Introduction :
The left atrial appendage (ALL) is a small muscular extension of the left atrium (LA). It is closely related to the left pulmonary veins, anatomically it lies anteriorly in the left atrioventricular sulcus in close proximity to the left circumflex artery [1]. Left atrial appendage develops in 3rd -4th week of embryonic life from the left wall of the primary atrium and functions like a left atrium during the fetal life [2]. In adults it is believed to function as a decompression chamber during elevated left atrial pressure including left ventricular systole or volume overload situations. It also contributes towards left atrial reservoir and contractile functions [3]. The LAA, however, is the most common source of thromboembolism in patients with atrial fibrillation (AF) and may be an arrhythmogenic source for the maintenance of AF[4]。According to the data analysis, there are 91% of intracardiac thrombosis associated with nonvalvular AF that are found in the LAA[5].Therefore it is urgent to distinguish and prevent the occurrence of left atrial appendage thrombosis. Although The morphology of the left atrial appendage is highly variable among individuals, the absence of ALL is quite rare anatomical variation that clinical significance has not been discovered yet. We are going to report a case of congenital absence of LAA diagnosed by Real-time 3D transesophageal echocardiography (RT 3D TEE).
Case report :
A 68-year-old woman with a medical history of hypertension (HTN) for 2 years, diabetes mellitus (DM) for 15 years, cerebral infarction for 5 years, and paroxysmal atrial fibrillation for the past 13 years, additionally there were radio frequency catheter ablation for three times for rhythm control in the past 10 years. Because of frequent palpitations, the left atrial appendage was planned to be occlusion, clinicians scheduled a transesophageal echocardiogram, as a pre-operative procedure, for morphologic evaluation of LAA and to exclude thrombus before the closure procedure. LAA was not visualized in the whole process (figure 1). In order to confirm, we checkup patient‘s other relevant imaging history, the patient had no previous history of surgical or percutaneous left atrial appendage exclusion or occlusion, and there was Computed tomography angiogram of the pulmonary veins proceeded before which showed no sign of imaging structure of LAA (figure 2). Then the congenital absence of left atrial appendage was diagnosed and no thrombosis in the left atrium was confirmed by RT 3D TEE. Carotid plaques were found in a cursory scan of the carotid artery before transesophageal ultrasound, we assumed that unstable Carotid plaques may be the main risk factor of cerebrovascular events in this case (figure 3).
Anticoagulation therapy with warfarin was continued as per current guidelines since we have no data on anticoagulation management in congenital absence of left atrial appendage.