This article appears in the following Europace issue: Spotlight Issue: Cardiac Imaging in EP and CRT [View the issue table of contents]
IMAGING IN CATHETER ABLATION FOR AF
Managing catheter ablation for atrial fibrillation: the role of echocardiography
Heart and Vascular Institute, Cleveland Clinic, 9500 Euclid Avenue, Desk F15, Cleveland, OH 44195, USA
* Corresponding author. Tel: +1 216 444 3932; fax: +1 216 445 2309. E-mail address: kleina{at}ccf.org
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Atrial fibrillation (AF) is a common arrhythmia associated with the serious clinical consequences of systemic thrombo-embolism and heart failure. Catheter ablation for AF is an evolving treatment option for patients with drug-refractory paroxysmal and persistent AF. The ablation procedure relies on precise knowledge of the left atrium, left atrial appendage, and pulmonary venous anatomy and function. Echocardiography is an integral component of multiple imaging modalities which contribute to its success. Both transoesophageal echocardiography and transthoracic echocardiography provide essential anatomical and functional information to guide all aspects of management. This article reviews the role of echocardigraphy in AF ablation, from appropriate patient selection and pre-procedural screening, to evaluating complications and determining the need for long-term anticoagulation.
Key Words: Transthoracic echocardiography, Transoesophageal echocardiography, Atrial fibrillation, Catheter ablation
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Radiofrequency catheter ablation of the left atrium (LA) and electrical isolation of the pulmonary veins (PV) is an important, potentially curative treatment option for selected patients with atrial fibrillation (AF). The procedure has evolved from direct focal ablation of AF triggers within the PV ostia to circumferential electrical isolation of LA tissue surrounding the PV. Multiple complementary imaging modalities with different strengths and weaknesses can be used to assist management decisions and to guide the ablation procedure in these patients. Echocardiography already has a well-recognized and essential role in current guidelines for the assessment of cardiac structure and function, and risk stratification of patients with AF.1
This article focuses on the role of transthoracic (TTE) and transoesophageal echocardiography (TEE) in catheter ablation of AF, from appropriate patient selection and pre-procedural screening, to evaluating complications and determining the need for long-term anticoagulation.
Initial evaluation and selection of patients for catheter ablation of atrial fibrillation: role of transthoracic echocardiography
Appropriate patient selection for catheter ablation of AF is important for optimizing the success and safety of the procedure. Initial evaluation with TTE is recommended for all patients to assess baseline LA and left ventricular (LV) size and function and to identify clinically silent valve, myocardial, pericardial, and congenital heart disease which may predispose to AF.1,2 In many cases, treatment of potentially underlying causes, such as pericarditis, myocarditis, or acute myocardial ischaemia, may revert AF and maintain sinus rhythm.
Patients with prolonged AF duration and marked LA dilatation are less likely to have a successful catheter ablation compared to patients with structurally normal hearts.3 This is reflected in current guideline recommendations supporting catheter ablation of AF as a reasonable alternative to pharmacologic therapy in symptomatic patients with little or no LA enlargement.1 TTE can readily determine LA size and function. LA diameter measurements from M-mode echocardiography have a tendency to underestimate true LA size; hence ideally LA volume assessment should use the area–length or Simpson's formula.4 An LA volume index of >41 mL/m2 can predict recurrence of AF after catheter ablation.5 Although well-correlated, echocardiographic measures of LA volume will underestimate size if directly compared with computed tomography (CT) or magnetic resonance imaging (MRI).6,7 Recently, the use of three-dimensional echocardiography to assess LA volume has been validated against MRI and has less test/retest as well as inter- and intra-observer variability compared with 2D echocardiography methods.8–10 Serial measures of LA volume using this method are also valid.
