Background
Computed tomography (CT) is the gold standard for assessing pulmonary vein (PV) anatomy and stenosis after ablation for atrial fibrillation (AF), but radiation exposure can be a concern. Transesophageal echocardiography (TEE) provides anatomic and functional assessment of the PVs, although no study has prospectively compared findings on TEE with those on CT.
Methods
The Role of Transesophageal Echocardiography Compared to Computed Tomography in Evaluation of Pulmonary Vein Ablation for Atrial Fibrillation (ROTEA) study was a prospective, single-blinded observational study of patients with paroxysmal or persistent AF undergoing ablation. TEE and CT were performed immediately before and 3 months after AF ablation. The study included 43 patients (84% men; mean age, 56 ± 11 years).
Results
In the preprocedural study, TEE identified 98% of PVs with adequate Doppler measurements obtained. After ablation, no moderate or severe PV stenosis was detected on CT, and a 30% to 50% reduction in luminal diameter was seen in 5% of studied veins. Functional PV stenosis by pulsed-wave Doppler was seen in two veins on TEE. PV diameters decreased after ablation by 0.20 ± 0.03 and 0.22 ± 0.03 cm as measured by CT and TEE, respectively ( P < .001). However, TEE underestimated PV ostial dimensions compared with CT, especially for the inferior PVs. Severe spontaneous echo contrast and low left atrial appendage emptying velocities, were identified in 10% of patients in sinus rhythm after ablation.
Conclusions
In the ROTEA study, TEE was feasible in assessing PVs before and after ablation, providing both anatomic and functional information that complemented CT. PV ostial dimensions after ablation can be monitored using either modality, although TEE underestimates PV dimensions, especially for the inferior veins.
Catheter-based radiofrequency ablation, or pulmonary vein (PV) isolation, is increasingly used in patients with atrial fibrillation (AF). Imaging modalities, including computed tomography (CT) and transesophageal echocardiography (TEE), are used to assess the anatomy and physiology of the left atrium and PVs and are integral to the success of the procedures. Accurate information on PV anatomy is critical in preprocedural planning. Anatomic variation in PV ostia number and position has been shown to influence the success of the ablation procedure. Imaging is also important in assessing the rare but important complications of PV stenosis and thromboembolism.
CT has superior spatial resolution without the limitation of acoustic windows and allows the accurate assessment of left atrial (LA) cavity size as well as PV ostial configuration and dimension. CT-derived data are routinely used in the preprocedural, three-dimensional LA reconstruction to guide AF ablation. Although CT is generally considered the imaging modality of choice for assessing PV stenosis, the cumulative radiation from serial computed tomographic scans and contrast exposure may be an important consideration for many patients, especially younger female patients. Conversely, TEE is the gold standard for excluding thrombus within the left atrium or LA appendage (LAA) before the ablation procedure. For PV stenosis, TEE provides additional functional assessment of stenosis, with pulsed-wave and color Doppler echocardiography showing a combination of elevated PV flow velocities and the presence of turbulent flow and spectral broadening. Published studies comparing TEE with CT for the evaluation of PV stenosis were performed retrospectively. In this prospective study, we compared TEE with CT for the evaluation of PV anatomy and function, both before and after PV ablation for AF.
Methods
The Role of Transesophageal Echocardiography Compared to Computed Tomography in Evaluation of Pulmonary Vein Ablation for Atrial Fibrillation (ROTEA) study was a prospective, single-blinded observational study evaluating TEE in patients undergoing PV ablation at the Cleveland Clinic. Patients gave written informed consent, and the protocol and study were approved by the Cleveland Clinic Institutional Review Board.
Study Population
Between January 2005 and August 2007, patients undergoing PV ablation for drug-resistant paroxysmal or persistent AF who were willing to undergo CT and TEE before and after AF ablation were invited to participate in the study. Patients were excluded if they could not return to the Cleveland Clinic for follow-up or had contraindications to esophageal intubation, renal impairment, LAA thrombus, moderate or severe mitral stenosis or regurgitation, cardiothoracic surgery within 6 months, or history of infection within 1 month of the procedures.
All patients underwent clinical examinations, transthoracic echocardiography (TTE), TEE, and cardiac CT within 24 hours of the ablation procedure. Patients returned at 3 months for clinical follow-up and repeat TTE, TEE, and cardiac CT. CHADS 2 scores were determined in all patients.
