Pediatric Surgery for Unroofed Coronary Sinus 

Updated: Jan 04, 2016
Author: Sergey G Toshinskiy; Chief Editor: John Kupferschmid, MD 

Overview

Background

Unroofed coronary sinus (UCS) is a rare atrial septal defect (ASD) that results in an abnormal communication between the coronary sinus and the left atrium. It is usually associated with other forms of congenital heart disease, typically heterotaxy syndromes. It is frequently associated with a persistent left superior vena cava (PLSVC), which is the most common anomaly of systemic venous drainage.[1]  

History Of The Procedure

Symptomatology stems from left-to-right shunting through the communication between the UCS and the left atrium and from right-to-left shunting, if there is a PLSVC draining deoxygenated blood from the left upper body into the left atrium. Dyspnea,[2, 3] right-sided heart enlargement,[2, 3] and cyanosis[4] have been reported in adults and children.[5] The presence of a PLSVC also creates the risk of brain abscess and paradoxical embolization.[6]

When left untreated, this defect has been reported to cause right-sided heart failure.[7] Chauvin et al have hypothesized that failed ablation procedures in adults, such as the Cox maze, could be attributable to an undiagnosed coronary sinus ASD; in essence, the ASD provides a means of a residual conduction pathway.[8] If untreated, this defect may leave behind significant residual right-to-left shunting following surgical repair of other associated defects.[9]

Etiology

Coronary sinus ASDs account for less than 1% of all types of ASDs.[10] They are usually associated with other forms of congenital heart disease (eg, heterotaxy syndromes) or PLSVC. PLSVC occurs in 0.1-0.5% of the general population, with 8% draining into the left atrium.[5] UCS is seen in 75% of patients with a PLSVC that drains into the left atrium and is usually associated with other forms of congenital heart disease and heterotaxy syndromes.[1]

Pathophysiology

In normal fetal development, the paired anterior cardinal veins drain the upper body and extremities of the fetus and become connected by an oblique vessel. During the 8th week of embryological development, a communication forms between the veins (future innominate [brachiocephalic] vein). The distal end of the left anterior cardinal vein degenerates (forms the ligament of Marshall), and the remaining right anterior cardinal vein ultimately becomes the right superior vena cava (RSVC).

The distal end of the left anterior cardinal vein drains into the left horn of the sinus venosus (future coronary sinus) before it degenerates; this explains the drainage pattern of a PLSVC into the coronary sinus (see the image below). When a PLSVC drains into an UCS, obligate drainage to the left atrium results in the right-to-left shunt and cyanosis.[11] Failure of the distal left anterior cardinal vein to degenerate is possible with or without degeneration of the right cardinal veins.[1] A PLSVC can be the sole drainage of systemic venous blood in the upper extremities and the head or may occur in conjunction with a RSVC. With dual superior vena cavae (SVCs), a bridging innominate (brachiocephalic) vein is often not present.

Embryologic remnant resulting in persistent left s Embryologic remnant resulting in persistent left superior vena cava (PLSVC). The dotted line illustrates the degenerated left anterior cardinal vein. This posterior view illustrates how the left superior vena cava drains into the coronary sinus.

Presentation

Isolated UCS defects may not express any symptoms and can be found during the workup for a concomitant lesion in asymptomatic patients.[12, 13] When present, symptoms may range from mild cardiomegaly to overt congestive heart failure. The degree of volume overload is determined primarily by the size and degree of biatrial shunting.[2]

UCS should be suspected in a patient with a PLSVC and a history of brain abscesses or paradoxical emboli, in a patient with a left-to-right interatrial shunt with unexplained arterial oxygen desaturation,[13] or in the setting of a new-onset, poorly explained left-to-right shunt following cardiac surgery.[12] Coronary sinus ASDs have been reported to occur with several other congenital heart defects, such as endocardial cushion defects,[14] cor triatriatum, tetralogy of Fallot,[15] pulmonary atresia or stenosis, abnormal ventriculoarterial connection,[15] and anomalous pulmonary venous return.[10] It also has been reported in association with Noonan syndrome, which is characterized by ASDs with pulmonary stenosis and developmental delay.[16]

Indications

As in other ASDs, indications for surgical repair include complications from right-to-left shunting, right heart volume overload, paradoxical emboli, and brain abscesses.[6] UCS may be repaired when presenting with other cardiac lesions.

