcath Advance Cryoballoon Circular Achieve mapping catheter Optional intracardiac echocardiogram for transseptal Sources of Difficulty Common ostium will need segmental ablation for durable isolation…

Pulmonary Vein Isolation for Atrial Fibrillation

Key Points Pulmonary vein isolation (PVI) is the cornerstone of current ablation techniques for the treatment of atrial fibrillation (AF). Confirmation of electrical isolation with a circular mapping catheter is crucial to improve the short- and long-term outcomes of this procedure. Wide antral PVI improves the long-term arrhythmia-free survival compared with ostial PVI. PV reconnection is a major contributor to AF recurrences after PVI, especially in…

Ablation of Postoperative Atrial Tachycardia in Congenital Heart Disease

Key Points Intraatrial reentrant tachycardia (IART) is a prevalent long-term consequence of congenital heart disease. IART may manifest as typical atrial flutter, atypical macroreentrant atrial tachycardia, or atrial fibrillation. In addition to causing symptoms, IART appears to be associated with heart failure, thrombosis and thromboembolism, and reduced survival. Although prophylactic antiarrhythmic drugs and pacing strategies may be useful in selected patients, modification of the atrial substrate…

Ablation of Nonisthmus-Dependent Flutters and Atrial Macroreentry

Key Points Atypical or nonisthmus-dependent atrial flutter and atrial macroreentry requires fixed or functional barriers and regions of slow conduction. Atypical flutters are often recognized after catheter ablation or surgical treatment of atrial fibrillation (AF) or after surgery that involves right or left atriotomies. Activation mapping is used to demonstrate reentrant circuits, middiastolic potentials, fractionated potentials, and double potentials. A multipolar electrode catheter is useful to…

Ablation of Cavotricuspid Isthmus–Dependent Atrial Flutters

Key Points The mechanism of most cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL) is macroreentry around the tricuspid valve annulus (TVA). The diagnosis of CTI-dependent atrial flutter is made by demonstration of macroreentry around the TVA during entrainment at two or more sites around the tricuspid valve, and demonstration of concealed entrainment from the CTI during AFL. The target for ablation of CTI-dependent AFL is the CTI,…

Ablation of Focal Atrial Tachycardias

Key Points Anatomy Atrial tachycardia (AT) foci exhibit a characteristic anatomic distribution in both atria. The right atrium is the most common location with two-thirds of right sided focal AT arising from the crista terminalis. Pathophysiology Focal AT may be caused by microreentry, abnormal automaticity, or triggered activity. This mechanistic distinction is less relevant in the current era of radiofrequency ablation. Arrhythmia Diagnosis Focal AT must…

Intracardiac Echocardiography, Computed Cardiac Tomography, and Magnetic Resonance Imaging for Guiding Mapping and Ablation

Key Points Cardiac imaging plays an essential role in contemporary invasive electrophysiologic mapping and ablation procedures, from guiding appropriate patient selection; to preprocedure definition of the substrate; to intraprocedural demonstration of catheter movement, tissue contact, and lesion formation; to postprocedure evaluation for both procedural success and development of complications Imaging is often integrated into the workflow of mapping and ablation procedures Intracardiac echocardiography (ICE) is perfectly…

Remote Catheter Navigation Systems

Key Points Remote catheter navigation systems currently comprise electromagnetic and electromechanical technologies. Four remote systems are currently available. Each navigation system has both advantages and disadvantages with substantial variation in the cost, learning curve, and procedure applications. Potential advantages of remote navigation system are reduced operator radiation exposure and physical stress, improved catheter stability, enhanced patient safety, and automated mapping (in some instances) and catheter navigation.…

Catheter 3-Dimensional Mapping Systems

Key Points Several 3-dimensional mapping systems are currently available, including three systems in widespread clinical use. Location of mapping electrodes is identified by the mapping system using magnetic-based or impedance-based technology or a combination of these. These systems allow 3-dimensional reconstruction of cardiac chamber anatomy, with recording and display of electrogram data at each point on the chamber surface. Activation maps can display propagation of wave…

Fundamentals of Intracardiac Mapping

Key Points Intracardiac electrograms provide timing and morphologic information. Local tissue activation is best identified by the point of maximal downslope of unipolar electrograms and maximal amplitude of bipolar electrograms. Cardiac mapping techniques include activation mapping, pace mapping, entrainment mapping, and computerized mapping (sometimes called substrate mapping). Atrial and ventricular pacing maneuvers performed in sinus rhythm and during tachycardia can be used to differentiate and diagnose…

Cardiac Anatomy for Catheter Mapping and Ablation of Arrhythmias

Key Points Anatomic terminology presently used and pertinent for the interventional electrophysiology defers from classic anatomy descriptions. It is more important for electrophysiologists to be able to correlate the anatomic view in a consistent fashion with real-time imaging. Intracardiac ultrasound, along with fluoroscopy, is the primary real-time imaging modality used during mapping and ablation. Preoperative transthoracic echocardiography, 3-dimensional computed tomography, and magnetic resonance imaging with registration…

Catheter Cryoablation: Biophysics and Clinical Applications

Key Points The biophysics and mechanisms of cryothermal injury comprise the following general phases: freeze/thaw, hemorrhage and inflammation, replacement fibrosis, and apoptosis. Cryoablation lesion size is determined by refrigerant flow rate, electrode size, electrode pressure, electrode orientation, duration of energy delivery, and electrode temperature. Advantages of cryoablation include the ability to titrate temperature/duration to produce reversible lesions before permanent tissue destruction (cryomapping), decreased risk of thromboembolism,…

Irrigated and Cooled-Tip Radiofrequency Catheter Ablation

Key Points In animal experiments, cooled ablation overcomes the limitations of standard radiofrequency (RF) delivery by cooling the catheter tip and preventing an impedance rise, thus allowing higher power delivery and resulting in deeper and larger lesions. In the clinical setting, efficacy of cooled-tip RF ablation is comparable to or better than conventional RF ablation for the catheter-based treatment of recurrent atrioventricular reentrant arrhythmias, reentrant atrial…

Guiding Lesion Formation During Radiofrequency Catheter Ablation

Key Points Radiofrequency (RF) energy is the most commonly used energy source in cardiac catheter ablation procedures. The goal of RF power titration is to maximize the safety and efficacy of energy application. Stable catheter-tissue contact is inadequately assessed by fluoroscopy, tactile feedback, and electrogram characteristics. Contact force sensing catheters may improve the safety and efficacy of catheter ablation procedures. Careful titration of energy delivery can…

Biophysics and Pathophysiology of Radiofrequency Lesion Formation

Key Points Radiofrequency (RF) energy induces thermal lesion formation through resistive heating of myocardial tissue. Tissue temperatures of 50°C or higher are necessary for irreversible injury. Under controlled conditions, RF lesion size increases with increasing delivered power, electrode–tissue interface temperature, electrode diameter, and contact force. Power density declines with the square of distance from the source, and tissue temperature declines inversely with distance from the heat…