Isolation of the Left Subclavian Artery in D-Transposition of the Great Arteries with Right Aortic Arch

Abnormal branching of the aorta associated with the right aortic arch (RAA) has been reported as isolation of left subclavian artery (ILSA), isolation of left common carotid artery, isolation of brachiocephalic artery. ILSA is a rare aortic branch anomaly that originates in the left subclavian artery from the pulmonary artery via ductus arteriosus. Several reports have described ILSA associated with 22q11.2 deletion syndrome and tetralogy of Fallot. Here, we present a very unusual case of RAA with ILSA associated with D-transposition of the great arteries and inferior vena cava interrupted with azygos continuation.     

Characterization of the mitral isthmus for atrial fibrillation ablation using intracardiac ultrasound from within the coronary sinus.

BACKGROUND: Atrial fibrillation (AF) ablation involving the mitral isthmus and/or the coronary sinus (CS) may result in circumflex artery (Cx) or other collateral structure damage. OBJECTIVE: The purpose of this study was to investigate the feasibility of intracardiac echocardiographic (ICE) imaging from within the CS to characterize mitral isthmus anatomy and guide ablation. METHODS: A 9-Fr sheath was introduced into the CS of 30 patients before AF ablation. A 9-Fr rotational ICE catheter was then advanced within the sheath to the distal CS adjacent to the lateral left atrial (LA) wall. Serial cross-sectional images to document the relations of the LA, Cx, CS, esophagus, and pericardium were obtained at multiple points within the CS during a pullback to the CS ostium. RESULTS: The Cx was identified in 62/150 positions in 25/30 patients. The median (range) of the LA-Cx distance was 3.3 mm (0.7-19.6 mm), and the median CS-Cx distance was 2.0 mm (0.4-9.7 mm). The esophagus was seen in 36/150 positions in 17/30 patients. The median CS-esophagus distance was 4.0 mm (1.4-16.2 mm). The proximity of the Cx and esophagus to the LA and CS varied considerably. The median CS-mitral annulus distance was 11.9 mm (4.1-21.6 mm). After CS cannulation, the ICE imaging took 5 +/- 2 minutes and required 120 +/- 60 seconds of fluoroscopy. CONCLUSIONS: Mitral isthmus anatomy can be accurately characterized by rotational ICE imaging from within the CS. There is great variability in the location and proximity of the Cx, CS, esophagus, and pericardium to the LA. Real-time identification of these structures could help to plan ablation strategies and potentially reduce complications.     

Simple and efficient identification of conduction gaps in post-ablation recurring atrial flutters.

AIMS: Cavo-tricuspid isthmus (CTI) radiofrequency (RF) ablation is a curative therapy for common atrial flutter (AFl), but is associated with a recurrence rate of 5-26%. Although complete bidirectional conduction block is usually achieved, the recurrence of AF is due to recovered conducting isthmus tissue through which activation wavefronts pass. We evaluated a simple and efficient electrophysiological strategy, which pinpoints the ablation target. METHODS AND RESULTS: Twenty-five patients (19 men), mean age 61 +/- 6, with recurrent AFl required a repeat ablation, 250 +/- 160 days after a successful RF CTI procedure. Transverse CTI conduction was monitored during AFl or coronary sinus (CS) pacing by a 24-pole mapping catheter positioned in the right atrium (RA), with the distal poles in the CS, proximal poles on the lateral RA, and intermediate poles on the CTI. A slow conduction area traversing the CTI (velocity, 37 +/- 22 vs. 98 +/- 26 cm/s on either side, P < 0.05) and a lower potential amplitude than at both sides (0.2 +/- 0.15 vs. 0.5 +/- 0.5 mV, P < 0.05), defined by a bayonet-shaped depolarization sequence, were considered to represent the incomplete line of block (InLOB). An ablation catheter was progressively dragged up to this InLOB, from the tricuspid annulus to the inferior vena cava, analysing the widely separated double potentials (DPs) until these coalesced. In nine patients (35%), the target conduction gap was a coalesced fractionated atrial potential within the InLOB (duration, 77 +/- 12 ms), and in 16 patients (65%), a narrow DP toward the healthy margins of this InLOB (duration, 28 +/- 15 ms). Adopting this strategy yields 100% successful re-ablation of recurring AFl leading to bidirectional block, with a mean 2.7 +/- 1.4 RF applications. CONCLUSION: Transverse CTI mapping precisely locates the InLOB and helps find conduction gaps along the CTI in re-ablation procedures for common AFl.     