The presence of LV systolic and/or diastolic dysfunction can assist the choice of pharmacologic rate or rhythm control agents and the need for anticoagulation for long-term thrombo-embolic stroke reduction in patients with AF. Catheter ablation of selected symptomatic patients with AF and heart failure and/or reduced ejection fraction (EF) may be appropriate.11 Reliable and reproducible qualitative and quantitative volumetric measures of LV size and EF are easily obtained from TTE.12
Echocardiography in pre-procedural imaging: role of transoesophageal echocardiography
Exclusion of left atrium and left atrium appendage thrombus
The presence of thrombus in the LA or LA appendage is an absolute contraindication to catheter ablation of AF, reflecting the potential risk of systemic embolism from thrombus dislodged by catheter manipulation.2 Compared with TTE, multiplane TEE provides superior assessment of the LA and LA appendage in the majority of patients.13 TEE can detect LA and LA appendage thrombi with a high degree of sensitivity (92–100%), specificity (98–100%), and negative predictive value (98–100%) (Figure 1A).14–16 Despite its high accuracy, TEE can be insensitive to thrombi of <2 mm. Artifacts, pectinate muscles, ‘coumadin ridge’, and severe spontaneous echo contrast (SEC) may be sources of false-positive results for thrombus, particularly in multilobed LA appendages. Patients with identified thrombus should receive 4–6 weeks of oral anticoagulation followed by a further TEE to confirm thrombus resolution prior to the catheter ablation procedure. However, up to 20% of patients may have residual thrombus on follow-up TEE.17
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Unlike thrombus, SEC in the LA or LA appendage is not an absolute contraindication to AF ablation, and oral anticoagulation with warfarin does not appear to influence it.18
SEC is visualized as echogenic swirling blood flow, reflecting red cell and clotting factor aggregation in the setting of low blood velocity.18 The presence of SEC is associated with LA thrombus formation, a higher risk of thrombo-embolism, and increased cardiovascular mortality.19 Careful monitoring for LA thrombus during catheter ablation procedures is essential in the setting of SEC. Despite adequate anticoagulation with heparin, LA thrombus was seen on mapping catheters and sheaths in 10% of cases, and of these, SEC was visualized in 67% of cases.20 However, not all SEC is associated with the same risk. The presence of ‘sludge,’ a term referring to an intermediate stage of thrombosis characterized by precipitous, dense SEC seen throughout the cardiac cycle, is associated with a poorer outcome than mild, mobile intermittent SEC (Figure 1B).21
Although TEE has been a routine investigation for patients before catheter ablation, the number of cases cancelled due to the presence of LA or LA appendage thrombus is relatively small compared with electrical cardioversion. Temporal trends in TEE use between 1999 and 2006 at the Cleveland Clinic demonstrate that <2% of catheter ablation procedures were cancelled as a result of TEE findings.22 Additional stratification of patients according to EF or the CHADS2 score may identify patients at low risk who may not require pre-procedural TEE.23 Of 907 consecutive patients undergoing TEE prior to ablation, 394 (44%) had a CHADS2 score of zero. No patient with a CHADS2 score of zero had LA thrombus or sludge on TEE.24
Several recent papers have compared the accuracy of CT with TEE to identify thrombus in the LA appendage.25–27 While CT has demonstrated good negative predictive value for exclusion of LA appendage thrombus, concerns about the ability of CT to differentiate thrombus from SEC currently limit its use as a gold standard imaging modality.
Assessment of the left atrium and pulmonary vein anatomy and stenosis
Accurate definition of PV and LA anatomy is essential for planning catheter ablation procedures for AF. Variation in PV anatomy is common with 18–44% of patients demonstrating deviation from the most common pattern of two left and two right veins, with the right middle being a branch of the right superior vein.28 The presence of separate right middle vein ostia to the LA and common trunks of the left and right superior and inferior veins have been described (Figure 2). Unusual PV configurations can substantially influence the success rate of catheter ablation, particularly if variant veins are not adequately treated. The presence of a single ostium for the left PV predicted a lower maintenance of sinus rhythm at 12 months.29
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While CT and MRI remain the imaging modalities of choice, TEE can also identify differences in PV anatomy. In a study of 31 consecutive patients undergoing TEE and MDCT prior to catheter ablation, TEE performed by a single experienced operator identified superior and inferior PV in 100% of patients. The concordance of PV ostial location by TEE and CT was 82%.30
TEE was able to identify anomalies of a common left trunk and separate right middle vein ostia in 9 of 13 patients. A similar prospective study comparing PV anatomy by TEE with magnetic resonance angiography (MRA) in patients undergoing catheter ablation visualized the superior PV in 100% of cases and the right and left inferior veins in 98 and 94% of cases, respectively. Concordance with MRA was high at 95%.31 However, in another earlier study, visualization of either the left or the right inferior vein was not possible in one-third of patients, likely highlighting a greater dependence on TEE operator experience compared with image acquisition from CT or MRI.32 With the veins in view, careful rotation and turning of the probe can avoid foreshortening and underestimation of vein ostial dimensions. In our experience, all PV can be visualized in over 98% of the patients.
