Atrial Fibrillation and the Role of LAA in Pathophysiology and Clinical Outcomes?

Abstract

Left atrial appendage (LAA) is a source of thromboembolism especially in patients with non valvular atrial fibrillation (AF). It is reasonable to accept LAA as a distinct part of left atrium (LA) with unique anatomical and physiological properties. Advances in imaging modalities increased the knowledge about anatomical and physiological characteristics of LAA. It is important to prevent the AF patients from systemic thromboembolic events, and new pharmacological and non pharmacological management approaches demonstrate encouraging results. Also pulmonary vein isolation which has been accepted as a curative and useful treatment option for the treatment of drug resistant AF has been helpful in understanding the electrophysiological properties of LAA. Accumulating data revealed that LAA continues to be the one of the most important structure of heart during AF because of its distinctive anatomical, mechanical, and electrophysiological properties.

Figure 1.. Longitudinal two chamber view of left atrium and left ventricle by 2-D transesophageal echocardiography demonstrating the left atrial appendage in a patient without cardiac disease.

Figure 2.. Outflow and inflow signals recorded during Doppler imaging of left atrial appendage in a patient without cardiac disease. In addition to high amplitude outflow and inflow signals two additional low amplitude inflow and outflow signals are present which can demonstrate the quadriphasic pattern. The velocities of high amplitude outflow and inflow signals are greater than 50cm/s.

Figure 3.. Doppler imaging of left atrial appendage in a patient with non valvular atrial fibrillation. Record demonstrates the irregular outflow and inflow signals in varying size and shape. The mean maximal value of outflow and inflow Doppler velocities is lower than 25 cm/s.

Figure 4.. a) The PLAATO system (ev3, Inc, Plymouth, Minnesota) b) Amplatzer cardiac plug (AGA Medical Corpo-Corporation, Plymouth, Minnesota, USA) c) The WATCHMAN (Atritech Inc., Plymouth, Minnesota, USA) device d) LARIAT Suture Delivery Device (SentreHEART Inc, Palo Alto, CA)