Phased-array intracardiac echocardiography for defining cavotricuspid isthmus anatomy during radiofrequency ablation of typical atrial flutter

INTRODUCTION: Cavotricuspid isthmus (CTI) topography includes ridges, pouches, recesses, and trabeculations. These features may limit the success of radiofrequency ablation (RFA) of typical atrial flutter (AFL). The aim of this study was to assess the utility of phased-array intracardiac echocardiography (ICE) for imaging the CTI and monitoring RFA of AFL. METHODS AND RESULTS: Fifteen patients (mean age 64 +/- 9 years) underwent ICE assessment (imaging frequency 7.5-10 MHz) before and after RFA of AFL. The ICE catheter was positioned at the inferior vena cava-right atrial junction and the following parameters were measured: (1) CTI length from the tricuspid valve to the eustachian ridge; (2) extent of CTI pouching; and (3) thickness pre/post RFA of the anterior, mid, and posterior CTI. CTI length was 35 +/- 6 mm at end-ventricular systole but shorter (30 +/- 6 mm) and more pouched at end-ventricular diastole (P = 0.02). A pouch or recess was seen in 11 of 15 patients (mean depth 6 +/- 2 mm). The septal CTI was more pouched than the lateral CTI, but the latter had more prominent trabeculations. Trabeculations were seen in 10 of 15 patients, and at these locations the CTI was 4.6 +/- 1 mm thick. Anterior, mid, and posterior CTI thickness pre-RFA was 4.1 +/- 0.8, 3.3 +/- 0.5, and 2.7 +/- 0.9 mm, respectively (P < 0.001 by analysis of variance). ICE guided RFA away from unfavorable CTI features (recesses/thick trabeculations). RFA applications created discrete CTI lesions that coalesced, forming diffuse CTI swelling. Post-RFA thickness was as follows: anterior 4.8 +/- 0.8 mm (P = NS vs pre); mid 3.8 +/- 0.8 mm (P = 0.05 vs pre); and posterior 3.8 +/- 0.8 mm (P = 0.02 vs pre). CONCLUSION: Phased-array ICE permits novel real-time CTI imaging with excellent endocardial resolution and may facilitate RFA of AFL.     

Atrial morphology in hearts with congenitally corrected transposition of the great arteries: implications for the interventionist

INTRODUCTION: In view of the possible need for septal puncture to ablate left-sided lesions and the occasional difficulty in coronary sinus (CS) cannulation, we investigated relevant anatomic features in the right atrium of hearts with congenitally corrected transposition of the great arteries (ccTGA). METHODS AND RESULTS: Nine hearts with ccTGA and an intact atrial septum and eight weight-matched normal hearts were examined by studying the "septal" aspect of the right atrium with reference to the oval fossa (OF). The anterior margin was arbitrarily measured as the shortest distance from the OF to the superior mitral/tricuspid annulus. The posterior margin was measured from the OF to the posterior-most edge of the right atrial "septal" surface. The total "septal" surface width was measured at the middle of the OF. The stretched OF dimensions and CS isthmus length were noted. Mann-Whitney test was used to compare absolute and indexed dimensions, i.e.. normalized to total width. The posterior margin in hearts with ccTGA was shorter than in controls (6.3+/-2.4 mm vs 11+/-1.9 mm, P < 0.001; normalized margin P = 0.09). The CS isthmus also was significantly shorter (5.3+/-2.7 mm vs 11.4+/-2.2 mm, P < 0.001). In two hearts with ccTGA, the CS opening into the right atrium was on the same side of the eustachian valve as the inferior caval vein. CONCLUSION: The shorter posterior "septal" margin in hearts with ccTGA may increase the risk of exiting the heart while performing septal puncture when pointing the needle posteriorly. The shorter CS isthmus and the abnormal location of the CS opening in some of these hearts are important when contemplating radiofrequency ablation in this area.     

