Computed tomographic analysis of the anatomy of the left atrium and the esophagus: implications for left atrial catheter ablation

Esophagus imaging for radiofrequency ablation of atrial fibrillation using a dual-source computed tomography system: Preliminary observations

OBJECTIVE

The very recent introduction of dual-source computed tomography (DSCT) has significantly improved the temporal resolution of ECG-gated multidetector-row cardiac computed tomography (CT). The aim of the present study was to evaluate whether with a DSCT visualization of the esophagus is feasible without any use of contrast in the esophagus.

MATERIALS AND METHODS

A total of 20 patients were evaluated. Ten patients underwent examination with a DSCT scanner without a gastric tube. In another ten patients, which served as control group, a CT scan was performed with a radio-opaque gastric tube prior to circumferential pulmonary vein isolation (in seven patients with a 16-slice CT and in three patients with a DSCT).

RESULTS

In the control group the gastric tube and the left atrium were reconstructed and were well visualized in all ten patients in the electro-anatomic mapping system, independently whether 16-row CT or DSCT scan was used. In the study group integration of the esophagus into the electro-anatomic mapping system was not feasible, due to the lacking contrast counterpart the surrounding tissue.

CONCLUSIONS

Even with the newest generation of DSCT scanner it is not possible to integrate the esophagus image into the 3-D electroanatomic mapping system without contrast by whatever means. However placing a conventional gastric tube before performing the CT scan allowed visualization and integration of the esophagus into the 3-D electro-anatomical map in all patients.

Image integration in electroanatomic mapping

Over the past five years, integration of the pre-procedural MR/CT images with a 3D electroanatomic mapping system has been developed to facilitate catheter ablation of clinical arrhythmias. It presents a significant advantage over the less-detailed surrogate geometry created by the 3D mapping systems. The process of image integration consists of pre-procedural imaging, image segmentation and image registration. Clinical studies have demonstrated the feasibility and accuracy of the use of image integration to guide catheter ablation of atrial fibrillation (AF). Accurate registration of the 3D left atrial MR/CT image to the real-time catheter mapping space can be technically challenging. Several important considerations should be taken into account to minimize registration error. Enhanced ability of catheter navigation with image integration may improve the efficacy and safety of anatomically based ablation strategies such as ablations of AF and nonidiopathic ventricular tachycardia. New developments in the field include integration of pathophysiologic as well as real-time anatomic information to the 3D mapping systems, and the use of new navigation system to improve registration.

CT radiographic findings: atrio-esophageal fistula after transcatheter percutaneous ablation of atrial fibrillation

INTRODUCTION

Radio-frequency catheter ablation (RFCA) is an ever increasing modality for treating refractory atrial fibrillation. Radiologists should not only be able to interpret and convey anatomic variations of pulmonary veins and left atrium to referring electrophysiologists, but also should be aware of all the post-RFCA complications and their radiographic findings including this rare, but often fatal complication. This report describes a fatal atrio-esophageal fistula (AEF) involving a normal variant single left common pulmonary vein after transcatheter ablation.

RESULTS

A 59-year-old man who presented to the Emergency Department (ED) with altered mental status previously complaining of fatigue and malaise. The patient underwent a total of 2 uneventful circumferential percutaneous pulmonary vein ablations for atrial fibrillation. The most recent was performed 5 weeks before admission to ED. Within hours of initial evaluation, the patient quickly deteriorated owing to overwhelming sepsis requiring both inotropic and ventilatory support. Transthoracic echocardiography within ED showed no evidence of valvular vegetation or gas bubbles in the left atrium. Computed tomography (CT) of the chest with intravenous contrast revealed findings compatible with AEF. Head CT was negative for ischemic changes or emboli. Patient underwent emergent cardiac and esophageal surgery at which point the patient later died on the operating table.

CONCLUSIONS

Patients who present with signs and symptoms of endocarditis, and particularly with new neurologic symptom after RFCA should be promptly evaluated for AEF. In our case, radiographic findings in correlation with clinical history and high suspicion strongly suggested this rare, often fatal complication. During review of the chest CT, particular vigilance should be made to the left pulmonary vein/posterior left atrium junction at which site fistulous tracts tend to occur. Prompt diagnosis necessitates emergent cardiac and esophageal surgery to prevent rapid deterioration and death.

Atrioesophageal Fistula After Catheter Pulmonary Venous Ablation for Atrial Fibrillation: Imaging Features

Atrioesophageal fistula is a rare but highly morbid complication of catheter-mediated pulmonary vein ablation for the treatment of atrial fibrillation. Among patients who do not exsanguinate from upper gastrointestinal tract bleeding, presentation includes sepsis and embolic cerebrovascular disease. We present a case of atrioesophageal fistula after pulmonary venous ablation as a treatment for atrial fibrillation, focusing on the imaging features of this diagnosis.

Close relationship between the bronchi and pulmonary veins: implications for the prevention of atriobronchial fistula after atrial fibrillation ablation

INTRODUCTION

Atrio-bronchial fistula (ABF) can be a rare but potentially lethal complication following the catheter ablation of atrial fibrillation (AF). Understanding the extent of the contact between the bronchial tree and pulmonary veins (PVs) is critical to avoid this complication. We investigated the anatomic relationship between the four PVs and bronchial tree using multi-detector computed tomography (MDCT) images.

