Intracardiac echocardiographic imaging of the left atrial appendage

Real-time intracardiac echocardiographic (ICE) imaging is increasingly being used to guide catheter ablation procedures for atrial fibrillation. Using an ICE catheter placed within the right atrium enables visualization of most of the left atrial anatomy. However, visualization of the cavity of the left atrial appendage (LAA) can difficult and, even when possible, typically reveals only the ostium of the LAA. In patients undergoing catheter ablation of atrial fibrillation, nonconventional imaging planes were used to visualize the LAA by ICE imaging. Using a 10Fr phased-array ultrasound catheter (AcuNav, Acuson Inc., Mountain View, CA, USA), a long-axis view of the LAA can be obtained by placing the catheter within the coronary sinus. As shown in Figure A, the image quality of left atrial structures is high because of the minimal amount of tissue between the coronary sinus and left atrium (not seen on the image). Alternatively, a short-axis view of the LAA can be obtained by placing the ultrasound catheter in the right ventricular outflow tract just proximal to the pulmonary valve. The pulmonary valve and proximal portion of the main pulmonary artery are shown in Figure B. Using a combination of these two imaging planes, the LAA can be assessed prior to entering the left atrium. After a transseptal puncture is performed using a standard 8Fr sheath, the ICE catheter can be manipulated across the transseptal puncture hole directly into the left atrium. After withdrawing the sheath back into the right atrium, the remaining transseptal puncture hole typically is large enough to allow advancement of the ICE catheter through the hole. With the catheter positioned in the body of the left atrium, the ICE catheter can be used to visualize the LAA in a long-axis plane that is orthogonal to the view provided from within the coronary sinus (Figure C; in this image, the ICE catheter is located just within the ostium of the left superior pulmonary vein), albeit with the requirement for a transseptal puncture.