Echocardiography in assessment of complications of catheter ablation
Pulmonary vein stenosis
PV stenosis is a well-known complication of catheter ablation of AF, resulting from fibrosis and contraction of scar within the PV musculature after application of radiofrequency energy. The routine use of intracardiac echocardiography (ICE) to identify PV ostia and avoiding ablation within the PV itself has significantly reduced the incidence of this complication, with published rates ranging from 0 to 38%. Symptomatic patients typically present with dyspnea, cough, and recurrent lung infections; however, many patients are asymptomatic even in the setting of severe stenosis or occlusion. Therefore, many electrophysiologists will routinely screen for PV stenosis.
Identification of PV stenosis can be evaluated by a number of clinically accepted imaging modalities, including PV angiography, CT, MRI, and TEE prior to and several months after the ablation procedure. While CT or MRI are generally considered the gold standard imaging test for stenosis, the accumulated radiation and contrast exposure from serial CT scans is an important consideration for many patients and an MRI scan is contraindicated in others with pacemakers. TEE is an alternative study which can provide both anatomical and functional assessment of PV stenosis as either a first-line imaging test or can adjudicate in patients with equivocal symptoms and mild–moderate anatomic stenosis.
TEE can determine PV ostial diameters at the venoatrial junction. PV stenosis severity is defined according to the percentage reduction in luminal diameter: mild (<50%), moderate (50–70%), or severe (>70%) in recent consensus guidelines.2 The anatomic PV diameter should be timed with the maximum PV inflow velocity in diastole. Although correlated, TEE tends to underestimate ostial diameter compared with CT or ICE.32
An increasing number of patients undergoing repeat catheter ablation for AF may have small PV ostial diameters from pre-existing stenosis. Haemodynamically significant stenosis could potentially be missed in these patients if assessed only by the percent diameter loss before and after ablation. A diameter of <7 mm may be sufficient to call significant anatomic stenosis. However, functional assessment of stenosis using TEE can be helpful in this scenario.33
The functional significance of a stenosis can be confirmed with color and pulsed Doppler assessment of PV flow. Both turbulence and aliasing of the color Doppler and increased pulsed Doppler diastolic flow velocities are required to confirm the presence of haemodynamically significant stenosis (Figure 3). The exact cutoff velocity which optimally defines stenosis has been a matter of debate. Although many of the early case reports of PV stenosis quoted velocities in excess of 160 cm/s,34,35 velocities anywhere between 80 and 110 cm/s have been used. A recent analysis comparing CT with PV Doppler velocities by TEE, found optimum detection of stenosis at peak diastolic velocities >100 cm/s, with 86% sensitivity and 95% specificity.36 Additional diagnostic criteria assessing diminished variation in the peak PV systolic and diastolic velocities have been used by some groups.37
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Echocardiography in anticoagulation and thrombo-embolism prevention post-catheter abation
Damaged LA endothelium, potential recurrence of AF, and atrial stunning all contribute to an increased early risk of stroke after AF ablation procedures. There is general agreement that anticoagulation with warfarin for 2 months should be recommended for all patients after AF ablation. However, the decision to terminate long-term anticoagulation needs to be individualized according to patient risk of AF recurrence and thrombo-embolism. One retrospective study suggests long-term anticoagulation could be discontinued after AF ablation in patients with no or one clinical risk factors for stroke (excluding age >65 and a previous history of stroke).38
Several echocardiographic measures of atrial mechanical function and predictors of stroke can be used to guide anticoagulation (Table 1).
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Echocardiographic predictors of stroke
The presence of LA or LA appendage thrombus, dense SEC, or LA appendage emptying velocities <20 cm/s are markers for increased risk of thrombus formation.39
–41 These TEE parameters can provide prognostic information incremental to clinical factors for identification of high thrombo-embolic risk.41–43 LA appendage emptying velocities can be assessed with TEE using pulsed wave Doppler with the sample volume placed 1 cm within the LA appendage. Low LA appendage emptying velocity (<20 cm/s) is a marker of poor LA appendage mechanical function and correlates strongly with the presence of SEC and thrombus formation (Figure 1C).44 A TEE performed 3–6 months after AF ablation can evaluate thrombo-embolic risk and need for long-term anticoagulation, as echocardiographic risk factors may be present even if restoration of sinus rhythm is successful.
