Austin, Texas. Left atrial appendage (LAA) is thought to be the source of 90-98% of atrial thrombi occurring in atrial fibrillation (AF). Whether the morphology of LAA predicts the occurrence of stroke is not known. A multicenter study reports, for the first time, that LAA morphology can be broadly classified into 4 different categories and some of them is associated with a higher risk of stroke than others.

LAA is a long tubular structure with different lobes located in the anterior region of atrioventricular sulcus close to left circumflex artery, the left phrenic nerve and the left pulmonary veins. Based on morphology, the authors classified the LAA into four types (i) Cactus LAA (ii) Chicken wing LAA (iii) Windsock LAA and (iv) Cauliflower LAA. The authors identified 932 drug resistant AF patients in whom pre-ablation cardiac CT or MRI was performed. The CHADS2 score before the occurrence of thromboembolic event and history of any stroke/TIA was obtained from the patient’s charts. The morphology of LAA including the LAA volume, LAA velocity and diameters were assessed by two radiologists blinded to patient’s history and clinical information.

The prevalence of different LAA types in overall population were as follows: Cactus 278(30%), Chicken wing 451(48%), Windsock 179 (19%) and Cauliflower 24(3%). The inter-observer variability in classifying LAA into these groups was very low. When compared to non-chicken wing type LAA, the Chicken wing type was associated with the lowest number of patients with CHADS2 score ? 2(9% vs. 18%, p<0.001). Of the 78 (8%) patients who had prior stroke /TIA, the prevalence of stroke was the lowest in the chicken type LAA (4% vs. 12% non-chicken wing type LAA, p<0.001) and was more likely associated with Cactus type LAA (OR 2.5; p =0.045). In the patient cohort with CHADS2 score ? 1, non chicken was independent predictor of stroke (OR 10.1; p=0.019), whereas in patients with CHADS2 score ? 2, the difference between chicken wing and other types was not statistically significant (46% vs. 29%, p = 0.061). But the patients with CHADS2 score ? 2 constituted only 14% of overall population indicating probably the study was underpowered to detect any statistical difference in the latter group.

In summary, this study demonstrates that LAA morphology is major independent predictor of embolic phenomenon particularly in low-intermediate risk of stroke/TIA i.e., patients with CHADS2 score of 0 to 1. Given the current lack of consensus regarding anticoagulation in patients with low-risk CHA2DS2-VaSc score, the findings of the current study suggest LAA morphology might guide in making decisions about anti-coagulation. Reference: 1. Di Biase L, Santangeli P, Anselmino M, Mohanty P, Salvetti I, Gili S, Horton R, Sanchez JE, Bai R, Mohanty S, Pump A, Cereceda Brantes M, Gallinghouse GJ, Burkhardt JD, Cesarani F, Scaglione M, Natale A, Gaita F.Does the left atrial appendage morphology correlate with the risk of stroke in patients with atrial fibrillation?: results from a multicenter study. J Am Coll Cardiol. 2012 Aug 7;60(6):531-8