Epicardial foci of atrial arrhythmias apparently originating in the left pulmonary veins

Catheter Ablation of Paroxysmal Atrial Fibrillation Originating from Non-pulmonary Vein Areas

Pulmonary veins (PVs) are a major source of ectopic beats that initiate AF. PV isolation from the left atrium is an effective therapy for the majority of paroxysmal AF. However, investigators have reported that ectopy originating from non-PV areas can also initiate AF. Patients with recurrent AF after persistent PV isolation highlight the need to identify non-PV ectopy. Furthermore, adding non-PV ablation after multiple AF ablation procedures leads to lower AF recurrence and a higher AF cure rate. These findings suggest that non-PV ectopy is important in both the initiation and recurrence of AF. This article summarises current knowledge about the electrophysiological characteristics of non-PV AF, suitable mapping and ablation strategies, and the safety and efficacy of catheter ablation of AF initiated by ectopic foci originating from non-PV areas.

Epicardial Ablation of Supraventricular Tachycardia

Epicardial catheter-based mapping and ablation of a variety of supraventricular tachycardias is feasible, safe, and effective. Supraventricular tachycardia substrates are not uncommonly epicardial, and approaches with percutaneous epicardial instrumentation or via the epicardial venous structures, such as the coronary sinus, are becoming more widely accepted. These techniques are an important treatment option as an alternative to a more invasive surgical approach or to allowing patients to suffer from an ongoing arrhythmia. New technologies and innovative techniques are being developed that hold great potential to improve the efficacy and safety of the epicardial catheter-based approach to these challenging arrhythmias.

Retrograde ethanol infusion in the vein of Marshall: regional left atrial ablation, vagal denervation and feasibility in humans

BACKGROUND

The vein of Marshall (VOM) is an attractive target during ablation of atrial fibrillation due to its autonomic innervation, its location anterior to the left pulmonary veins and drainage in the coronary sinus.

METHODS AND RESULTS

We studied 17 dogs. A coronary sinus venogram showed a VOM in 13, which was successfully cannulated with an angioplasty wire and balloon. In 5 dogs, electroanatomical maps of the left atrium were performed at baseline and after ethanol infusion in the VOM, which demonstrated a new crescent-shaped scar, extending from the annular left atrium towards the posterior wall and left pulmonary veins. In 4 other dogs, effective refractory periods (ERP) were measured at 3 sites in the left atrium, before and after high-frequency bilateral vagal stimulation. The ERP decreased from 113.6+/-35.0 ms to 82.2+/-25.4 ms (p<0.05) after vagal stimulation. After VOM ethanol infusion, vagally-mediated ERP decrease was eliminated (from 108.6+/-24.1 ms to 96.4 +/-16.9ms, p=NS). The abolition of vagal effects was limited to sites near the VOM (ERP: 104+/-14 ms, vs 98.6+/-12.2 ms post vagal stimulation, p=ns), as opposed to sites remote to VOM (ERP: 107.2+/-14.9 ms, vs 78.6+/-14.7ms post vagal stimulation, p<0.05). To test feasibility in humans, 5 patients undergoing pulmonary vein antral isolation had successful VOM cannulation and ethanol infusion: left atrial voltage maps demonstrated new scar involving the infero-posterior left atrial wall extending towards the left pulmonary veins.

CONCLUSIONS

Ethanol infusion in then VOM achieves significant left atrial tissue ablation, abolishes local vagal responses and is feasible in humans.

Ethanol infusion in the vein of Marshall: Adjunctive effects during ablation of atrial fibrillation

BACKGROUND

The vein of Marshall (VOM) is a left atrial (LA) vein that contains autonomic innervation and triggers of AF. Its location coincides with areas usually ablated during pulmonary vein (PV) antral isolation (PVAI).

OBJECTIVE

This study sought to delineate the safety and ablative effects of ethanol infusion in the VOM during catheter ablation of atrial fibrillation (AF).

