Pulmonary Vein-left Atrial Junction Research Articles

New Insights into Sinus Venosus Defects from Cross-Sectional Imaging

Sinus venosus defects include two varieties, superior and inferior sinus venosus defects. The superior sinus venosus defect is characterized by abnormal communication between two closely related venoatrial structures: 1) the normally positioned superior vena cava-right atrium complex and 2) the right pulmonary vein-left atrium complex that is displaced leftward, forward and upward. Inferior sinus venosus defects primarily involve the inferior vena cava-right atrial junction while the right pulmonary vein-left atrial junction can also be affected. Because of the rarity and wide variation of the defects, the morphological characterization of sinus venosus defects is inconsistent among investigators and often inaccurate. Modern imaging technologies with high spatial and temporal resolutions have allowed accurate and detailed assessment of the pathological anatomy in larger numbers of cases. In this pictorial essay, we revisit the established and controversial features of the sinus venous defects using two-dimensional (2D) and three-dimensional (3D) images obtained by magnetic resonance (MR) or computed tomography (CT) with brief discussion on imaging and treatment strategies.

P1166High-resolution mapping using smaller electrodes with closer interelectrode spacing to define pulmonary vein-left atrial junction electrograms characteristics

P1166High-resolution mapping using smaller electrodes with closer interelectrode spacing to define pulmonary vein-left atrial junction electrograms characteristics

Evolution of Force Sensing Technologies

In order to improve the procedural success and long-term outcomes of catheter ablation techniques for atrial fibrillation (AF), an important unfulfilled requirement is to create durable electrophysiologically complete lesions. Measurement of contact force (CF) between the catheter tip and the target tissue can guide physicians to optimise both mapping and ablation procedures. Contact force can affect lesion size and clinical outcomes following catheter ablation of AF. Force sensing technologies have matured since their advent several years ago, and now allow the direct measurement of CF between the catheter tip and the target myocardium in real time. In order to obtain complete durable lesions, catheter tip spatial stability and stable contact force are important. Suboptimal energy delivery, lesion density/contiguity and/or excessive wall thickness of the pulmonary vein-left atrial (PV-LA) junction may result in conduction recovery at these sites. Lesion assessment tools may help predict and localise electrical weak points resulting in conduction recovery during and after ablation. There is increasing clinical evidence to show that optimal use of CF sensing during ablation can reduce acute PV re-conduction, although prospective randomised studies are desirable to confirm long-term favourable clinical outcomes. In combination with optimised lesion assessment tools, contact force sensing technology has the potential to become the standard of care for all patients undergoing AF catheter ablation.

Evolution of Force Sensing Technologies.

In order to Improve the procedural success and long-term outcomes of catheter ablation techniques for atrial fibrillation (AF), an Important unfulfilled requirement is to create durable electrophysiologically complete lesions. Measurement of contact force (CF) between the catheter tip and the target tissue can guide physicians to optimise both mapping and ablation procedures. Contact force can affect lesion size and clinical outcomes following catheter ablation of AF. Force sensing technologies have matured since their advent several years ago, and now allow the direct measurement of CF between the catheter tip and the target myocardium in real time. In order to obtain complete durable lesions, catheter tip spatial stability and stable contact force are important. Suboptimal energy delivery, lesion density/contiguity and/or excessive wall thickness of the pulmonary vein-left atrial (PV-LA) junction may result in conduction recovery at these sites. Lesion assessment tools may help predict and localise electrical weak points resulting in conduction recovery during and after ablation. There is increasing clinical evidence to show that optimal use of CF sensing during ablation can reduce acute PV re-conduction, although prospective randomised studies are desirable to confirm long-term favourable clinical outcomes. In combination with optimised lesion assessment tools, contact force sensing technology has the potential to become the standard of care for all patients undergoing AF catheter ablation.

