MDCT of the Left Atrium and Pulmonary Veins in Planning Radiofrequency Ablation for Atrial Fibrillation: A How-To Guide

Novel cryoballoon technology for atrial fibrillation ablation: Impact of pulmonary vein variant anatomy, cooling characteristics, and 1-year outcome from the CHARISMA registry

BACKGROUND

No data have been reported on cooling characteristics and the impact of variant pulmonary vein (PV) anatomy on atrial fibrillation (AF) recurrences after POLARx cryoballoon (CB) ablation.

OBJECTIVE

The purpose of this study was to analyze the impact of PV anatomy variants and cooling characteristics after CB ablation from a large multicenter prospective registry.

METHODS

The primary end point was defined as 1-year absence of any atrial tachyarrhythmias (ATAs: AF/atrial flutter/atrial tachycardia). Correlation between ATA recurrences and anatomy variants/cooling characteristics were evaluated. The secondary outcome was the rate of major periprocedural complications.

RESULTS

A total of 429 consecutive patients diagnosed with paroxysmal AF (83.4%) or persistent AF (peAF; 16.6%) were enrolled. Twenty-eight patients (6.6%) exhibited an anatomical variant (common ostium: 4.0%; adjunctive PV: 2.6%). Nadir temperature, thaw time, and total deflation time were different between standard PVs and PV variants. After the blanking period, over a mean of 431 ± 99 days of follow-up, 63 patients (14.7%) suffered an ATA recurrence. Patients with recurrences had both a shorter thaw time (18.5 ± 7 seconds vs 19.8 ± 7 seconds; P = .0012) and a shorter total deflation time, whereas time to isolation was longer (57.4 ± 42 seconds vs 49.1 ± 33 seconds; P = .04). Patients with anatomy variants showed a similar ATA recurrence rate (5 of 28 [17.9%]) to the standard anatomy group (58 of 401 [14.5%]) (P = .584), with a hazard ratio (HR) of 1.43 (95% confidence interval [CI] 0.49-4.13; log-rank, P = .4384). After adjusting for confounders, heart failure (HR 4.12; 95% CI 1.75-9.73; P = .0013) and peAF (HR 1.81; 95% CI 1.03-3.18; P = .0433) remained associated with ATA recurrence during follow-up.

CONCLUSION

The POLARx CB system demonstrated long-term efficacy, along with a safe profile, in both patients with paroxysmal AF and those with peAF, regardless of the presence PV variants. Time to isolation was longer in patients with ATA recurrences during follow-up.

CLINICAL TRIAL REGISTRATION

Catheter Ablation of Arrhythmias with a High-Density Mapping System in Real-World Practice (CHARISMA).

CLINICALTRIALS

gov identifier: NCT03793998. Registration date: January 4, 2019.

CAR and CSTR Cardiac Computed Tomography (CT) Practice Guidelines: Part 2-Non-Coronary Imaging

The cardiac computed tomography (CT) practice guidelines provide an updated review of the technological improvements since the publication of the first Canadian Association of Radiologists (CAR) cardiac CT practice guidelines in 2009. An overview of the current evidence supporting the use of cardiac CT in the most common clinical scenarios, standards of practice to optimize patient preparation and safety as well as image quality are described. Coronary CT angiography (CCTA) is the focus of Part I. In Part II, an overview of cardiac CT for non-coronary indications that include valvular and pericardial imaging, tumour and mass evaluation, pulmonary vein imaging, and imaging of congenital heart disease for diagnosis and treatment monitoring are discussed. The guidelines are intended to be relevant for community hospitals and large academic centres with established cardiac CT imaging programs.