Use of double-potential barrier to identify functional isthmus at the cavotricuspid isthmus for facilitating catheter ablation of isthmus-dependent atrial flutter

INTRODUCTION: The aim of the study was to identify an alternative target for more effective radiofrequency catheter ablation (RFCA) of isthmus-dependent atrial flutter (AFL). METHODS AND RESULTS: We hypothesized that a functional isthmus formed by preexisting double potential barrier at the cavotricuspid isthmus (CTI) could serve as a new target site for facilitating RFCA of AFL. Forty-three consecutive patients with recurrent isthmus-dependent AFL were studied using three-dimensional navigated magnetic mapping and ablation technique. Twenty patients (47%, group A) were shown to have a narrower functional channel at the CTI (functional isthmus). The remaining 23 patients did not have this feature (53%, group B). In group A, double potentials were clustered near the border of the inferior vena cava (IVC) of the CTI and served as a functional channel along the tricuspid annulus (TA). The interspike interval of double potentials was 87 +/- 26 ms near the IVC border and 45 +/- 17 ms (P < 0.0001) near the TA border of CTI. RFCA targeting at the functional isthmus in group A resulted in interruption of bidirectional transisthmus conduction with fewer radiofrequency pulses (6.7 +/- 4.7 in group A vs 21.1 +/- 17.1 pulses in group B, P < 0.001), shorter ablation line (11.6 +/- 4.0 mm vs 37.8 +/- 7.2 mm, P < 0.0001) with no arrhythmia recurrence. These functional isthmuses were found to be located at the lateral third of CTI in 12 patients, middle third in 7, and medial third in 1. This finding is different from that obtained by the conventional method in group B (lateral in 5, middle in 16, medial in 2, P < 0.038). CONCLUSION: In our study, a functional, rather than anatomic, isthmus formed by preexisting double-potential barrier at the CTI was identified in 47% of patients with isthmus-dependent AFL. It is a useful guide to facilitate RFCA of isthmus-dependent AFL.     

Correlation between electrogram morphology and standard criteria to validate bidirectional cavotricuspid block in common atrial flutter ablation.

AIM: Assessment of a bidirectional conduction block within the cavotricuspid isthmus (CTI) is critical during radiofrequency (RF) atrial flutter (AF) ablation. We investigated the use of bipolar atrial electrogram (BAE) morphology as an additional criterion identifying CTI block and tested it against two recognized criteria: differential pacing and reversal of the right atrial depolarization sequence during coronary sinus (CS) pacing. METHODS AND RESULTS: An RF ablation procedure was performed during 600 ms CS pacing in 100 consecutive patients with a common AF. BAE recorded along the CTI were continuously monitored. CTI conduction block was achieved by RF ablation in all patients and a clear change in BAE polarity in the Electrogram recorded by the dipoles located on the CTI and immediately lateral to the intended line of block (RS to QR pattern) associated with a confirmed CTI conduction block was observed in all cases. BAE morphology changes predicted bidirectional CTI conduction blocks with a 100% positive and a 100% negative predictive value. At a mean follow-up of 33 +/- 11 months, there was a 5% AF recurrence rate. CONCLUSIONS: Our study suggests that morphological changes in BAE recorded at sites lateral and adjacent to the target line of block may be used as a unique and robust criterion to validate CTI conduction block during AF ablation procedure.     

Percutaneous revascularization of atherosclerotic obstruction of aortic arch vessels

OBJECTIVES: To compare stenting of aortic arch vessel obstruction with surgical therapy and to establish recommendations for treatment. BACKGROUND: Though surgery has been considered to be the procedure of choice for subclavian and brachiocephalic obstruction, little work has been done to compare it with stenting. METHODS: Eighteen patients with symptomatic aortic arch vessel stenosis or occlusion were treated with stenting, followed by periodic clinical follow-up and noninvasive arterial Doppler studies. Data were compared with the results as shown in a systematic review of a published series of surgery and stenting procedures which included comparison of technical success, complications, mortality and patency. RESULTS: Primary success in our series was 100% with improvement in mean stenosis from 84+/-11% to 1+/-5% and mean arm systolic blood pressure difference from 44+/-16 mm Hg to 3+/-3 mm Hg. There were no major complications (death, stroke, TIA, stent thrombosis or myocardial infarction). At follow-up (mean 17 months), all patients were asymptomatic with 100% primary patency. Literature review demonstrates equivalent patency and complications in the other published series of stenting. In contrast, there was a similar patency but overall incidence of stroke of 3+/-4% and death of 2+/-2% in the published surgical series. CONCLUSIONS: Subclavian or brachiocephalic artery obstruction can be effectively treated by primary stenting or surgery. Comparison of stenting and the surgical experience demonstrates equal effectiveness but fewer complications and suggests that stenting should be considered as first line therapy for subclavian or brachiocephalic obstruction.     