Relevant Anatomy

Coronary sinus type ASD is characterized by a communication between the coronary sinus and the left atrium. Several anatomic variations of this communication have been described, including partial fenestrations between the walls of the coronary sinus and left atrium to a complete atresia of the coronary sinus orifice. The "pure form" of this defect refers to total absence of the walls between the coronary sinus and left atrium, with a connection between a PLSVC and the left atrium in the presence of a heterotaxy syndrome.[5]

The PLSVC enters the pericardium anterior to the left pulmonary artery. It then runs posterior to enter the left atrium and drain through the coronary sinus to the right atrium. When the wall between the coronary sinus tube and left atrium fails to form, which is thought to be caused by the maldevelopment of the atriovenous fold, the systemic venous blood drains directly into the left atrium. This fenestration into the left atrium usually occurs between the left atrial appendage and the left upper pulmonary vein, as shown in the image below.[17] When this fold is missing, the defect is called a UCS or UCS-ASD.

The fenestration is seen draining between the left The fenestration is seen draining between the left atrial appendage and the pulmonary veins.

UCS has been classified morphologically into various types by Kouchoukos et al,[18] as follows:

  • Type I: Completely UCS with PLSVC

  • Type II: Completely UCS without PLSVC

  • Type III: Partially unroofed midportion of coronary sinus

  • Type IV: Partially unroofed terminal portion of coronary sinus

  • Unroofed sinus syndrome related to cor triatriatum and ASD

Contraindications

Surgery is contraindicated in the presence of major genetic abnormalities.

 

Workup

Imaging Studies

Echocardiography (3- or 2-dimensional) can reveal an unroofed coronary sinus (UCS) and/or persistent left superior vena cava (PLSVC). However, the diagnosis can be missed, even by those with experience, which can lead to a diagnosis made at the time of surgery.[5] Xie et al have estimated the diagnostic accuracy of transthoracic and contrast echocardiography for UCS at only 65%.[19] Injection of agitated saline into the left antecubital vein during echocardiography can confirm the diagnosis of a PLSVC. Bubbles are seen in the coronary sinus before appearing in the right heart.[7] Echocardiography findings can be inconclusive because deep structures such as the coronary sinus are not always well delineated.

When the echocardiography findings are inconclusive, further imaging may be necessary. Newer generations of multidetector CT (MDCT) scanners can offer 3-dimensional reconstructions of cardiac structures and require less time, making this imaging modality a favorable choice for uncooperative patients or pediatric patients.[13, 20] MDCT scanning has high spatial and temporal resolutions, multiplanar reconstruction capabilities, and a wide field of view, making it an excellent tool for the detection and characterization of defects and for the identification of associated anomalies of the heart and pulmonary vasculature.[21]

Cardiac MRI provides high contrast of the internal cardiac structures without the need for injection of contrast media.[11] ).

Cardiac catheterization can also confirm the presence of a PLSVC associated with an UCS atrial septal defect (ASD) via selective angiography of the systemic veins, coronary sinus, or left atrium.[5, 22]

 

Treatment

Medical Therapy

While in most cases the defect is associated with a more complex congenital heart lesion, excluding an interventional approach, device closure has been proposed recently as a possible nonsurgical option.[5]

Bernado et al reported device closure of a 9.5-year-old, 31-kg child with a coronary sinus atrial septal defect (ASD) and persistent left superior vena cava (PLSVC), through a catheter placed within the left superior vena cava (LSVC).[23] Torreset et al (2007) used a similar approach to close an unroofed coronary sinus (UCS) with a covered stent in a symptomatic 7-month-old infant.[24] Santoro et al (2013) reported transcatheter closure of a partial UCS, where the defect was distal in the coronary sinus, via implantation of a standard occluding device in an 8-year-old child.[25]

