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eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Cardiothoracic Surgery

Atrial Septal Defect, Unroofed Coronary Sinus: Surgical Perspective

Samuel Weinstein, MD, Associate Professor, Albert Einstein College of Medicine; Director, Department of Pediatric Cardiothoracic Surgery, The Children's Hospital at Montefiore
Robert E Michler, MD, Samuel I Belkin Chair, Professor and Chairman, Department of Surgery, Professor and Chairman, Department of Cardiothoracic Surgery, Albert Einstein College of Medicine; Surgeon-in-Chief, Chairman, Department of Surgery and Chairman, Department of Cardiothoracic Surgery, Co-Director Montefiore-Einstein Heart Center, Montefiore Medical Center; Suzanne Courtwright, MS, CPNP-AC, Pediatric Nurse Practitioner, Department of Pediatric Cardiothoracic Surgery and Adult Congenital Heart Surgery, Montefiore Medical Center

Updated: Jan 28, 2009

Introduction

Coronary sinus atrial septal defects (ASDs) are rare and are usually associated with other forms of congenital heart disease, usually heterotaxy syndromes. They are also frequently associated with a persistent left superior vena cava (LSVC), which is the most common anomaly of systemic venous drainage.1

History Of The Procedure

Symptomatology stems from right-to-left shunting, the amount of which is related to the size of the defect and the presence or absence of a persistent LSVC draining into or through it. Dyspnea and cyanosis have been reported in adults and children.2 The presence of a persistent LSVC also creates risk for brain abscess and cerebral emboli.3 When left undiagnosed, this defect has been reported to cause right heart failure in adults.4  Chauvin et al (2000) 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.5  If undiagnosed, this defect may leave behind a significant residual right-to-left shunting following surgical repair of other associated defects.6

Etiology

Coronary sinus ASDs comprise less than 1% of all types of atrial septal defects.7  They are usually associated with other forms of congenital heart disease (eg, heterotaxy syndromes) or persistent LSVC. Persistent LSVC occurs in 0.1-0.5% of the general population, with 8% draining into the left atrium.2 Unroofed coronary sinus ASD is seen in 75% of patients with an LSVC 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 8-week period of embryological development, a communication forms between the veins, which becomes the innominate vein. The distal end of the left anterior cardinal vein degenerates, 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 coronary sinus before it degenerates; this explains the drainage pattern of a persistent LSVC into the coronary sinus. Failure of the distal left anterior cardinal vein to degenerate is possible with or without degeneration of the right cardinal veins.1 A persistent LSVC can be the sole drainage of systemic venous blood in the upper extremities and the head or may occur in conjunction with an RSVC. With dual superior vena cavae (SVCs), a bridging innominate vein is often not present.

Presentation

Patients usually present with symptoms related to their concomitant defects. Unroofed coronary sinus ASD is difficult to diagnose based on clinical signs and symptoms alone and should be suspected in a patient with an LSVC and a history of brain abscess or cerebral emboli or in a patient with a left-to-right interatrial shunt with unexplained arterial oxygen desaturation. Suspect a brain abscess or a cerebral embolism whenever an LSVC is seen on an echocardiograph. Coronary sinus ASDs have been reported to occur with several other congenital heart defects, such as canal defects,8 cor triatriatum, tetralogy of Fallot,9 pulmonary atresia or stenosis, abnormal ventriculoarterial connection,9 and anomalous pulmonary venous return.7 It also has been reported in association with Noonan syndrome, which is characterized by ASDs with pulmonary stenosis and developmental delay.10

Indications

As in other atrial septal defects (ASDs), indications for surgery include symptoms of ASD physiology (eg, left-to-right shunting), right heart volume overload, and risk of cerebral embolism. Indications for surgical repair include complications from right-to-left shunting, including cerebral emboli and brain abscesses.3 They may be repaired when they present with other cardiac lesions.

Relevant Anatomy

Coronary sinus type atrial septal defect (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 of a persistent left superior vena cava to the left atrium in the presence of a heterotaxy syndrome.2

The left superior vena cava (LSVC) 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 a maldevelopment of the arteriosinus 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.11 When this fold is missing, the defect is called an unroofed coronary sinus or unroofed coronary sinus ASD.