Relationship between perimitral and peritricuspid conduction times

BACKGROUND: Conduction block across the left mitral isthmus (LMI) seems more challenging to achieve and validate compared with the cavotricuspid isthmus (CTI). OBJECTIVE: This study sought to investigate the relationship between peritricuspid and perimitral circuit times in the same patient and to compare the difficulty in achieving the CTI and LMI linear lesions. METHODS: We retrospectively studied 122 consecutive patients (46 paroxysmal and 76 persistent) admitted for atrial fibrillation ablation or subsequent atrial macroreentry who underwent both CTI and LMI ablation. The peritricuspid and perimitral conduction times were measured after validation of bidirectional block across their respective line by pacing from the septal side of the CTI or LMI and recording of the second late potential on the line of block. Atrial dimensions were measured by standard transthoracic echocardiographic techniques. RESULTS: The mean peritricuspid and perimitral times were 180 +/- 35 ms (range 120 to 300) and 189 +/- 42 ms (range 120 to 322), respectively, with a mean difference of 7 +/- 32 ms (-70 to 95). The correlation between both circuit times was highly significant (r = 0.621, P < .001). In 84 patients (68%), the perimitral time was within 30 ms of the peritricuspid time. In the remaining patients, only 12 (10% of the total patients) had a shorter perimitral time compared with peritricuspid time. Radiofrequency energy delivered was significantly longer for LMI (15 +/- 7 min [range 7 to 33]) compared with CTI (7 +/- 4 min [range 3 to 17]) (P = .005). CONCLUSION: The peritricuspid and perimitral circuit times are strongly correlated. In 90% of patients, the perimitral conduction time is within 30 ms or longer than the peritricuspid time. In addition, both circuit times are always > or = than 120 ms. Compared with the left mitral isthmus line, the CTI line is significantly easier to perform.     

Characteristics of right atrial activation during coronary sinus pacing

INTRODUCTION: Anatomic and electrical connections between the left atrium and right atrium (RA) have been described. The relationship between coronary sinus (CS) pacing site and RA activation has not been examined. METHODS AND RESULTS: Fifteen anesthetized swine underwent high-density noncontact mapping of the RA during pacing from up to five different sites within the CS. Isopotential mapping identified the site of earliest RA depolarization and the pattern of subsequent activation. Hearts were excised and endocardial dissection performed. Earliest RA activation occurred at the CS os with proximal CS pacing sites and at Bachmann's bundle at distal pacing sites. The mean depth at which a shift in earliest RA activation site occurred was 46 +/- 13 mm (range 21 to 63 mm). RA activation times following earliest activation at the CS and Bachmann's bundle were 40 +/- 4 msec and 51 +/- 6 msec (P < 0.002). Conduction delay or block was recorded at the lateral cavotricuspid isthmus, terminal crest, and tendon of Todaro. Latest RA activation always occurred in the high anterolateral atrium after ascending the anterolateral wall. The lateral RA was activated by the wavefront that traversed the posterior wall rather than by the wavefront crossing the cavotricuspid isthmus, even with earliest RA activation at the CS os. CONCLUSION: The site of earliest RA activation during CS pacing is dependent upon the pacing depth within the CS. In the porcine heart, areas of conduction delay influence RA activation patterns and timings. These findings may have implications for patients undergoing assessment of radiofrequency ablation of atrial flutter.     

Visualisation of intra-cardiac structures and radiofrequency lesions using intracardiac echocardiography.