Pulmonary Vein Remodeling Between Atrial Fibrillation Subtypes: A Matched Comparison Cardiac Computed Tomography-Based Study Between Patients With Paroxysmal and Persistent Atrial Fibrillation

Although pulmonary vein (PV) isolation (PVI) is the cornerstone for atrial fibrillation (AF) ablation, no data exist comparing PV anatomy between AF subtypes directly. We aimed to compare PV anatomic characteristics between paroxysmal (PAF) and persistent AF (PeAF) in a matched population using cardiac computed tomography (CCT). Fifty-eight PeAF patients (with CCT prior first AF ablation procedure, absence of valvular disease/previous cardiac intervention), and 58 age-, sex-, body surface area-matched PAF patients were evaluated for left atrial (LA) and PV anatomy: ostial area, ovality index (OVI), transverse/frontal angles. In PeAF vs PAF group, beside higher LA volume index (LAVI), PVs' ostial areas were significantly larger (between 64 - 101 mm2, P < 0.001 for all PVs; remaining valid after LAVI adjustment for left superior [LS], left inferior [LI], and right inferior [RI]PV); left PVs were less oval (0.7 - 0.11 OVI decrease, P =0.039 for LSPV; P = 0.012 for LIPV); LSPV (P = 0.019), LIPV (P < 0.001), RIPV (P = 0.029) were more posteriorly directed; whereas LSPV (P = 0.002), and right superior PV (P = 0.043) were more superiorly directed. Incidence of anatomic variations or early branching was not different. This study showed significant anatomical PV differences between patients with PeAF and PAF, in terms of PV orientation, ostial size and ovality. Anticipating such anatomical differences may aid in choosing the adequate catheter design and technology for PeAF ablation.

The role of CT in arrhythmia management-treatment planning and post-procedural imaging surveillance

Several interventional treatment options exist in patients with atrial and ventricular arrhythmia. Cardiac CT is routinely performed prior to occlusion of the left atrial appendage, pulmonary vein isolation, and cardiac device implantation. Besides the evaluation of coronary artery disease, cardiac CT provides isotropic, high-resolution CT images of the cardiac anatomy with the possibility of multiplanar reformations and three-dimensional reconstructions which are helpful to guide interventional treatment. In addition, cardiac CT is increasingly used to rapidly evaluate periprocedural complications and for the routine post-procedural imaging surveillance in patients after interventions. This review article will discuss current applications of pre- and post-interventional CT imaging in patients with arrhythmia.

[What the ablationist should know about pulmonary vein anatomy]

The importance of anatomy in daily clinical practice of the interventional electrophysiologist is crucial, especially for pulmonary vein isolation which is a predominantly anatomy-based approach. Many anatomical and morphological studies focusing on this topic were published in last two decades. In this article we are refreshing the knowledge of anatomy and morphology of the pulmonary veins and present them from a clinical perspective.

Cryoballoon Ablation for Persistent Atrial Fibrillation in a Patient with a Left Pneumonectomy

Pulmonary vein (PV) isolation (PVI) is the most important component of catheter ablation of atrial fibrillation (AF) and can be achieved by radiofrequency or cryoballoon ablation (CBA). The CBA system has shown excellent efficacy and safety in a number of clinical trials and is independent of the PV anatomy. However, pneumonectomy can significantly alter the anatomy posing a challenge to CBA. Few cases of PVI accomplished by CBA have been described in patients with lobectomy, but none in the pneumonectomy population. We describe a case of successful CBA for paroxysmal AF in a patient with a left total pneumonectomy.

Normal pulmonary venous anatomy and non-anomalous variations demonstrated on CT angiography: what the radiologist needs to know?

Variations in pulmonary venous anatomy (in the absence of any anomalous pulmonary venous connections) is not uncommon. Commonly occurring variations include presence of conjoined pulmonary veins (PV), supernumerary PVs and ostial PVs. Variant PV anatomy is often asymptomatic; however, it may assume importance in the pre-procedural planning prior to cardiothoracic surgeries and radiofrequency catheter-directed ablation for PV isolation. It is therefore important that the radiologist is aware of the conventional normal and variant PV anatomy in addition to obvious abnormalities like anomalous PV drainage or PV stenosis/ occlusion. Multidetector CT (MDCT) is often used as the first-line imaging modality for pre-procedural PV mapping as it provides high quality images with short acquisition times and availability of numerous post-processing tools.This pictorial review focusses on the MDCT-based PV imaging describing the reporting nomenclature, the conventional normal as well as non-anomalous variant PV anatomy along with their clinical significance.