METHODS AND RESULTS

Seventy patients with drug refractory AF were included. They underwent 16-slice MDCT before the ablation. The spatial relationship between the bronchus and PVs was demonstrated by the multi-planar images. The bronchus was in direct contact with four PVs in the vast majority of patients. The mean distances between the bronchus and the ostia of right superior, left superior, right inferior, and left inferior PV were 7.1 +/- 5.5, 3.5 +/- 4.8, 12.3 +/- 5.6, and 17.9 +/- 6.8 mm, respectively. Patients were categorized into two groups: Group I: proximal contact (<5 mm from the PV ostium) and Group II: distal contact (>5 mm from the PV ostium). For the right superior pulmonary vein (RSPV), the Group I patients were associated with thinner connective tissue between them (P = 0.001), a larger RSPV (17.2 +/- 2.2 vs 15.5 +/- 2.1 mm, P < 0.001), and right inferior pulmonary vein (RIPV) diameter (15.9 +/- 1.9 vs 14.6 +/- 1.6 mm, P < 0.01). For the left superior pulmonary vein (LSPV), the Group I patients were associated with an older age (P = 0.02).

CONCLUSION

Isolation of the superior PVs may carry the potential risk of bronchial damage. The clinical or anatomic characteristics associated with the proximal contact between the bronchi and superior PVs can provide useful information to prevent this complication.

Trastornos del ritmo cardíaco: un reto para el radiólogo

Arrhythmia or altered heart rhythms can present with or without underlying heart disease. Most cardiopathies give rise to arrhythmias; however, arrhythmias can also be caused in previously healthy hearts by other conditions such as metabolic disorders, electrolyte imbalances, and drug use or abuse. The clinical presentation can range from asymptomatic cases discovered incidentally on routine examination to sudden death as the only clinical sign. In cases with clinical suspicion of arrhythmia, Holter and electrophysiological studies should be performed. If the condition is confirmed, associated cardiopathy must be ruled out. Echocardiography should be the first imaging test to be performed. Multidetector computed tomography (CT) and magnetic resonance imaging (MRI) have been applied to the field of cardiology more recently and are gradually acquiring specific roles with precise indications. In the study of arrhythmias, MRI is indicated in two particular areas: auricular fibrillation and arrhythmogenic right ventricular dysplasia.

Evaluation of left atrial and posterior mediastinal anatomy by multidetector helical computed tomography imaging: relevance to ablation

INTRODUCTION

Increasing use of catheter ablation in the left atrium (LA) requires understanding of substrate anatomy, especially with regard to potential damage to adjacent structures.

METHODS AND RESULTS

We reviewed multidetector helical computed tomography (MDCT) imaging on 42 subjects, 26 imaged before planned LA ablation for atrial fibrillation (AF), and 16 without AF. LA volume and dimensions were larger in patients with AF (p < 0.05) and the spine and aorta (Ao) impressed the LA more frequently in the AF group. The esophagus (Eo) was the predominant feature on the posterior LA wall, contacting it in all patients. The Ao was in contact with the LA body or the left inferior pulmonary vein (PV) in 32 (76%) of 42 cases, and in 10 it ran along an indentation on the posterior aspect of the LA. The coronary sinus was adjacent to LA ablation sites, the azygos vein was rarely adjacent to those sites, and the left bronchus abutted the PV ostium but not the LA. Two patients had findings that directly impacted the ablation procedure: one patient had a dilated fluid filled Eo with esophageal stricture and underwent nasogastric decompression before ablation, and one was discovered to have an anomalous PV and underwent surgical repair.

CONCLUSIONS

MDCT imaging identifies structures adjacent to the LA, which could be affected by ablation. Posterior LA topography can be influenced by the position of the Ao or by the proximity of the spine. Preprocedural imaging can characterize anatomic structures that could be vulnerable during ablation, and detect unusual pathology that can affect the treatment plan.

Value of CT localization of the fossa ovalis prior to transseptal left heart catheterization for left atrial ablation

AIMS

Transseptal puncture (TP) can be a difficult procedure and is not without risk of complications. The purpose of this study was to evaluate the use of three-dimensional multi-detector row computed tomography (MDCT) to localize the fossa ovalis (FO) and facilitate TP in patients undergoing left atrial catheter ablation.

METHODS AND RESULTS

Fourteen consecutive patients were studied. Thirteen patients underwent pulmonary vein isolation and one patient had ablation for left atrial flutter. All patients underwent cardiac MDCT imaging pre-ablation for use in conjunction with electroanatomic mapping. Prior to puncturing the interatrial septum, standard fluoroscopic views of the transseptal sheath were compared with corresponding MDCT images tagging the FO. Successful, uncomplicated TP was achieved in all 14 patients. The mean duration of TP was 15.6 +/- 10.0 min. The average fluoroscopy time was 8.5 +/- 7.4 min. The MDCT images were deemed helpful in facilitating TP in 13 patients (93%).

CONCLUSION

This study demonstrates the feasibility of MDCT to localize the FO and aid TP. For patients undergoing left atrial ablation in whom MDCT imaging is undertaken pre-ablation, tagging the FO can be easily performed and is a novel tool for guiding transseptal catheterization without additional risk.

Esophageal temperature monitoring during radiofrequency catheter ablation: experimental study based on an agar phantom model

Although previous studies have established the feasibility of monitoring esophageal temperature during radiofrequency cardiac ablation using an esophageal temperature probe (ETP), some questions remain regarding its efficacy. The aims of this study were to study the effect of the location of the ETP on the temperature reached, and to test the characteristics of ETP as used in clinical practice. We constructed an agar phantom to model the thermal and electrical characteristics of the biological tissues (left atrium, esophagus and connective tissue). The ETP was positioned at 6.5 mm from an ablation electrode and at distances of 0, 5, 10, 15, 20 mm from the catheter axis. A thermocouple was located on the probe to measure the actual temperature of the external esophageal layer during the ablations (55 degrees C, 60 s). The mean temperatures reached at the thermocouple were significantly higher than those measured by the ETP (48.3 +/- 1.9 degrees C versus 39.6 +/- 1.1 degrees C). The temperature values measured with the ETP were significantly lower when the probe was located further from the catheter axis (up to 2.5 degrees C lower when the distance from the probe-catheter axis was 2 cm). The dynamic calibration of the ETP showed a mean value for the time constant of 8 s. In conclusion, the temperature measured by the ETP always underestimates the temperature reached in the thermocouple. This fact can be explained by the distance gap between the thermocouple and probe and by the dynamic response of the ETP. The longer the distance between the ETP and catheter axis, the higher is the temperature difference.