AIMS: Fluoroscopy does not allow identification specific anatomical landmarks during electrophysiological studies. Intra-cardiac echocardiography permits visualization of these structures with excellent accuracy, but the optimal method has not been fully described. The aim of this study was to assess the capability of intra-cardiac echocardiography for the visualization of such structures using two different approaches. We also assessed its capability for the evaluation of radio frequency lesions 20 min after catheter ablation of the cavo-tricuspid isthmus. METHODS: Intra-cardiac echocardiography was performed using a 9 MHz rotating transducer in eight consecutive patients (age range: 37-76 years) after radio frequency ablation of the cavo-tricuspid isthmus. The ultrasound catheter was inserted through the femoral vein into the superior vena cava and was pulled back to the inferior vena cava. The echo catheter was then reinserted through the subclavian vein and advanced into the right ventricular apex and was pulled back from the right ventricular to the superior vena cava. Qualitative evaluation and intra-cardiac measurements were performed off-line. RESULTS: The fossa ovalis, the tricuspid valve, and the terminal crest were visible in all patients regardless of the method of introduction of the echo catheter. Left-sided structures were less accurately seen by intra-cardiac echocardiography. The horizontal diameter of the fossa ovalis was 8.9+/-1.8mm. The cavo-tricuspid isthmus was visible using the femoral approach in three patients. The isthmus could be visualized in all patients, and in three patients together with the ostium of the coronary sinus, using the subclavian approach. radio frequency lesions were not visible 20 min after ablation. Additionally, both the left and right ventricles could be seen using the subclavian approach. CONCLUSIONS: The subclavian approach is feasible, safe and superior to visualize the isthmus. Twenty minutes after radio frequency ablation of the cavo-tricuspid isthmus radio frequency lesions are not visible using intra-cardiac echocardiography.     

Evaluation of an individualized strategy of cavotricuspid isthmus ablation as an adjunct to atrial fibrillation ablation

Objectives: To evaluate supplementary cavotricuspid isthmus (CTI) ablation as an adjunct to atrial fibrillation (AF) ablation in selected patients.
Background: It is unclear whether routine CTI ablation is beneficial in all patients undergoing AF ablation.
Methods and Results: In patients undergoing AF ablation, additional CTI block was created only for those with typical atrial flutter (Afl) before or during the ablation. Out of 188 consecutive patients (108 male, 56 ± 9 years), 75 underwent CTI ablation (Group CTI+) and left atrial (LA) ablation (circular mapping-guided extensive pulmonary vein isolation in all and linear LA ablation when required), while 113 underwent LA ablation alone (Group CTI−). Group CTI+ patients had smaller LA and less frequently persistent/permanent AF and linear LA ablation. Over a follow-up of 30 ± 10 months, complications (4% vs 5%, P = NS), typical Afl occurrence (1.3% and 2.6%, P = NS) and AF recurrence (25% and 28%, P = NS) were similar. Atypical Afl was more common in Group CTI− (4 vs 14%, P = 0.026). Eighty-two percent and 79% of patients in Groups CTI+ and CTI−, respectively, remained arrhythmia free in stable sinus rhythm without antiarrhythmic drug treatment (P = NS).
Conclusions: Avoiding supplementary CTI ablation in AF ablation patients without evidence of typical flutter does not result in a higher incidence of typical Afl. Despite more persistent/permanent AF and larger LA in patients without evidence of typical flutter, a strategy of selective supplementary ablation resulted in similar and low AF recurrence rates in the group without CTI ablation compared with the group with CTI ablation.     

Unusual collateral vessel from right subclavian vein to left atrium,a rare complication of superior vena cava obstruction

The most commonly reported collateral systems in the setting of superior vena cava obstruction are azygos venous system, vertebral venous system, external and internal thoracic venous system based on McLntire and Sykes classification. A 49‐year‐old female with renal disease complained dyspnea on exertion. Transesophageal echocardiography showed significant mitral annular calcification, large multi‐lobulated mass at posterior aspect of RA, and complete obstruction of superior vena cava by thrombus formation. Computed tomography angiography showed a collateral vein to the left atrium (LA) roof. This case report is the first one which shows development of collateral vein from right subclavian to LA.     