Atrial mechanical function
Measures of LA mechanical function including phasic LA volumes, transmitral peak early (E) and atrial (A) wave velocities, pulsed tissue Doppler imaging of the atrial (A’) wave and measures of atrial strain, and strain rate can be obtained from TTE in patients prior to and after ablation.45,46 A reduction in LA size can often be documented on follow-up TEE regardless of whether the AF ablation procedure was successful—this likely resulting from both atrial remodeling and scar formation. Several studies have investigated the impact of extensive AF ablation on atrial transport function, with conflicting results.47–49 One study demonstrated only a partial return of LA EF to normal after restoration of sinus rhythm in patients with chronic AF, and a decrease in LA EF in patients in sinus rhythm prior to their ablation procedure. Another study revealed an improvement in measures of contractile function after AF ablation. If evidence of LA failure (reduced LA EF, low transmitral A wave Doppler velocity, or PV atrial reversal velocities) is identified at follow-up TTE even in the presence of sinus rhythm, long-term anticoagulation should be considered in these patients (Figure 4). While it may not be realistic to obtain all these echocardiographic measures in routine practice, the role of atrial mechanical dysfunction as predictor of thrombo-embolic risk after AF ablation remains a topic of ongoing research.
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Echocardiography plays an integral and complementary role to CT, MRI, and ICE in the management of patients undergoing catheter ablation procedures for AF. The portability, non-invasiveness, absence of radiation exposure, and the few contraindications to both TTE and TEE ensure greater accessibility. The ability to provide both anatomical and functional information assists in the diagnosis of complications of AF ablation and management of long-term anticoagulation. Development of novel methods to assess PV and LA structure and function will ensure that the role of echocardiography will continue to evolve with AF ablation techniques.
Conflict of interest: none declared.
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Dr Ruvin Gabriel acknowledges the support of the National Heart Foundation of New Zealand Overseas Training and Research Fellowship Award. Dr Allan Klein acknowledges the support of the American Society of Echocardiography Outcomes Award.
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[1] Fuster V, Ryden LE, Cannom DS, Crijns HJ, Curtis AB, Ellenbogen KA, et al. ACC/AHA/ESC 2006 guidelines for the management of patients with atrial fibrillation: full text: a report of the American College of Cardiology/American Heart Association Task Force on practice guidelines and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Revise the 2001 guidelines for the management of patients with atrial fibrillation) developed in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society. Europace (2006) 8:651–745.
[2] Calkins H, Brugada J, Packer DL, Cappato R, Chen SA, Crijns HJ, et al. HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for personnel, policy, procedures and follow-up. A report of the Heart Rhythm Society (HRS) Task Force on Catheter and Surgical Ablation of Atrial Fibrillation developed in partnership with the European Heart Rhythm Association (EHRA) and the European Cardiac Arrhythmia Society (ECAS); in collaboration with the American College of Cardiology (ACC), American Heart Association (AHA), and the Society of Thoracic Surgeons (STS). Endorsed and approved by the governing bodies of the American College of Cardiology, the American Heart Association, the European Cardiac Arrhythmia Society, the European Heart Rhythm Association, the Society of Thoracic Surgeons, and the Heart Rhythm Society. Europace (2007) 9:335–79.
[3] Themistoclakis S, Schweikert RA, Saliba WI, Bonso A, Rossillo A, Bader G, et al. Clinical predictors and relationship between early and late atrial tachyarrhythmias after pulmonary vein antrum isolation. Heart Rhythm (2008) 5:679–85.[CrossRef][Web of Science][Medline]
[4] Lester SJ, Ryan EW, Schiller NB, Foster E. Best method in clinical practice and in research studies to determine left atrial size. Am J Cardiol (1999) 84:829–32.[CrossRef][Web of Science][Medline]
[5] Sleik K, Wazni O, Oneill J, Marrouche N, Klein A. Left atrial volume predicts recurrence of atrial fibrillation in patients undergoing pulmonary vein antrum isolation. Circulation (2004) 110:III–398.