Echocardiography
TEE was performed by experienced operators (A.L.K., B.S.L., R.J.C.) using an Acuson Sequoia C256 machine (Siemens Medical Solutions USA, Inc., Mountain View, CA) using a multiplane transesophageal echocardiographic probe (TE-V5M) or a Philips 7500 machine (Philips Medical Systems, Andover, MA) using a multiplane (S7-2) probe. TEE was performed under sedation of intravenous midazolam and fentanyl, titrated to each patient’s level of tolerance. The operators were blinded to the results of CT. Specific imaging included assessment of (1) the left atrium at 0° and 90° for LA dimensions, LA area, spontaneous echo contrast (SEC), and thrombus; (2) the LAA at 0°, 45°, 90°, and 135° for dimensions, area, SEC, and thrombus; (3) pulsed-wave Doppler imaging of LAA emptying and filling velocities; and (4) pulsed-wave Doppler imaging of the PVs. Pulsed-wave Doppler of PV flow was measured with a 5-mm sample volume. The peak systolic, diastolic, and atrial reversal velocities were recorded for each vein. The configuration of the PV ostia into the left atrium was identified, and measurement of the maximum diameter was made of each vein ostium. Careful interrogation of the PV ostia anatomy and diameters was made from multiple imaging planes, assessed as best as possible. The views used for PV anatomy are standardized for each study, before and after ablation, as well as across readers.
TTE was performed by an experienced research sonographer. Standard views for LA and left ventricular volume measurement, as well as an ejection fraction using Simpson’s biplane method, were made according to recognized guidelines. In addition, pulsed-wave Doppler imaging of transmitral inflow and pulsed wave tissue Doppler imaging of the septal and lateral mitral annulus were performed. Measurements were indexed for body surface area.
Echocardiographic measurements were recorded over 2-sec digital loops for patients with AF and three-beat loops for patients in normal sinus rhythm. For each measurement, three to five recorded loops were obtained. All studies were analyzed by experienced readers.
CT
Computed tomographic scans of the PVs were performed according to a standardized protocol with retrospective electrocardiographic gating in late systole (40% of the cardiac cycle). A three-dimensional volume acquisition was obtained using a Siemens SOMATOM Sensation 64-slice or Definition Dual Source 64-slice CT scanner (Siemens Medical Solutions USA, Inc.). Typical scan parameters were 120 kV, 100 mAs, and 165-msec temporal resolution, with images acquired with a 1.5-mm slice thickness without β-blockade. Retrospective electrocardiographic gating was used. With offline multiplanar reconstructions to obtain views of the PVs in a true en face short-axis plane, PV ostial diameters were measured in the major and minor axes ( Figure 1 ). The severity of PV stenosis was defined as a percentage reduction in area and graded as follows: severe (>70%), moderate (50%–70%), mild (30%–50%), or none (0%–30%), on direct comparison with an appropriate proximal or distal reference segment of the interrogated vein. Mean ostial diameters were calculated by averaging the diameters measured in the major and minor axes. Luminal area was calculated by tracing the lumen of the reconstructed short-axis image.
; view video clip online). On CT, multiplanar reconstruction of the LIPV in a patient demonstrates the oval shaped vein, with the major axis ( green arrow ) most commonly in the craniocaudal orientation and minor axis ( red arrow ) in the transaxial orientation. On TEE, the ostium of the vein can be measured after careful interrogation and alignment from different angles. Ao , Aorta; LA , left atrium. Ablation Procedure
Details of the ablation procedure have been described previously. Briefly, the ablation technique involves radiofrequency isolation of the PV antrum and the superior vena cava guided by intracardiac echocardiography and CARTO mapping (Biosense Webster, Diamond Bar, CA). All procedures were performed under heparin anticoagulation, with a target activated clotting time of 350 sec. Oral anticoagulation was continued until evaluation in the clinic 3 months after the procedure.
Statistical Analysis
All continuous variables were expressed as mean ± SD and categorical variables as proportions. Paired Student’s t tests were used for intergroup comparisons for continuous variables. Chi-square tests were used for intergroup comparisons of categorical variables. P values < .05 were considered significant, and all tests were two sided. All data analysis was performed using JMP version 8.0.1 for Windows (SAS Institute Inc., Cary, NC).
Results
Patient Demographics
We enrolled 43 patients (84% men; mean age, 56 ± 11 years) with paroxysmal or persistent AF undergoing PV ablation in the study. They completed TTE, TEE, and cardiac CT before PV ablation. At 3 months, 37 patients completed follow-up cardiac CT, and 33 patients returned for TEE. The mean follow-up duration was 121 ± 59 days.
