Renal Denervation for Treatment of Cardiac Arrhythmias: State of the Art and Future Directions

Renal Denervation for Treatment of Cardiac Arrhythmias . It has now been more than a quarter of a century since modulation of the sympathetic nervous system was proposed for the treatment of cardiac arrhythmias of different origins. But it has also been some time since some of the early surgical attempts have been abandoned. With the development of ablation techniques, however, new approaches and targets have been recently introduced that have revolutionized our way of thinking about sympathetic modulation. Renal nerve ablation technology is now being successfully used for the treatment of resistant hypertension, but the indication spectrum might broaden and new therapeutic options might arise in the near future. This review focuses on the possible impact of renal sympathetic system modulation on cardiac arrhythmias, the current evidence supporting this approach, and the ongoing trials of this method in electrophysiological laboratories. We will discuss the potential roles that sympathetic modulation may play in the future.     

Radiofrequency Catheter Ablation of the Anterosuperior and Posteroinferior Atrial Approaches to the AV Node for Treatment of AV Nodal Reentrant Tachycardia

Catheter Ablation Techniques in AVNRT. Radiofrequency catheter ablation has been established as a first-line curative treatment modality in patients with symptomatic AV nodal reentrant tachycardia (AVNRT). The successful sites of stepwise catheter ablation approaches of the so-called fast and slow pathways strongly suggest that AVNRT involves the atrial approaches to the AV node. The typical fast pathway ablation sites are located anterosuperior toward the apex of the triangle of Koch, which also contains the compact AV node, whereas the usual slow pathway ablation sites are located posteroinferior toward the base of the triangle of Koch at a greater distance to the compact AV node and bundle of His. Accordingly, ablation studies with large patient cohorts have demonstrated that fast pathway ablation carries a higher risk of inadvertent complete AV block. Thus, the slow pathway is clearly the primary target site, and fast pathway ablation is rarely necessary. Different approaches for slow pathway ablation have been elaborated: anatomically oriented stepwise techniques, ablation guided by double potentials recorded within the area of the slow pathway insertion, and combined techniques. The modern concept of AVNRT suggests that this arrhythmia involves the highly complex three-dimensional nonuniform anisotropic AV junctional area. Accordingly, mapping and ablation studies demonstrated that the anterior approach is not identical with fast pathway ablation, and the posterior approach is not identical with slow pathway ablation. Therefore, it is essential for interventional electrophysiologists to familiarize themsdves with the anatomic and electrophysiologic details of this complex and variable specialized AV junctional region. In this review, the anatomic and pathophysiologic aspects of the AV junctional area as they relate to interventional therapy are summarized briefly, and the catheter techniques for ablation of the so-called fast and slow AV nodal pathways for the treatment of AVNRT are described.     

The Myocardial Lesions Produced by the Potassium Channel Opener Aprikalim in Monkeys and Rats Are Prevented by Blockade of Cardiac {beta}-Adrenoceptors

Aprikalim is a potent, specific, and selective opener of ATP-sensitiveK⁺ (K_ATP) channels. By virtue of this pharmacological property,aprikalim affords cardioprotection in experimental models ofischemia/reperfusion injury, and, at higher doses, also causesperipheral or coronary vasodilatation. Direct-acting peripheralvasodilators can cause myocardial lesions, particularly in ratsand dogs. However, unexpectedly, aprikalim produced this effectalso in monkeys. Thus, the primary aim of this investigationwas to assess whether in monkeys these myocardial lesions werethe direct or indirect consequence of the vascular effects ofaprikalim. Cyno-mologus monkeys were given the ß-adrenoceptorantagonist nado-lol (2 mg/kg po, twice daily) for 4 consecutivedays. On the third and fourth day of the experiment, they receivedaprikalim (1 mg/kg po). In another series, two monkeys carryingtelemetry transmitters for blood pressure and heart rate measurementswere also given aprikalim or its vehicle. Finally, aprikalim(1 mg/kg po for 2 days) or its vehicle was administered to ratswhich were concurrently treated with the ß-adrenoceptorantagonist atenolol (5 mg/ kg sc) or its vehicle. In cynomologusmonkeys, aprikalim produced focal and multifocal myocardialnecrosis of minimal to moderate intensity in or near the papillarymuscles of the left ventricle. These effects were abrogatedby nadolol. Similarly, necrotic lesions were caused by aprikalimonly in those rats which had not been pretreated with atenolol.In monkeys, aprikalim produced a marked and long-lasting decreasein aortic blood pressure, accompanied by an even more prolongedtachycardia. These results demonstrate that aprikalim can producemyocardial necrosis not only in rats but also in monkeys. Toour knowledge, this is the first time that such adverse effectsare reported for a vasodilator in monkeys. More importantly,these effects were prevented by blocking cardiac ß-adrenoceptors.Thus, the myocardial lesions produced by aprikalim may be attributedto its profound and prolonged hemodynamic effects.     

