The advantage of ICE-assisted ablation is obvious. Through the rotation, advance, retreat and bending of ultrasonic catheter, the heart structure and the adhesion between catheter and tissue can be seen at a glance. ICE combining with Carto3 is even more powerful. It can directly establish a three-dimensional model of the heart on the electrophysiological mapping system, so as to guide the operator to operate the catheter under very low radiation quantity. The author's personal experience is that the learning curve of ICE manipulation is significantly shorter than that of ablation catheter manipulation. Therefore both the popularity of this technology and the accuracy of the cardiac cavity model constructed by ICE is high. Combining with the pressure sensing catheter, the catheter can be safely and smoothly sent to any position of the cardiac cavity under zero ray. It greatly reduces radiolesion. If the patient cannot receive coronary CT angiography or esophageal ultrasonography for some reason before operation, he can choose ICE to assist radiofrequency ablation of atrial fibrillation. ICE can clearly display the left atrial structure and exclude of thrombus.
Can the mapping and ablation that guided by ICE improve the success rate of ablation? Fei et al. concluded through the follow-up of 110 patients with PAF receiving ablation that ICE has no advantage in effectiveness . Our study showed that the ablation success rate in ICE group was higher than that in control group, but there was no significant difference. We believe that one of the reasons is that after the application of ICE, the puncture point of atrial septum is ideal, which is convenient for the manipulation of ablation catheter. Because of this there are relatively few leakage points. The second reason is that the atrial model built by ICE has high simulation. These are two reasons why the ablation success rate was higher in ICE group. But in our study the size of the left atrium of AF patients in ICE group was larger than that of AF patients in control group. A meta-analysis of 22 clinical studies which related to atrial fibrillation ablation from 2004 to 2011 concluded that the enlarged left atrium significantly increased the recurrence rate of atrial fibrillation after radiofrequency ablation . Therefore, our study shows that ICE assisted radiofrequency ablation of atrial fibrillation can improve the success rate, but its advantage is still limited by the size of the left atrium.
Improper atrial septal puncture is the main cause of pericardial tamponade during catheter ablation of atrial fibrillation. In 2007, the literature reported that the incidence of pericardial tamponade in the perioperative period of atrial fibrillation radiofrequency ablation was 3% . In 2013, aldhoon et al reported that the incidence of pericardial tamponade during perioperative period of radiofrequency ablation of atrial fibrillation with ICE was only 0.25% . Due to the application of ICE the operator can look directly at the atrial septum and puncture the septum when the Tent Sign and Rabbit Ear Sign appear, so as to avoid damaging the aorta, the posterior wall of the left atrium or the left atrial appendage. For patients with anatomical abnormalities, such as flat and narrow left atrium (anterior and posterior diameter < 30mm), aortic aneurysm, dextrocardia, atrial septal thickening or atrial septal bulge, ICE ensures the correctness of puncture and facilitates the subsequent catheter ablation. Similar patients were also encountered in this study. All patients successfully punctured the atrial septum under the guidance of ICE. No complication occurred during atrial septal puncture in ICE group. In control group, 3 cases had pericardial tamponade at this time. In addition, during radiofrequency ablation ICE being sent into the right ventricle can be used to monitor and detect pericardial effusion in real time. In this study, one patient in ICE group was found pericardial effusion after right upper pulmonary vein supplementary ablation, but the patient had no obvious discomfort and abnormal vital signs. If there was no ICE, the complication would not be noticed in time. The patient recovered after pericardiocentesis. Although the diameter of ICE catheter was 10F, the complications caused by femoral vein puncture showed no difference between the two groups.
The safety of ICE is also reflected in its ability to display the relationship between esophagus and posterior wall of left atrium in real time during ablation. The esophagus is located behind the left atrium and 3.3-13.5mm away from the atrium. Whether the esophagus is left or right behind the left atrium can be determined by cardiac CT or MRI before operation, but the positional relationship between the esophagus and the left atrium may change during atrial fibrillation ablation . ICE can observe the position of the two in real time during ablation, which is also a more reliable means to observe the position relationship between the esophagus and the posterior wall of the left atrium during atrial fibrillation ablation. In this study, the position of the esophagus was marked on the posterior wall of the model of the left atrium of every patient in ICE group. Its relationship with the left and right pulmonary veins was clear at a glance. During ablation, the ablation power and time were appropriately reduced near the esophagus, so as to reduce the damage to the esophagus. Therefore after atrial fibrillation ablation cases with injuries of peripheral esophageal vagus nerve in ICE group were less than that in control group.