Performing transcatheter left atrial appendage closure: Techniques and challengesThe left atrial appendage (LAA) has been demonstrated to be the major source of thromboemboli in patients with atrial fibrillation.1 The rationale of LAA closure is based on eliminating LAA continuity with the left atrium (LA), thereby reducing stroke risk. Indeed, left atrial appendage occlusion (LAAO) procedures play an important role in anticoagulation-intolerant patients who are at risk for atrial fibrillation–related stroke. Based on the PROTECT AF (Watchman Left Atrial Appendage System for Embolic PROTECTion in Patients With Atrial Fibrillation)2 and PREVAIL (Prospective Randomized Evaluation of the WATCHMAN LAA Closure Device in Patients With Atrial Fibrillation [AF] Versus Long Term Warfarin Therapy)3 studies, the Food and Drug Administration (FDA) approved use of the Watchman (Boston Scientific, Marlborough, MA) device in 2015, with an updated generation of device subsequently ratified in 2020 following the PINNACLE-FLX (Protection Against Embolism for Nonvalvular AF Patients: Investigational Device Evaluation of the Watchman FLX LAA Closure Technology) study.
How to perform an epicardial ventricular tachycardia ablation: A contemporary and practical approachCatheter ablation is increasingly used for the treatment of cardiac arrhythmias. In the 1990s, in order to treat ventricular arrhythmias resulting from chagasic cardiomyopathy, Sosa et al1 developed a technique to enter the pericardium percutaneously in the absence of a pericardial effusion. Since then, “dry” epicardial access has become a regular part of complex catheter ablation. In this review, we concentrate on the technical aspects of performing epicardial ablation for ventricular tachycardia (VT), including the management of potential complications.
How to perform ethanol ablation of the vein of Marshall for treatment of atrial fibrillationThe arrhythmogenicity of the vein of Marshall (VoM) in atrial fibrillation (AF) has been known for more than 20 years.1 A recent randomized trial showed a reduced odds ratio (0.63; 95% confidence interval 0.41–0.97; P = .04) for the primary outcome of AF or atrial tachycardia (AT) recurrence in patients with persistent AF by adding VoM ethanol infusion (VoM-Et) to the standard ablation approach.2 The VoM is involved in 30% of ATs after AF ablation, and VoM ablation significantly improves the freedom from recurrent arrhythmia.
Left atrial appendage occlusion using intracardiac echocardiographyLeft atrial appendage (LAA) closure (LAAC) has emerged as an alternative prevention strategy for patients with nonvalvular atrial fibrillation and contraindications to long-term anticoagulation.1 In randomized trials studying the Watchman device (Boston Scientific, St. Paul, MN), implantation was performed under transesophageal echocardiography (TEE) guidance.1 The use of TEE often mandates the presence of general anesthesia and an additional cardiologist or anesthesiologist to perform TEE. This uses greater health care resources and adds additional complexity to the procedure.
How to use intracardiac echocardiography to guide catheter ablation of outflow tract ventricular arrhythmiasThe anatomy of the ventricular outflow tracts and semilunar valves as it pertains to catheter ablation of outflow tract ventricular arrhythmias (OTVAs) has been described.1 Assessment of semilunar valve and regional anatomy by fluoroscopy and angiography has limitations. Coronary arteries may be subject to damage from catheter ablation near the semilunar valves due to their proximity to sites of origin of OTVAs. Detailed intracardiac echocardiographic (ICE) views of the semilunar valves may be useful to understand the anatomy, catheter location, and coronary artery proximity and variations.
When bigger is better: Novel use of a 27 F leadless pacemaker delivery sheath for femoral lead extractionsAs the implantation rate of cardiac implantable electronic devices has continued to increase, lead extractions for clinical indications such as infection, lead failure, and lead recall have also increased.1 A femoral approach to transvenous lead extractions is needed when removing previously cut and abandoned leads, leads that disrupt during a superior extraction attempt and in some cases involving central venous obstruction.2
A beginner's guide to permanent left bundle branch pacingStudies have demonstrated the feasibility and clinical benefits of permanent His-bundle pacing (HBP).1 However, concerns regarding higher pacing thresholds, lower R-wave amplitudes, and the potential to develop distal conduction block have limited the clinical application of HBP in certain subgroups.1,2
Mitral isthmus ablation: A hierarchical approach guided by electroanatomic correlationMitral isthmus ablation is an established technique used to treat perimitral atrial flutter. The classic approach involves creating an ablation line connecting the left inferior pulmonary vein (LIPV) to the lateral mitral annulus.1 Its feasibility was first prospectively studied by Jais et al,1 who reported a high rate of bidirectional block. However, subsequent studies by the same group, as well as others, have been less promising.2 This is important because failure to achieve bidirectional block with ablation has been shown to be proarrhythmic.