Study population baseline characteristics ( Table 1 ) indicated that 60% had prior direct current cardioversion, 35% had prior PV ablation procedures, and 19% had prior systemic thromboembolism. The median CHADS 2 score was 1.1, and the mean left ventricular ejection fraction was 50 ± 11%. Between the paroxysmal AF and persistent AF groups, the baseline variables differed in that patients with persistent AF had lower baseline left ventricular ejection fractions (48 ± 10% vs 54 ± 9%, P = .032) and were more likely to have had prior cardioversion (83% vs 35%, P = .002). At the 3-month follow-up visit, 30 patients (71%) were in sinus rhythm, eight (19%) were in paroxysmal or persistent atrial flutter, and four (10%) had recurrence of AF
| Parameter | Value |
|---|---|
| Age (y) | 56 ± 11 |
| Men | 36 (86%) |
| Height (cm) | 180 ± 7 |
| Body mass index (kg/cm 2 ) | 30 ± 5 |
| Clinical characteristics | |
| CHADS 2 score | 1.1 ± 1.1 |
| Age > 75 y | 3 (7%) |
| Hypertension | 18 (42%) |
| Diabetes mellitus | 6 (14%) |
| Coronary artery disease | 10 (23%) |
| Congestive heart failure | 5 (12%) |
| Peripheral vascular disease | 1 (2%) |
| Previous embolism | 8 (19%) |
| AF | |
| Duration of AF (y) | 7 ± 6 |
| Persistent AF at the time of ablation | 23 (53%) |
| Paroxysmal AF at the time of ablation | 20 (47%) |
| Previous direct current cardioversion | 26 (61%) |
| Previous PV ablation | 15 (35%) |
| Ablation success at 3 months | 30 (71%) |
| TTE | |
| LV ejection fraction (%) | 50 ± 11 |
| LV end-diastolic dimension (cm) | 4.9 ± 0.6 |
| LV end-systolic dimension (cm) | 3.4 ± 0.7 |
| LA area (cm 2 ) | 27 ± 9 |
| LA volume index (cm 3 /cm 2 ) | 37 ± 15 |
| Right atrial area (cm 2 ) | 23 ± 6 |
| E-wave deceleration time (msec) | 208 ± 81 |
| E/e′ averaged | 10.7 ± 6.3 |
PV Anatomy: CT Versus TEE
Anatomic Variations
On preablation cardiac CT, a total of 166 separate ostia entering the left atrium were identified in the 43 patients. There were 92 right-sided and 78 left-sided PV ostia identified. The most common anatomic variant observed in this study was a common left PV antrum for the left superior PV (LSPV) and left inferior PV (LIPV), seen in 13 patients (30%). A separate right middle PV ostium was observed in seven patients (16%).
With preprocedural TEE, image quality was adequate for both anatomic and pulsed Doppler measurements in 100% of both right superior PV (RSPV) and right inferior PV (RIPV) and 98% of both LSPV and LIPV. The left PVs were not visualized in one patient, because of procedure intolerance and early termination of TEE. The separate right middle PV ostia were identified in six of the seven patients (86%) ( Figure 2 ); however, the 13 common left PV antra were correctly identified in only 54% by TEE.
PV Ostial Dimensions
On cardiac CT, PV ostia were generally elliptical in morphology, with the larger ostial diameters in the craniocaudal rather than in the transaxial axis in the LSPV, LIPV, and RSPV (all P values < .001). However, this was not observed in the RIPV ( P = .14). Comparing the preablation transesophageal echocardiographic measurement of anatomic ostia dimensions with that of CT, TEE significantly underestimated anatomic ostial measurements of the LIPV, RIPV, and LSPV by 0.34, 0.43, and 0.16 cm, respectively ( P < .001). However, there was no difference observed in the RSPV between the modalities ( Table 2 ).