METHODS

Patients undergoing PVAI (n = 14) gave consent for adjunctive VOM ethanol infusion. In 10 of 14 patients, the VOM was cannulated with an angioplasty wire and balloon. Echocardiographic contrast was injected in the VOM under echocardiographic monitoring. Two infusions of 100% ethanol (1 ml each) were delivered via the angioplasty balloon in the VOM. LA bipolar voltage maps were created before and after ethanol infusion. Radiofrequency ablation times required to isolate each PV and other procedural data were compared with those of 10 age-, sex-, AF type- and LA size-matched control subjects undergoing conventional PVAI.

RESULTS

The VOM communicated with underlying myocardium, as shown by echocardiographic contrast passage into the LA. There were no acute complications related to VOM ethanol infusion, which led to the creation of a low-voltage area in the LA measuring 10.6 +/- 7.6 cm(2) and isolation of the left inferior PV in 4 of 10 patients. Radiofrequency ablation time required to achieve isolation of the left inferior PV was reduced (2.2 +/- 4 min vs. 11.4 +/- 10.3 min in control subjects, P <.05).

CONCLUSION

VOM ethanol infusion is safe in humans, decreases radiofrequency ablation time in the left inferior PV, and may have a role as an adjunct to PVAI.

Site Localization and Characterization of Pain During Radiofrequency Ablation of the Pulmonary Veins

BACKGROUND

Characteristics of radiofrequency (RF) lesions producing pain with an 8-mm catheter during pulmonary vein (PV) ablation have not been prospectively studied.

METHODS

We studied 46 (30 men, age 56 +/- 10 years) patients with AF who underwent RF ablation of PVs. PV isolation was achieved by using an 8F, 8-mm Biosense ablation catheter (Biosense Webster, Diamond Bar, CA, USA) guided by intracardiac echocardiography (ICE). An electroanatomic map was used to document the location of all RF lesions and the time; PV location and maximum temperature of every lesion were recorded. Location of the esophagus was determined by magnetic resonance imaging prior to the procedure and by both ICE and barium swallows during procedure.

RESULT

A total of 1,448 (33 +/- 12) RF lesions were delivered to 180 veins. Thirty-nine patients (85%) had at least one lesion associated with pain (mean: 8 +/- 5 lesions) during ablation. The RF generator setting during lesions resulting in pain sensation was 48.6 +/- 7.0 Watts and 51.5 +/- 2.9 degrees C. Maximum temperature attained at the time of pain sensation was 45.7 +/- 4.2 degrees C. By logistic regression analysis the left superior PV (OR 1.54, CI 1.06-2.24, LS vs RI, P < 0.05) and left inferior PV (OR 2.74, CI 1.79-4.19, LI vs RI, P < 0.001) location were both positively correlated with the production of pain. The location of lesions associated with pain was not near the esophagus during any of the pain-producing lesions.

CONCLUSION

Pain sensation is relatively common during RF ablation of PVs. There was no correlation between pain and the location of esophagus. Pain was more common during RF ablation of left inferior and left superior PVs.

The ligament of Marshall as a parasympathetic conduit

The objective of the study was to investigate the morphology, distribution, and electrophysiological profile of the autonomic fibers that innervate the ligament of Marshall (LOM). Gross anatomical dissections were performed in 10 dogs. Sections of the left vagus nerve, left stellate ganglion, and the LOM were immunostained to identify adrenergic and cholinergic nerves. Hearts were also stained for acetylcholinesterase to identify epicardial cholinergic nerves. In vivo electrophysiological studies were performed in another 10 dogs before and after LOM ablation. The anatomical examination revealed that the LOM is innervated by a branch of the left vagus. Immunohistochemistry confirmed that these nerve bundles are predominantly cholinergic (cholinergic-to-adrenergic ratio of 12.6 +/- 3.9:1). Cholinergic nerves originating in the LOM were found to innervate surrounding left atrial structures, including the pulmonary veins, left atrial appendage, coronary sinus, and posterior left atrial fat pad. Ablation of the LOM significantly attenuated effective refractory period shortening at distant sites, such as pulmonary veins and left atrial appendage, in response to vagal stimulation (vagal-induced ERP decrease in the left atrium: baseline vs. postablation = 17 vs. 4%; P = 0.0056). In conclusion, the LOM contains a predominance of cholinergic nerve fibers. Cholinergic fibers arising from the LOM innervate surrounding structures and contribute to the electrophysiological profile of the left atrium. These findings may provide a basis for the role of the LOM in the genesis and maintenance of atrial fibrillation.