Retrograde venous ethanol ablation for ventricular tachycardiaRadiofrequency catheter ablation (RFCA) has been considered the first-line therapy for treatment of drug-refractory ventricular arrhythmias (VAs).1 The success of catheter ablation depends on our ability to reach the anatomic location of the ventricular tachycardia (VT) substrate. VTs arising from deep intramural regions2 or in close proximity to coronary vessels3 can have limited RFCA success. Transarterial coronary ethanol ablation has been used as an alternative treatment option and is reasonably successful in treating RFCA-refractory VTs.
Cosmetic aspects of device implantationThe cosmetic aspects of device implantation imply achieving an aesthetically pleasing surgical result. It involves concealing the cardiac implantable electronic device, avoiding unsightly scars, device bulges, and protrusion (Figure 1). Cosmetic device implantation is indicated for the extremely thin patient at risk of erosion and the young patient concerned with body image. These techniques are also important in the pediatric population, patients with burn injury, and patients after mastectomy.
How to perform left atrial appendage electrical isolation using radiofrequency ablationAlthough pulmonary vein (PV) isolation (PVI) has been considered an effective treatment for paroxysmal atrial fibrillation (AF), non-paroxysmal AF is a complex arrhythmia for which no ablation strategy has been demonstrated to be effective and widely accepted. As such, a success rate of ∼55% in these patients with AF (Substrate and Trigger Ablation for Reduction of Atrial Fibrillation Trial Part II [Star AF II trial]) is not acceptable in our opinion and efforts should be made to seek for alternative strategies.
Approach to permanent His bundle pacing in challenging implantsRight ventricular apical pacing has been the cornerstone of bradycardia pacing for decades. It is well established that right ventricular pacing leads to ventricular dyssynchrony, reduced left ventricular function, and heart failure.1,2 Since the initial description of permanent His bundle pacing (HBP) by Deshmukh et al in 2000,3 several investigators have demonstrated the clinical utility of HBP in patients with atrioventricular (AV) nodal block, infranodal AV block, and bundle branch block.4–7 Increasing interest in HBP has been hampered in part by challenges and limitations associated with a limited implantation tool set.
How to map and ablate parahisian ventricular arrhythmiasVentricular tachycardia (VT) and premature ventricular contractions (PVCs) originating in the vicinity of the His-bundle region represent 3%–9% of all idiopathic ventricular arrhythmias (VAs).1,2 In addition, patients with cardiomyopathies and scar-related VT may exhibit septal arrhythmogenic substrate involving the parahisian region.3 Catheter ablation of these arrhythmias poses particular challenges because of the risk of inadvertent atrioventricular (AV) block, and a systematic approach is important to improve outcomes and minimize complications.
Implantation of the subcutaneous implantable cardioverter–defibrillator with truncal plane blocksOperative anesthetic requirements and perioperative discomfort are barriers to wide adoption of the subcutaneous implantable cardioverter–defibrillator (SICD) system. The SICD implant procedure involves incision and dissection in the richly innervated midaxillary line of the chest wall for placement of the pulse generator and tunneling in subcutaneous tissue for implantation of the defibrillator lead.1 Intraoperative local anesthetic wound infiltration is routine and provides moderate analgesia, but the effects are short-lasting, and complete coverage of the affected areas is difficult.
Evaluation of shortness of breath after atrial fibrillation ablation—Is there a stiff left atrium?Ablation has emerged as the most effective therapy for atrial fibrillation (AF), with the primary goal to improve symptoms. However, there is a subset of patients who develop limiting symptoms after successful ablation despite reestablishment of sinus rhythm. There is now recognition of “stiff left atrial (LA) syndrome” related to adverse consequences of ablation itself on LA hemodynamics, as described by Gibson and others.1,2 Although relatively uncommon (1.4% incidence in the Gibson series), this syndrome is important to diagnose, as it can cause severe unexplained dyspnea.