High-rate pacing-induced atrial fibrillation effectively reveals properties of spontaneously occurring paroxysmal atrial fibrillation in humans

Research on paroxysmal atrial fibrillation (AF) assumes that fibrillation induced by rapid pacing adequately reproduces spontaneously occurring paroxysmal AF in humans. We aimed to compare the spectral properties of spontaneous vs. induced AF episodes in paroxysmal AF patients. Eighty-five paroxysmal AF patients arriving in sinus rhythm to the electrophysiology laboratory were evaluated prior to ablation. Atrial fibrillation was induced by rapid pacing from the pulmonary vein-left atrial junctions (PV-LAJ), the coronary sinus (CS), or the high right atrium (HRA). Simultaneous recordings were obtained using multipolar catheters. Off-line power spectral analysis of 5 s bipolar electrograms was used to determine dominant frequency (DF) at recording sites with regularity index >0.2. Sixty-eight episodes were analysed for DF. Comparisons were made between spontaneous (n = 23) and induced (n = 45) AF episodes at each recording site. No significant differences were observed between spontaneous and induced AF episodes in HRA (5.18 ± 0.69 vs. 5.06 ± 0.91 Hz; P = 0.64), CS (5.27 ± 0.69 vs. 5.36 ± 0.76 Hz; P = 0.69), or LA (5.72 ± 0.88 vs. 5.64 ± 0.75 Hz; P = 0.7) regardless of pacing site. Consistent with these results, paired analysis in seven patients with both spontaneous and induced AF episodes, showed no regional DFs differences. Moreover, a left-to-right DF gradient was also present in both spontaneous (PV-LAJ 5.71 ± 0.81 vs. HRA 5.18 ± 0.69 Hz; P = 0.005) and induced (PV-LAJ 5.62 ± 0.72 vs. HRA 5.07 ± 0.91 Hz; P = 0.002) AF episodes, with no differences between them (P = not specific). In patients with paroxysmal AF, high-rate pacing-induced AF adequately mimics spontaneously initiated AF, regardless of induction site.

High-density epicardial mapping of the pulmonary vein–left atrial junction in humans: Insights into mechanisms of pulmonary vein arrhythmogenesis

The pulmonary veins (PVs) and the PV-LA (left atrium) junction are established sources of triggers initiating atrial fibrillation. In addition, they have been implicated in the maintenance of arrhythmia. To undertake high-density electrophysiological characterization of the right superior PV-LA junction in humans. Mapping was performed in 18 patients without a history of atrial fibrillation undergoing cardiac surgery. A high-density epicardial plaque was positioned at the anterior right superior pulmonary vein covering 3 regions: LA, PV-LA junction, and the PV. Isochronal maps were created during (1) sinus rhythm (SR); (2) LA pacing (LA-Pace); (3) PV pacing (PV-Pace); (4) LA programmed electrical stimulation (LA-PES); and (5) PV programmed electrical stimulation (PV-PES). Regional differences in conduction slowing/conduction block (CS/CB) and the prevalence of fractionated signals (FS) and double potentials (DPs) were assessed. A region of isochronal crowding representing CS/CB developed at the PV-LA junction in 84% of the maps. Three distinct activation patterns were seen. Pattern 1: Uniform SR activation without CS/CB. LA-Pace and PES caused 1 to 2 lines of isochronal crowding (CS/CB) at the PV-LA junction. Pattern 2: CS/CB occurred at the PV-LA junction in SR. LA/PV-Pace and LA/PV-PES caused an increase in CS/CB at the PV-LA junction with widely split DPs and FS. Pattern 3: A single incomplete line of CS at the PV-LA junction in SR. With LA/PV pacing and LA/PV-PES, multiple lines (≥3) of CS/CB developed at the PV-LA junction with evidence of circuitous activation and a marked increase in DPs and FS. High-density epicardial mapping of the right superior pulmonary vein demonstrates marked functional conduction delay and circuitous activation patterns at the PV-LA junction, creating the substrate for reentry.