[New therapy possibilities for arrhythmias using catheter ablation]

Radiofrequency current ablation has been developed over the last 20 years to be the standard approach for treating tachycardia by catheter ablation. By combining new 3-D imaging technology (CT and MRI) with 3-D electrophysiologic mapping systems, a new tool has been created to display the cardiac activation sequence of the individual. These technologies are extremely important for the treatment of complex arrhythmias such as the catheter ablation of atrial fibrillation. Instead of the conventional "point by point" linear ablation procedure, balloon catheters have been applied to a circumferential linear lesion in a "single shot" procedure using, for example, cryothermia, ultrasound or laser energy. Finally, magnetic navigation is a new steering tool for performing ablation procedures, leading to reduced exposure to ionizing radiation.

Accuracy of integration of multislice computed tomography imaging into three-dimensional electroanatomic mapping for real-time guided radiofrequency ablation of left atrial fibrillation—Influence of heart rhythm and radiofrequency lesions

Circumferential radiofrequency ablation around the orifices of the pulmonary veins is a curative catheter-based therapy of paroxysmal and persistent atrial fibrillation (AF). Three-dimensional cardiac image integration is a promising new technology to visualize the complex left atrial anatomy and neighbouring structures. This study aimed to validate the accuracy of integrating multislice computed tomography (MSCT) into three-dimensional electroanatomic mapping (EAM) to guide radiofrequency catheter ablation (CA) of AF. Forty consecutive patients (34 male, mean age 56 +/- 10 years) with multidrug-resistant AF underwent 16-slice MSCT 1 day before radiofrequency CA. MSCT data were processed and imported to the Cartotrade mark EAM system. Using the CartoMergetrade mark Image Integration Module, the generated EAM was aligned with the MSCT images. An integrated statistical algorithm provided information about the accuracy of the fusion process. In every single patient, MSCT images could be aligned with the EAM. Mean distance between the EAM points (n = 63 +/- 14) and the MSCT surface was 1.6 +/- 1.2 mm with no difference between sinus rhythm versus AF (p = 0.145) and no distinction between patients in paroxysmal versus persistent/permanent AF despite a significant difference in left atrial diameters. An average of 388 +/- 81 radiofrequency ablation points were taken within the procedures resulting in a mean distance of 2.3 +/- 1.8 mm between the EAM points and the MSCT image after the ablation procedure. There was a significant difference of alignment accuracy before and after radiofrequency CA (p < 0.001). MSCT images can be accurately integrated into three-dimensional EAM. Pre-interventional cardiac rhythm does not influence the precision of fusion. Accuracy of fusion deteriorates after radiofrequency CA.

Usefulness of transesophageal echocardiography in the isolation of pulmonary veins in the treatment of atrial fibrillation

BACKGROUND

New imaging strategies for atrial fibrillation (AF) ablation should enhance the safety of this technique. The role of transesophageal echocardiography (TEE) in this setting has not been prospectively evaluated.

METHODS

Under general anesthesia, 85 patients underwent TEE-guided AF ablation. A hybrid technique was performed with circular pulmonary veins (PV) lesions and antrum and ostial electrical isolation guided by TEE. TEE excluded left atrial (LA) thrombus, guided transseptal puncture and catheter positioning, and helped to identify PV ostia and their velocities. The TEE probe localized the esophagus, its temperature (T degrees ) and micro bubbles formation.

RESULTS

Overall, one patient had a LA clot. The esophagus was located close to left PV in 38%, the right PV in 28%, midline in 17% and with an oblique course in 17% of patients. Right and left superior PV velocities were detected in 100%, left inferior PV in 88% and right inferior PV in 82% of patients. Microbubbles were detected in 9 patients (11%). Elevation of TEE T degrees occurred in 14 patients (16%) and was regularly observed when lesions were applied over the TEE probe shadow, in close proximity to the posterior wall. Two major complications (1 tamponade, 1 PV laceration) occurred and were detected early by TEE.

CONCLUSIONS

TEE offers advantages compared to a map-guided only approach. It is a reliable tool to assess esophagus T degrees and localization, guide transseptal puncture, delineate the PV ostia, and monitor complications.

CT of the Pulmonary Veins

Atrial fibrillation (AF) is a common cardiac rhythm disturbance and its incidence is increasing. Radiofrequency catheter ablation (RFCA) is a highly successful therapy for treating AF, and its use is becoming more widespread; however, with its increasing use and evolving technique, known complications are better understood and new complications are emerging. Computed tomography (CT) of the pulmonary veins, or more correctly, the posterior left atrium (LA), has an established role in precisely defining the complex anatomy of the LA and pulmonary veins preablation and has an expanding role in identifying the myriad of possible complications postablation. The purposes of this article are: to review AF and RFCA; to discuss CT evaluation of the LA and pulmonary veins preablation; and to review the complications of RFCA focusing on the role of CT postablation.

Variation in left atrial transmural wall thickness at sites commonly targeted for ablation of atrial fibrillation

BACKGROUND

The number of catheter ablations performed for atrial fibrillation (AF) has increased dramatically over the past several years. Regional variation in left atrial (LA) wall thickness is known to exist but have not been described in detail. AF ablation success and complication rates may be related to regional differences in LA wall thickness.

OBJECTIVE

To evaluate differences in transmural wall thickness in five pre-defined anatomic areas within the LA which are commonly targeted for AF ablation.

MATERIALS AND METHODS

We measured LA wall transmural thickness in 34 human heart specimens using calipers in five anatomic areas frequently targeted during AF ablation (anterior wall, septum, mitral isthmus, posterior wall and roof).