Transcatheter/leadless pacingEntirely self-contained cardiac pacing systems for direct implantation within the heart via deflectable catheter are now available for use in humans. Worldwide, there have been more 7000 implants of the “transcatheter” or “leadless” pacemaker.∗ The concept of these pacing systems is far from new; Spickler et al.1 were able to achieve cardiac pacing in animals using a capsular nuclear-powered system in 1970. However, only recently has technology enabled sufficient miniaturization to make transcatheter pacing feasible.
When and how to target atrial fibrillation sources outside the pulmonary veins: A practical approachPulmonary vein (PV) isolation is an effective procedure in patients with paroxysmal atrial fibrillation (AF). For most patients with persistent AF and a subset of patients with paroxysmal AF, however, PV isolation may not be sufficient. Patients with the persistent form are more often beleaguered with comorbidities, which result in a greater degree of structural alterations that contribute to the maintenance of AF. In addition, the atrial activation rate during AF is higher (as evidenced by a shorter AF cycle length) in patients with persistent AF, consistent with a greater degree of electrical remodeling.
How to perform transconduit and transbaffle puncture in patients who have previously undergone the Fontan or Mustard operationThe incidence of arrhythmia is high in patients who have undergone a surgical procedure for complex congenital heart disease.1 Catheter ablation is a good therapeutic option to achieve a cure for tachyarrhythmia or a decrease in tachycardia burden. However, there are considerable limitations for a catheter approach to the heart in patients who have undergone a lateral tunnel or extracardiac conduit Fontan operation or an atrial switch operation (eg, Senning operation or Mustard operation).2 In these patients, a transconduit or transbaffle puncture is needed for electrophysiological procedures.
How to map and ablate papillary muscle ventricular arrhythmiasThe papillary muscles (PMs) are a source of ventricular arrhythmias (VAs) in both structurally normal and abnormal hearts. Presentation includes isolated premature ventricular contractions (PVCs), nonsustained ventricular tachycardia (VT), and sustained recurrent VT. In addition, PVCs arising from the PMs may play a role as triggers of ventricular fibrillation (VF).1,2 Because of their highly variable and complex anatomy and independent motion during the cardiac cycle, catheter ablation is challenging, with lower procedural success and higher recurrence rates compared with other locations.
Fluoroless catheter ablation of atrial fibrillationAlthough the concept of performing fluoroless catheter ablation of atrial fibrillation (AF) was introduced several years ago, it has yet to gain wide adoption.1,2 Despite its well-documented advantages, there are several impediments, including concern that a fluoroless approach will add time to the procedure and may require a second operator. However, perhaps the greatest obstacle is that many electrophysiologists are trained to rely on fluoroscopic imaging and are therefore reluctant to trust intracardiac echocardiography (ICE) as their primary visual modality for tracking catheter movement and manipulation.
Epicardial substrate ablation for Brugada syndromeBrugada syndrome (BrS), characterized by the presence of coved-type ST-segment elevation followed by T-wave inversion in the right precordial electrocardiogram (ECG) leads in patients who have no structural heart disease but have a high risk of sudden cardiac death from ventricular fibrillation (VF), has captivated arrhythmia scholars and electrophysiologists for more than 2 decades. As a result, major progresses have been made toward a better understanding of the syndrome with respect to its genetic basis, underlying pathophysiology, and risk stratification.
How to map and ablate left ventricular summit arrhythmiasCatheter ablation of idiopathic ventricular arrhythmias (VAs) is highly successful, with overall cure rates >90%, and is accepted as a first-line therapy by current guidelines.1 However, despite the advances in mapping and ablation techniques, there is a percentage of patients in whom successful ablation cannot be achieved because of anatomic limitations. In this regard, one of the most challenging clinical problems that electrophysiologists may face in the laboratory is the approach to VAs arising from the summit of the left ventricle (LV).
Novel approach to intraprocedural cardiac tamponade: Dual-site drainage with continuous suctionPericardial effusion and cardiac tamponade is an infrequent complication of invasive electrophysiologic procedures, with an estimated risk of 1%–3%.1–3 The most common procedures with increased risk for myocardial perforation are complex ablation during endocardial mapping and/or ablation, transseptal access, and lead placement for device therapy. Although early recognition with supportive management and immediate drainage with pericardiocentesis are necessary to prevent acute hemodynamic instability, the threshold for recommending surgical correction compared to conservative management is not well established.
