The left atrium extra-appendicular pectinate muscles of the mitral isthmus detected by multislice computed tomography: Implications for the safety of atrial fibrillation catheter ablation

Abstract

Previous anatomical studies in human hearts have demonstrated muscular trabeculations and remnants of extra-appendicular pectinate muscles (PM) at the area of the left mitral isthmus (LMI), between the ostium of the left inferior pulmonary vein and the mitral valve annulus. The areas in between the muscular trabeculas at this region of the LMI are large enough to trap an ablation catheter leading to excessive tissue heating and eventual tamponade due to a pop phenomenon. A prospectively acquired 64-Detector Cardiac Computed Tomography Angiography (CTA) was performed in 60 consecutive patients (mean age 57±6 years, 43 males). We analyzed the presence and anatomical characteristics of the extra-appendicular PM along the LMI. In 20 cases (33%), the anterior ostial margin of the left atrial appendage (LAA) did not present as a clear-cut border and muscular trabeculations were found extending inferiorly from the LAA to the vestibule of the mitral valve. They were all located at the posterior LA wall, extending to the mitral valve. The average distance between the PM and the ostium of the LAA was 11,9 mm (Range 3,9 to 31 mm). The regions in between the extra-appendicular PM were found to have a thinner wall, compared to the rest of the LA posterior wall. In conclusion,the detection of extra-appendicular posterior pectinate muscles by Multidetector CTA has not been previously reported. This information could be relevant to perform the procedures of atrial fibrillation ablation more safely.