Role of right middle pulmonary vein in patients with paroxysmal atrial fibrillation

Silent cerebral ischemic lesions in ablation-naïve patients with non-valvular atrial fibrillation: Does the pulmonary vein anatomy matter?

BACKGROUND

Silent cerebral ischemic lesions (SCILs) detected by magnetic resonance imaging (MRI) can precede symptomatic stroke, the risk of which is increased five-fold in atrial fibrillation (AF) patients. In our study, we aimed to evaluate the initial incidence of SCILs in the population of patients referred for ablation due to symptomatic AF and to identify possible risk factors.

METHODS

A total of 110 patients, with a mean age (SD) of 59.9 (9.4) years, referred for ablation, were included in the study. In all patients, MRI was performed before the procedure to evaluate the incidence of SCILs in the ablation-naïve patients.

RESULTS

MRI revealed preexisting SCIL in 81/110 patients (73.6%). Notably, SCILs were found in all patients with CHA₂DS₂-VASc score ≥ 4. In univariable analysis, age (p < 0.001), CHA₂DS₂-VASc score (p = 0.001), hypertension (p = 0.01), and anticoagulation duration (p = 0.023) were identified as significant risk factors for SCILs, while the presence of anatomical variants of left-sided common pulmonary veins trunk (LCPV) had negative prognostic value (p = 0.026). Multivariable logistic regression analysis identified age (p < 0.001) as the risk factor of preexisting SCILs, whereas the presence of LCPV trunk was associated with significantly lower (p = 0.005) SCILs incidence.

CONCLUSIONS

Silent cerebral ischemic lesions detected in MRI are frequent in the population of patients with non-valvular AF. The incidence of SCILs is higher in patients with long history of arrhythmia and higher CHA₂DS₂-VASc score. The relationship between the anatomy of pulmonary veins and the incidence of SCILs needs further investigation.

Pulmonary Vein Morphology in Patients Undergoing Catheter Ablation of Atrial Fibrillation

PURPOSE

Variations in the anatomy of pulmonary veins can influence selection of approaches of atrial fibrillation catheter ablation. Therefore, preprocedural evaluation and knowledge of pulmonary veins anatomy is crucial for proper mapping and the successful ablation of atrial fibrillation. The aim of this observational study was to assess CT angiography scans and perform detailed analysis of pulmonary veins morphology in patients scheduled for catheter ablation of atrial fibrillation.

METHODS

CT angiography was performed in 771 individuals (223 females, 548 males, mean age 58.4 ± 10.7 years). Pulmonary veins anatomy was evaluated using 3D models. The patterns used for evaluation included typical anatomy with four separate pulmonary veins, a common left ostium, and various types of accessory veins either alone or in combination with common left ostia.

RESULTS

An anatomical variant with common left ostium was observed as the most prevalent anatomy (44%). The typical variant was observed in 34.8% of patients. Accessory pulmonary veins were observed predominantly on the right side. The prevalence of anatomical variants did not differ between sexes with the exception of the unclassifiable category U (4.4% vs. 9%, p < 0.05).

CONCLUSIONS

Our study shows that a considerable number of atypical anatomies is present in patients undergoing AF catheter ablation. This knowledge may influence the choice of instrumentation. The data could be possibly helpful also in development of new ablation techniques.

Research on the Internal Flow Field of Left Atrial Appendage and Stroke Risk Assessment with Different Blood Models

Extant clinical research has underscored that patients suffering from atrial fibrillation (AF) bear an elevated risk for stroke, predominantly driven by the formation of thrombus in the left atrial appendage (LAA). As such, accurately identifying those at an increased risk of thrombosis becomes paramount to facilitate timely and effective treatment. This study was designed to shed light on the mechanisms underlying thrombus formation in the LAA by employing three-dimensional (3D) left atrium (LA) models of AF patients, which were constructed based on Computed Tomography (CT) imaging. The distinct benefits of Computational Fluid Dynamics (CFD) were leveraged to simulate the blood flow field within the LA, using three distinct blood flow models, both under AF and sinus rhythm (SR) conditions. The potential risk of thrombus formation was evaluated by analyzing the Relative Residence Time (RRT) and Endothelial Cell Activation Potential (ECAP) values. The results gleaned from this study affirm that all three blood flow models align with extant clinical guidelines, thereby enabling an effective prediction of thrombosis risk. However, noteworthy differences emerged when comparing the intricacies of the flow field and thrombosis risk across the three models. The single-phase non-Newtonian blood flow model resulted in comparatively lower residence times for blood within the LA and lower values for the Oscillatory Shear Index (OSI), RRT, and ECAP within the LAA. These findings suggest a reduced thrombosis risk. Conversely, the two-phase non-Newtonian blood flow model exhibited a higher residence time for blood and elevated RRT value within the LAA, suggesting an increased risk for thrombosis.