Temperature-controlled Radiofrequency Catheter Ablation of Accessory Pathways and Atrioventricular Nodal Reentrant Tachycardia: The 5-French Catheter Approach

Ablation with Temperature-Controlled 5-French Catheters. Introduction: In the present study, we assessed the feasibility of radiofrequency (RF) ablation of accessory pathways and AV nodal reentrant tachycardias with novel 5-French catheters with 4-mm tip electrodes using established mapping criteria and temperature-controlled power output control. Methods and Results: In this prospective study, 60 consecutive adult patients (mean age 36 ± 20 years) with accessory pathways (n = 37; 24 left-sided) or AV nodal reentrant tachycardia (n = 23) underwent RF catheter ablation. A 5-French catheter with a 4-mm tip electrode and an embedded thermistor was used for RF application. The surface of the tip electrodes was 26 mm2 compared to 38 mm² of 7-French catheters with 4-mm tip electrodes from the same catheter series. Power output was automatically and continuously adjusted according to the preset catheter tip temperature of 60° to 70°C. Pulse duration was 90 seconds. For left-sided accessory pathways, the retrograde route via the femoral artery was used. After removing the 5-French sheaths, only 4 hours of bed rest were advised. For ablation of AV nodal reentrant tachycardia, the so-called slow pathway was targeted for ablation. Acute success was achieved in 34 (92%) of 37 patients with accessory pathways and 23 (100%) of 23 patients with AV nodal reentrant tachycardia. A mean of 3 ± 4 RF pulses (median 2 pulses; range 1 to 20 pulses) was applied. The mean fluoroscopy time was 26 ± 21 minutes. No complete AV block or other procedure-related complications were observed. Recurrences occurred in 2 patients with accessory pathways and in 2 patients with AV nodal reentrant tachycardia during a follow-up of 9 ± 4 months. Conclusions: Temperature-controlled RF ablation of accessory pathways and AV nodal reentrant tachycardia in adults using 5-French catheters is feasible, effective, and safe. Ablation with 5-French catheters might help to reduce the complication rate of catheter ablation techniques.     

Radiofrequency Catheter Ablation of Idiopathic Left Ventricular Tachycardia:

Idiopathic Left Ventricular Tachycardia. Introduction: Idiopathic left ventricular tachycardia with a QRS pattern of right bundle branch block and left-axis deviation constitutes a rare but electrophysiologically distinct arrhythmia entity. The underlying mechanism of this tachycardia, however, is still a matter of controversy. This report describes findings in a 42-year-old man who underwent successful radiofrequency catheter ablation of idiopathic left ventricular tachycardia.
Methods and Results: On electrophysiologic study, the tachycardia was reproducibly induced and terminated with double ventricular extrastimuli. Intravenous verapamil terminated the tachycardia whereas adenosine did not. Detailed left ventricular catheter mapping during sinus rhythm revealed a fragmented delayed potential at the mid-apical region of the inferior site near the posterior fascicle of the left bundle branch. At the same site, continuous electrical activity throughout the entire cardiac cycle was recorded during ventricular tachycardia. Repeated spontaneous termination of this continuous electrical activity in late diastole was followed immediately by termination of the tachycardia. Single application of radiofrequency current for 20 seconds at this site completely abolished inducibility of the tachycardia. After catheter ablation, at the identical site of preablation recording of the fractionated potential during sinus rhythm, no fragmented delayed activity could be recorded. There was no complication from the ablation procedure.
Conclusion: The preablation recordings of fragmented delayed potentials during sinus rhythm and continuous diastolic electrical activity during tachycardia, together with ablation characteristics and previously reported electrophysiologic properties of this arrhythmia, may further support microreentry as the underlying mechanism in idiopathic left ventricular tachycardia.     