Roles of Transesophageal Echocardiography and Cardiac Computed Tomography for Evaluation of Left Atrial Thrombus and Associated Pathology: A Review and Critical Analysis

Evaluation of the left atrium and left atrial appendage for the presence of thrombus prior to cardioversion and pulmonary vein isolation, and of the entire heart for embolic sources in the setting of cryptogenic stroke, has long been standard medical care. Guidelines have uniformly recommended transesophageal echocardiography (TEE) to accomplish these goals. In recent years, computed tomographic angiography has demonstrated diagnostic accuracy similar to that of TEE for the detection of thrombus. Analysis of the pertinent data and relative merits of the 2 technologies leads to the conclusions that: 1) both modalities have some unique, nonoverlapping capabilities that may dictate their use in specific situations; 2) computed tomographic angiography is a reasonable alternative to TEE when the primary aim is to exclude left atrial and left atrial appendage thrombus and in patients in whom the risks associated with TEE outweigh the benefits; and 3) both options should be discussed with the patient in the setting of shared decision making.

Multidetector computed tomography in planning the treatment of atrial fibrillation

OBJECTIVE

To know the anatomy of the pulmonary veins (PVs) by multidetector computed tomography (MDCT) in patients with atrial fibrillation (AF) prior to ablation.

MATERIALS AND METHODS

MDCT was performed in 89 patients with AF, analyzing the number of PVs, accessory variants and veins, diameter and ostial shape, distance to the first bifurcation and thrombus in the left atrial appendage.

RESULTS

The most frequent venous pattern was 4 PVs (two right and two. left) in 49 patients (55.1%). The superior veins had a statistically significant greater mean ostial diameter than the inferior veins (Right Superior Pulmonary Vein (RSPV)> Right Inferior Pulmonary Vein (RIPV); p=0.001 and Left Superior Pulmonary Vein (LSPV)> Left Inferior Pulmonary Vein (LIPV); p<0.001). The right pulmonary veins ostial diameters were significantly larger than the left pulmonary veins ostial diameters (RSPV> LSPV; p<0.001 and RIPV> LIPV; p<0.001). The most circular ostium was presented by the VPID (ratio: 0.885) compared to the LIPV (p<00.1) and LSPV (p<0.001). The superior veins had a statistically significant greater mean distance to first bifurcation than the inferior veins (RSPV> RIPV; p=0.008 and LSPV> LIPV; p=0.038). Mean distance to first bifurcation has been greater in left PVs respect to the right PVs (LSPV> RSPV; p<0.001and LIPV> RIPV; p<0.001). Other findings found in AI: diverticula (30), accessory auricular appendages (5), septal aneurysms (8), septal bags (6) and 1 thrombus in the left atrial appendage.

CONCLUSION

MDCT prior to ablation demonstrates the anatomy of the left atrium (LA) and pulmonary veins with significant differences between the diameters and morphology of the venous 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.

Treatment Planning Considerations for Robotic Guided Cardiac Radiosurgery for Atrial Fibrillation

Purpose

Robotic guided stereotactic radiosurgery has recently been investigated for the treatment of atrial fibrillation (AF). Before moving into human treatments, multiple implications for treatment planning given a potential target tracking approach have to be considered.   

Materials & Methods

Theoretical AF radiosurgery treatment plans for twenty-four patients were generated for baseline comparison. Eighteen patients were investigated under ideal tracking conditions, twelve patients under regional dose rate (RDR = applied dose over a certain time window) optimized conditions (beam delivery sequence sorting according to regional beam targeting), four patients under ultrasound tracking conditions (beam block of the ultrasound probe) and four patients with temporary single fiducial tracking conditions (differential surrogate-to-target respiratory and cardiac motion).  