State of the art paper: Cardiac computed tomography of the left atrium in atrial fibrillation

The clinical spectrum of atrial fibrillation means that a patient-individualized approach is required to ensure optimal treatment. Cardiac computed tomography can accurately delineate atrial structure and function and could contribute to a personalized care pathway for atrial fibrillation patients. The imaging modality offers excellent spatial resolution and has been utilised in pre-, peri- and post-procedural care for patients with atrial fibrillation. Advances in temporal resolution, acquisition times and analysis techniques suggest potential expanding roles for cardiac computed tomography in the future management of patients with atrial fibrillation. The aim of the current review is to discuss the use of cardiac computed tomography in atrial fibrillation in pre-, peri- and post-procedural settings. Potential future applications of cardiac computed tomography including atrial wall thickness assessment and epicardial fat volume quantification are discussed together with emerging analysis techniques including computational modelling and machine learning with attention paid to how these developments may contribute to a personalized approach to atrial fibrillation management.

Numerical study of the risk of thrombosis in the left atrial appendage of chicken wing shape in atrial fibrillation

Atrial fibrillation (AF) is a common and life-threatening disease. For the patients with AF, more than 90% of the thrombi are formed in the left atrial appendage (LAA), thrombus dislodgement can cause vascular embolism, making them is becoming a high-risk group for stroke. Therefore, identifying the patients with high risk of thrombosis is crucial for advanced stroke warning. To better investigate the mechanism behind thrombus formation in the LAA, this study reconstructed the 3-D Left Atrium (LA) models of six AF volunteer patients by corresponding Computed Tomography (CT) images. Combine the advantages of Computational Fluid Dynamics (CFD), the blood flow field in LA both in AF and sinus heart rate states were studied. The risk of thrombus was evaluated based on the blood viscosity, shear rate thrombus prediction model and Time Average Wall Shear Stress (TAWSS), Oscillatory Shear Index (OSI), and Relative Residence Time (RRT) values. The results showed that the left atrium had lower blood flow velocity and TAWSS values at the LAA in both AF and sinus rhythm, thus the LAA is the most thrombogenic region in the LA. Besides, the RRT value of LAA was generally higher in AF than in sinus rhythm. Therefore, AF carries a higher risk of thrombosis.

Is there an association between left atrial outpouching structures and recurrence of atrial fibrillation after catheter ablation?

Objective

The aim of this study was to investigate the impact of left atrial diverticula (LADs), left sided septal pouches (LSSPs) and middle right pulmonary veins (MRPVs) on recurrent atrial fibrillation (rAF) in patients undergoing laser pulmonary vein isolation procedure (PVI).

Material and methods

This retrospective study enrolled 139 patients with pre-procedural multiple detector computed tomography (MDCT) imaging and 12 months follow-up examination. LADs, LSSPs and MRPV were identified by two radiologists on a dedicated workstation using multiplanar reconstructions and volume rendering technique. Univariate and bivariate regression analyses with patient demographics and cardiovascular risk factors as covariates were performed to reveal independent factors associated with rAF.

Results

LADs were recorded in 41 patients (29%), LSSPs in 20 (14%) and MRPVs in 15 (11%). The right anterosuperior wall of the left atrium was the most prevalent location of LADs (68%). rAF occured in 20 patients, thereof, 15 exhibited an outpouching structure of the left atrium (LAD: 9, LSSP: 2 and MRPV: 3). Presence of an LAD (HR: 2.7, 95%CI: 1.0–8.4, p = 0.04) and permanent AF (HR: 4.8, 95%CI: 1.5–16.3, p = 0.01) were independently associated with rAF.

Conclusions

LAD, LSSP and MRPV were common findings on pre-procedural cardiac computed tomography. LADs were revealed as potential independent risk factor of rAF, which might be considered for treatment planning and post-treatment observation.

Catheter ablation of atrial fibrillation: cardiac imaging guidance as an adjunct to the electrophysiological guided approach

Catheter ablation is increasingly utilized to treat patients with atrial fibrillation (AF). Despite progress in technology and procedural strategy, there remain significant limitations with suboptimal outcomes. The role of imaging has continued to evolve, and multimodality imaging now presents an important opportunity to make substantial progress in the safety and efficacy of ablation. In this review, we discuss the history of imaging in the ablation of AF with a specific focus on the ability of cardiac computed tomography and magnetic resonance imaging to characterize anatomy, arrhythmogenic substrate, and guide ablation strategy. We will review the progress that has been made and highlight many of the limitations as well as future directions for the field.

High anatomical accuracy of a novel high-resolution wide-band dielectric imaging system in cryoballoon-based ablation

PURPOSE

Recently, a novel cardiac imaging system based on a wide-band dielectric technology (KODEX-EPD) was introduced to guide catheter ablation. The aim of the study was to evaluate this 3D wide-band dielectric imaging system (WDIS) during cryoballoon (CB)-based atrial fibrillation (AF) ablation focusing on accuracy of pulmonary vein (PV)-anatomy.

