Andrew S. Thornton

Initial experience with catheter ablation using remote magnetic navigation in adults with complex congenital heart disease and in small children

Background: The improved outcomes and increased availability of surgery for congenital heart disease (CHD) over the last three decades have created a small but steadily increasing subset of patients with unique needs: children and adults with complex arrhythmias in the setting of structural cardiac abnormalities. Radiofrequency catheter ablation (RFCA) in these patients, and in small children with normal cardiac anatomy, is effective but challenging. An understanding of specific anatomical and electrophysiological characteristics of these patients and the technical challenges in addressing them are critical to the success of this therapy. Tools specifically designed for intracardiac diagnosis and therapy in anatomically complex and/or small hearts remain scarce.

Use of advanced mapping and remote magnetic navigation to ablate left ventricular fascicular tachycardia.

Ablation of idiopathic left ventricular, or fascicular tachycardia can be aided by electroanatomical mapping. The addition of a floppy, magnetically enabled ablation catheter may improve maneuvering as well as decrease mechanically induced arrhythmias and mechanical block. We describe a case of fascicular tachycardia in which both these modalities were used in a sequential fashion. Integration of these modalities should prove even more helpful.

Magnetic navigation in left-sided AV reentrant tachycardias: preliminary results of a retrograde approach

Introduction: A novel magnetic navigation system allows remote guidance of floppy radiofrequency (RF) ablation catheters. We evaluated the feasibility of mapping and ablation of left‐sided accessory pathways (APs) using the retrograde transaortic approach with this system. This might open the gate to retrograde ablation of left atrial arrhythmias.

Outcome in patients with an ICD incorporating cardiac resynchronisation therapy: Differences between primary and secondary prophylaxis

The incidence of ventricular tachyarrhythmias in ICD patients with cardiac resynchronisation therapy (CRT‐D) is not well studied.

Left Ventricular Lead Placement Within a Coronary Sinus Side Branch Using Remote Magnetic Navigation of a Guidewire: A Feasibility Study

Background: A novel magnetic navigation system (MNS) allowing remote guidance of catheters and guidewires might assist in implantation of left ventricular (LV) pacing leads.

Intracardiac echocardiography during interventional procedures

BACKGROUND As non-surgical percutaneous interventions are increasingly considered for many cardiac conditions, high quality near field continuous imaging is warranted, in order to optimize the results, and to prevent and detect complications. Transesophageal echocardiography is the standard imaging technique, however general anesthesia and endotracheal intubation is required during prolonged monitoring of percutaneous interventions. Intracardiac echocardiography is a novel emerging tool that allows a view within the cardiac chambers and the large vessels and can be employed by the interventional cardiologist. METHOD In our department, a phased array, multi-frequency, four-way steerable catheter (AcuNaV - Siemens) was used for anatomic and haemodynamic cardiac assessment and for guidance and monitoring during non-coronary percutaneous interventions. In total 135 patients underwent intracardiac echocardiographic investigation, 4 during diagnostic heart catheterization, 6 during percutaneous coronary intervention with the use of a new left ventricular assist device, the Impella Recover LP 2.5 system, 26 during percutaneous transluminal septal myocardial ablation (10 patients were reevaluated with intracardiac echocardiography at 6 months), 50 during interatrial communication closure, 4 during percutaneous left atrial appendage transcatheter occlusion, 7 during percutaneous balloon valvuloplasty, 1 during percutaneous aortic valve replacement and 27 during pulmonary vein ablation. All patients tolerated the procedure very well with no catheter related complications. However, there were two complications, which were due to the guidewire and the sheath, an inferior vena cava dissection and a femoral vein dissection, respectively. CONCLUSION Phased array intracardiac imaging is a safe technology, which facilitates non-surgical interventions by providing high quality images. It eliminates the need for general anesthesia and thus increases the patient comfort.

Visualization of a coronary sinus valve using intracardiac echocardiography

Cannulation of the coronary sinus (CS) is sometimes difficult due to the presence of anatomical anomalies. Fluoroscopy is of limited value in visualizing these variations. This case is the first to demonstrate how intracardiac echocardiography (ICE) allows visualization of a valve, which is one of the causes of problematic cannulation of the CS. Based on information obtained by ICE an appropriate catheter could be selected.

An in vivo comparison of radiofrequency cardiac lesions formed by standard and magnetically steered 4 mm tip catheters.

AbstractBackground.In vivo comparison of cardiac radiofrequency ablation lesions between standard and magnetically steered 4 mm tip catheters has never been reported. Methods. High and low right atrium (RA) free wall, isthmus, right ventricle (RV) free wall and outflow tract lesions were studied macroscopically and microscopically five days after lesion formation in seven pigs. Shape, size, thrombus formation, and ablation parameters were compared. The effect of minimal, medium and high wall contact was assessed by a contact measurement utility for magnetic catheters. Results. All 14 RA free wall lesions were transmural with a similar epicardial and endocardial surface area. In the RV, the epicardial area usually appeared to be smaller than the endocardial area with standard catheters. Isthmus lesions were difficult to assess transmurality. There was no difference in endocardial area: standard 39 mm2 (range 16 to 82 mm2) vs. magnetic 36 mm2 (range 23 to 111 mm2). If the catheter tip was perpendicular to the tissue, magnetic lesions were more often round or oval, while standard lesions were more often elongated (p<0.05). When the catheter tip was parallel to tissue, lesions always tended to be elongated. Microscopic characteristics were similar. The contact utility was not useful. Average impedance (p<0.0001) and energy delivered (p<0.05) were less with magnetic catheters. Conclusion. Lesions from magnetically steered catheters are transmural of similar size, but with less variability than standard catheter lesions when the tip is perpendicular to the tissue. Magnetic lesions are associated with lower impedance and energy delivery. This suggests a more stable tip-to-tissue contact. (Neth Heart J 2010;18:66–71.)

ABLATION OF A FOCAL LEFT ATRIAL TACHYCARDIA VIA A RETROGRADE APPROACH USING REMOTE MAGNETIC NAVIGATION

A 66-year-old man who had undergone successful ablation of typical atrial flutter subsequently developed a left atrial tachycardia. A trans-septal approach was proposed, but not performed due to risk. He was referred to us with the suggestion that a retrograde procedure could be attempted using a magnetic navigation system (Niobe, Stereotaxis Inc, St Louis, MO, USA) installed in our institution. We performed multi-slice computed tomography (CT) with three-dimensional reconstruction to allow for use of the CARTO RMT Merge system (Biosense Webster, Diamond Bar, CA, USA). The patient was sedated with diazepam and fentanyl. Heparin was used to maintain the activated clotting time of above 300 s. After placing diagnostic catheters, we approached the left atrium (LA) in a retrograde fashion using a 4 mm tip magnetically enabled ablation catheter (Navistar RMT, Biosense Webster), advancing it to just below the subclavian artery manually. The ablation catheter was then manoeuvred across the aortic and mitral …

Targets and endpoints in ablation therapy for atrial fibrillation in the light of pathophysiological mechanisms

Atrial fibrillation (AF), an important public health problem is a complex and multifactorial arrhythmia. Non-pharmacological treatment for symptomatic patients is of increasing importance. The different catheter ablation techniques in AF treatment developed during recent years, all based on different pathophysiological insights, are discussed. The non-standardized use of different follow-up methods after ablation make interpretation and comparison of results difficult.