RESULTS

The autopsied individuals were 53% female, 67.7% had CAD, 14.7% had atrial fibrillation, 61.8% had hypertension, and 21.6% had congestive heart failure. The roof was the thinnest region with mean thickness measuring significantly less than each other area (p 0.005 for the posterior wall and <0.001 for all other areas). The septum was the thickest region with mean thickness measuring significantly greater than each other area (p = 0.05, 0.001, <0.001, <0.001 measured against the anterior wall, isthmus, posterior wall and roof, respectively).

CONCLUSIONS

Significant regional differences exist for mean left atrial wall thickness among the different anatomic areas within the left atrium which are often targeted during catheter ablation of AF. These differences may have significant implications in determining the ideal intensity and total duration of radiofrequency energy required to achieve a safe and successful ablation.

Three-dimensional rotational angiography of the left atrium and esophagus—A virtual computed tomography scan in the electrophysiology lab?

BACKGROUND

Three-dimensional (3D) reconstruction of the heart and surrounding structures has been supplementing traditional two-dimensional imaging to guide diagnostic and therapeutic electrophysiologic procedures. Current methods using computed tomography (CT)/magnetic resonance imaging (MRI) reconstruction have certain limitations.

OBJECTIVE

We investigated the feasibility of rotational angiography (RA) combined with simultaneous esophagogram to create an intraprocedural 3D reconstruction of the left atrium (LA) and the esophagus.

METHODS

Rotational angiography was performed. Contrast was injected via a pigtail catheter positioned in the left or right pulmonary artery to achieve a levophase venous cycle opacification of the ipsilateral pulmonary veins and adjacent LA. Simultaneous administration of oral contrast allowed a 3D reconstruction of the esophagus in the same image. Qualitative and quantitative comparison between the intraprocedural 3D RA and a remote CT scan was performed in 11 consecutive patients undergoing ablation for atrial fibrillation.

RESULTS

Adequate visualization of the pulmonary veins, adjacent posterior LA, and esophagus was achieved in 10 patients. Determination of pulmonary transit time to guide the initiation of RA resulted in better-quality imaging. A close correlation between 3D RA and CT was found. Based on close proximity between the LA and esophagus, the ablation procedure was modified in three patients.

CONCLUSIONS

Three-dimensional RA of the LA and esophagus is a promising new method allowing intraprocedural 3D reconstruction of these structures comparable in quality to a CT scan. Further studies refining the method are justified because it could eliminate the need for CT/MRI scans before ablation.

Anatomic Characteristics of the Left Atrial Isthmus in Patients with Atrial Fibrillation: Lessons from Computed Tomographic Images

INTRODUCTION

Left atrial (LA) isthmus ablation was reported to improve the success rate of catheter ablation of paroxysmal atrial fibrillation (AF). LA isthmus ablation could also cure a subset of LA flutter. Therefore, understanding the anatomy of the LA isthmus is important for performing the ablation effectively.

METHODS AND RESULTS

Group I included 45 patients (40 male, mean age = 50 +/- 13 years) with paroxysmal AF who underwent catheter ablation. Group II included 45 patients (37 male, mean age = 54 +/- 10 years) without a history of AF. They underwent a 16-slice multidetector computed tomography (MDCT) scan to delineate the LA structures before the ablation procedure. The average length of the LA isthmus was longer in group I than in group II (lateral isthmus: 3.30 +/- 0.68 vs 2.71 +/- 0.60 cm, P < 0.001; medial isthmus: 5.12 +/- 0.94 vs 4.45 +/- 0.63 cm, P < 0.001), and morphological patterns of lateral and medial isthmus were similar between groups. In addition, the average depth of lateral isthmus was similar between groups (0.62 +/- 0.32 vs 0.55 +/- 0.33 cm, P = 0.41), but the average depth of medial isthmus was larger in group I than in group II (0.60 +/- 0.32 vs 0.44 +/- 0.25 cm, P = 0.01). The medial isthmus had more ridges, as compared to the lateral isthmus (13% vs 0%, P = 0.026). Furthermore, the distances between esophagus and lateral isthmus were longer in group I than in group II (at the middle of isthmus and mitral annulus level: 21.0 +/- 4.8 vs 18.4 +/- 6.0 mm, P < 0.001; and 37.1 +/- 5.7 vs 29.6 +/- 8.1 mm, P < 0.001, respectively).

CONCLUSION

The LA isthmus was longer in the AF patients. The morphology of the isthmus was variable. Compared with the lateral isthmus, the medial isthmus was longer and had more ridges. A peculiar configuration of the isthmus provided by CT images could influence the ablation strategy.

Posterior left atrial–esophageal relationship throughout the cardiac cycle

BACKGROUND

Radiofrequency energy delivered throughout the cardiac cycle has the potential to cause thermal injury to the esophagus if the anatomical relationship between the posterior left atrium and the esophagus changes during cardiac motion.

OBJECTIVE

To assess the posterior left atrial-esophageal relationship throughout the cardiac cycle.

METHODS

In this study, the anatomical relationship between the posterior left atrium and the esophagus was assessed throughout the cardiac cycle in 10 consecutive patients. All patients underwent contrast-enhanced, ECG-gated CT scanning. Left atrial volumes and the esophageal structure were generated from the reconstructed data at 10 phases of the cardiac cycle from 5% to 95% of the R-R interval. The posterior left atrial-esophageal anatomical relationship was measured at four levels, the superior pulmonary vein ostial site, and the upper, mid and lower left atrium.

RESULTS

There were significant variations in the left atrial-esophageal relationship in the 10 patients. The relative movement between the esophagus and the posterior left atrium throughout the cardiac cycle in the anteroposterior and right-to-left orientations was 0.55 +/- 0.99 mm and 0.60 +/- 1.02 mm (95% confidence interval, 2.03 and 1.98 respectively).