METHODS

In consecutive patients with symptomatic AF, CB-based ablation was performed in conjunction with the 3D WDIS. Selective PV-angiographies were performed, and 3D anatomy of the left atrium (LA) and PVs using the 3D WDIS was created. The ostial diameters of the ipsilateral right-sided and left-sided PVs and ostial diameters of the right-/left-sided upper/lower PVs demonstrated by selective angiographies were analyzed and compared to 3D WDIS-based PV visualization.

RESULTS

In 65 patients (42/65 (65%) male, age 65 ± 9 years, 29/65 (45%) paroxysmal AF) a total of 260 PVs were identified. Median ostial PV-diameters for the ipsilateral left- and right-sided PVs were 38 [34; 43] and 37 [34; 40.3] mm when assessed fluoroscopically and 40 [35.7; 43] and 39 [35.0; 43] mm as demonstrated by 3D WDIS. There was no statistically significant difference between both methods regarding PV-diameter measurements. KODEX-EPD overestimated fluoroscopy measurements by 1.08 mm (95% limits of agreement of -1.93 mm and 4.1 mm).

CONCLUSION

The novel wide-band dielectric 3D-imaging system is feasible to create high-resolution images of cardiac structures during CB ablation procedures and accurately visualizes PV-anatomy.

Cryoballoon ablation of atrial fibrillation in patients with atypical right pulmonary vein anatomy

BACKGROUND

Cryoballoon ablation is widely used for pulmonary vein isolation in patients with atrial fibrillation. There are no data regarding the clinical efficacy of cryoballoon ablation in patients with atypical right pulmonary vein anatomy.

AIM

We aimed to evaluate the impact of right pulmonary vein anatomy on the safety and efficacy of cryoballoon ablation.

METHODS

Patients referred for cryoballoon ablation of paroxysmal atrial fibrillation were enrolled prospectively. Left atrial computed tomography was performed before cryoballoon ablation to determine whether the right pulmonary vein anatomy was "normal" or "atypical". For patients with atypical anatomy, cryoballoon ablation was only performed for right superior and right inferior pulmonary veins, neglecting accessory pulmonary veins.

RESULTS

Overall, 303 patients were included: 254 (83.8%) with normal and 49 (16.2%) with atypical right pulmonary vein anatomy. First-freeze isolation for right superior and right inferior pulmonary veins occurred in 44 (89.8%) and 37 (75.5%) patients with atypical pulmonary vein anatomy, and in 218 (85.8%) and 217 (85.4%) patients with typical pulmonary vein anatomy, respectively (P not significant). Phrenic nerve palsies were only observed in patients with normal anatomy (0 vs. 26 [8.6%]; P=0.039). Mid-term survival free from atrial arrhythmia was similar, regardless of right pulmonary vein anatomy.

CONCLUSIONS

A significant proportion of patients have atypical right pulmonary vein anatomy. Procedural characteristics, acute pulmonary vein isolation success and mid-term procedural efficacy were similar, regardless of right pulmonary vein anatomy. In addition to left-side pulmonary vein isolation, cryoballoon ablation of right superior and right inferior pulmonary veins only, neglecting accessory pulmonary veins, is sufficient to obtain acute right-side pulmonary vein isolation and mid-term sinus rhythm maintenance in patients with atypical anatomy.

A meta-analysis of the relationship between anatomical variations of pulmonary veins and atrial fibrillation

Background: Our aim was to provide an evidence-based assessment of the relationship between pulmonary vein variants and atrial fibrillation (AF).Methods: A comprehensive systematic search was performed on the databases PubMed, EMBASE, Cochrane library and Science Direct. Following assessment of eligibility and methodologic quality, data on PV variants were extracted and pooled into a meta-analysis.Results: A total of 12 studies (1337 cases and 1250 controls) were included. Presence of a right middle pulmonary vein was significantly associated with AF (OR = 1.85, 95% CI 1.26-2.72, p = .002). No significant association was however noted between presence of a common pulmonary vein ostia and AF. In the analysis of ostial diameters, the strongest association was observed between increased left common ostia diameter and AF (OR = 2.71, 95% CI 0.99-4.44, p = .002), followed by right superior (OR = 2.39, 95% CI 1.76-3.02, p < .00001), left superior (OR = 2.30, 95% CI 1.48-3.13, p < .00001), right inferior (OR = 2.19, 95% CI 1.69-2.69, p < .00001) and left inferior (OR = 1.79, 95% CI 1.25-2.34, p < .00001) pulmonary veins.Conclusion: The findings of the current study support the hypothesis that pulmonary vein variations predispose to AF. Further studies into the role of structural abnormalities of the pulmonary veins variations in the genesis of AF are recommended.

Pulmonary vein anatomy variants as a biomarker of atrial fibrillation - CT angiography evaluation

Background

It has been suggested that changes in pulmonary veins (PV) and left atrium (LA) anatomy may have an influence on initiating atrial fibrillation (AF) and the effectiveness of pulmonary vein isolation (PVI) in patients (pts) with atrial fibrillation.

The aim of the study was to assess anatomy abnormalities of the PV and LA in the patients with the history of AF and compare it with the control group(CG).

