The anatomical characteristics of three different endocardial lines in the left atrium: evaluation by computed tomography prior to mitral isthmus block attempt.

AIMS: Additional linear ablation lesions are created to improve the outcomes of pulmonary vein (PV) isolation during atrial fibrillation (AF) ablation. We aimed to evaluate the safety and feasibility of additional ablation sites in terms of anatomical characteristics. METHODS AND
RESULTS: Multi-detector computed tomography (MDCT) data from 140 consecutive patients (40 with AF, 84 males, 59 ± 11 years old) and additional 10 heart specimens were analysed for their anatomical characteristics at three types of mitral isthmus lines: anteromedial (AM), anterolateral (AL), and posterolateral (PL) lines (from right superior, left superior, and left inferior PV to 10, 12, and 4 o'clock position of the mitral annulus, respectively). The data demonstrated that the length was shortest at the PL lines (MDCT, 36.4 ± 8.6 mm; specimens, 31 ± 6 mm) and the maximal myocardial thickness was greatest at the AL lines (MDCT, 3.2 ± 1.0 mm; specimens, 5.0 ± 0.9 mm). Ridge, cord-like structure, or diverticulum was found most frequently at the AM lines (MDCT, 20%; specimens, 20%). Sinus nodal artery (SNA) was found near the AM (MDCT, 100%; specimens, 90%) and AL lines (MDCT, 46.3%; specimens, 30%), while left coronary artery (LCA) and cardiac vein were closest to the PL lines. The trend of these findings was not significantly altered with the presence of AF.
CONCLUSIONS: The PL lines were shortest among the three mitral isthmus lines, but closest to LCA. Myocardium was thickest at the AL line, and SNAs were frequently found on the anterior lines. Multi-detector computed tomography provided detailed information, and further studies are required to clarify the clinical impact of these findings.