Results

With currently known guidelines on dose limitations of critical structures, treatment planning for AF radiosurgery with 25 Gy under ideal tracking conditions with a 3 mm safety margin may only be feasible in less than 40% of the patients due to the unfavorable esophagus and bronchial tree location relative to the left atrial antrum (target area). Beam delivery sequence sorting showed a large increase in RDR coverage (% of voxels having a larger dose rate for a given time window) of 10.8-92.4% (median, 38.0%) for a 40-50 min time window, which may be significant for non-malignant targets. For ultrasound tracking, blocking beams through the ultrasound probe was found to have no visible impact on plan quality given previous optimal ultrasound window estimation for the planning CT. For fiducial tracking in the right atrial septum, the differential motion may reduce target coverage by up to -24.9% which could be reduced to a median of -0.8% (maximum, -12.0%) by using 4D dose optimization. The cardiac motion was also found to have an impact on the dose distribution, at the anterior left atrial wall; however, the results need to be verified.

Conclusion

Robotic AF radiosurgery with 25 Gy may be feasible in a subgroup of patients under ideal tracking conditions. Ultrasound tracking was found to have the lowest impact on treatment planning and given its real-time imaging capability should be considered for AF robotic radiosurgery. Nevertheless, advanced treatment planning using RDR or 4D respiratory and cardiac dose optimization may be still advised despite using ideal tracking methods.

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.

Left atrio-vertebral ratio: A new computed-tomography measurement to identify left atrial dilation

BACKGROUND

Left cardiac chambers dilation, interstitial lung changes and pleural effusions are the characteristics of cardiogenic pulmonary oedema on computed tomography (CT) of the chest but mensuration of the left atrial size is not routinely performed. Cardiac chambers normal dimensions are known to be proportional to the patient's build and anthropomorphic data but adjustment of chambers dimensions to available elements seen on the axial CT images has never been evaluated before.

OBJECTIVES

Our objective was to use data easily available on axial images to directly scale the left atrium. We chose to divide the left atrial diameter by the thoracic vertebral diameter, using the latter as a body-mass indicator. As a preliminary study, we aimed to evaluate the range of values of this left atrio-vertebral ratio (LAVR) by comparing patients suffering from cardiogenic pulmonary oedema with patients free of cardiac disease. We hypothesized that if the difference of values in these two populations of patients was significant enough, this ratio would be relevant and could be used as a quick criterion in different clinical situations.

METHOD

Two radiologists reviewed CT scans of 32 of patients free of cardiac disease and 40 patients in acute cardiac failure. The maximum diameter of the left atrium at the level of the right inferior pulmonary vein was divided by the vertebral transverse diameter to generate a left atrio-vertebral ratio. Receiver operating characteristic curves identified the threshold associated with pulmonary oedema.

MEASUREMENTS AND MAIN RESULTS

The mean LAVR was 1.85 ± 0.27 in asymptomatic patients and 2.48 ± 0.35 in patients with pulmonary oedema. A LAVR of 2.1 yielded 85% sensitivity and 88% specificity for the diagnosis of cardiogenic pulmonary oedema.

CONCLUSIONS

LAVR is a simple new measure directly scaling the left atrial diameter to the anthropomorphic characteristics of the patient. In our series, a ratio above 2.1 is strongly associated with cardiogenic pulmonary oedema indirectly suggesting left atrial dilation. The results were significantly different between the two populations of patients (no heart condition versus cardiogenic pulmonary oedema) suggesting a high potential for clinical application.

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.

Left atrial anatomy relevant to catheter ablation

The rapid development of interventional procedures for the treatment of arrhythmias in humans, especially the use of catheter ablation techniques, has renewed interest in cardiac anatomy. Although the substrates of atrial fibrillation (AF), its initiation and maintenance, remain to be fully elucidated, catheter ablation in the left atrium (LA) has become a common therapeutic option for patients with this arrhythmia. Using ablation catheters, various isolation lines and focal targets are created, the majority of which are based on gross anatomical, electroanatomical, and myoarchitectual patterns of the left atrial wall. Our aim was therefore to review the gross morphological and architectural features of the LA and their relations to extracardiac structures. The latter have also become relevant because extracardiac complications of AF ablation can occur, due to injuries to the phrenic and vagal plexus nerves, adjacent coronary arteries, or the esophageal wall causing devastating consequences.

