Variations in the Size and Shape of Left Atrial Appendage: A Cross-sectional Study-based on Autopsy Specimens and their Endocasts

Introduction: Atrial appendages are recognised as structures with implications in cardiac thromboembolism and arrhythmogenesis. Variations in the shape and size of atrial appendages, especially the Left Atrial Appendage (LAA), have been found to impact these pathological conditions. Knowledge about the variations in the relationship of the LAA to its nearby structures is important in planning interventional and surgical procedures in and around the LAA. Most of the studies on variations in LAA morphology are image-based, with only a few anatomical studies available. Aim: To investigate the variations in the shape and size of the LAA using autopsy specimens. Materials and Methods: This cross-sectional study examined LAA specimens from 50 autopsies conducted in a tertiary care teaching hospital. Observations were made on the shape of LAA, the shape of LAA orifice, and its relationship with the Pulmonary Vein (PV) orifice. Measurements were taken of the LAA's length, external diameter, and LAA orifice's diameter. Endocasts were prepared from 30 specimens to estimate internal volume. The shape classification system proposed by Wang Y et al., was used. Categorical variables were expressed as percentages, and continuous variables as mean and standard deviation. Results: The windsock type was the most common seen in 29 (58%), followed by the chicken wing type in 15 (30%). The majority 30 (60%) of LAA orifices were oval. In 27 cases (54%), the Left Superior Pulmonary Vein (LSPV) orifice was at a higher level than LAA orifice and in 20 (40%), both orifices were at same level, with a prominent ridge between the orifices in all patients. The majority of appendages were bilobed 22 (44%). There was considerable variation in the length, diameter, and internal volume of the LAA appendage. Specimens from females were found to have smaller external diameters. One patient with an accessory LAA was identified. Conclusion: The shape variations observed in this study were similar to findings in some earlier studies but in contrast to others. Variations in the shape and size of the LAA orifice and the size of the LAA were consistent with those reported in earlier studies. Larger studies exploring these anatomical variations in specimens will be valuable for designing and developing therapeutic interventions in and around the LAA.