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The recent advent of an entirely subcutaneous implantable defibrillator (ICD) has provided a relevant contribution to the debate concerning the use of ICD therapy in patients at high risk for death. Although conventional transvenous ICDs have proven very effective during the past 23 years, they still appear to be limited by nontrivial acute and long-term complications. This study delineates some of the historical and current issues characterizing the advent of the subcutaneous ICD system in daily clinical practice. Subcutaneous ICDs have proven effective in more than 1100 patients worldwide and appear to be competitive with transvenous ICD in all clinical conditions not requiring antibradycardia, antitachycardia, or cardiac resynchronization pacing.

Background— QRS-ST changes in the inferior and lateral ECG leads are frequently observed in athletes. Recent studies have suggested a potential arrhythmogenic significance of these findings in the general population. The aim of our study was to investigate whether QRS-ST changes are markers of cardiac arrest (CA) of unexplained cause or sudden death in athletes. Methods and Results— In 21 athletes (mean age, 27 years; 5 women) with cardiac arrest or sudden death, the ECG recorded before or immediately after the clinical event was compared with the ECG of 365 healthy athletes eligible for competitive sport activity. We measured the height of the J wave and ST elevation and searched for the presence of QRS slurring in the terminal portion of QRS. QRS slurring in any lead was present in 28.6% of cases and in 7.6% of control athletes ( P =0.006). A J wave and/or QRS slurring without ST elevation in the inferior (II, III, and aVF) and lateral leads (V 4 to V 6 ) were more frequently recorded in cases than in control athletes (28.6% versus 7.9%, P =0.007). Among those with cardiac arrest, arrhythmia recurrences did not differ between the subgroups with and without J wave or QRS slurring during a median 36-month follow-up of sport discontinuation. Conclusions— J wave and/or QRS slurring was found more frequently among athletes with cardiac arrest/sudden death than in control athletes. Nevertheless, the presence of this ECG pattern appears not to confer a higher risk for recurrent malignant ventricular arrhythmias.

Accessory pathways with slow and anterograde decremental conduction (Mahaim fibres) are responsible for a minority of atrioventricular reentrant tachycardias. While usually located along the tricuspid annulus, left-sided Mahaim fibres have been occasionally reported. We here report on a unique case of radiofrequency catheter ablation of a Mahaim pathway located at the supero-septal aspect of the mitral annulus, in a region known as mitral annulus-aorta junction, between the right and left fibrous trigons. Electrophysiological properties and embryological implications of this unusual accessory pathway are discussed.

A 25-year-old woman with drug-refractory permanent junctional reciprocating tachycardia (PJRT) and a previous failed ablation, was referred to our institution. Electrophysiological study confirmed the diagnosis of orthodromic atrioventricular reentry tachycardia using a slowly conducting accessory pathway. This accessory pathway was successfully ablated by conventional radiofrequency at the left anteroseptal region using a transseptal approach. Catheter ablation of this accessory pathway (Coumel type) at the mitral annulus-aorta junction offers insights on a rare anatomical location of PJRT.

A 24-year-old female underwent an electrophysiological study because of recurrent episodes of drug-refractory, paroxysmal supraventricular tachycardia. During adrenergic stress, a narrow QRS tachycardia with eccentric atrial activation was reproducibly inducible. The response to premature ventricular extrastimulation during tachycardia suggested the presence of a slowly conducting accessory pathway. However, a comprehensive appraisal of the electrophysiological study delineated the tachycardia substrate as an atypical atrioventricular nodal reentrant tachycardia in the presence of a bystander nodofascicular pathway. Careful analysing of the basal pacing manoeuvers during sinus rhythm (para-Hisian and differential ventricular pacing) was crucial to establish the correct diagnosis and to avoid unnecessary left-side access to ablate this tachycardia.

Although conventional implantable cardioverter-defibrillators (ICDs) have proved effective in the prevention of sudden cardiac death (SCD), they still appear to be limited by non-trivial acute and long-term complications. The recent advent of an entirely subcutaneous ICD (S-ICD) represents a further step in the evolution of defibrillation technology towards a less-invasive approach. This review highlights some historical and current issues concerning the S-ICD that may offer a viable therapeutic option in selected patients at high risk of SCD and in whom pacing is not required. After the CE Mark and US Food and Drug Administration (FDA) approvals, the S-ICD is being implanted worldwide with growing clinical data regarding its safety and efficacy (the EFFORTLESS Registry). The recently developed new generation of S-ICD (EMBLEM, Boston Scientific) demonstrates favourable features including a smaller device, longer longevity and remote-monitoring compatibility. Further innovations in the S-ICD system and potential integration with leadless pacing may play an important role in defibrillation therapy and prevention of SCD in the near future.

EFFICACY OF CATHETER ABLATION AT THE ATRIUM-TOPULMONARY VEIN JUNCTION IN THE TREATMENT OF ATRIAL TACHYARRHYTHMIAS OCCURRING AFTER ANATOMICAL CIRCUMFERENTIAL ABLATION OF ATRIAL FIBRILLATION Riccardo Cappato, MD, Cristina Esposito, MD, Pier Paolo Lupo, MD, Domenico Pecora, MD, Mario Pittalis, MD, Sara Foresti, MD, Luigi Fedele, MD, Hussam Ali, MD, Francesco Furlanello, MD and Luigi De Ambroggi, MD. Istituto Policlinico San Donato, San Donato Milanese, Italy.

A 15-year-old female with WPW syndrome and normal heart underwent an electrophysiology study for paroxysmal palpitations and syncope. Intravenous adenosine produced an unexpected response of QRS changes and advanced AV block. During isoproteronol infusion, short-lasting and poorly tolerated wide QRS tachycardia was inducible, but pacing maneuvers were not feasible during tachycardia to determine its definitive mechanism. However, various electrophysiologic phenomena including adenosine response, junctional beats pattern, and multisite atrial pacing were helpful to overcome the diagnosis challenges. Finally, careful evaluation of tachycardia features and the comprehensive electrophysiology study were crucial to establish presence of unusual preexcitation variants, and thus to guide successful catheter ablation of the arrhythmic substrate.