How to perform permanent His bundle pacing in routine clinical practiceOver the years, various sites of ventricular pacing have been evaluated in clinical trials. Earlier trials established the detrimental effects of right ventricular (RV) apical pacing, including increased risk of atrial fibrillation, heart failure (HF), and mortality. Alternate RV pacing sites have yielded mixed results.1 Biventricular (BiV) pacing in advanced HF and electrical dyssynchrony reduced HF hospitalizations and mortality. Recently, 2 trials evaluated the clinical utility of BiV pacing in the setting of heart block and demonstrated equivocal results.
Enhanced cardiac device management utilizing the random EGM: A neglected feature of remote monitoringRemote monitoring (RM) of cardiac implantable devices is rapidly becoming the standard of care for implantable cardiac device follow-up.
Nodo- and fasciculoventricular pathways: Electrophysiological features and a proposed diagnostic algorithm for preexcitation variantsFasciculoventricular and nodoventricular pathways (FVP and NVP) are uncommon preexcitation variants that can be misleading during electrophysiology studies (EPSs), and differentiating them could be challenging.1–3 In this article, we describe 2 representative cases and then we present various electrophysiological features and phenomenon encountered in patients with these particular accessory pathways (APs).
Pulmonary vein signal interpretation during cryoballoon ablation for atrial fibrillationThe recognition that paroxysmal atrial fibrillation (AF) is predominantly triggered by ectopic beats arising from the vicinity of pulmonary veins (PVs) has spurred the establishment of percutaneous procedures specifically designed to electrically sequestrate the arrhythmogenic PV from the vulnerable left atrium (LA) substrate.1 Recently, the procedure has evolved with the development of purpose-built pulmonary vein isolation (PVI) tools, such as the cryoballoon catheter. This article discusses the anatomic and electrophysiologic bases for the interpretation of pulmonary vein potentials (PVPs) using a small-caliber circular mapping catheter (CMC) and provides an expanded discussion on the pacing maneuvers relevant to cryoballoon-based PVI procedures.
Prevention of phrenic nerve injury during interventional electrophysiologic procedures
The advent of innovative, potent ablative technologies and the adoption of endo–epicardial approaches to treat various arrhythmias have engendered a need for developing strategies to prevent collateral damage to critical structures such as the phrenic nerve (PN) and the esophagus during percutaneous electrophysiologic interventions. Here we detail phrenic nerve injury (PNI) prevention strategies during atrial fibrillation (AF), atrial tachycardia (AT), and ventricular tachycardia (VT) ablation. PNI is more common on the right side because of the anatomic course of the nerve and the greater preponderance of AF and AT ablations.
Safety and prevention of complications during percutaneous epicardial access for the ablation of cardiac arrhythmiasSince its introduction, percutaneous epicardial access is increasingly being performed to facilitate catheter ablation of ventricular tachycardias (VTs) with epicardial circuits, difficult cases of idiopathic VTs, focal atrial tachycardia, and accessory pathways that cannot be successfully targeted endocardially.1 A thorough understanding of the clinical anatomy and potential complications is vital in order to perform a safe procedure.2 In this article, we present the clinical anatomy related to epicardial access, the technique of performing a subxiphoid epicardial puncture, and various measures to prevent complications.
LAA ligation using the LARIAT suture delivery device: Tips and tricks for a successful procedureChronic oral anticoagulation (OAC) has traditionally been considered as the most effective prophylaxis against thromboembolic events in patients with atrial fibrillation (AF). However, as many as 20% of the patients with AF are not candidates for OAC.1,2 Reasons for ineligibility range from intracranial bleeding (the most serious complication) to increased propensity for mechanical injury (the least serious complication). The resumption of OAC in patients who have suffered a life-threatening complication due to OAC is associated with a much higher risk of such events in the future.
Safety and feasibility of transseptal puncture for atrial fibrillation ablation in patients with atrial septal defect closure devicesAF is often found in association with an ASD.1–4 There are an increasing number of patients undergoing transcatheter closure of an ASD who subsequently develop AF in clinical practice.2–4 Catheter ablation has emerged as an effective treatment strategy for drug-refractory symptomatic AF.5 While transseptal access to the left atrium (LA) is a prerequisite for AF ablation, it may prove difficult in the presence of an ASD closure device.6,7 Anticipating technical difficulties and potential complications may discourage operators from considering catheter ablation of AF in this particular patient population.