[6] Kircher B, Abbott JA, Pau S, Gould RG, Himelman RB, Higgins CB, et al. Left atrial volume determination by biplane two-dimensional echocardiography: validation by cine computed tomography. Am Heart J (1991) 121:864–71.[CrossRef][Web of Science][Medline]
[7] Rodevan O, Bjornerheim R, Ljosland M, Maehle J, Smith HJ, Ihlen H. Left atrial volumes assessed by three- and two-dimensional echocardiography compared to MRI estimates. Int J Card Imaging (1999) 15:397–410.[CrossRef][Web of Science][Medline]
[8] Anwar AM, Soliman OI, Geleijnse ML, Nemes A, Vletter WB, ten Cate FJ. Assessment of left atrial volume and function by real-time three-dimensional echocardiography. Int J Cardiol (2008) 123:155–61.[CrossRef][Web of Science][Medline]
[9] Keller AM, Gopal AS, King DL. Left and right atrial volume by freehand three-dimensional echocardiography: in vivo validation using magnetic resonance imaging. Eur J Echocardiogr (2000) 1:55–65.
[10] Jenkins C, Bricknell K, Marwick TH. Use of real-time three-dimensional echocardiography to measure left atrial volume: comparison with other echocardiographic techniques. J Am Soc Echocardiogr (2005) 18:991–7.[CrossRef][Web of Science][Medline]
[11] Hsu LF, Jais P, Sanders P, Garrigue S, Hocini M, Sacher F, et al. Catheter ablation for atrial fibrillation in congestive heart failure. N Engl J Med (2004) 351:2373–83.
[12] Lang RM, Bierig M, Devereux RB, Flachskampf FA, Foster E, Pellikka PA, et al. Recommendations for chamber quantification: a report from the American Society of Echocardiography's Guidelines and Standards Committee and the Chamber Quantification Writing Group, developed in conjunction with the European Association of Echocardiography, a branch of the European Society of Cardiology. J Am Soc Echocardiogr (2005) 18:1440–63.[CrossRef][Web of Science][Medline]
[13] Omran H, Jung W, Rabahieh R, Wirtz P, Becher H, Illien S, et al. Imaging of thrombi and assessment of left atrial appendage function: a prospective study comparing transthoracic and transoesophageal echocardiography. Heart (1999) 81:192–8.
[14] Aschenberg W, Schluter M, Kremer P, Schroder E, Siglow V, Bleifeld W. Transesophageal two-dimensional echocardiography for the detection of left atrial appendage thrombus. J Am Coll Cardiol (1986) 7:163–6.[Abstract]
[15] Fatkin D, Scalia G, Jacobs N, Burstow D, Leung D, Walsh W, et al. Accuracy of biplane transesophageal echocardiography in detecting left atrial thrombus. Am J Cardiol (1996) 77:321–3.[CrossRef][Web of Science][Medline]
[16] Manning WJ, Weintraub RM, Waksmonski CA, Haering JM, Rooney PS, Maslow AD, et al. Accuracy of transesophageal echocardiography for identifying left atrial thrombi. A prospective, intraoperative study. Ann Intern Med (1995) 123:817–22.
[17] Jaber WA, Prior DL, Thamilarasan M, Grimm RA, Thomas JD, Klein AL, et al. Efficacy of anticoagulation in resolving left atrial and left atrial appendage thrombi: a transesophageal echocardiographic study. Am Heart J (2000) 140:150–6.[CrossRef][Web of Science][Medline]
[18] Black IW, Hopkins AP, Lee LC, Walsh WF. Left atrial spontaneous echo contrast: a clinical and echocardiographic analysis. J Am Coll Cardiol (1991) 18:398–404.[Abstract]
[19] Bernhardt P, Schmidt H, Hammerstingl C, Luderitz B, Omran H. Patients with atrial fibrillation and dense spontaneous echo contrast at high risk a prospective and serial follow-up over 12 months with transesophageal echocardiography and cerebral magnetic resonance imaging. J Am Coll Cardiol (2005) 45:1807–12.
[20] Ren JF, Marchlinski FE, Callans DJ. Left atrial thrombus associated with ablation for atrial fibrillation: identification with intracardiac echocardiography. J Am Coll Cardiol (2004) 43:1861–7.
[21] Lowe B, Varr B, Shrestha K, Whitman C, Klein A. Prognostic significance of left atrial appendage ‘sludge’ in patients with atrial fibrillation: a new transesophageal echocardiographic thromboembolic risk factor. Circulation (2007) 116:II-687.
