Abstract 2877: How Thin the Left Posterior Atrial Myocardium is! The Observation from 3D Scanned Image by 64ch Multi-detector CT and Its Implication for Radiofrequency Ablation of Atrial Fibrillation
Background: Pulmonary vein (PV) isolation is a useful measure for treatment of paroxysmal or persistent atrial fibrillation. However, this procedure is occasionally complicated with cardiac tamponade or atrio-esophageal fistula. To avoid such a complication, precise measurement of the left atrial (LA) wall thickness is mandatory. To this end, we investigated if a newly developed 64ch multi-detector CT (64ch MDCT) is useful to obtain this information in the beating human heart.
Method: 100 patients with ischemic heart disease or atial fibrillation underwent 64ch MDCT (GE, U.S.A.). LA myocardial thickness was measured at 5–10mm apart from each PV ostium toward septal, inferior, posterior, superior and lateral wall directions with accuracy of 0.3 mm. Total measurements were performed in 46 points in each patient.
Results: LA myocardial tissue was identified anatomically and radiologically using 3D scanned images. CT No. of 87±6 and 92±7 were defined as the anterior and posterior LA walls, respectively. These values were adequate enough to distinguish LA from other tissues such as fat, esphagus, etc. LA myocardial thickness measured 2.0±0.5 mm at the midseptum 10 mm apart from the right superior PV. A similar value was obtained around right inferior PV. In the lateral free wall near left superior and inferior PV’s, LA myocardial thickness was slightly smaller at 1.7±0.7 mm (not significant compared with septal thickness). However, LA posterior wall thickness near left superior and inferior PV’s measured 1.3±0.5 and 0.8±0.4 mm, respectively. These values were significantly smaller than the values obtained at septal wall (P<0.05). Furthermore, LA posterior myocardiuim was often invisible (<0.3 mm) at the esophagus site implying that myocardial tissue is lacking and fibrous and/or fatty tissue may be present there.
Conclusions: 64ch MDCT enables us to scan entire LA myocardium and give us precise anatomical information on its thickness. In general, LA is thick in the vicinity of right superior and inferior PV’s, but thin at the posteroinferior site near left inferior PV. 64ch MDCT is highly valuable for detection of localized thin atrial wall and subsequently for prevention of cardiac tamponade and atrio-esophageal fistula from occurrence during ablation.