CONCLUSIONS

Under normal conditions, there is little change in the anatomical relationship between the posterior left atrium and the esophagus during the entire cardiac cycle. However, due to the interpatient variability at the esophageal location, identification of esophageal location may help prevent complications during catheter ablation procedures involving the left atrium.

Cardiovascular Imaging in the Management of Atrial Fibrillation

Atrial fibrillation (AF) is he most commonly encountered arrhythmia in clinical practice, with an overall prevalence of 0.4% in the general population. Recent advances in technology and in the understanding of the pathophysiology of AF have led to more definitive and potentially curative therapeutic approaches. Echocardiography has a well-established role in the assessment of cardiac structure and function and risk stratification, and has become an essential part of the guidelines for management of AF. The development of intracardiac echocardiography has led to real-time guidance of percutaneous interventions, including radiofrequency ablation and left atrial appendage closure procedures for patients with AF. Other imaging modalities, including computed tomography and magnetic resonance angiography, have allowed for more accurate measurement and better understanding of the cardiac anatomy. We review the impact of various imaging modalities in the evaluation and management of AF.

Atrial fibrillation: Catheter ablation

Catheter ablation of atrial fibrillation (AF) has evolved dramatically over the last several years. The initial efforts in the catheter-based management of AF targeted the atrial substrate in an effort to mimic the maze procedure. After the pulmonary veins (PV) were shown to be critical in the initiation and perpetuation of AF, the focus then shifted to a trigger approach in which the PVs and other foci were targeted for ablation. The pendulum then appeared to swing back toward the substrate approach after it was shown that left atrial circumferential ablation afforded improved outcomes in patients with paroxysmal and persistent AF. It has become clear that there are several possible approaches in the catheter ablation of AF, each with its strengths and limitations. It is also becoming evident that not all patients will respond to a single ablation technique and that the ablation protocol is best tailored to suit the individual patient. This article strives to present an evidence-based review of the many techniques, and then offer a practical guide to the catheter ablation of AF.

Rapid detection and successful treatment of esophageal perforation after radiofrequency ablation of atrial fibrillation: lessons from five cases

INTRODUCTION

The aim of the study was to identify criteria for rapid recognition and successful treatment of esophageal perforation after radiofrequency ablation for atrial fibrillation (AF).

METHODS AND RESULTS

Esophageal perforation occurred in five patients after intraoperative (n = 4) or percutaneous (n = 1) AF ablation. Patients presented with high fever (n = 3) or severe chest/epigastric pain (n = 2) 8-28 days after ablation. WBC count was elevated at presentation in all patients (15,460 +/- 2,910/muL), CRP showed a delayed rise. Thoracic CT detected free air in all. Neurologic complications occurred in three cases (60%) with a delay of 5-40 hours after first symptoms. Only one (20%) developed neurologic complications within the first 24 hours. Two patients (40%) died before surgery could be performed. In both, time from symptom onset to diagnosis was significant (24 and 36 hours). Three patients (60%) underwent esophageal resection and survived. In two of them, treatment was rapid with time from symptoms to surgery of 24 hours; they had favorable outcome. In the third surviving patient, surgery was late (5 days after first symptoms); permanent neurologic residues remained.

CONCLUSION

The leading symptom of esophageal perforation is high fever or severe chest/epigastric pain. Fever is not necessarily present. Leukocytosis is the earliest and most sensitive laboratory marker, thoracic CT the most valuable diagnostic examination. The dramatic neurologic complications occur with a delay of at least a few hours after first symptoms. Immediate surgery may prevent neurologic complications and could possibly result in a high survival rate without residues. Delay of treatment seems to have devastating results.

Temporary esophageal stenting allows healing of esophageal perforations following atrial fibrillation ablation procedures

BACKGROUND

Left atrial catheter ablation (LACA) has emerged as a successful method to eliminate atrial fibrillation (AF). Recent reports have described atrio-esophageal fistulas, often resulting in death, from this procedure. Temporary esophageal stenting is an established therapy for malignant esophageal disease. We describe the first case of successful temporary esophageal stenting for an esophageal perforation following LACA.

CASE

A 48-year-old man with symptomatic drug refractory lone AF underwent an uneventful LACA. Fifty-nine ablations with an 8-mm tip ablation catheter (30 seconds, 70 Watts, 55 degrees C), as guided by 3-D NavX mapping, were performed in the left atrium to isolate the pulmonary veins as well as a left atrial flutter and roof ablation line. In addition, complex atrial electrograms in AF and sites of vagal innervation were ablated. Two weeks later, he presented with sub-sternal chest pain, fever, and dysphagia. A chest CT showed a 3-mm esophageal perforation at the level of the left atrium with mediastinal soiling and no pericardial effusion. An urgent upper endoscopy with placement of a PolyFlex removable esophageal stent to seal off the esophago-mediastinal fistula was performed. After 3 weeks of i.v. antibiotics, naso-jejunal tube feedings, and esophageal stenting, the perforation resolved and the stent was removed. Over 18 months of follow-up, there have been no other complications, and he has returned to a physically active life and remains free from AF on previously ineffective anti-arrhythmic drugs.

CONCLUSION

Early diagnosis of esophageal perforations following LACA may allow temporary esophageal stenting with successful esophageal healing. Prompt chest CT scans with oral and i.v. contrast should be considered in any patient with sub-sternal chest pain or dysphagia following LACA.

Esophageal temperature during radiofrequency-catheter ablation of left atrium: a three-dimensional computer modeling study

INTRODUCTION

There is current interest in finding a way to minimize thermal injury in the esophagus during radiofrequency-catheter ablation of the left atrium. Despite the fact that the esophageal temperature is now being monitored during ablation, the influence of different anatomic and technical factors on the temperature rise remains unknown.