[22] Varr B, Gabriel R, Jaffer S, Curtin R, Daly R, Wazni O, et al. Is transesophageal echocardiography necessary for screening of patients with atrial fibrillation prior to pulmonary vein antral isolation? J Am Coll Cardiol (2008) 51:A118.
[23] Khan MN, Usmani A, Noor S, Elayi S, Ching CK, Biase LD, et al. Low incidence of left atrial or left atrial appendage thrombus in patients with paroxysmal atrial fibrillation and normal EF who present for pulmonary vein antrum isolation procedure. J Cardiovasc Electrophysiol (2008) 19:356–8.[CrossRef][Web of Science][Medline]
[24] Puwanant S, Varr B, Gabriel R, Lowe B, Shrestha K, Saliba W, et al. Role of CHADS2 score in evaluation of thromboembolic risk in patients with atrial fibrillation undergoing transesophageal echocardiography prior to pulmonary vein isolation. J Am Soc Echocardiogr (2008) 21:583.
[25] Kim YY, Klein AL, Halliburton SS, Popovic ZB, Kuzmiak SA, Sola S, et al. Left atrial appendage filling defects identified by multidetector computed tomography in patients undergoing radiofrequency pulmonary vein antral isolation: a comparison with transesophageal echocardiography. Am Heart J (2007) 154:1199–205.[CrossRef][Web of Science][Medline]
[26] Patel A, Au E, Donegan K, Kim RJ, Lin FY, Stein KM, et al. Multidetector row computed tomography for identification of left atrial appendage filling defects in patients undergoing pulmonary vein isolation for treatment of atrial fibrillation: comparison with transesophageal echocardiography. Heart Rhythm (2008) 5:253–60.[CrossRef][Web of Science][Medline]
[27] Shapiro MD, Neilan TG, Jassal DS, Samy B, Nasir K, Hoffmann U, et al. Multidetector computed tomography for the detection of left atrial appendage thrombus: a comparative study with transesophageal echocardiography. J Comput Assist Tomogr (2007) 31:905–9.[Web of Science][Medline]
[28] Marom EM, Herndon JE, Kim YH, McAdams HP. Variations in pulmonary venous drainage to the left atrium: implications for radiofrequency ablation. Radiology (2004) 230:824–9.
[29] Jacob R, Patel D, Lieber M, Williams M, Natale A, Sola S. Pulmonary venous anatomy predicts recurrent arrhythmia after pulmonary vein antrum isolation for atrial fibrillation. Circulation (2007) 116:II_562.
[30] Lowe B, Curtin R, Park M, Ong H, Whitman C, Jasper S, et al. Transesophageal echocardiographic determination of pulmonary venous anatomic variations: comparison with computed tomography. J Am Soc Echocardiogr (2007) 20:623.
[31] Toffanin G, Scarabeo V, Verlato R, De Conti F, Zampiero AA, Piovesana P. Transoesophageal echocardiographic evaluation of pulmonary vein anatomy in patients undergoing ostial radiofrequency catheter ablation for atrial fibrillation: a comparison with magnetic resonance angiography. J Cardiovasc Med (Hagerstown) (2006) 7:748–52.[Medline]
[32] Wood MA, Wittkamp M, Henry D, Martin R, Nixon JV, Shepard RK, et al. A comparison of pulmonary vein ostial anatomy by computerized tomography, echocardiography, and venography in patients with atrial fibrillation having radiofrequency catheter ablation. Am J Cardiol (2004) 93:49–53.[Web of Science][Medline]
[33] Kluge A, Dill T, Ekinci O, Hansel J, Hamm C, Pitschner HF, et al. Decreased pulmonary perfusion in pulmonary vein stenosis after radiofrequency ablation: assessment with dynamic magnetic resonance perfusion imaging. Chest (2004) 126:428–37.[CrossRef][Web of Science][Medline]
[34] Seshadri N, Novaro GM, Prieto L, White RD, Natale A, Grimm RA, et al. Images in cardiovascular medicine. Pulmonary vein stenosis after catheter ablation of atrial arrhythmias. Circulation (2002) 105:2571–2.
