The effects of fat layer on temperature distribution during microwave atrial fibrillation catheter ablation

To investigate the effects of fat layer on the temperature distribution during microwave atrial fibrillation catheter ablation in the conditions of different ablation time; 3D finite element models (fat layer and no fat layer) were built, and temperature distribution was obtained based on coupled electromagnetic-thermal analysis at 2.45 GHz and 30 W of microwave power. Results shown: in the endocardial ablation, the existence of the fat layer did not affect the shape of the 50 °C contour before 30 s. The increase speed of depth became quite slowly in the model with fat layer after 30 s. When ablation depth needed fixed, there are no significant effect on effectively ablation depth whether fat layer over or not. However, the existence of fat layer makes the temperature lower in the myocardium, and maximum temperature point closer to the myocardium surface. What is more, in the model with fat layer, effective ablation reach lower maximum temperature and the shallower depth of 50 °C contour. But there are larger ablation axial length and transverse width. In this case, doctor should ensure safety of normal cardiac tissue around the target tissue. In the epicardial ablation, the existence of fat layer seriously affects result of the microwave ablation. The epicardial ablation needs more heating time to create lesion. But epicardial ablation can be better controlled in the shape of effective ablation area because of the slowly increase of target variables after the appearing of 50 °C contour. Doctor can choose endocardial or epicardial ablation in different case of clinic requirement.