Imaging for Atrial Fibrillation

Flow diagram illustrating the role of cardiac imaging in the evaluation and treatment of AF. Adapted with permission from Camm et al. Figure 3 from Guidelines for the management of atrial fibrillation: The Task Force for the Management of Atrial Fibrillation of the European Society of Cardiology (ESC) Eur Heart J (2010) 31(19): 2369-2429.¹ LA, left atrial; LASEC, left atrial spontaneous echocardiographic contrast. (Color version of figure is available online.)

left atrial (LA) anatomy correlates with noninvasive imaging. (A) Longitudinal section through the heart that permits visualization of the interatrial septum from the LA. The black arrow indicates the crescentic edge of the fossa ovalis. On 3-dimensional TEE (B), these anatomical details can be noted together with the surrounding structures, such as the RSPV, the mitral valve, and the CS. The anterior wall of the LA is displayed in (C). The aortic root is retracted forward and the right and left atrial appendages (LAAs) are deflected laterally. The BB is located at the interatrial groove and the curved arrows indicate the bifurcations of this bundle as it approaches the appendages. The dotted line indicates the “unprotected” LA wall. The imaging correlate of these structures can be appreciated with MDCT (D). The aortic root is colored red. The LA is located posteriorly. MDCT provides superior image quality and permits identification of the pulmonary veins, LAA, right atrial appendage, and the SVC. (Adapted with permission.⁸⁴). Ao, aorta; BB, Bachmann's bundle; CS, coronary sinus; LAA, left atrial appendage; LIPV, left interior pulmonary vein; LSVP/LS, left superior pulmonary vein; RAA, right atrial appendage; RIPV, right inferior pulmonary vein; RSPV/RS, right superior pulmonary vein; SVC, superior vena cava. (Color version of figure is available online.)

Visualization of the left atrial appendage (LAA) with noninvasive imaging techniques. (A) Anatomical section through the ostium (OS) of the LAA (double arrowhead). The spatial relationship of the LAA with the circumflex coronary artery (Cx), left pulmonary veins (superior [LSPV] and inferior [LIPV]), and mitral valve can be visualized. On 2-dimensional TEE (B), a 45°-60° midesophageal view permits visualization of the long axis of the LAA and the relationship with the circumflex coronary artery, the left superior pulmonary vein, and the ridge that separates them. The pectinate muscles are located within the body of the LAA (arrows). With 3-dimensional TEE, the exact relationship between the LAA and the left superior pulmonary vein can be visualized. (D) Longitudinal section of the heart through the ridge (black arrow) and the pointed profile of this structure formed by the infolding of the atrial wall. MDCT reconstructions provide accurate evaluation of these structures. (E) Longitudinal section of the heart visualized with MDCT. The left superior pulmonary vein is separated by the ridge from the LAA. The circumflex coronary artery is in close relationship with the left appendage and the mitral annulus. (Adapted with permission.) CS, coronary sinus; Cx, circumflex coronary artery; LAA, left atrial appendage; LIPV/LI, left interior pulmonary vein; LSVP/LS, left superior pulmonary vein; OS, ostium. (Color version of figure is available online.)

Assessment of left atrial dimensions. Two-dimensional techniques for estimating LA linear diameters and volume,⁸⁶ where L is the longer of L₁ and L₂, and A_2CH and A_4CH are the areas of the atrium traced at end-ventricular systole in the apical 2- and 4-chamber views, respectively, and h is the disk height. A, parasternal long axis view; B, apical 4-chamber view; C, apical 2-chamber view. (Color version of figure is available online.)

Three-dimensional techniques for the evaluation of left atrial size and geometry. (A) Representative short-axis cine cardiac magnetic resonance image at the level of the left atrium at end-ventricular systole. LA volume may be estimated by summation of the volumes of contiguous slices spanning the left atrium. (B-E) Cropped 3-dimensional transthoracic echocardiography data set. The left atrium is demonstrated in the 4-chamber (B), 2-chamber (C), short-axis (D) views, and as a sliced 3-dimensional image (E). A volume-rendered computed tomography image of the left atrium and pulmonary veins is displayed in (F), with orthogonal sections through the left atrium in the 4-chamber (G), 2-chamber (H), and short axis (I) views. Ao, aorta; LA, left atrium; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein; LV, left ventricle; PA, pulmonary artery; RA, right atrium; RIPV, right inferior pulmonary vein; RSPV, right superior pulmonary vein. (Color version of figure is available online.)

Graphical representation of phasic changes in LA volume during the cardiac cycle.

Transthoracic echocardiographic techniques for evaluating LA function. (A) Tissue Doppler imaging of the septal mitral annulus, with A′ indicated (blue arrows). (B) Speckle-tracking strain of the left atrium, with dotted curve representing the average of 6 segments and the yellow arrow indicating the peak strain. (C) Strain rate of the left atrium by tissue Doppler imaging (white arrows). (Color version of figure is available online.)

Delayed enhancement cardiac magnetic resonance of the left atrium to quantify myocardial fibrosis. After CMR cropping, LA epicardium and endocardium are manually planimetered to create a region of interest. Areas of delayed enhancement are highlighted by an algorithm on the basis of pixel intensity. (Reproduced with permission.³⁶) Ao, aorta; LA, left atrium. (Color version of figure is available online.)

Real-time integration of intracardiac echocardiography and MDCT to guide RFCA. The LA endocardial contours are traced in real-time (A) to obtain a 3-dimensional reconstruction of the left atrium (B). In addition, the pulmonary veins are localized (C) and incorporated in the volume rendering of the left atrium (D). Manual coregistration of the 3-dimensional LA volume obtained with intracardiac echocardiography and MDCT is performed to obtain the final 3-dimensional rendering of the left atrium to guide the procedure (E). (Adapted with permission.⁷²) Add PV, additional pulmonary vein; LCO, left common ostium; RIVP, right inferior pulmonary vein; RSPV, right superior pulmonary vein. (Color version of figure is available online.)

Difference in visibility of (A) active (capable of receiving magnetic resonance signal) and (B) passive catheters on magnetic resonance images in a canine model.