Methods

The multi-slice tomography (MSCT) scans were performed in 224 AF pts. before PVI (129 males, mean age 59 ± 9 yrs). The CG consisted of 40 pts. without AF (26 males, age 45 ± 9 yrs). LA and PV anatomy were evaluated. Diameters of PV ostia were measured in two directions: anterior-posterior (AP) and superior-inferior (SI) automatically using Vitrea 4.0.

Results

Pulmonary veins anatomy variants were observed more frequently in the atrial fibrillation group - 83 pts. (37%) vs 6 pts. (15%) in CG; 9% (21 pts) left common ostia (CO), 2% (5 pts) right CO, 19% (42 pts) additional right PV (APV), (1.8%) 4 pts. APV left, 8% right early branching (EB) and 3.5% left EB. The LA diameter differed significantly in AF vs CG group (41.2 ± 6 mm vs 35 ± 4.2 mm, p < 0.0001) respectively.

Conclusions

The anomalies of pulmonary vein anatomy occurred more often in pts. with AF. They can be defined as an image biomarkers of atrial fibrillation. Right additional (middle) pulmonary vein was the most important anomaly detected in AF patients as well as enlargered diameters of the LA and PV ostia.

Pulmonary venous abnormalities encountered on pre-radiofrequency ablation mapping multidetector computed tomography

Multidetector computed tomography (MDCT) elegantly renders pulmonary venous anatomy. With increasing numbers of radiofrequency ablation procedures being performed, there is now a greater emphasis on pre-procedure imaging to delineate this anatomy. Pulmonary venous mapping studies can be performed with or without ECG-gating. However, ECG-gating improves both the quality of 3D images and the accuracy of pulmonary vein (PV) ostial diameter measurements. Including the superior thorax, and not just the left atrium and central PVs, allows visualization of aberrant pulmonary venous drainage to the brachiocephalic veins or superior vena cava. Normally, there are two superior PVs, one right and one left, and two inferior PVs, one right and one left. The right superior vein usually drains the right upper and middle lobe. The left superior vein drains the left upper lobe including the lingula. The inferior veins drain their respective lower lobe. PV anatomy is more variable than pulmonary arterial anatomy, and developmental anomalies are common. This article describes, illustrates and reviews the common anomalies of the PVs in our experience performing over 1000-pre-radiofrequency ablation cardiac MDCT studies. The commonest anomalies are supernumerary or accessory veins (on the right) and a (left) common trunk. More rarely, partial anomalous pulmonary venous return and Cor triatriatum are seen, and rarest of all is total anomalous pulmonary venous return, PV varix and single or multiple vein stenosis or atresia.

Role of low kilovoltage electrocardiographic-gated multidetector CT in electrophysiological procedures in the paediatric age group

Treatment of arrhythmias by catheter ablation targeting the anatomical foci of arrhythmias by radiofrequency has evolved dramatically in recent years. A road map for the relevant heart structures is an important asset for the success of the procedure and should be obtained before the intervention. This can be achieved by intra-cardiac echocardiography, conventional angiographic methods, multidetector CT, or MRI. The electrophysiological technique comprises a diagnostic procedure and an interventional - therapeutic - procedure. Electrocardiographic-gated multidetector CT is important in the diagnostic session to evaluate the anatomical details in combination with electric activity mapping. This combined protocol provides a unique view of the propagation of electrical activity, either normal or abnormal, over cardiac structures and allows a precise functional and anatomical evaluation to be obtained. In this review, we evaluate the role of electrocardiographic-gated multidetector CT in roadmapping arrhythmias in the paediatric age group, focussing on its strengths; we also evaluated some additional aspects that need further improvement in the future.

Assessments of pulmonary vein and left atrial anatomical variants in atrial fibrillation patients for catheter ablation with cardiac CT

OBJECTIVES

To provide a road map of pulmonary vein (PV) and left atrial (LA) variants in patients with atrial fibrillation (AF) before catheter ablation procedure using cardiac CT.

METHODS

Cardiac CT was performed in 1420 subjects for accurate anatomical information, including 710 patients with AF and 710 matched controls without AF. PV variants, PV ostia and spatial orientation, LA enlargement, and left atrial diverticulum (LAD) were measured, respectively. Differences between these two groups were also respectively compared. Some risk factors for the occurrence of LAD were analyzed.

RESULTS

In total, PV variants were observed in 202 (28.5 %) patients with AF patients and 206 (29.0 %) controls without AF (p = 0.8153). The ostial sizes of all accessory veins were generally smaller than those of the typical four PVs (p = 0.0153 to 0.3958). There was a significant difference of LA enlargement between the AF and control groups (36.3 % vs. 12.5 %, p < 0.0001), while the prevalence of LAD was similar in these two groups (43.2 % vs. 41.9 %, p = 0.6293).

CONCLUSION

PV variants are common. Detailed knowledge of PVs and LA variants are helpful for providing anatomical road map to determine ablation strategy.

KEY POINTS

• PVs variants are helpful for providing anatomical road map to ablation. • PV variants are common. • DSCT could recognize these anatomic features before ablation as a non-invasive imaging.