Functional anatomy of bronchial veins

The amount of bronchial arterial blood that drains into the systemic venous system is not known. Therefore, in this study we further delineated the functional anatomy of the bronchial venous system in six adult, anesthetized, and mechanically ventilated sheep. Through a left thoracotomy, the left azygos vein was dissected and the insertion of the bronchial vein into the azygos vein was identified. A pouch was created by ligating the azygos vein on either side of the insertion of the bronchial vein. A catheter was inserted into this pouch for the measurement of bronchial venous occlusion pressure and bronchial venous blood flow. An ultrasonic flow probe was placed around the common bronchial branch of the bronchoesophageal artery to monitor the bronchial arterial blood flow. Catheters were also placed into the carotid artery and the pulmonary artery. The mean bronchial blood flow was 20.6+/-4.2mlmin(-1) (mean+/-SEM) and, of this, only about 13% of the blood flow drained into the azygos vein. The mean systemic artery pressure was 72.4+/-4.1mmHg whereas the mean bronchial venous occlusion pressure was 38.1+/-2.1mmHg. The mean values for blood gas analysis were as follows: bronchial venous blood pH=7.54+/-0.02, PCO(2)=35+/-2.6, PO(2)=95+/-5.7mmHg; systemic venous blood-pH=7.43+/-0.02, PCO(2)=48+/-3.2, PO(2)=42+/-2.0mmHg; systemic arterial blood-pH=7.51+/-0.03, PCO(2)=39+/-2.1, PO(2)=169+/-9.8mmHg. We conclude that the major portion of the bronchial arterial blood flow normally drains into the pulmonary circulation and only about 13% drains into the bronchial venous system. In addition, the oxygen content of the bronchial venous blood is similar to that in the systemic arterial blood.     

Multidetector 16-slice CT scan evaluation of cavotricuspid isthmus anatomy before radiofrequency ablation

INTRODUCTION: The anatomy of the cavotricuspid isthmus (CTI) is an important determinant of the ease of radiofrequency ablation. We evaluated the anatomy of the region with a multidetector 16-slice computed tomography (CT) scan and correlated this with subsequent procedural difficulty. METHODS: Twenty-nine patients (mean age 64 +/- 15 years) with typical atrial flutter or paroxysmal atrial fibrillation underwent ablation of the CTI. A multidetector 16-slice CT scan with contrast injection was performed in all before the procedure. RESULTS: The CTI showed marked variability as evidenced by the following measurements: length (8.2 to 32.2 mm), width (26 to 56.5 mm), depth (0 to 11 mm), thickness (0.2 to 7.5 mm), the angle between the inferior vena cava and the CTI (59.9 to 129.5 degrees ), and the length of the Eustachian valve (4.8 to 26.1 mm) present in 72% of patients. The appearance of the CTI was classified as follows into three categories: concave (72%), flat (17%), or with a sub-Eustachian recess (28%). Procedures were classified as difficult in case of failure to achieve bidirectional block or if radiofrequency duration was greater than 99% confidence interval. In the multivariate analysis, a significant correlation was present between the thickness of the CTI and procedural difficulty (p = 0.0005). CONCLUSIONS: The multidetector 16-slice CT scan with contrast injection accurately evaluates the anatomy of the CTI. The only independent anatomic parameter that predicts a more difficult procedure is the thickness of the CTI.     

Anatomic relationship of the esophagus and left atrium: implication for catheter ablation of atrial fibrillation

STUDY OBJECTIVES: Atrioesophageal fistulas have been reported to be a lethal complication following catheter ablation of atrial fibrillation (AF). The purpose of this study was to investigate the relationship between the esophagus and posterior left atrium (LA) and provide the anatomic information necessary to minimize the risk of esophageal injury during AF ablation. METHODS AND RESULTS: Forty-eight patients (43 men; mean +/- SD age, 59 +/- 12 years) with drug-refractory paroxysmal AF and 32 control subjects (26 men; mean age, 60 +/- 9 years) were included. All underwent a CT scan for delineation of the relationship between the esophagus and posterior LA. In the paroxysmal AF group, two major types of esophageal routes were demonstrated. Type 1 routes were found in 42 patients with the lower portion of esophagus close to the ostium of the left inferior pulmonary vein (LIPV), including three subtypes of courses according to the proximity to the left superior pulmonary vein (PV) and LIPV. Type 2 routes were found in six patients with the lower portion of esophagus close to the ostium of the right inferior pulmonary vein (RIPV), including three subtypes of courses according to the proximity to the right superior PV and RIPVs. The mean shortest distance of the esophagus to the four individual PVs significantly differed between type 1 and type 2: 28.4 +/- 6.1 mm vs 10.5 +/- 5.7 mm (to the right superior), 19.6 +/- 7.0 mm vs 3.7 +/- 3.4 mm (to the right inferior), 10.1 +/- 3.4 mm vs 22.8 +/- 4.2 mm (to the left superior), and 2.8 +/- 2.5 mm vs 18.7 +/- 5.2 mm (to the left inferior), respectively (p < 0.001 for all). Contact of the esophagus and middle part of posterior LA was observed in each patient. However, direct contact of the aorta with the posterior LA wall was more frequent in type 2 than in type 1 (p = 0.001). The clinical characteristics, type of esophageal routes, distance from the esophagus to the four PVs, and diameter of the thoracic cage, LA, and aorta in the control group were similar to those in the AF group (p > 0.05 for all). CONCLUSION: Although the anatomic relationship between the esophagus and LA posterior wall varied widely, two major patterns of esophageal routes could be depicted. This information is important for deciding the location of the ablation lesions around the PV ostia and LA and for avoiding the potential risk of esophageal injury.     