[35] Sohn RH, Schiller NB. Left upper pulmonary vein stenosis 2 months after radiofrequency catheter ablation of atrial fibrillation. Circulation (2000) 101:E154–E155.[Medline]
[36] Sigurdsson G, Troughton RW, Xu XF, Salazar HP, Wazni OM, Grimm RA, et al. Detection of pulmonary vein stenosis by transesophageal echocardiography: comparison with multidetector computed tomography. Am Heart J (2007) 153:800–6.[CrossRef][Web of Science][Medline]
[37] Jander N, Minners J, Arentz T, Gornandt L, Furmaier R, Kalusche D, et al. Transesophageal echocardiography in comparison with magnetic resonance imaging in the diagnosis of pulmonary vein stenosis after radiofrequency ablation therapy. J Am Soc Echocardiogr (2005) 18:654–9.[CrossRef][Web of Science][Medline]
[38] Oral H, Chugh A, Ozaydin M, Good E, Fortino J, Sankaran S, et al. Risk of thromboembolic events after percutaneous left atrial radiofrequency ablation of atrial fibrillation. Circulation (2006) 114:759–65.
[39] Echocardiographic predictors of stroke in patients with atrial fibrillation: a prospective study of 1066 patients from 3 clinical trials. Arch Intern Med (1998) 158:1316–20.
[40] The Stroke Prevention in Atrial Fibrillation Investigators Committee on Echocardiography. Transesophageal echocardiographic correlates of thromboembolism in high-risk patients with nonvalvular atrial fibrillation. Ann Intern Med (1998) 128:639–47.
[41] Zabalgoitia M, Halperin JL, Pearce LA, Blackshear JL, Asinger RW, Hart RG. Transesophageal echocardiographic correlates of clinical risk of thromboembolism in nonvalvular atrial fibrillation. Stroke Prevention in Atrial Fibrillation III Investigators. J Am Coll Cardiol (1998) 31:1622–6.
[42] Dawn B, Varma J, Singh P, Longaker RA, Stoddard MF. Cardiovascular death in patients with atrial fibrillation is better predicted by left atrial thrombus and spontaneous echocardiographic contrast as compared with clinical parameters. J Am Soc Echocardiogr (2005) 18:199–205.[CrossRef][Web of Science][Medline]
[43] Thambidorai SK, Murray RD, Parakh K, Shah TK, Black IW, Jasper SE, et al. Utility of transesophageal echocardiography in identification of thrombogenic milieu in patients with atrial fibrillation (an ACUTE ancillary study). Am J Cardiol (2005) 96:935–41.[CrossRef][Web of Science][Medline]
[44] Goldman ME, Pearce LA, Hart RG, Zabalgoitia M, Asinger RW, Safford R, et al. Pathophysiologic correlates of thromboembolism in nonvalvular atrial fibrillation: I. Reduced flow velocity in the left atrial appendage [The Stroke Prevention in Atrial Fibrillation (SPAF-III) study]. J Am Soc Echocardiogr (1999) 12:1080–7.[CrossRef][Web of Science][Medline]
[45] Hesse B, Schuele SU, Thamilasaran M, Thomas J, Rodriguez L. A rapid method to quantify left atrial contractile function: Doppler tissue imaging of the mitral annulus during atrial systole. Eur J Echocardiogr (2004) 5:86–92.
[46] Thomas L. Assessment of atrial function. Heart Lung Circ (2007) 16:234–42.[CrossRef][Medline]
[47] Verma A, Kilicaslan F, Adams JR, Hao S, Beheiry S, Minor S, et al. Extensive ablation during pulmonary vein antrum isolation has no adverse impact on left atrial function: an echocardiography and cine computed tomography analysis. J Cardiovasc Electrophysiol (2006) 17:741–6.[CrossRef][Web of Science][Medline]
[48] Lemola K, Desjardins B, Sneider M, Case I, Chugh A, Good E, et al. Effect of left atrial circumferential ablation for atrial fibrillation on left atrial transport function. Heart Rhythm (2005) 2:923–8.[CrossRef][Web of Science][Medline]
[49] Donal E, Grimm RA, Yamada H, Kim YJ, Marrouche N, Natale A, et al. Usefulness of Doppler assessment of pulmonary vein and left atrial appendage flow following pulmonary vein isolation of chronic atrial fibrillation in predicting recovery of left atrial function. Am J Cardiol (2005) 95:941–7.[CrossRef][Web of Science][Medline]
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