Left Ventricular Diastolic Dysfunction in Atrial Fibrillation: Predictors and Relation with Symptom Severity

Left Ventricular Diastolic Dysfunction in Atrial Fibrillation Background: Left ventricular diastolic dysfunction (LVDD) is common in the general population, but its prevalence in atrial fibrillation (AF), predictors for LVDD in AF and the association between LVDD and AF‐related symptom severity has not been well studied. Methods: In 124 consecutive patients (mean age 61 ± 11years, 60% male) with paroxysmal (n = 70) or persistent AF (n = 54) referred for AF catheter ablation, LVDD was evaluated according to current guidelines using transthoracic echocardiography. AF‐related symptom severity was quantified using the European Heart Rhythm Association score. Results: LVDD was present in 46 patients (37%). In uni‐ and multivariable regression analysis, age (OR 1.068 per year, 95% CI 1.023–1.115, P = 0.003) and persistent AF (OR 2.427 vs. paroxysmal AF, 95% CI 1.112–5.3, P = 0.026) were associated with LVDD. LVDD was found in 11% with mild AF symptoms (n = 27) as opposed to 44% in patients with moderate–severe AF symptoms (n = 97, P = 0.002). Thus, the OR for moderate–severe AF symptoms was 6.368 (1.797–22.568, P = 0.004) in the presence of LVDD. Conclusions: LVDD (1) occurs frequently in AF, (2) is associated with advancing age and AF progression and (3) is correlated with symptom severity in AF. (J Cardiovasc Electrophysiol, Vol. 23 pp. 1073‐1077, October 2012)     

Phrenic Nerve Stimulation for Central Ventilatory Failure with Bipolar and Four-Pole Electrode Systems

A multi-channel phrenic nerve stimulator developed in Tampere has been implanted into seven patients with C2-tetraplegia and into three patients with central sleep apneas. Six bipolar cuff electrodes were implanted bilaterally into the neck. Two four-pole cuff and 14 four-pole noncuff electrodes were used in seven patients and to replace one bipolar electrode. Four-pole electrodes were implanted within the thorax. Seven patients achieved total independence from conventional ventilators within 4 months of implantation, and one for 18 hours each day. Two patients died 12 days and 3 months after implantation and two patients after having achieved independence from mechanical ventilators from causes unrelated to the stimulators. Reoperations were necessary because of dislocation of receivers, electrodes, electrode lesions, nerve injuries, and technical failures in seven patients. Most of the problems appeared in two patients with obesity and in three patients with very thin phrenic nerves. Single unit prototypes failed technically more frequently than units of prototype serial fabrication. New electrode design, progress in the manufacture of receivers, and improved implantation technique should help to diminish failures in future.     

Long-term effects of otitis media with effusion on language,reading and spelling

The long-term effects of early OME on language and educational attainment were studied in 47 children of 7–8 years of age who had participated in earlier pre-school study¹ on otitis media with effusion (OME) and language development. At pre-school age OME was diagnosed by quarterly tympanometric screens (maximum nine) and language was assessed by a standard Reynell gtest. At school age the ears of the children were assessed by otomicroscopy, tympanometry and audiometry, and the development status by several language, reading and spelling tests. The association between early OME and language development found at pre-school age was no longer present at school age.     

Catheter Ablation of Recurrent Scar-Related Ventricular Tachycardia Using Electroanatomical Mapping and Irrigated Ablation Technology: Results of the Prospective Multicenter Euro-VT-Study

Catheter Ablation of Ventricular Tachycardia.   Introduction: Ventricular tachycardia (VT) late after myocardial infarction is an important contributor to morbidity and mortality. This prospective multicenter study assessed the efficacy and safety of electroanatomical mapping in combination with open-saline irrigated ablation technology for ablation of chronic recurrent mappable and unmappable VT in remote myocardial infarction.
Methods and Results: In 8 European institutions, 63 patients (89% males) were enrolled in the study. All patients had remote myocardial infarction and presented with a median number of 17 (range 1–380) VTs in the preceding 6 months. Incessant VT was present in 14 patients (22%). Left ventricular ejection fraction measured 30 ± 13%. A mean of 3 VTs were targeted per patient and 22% of all patients had only unmappable VT. The mean follow-up period was 12 ± 3 months. A total of 164 VTs were targeted during catheter ablation. Ablation was acutely successful in 51 patients (81%). One patient (1.5%) experienced a major complication with degeneration of VT into ventricular fibrillation necessitating cardiopulmonary resuscitation maneuvers. However, no death occurred acutely or within the first 30 days after catheter ablation. During the follow-up, 19 of the initially successful ablated patients (37%) and 31 of all ablated patients (49%) developed some type of VT recurrence.
Conclusions: The results of this multicenter study demonstrate the high acute success rate and a low complication rate of irrigated tip catheter ablation of all clinical relevant VTs in remote myocardial infarction. However, during the follow-up a relevant number of recurrences occurred. (J Cardiovasc Electrophysiol, Vol. 21, pp. 47–53, January 2010)