4.3 The LAPW myocardium and the fat pad
No relationship was found between the LA diameter, age, gender, BMI, type of AF (PAF or PsAF), and the thickness of the LAPW myocardium under CPL and MPL. The thickness of LAPW myocardium could vary from different measurements. A cadaver study reported the myocardium was thicker in the inferior region (close to coronary sinus) than in the middle region (close to inferior PV), and the roofline region was the thinnest.13 This result was comparable with our study in which we also observed that the myocardium inferior PV region corresponded to the lower region of MPL, while the middle region corresponded to the region of CPL. From the CT study, however, Lemola et al12 reported that the thickness of LAPW myocardium was 2.2 ± 0.9mm with no difference from superior to inferior regions. Suenari et al19 reported that in cases where there were close contacts between the esophagus and left PV atrium, the distance was about 1.79 ± 0.22mm. These measurements indicated that the LAPW musculature was quite thin in the inferior PV region. Indeed, the thickness of LAPW myocardium in the region of CPL almost represents the distance between the endocardium of LAPW and the esophagus,11 because a lower fat pad is presented between the CPL and the esophagus. It was reported the fat pad was mainly located in the superior and inferior part of LAPW19 and it was thinnest at the level between the orifices of the inferior PV13 where the CPL was located. Consistent with our study, only 18.6% of CPL with a fat pad was observed, whereas 74.5% of MPL with a fat pad was noticeable. Therefore, the higher presence of a fat pad in the MPL might serve as a protection of esophageal ablation injury.