Depending on systemic venous drainage patterns, the LSVC can be occluded with an interventional technique or can remain draining systemic venous blood to the left atrium. In this situation, as well as when there are multiple fenestrations, surgical management may be more appropriate.[23, 24] Other contraindications to device closure include inadequate margins to seat the device, large defects, and infants who are too small to accommodate the delivery system.[26]

Surgical Therapy

The goals of surgical therapy include the separation of systemic venous drainage from pulmonary venous drainage, completion of the atrial septum, and management of the PLSVC, if present. This lesion can be repaired with standard bypass techniques, and systemic venous cannulation of the LSVC may be possible if the patient is not an infant or a neonate. As well, the PLSVC can be temporarily occluded if the period is brief and will aid visualization of the repair.

Intraoperative Details

Repair of a coronary sinus ASD without a PLSVC can be accomplished with a roofing procedure.[27] After cardiac arrest and right atriotomy, the defect is examined. If the atrial septum is intact, the fossa ovalis can be incised for increased exposure. Intraoperatively, a probe can be passed through the coronary sinus and visualized through an ASD to confirm the presence of an UCS.[2] The coronary sinus is unroofed into the left atrium, and a patch is placed to close the atrial septum and coronary sinus to the left side (see the image below).

A venous cannula stent opens the coronary sinus wh A venous cannula stent opens the coronary sinus while sutures are placed.

When the tissues are redundant, the defect can be closed primarily. When a PLSVC is not present, the amount of cyanosis from coronary blood return is incidental. After closure of the ASD, the presence of a residual leak can be determined by ventilating the lung and looking for evidence of pulmonary venous return from the coronary sinus.[2]

In each case of a PLSVC, the vessel is addressed on its own merits. If it is small and a bridging innominate vein is present, the PLSVC can be ligated. Others have recommended ligation when the occlusion pressure is less than 16 mm Hg.[28] If it is large and is the sole source of venous drainage for the upper extremities and head, an intra-atrial baffle can be considered (see the image below). Still, others have described extracardiac techniques (ie, reimplantation of the LSVC into the right atrium)[29, 30] or right superior vena cava (RSVC) when a bridging vein is absent.[31, 32]

A pericardial patch is used to baffle the pulmonar A pericardial patch is used to baffle the pulmonary veins directly toward the mitral valve. This approach allows unobstructed flow from the orifice of the left superior vena cava (LSVC) to drain to the right-sided atrium.

An intra-atrial baffle, however, can potentially result in pulmonary venous obstruction or mitral valve inflow obstruction.[2, 28, 29, 33] Bidirectional left superior cavopulmonary anastomosis is also described as a surgical option for patients with low pulmonary pressures.[30]

When a common atrium is present or when a coronary sinus is absent, landmarks for the conduction system are not available to the surgeon.[29] To remedy this and to avoid the area of conduction, de Leval has described the placement of sutures along the base of the septal leaflet of the tricuspid valve and then out onto the right atrial wall beyond the tricuspid valve annulus.[29]

Follow-up

For patient education resources, see the Heart Center, as well as Ventricular Septal Defect and Tetralogy of Fallot.

Complications

Complications are similar to other atrial level repairs. Risks of residual left-to-right or right-to-left shunting and risk of heart block or sinus node dysfunction are most commonly encountered. However, these ASDs are usually seen with other lesions, which may have more severe complications that take precedence.

Outcome and Prognosis

Outcome and prognosis for an isolated coronary sinus ASD are excellent, but the more serious lesions that can be associated may alter the overall outcome for the patient.

Future and Controversies

Results of surgical repair are closely related to the complexity of the associated lesions. A UCS should be suspected whenever a PLSVC is encountered on echocardiogram.