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.