Anatomical Basis for the Cardiac Interventional Electrophysiologist

The establishment of radiofrequency catheter ablation techniques as the mainstay in the treatment of tachycardia has renewed new interest in cardiac anatomy. The interventional arrhythmologist has drawn attention not only to the gross anatomic details of the heart but also to architectural and histological characteristics of various cardiac regions that are relevant to the development or recurrence of tachyarrhythmias and procedural related complications of catheter ablation. In this review, therefore, we discuss some anatomic landmarks commonly used in catheter ablations including the terminal crest, sinus node region, Koch's triangle, cavotricuspid isthmus, Eustachian ridge and valve, pulmonary venous orifices, venoatrial junctions, and ventricular outflow tracts. We also discuss the anatomical features of important structures in the vicinity of the atria and pulmonary veins, such as the esophagus and phrenic nerves. This paper provides basic anatomic information to improve understanding of the mapping and ablative procedures for cardiac interventional electrophysiologists.

Risk factors for atrial fibrillation recurrence: a literature review

Atrial fibrillation is the most common arrhythmia managed in clinical practice and it is associated with an increased risk of mortality, stroke and peripheral embolism. Unfortunately, the incidence of atrial fibrillation recurrence ranges from 40 to 50%, despite the attempts of electrical cardioversion and the administration of antiarrhythmic drugs. In this review, the literature data about predictors of atrial fibrillation recurrence are highlighted, with special regard to clinical, therapeutic, biochemical, ECG and echocardiographic parameters after electrical cardioversion and ablation. Identifying predictors of success in maintaining sinus rhythm after cardioversion or ablation may allow a better selection of patients to undergo these procedures. The aim is to reduce healthcare costs and avoid exposing patients to unnecessary procedures and related complications. Recurrent atrial fibrillation depends on a combination of several parameters and each patient should be individually assessed for such a risk of recurrence.

Variations in the pulmonary venous ostium in the left atrium and its clinical importance

INTRODUCTION

During early embryonic development, absorption of pulmonary venous network by the left primitive atrial chamber results in opening of four pulmonary veins which drain independently into its chamber. The extent of absorption and hence, the number of pulmonary veins which open into the left atrium, may vary. As only few studies have been done, which have shown such variations, the present study was done to evaluate the possible variations in the pulmonary veins which opened into the left atrium.

MATERIALS AND METHODS

Fifty formalin fixed adult cadaveric hearts were studied for variations in the opening of the pulmonary veins into left atrium.

RESULTS

Our results showed that 68% of the hearts which were studied, showed usual pattern of 2 pulmonary veins on either side, while remaining 32 % hearts showed variations in the number of pulmonary veins which opened. Twelve percent of the hearts showed 2 left and 3 right pulmonary veins, 14% of hearts showed 2 left and 1 right veins, 4% hearts showed 1 left and 2 right veins and 2% hearts showed 1 left and 4 right pulmonary veins opening into the left atrium.

CONCLUSION

Knowledge on such variations gains significance in isolation for radiofrequency ablation as a treatment for atrial fibrillation.

Triggers and anatomical substrates in the genesis and perpetuation of atrial fibrillation

The definition of atrial fibrillation (AF) as a functional electrical disorder does not reflect the significant underlying structural abnormalities. Atrial and Pulmonary Vein (PV) muscle sleeve microstructural remodeling is present, and establishes a vulnerable substrate for AF maintenance. In spite of an incomplete understanding of the anatomo-functional basis for AF, current evidence demonstrates that this arrhythmia usually requires a trigger for initiation and a vulnerable electrophysiological and/or anatomical substrate for maintenance. It is still unclear whether the trigger mechanisms include focal enhanced automaticity, triggered activity and/or micro re-entry from myocardial tissue. Initiation of AF can be favored by both parasympathetic and sympathetic stimulation, which also seem to play a role in maintaining AF. Finally, evolving clinical evidence demonstrates that inflammation is associated with new-onset and recurrent AF through a mechanism that possibly involves cellular degeneration, apoptosis, and subsequent atrial fibrosis.

Standardized review of atrial anatomy for cardiac electrophysiologists

Catheter ablation of cardiac arrhythmias has rapidly evolved from a highly experimental procedure to a standard form of therapy for various tachyarrhythmias. The advances in this field have included, first, the development of techniques of catheter ablation that often requires the precise destruction of minute amounts of arrhythmogenic tissues and, second, techniques of resynchronization therapy that require pacing different parts of the ventricles. A detailed prepocedural knowledge of cardiac anatomy can improve the safety of the procedure and its rate success. It helps the electrophysiologist to choose the appropiate region for ablation, shortening the procedural time. The atrial anatomy structures are usually localized before ablation by different imaging techniques such as fluoroscopy, electroanatomic mapping, intracardiac echocardiography or multidetector computed tomography. In this review, we describe the normal anatomy of the atria, highlighting the landmarks of interest to intervencional cardiologist, stressing their relationship to other structures. This article is part of a JCTR special issue on Cardiac Anatomy.