A Spatial Gradient in IK1 Density Across the Pulmonary Vein-left Atrial Junction Attracts Atrial Fibrillation (AF) Drivers to the Pulmonary Veins

Background: The mechanisms underlying the maintenance of paroxysmal AF by high frequency rotors near or at the pulmonary veins (PVs) are not clear. As IK1 plays a major role in rotor dynamics we surmise that heterogeneous IK1 distribution, with lower density in the PVs than in the left atrium (LA), is also a major ionic mechanism for preferential localization of rotors in the PVs.

Noninvasive stereotactic radiosurgery (CyberHeart) for creation of ablation lesions in the atrium

A variety of catheter-based energy modalities are used for cardiac ablation to treat arrhythmias. Robotic radiosurgery is increasingly being utilized to successfully accomplish precise tissue ablation in anatomically remote areas. The purpose of this study was to examine the experimental feasibility of a noninvasive method using stereotactic robotic radiosurgery (SRS) to create cardiac lesions. Sixteen (16) Hanford-Sinclair mini swine (weight 40-70 kg) under general anesthesia were studied. Baseline computed tomographic scans were performed, followed by electroanatomic mapping using the CARTO system. Stereotactic robotic radiosurgery was performed using the CyberHeart system, with predetermined targets at the cavotricuspid isthmus, AV node, pulmonary vein-left atrial junction, or left atrial appendage. From 25 to 196 days after treatment, the animals were investigated with repeat electroanatomic voltage mapping and transesophageal echocardiography, when possible. The animals then were sacrificed and pathology specimens taken. Dose ranging suggested that 25 Gy was needed to produce an electrophysiologic effect. The time course showed an electrophysiologic effect consistently by 90 days. The method was feasible for producing bidirectional cavotricuspid isthmus block and AV nodal conduction block. The pulmonary vein-left atrial junction and left atrial appendage showed marked voltage reduction to less than 0.05 mV. No spontaneous arrhythmias were observed. Pathology specimens showed no evidence of radiation damage outside the target. Histology samples from target sites showed effects consistent with X-beam radiation. Stereotactic robotic radiosurgery can produce cavotricuspid isthmus block, AV nodal block, and significant decreased voltage at the pulmonary vein-left atrial junction. No other organ damage was seen. The study findings demonstrate the feasibility of this noninvasive treatment method for creating cardiac lesions. This approach merits further investigation in the treatment of arrhythmias.

Dominant frequency differences in atrial fibrillation patients with and without left ventricular systolic dysfunction

The aim of this study was to determine the mechanisms of atrial fibrillation (AF) in patients with left ventricular systolic dysfunction (LVSD). Dominant frequency (DF) spatiotemporal stability was studied in 15 patients with persistent AF (PEAF) and LVSD (Group I), 15 with PEAF without LVSD (Group II), and 10 with paroxysmal AF (PAAF) without LVSD (Group III). Dominant frequencies were analysed at 536 sites at baseline (DF1) and 26 +/- 12 min later (DF2). A DF1-DF2 difference of <or=0.5 Hz was found in 77, 70, and 48% of sites in Groups I, II, and III (P < 0.001). Maximal DF1 and DF2 were recorded at the same site in 12/15, 11/15, and 0/10 patients in Groups I, II, and III, respectively (P < 0.01). Gradient differences: Group I, DFs were higher at left atrium appendage (LAA) than at anterior (A) LA (ALA), pulmonary vein-left atrial junction (PV-LAJ), and posterior (P) LA (PLA) (7.4 +/- 1.1 vs. 6.6 +/- 1 vs. 6.8 +/- 0.8 vs. 6.8 +/- 0.7 Hz, P < 0.05); Group II, no differences; Group III, DF was higher at PV-LAJ than at LAA, AL, and PLA (6 +/- 1.2 vs. 5.3 +/- 1.1 vs. 5.2 +/- 0.9 vs. 5.4 +/- 1.1 Hz, P < 0.05). Dominant frequency stability supports stable arrhythmia sources as the mechanism of PEAF with (without) LVSD, but not of PAAF.