| Variable | n (before/after PVI) | Before PVI | 3 months after PVI | P , before vs after PVI | Mean difference ∗ | |||
|---|---|---|---|---|---|---|---|---|
| Before vs after PVI | P | Before PVI (CT vs TEE) | P | |||||
| LSPV | ||||||||
| CT major axis (cm) | 43/37 | 1.65 ± 0.30 | 1.48 ± 0.30 | .001 | ||||
| CT minor axis (cm) | 1.42 ± 0.29 | 1.21 ± 0.24 | <.001 | |||||
| CT mean diameter (cm) | 1.54 ± 0.23 | 1.34 ± 0.23 | <.001 | 0.20 ± 0.22 | <.001 | |||
| CT area (cm 2 ) | 1.86 ± 0.56 | 1.43 ± 0.48 | <.001 | 0.42 ± 0.52 | <.001 | |||
| TEE diameter (cm) | 42/33 | 1.40 ± 0.24 | 1.21 ± 0.23 | <.001 | 0.17 ± 0.27 | .001 | 0.16 ± 0.30 | <.001 |
| LIPV | ||||||||
| CT major axis (cm) | 43/37 | 1.64 ± 0.33 | 1.47 ± 0.32 | .002 | ||||
| CT minor axis (cm) | 1.43 ± 0.34 | 1.18 ± 0.25 | <.001 | |||||
| CT mean diameter (cm) | 1.52 ± 0.29 | 1.32 ± 0.24 | <.001 | 0.21 ± 0.25 | <.001 | |||
| CT area (cm 2 ) | 1.84 ± 0.68 | 1.38 ± 0.47 | <.001 | 0.53 ± 0.61 | <.001 | |||
| TEE diameter (cm) | 42/33 | 1.18 ± 0.31 | 1.00 ± 0.25 | .007 | 0.16 ± 0.35 | .012 | 0.34 ± 0.34 | <.001 |
| RSPV | ||||||||
| CT major axis (cm) | 43/37 | 1.60 ± 0.29 | 1.50 ± 0.26 | .009 | ||||
| CT minor axis (cm) | 1.46 ± 0.31 | 1.32 ± 0.26 | .009 | |||||
| CT mean diameter (cm) | 1.53 ± 0.29 | 1.41 ± 0.23 | .005 | 0.12 ± 0.24 | .005 | |||
| CT area (cm 2 ) | 1.88 ± 0.79 | 1.58 ± 0.52 | .009 | 0.33 ± 0.67 | .009 | |||
| TEE diameter (cm) | 43/33 | 1.54 ± 0.43 | 1.27 ± 0.34 | .004 | 0.31 ± 0.41 | <.001 | 0.05 ± 0.35 | .284 |
| RIPV | ||||||||
| CT major axis (cm) | 43/37 | 1.68 ± 0.38 | 1.48 ± 0.34 | <.001 | ||||
| CT minor axis (cm) | 1.64 ± 0.38 | 1.42 ± 0.36 | <.001 | |||||
| CT mean diameter (cm) | 1.66 ± 0.36 | 1.41 ± 0.40 | <.001 | 0.26 ± 0.44 | <.001 | |||
| CT area (cm 2 ) | 2.25 ± 0.98 | 1.68 ± 0.82 | <.001 | 0.66 ± 1.00 | <.001 | |||
| TEE diameter (cm) | 42/33 | 1.24 ± 0.37 | 1.03 ± 0.38 | <.001 | 0.21 ± 0.32 | .001 | 0.43 ± 0.54 | <.001 |
∗ Paired comparisons to calculate the mean difference between paired measurements.
Postablation Changes of PVs
Three months after AF ablation, PV ostial dimensions significantly decreased for all four major PVs and were demonstrated by both modalities ( Table 2 ). The reductions in PV ostial dimensions detected by CT and TEE were 0.20 ± 0.03 cm ( P < .001) and 0.22 ± 0.03 cm ( P < .001), respectively. However, no patient developed symptoms consistent with PV stenosis at 3 months. On cardiac CT, moderate or severe stenosis was not seen in this cohort (>50% reduction in PV area compared with a proximal or distal reference). Mild PV stenosis (30% to 50% reduction) was seen in only two veins ( Table 3 ).
| Patient | Vein | Prior PVI | PV flow velocity on TEE (cm/sec) | TEE stenosis (turbulence at ostia, spectral broadening) | TEE-measured diameter (mm) | % area stenosis on CT | CT-measured diameter (mm) | |||
|---|---|---|---|---|---|---|---|---|---|---|
| Systolic | Diastolic | Before PVI | After PVI | Before PVI | After PVI | |||||
| 4 | LSPV | No | 104 | 126 | Yes | 16 | 8 | 40% | 13 × 10 | 12 × 4 |
| 4 | RSPV | 45 | 116 | No | 19 | 11 | <30% | 14 × 10 | 11 × 10 | |
| 21 | LIPV | Yes | 91 | 151 | Yes | 15 | 8 | 40% | 16 × 10 | 9 × 6 |
| 21 | RSPV | 39 | 121 | No | 14 | 12 | <30% | 13 × 10 | 10 × 9 | |
| 25 | LSPV | No | 73 | 102 | No | 10 | 10 | <30% | 14 × 12 | 10 × 10 |
| 29 | LSPV | Yes | 45 | 107 | No | 14 | 15 | <30% | 16 × 14 | 15 × 14 |
| 33 | RSPV | Yes | 21 | 102 | No | 24 | 13 | <30% | 24 × 23 | 17 × 15 |
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