Role of Cardiac Imaging (CT/MR) Before and After RF Catheter Ablation in Patients with Atrial Fibrillation

Pre-procedure X-ray computed tomography (CT) and magnetic resonance imaging (MRI) angiography are commonly used to delineate the complex and variable relationship of the left atrium, pulmonary veins, and surrounding structures. 3D CT and MR angiography are routinely incorporated into electroanatomic mapping systems to guide ablation lesion placement in the context of patient specific anatomy. Post-procedure CT and MRI have also proven useful for evaluating complications such as pulmonary vein stenosis. In the future, these imaging modalities may be used to visualize more detailed tissue characteristics such as atrial fibrosis and ablation lesions. This could improve selection of patients for different treatment strategies and perhaps guide more effective ablation. This review will discuss current and emerging applications of CT and MRI before and after radiofrequency catheter ablation of atrial fibrillation.

2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design

This is a report of the Heart Rhythm Society (HRS) Task Force on Catheter and Surgical Ablation of Atrial Fibrillation, developed in partnership with the European Heart Rhythm Association (EHRA), a registered branch of the European Society of Cardiology and the European Cardiac Arrhythmia Society (ECAS), and in collaboration with the American College of Cardiology (ACC), American Heart Association (AHA), the Asia Pacific Heart Rhythm Society (APHRS), and the Society of Thoracic Surgeons (STS). This is endorsed by the governing bodies of the ACC Foundation, the AHA, the ECAS, the EHRA, the STS, the APHRS, and the HRS.

CT evaluation of pulmonary venous anatomy variation in patients undergoing catheter ablation for atrial fibrillation

To characterize pulmonary vein (PV) anatomy and the relative position of the PV ostia to the adjacent thoracic vertebral bodies, two readers reviewed 176 computed tomography pulmonary venous studies. PV ostial dimensions were measured and PV ovality assessed. Anatomical variations in PV drainage were noted. The position of the PV ostium relative to the nearest vertebral body edge was recorded. Right PV ostia were significantly more circular than the left (p<.001). Anatomical variability was greater for right PVs: 82% of patients had 2 ostia, 17% had 3 ostia, 0.5% had 4 ostia and 0.5% a common ostium. For left PVs, 91% of patients had 2 ostia, 8.5% a common ostium and 0.5% 3 ostia. Mean ostial distances from vertebral margin were: right PVs 3.62±7.48 mm; left PVs 3.84±8.46 mm (p=.72). 65% of right upper PV, 60.5% of right lower PV, 51% of left upper PV and 57% of left lower PV ostia were positioned lateral to vertebral bodies. Right PV ostia are rounder than left-sided and right PV drainage is more variable. As a significant proportion of PV ostia overlap the vertebral bodies, prior anatomical evaluation by CT can assist catheter ablation procedures for atrial fibrillation (AF), especially when performed under fluoroscopy.

Role of three-dimensional imaging integration in atrial fibrillation ablation

Atrial fibrillation is the most common arrhythmia and in symptomatic patients with a drug-refractory form, catheter ablation aimed at electrically disconnecting the pulmonary veins (PVs) has proved more effective than use of antiarrhythmic drugs in maintaining sinus rhythm during follow-up. On the other hand, this ablation procedure is complex, requires specific training and adequate clinical experience. A main challenge is represented by the need for accurate sequential positioning of the ablation catheter around each veno-atrial junction to deliver point-by-point radiofrequency energy applications in order to achieve complete and persistent electrical disconnection of the PVs. Imaging integration is a new technology that enables guidance during this procedure by showing a three-dimensional, pre-acquired computed tomography or magnetic resonance image and the relative real-time position of the ablation catheter on the screen of the electroanatomic system. Reports in the literature suggest that imaging integration provides accurate visual information with improvement in the procedure parameters and/or clinical outcomes of the procedure.

Developments and recent advances in catheter ablation of paroxysmal atrial fibrillation

The development of catheter ablation for paroxysmal atrial fibrillation (AF) has evolved rapidly over the last 10 years from an experimental unproven procedure to a commonly performed ablation therapy in many major hospitals. The pulmonary vein (PV) and left atrium were discovered to be critical in the initiation and perpetuation of AF. With a better understanding of the AF mechanisms and more experience from the ablation follow-up, we have seen the ablation technique change from PV focal ablation to empirical circumferential isolation of all four PVs. In addition, the technological aid obtained from 3D electroanatomic mapping systems has further improved the safety and long-term efficacy and minimized the procedural difficulty. Recently, the atrial substrate analysis of the high-frequency and fractionated electrograms has further afforded the improvement in the outcome of more complex arrhythmias. Therefore, in this article, we will review the recent evidence and advancements in the mechanisms of AF and catheter ablation, and highlight the unsolved issues regarding future perspectives for paroxysmal AF.

