Morphology of the Left Atrial Appendage: Introduction of a New Simplified Shape-Based Classification System.

Background The left atrial appendage (LAA) is a heart structure with known prothrombogenic and pro-arrhythmogenic properties. Aim The aim of this study was to evaluate the specific anatomy of the LAA and to create a simple classification system based on the shape of its body. Method and Results This study investigated 200 randomly selected autopsied human hearts (25.0% females, 46.6 +/- 19.1 years old). Three (3) types of LAAs were distinguished: the cauliflower type (no bend, limited overall length, compact structure [36.5%]); the chicken wing type (substantial bend in the dominant lobe [37.5%]), and the arrowhead type (no bend, one dominant lobe of substantial length [26.0%]). Additional accessory lobes were present in 55.5% of all LAAs. Significant variations between category types were noted in LAA length (chicken wing: 35.7 +/- 9.8 mm, arrowhead: 30.8 +/- 10.1 mm, cauliflower: 22.3 +/- 9.6 mm [p<0.001]) and in the thickness of pectinate muscles located within the LAA apex (arrowhead: 1.2 +/- 0.7 mm; cauliflower: 1.1 +/- 0.6 mm; chicken wing: 0.9 +/- 0.6 mm [p<0.001]). Left atrial appendage volume and orifice size were not affected by the type of LAA shape. The age of the donor was positively correlated with LAA volume (r=0.29, p=0.005), body length (r=0.26, p=0.012), and area of the orifice (r=0.36, p<0.001). Donors with an oval LAA orifice were significantly older than those with round orifices (50.2 +/- 16.6 vs 43.7 +/- 20.4 years [p=0.014]) and had significantly heavier hearts (458.2 +/- 104.8 vs 409.6 +/- 114.1g [p=0.002]). Conclusions This study delivered a new simple classification system of the LAA based on its body shape. An increase in age and heart weight was associated with LAA enlargement and a more oval-shaped orifice. Results of current study may help to estimate the different thrombogenic properties associated with each LAA type and be an assistance during planning and performing interventions on LAA.