METHODS AND RESULTS

We implemented a three-dimensional computational model that included atrial tissue, epicardial fat, esophagus, aorta, and lung, all linked by connective tissue. The finite-element method was used to calculate the esophageal temperature distribution during a procedure of constant-temperature ablation with an 8-mm electrode, under different tissue conditions. Results showed that the distance between electrode and esophagus was the most important anatomic factor in predicting the esophageal temperature rise, the composition of the different tissues being of lesser importance. The measurement of the esophageal temperature in different sites of the lumen offered differences up to 3.7 degrees C, especially for a short electrode-esophagus distance (5 mm). The difference in the convective cooling by circulating blood around electrode and endocardium did not show a significant influence on the esophageal temperature rise.

CONCLUSION

Computer results suggest that (1) the electrode-esophagus distance is the most important anatomic factor; (2) the incorrect positioning of an esophageal temperature probe could give a low reading for the maximum temperature reached in the esophagus; and (3) the different cooling effect of the circulating blood flow at different atrial sites has little impact on the esophageal temperature rise.

Mechanical Esophageal Deflection During Ablation of Atrial Fibrillation

To prevent esophageal damage during ablation of atrial fibrillation, we developed a technique to move the esophagus away from a desired ablation site too close to the esophagus. Under fluoroscopy, a transesophageal echocardiography probe was used to deflect the barium-opacified esophagus from the ablation site. This technique was successfully employed in three patients where critical sites of the posterior left atrial wall were very close to the esophagus.

Imaging in percutaneous ablation for atrial fibrillation

Percutaneous ablation for electrical disconnection of the arrhythmogenic foci using various forms of energy has become a well-established technique for treating atrial fibrillation (AF). Success rate in preventing recurrence of AF episodes is high although associated with a significant incidence of pulmonary vein (PV) stenosis and other rare complications. Clinical workup of AF patients includes imaging before and after ablative treatment using different noninvasive and invasive techniques such as conventional angiography, transoesophageal and intracardiac echocardiography, computed tomography (CT) and magnetic resonance imaging (MRI), which offer different information with variable diagnostic accuracy. Evaluation before percutaneous ablation involves assessment of PVs (PV pattern, branching pattern, orientation and ostial size) to facilitate position and size of catheters and reduce procedure time as well as examining the left atrium (presence of thrombi, dimensions and volumes). Imaging after the percutaneous ablation is important for assessment of overall success of the procedure and revealing potential complications. Therefore, imaging methods enable depiction of PVs and the anatomy of surrounding structures essential for preprocedural management and early detection of PV stenosis and other ablation-related procedures, as well as long-term follow-up of these patients.

Usefulness of esophageal leads for determining the strategy of pulmonary vein ablation to avoid complications associated with the esophagus

To avoid fatal complications after extensive pulmonary vein (PV) ablation, it has been proved important to comprehend the anatomic relation between the PVs and the esophagus. In 42 consecutive patients with atrial fibrillation, PV ostial isolation was performed using a basket catheter. The shortest distance and anatomic relation between the esophageal lead and PV ostium, determined by successful PV ostial isolation, was analyzed in biplane fluoroscopic views. In 18 left superior PVs (LSPVs) (43%), 13 left inferior PVs (32%) (LIPVs), and all the right PVs (group A), the shortest distance was > 10 mm in > or = 1 of the biplane fluoroscopic views. In 4 LSPVs (10%) and 2 LIPVs (5%) (group B), the shortest distance was < or = 5 mm in the fluoroscopic views. In the remaining PVs (group C), the esophagus was situated directly behind 10 LSPVs (24%) and 12 LIPVs (29%) (group C1), posteromedial to 1 LSPV (2%) and 9 LIPVs (22%) (group C2), and medial to 9 LSPVs (21%) and 5 LIPVs (12%) (group C3). The risk of esophagus-associated complications with ablation around the left PV ostia was suggested to be high in group B, very low in group A, and relatively low in group C. In group C3, extensive PV ablation might increase the risk of that complication. In conclusion, esophageal leads are useful for determining strategies for PV ablation to avoid esophagus-associated complications, because they enable comprehension of the anatomic relation between the PVs and the esophagus.

Endocardial Visualization of Esophageal-Left Atrial Anatomic Relationship by Three-Dimensional Multidetector Computed Tomography "Navigator Imaging"

BACKGROUND

The close proximity of left atrium (LA) and esophagus during radiofrequency ablation for atrial fibrillation (AF) predisposes to thermal injury resulting in atrio-esophageal fistula. This work proposes to study the anatomic relationship between the esophagus and the LA wall using multidetector computed tomography (MDCT) three-dimensional (3D) "Navigator" reconstruction technique.

METHODS

Forty-five consecutive patients (37 men, mean age 52.7+/-14.1 years) with preradiofrequency ablation MDCT scans of the thorax for AF were recruited. Length and type (continuous or interrupted) of fat pad between esophagus and LA were evaluated. The position, width, and length of the esophagus in contact (without fat pad) with the LA were determined by using "Navigator" software on the endocardial view of LA.

RESULTS

The fat pad was continuous in 4% (2 of 45) and interrupted in 96% (43 of 45) patients. The mean width and length of esophageal-LA contact in 43 cases with interrupted fat pad was 24.0+/-5.8 mm (range 10.5-35.3 mm) and 41.9+/-11.6 mm (5.4-64 mm), respectively. There was an inverse relationship between the lengths of the esophageal-LA contact and the upper fat pad (r=-0.50, P=0.001). The esophagus was located to the left, right, and midline of the LA in 40, 2, and 1 patients, respectively, and the esophagus was in contact with and overrode the PV orifice in 22 and 4 patients, respectively.

CONCLUSION

Direct esophageal-LA contact without the intervening fat pad was present in 96% of the cases, with 93% of esophagi lying to the left of the LA and 51% in contact with a PV orifice. Three-dimensional Navigator imaging technique has enhanced the visualization of the anatomical information of the esophagus, LA wall, and PV orifices that may be used to avoid thermal injury to the esophagus during LA ablation procedure.