Computed tomography of pulmonary venous variants and anomalies

Radiofrequency ablation of the pulmonary veins is a well-established technique in the management of atrial fibrillation. Computed tomography (CT) plays an important role in the evaluation of these patients, especially delineating pulmonary venous anatomy, anatomic variations, and complications after radiofrequency ablation. CT scan is characterized by high spatial and temporal resolutions, multiplanar reconstruction capabilities, and wide field of view. Knowledge of the normal pulmonary venous anatomy, anatomic variants, and optimal scanning protocol is essential for preablation planning and for evaluation of postablation complications. In this pictorial review, the CT appearance of various pulmonary venous variants and anomalies are discussed and illustrated.

Transoesophageal echocardiographic evaluation of pulmonary vein anatomy in patients undergoing ostial radiofrequency catheter ablation for atrial fibrillation: a comparison with magnetic resonance angiography

OBJECTIVE

A detailed definition of pulmonary vein (PV) anatomy is of great importance in patients undergoing radiofrequency catheter ablation for atrial fibrillation. In fact, it is known that variations in the number and anatomy of the PV ostia are more frequent than thought. The aim of this study was to assess the usefulness of transoesophageal echocardiography (TOE) in defining the exact PV anatomy by comparing it with magnetic resonance angiography (MRA), which is proven to be very accurate.

METHODS

Forty-five consecutive patients (39 male, 6 female, mean age 50 + or - 6 years) affected by drug-refractory atrial fibrillation underwent radiofrequency catheter ablation. They were all studied with MRA and then with TOE in order to exclude intra-atrial thrombi and to assess PV anatomy.

RESULTS

TOE visualised the superior PVs in 100% of cases and the right and left inferior PVs in 98% and 94% of cases, respectively. Only 19 patients (42%) showed typical PV anatomy, with two left and two right distinct PV ostia. In 14 patients (31%), one or two intermediate right PVs and in 12 patients (27%) a common left trunk were detected. The concordance with MRA was high (95%).

CONCLUSIONS

TOE is accurate in assessing PV anatomy and in showing anatomic variations in the PV ostia compared with MRA. Anomalous pulmonary venous drainage is more frequent than expected. TOE can provide functional Doppler information, thus being particularly useful in the follow-up after radiofrequency catheter ablation.

The effect of the cryosurgical cox-maze procedure on pulmonary veins diameter and left atrial size: computed tomography angiographic assessment

OBJECTIVE

: The Cox-Maze procedure using cryoablation results in transmural lesions, which follow the lesion pattern of the cut-and-sew Cox-Maze procedure. The purpose of our study was to evaluate the effect of the Cox-Maze procedure on left atrial and pulmonary vein size using computed tomography angiogram (CTA). An additional aim was to evaluate pulmonary vein anatomic variability.

METHODS

: Six patients (four women and two men; ages 39-63 years, mean age 54.3) underwent chest CTA 1 day before and 38 to 104 days (mean 62.6 days) after the cryosurgical Cox-Maze procedure. Measurements of pulmonary vein ostia and left atrial cranio-caudal, left-to-right and anterior-posterior diameters were derived by consensus. The change in diameters after therapy was compared using the Wilcoxon nonparametric test for paired measurements. Four patients (1 woman and 3 men; age 57-73 years; mean age 59) were evaluated with postoperative CTA alone 296-530 days (mean 447) after surgery, for the development of postoperative pulmonary vein stenosis. A single patient underwent preoperative CTA, but surgery was not performed. Pulmonary venous anatomy was recorded in all 11 patients.

RESULTS

: Sinus rhythm was restored in all operated patients. No focal ostial stenosis of the pulmonary veins was observed. The quantitative assessment in the six patients with preoperative and postoperative studies disclosed only slight changes in pulmonary vein diameter with either reduction or dilatation of no more than 20% from baseline (P > 0.05). There was a consistent trend toward decrease in left atrial dimensions, which did not reach statistical significance. Six patients (55%) had standard pulmonary venous anatomy and five patients (45%) had at least one variation in their pulmonary vein anatomy.

CONCLUSIONS

: In this study, we found that a very intensive cryoablation protocol around the pulmonary veins did not result in pulmonary vein stenosis. In addition, a relatively high incidence of anatomic variations of the pulmonary veins was documented.

The role of computed tomography and magnetic resonance imaging in ablation procedures for treatment of atrial fibrillation

Cardiac ablation procedures have become the standard of therapy for various arrhythmias including atrial fibrillation. Understanding the morphological characteristics of the left atrium (LA) and pulmonary veins (PV) in detail and identification of its anatomic variants is crucial to perform a successful ablation procedure and minimize complications. The current techniques for radiofrequency ablation of atrial fibrillation include targeting the PVs or the tissue in the antrum of the LA. Localization of the anatomic structures within the LA is performed by using fluoroscopy, electroanatomic mapping, and intracardiac echocardiography. Multidimentional computed tomography and magnetic resonance angiography are invaluable techniques for better visualization of the anatomic landmarks that are essential for cardiac ablation procedures as well as prompt diagnosis and, in selected cases, prevention of procedure-related complications. Some of the complications of ablation procedures may include cardiac tamponade, PV stenosis, as well as esophageal and phrenic nerve injuries.