The role of computed tomography in pre-procedural planning of cardiovascular surgery and intervention

Advances in our knowledge of cardiovascular disorders coupled with technological innovations have enabled the increased use of minimally invasive cardiovascular surgeries and transcatheter interventions, with resultant reduced morbidity and hospital stay. Three-dimensional imaging, particularly computed tomography (CT) is increasingly used for patient selection, providing a roadmap of the anatomy and identifying factors that may complicate these procedures. Advantages of CT are the rapid turnaround time, good spatial and temporal resolutions, wide field of view and three-dimensional multi-planar reconstruction capabilities. This pictorial review describes the role of CT in the pre-operative evaluation of patients undergoing cardiovascular surgeries and intervention. Main Messages • CT scan is valuable in pre-operative evaluation for cardiac surgeries • Cardiovascular structures, including bypass grafts should be located >10 mm from the sternum in patients for reoperative cardiothoracic surgeries • Knowledge of variations in pulmonary venous anatomy are essential for planning radiofrequency ablation.

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.

Time-resolved MR venography of the pulmonary veins precatheter-based ablation for atrial fibrillation

PURPOSE

To evaluate time-resolved magnetic resonance angiography (TR-MRA) of the pulmonary venous circulation using the time-resolved angiography with interleaved stochastic trajectories (TWIST) method and compare it with the more commonly used conventional contrast-enhanced magnetic resonance angiography (CE-MRA) approach in atrial fibrillation patients referred for preablation pulmonary vein mapping.

MATERIALS AND METHODS

This study was approved by the Institutional Review Board. Twenty-six patients (15 males; age 59.6 ± 12.7 years) referred for preablation pulmonary vein mapping underwent both conventional CE-MRA and TR-MRA with TWIST. Imaging was performed on a 1.5 T (Magnetom Avanto, Siemens Healthcare, Erlangen, Germany) MRI scanner. Source partition and maximum intensity projection (MIP) images were evaluated retrospectively. For quantitative analysis, pulmonary vein ostium orthogonal dimensions were measured using double oblique multiplanar reformatting. The results were analyzed using paired t-tests, Lin's concordance correlation coefficient, and Bland-Altman plots. For qualitative analysis, both source partition images and MIP images were assessed by two observers (A.P. and M.G.). The presence of common ostiums or accessory veins was recorded and analyzed using unweighted Cohen's kappa. Pulmonary vein conspicuity was scored on a scale of 1-4 (1 = poor, 2 = fair, 3 = good, 4 = excellent) and analyzed using paired t-tests, intraclass correlation coefficients, and quadratic weighted kappa statistics.

RESULTS

Orthogonal venous diameters were comparable for both TR-MRA and conventional CE-MRA (1.34 ± 0.37 vs. 1.38 cm ± 0.36, respectively). Results of paired t-tests, Lin's concordance correlation coefficient, and Bland-Altman analysis revealed relatively close comparison between methods. The magnitude of the mean difference for any of the statistical comparisons did not exceed 0.10 cm. The visualization of variant pulmonary vein anatomy was very similar for both techniques. Agreement between techniques was determined to be "good" to "very good" (κ = 0.78-0.85). Conspicuity scores for each pulmonary vein were also very close. Paired t-tests, intraclass correlation coefficients, and quadratic weighted kappa statistics all revealed strong agreement between methods.

CONCLUSION

TR-MRA using TWIST produces comparable anatomic images and pulmonary venous dimensions to the more widely used CE-MRA technique. Additionally, the TWIST technique improves arterio-venous separation, does not need exact bolus timing, requires less gadolinium, and gives additional information on vein perfusion.

