Atrial fibrillation (AF) is the most common arrhythmia. Worldwide, the incidence of atrial fibrillation in men and women is 596.2 per 100,000 and 373.1 per 100,000, respectively. [1] The prevalence of AF in China is 0.97%.[2] AF increases the risk of stroke, heart failure and death. Ischemic stroke occurs in 25% of hospitalized patients with nonvalvular atrial fibrillation according to a single-center clinical study in China. [3,4] Complications associated with AF place a huge burden on the healthcare system, with an estimated 4.9 billion RMB for patients with AF in China, 89% of which are caused by AF-related strokes.[5]

According to the 2018 AHA/ACC/HRS guideline [6], catheter ablation was recommended for paroxysmal AF that is symptomatic and refractory or intolerable to at least one class I or III antiarrhythmic drug. Transesophageal echocardiography (TEE) is a necessary preoperative examination for catheter ablation of patients with AF in order to exclude thrombus in the left atrium and left atrial appendage (LAA) and to prevent thrombotic complications caused by thrombus shedding during the procedure. However, TEE detection, like gastroscopy, requires transpharyngeal insertion of the probe into the esophagus and should be fasted before it. The TEE probe is thicker than the gastroscope, which can increase the discomfort of the patient during the examination. At the same time, if the patient cooperates poorly during the delivery process, the probe may damage the oropharyngeal or esophageal mucosa, causing complications such as bleeding or perforation.

Intracardiac echocardiography (ICE) is a new technique that can completely replace TEE in excluding thrombus in left atrium and left atrial appendage. The advantages are that the catheter is inserted from the femoral vein without the discomfort of stimulating the swallowing reflex caused by TEE examination; To avoid complications such as bleeding or perforation caused by injury to oropharynx or esophageal mucosa; It can be used in frail, elderly, pharyngeal or esophageal lesions (eg, ulcers, varices), or intolerable patients. Some studies have shown that ICE is an important test for the diagnosis of LAA thrombosis, especially when thrombus is described as a soft thrombus.

TEE is the gold standard for the detection of thrombi in the LAA before catheter ablation for AF. ICE is used to assist AF ablation; however, ICE is also accurate for LAA visualization and minimizes the complications during procedures[7].

The primary purpose of this study aimed at determining whether ICE could replace TEE by minimizing the procedural-related complications but not compromise the detection of thrombi in the LAA.

Inclusion Criteria:

1. Aged 18-80 years.
2. Willing to sign informed consent.
3. Patients diagnosed with atrial fibrillation Paroxysmal AF and Persistent AF according to the latest clinical guidelines.

Exclusion Criteria:

1. End-stage disease with a mean life expectancy less than 1 year
2. New York Heart Association (NYHA) class III or IV, or last known left ventricular ejection fraction less than 30%
3. Previous surgical or catheter ablation for AF
4. Bradycardia and presence of implanted ICD
5. Uncontrolled hypertension: Systolic blood pressure (SBP) >180 mmHg or diastolic blood pressure (DBP) > 110 mmHg
6. Patients with Cardiovascular events including acute myocardial infarction, any PCI, valvular cardiac surgical, or percutaneous procedure within the past 3 months
7. Women of childbearing potential who are, or plan to become, pregnant during the time of the study
8. Have been enrolled in an investigational study evaluating devices or drugs.