Marshall vein as arrhythmogenic source in patients with atrial fibrillation: correlation between its anatomy and electrophysiological findings

BACKGROUND

Atrial fibrillation (AF) may originate from catecholamine-sensitive vein of Marshall (VOM) or its ligament in addition to pulmonary veins (PVs). The anatomy of VOM and its relation to arrhythmogenic foci in the left atrium are unknown. We studied the anatomy of VOM and its relation to foci in patients with AF.

METHODS

The study population consisted of 100 patients with AF (mean age, 62 years; chronic AF, n = 15). AF sources were determined at baseline and after isoproterenol administration without sedation. VOM was identified by balloon-occluded coronary sinus (CS) angiography. We determined its anatomy in relation to left PVs.

RESULTS

VOM was visualized in 73 patients (73%). Ninety-seven patients had 269 arrhythmogenic foci (PV, n = 77; non-PV, n = 48). Non-PV foci included left atrial posterior wall (24, 9%), left lateral area (12, 4.5%), roof (6, 2.2%), superior vena cava (28, 10.4%), crista terminalis (8, 3.0%), CS (10, 3.7%), and others (10, 3.7%). The incidence of PV foci in the left superior PV (LSPV) was significantly higher in patients with well-developed VOM than in those without (66% vs 42%, P < 0.05). Twenty-eight patients had 30 non-PV foci around the LSPV ostium. We successfully ablated the non-PV foci at the distal end of VOM in 11 patients. The ends of the VOM branches were good markers to search for non-PV foci. Seven of 11 (64%) patients with successful ablation of non-PV foci were free from arrhythmia, whereas only 6 of 17 (35%) were free from arrhythmia in those with residual non-PV foci.

CONCLUSIONS

To determine VOM anatomy is important to identify non-PV foci around the ends of VOM.

Is isolation of all four pulmonary veins necessary in patients with paroxysmal atrial fibrillation?

The upper pulmonary veins (PVs) are responsible for the majority of atrial fibrillation (AF) triggering foci, whereas the inferior PVs are more difficult to ablate and prone to postablation ostial stenosis. Most procedure failures can be attributed to incomplete isolation or recurrent PV left atrial reconnection rather than to identification of another focus. Furthermore, in certain patients AF triggers can be detected outside the PVs, and local denervation of the ganglionic plexus around the superior PV left atrial junctions following the ablation procedure may also play a role in eliminating AF. Based on these data, the authors propose that in AF patients the superior PVs should be ablated first, and in case of recurrence a second procedure should be performed for identification of PV left atrial reconnection or extrapulmonary foci and additional ablation of the inferior PVs. Such a staged approach might offer slightly lower success rates but with a significantly lower radiation exposure and procedural time and at a smaller risk of ablation induced PV stenosis.

Ablation of Superior Pulmonary Veins Compared to Ablation of All Four Pulmonary Veins:. A Randomized Clinical Trial

INTRODUCTION

Isolation of all pulmonary veins (PV) is advocated for treatment of paroxysmal atrial fibrillation (PAF). However, the superior PVs are responsible for most AF triggers, whereas the inferior PVs carry the higher risk for ablation-induced ostial stenosis. The aim of this study was to compare a superior PV isolation approach with isolation of all PVs for treatment of PAF.