Low-dose electrocardiography synchronized nonenhanced computed tomography for assessing left atrium and pulmonary veins before radiofrequency catheter ablation for atrial fibrillation

Recently contrast-enhanced cardiac computed tomography (CT) was found to be useful for imaging the left atrium and pulmonary veins (PVs) before radiofrequency catheter ablation in patients with atrial fibrillation. However, the risks of contrast agent in patients with impaired renal function must be considered. We investigated the accuracy of low-dose electrocardiographically synchronized nonenhanced cardiac CT (NECT) for identifying PV anatomy. One hundred eight consecutive patients who underwent cardiac CT before radiofrequency catheter ablation of atrial fibrillation were included. Nonenhanced cardiac computed tomogram was retrospectively evaluated for each patient by 2 radiologists for the following PV anatomy: conventional pattern, conjoined ostium, and accessory PVs with number and location. Sensitivity and specificity for variations in PVs were calculated using contrast-enhanced cardiac computed tomogram as the reference standard. Detection rates for each variation were also calculated. Twenty-one right PV (RPV) variations and 11 left PV (LPV) variations were observed. NECT showed a high diagnostic performance in detecting variations in PVs for the 2 observers. For RPV variations overall sensitivity was 97.6% and specificity was 96.6%. For LPV variations overall sensitivity was 90.9% and specificity was 97.9%. Overall detection rates for variation between the 2 observers were 97.1% for accessory RPV from the right middle lobe, 100% for 4 ostia with accessory RPV from the right middle lobe and accessory RPV from the superior segment of the right lower lobe, 100% for accessory RPV from the superior segment of the right lower lobe, 88.9% for conjoined ostium of the LPV, and 100% for accessory LPV from the left lingular segment. In conclusion, variations in PV anatomy were detected with great accuracy by NECT.

Cardiac multidetector computed tomography: basic physics of image acquisition and clinical applications

Cardiac MDCT is here to stay. And, it is more than just imaging coronary arteries. Understanding the differences in and the benefits of one CT scanner from another will help you to optimize the capabilities of the scanner, but requires a basic understanding of the MDCT imaging physics.

This review provides key information needed to understand the differences in the types of MDCT scanners, from 64 – 320 detectors, flat panels, single and dual source configurations, step and shoot prospective and retrospective gating, and how each factor influences radiation dose, spatial and temporal resolution, and image noise.

Intraprocedure visualization of the esophagus using interventional C-arm CT as guidance for left atrial radiofrequency ablation

RATIONALE AND OBJECTIVES

During radiofrequency catheter ablation for atrial fibrillation, the esophagus is at risk for thermal injury. In this study, C-arm computed tomography (CT) was compared to clinical CT, without the administration of oral contrast, to visualize the esophagus and its relationship to the left atrium and the ostia of the pulmonary veins (PVs) during the radiofrequency ablation procedure.

MATERIALS AND METHODS

Sixteen subjects underwent both cardiac clinical CT and C-arm CT. Computed tomographic scans were performed on a multidetector scanner using a standard electrocardiographically gated protocol. C-arm computed tomographic scans were obtained using either a multisweep protocol with retrospective electrocardiographic gating or a non-gated single-sweep protocol. C-arm and clinical computed tomographic scans were analyzed in a random order and then compared for the following criteria: (1) visualization of the esophagus (yes or no), (2) relationship of esophageal position to the four PVs, and (3) direct contact or absence of a fat pad between the esophagus and the PV antrum.

RESULTS

The esophagus was identified in all C-arm and clinical computed tomographic scans. In four cases, orthogonal planes were needed on C-arm CT (inferior PV level). In six patients, the esophageal location on C-arm CT was different from that on CT. Direct contact was reported in 19 of 64 of the segments (30%) examined on CT and in 26 of 64 (41%) on C-arm CT. In five of 64 segments (8%), C-arm CT overestimated a direct contact of the esophagus to the left atrium.