Differential densities of muscarinic acetylcholine receptor and I(K,ACh) in canine supraventricular tissues and the effect of amiodarone on cholinergic atrial fibrillation and I(K,ACh)

BACKGROUND: Vagal nerve plays an important role in the induction and maintenance of atrial fibrillation (AF). This study investigated the differential densities of M2 receptor and acetylcholine-induced inward rectifier K+ current (I(K,ACh)) in atrial appendage, atrium, pulmonary vein (PV) and super vena cava (SVC) to discuss the role of atrial appendage and PV in cholinergic AF. METHODS AND RESULTS: In 10 dogs, action potential duration was determined at 24 sites during bilateral cervical vagal stimulation and amiodarone administration. AF could be induced at first in right atrial appendage (RAA) and right atrium (RA) without left atrial appendage (LAA) and left atrium (LA). Amiodarone decreased the initiation of AF in vivo. Western blot and patch clamp were used to determine M2 receptor and I(K,ACh) in RAA, LAA, RA, LA, PV and SVC. The densities of M2 receptor and I(K,ACh) in LAA, RAA and LA were higher than that in RA, PV and SVC (21.34 +/- 0.92 vs. 8.24 +/- 0.45 pA/pF, p < 0.05). Furthermore, the densities of the M2 receptor and I(K,ACh) in LAA and RAA were higher than that in LA (21.34 +/- 0.92 vs. 14.17 +/- 0.65 pA/pF, p < 0.05). After amiodarone administration, densities of I(K,ACh) in LA and RA were not different, but densities of I(K,ACh )were also less in atrium than in atrial appendage. CONCLUSIONS: Densities of the M2 receptor and I(K,ACh) are higher in atrial appendage than other sites. Atrial appendage perhaps plays an important role in initiation of cholinergic AF. However, PV and SVC less often play an important role in vagotonic paroxysmal AF. Reduced dispersion of I(K,ACh) is the mechanism for amiodarone to therapy AF.     

Changes in left atrial anatomy due to respiration: impact on three-dimensional image integration during atrial fibrillation ablation

Introduction: Patient respiration influences the accuracy of image integration approaches used during atrial fibrillation (AF) ablation procedures. We assessed both absolute and relative changes in left atrial (LA) and pulmonary venous (PV) anatomy due to respiration and their implications for 3D image integration.
Methods and Results: Intensity-based segmentation of the LA and PVs was performed on cardiac computed tomography (CT) images obtained during both inspiration and expiration in 16 patients referred for AF ablation. A 3D LA-PV surface model was reconstructed for each respiratory phase. Absolute and relative respiratory motion components were evaluated from corresponding landmarks in both models. The mean 3D respiratory motion distance for all four PVs was 19 ± 9 mm. The most important motion component was in the inferior direction, with a mean inferior motion distance of 15 ± 8 mm. The mean 3D respiratory motion of the PV centers due to relative geometrical changes was small at the ostial level (2.6 ± 1.4 mm, 95% CI 2.3-3.0 mm) but significantly larger at the level of the first PV bifurcation (4.0 ± 2.3 mm, 95% CI 3.4-4.6 mm, P < 0.001). Relative geometrical changes of the LA body were most pronounced in regions near the mitral valve, resulting in a changed configuration of the mitral annulus during inspiration.
Conclusions: Respiration causes important movements of the PVs and LA. Relative changes in LA–PV geometry are most pronounced in the distal PVs and in the LA body near the mitral valve. Therefore, these regions should be avoided during registration of pre- and per-procedural images unless they are acquired in the same phase of respiration.