Left Atrial Appendage Orifice Size in Japanese Patients with Atrial Fibrillation

Implanting a WATCHMAN device for atrial fibrillation (AF) requires thorough knowledge of left atrial appendage (LAA) anatomy; however, “racial differences are observed in LAA size when comparing Asians with non-Asians,” wrote the authors of a study published in the Journal of Echocardiology. The study’s authors, led by Miho Miyoshi, reported data on LAA orifice dimensions, as measured by multiplane transesophageal echocardiography, in a population of Japanese patients with AF.

The authors’ report proposed that “this finding should be used as a reference to understand the racial characteristics of LAA size for the WATCHMAN procedure.”

The study included a total of 170 patients with paroxysmal or persistent AF who underwent transesophageal echocardiography assessment before a catheter ablation or cardioversion procedure between September 2018 and September 2019. According to the authors, “the maximal LAA ostial diameters were measured at multiplane angles of 0°, 45°, 90°, and 135°,” per the WATCHMAN device recommendations.

Miyoshi and colleagues reported that 71% of patients (121/160) had an LAA orifice size between 17 and 25 mm. Among patients outside of this range, 15 (8.8%) patients had LAA orifice size below 17 mm, termed undersized, and eight “oversized” patients (0.5%) had LAA size over 31 mm. One patient was observed with no LAA.

Notably, “LAA size was significantly larger in patients with persistent AF than in those with paroxysmal AF (23.3 ± 4.2 mm vs. 20.0 ± 3.0 mm; p <0.001) and in male patients than in female patients (22.4 ± 4.2 vs. 20.9 ± 3.7 mm; p = 0.03).” The investigators also reported that LAA dimensions were significantly correlated with CHADS2 score, left atrial value (LAV), E/e’ ratio, and left ventricular ejection fraction, while persistent AF, body mass index, and LAV were associated with LAA orifice dimension.

“This finding should be used as a reference to understand the racial characteristics of LAA size for the WATCHMAN procedure,” the authors concluded.