CONCLUSIONS

C-arm computed tomographic image quality without the administration of oral contrast agents was shown to be sufficient for visualization of the esophagus location during a radiofrequency catheter ablation procedure for atrial fibrillation.

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.

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.

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.

Pulmonary vein contraction: characterization of dynamic changes in pulmonary vein morphology using multiphase multislice computed tomography scanning

BACKGROUND

The presence and extent of contraction within the pulmonary veins (PVs) have not been defined clearly.

OBJECTIVE

The purpose of this study was to determine whether PV contraction exists and can be visualized using multislice computed tomography (MSCT) scanning as this may indicate that this modality may be useful for monitoring patients after PV isolation procedures.

METHODS

Analysis was performed on 29 patients (mean age 57.5 +/- 12 years) undergoing MSCT for suspected coronary artery disease without structural heart disease or left atrial anatomical variants. Multiplane reconstructions were used to measure PV diameters at 0, 5, 10, and 15 mm from the ostium in two phases (maximum and minimum size). The ejection fractions of three 5-mm segments were calculated for each PV.

RESULTS

Right-sided and left-sided PV contraction and maximal atrial contraction occurred at a median of 85% and 95% of the cardiac cycle, respectively. The temporal concordance of minimal PV volume during peak atrial contraction indicated that the PV volume changes are secondary to active contraction rather than passive reflux and PV distension. The ejection fractions were highest in the superior veins: right superior PV (36.7%, 27.8%, and 16%, respectively, for the three segments from proximal to distal) and left superior PV (26.9%, 21.3%, and 12.1%), in comparison with the right inferior PV (21.1%, 6.6%, and -0.7%) and left inferior PV (15%, 9.3%, and 7.6%).

CONCLUSION

Volume changes related to active PV contraction occur extending up to 15 mm into the veins, and this effect is most pronounced in the superior veins.

Optimization of imaging before pulmonary vein isolation by radiofrequency ablation: breath-held ungated versus ECG/breath-gated MRA

Isolation of the pulmonary veins has emerged as a new therapy for atrial fibrillation. Pre-procedural magnetic resonance (MR) imaging enhances safety and efficacy; moreover, it reduces radiation exposure of the patients and interventional team. The purpose of this study was to optimize the MR protocol with respect to image quality and acquisition time. In 31 patients (23-73 years), the anatomy of the pulmonary veins, left atrium and oesophagus was assessed on a 1.5-Tesla scanner with four different sequences: (1) ungated two-dimensional true fast imaging with steady precession (2D-TrueFISP), (2) ECG/breath-gated 3D-TrueFISP, (3) ungated breath-held contrast-enhanced three-dimensional turbo fast low-angle shot (CE-3D-tFLASH), and (4) ECG/breath-gated CE-3D-TrueFISP. Image quality was scored from 1 (structure not visible) to 5 (excellent visibility), and the acquisition time was monitored. The pulmonary veins and left atrium were best visualized with CE-3D-tFLASH (scores 4.50 +/- 0.52 and 4.59 +/- 0.43) and ECG/breath-gated CE-3D-TrueFISP (4.47 +/- 0.49 and 4.63 +/- 0.39). Conspicuity of the oesophagus was optimal with CE-3D-TrueFISP and 2D-TrueFISP (4.59 +/- 0.35 and 4.19 +/- 0.46) but poor with CE-3D-tFLASH (1.03 +/- 0.13) (p < 0.05). Acquisition times were shorter for 2D-TrueFISP (44 +/- 1 s) and CE-3D-tFLASH (345 +/- 113 s) compared with ECG/breath-gated 3D-TrueFISP (634 +/- 197 s) and ECG/breath-gated CE-3D-TrueFISP (636 +/- 230 s) (p < 0.05). In conclusion, an MR imaging protocol comprising CE-3D-tFLASH and 2D-TrueFISP allows assessment of the pulmonary veins, left atrium and oesophagus in less than 7 min and can be recommended for pre-procedural imaging before electric isolation of pulmonary veins.

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.