Atrial Fibrillation–Atrial Flutter Interactions

An appreciation of the article by Moreira et al in the current issue of Circulation 1 requires an understanding of the close interrelationship between atrial fibrillation (AF) and atrial flutter (AFL). These authors have understood this interrelationship and applied it to their data to advance the approach to both AF and AFL ablation. Key to this understanding is the recognition that cavotricuspid isthmus (CTI)–dependent AFL almost always develops from antecedent AF of variable duration.2–5 This is because in almost all instances, it is during the AF that a functional line of block (LoB) necessary for the development of AFL forms between the superior and inferior vena cavae. This LoB acts as a critical lateral boundary that prevents short-circuiting of the AFL reentrant circuit. Thus, in the vast majority of instances, without preceding AF, there can be no AFL. The most recent additional support of this concept comes from the report by Ellis et al,6 which found that of 363 patients who presented with only CTI-dependent AFL and who underwent CTI ablation, long-term follow-up (mean of 39±11 months) demonstrated newly recognized AF in 82%. It also should be noted that, as Moreira et al1 recognize, in some patients, a LoB between the vena cavae may be fixed (ie, anatomic) rather than functional. In such patients, AF may not be required for AFL to develop. Article p 2786 As Moreira et al1 further recognize, their report does not answer all the questions about the interrelationships of AF and AFL as they relate to AF ablation, …

Abstract 2246: Non-invasive ablation of the Left Superior Pulmonary Vein-Left Atrial junction using stereotactic focussed radiation

Introduction: High energy x-ray irradiation from a linear accelerator mounted on a robot arm has recently been used to produce ablation of cardiac tissue in swine. This device is currently used in patients for diverse indications requiring careful targeting, from tumors to trigeminal neuralgia. Purpose: This study was to determine if this method of energy delivery can be used to target potential arrhythmogenic sites such as the left superior pulmonary vein-left atrial junction. Method: Hanford-Sinclair mini-swine (40–70kg)(n=9) were studied under anesthesia. The animals underwent radiation (x-rays, 20 – 80 Gray) using a computer controlled robotic arm (Cyberknife) which focussed the x-ray beam on a preselected target. Targeting was done using either surgically implanted fiducials or fully non-invasively using a CT scan. A proprietary system was used to radiate the target while minimizing the dose to surrounding structures. Motion compensation was made for respiration during radiation, but no cardiac contractile motion compensation was made. The animals were then studied 4 – 8 weeks later with construction of cardiac voltage maps using CARTO (Biosense-Webster). Following this the animals were sacrificed and specimens taken for pathology. Results: All animals survived treatment. Radiation to the left superior pulmonary vein eliminated local electrograms with voltage less than 0.1mv. Pathology specimens showed histologic changes consistent with an area of discrete myocyte damage. There was no evidence of phrenic nerve injury. Limitations: This study was done in swine and human pulmonary vein response to this treatment is unknown. This model was arrhythmia free and the efficacy of this treatment for atrial fibrillation is unknown. Conclusions: Selective targeting of cardiac arrhythmogenic sites can be done using stereotactically focussed external radiation with respiratory motion compensation. The left superior pulmonary vein can be ablated without compensation for cardiac contractility.

Reentry and atrial fibrillation

The mechanisms of human atrial fibrillation (AF) are poorly understood. Experimental studies have demonstrated that cholinergic AF in the sheep heart is maintained by high-frequency reentrant sources (drivers) that result in a consistent left-to-right frequency gradient. More recently, clinical studies have confirmed the existence of a hierarchical organization in the rate of activation of different regions in the atria of patients with paroxysmal and chronic AF. Although maximal dominant-frequency sites were found to play a crucial role in the maintenance of AF in some patients, whether AF drivers in humans are focal or reentrant and whether changes in driver activity alter spatial frequency gradients are unclear. To test the hypothesis that localized functional reentry maintains AF in humans, we determined the effects of adenosine infusion on local dominant frequency at different sites of both atria. In patients with paroxysmal AF, adenosine infusion increases local dominant frequencies, particularly at the pulmonary vein-left atrial junction region, amplifying a left-to-right frequency gradient. In patients with chronic AF, dominant frequency is significantly higher than in patients with paroxysmal AF in all atrial regions surveyed, with the highest adenosine increase of frequencies outside the pulmonary vein region. Adenosine-induced driver acceleration is strongly suggestive of a reentrant mechanism in both groups of AF patients.

