Clinical Implications of Left Atrial Appendage Flow Patterns in Nonrheumatic Atrial Fibrillation: Echocardiographic Studies

All the patients received transthoracic echocardiography and TEE. The transthoracic echocardiography was performed with a 2.5- or 3.75-MHz phased-array transducer connected to an ultrasound system (Aloka SSD-870 Aloka Co, Ltd, Tokyo, Japan). All the transthoracic echocardiography measurements were obtained according to the standards of American Society of Echocardiography. Left ventricular ejection fraction was calculated by the method of Teichholz et al.n Transesophageal echocardiography was performed according to previously described methods with a 5-MHz phased-arrav biplane transesophageal transducer connected to the same ultrasound system. After topical pharyngeal anesthesia with lidocaine spray, the patient was placed in the left lateral position, and the gastroscope was advanced into the esophagus. The LAA was observed from the basal short axis view in transverse scan.

Three parameters were observed and measured subsequently. First, the LAA area was measured by tracing a line from the top of the limbus of the left upper pulmonary vein to the aorta at its shortest distance and along the whole LAA endocardial border (Fig 1). The LAA maximal and minimal areas were determined bv two observers independent of the electrocardiography, and were measured blind to each other. The LAA ejection fraction was calculated as (LAA maximal area – LAA minimal area)/LAA maximal area. Second, the LAA blood flow pattern was obtained bv putting the pulsed Doppler sample volume into the LAA cavitv and the Doppler signals were recorded in five to ten consecutive cardiac cycles. The peak emptying velocity was measured. Third, the presence of SEC and thrombus in left atrium or LAA was observed by two independent observers. The SEC was defined as dynamic smoke-like echoes swirling slowly in the left atrium or LAA cavity despite adjustment in gain setting. Left atrium or LAA thrombus was diagnosed by demonstrating well-defined echogenic mass with different echotexture from that of the left atrial or LAA wall. Any difference in determination was resolved bv a third observer’s opinion. buy allegra

Interobserver variability in the measurement of the LAA maximal and minimal area between the two observers was assessed in ten randomly selected subjects. The mean interobserver difference in the LAA maximal area was 0.78 cm2 (range, 0.1 to 1.8 cm2) and in the LAA minimal area was 0.81 cm2 (range. 0.2 to 1.6 cm2). Correlation of the measurements of the LAA maximal and minimal area between the two observers was good (r = 0.986 and 0.991, respectively).
All values are expressed as mean ± SD. The continuous variables between groups were compared by Student unpaired t test. The %2 test or Fisher s exact test was used to compare categoric variables. A p value < 0.05 was considered statistically significant.

Figure-1

Figure 1. Transesophageal echocardiography from a patient with nonrheumatic atrial fibrillation showing the measurement of the left atrial appendage (LAA) area. AO = aorta; LI = limbus of left upper pulmonary vein.

This entry was posted in Nonrheumatic Atrial Fibrillation and tagged echocardiography, ejection fraction, thromboembolism, thrombus.