Two-incision technique for implantation of the subcutaneous implantable cardioverter-defibrillatorThree incisions in the chest are necessary for implantation of the entirely subcutaneous implantable cardioverter-defibrillator (S-ICD). The superior parasternal incision is a possible risk for infection and a potential source of discomfort. A less invasive alternative technique of implanting the S-ICD electrode—the two-incision technique—avoids the superior parasternal incision.
How to perform ventricular tachycardia ablation with a percutaneous left ventricular assist deviceA majority of patients with structural heart disease and scar-related ventricular tachycardia (VT) have fast, hemodynamically unstable VT.1 In fact, up to one-fifth of the patients have only unstable VT, which precludes detailed activation and entrainment mapping.2 In addition, even in those with well-tolerated VT, procedural success can be complicated by acute heart failure as a consequence of prolonged episodes of induced VT and intravascular volume expansion; and one consequence of this acute decompensated heart failure is a significant increase in the short-term morbidity and mortality of the procedure.
A straightforward, reliable technique for retaining vascular access during lead replacementDuring the removal or replacement of device leads, it is often desirable to retain vascular access, which removes any risk of complications from venous cannulation techniques. In this article, I describe a rapid, safe, and flexible technique for the replacement of a nonadherent device lead while preserving vascular access.
How to perform antral pulmonary venous isolation using the cryoballoonThis article describes our current practice, clinical outcomes, and future directions for the use of balloon cryoablation for the treatment of atrial fibrillation.
Management of hemopericardium related to percutaneous epicardial access, mapping, and ablationPercutaneous epicardial access (Figs. 1A and 1B) has gained wide acceptance as an interventional technique to access the pericardial space. Since its initial description1 in targeting epicardial circuits of ventricular tachycardia (VT) in patients with Chagasic cardiomyopathy, percutaneous epicardial access and ablation has come to play an important role in interventional electrophysiology. This technique has been recognized as a vital addition to catheter ablation of certain cardiac arrhythmias and for the delivery of newer investigational devices such as epicardial suture ligation of the left atrial appendage.
Recording and interpreting unipolar electrograms to guide catheter ablationElectrophysiology laboratories commonly use closely spaced bipolar recordings for mapping. However, unipolar recordings have some useful features that can provide additional complimentary information, provided the limitations of these recordings and the particular recording techniques are recognized.
Implantable cardioverter-defibrillators in congenital heart disease: 10 programming tipsAdvances in cardiac care of the young have given rise to a growing and aging population of patients with congenital heart disease. Despite remarkable improvements in overall survival, sudden cardiac death remains the most common cause of late mortality. As a result, implantable cardioverter-defibrillators (ICDs) are increasingly used in this heterogeneous patient population. Tetralogy of Fallot and transposition of the great arteries are the most prevalent subtypes of congenital heart disease in ICD recipients.
Left cardiac sympathetic denervation for the prevention of life-threatening arrhythmias: The surgical supraclavicular approach to cervicothoracic sympathectomyThe progressive understanding of the diseases associated with significant risk for sudden cardiac death has fostered the development of early diagnosis and risk stratification. Thus, instead of starting from either a sudden death victim or a survivor of a cardiac arrest, it has become relatively common for cardiologists to identify individuals at high risk for sudden death, often after an arrhythmic nonlethal cardiac event such as syncope. Besides ischemic heart disease, it has also been recognized that children and young adults can be affected by arrhythmogenic disorders of genetic origin with a high propensity for lethal arrhythmias.
How to troubleshoot the electroanatomic mapAn electroanatomical mapping system is a useful tool for complex arrhythmia ablation. The system reconstructs the precise 3-dimensional chamber of interest with electrical and anatomical information. There are several technical aspects that physicians should be aware of to maximize its efficacy. This review provides relevant information on troubleshooting of the mapping system.
How to perform and interpret rotational angiography in the electrophysiology laboratorySophisticated imaging methods have been growing in popularity since the introduction of curative ablation procedures for atrial fibrillation (AF). This trend is predicated on the need for a precise anatomic guidance within the complex left atrial (LA) anatomy and less reliance on electrocardiographic characteristics of the substrate. Traditional two-dimensional imaging methods such as fluoroscopy would not satisfy the needs of a complex catheter navigation inside three-dimensional (3D) anatomic structures that may not be confined to the radiographic cardiac silhouette (e.g., pulmonary veins [PVs]).