Arrangement of the Autonomic Nerves Around the Pulmonary Vein-Left Atrial Junctions —Histologic and Immunohistochemical Analyses—

Introduction: Imbalanced autonomic activity in the area of the pulmonary veins (PVs) can result in spontaneous atrial fibrillation (AF). Histologic characteristics of the PV sleeve musculature and associated autonomic nerve are not fully understood. We investigated the arrangement of autonomic nerve fibers around PV‐left atrium (LA) junctional musculature.Methods: Thirteen autopsied adult hearts (9 men and 4 women; mean age at death, 66.2 years were studied. The atria were removed from each heart, along with all PV stalks, and cut longitudinally to each PV myocardial sleeve. After treatment with azan‐Mallory stain and immunohistochemical staining for S‐100 and tyrosine hydroxylase (TH), autonomic nerve distribution was assessed by counting the numbers of TH‐positive (adrenergic and ‐negative (non‐adrenergic) fibers within S‐100‐positive fibers (&gt;50 mm in diameter) in the anterior, posterior, and septal junctions.Results: TH‐positive adrenergic fibers, consisting of sympathetic nerves, were most predominant in the anterior and septal junctions. In the anterior junction, these fibers were packed tightly among myocardial sleeve fascicles. In the posterior junction, the numbers of adrenergic and non‐adrenergic fibers were fewer. In the septal junction, the number of THnegative non‐adrenergic fibers (predominantly parasympathetic nerves) was greater, concomitant diffuse ganglionic nodule distribution in the interatrial fat pad.Conclusions: In each PV‐LA junction, autonomic nerves were localized on the anterior and septal walls. Heterogeneous distribution of TH‐positive and TH‐negative fibers and ganglion nodules around each PV opening appears to represent the major histologic characteristic in these areas.

Activation of Inward Rectifier Potassium Channels Accelerates Atrial Fibrillation in Humans

It is unclear whether atrial fibrillation (AF) drivers in humans are focal or reentrant. To test the hypothesis that functional reentry is involved in human AF maintenance, we determined the effects of adenosine infusion on local dominant frequency (DF) at different atrial sites. By increasing inward rectifier potassium channel conductance, adenosine would increase DF of reentrant drivers but decrease it in the case of a focal mechanism. Thirty-three patients were studied during AF (21 paroxysmal, 12 persistent) using recordings from each pulmonary vein-left atrial junction (PV-LAJ), high right atrium, and coronary sinus. DFs were determined during baseline and peak adenosine effect. In paroxysmal AF, adenosine increased maximal DF at each region compared with baseline (PV-LAJ, 8.03+/-2.2 versus 5.7+/-0.8; high right atrium, 7+/-2.2 versus 5.4+/-0.7; coronary sinus, 6.6+/-1.1 versus 5.3+/-0.7 Hz; P=0.001) and increased the left-to-right DF gradient (P=0.007). In contrast, in persistent AF, adenosine increased DF only in the high right atrium (8.33+/-1.1 versus 6.8+/-1.2 Hz; P=0.004). In 4 paroxysmal AF patients, real-time DF mapping of the left atrium identified the highest DF sites near the PV-LAJ, where adenosine induced an increase in DF (6.7+/-0.29 versus 4.96+/-0.26 Hz; P=0.008). Finally, simulations demonstrate that the frequency of reentrant drivers accelerates proportionally to the adenosine-modulated inward rectifier potassium current. Adenosine accelerates drivers and increases frequency differently in paroxysmal compared with persistent human AF. The results strongly suggest that AF is maintained by reentrant sources, most likely located at the PV-LAJ in paroxysmal AF, whereas non-PV locations are more likely in persistent AF.