A Tailored Approach to Catheter Ablation of Paroxysmal Atrial Fibrillation

Background— Because the genesis of atrial fibrillation (AF) is multifactorial and variable, an ablation strategy that involves pulmonary vein isolation and/or a particular set of ablation lines may not be equally effective or efficient in all patients with AF. A tailored strategy that targets initiators and drivers of AF is a possible alternative to a standardized lesion set.

Methods and Results— Catheter ablation was performed in 153 consecutive patients (mean age, 56±11 years) with symptomatic paroxysmal AF with the use of an 8-mm tip radiofrequency ablation catheter. The esophagus was visualized with barium. The pulmonary veins and left atrium were mapped during spontaneous or induced AF. Arrhythmogenic pulmonary veins were isolated or encircled. If AF was still present or inducible, complex electrograms in the left atrium, coronary sinus, and superior vena cava were targeted for ablation. The end point of ablation was absence of frequent atrial ectopy and spontaneous AF during isoproterenol infusion and noninducibility of AF. Routine energy applications near the esophagus were avoided. During follow-up, left atrial flutter developed in 19% of patients and was still present in 10% at >12 weeks of follow-up. A repeat ablation procedure was performed in 18% of patients. During a mean follow-up of 11±4 months, 77% of patients were free from AF and/or atrial flutter without antiarrhythmic drug therapy. Pericardial tamponade or transient neurological events occurred in 2% of procedures.

Conclusions— A tailored ablation strategy that only targets triggers and drivers of AF is feasible and eliminates paroxysmal AF in ≈80% of patients.

Anatomic Proximity of the Esophagus to the Coronary Sinus: Implication for Catheter Ablation Within the Coronary Sinus

INTRODUCTION

The anatomic proximity between the esophagus and the coronary sinus (CS) might render the esophagus vulnerable to thermal injury during ablation. Therefore, we investigated the anatomic relationship between the esophagus and the CS in patients with atrial fibrillation (AF).

METHODS AND RESULTS

Thirty patients (25 males, mean age = 54 +/- 11 years) with drug-refractory paroxysmal AF were included. Sixteen-slice multidetector computed tomography was performed to depict the course of the esophagus and relationship to the CS. The esophagus was in direct contact with the CS in 57% (17/30) of patients (group 1). The mean length of the contact was 6.1 +/- 3.4 mm. In the remaining 13 patients, the esophagus did not come in direct contact with the CS (group 2). The shortest distance between the esophagus and the CS was 4.0 +/- 2.6 mm. The CS diameter (9.4 +/- 1.8 vs 8.5 +/- 2.4 mm, P = 0.15), esophagus width (18.6 +/- 1.6 vs 18.6 +/- 1.7 mm, P = 0.87), anteroposterior diameter of the left atrium (35.9 +/- 3.8 vs 35.0 +/- 3.3 mm, P = 0.58), thickness of the anterior wall of the esophagus (2.9 +/- 0.6 vs 2.9 +/- 0.6 mm, P = 0.97), and shortest distance from the esophagus to the CS ostium (19.3 +/- 5.4 vs 25.0 +/- 6.2 mm, P = 0.02) and to the great cardiac vein (8.5 +/- 5.3 vs 12.1 +/- 6.9 mm, P = 0.10) were compared between the two groups.

CONCLUSIONS

In 57% of our patients, the esophagus was in direct contact with the CS, and a significantly shorter distance between the esophagus and the CS ostium was noted in these patients. It is important to prevent esophageal damage when applying energy within the CS.

Electroanatomic reconstruction of the left atrium, pulmonary veins, and esophagus compared with the “true anatomy” on multislice computed tomography in patients undergoing catheter ablation of atrial fibrillation

BACKGROUND

Current concepts of catheter ablation for atrial fibrillation (AF) commonly use three-dimensional (3D) reconstructions of the left atrium (LA) for orientation, catheter navigation, and ablation line placement.

OBJECTIVES

The purpose of this study was to compare the 3D electroanatomic reconstruction (Carto) of the LA, pulmonary veins (PVs), and esophagus with the true anatomy displayed on multislice computed tomography (CT).

METHODS

In this prospective study, 100 patients undergoing AF catheter ablation underwent contrast-enhanced spiral CT scan with barium swallow and subsequent multiplanar and 3D reconstructions. Using Carto, circumferential plus linear LA lesions were placed. The esophagus was tagged and integrated into the Carto map.

RESULTS

Compared with the true anatomy on CT, the electroanatomic reconstruction accurately displayed the true distance between the lower PVs; the distances between left upper PV, left lower PV, right lower PV, and center of the esophagus; the longitudinal diameter of the encircling line around the funnel of the left PVs; and the length of the mitral isthmus line. Only the distances between the upper PVs, the distance between the right upper PV and esophagus, and the diameter of the right encircling line were significantly shorter on the electroanatomic reconstructions. Furthermore, electroanatomic tagging of the esophagus reliably visualized the true anatomic relationship to the LA. On multiple tagging and repeated CT scans, the LA and esophagus showed a stable anatomic relationship, without relevant sideward shifting of the esophagus.

CONCLUSION

Electroanatomic reconstruction can display with high accuracy the true 3D anatomy of the LA and PVs in most of the regions of interest for AF catheter ablation. In addition, Carto was able to visualize the true anatomic relationship between the esophagus and LA. Both structures showed a stable anatomic relationship on Carto and CT without relevant sideward shifting of the esophagus.

Real-Time Monitoring of Luminal Esophageal Temperature During Left Atrial Radiofrequency Catheter Ablation for Atrial Fibrillation: Observations About Esophageal Heating During Ablation at the Pulmonary Vein Ostia and Posterior Left Atrium

INTRODUCTION

Left atrial radiofrequency catheter ablation (RFA) is gaining acceptance as treatment for drug-refractory atrial fibrillation (AF). This therapy has been associated with esophageal injury and atrioesophageal fistula formation causing death.