METHODS AND RESULTS

Fifty-two patients with PAF were randomized to either left superior pulmonary vein (LSPV) isolation followed by additional isolation of the right superior pulmonary vein (RSPV) in case of AF recurrence (group A, n = 27) or isolation of all four PVs followed by a repeat procedure in case of recurrence (group B, n = 25). At 1-year follow-up, 11 patients (41%) in group A and 8 patients (32%) in group B had AF relapse (P = 0.55). No significant differences in AF relapse were detected between groups at 3 and 12 months (log rank = 0.36, P = 0.54) and by Cox proportional hazards model analysis (P = 0.62). Nonsignificant PV stenosis was detected in two patients from group B. Total radiofrequency energy delivery and fluoroscopy and procedure times were lower in group A: 8.9 +/- 1.4 minutes vs 25.6 +/- 3.7 minutes (P < 0.001), 22.2 +/- 6.8 minutes vs 62 +/- 10.3 minutes (P < 0.001), and 131.8 +/- 26.5 minutes vs 222.2 +/- 32.3 minutes (P < 0.001), respectively.

CONCLUSION

A staged superior PVs isolation approach confers equal success rates but with reduced radiofrequency energy delivery and fluoroscopy and procedure times compared to isolation of all PVs at the initial ablation attempt.

The coronary sinus: Passive bystander or source of arrhythmia?1 1ASSOCIATE EDITOR: D. GEORGE WYSE

The coronary sinus provides access to the epicardial space of the heart allowing ablation of epicardial accessory pathways, foci of ventricular arrhythmia, and arrhythmogenic areas such as the vein or ligament of Marshall. In addition, its musculature may form atrioventricular accessory connections, participate in macroreentrant atrial arrhythmias, and generate foci of microreentrant atrial tachycardia and fibrillation. Thus, the coronary sinus may serve both as a bystander to arrhythmia circuits as well as an original source of cardiac arrhythmia.

Catheter ablation therapy for atrial fibrillation

The past several years have witnessed a significant growth in the number of institutions offering catheter ablation for atrial fibrillation (AF). This growth has been a result of a better understanding of pathophysiology of AF and use of instruments and approaches that made catheter ablation of AF a safe and an effective alternative to the drug therapy. The procedure increasingly is becoming a therapy of choice for a select group of symptomatic, drug-refractory patients without structural heart disease, and it is being offered to a rapidly widening patient pool. This article reviews the procedural aspects and clinical evidence supporting this wider use of AF ablation. In addition, new techniques and technologies for AF ablation and new avenues of research in this area are explored.

Atrial tachycardia arising from an epicardial site with venous connection between the left superior pulmonary vein and superior vena cava

We describe a case of atrial tachycardia originating from an epicardial site with a venous connection between the left superior pulmonary vein (LSPV) and superior vena cava (SVC). Initial endocardial mapping with multiple electrodes catheters demonstrated early endocardial activation at both the SVC and LSPV. However, radiofrequency applications at the SVC failed to terminate the atrial tachycardia. With three-dimensional electroanatomic mapping, the earliest endocardial activation was found to be in the left atrial appendage (LAA). However, radiofrequency energy applications at multiple sites in the LAA resulted in only transient termination of the tachycardia. A left atrial angiogram demonstrated a venous connection between the LSPV and SVC, overlying the LAA. An application of radiofrequency energy with a saline-irrigated ablation catheter delivered at the earliest activation site in the LAA terminated the tachycardia. The tachycardia did not recur during 18-month follow-up.

Pulmonary vein ablation: role in preventing atrial fibrillation

Several investigators have identified the pulmonary vein as the most common initiator of atrial fibrillation, and isolation of the pulmonary vein from atrial tissue can cure approximately 70% of patients with paroxysmal atrial fibrillation. Ongoing trials of a new device may increase the success rate and decrease the complication rate during the pulmonary vein isolation procedure.