Pulmonary Vein Edema in a Patient Undergoing Coronary Artery Bypass Graft Surgery and Concomitant Radiofrequency Ablation for Chronic Atrial Fibrillation

The syndrome of pulmonary vein stenosis characterized by pulmonary hypertension, dyspnea on exertion, and right heart failure, is a well-described complication of percutaneous ablation approaches, but has not been described with surgical approaches. We describe the case of a patient who developed localized edema at the pulmonary vein-left atrial junction after undergoing intraoperative radiofrequency ablation for chronic atrial fibrillation as part of CABG for severe triple vessel disease. The pulmonary vein edema resolved within 10 months suggesting that it may be a clinically silent and self-resolving phenomenon.

AB44-5: Safety and feasibility of left atrial imaging by placing an intracardiac echocardiographic catheter within the coronary sinus

When guiding radiofrequency ablation of AF, an intracardiac echocardiography (ICE) catheter positioned within the RA may not allow adequate visualization of critical LA structures. Placing the ICE catheter in the coronary sinus (CS) may allow for enhanced imaging of key LA structures, including the left atrial appendage (LAA) and pulmonary vein-left atrial (PV-LA) junction. The ability to successfully cannulate the CS and then image from this position was studied in a cohort of 100 consecutive patients referred for AF ablation.

Arrangement of the Autonomic Nerves Around the Pulmonary Vein-Left Atrial Junctions —Histologic and Immunohistochemical Analyses—

Introduction: Imbalanced autonomic activity in the area of the pulmonary veins (PVs) can result in spontaneous atrial fibrillation (AF). Histologic characteristics of the PV sleeve musculature and associated autonomic nerve are not fully understood. We investigated the arrangement of autonomic nerve fibers around PV-left atrium (LA) junctional musculature. Methods: Thirteen autopsied adult hearts (9 men and 4 women; mean age at death, 66.2 years were studied. The atria were removed from each heart, along with all PV stalks, and cut longitudinally to each PV myocardial sleeve. After treatment with azan-Mallory stain and immunohistochemical staining for S-100 and tyrosine hydroxylase (TH), autonomic nerve distribution was assessed by counting the numbers of TH-positive (adrenergic and -negative (non-adrenergic) fibers within S-100-positive fibers (>50 mm in diameter) in the anterior, posterior, and septal junctions. Results: TH-positive adrenergic fibers, consisting of sympathetic nerves, were most predominant in the anterior and septal junctions. In the anterior junction, these fibers were packed tightly among myocardial sleeve fascicles. In the posterior junction, the numbers of adrenergic and non-adrenergic fibers were fewer. In the septal junction, the number of THnegative non-adrenergic fibers (predominantly parasympathetic nerves) was greater, concomitant diffuse ganglionic nodule distribution in the interatrial fat pad. Conclusions: In each PV-LA junction, autonomic nerves were localized on the anterior and septal walls. Heterogeneous distribution of TH-positive and TH-negative fibers and ganglion nodules around each PV opening appears to represent the major histologic characteristic in these areas.

Lesion size and depth of tissue heating associated with microbubble formation during irrigated radiofrequency ablation

