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A 53-year-old man presented to our hospital with acute coronary syndrome and underwent uncomplicated cardiac catheterization with percutaneous coronary intervention. As part of an institutional research protocol for the evaluation of the recently placed left circumflex stent, he underwent coronary CT angiography with ECG-gated contrast-enhanced 64-slice multidetector computed tomography (CT) (Sensation Cardiac 64, Siemens Medical Solutions, Forchheim, Germany). Incidental note of an unroofed coronary sinus (CS) was made on the coronary CT angiogram (Figure 1A-1D). The defect size measured by CT was 2.1 cm × 0.4 cm and its distance from the CS ostium was 2.1 cm. In addition to its normal connection to the right atrium (RA), the CS had a direct connection with the left atrium (LA) as noted by the contrast shunting from the LA into the CS, and subsequently into the RA (Figure 1D). No other congenital anomalies including persistent left superior vena cava (LSVC) were identified on the CT. Clinically the patient had no prior history of strokes, hypoxia, or heart failure symptoms. His twelve-lead surface electrocardiogram (Figure 2) showed normal sinus rhythm without evidence of chamber enlargement. The chest topogram from the CT (Figure 3) revealed clear lungs with normal heart size. His transthoracic echocardiogram (Movie 1) showed mild left atrial enlargement (AP diameter of 4.0 cm) with the other chambers normal in size, normal biventricular function, and no significant valvular disease. The coronary sinus in the parasternal long-axis view (Figure 4) was mildly dilated, measuring 1.4 cm × 1.0 cm. However, agitated saline study injected into the left upper extremity with provocative maneuvers did not show bubbles in the coronary sinus nor left cardiac chambers to suggest either the present of a persistent LSVC or a right-to-left shunt (Movie 2).
Unroofed coronary sinus is a rare congenital cardiac anomaly in which there is partial (either focal or fenestrated) or complete absence of the roof of the CS, resulting in a communication between the CS and the LA. Classified as an atrial septal defect (ASD), unroofed CS is the rarest type of ASD.1 It is often associated with persistent LSVC and other forms of complex congenital disease, usually heterotaxy syndromes. The morphological types have been classified into four groups: type I, completely unroofed with persistent LSVC; type II, completely unroofed without persistent LSVC; type III, partially unroofed mid portion; and type IV, partially unroofed terminal portion (as illustrated in our case). The fenestration into the LA typically occurs between the left atrial appendage and the left upper pulmonary vein. The size of the defect and degree of left-to-right shunt generally determines the clinical presentation. The spectrum of symptoms may range from asymptomatic to nonspecific complaints to severe dyspnea with symptoms of overt right heart failure from chronic right ventricular volume overload. The diagnosis should be considered when evaluating an unknown cardiac murmur, right heart enlargement, transient cyanosis or hypoxia, or paradoxical embolism. Management is guided by the presence of clinical symptoms with surgical repair consideration when symptoms prevail.
Transthoracic echocardiography is the most widely used imaging modality for suspected unroofed CS but is limited in its ability to visualize the posterior cardiac structures such as the coronary sinus and pulmonary veins. Transesophageal echocardiography (TEE) and cardiac magnetic resonance imaging (CMR) can more accurately assess these posterior structures but were not indicated in this incidental case due to patient's lack of symptoms and thus not performed. Multi-detector CT with its excellent spatial resolution also allows for the visualization and accurate anatomic and morphologic evaluation of the posterior structures of the heart. With the widespread use of cardiac CT for coronary artery assessment, incidental findings of asymptomatic congenital heart disease are not a rare occurrence. Other non-coronary artery anatomic structures such as the coronary veins are easily visualized with gated cardiac CT, which is emerging as a potentially useful noninvasive imaging modality for the evaluation of the coronary venous system.
A prior case report has documented indirect evidence of an unroofed CS with persistent LSVC (Type I) on a conventional chest CT study.2 We herein report a rare case of an isolated unroofed coronary sinus (Type IV, partially unroofed terminal portion without persistent LSVC) atrial septal defect that was diagnosed as an incidental finding on cardiac MDCT. Further hemodynamic evaluation using either Doppler analysis with TEE or phase contrast imaging with CMR to quantify the degree of intracardiac shunt is warranted should patient develop symptoms of ASD physiology (i.e. left-to-right shunting), show signs of right heart volume overload, or be considered for surgical repair.
Movie 1. Parasternal long-axis view of the transthoracic echocardiogram showed mild left atrial enlargement, normal left ventricular function, and a mildly enlarged left coronary sinus at the left atrioventricular groove. Best viewed with Windows Media Player.
Movie 2. Apical four-chamber view of the transthoracic echocardiogram with agitated saline injection into the left upper extremity with provocative maneuvers showed bubbles infiltrating the right cardiac chambers but failed to demonstrate bubbles in the coronary sinus nor left cardiac chambers, thus, did not suggest the present of a persistent left superior vena cava or right-to-left shunt. Best viewed with Windows Media Player.
Disclosures: Dr. Truong has received support from NIH grant T32HL076136 and L30 HL093896.
Molly Thangaroopan, Cardiac MR PET CT Program, Department of Radiology, Massachusetts General Hospital, Boston, MA, 02114.
Quynh A. Truong, Cardiac MR PET CT Program, Division of Cardiology and Department of Radiology, Massachusetts General Hospital, Boston, MA, 02114.
Manudeep Kalra, Cardiac MR PET CT Program, Department of Radiology, Massachusetts General Hospital, Boston, MA, 02114.
Kibar Yared, Division of Cardiology, Massachusetts General Hospital, Boston, MA, 02114.
Suhny Abbara, Cardiac MR PET CT Program, Department of Radiology, Massachusetts General Hospital, Boston, MA, 02114.