History
A 28-year-old female patient, suffering from a sudden onset of heart palpitation accompanied by atypical chest pain, was admitted to the emergency room. Dextrocardia was identified on an electrocardiogram and a chest X-ray and was confirmed by a transthoracic echocardiography. The 24-h Holter monitor showed frequent supraventricular extrasystoles and episodes of inappropriate sinus tachycardia. The patient reported no previous episode and her medical history was unremarkable. A chest CT angiography (CTA) was requested to rule out associated anomalies.
Diagnosis
CTA images showed a dextrocardia as well as an atrial and abdominal situs inversus. The atrioventricular and the ventricle-arterial connections were concordant, with the left ventricle positioned posteriorly to the right ventricle and the aorta positioned left-posteriorly to the pulmonary artery. The aortic arch was rightsided with a mirrored origin of the supra-aortic trunks. The main pulmonary artery (MPA) showed confluent branches without stenosis. The four pulmonary veins (PVs) draining into the left atrium (LA) were normal and the LA was located on the right. A persistent left superior vena cava (SVC), connecting to the right atrium (RA), was seen and no right SVC was present. The azygos-hemiazygos system was hypertrophic and dilated. The origins and the courses of the left and right coronary arteries were normal. There were two lung lobes bilaterally, as well as a left bronchial isomerism with eparterial left accessory bronchus. Below the chest, the liver was seen on the left along with the right-sided polysplenia and gastric bubble. The suprahepatic portion of the inferior vena cava connecting to the right atrium was observed. CT findings led to a diagnosis of a situs inversus totalis (SIT). The treating physicians considered the chest pain was caused by a right intercostal neuritis, non-cardiac origin, and the sinus tachycardia was related to a mild anxiety disorder. The patient was treated with analgesics, anti-inflammatories and anxiolytics, and reported remission of symptoms.
Figs. 1: cVRT images with anterior (Fig. 1a) and posterior view (Fig. 1b) show a dextrocardia, right aortic arch with mirrored origin of the supra-aortic trunks, MPA with confluent branches without stenosis, four PVs draining into the LA and a persistent left SVC connecting to the RA.
Fig. 2: cVRT images show the normal course of the coronaries.
Fig. 3: An axial image (Fig. 3a) shows a dextrocardia with concordant atrioventricular connections. An oblique thin MIP image (Fig. 3b) reveals the normal origins of the coronaries. An axial cVRT image at the lower level of the chest (Fig. 3c) shows the left-sided liver and the right-sided polysplenia (arrow) as well as the gastric bubble (asterisk). A cVRT image shows a hypertrophic and dilated azygos-hemiazygos system (Fig. 3d, arrows).
Fig. 4: Two different presentations of the bronchial tree show a left bronchial isomerism with eparterial left accessory bronchus (arrows).
Comments
SIT, also termed as “mirror man”, is a very rare congenital abnormality in which both thoracic and abdominal viscera are reversed 180°. Usually, it is asymptomatic, however, it can pose great challenges in the interventional or surgical procedures due to the mirrored effect, since most surgeons are right-handed. Although both chest radiograph and ultrasound are useful for the initial diagnosis, CT and MRI are the modalities of choice to confirm and outline the full underlying anatomic variations, allowing for an early management of the anomalies and guidance for the best approaches. This case is performed on a dual source CT scanner, SOMATOM Force, using an ECG triggered spiral scan mode – the “Turbo Flash mode”. It applies an ultra-high pitch of 3.2 providing an acquisition speed of 737 mm/s. Two acquisitions of the entire thoracic aorta and the heart are completed in just 0.29 and 0.17 seconds, in free breathing. Optimized lower kV (80 kV & 70 kV) scan protocols are selected to enhance contrast and to reduce the radiation dose. Owing to the high spatial and temporal resolution (66 ms), the anatomical details, including the origins and the courses of the coronary arteries are depicted with an optimal image quality. Furthermore, cinematic volume rendering technique (cVRT) is used to facilitate a lifelike demonstration of the complexity of the SIT, assisting in preprocedural planning and follow-ups.
Examination Protocol