Introduction: Radiofrequency (RF) ablation at the pulmonary vein (PV)left atrial (LA) junction is effective in eliminating AF, but may be complicated by PV stenosis. Although theoretically less likely to cause PV stenosis, the impact of circumferential balloon cryo-ablation on PV patency has not been established. Methods: Therefore, PV integrity was assessed before, 4 1 weeks, and 16 2 weeks after circumferential ablation with a novel occlusive cryoballoon (CryoCath) in 15 PV (6 LS, 6 RS, 3 LI) in 6 dogs. Cryotherapy was delivered for 2-16 minutes at -80 to -62 degrees, with the intention of detecting the threshold for causing PV stenosis. CT scans were performed to assess PV diameter and to identify any focal narrowing and pathologic response was characterized at 16 weeks. Results: Six LSPVs, 3 LIPVs and 6 RSPVs were ablated with a duration of 6.3 5.0 minutes to temperatures of -71 7 C. The baseline, 4 week, and late PV diameters are as shown in Table. While there was no significant ( 50%) stenosis in these veins, two individual veins showed modest narrowing at 4 weeks with partial or total resolution at 16 weeks: RSPV with 31% early narrowing that resolved by 16 weeks, and an LSPV with 41% narrowing that reduced to 32% at 17 weeks. Thrombus developed in a branch of an LSPV during a 16 minute, under-sized balloon ablation, 10.2 mm into the branch. The mean ablation time for narrowed and nonnarrowed PVs at 16 weeks was 8.0 0.0 vs 6.8 5.4 minutes (p 0.48). The mean ablation temperature for narrowed and non-narrowed PVs was -74 0 and -72 7 (p 0.41.) Several veins showed dilatation upon long term follow-up. Conclusion: Cryo-therapy delivered via an occlusive balloon at the PV LA junction does not produce PV stenosis, although dilational remodeling may occur. This supports the safety of cryo-ablation, as a suitable alternative to RF ablation in the clinical setting.

Morphology of the Thoracic Veins and Left Atrium in Paroxysmal Atrial Fibrillation Initiated by Superior Caval Vein Ectopy

The structural changes of the superior caval vein, pulmonary veins, and left atrium in atrial fibrillation initiated by superior caval vein ectopy have not been reported. Nine patients with atrial fibrillation initiated by superior caval vein ectopic beats (male = 5, 54 +/- 10 years) and 15 control (n = 15, male = 10, 52 +/- 8 years) without any cardiac arrhythmias were included in this study. Using gadolinium-enhanced magnetic resonant angiography with three-dimensional reconstruction, the parameters of the superior caval vein morphology (length, various diameters, area, eccentricity, and volume) were measured. The morphological parameters of the four pulmonary veins (diameter, ostial area, and eccentricity) were also measured at the pulmonary vein-left atrial junction in an oblique sagittal section from the multiple-plane reconstruction images. The left atrial diameters and volume were measured. The different morphological parameters were compared between the two groups. The patients with atrial fibrillation initiated by superior caval vein ectopic beats exhibited a more eccentric structure of the second part of the superior caval vein as compared to the control group. All the ectopic beats initiating atrial fibrillation were located in the second part of the superior caval vein. Furthermore, the patients with atrial fibrillation initiated by superior caval vein ectopic beats had a larger superior caval vein volume, left atrial volume, and pulmonary vein size, and more eccentric pulmonary vein ostia than the controls. Structural changes of the superior caval vein were demonstrated in the patients with atrial fibrillation initiated by superior caval vein ectopic beats. These findings might explain the arrhythmogenic mechanism of atrial fibrillation initiated by superior caval vein ectopy.

Beating-heart epicardial radiofrequency ablation: optimal temperature setting

PurposePulmonary vein isolation is a simple procedure, which has recently been reported as an effective treatment for the termination of atrial fibrillation. Although there are several clinical reports of beating-heart epicardial ablation, the optimal temperature has not been experimentally investigated. We evaluated the effective temperature for the placement of circular lesions around the pulmonary vein–left atrial junction. DescriptionTwelve swine underwent epicardial ablation to create linear conduction block lesions around the pulmonary vein–left atrial junction by a seven-electrode ablation catheter. The ablation was performed at 60°C (group I), 70°C (group II), 80°C (group III), and 90°C (group IV) for 120 seconds. The creation of a firm conduction block across the ablated lesion under pacing was compared. EvaluationComplete conduction block was observed in all groups except group I. However, heat injury to adjacent structures in group IV and transient discoloration of the tissue surrounding coronary arteries in groups III and IV were observed. ConclusionsThe effective temperature for epicardial radiofrequency pulmonary vein isolation was 120 minutes and above 70°C.