How to implant a defibrillation coil in the azygous veinImplantable cardioverter-defibrillator (ICD) defibrillation testing may reveal failure to achieve a satisfactory safety margin (conventionally, ≥10 J below the maximum energy of the generator) for defibrillation. Options for modification of the defibrillation threshold include repositioning of the ventricular lead, use (or removal) of a defibrillation coil in the superior vena cava (SVC), reversal of shock polarity, and modifying the shock waveform (not available in all devices). Additional defibrillator coils can be added to the subcutaneous space, the subclavian vein, or the coronary sinus.
How to diagnose and treat cardiac tamponade in the electrophysiology laboratoryAs certain as death and taxes occur, complications will occur when invasive procedures are performed. Pericardial effusion, with or without tamponade, is a well-documented complication even in the most experienced centers.1,2 As a result, electrophysiologists should know how to recognize and manage this complication over the course of their careers. In most situations, the outcome is excellent if the complication is recognized and managed expeditiously; however, delay in diagnosis and treatment can lead to catastrophic results.
CRT delivery systems based on guide support for LV lead placementDespite improvements in LV pacing leads, their placement continues to be limited by the coronary venous anatomy. Frequently, the angioplasty wire does not provide adequate support to advance the LV lead into the vein. However, a guiding catheter preshaped to fit into the ostium of the target can easily provide the required support.1,2 Many implanting physicians are reluctant to adopt preshaped guides for direct LV lead delivery because of lack of familiarity with the approach to open lumen catheter manipulation and contrast injection.
How to use balloons as anchors to facilitate cannulation of the coronary sinus left ventricular lead placement and to regain lost coronary sinus or target vein accessCoronary venous anatomy can make successful implantation of a cardiac resynchronization therapy device difficult or impossible. Venogram and coronary balloons can be used as anchors to facilitate initial coronary sinus (CS) cannulation and left ventricular lead placement and to recover lost CS and target vein access.
Catheter ablation in tetralogy of FallotTetralogy of Fallot is the most common form of cyanotic heart disease, accounting for approximately 10% of congenital heart defects. Corrective surgery involves atrial and/or ventricular incisions and patches that, when combined with altered hemodynamics, predispose to the late onset of arrhythmias.1,2 In a multicenter cohort followed up for 35 years after corrective surgery, sustained atrial and ventricular tachyarrhythmias occurred in 10% and 12% of patients, respectively.1 Macroreentrant right atrial tachycardia is the most common atrial arrhythmia.
Catheter ablation in transposition of the great arteries with Mustard or Senning bafflesComplete transposition of the great arteries (D-TGA) accounts for 5% to 7% of congenital heart defects. Although the arterial switch procedure has now replaced atrial redirection as the surgical procedure of choice, most adults today with D-TGA have had Mustard or Senning baffles. These surgeries involve extensive atrial reconstruction and predispose to sinus node dysfunction and atrial tachyarrhythmias.1,2 By 20 years after surgery, the prevalence of atrial tachyarrhythmias is approximately 25%, continues to increase with time, and is similar among patients with Mustard or Senning baffles.
How to perform magnetic resonance imaging on patients with implantable cardiac arrhythmia devicesMagnetic resonance imaging (MRI) offers unrivaled soft tissue resolution and multiplanar imaging capabilities. Cardiac MRI is capable of accurate characterization of cardiac function and is uniquely capable of identifying scar fibrosis and fat deposition, thus making it an ideal imaging modality for the evaluation of patients presenting with arrhythmia. In addition, the absence of x-ray radiation makes MRI suitable for follow-up of chronic disease and for imaging in young patients and women of childbearing age.
How to identify the location of an accessory pathway by the 12-lead ECGRadiofrequency catheter ablation has become the treatment of choice for patients with symptomatic Wolff-Parkinson-White syndrome (WPW). The QRS complex morphology present on the 12-lead electrocardiogram (ECG) in WPW patients depends on the location of the accessory pathway(s) (AP) and the degree of fusion over the normal atrioventricular (AV) conduction. Accordingly, it is determined by the site of ventricular insertion of the accessory pathway, AV node conduction time, and atrial conduction.
Ablation above the semilunar valves: When, why, and how? Part IIn this two-part series, we discuss the anatomical basis for arrhythmias arising above the semilunar valves. In this part (part I), we describe the relevant anatomy and technique for mapping and ablation of ventricular arrhythmias arising above either the pulmonic or the aortic valve. After an initial discussion of the underlying anatomy and characteristics of the substrate targeted for ablation above the semilunar valve, an approach for safe and effective ablation of supravalvar ventricular arrhythmias is presented.