METHODS

We describe 3 patients undergoing catheter ablation for AF during real-time monitoring of luminal esophageal temperature.

RESULTS

We observed heating of the esophagus during short duration low power RFA, at either the left or right pulmonary vein ostia. Cryoablation at the pulmonary vein ostium in one patient resulted in esophageal cooling. Furthermore, we observed that fluoroscopic localization of the ablation catheter at a site apparently distant from the esophagus is not adequate to assure avoidance of ablation-induced esophageal heating.

CONCLUSIONS

Real-time monitoring of luminal esophageal position and temperature is feasible, enhances recognition of esophageal heating, and may add useful information beyond that provided by fluoroscopic assessment of esophageal position. There is a potential role for esophageal monitoring to help avoid thermal injury to the esophagus during catheter ablation for atrial fibrillation.

Randomized comparison of encircling and nonencircling left atrial ablation for chronic atrial fibrillation

BACKGROUND

Left atrial (LA) circumferential ablation has been reported to eliminate atrial fibrillation (AF). Whether an ablation without encirclement of the pulmonary veins (PVs) is as effective as LA circumferential ablation is not clear.

OBJECTIVES

The purpose of this study was to compare the efficacy of LA circumferential ablation and nonencircling linear ablation in patients with chronic AF.

METHODS

Eighty patients with chronic AF were randomized to undergo LA circumferential ablation (n = 40) or nonencircling linear ablation (n = 40). In LA circumferential ablation, the PVs were encircled, with additional lines made in the mitral isthmus and posterior wall or roof. In nonencircling linear ablation, 4 +/- 1 ablation lines were created through areas of complex electrograms, with lines in the roof (38), anterior wall (36), septum (40), mitral isthmus (32), and posterior annulus (6). The endpoint of LA circumferential ablation and nonencircling linear ablation was voltage abatement.

RESULTS

LA flutter occurred in 15% after LA circumferential ablation and in 18% after nonencircling linear ablation (P = .8). A repeat ablation procedure was performed for recurrent AF in 7 and 11 patients or for atrial flutter in 6 and 4 patients after LA circumferential ablation and nonencircling linear ablation, respectively (P = .8). At 9 +/- 4 months, the prevalence of AF was 28% in the LA circumferential ablation and 25% in the nonencircling linear ablation group (P = .8). Sixty-eight percent and 60% of patients were in sinus rhythm and free of AF and atrial flutter in the absence of antiarrhythmic drug therapy after LA circumferential ablation and nonencircling linear ablation, respectively (P = .5). There were no complications.

CONCLUSION

Nonencircling linear ablation and LA circumferential ablation are equally efficacious in eliminating chronic AF. However, the advantage of nonencircling linear ablation is that it eliminates the need for ablation along the posterior wall of the LA. Therefore, nonencircling linear ablation may avoid the small but real risk of atrioesophageal fistula formation associated with LA circumferential ablation.

Imaging techniques in cardiac electrophysiology

Modern cardiac electrophysiology procedures include catheter-based arrhythmia ablation and transvenous device implantation, which are highly dependent on accurate, real-time cardiac imaging. With the realization that anatomic structures are critical to successful electrophysiologic procedures, accurately defining a patient's cardiac anatomy has become more important. Fluoroscopy allows for 2D imaging of cardiac structures in real-time, and is used to guide catheter and lead placement, but does not allow for visualization of soft tissues. Intracardiac echocardiography allows for both direct visualization of anatomic structures within the heart and real-time imaging during catheter placement. Despite advances in intracardiac echocardiography catheters that allow for larger windows, the ability to accurately delineate anatomic structures depends on the patient's anatomy and operator experience. Neither of these techniques allows for electrical mapping of the heart; however, both anatomic and electrical intracardiac mapping can be achieved with advanced mapping systems. These systems allow for real-time catheter localization, help elucidate cardiac anatomy, evaluate electrical activation during arrhythmias and guide catheter placement for deliverance of radiofrequency current. More recently, 3D cardiac computed tomography has been used to accurately define intracardiac anatomy; however, catheter tracking and electrical mapping cannot be performed by computed tomography. Mapping systems are now being merged with computed tomography images to produce an accurate anatomic and electrical map of the heart to guide catheter ablations. The objective of this paper is to describe the current imaging and mapping techniques used in electrophysiologic procedures.

Ablation of atrial fibrillation and esophageal injury: Effects of energy source and ablation technique

OBJECTIVE

The aim of this study was the evaluation of histologic changes induced on the esophagus by surgical ablation therapy for atrial fibrillation.

METHODS

Experiments were performed on 39 sheep. Circular lesions were created endocardially or epicardially in the left atrium and at the pulmonary veins by using different energy sources: cryoablation, microwave, laser, and unipolar or bipolar radiofrequency. Temperatures inside the esophagus were measured, and esophageal tissue was investigated macroscopically and histopathologically.

RESULTS

Esophageal damage was seen histologically in 24 of 39 cases. The epithelium was intact in all cases. Unipolar radiofrequency induced the most intensive esophageal lesions in 4 of 6 cases. The affected areas were small (1.56-3.01 mm) but reached deep into the tissue. Endocardial cryoablation resulted in wider lesions (2.01-8.54 mm), which were intensive in only 2 of 6 cases. Epicardial cryoablation and bipolar radiofrequency induced wide (1.11-6.8 mm) but mainly mild alterations. Endocardial and epicardial microwave energy affected the esophagus in single cases, and lesions were small (0.97-2.81 mm). Only in 1 case did laser energy induce a moderate alteration (5.30 mm) of the esophageal wall.

CONCLUSIONS

Esophageal alterations were found in numerous cases. However, marked lesions were especially induced by endocardial unipolar radiofrequency and cryoablation.