Role of multidetector computed tomography in the anatomical definition of the left atrium-pulmonary vein complex in patients with atrial fibrillation. Personal experience and pictorial assay

PURPOSE

This study aimed to illustrate the typical anatomical pattern and anatomical variants of the left atrium-pulmonary vein (LA-PV) complex studied by 16-slice multidetector computed tomography (MDCT) in a population of patients with atrial fibrillation (AF) undergoing percutaneous transcatheter left atrial ablation. Accurate knowledge of this anatomical region is fundamental for increasing the efficiency, efficacy and accuracy of the procedure and for reducing the risk of complications.

MATERIALS AND METHODS

From January 2004 to March 2007, we studied 75 patients (57 men, 18 women) affected by paroxysmal and chronic AF by using MDCT. In 63 patients, the MDCT examination was performed using retrospective cardiac electrocardiographic (ECG) gating and dose modulation, with reconstructions performed at 75% of R-R interval. In the remaining 12 patients, ECG gating was not possible due to high-frequency AF.

RESULTS

We identified 286 PV: 157 right and 129 left. On the right side, eight PV were supernumerary and one was a common trunk, whereas on the left side, we found 22 common trunks and one supernumerary vein. In 61.3% of patients, the anatomical pattern was typical (two right and two left PV). In the remaining 38.7%, it was atypical [two right PV-left common trunk (26.6%); three right PV-two left PV (6.7%); three right PV-left common trunk (2.6%); three right PV-three left PV (1.3%); right common trunk-two left PV (1.3%)]. MDCT identified branching of the right inferior PV in 94.5%, of the right superior PV in 75.6%, of the left superior PV in 7.5% and of the left inferior PV in 7.5%; 3/8 of the right supernumerary veins presented branching. With respect to the left PV ostia, the position of the orifice of the 74 recognised appendages was high in 85.1%, intermediate in 12.1% and low in 2.8%. There was no association between PV anatomical variants and clinical presentation of AF (paroxysmal or chronic).

CONCLUSIONS

MDCT represents a fundamental diagnostic imaging tool in the anatomical definition of the LA-PV complex, which is characterised by considerable variability. Radiologists must be familiar with the anatomical variants and help the referring interventional electrophysiologist understand their importance.

Prevalence and characterization of pulmonary vein variants in patients with atrial fibrillation determined using 3-dimensional computed tomography

Although several branching patterns of pulmonary veins (PVs) were reported, their prevalence and characterization were not sufficiently clarified. Multislice computed tomography was performed in 428 patients who underwent catheter ablation for drug-refractory atrial fibrillation. Size and branching pattern of PVs were analyzed. A typical pattern of 4 PVs with 4 separate ostia was found in 326 patients (76%). However, a common PV trunk, defined as a PV with coalescence of superior and inferior PVs > or =1.5 cm proximal to the junction with the left atrium, was found on the left side in 34 patients (8%) and right side in 3 patients (0.76%). A discrete middle PV was found on the right side in 54 patients (13%) and left side in 9 patients (2%). A right top PV, defined as an anomalous insertion of a branch of the right superior PV into the left atrial body, was also found in 16 patients (4%). In conclusion, 24% of our patients with atrial fibrillation had PV anomalies and 3% had coexistence of 2 PV variants, indicating that PV variants are not rare.

Stretch-activated currents in cardiomyocytes isolated from rabbit pulmonary veins

Evidence is growing of a relationship between atrial dilation and atrial fibrillation (AF), the most prevalent type of arrhythmia. Pulmonary veins, which are important ectopic foci for provoking AF, are of increasing interest in relation to the early development of AF. Here, using single cardiomyocytes isolated from rabbit pulmonary veins, we characterised the stretch-activated currents induced by swelling and axial mechanical stretching. Swelling induced both a stretch-activated nonselective cationic current (NSC) and a Cl(-) current. The swelling-induced Cl(-) current (I Cl,swell) was inhibited by DIDS, whereas the swelling-induced NSC (I NSC,swell) was inhibited by Gd3+. The cationic selectivity of the I NSC,swell was K+ >Cs+ >Na+ >Li+, whilst the PK/PNa, PCs/PNa, and PLi/PNa permeability ratios were 2.84, 1.86, and 0.85, respectively. Activation of the I NSC,swell was faster than that of the I Cl,swell. Given a high K+ concentration in the bath solution, the I NSC,swell showed limited amplitude (<-70 mV). Mechanical stretching induced an immediate Gd3+- and streptomycin-sensitive NSC (I NSC,stretch) that was permeable to Na+, K+, Cs+ and NMDG. Persistent stretching activated a DIDS-sensitive current (I Cl,stretch). The I NSC,stretch, but not the I NSC,swell, was completely blocked by 400 microM streptomycin; therefore, the two currents may not be associated with the same channel. In addition, the type of current induced may depend on the type of stretching. Thus, stretch-induced anionic and cationic currents are functionally present in the cardiomyocytes of the main pulmonary veins of rabbits, and they may have pathophysiological roles in the development of AF under stretched conditions.