ANATOMY OF THE NORMAL LEFT ATRIAL APPENDAGE - A QUANTITATIVE STUDY OFAGE-RELATED-CHANGES IN 500 AUTOPSY HEARTS - IMPLICATIONS FOR ECHOCARDIOGRAPHIC EXAMINATION

Background Transesophageal echocardiography (TEE) is the diagnostic mo dality of choice for visualizing the left atrial appendage (LAA). This study defined the morphology of the LAA in normal autopsy specimen he arts and considered the implications of these findings for TEE studies . Methods and Results Five hundred normal autopsy hearts were reviewed (25 male and 25 female subjects from each decade for 10 decades). LAA length, width, orifice size, and number of lobes were recorded. Numbe r of lobes was cam pared between sexes with the rank sum test and regr essed against age. Mean length, width, and orifice size increased with age, up to age 20 years, in both sexes. Rates were significantly diff erent between sexes for LAA size (P=.011) and width (P=.006). After ag e 20, statistically significant but clinically insignificant age-relat ed changes were observed. Fifty-four percent of LAAs had two lobes (ra nge, 1 to 4), with no age or sex differences. Lobes exist in different planes of the heart. Most pectinate muscles were greater than or equa l to 1 mm in width. Pectinate muscles <1 mm (2.6% of cases) were seen in only the first and last decades. Conclusions Age- and sex-related d ifferences in LAA dimensions exist. These differences and the existenc e of multilobed appendages are important in the accurate TEE evaluatio n of LAA. Because lobes exist in different planes, imaging must be don e in multiple planes to visualize the entire LAA.