Contraindications

Surgery is contraindicated in the presence of major genetic abnormalities.

Workup

Imaging Studies

Echocardiography and MRI can reveal a left superior vena cava (LSVC) before surgery; however, the diagnosis can be missed, even by those with experience, which can lead to a diagnosis made at the time of surgery.2 Injection of agitated saline into the left antecubital vein during echocardiography can confirm the diagnosis of a persistent LSVC. Bubbles are seen in the coronary sinus before appearing in the right heart.4  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. Cardiac MRI provides high contrast of the internal cardiac structures without the need for injection of contrast media. Newer generations of helical CT 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.12 Cardiac catheterization can also confirm the presence of an LSVC associated with an unroofed coronary sinus atrial septal defect (ASD) via selective angiography of the coronary sinus and the left atrium.13,2

Treatment

Medical Therapy

Device closure with an Amplatzer device has been proposed as a nonsurgical option;2 however, in most cases, the defect is associated with a more complex congenital heart lesion, thereby excluding this approach as a feasible option.

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 left superior vena cava (LSVC), if present. This lesion can be repaired with systemic venous cannulation of the LSVC, right superior vena cava (RSVC), and inferior vena cava (IVC); right atriotomy and cardiac arrest; or with circulatory arrest if the patient is an infant or neonate.

Intraoperative Details

Repair of a coronary sinus atrial septal defect (ASD) without a LSVC can be accomplished with a roofing procedure.14 After cardiac arrest and right atriotomy, the defect is examined through the atrial septum. If the atrial septum is intact, the fossa ovalis is incised for exposure. When the tissues are redundant, the defect can be closed primarily.

Another approach is to use a cannula or obturator introduced into the coronary sinus toward the left atrium to stent the area while a roof of pericardial tissue is created.15 The patch runs from a location between the left atrial (LA) appendage and upper pulmonary veins, continuing inferiorly toward the mitral valve, and terminating near the right atrium and right atrial orifice of the coronary sinus. Bites are placed superficially toward the right side of the atrium to avoid injury to conduction tissue.15 The atrial septum is then repaired primarily or with a patch.

If an LSVC is present, the repair can be performed in a similar manner, or with an intra-atrial baffle to help avoid narrowing of pulmonary veins or obstruction of the mitral valve.15,16,17 After cardiac arrest and right atriotomy, the atrial septum is first incised for exposure if the ASD is small or nonexistent. A patch of pericardium serves as a baffle, separating the orifice of the left SVC from the pulmonary veins. This allows the pulmonary venous blood to drain toward the mitral valve, whereas the systemic venous blood drains directly to the right atrium. When a common atrium is present or when a coronary sinus is absent, landmarks for the conduction system are not available to the surgeon.15 To remedy this and to avoid the area of conduction, de Leval has described placement of the 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.

In each case, the left SVC is addressed on its own merits. If it is small and a bridging innominate vein is present, the left SVC can be ligated. Others have recommended ligation when the occlusion pressure is less than 16 mm Hg.17 If it is large and is the sole source of venous drainage for the upper extremities and head, an intraatrial baffle can be considered. Still, others have described extracardial techniques (ie, reimplantation of the LSVC into the right atrium)18,15 or RSVC when a bridging vein is absent.19  Bidirectional left superior cavopulmonary anastomosis is also described as a surgical option for patients with low pulmonary pressures.18

Postoperative Details

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.

Follow-up

For excellent patient education resources, visit eMedicine's Heart Center. Also, see eMedicine's patient education articles Ventricular Septal Defect and Tetralogy of Fallot.

Complications

Complications are similar to other atrial level repairs. Risks of residual left-to-right shunting and risk of heart block or sinus node dysfunction are most commonly encountered. However, these atrial septal defects (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 a patient.

Future and Controversies

Results of surgical repair are closely related to the complexity of the associated lesions also being operated on. An unroofed coronary sinus should be suspected whenever a left superior vena cava (LSVC) is encountered on echocardiogram. Failure to repair these defects results in excessive blood return to the heart and a residual right-to-left shunt.

Debate on this topic is negligible because this atrial septal defect (ASD) is a very rare lesion (most centers may see 1-2 a year). A minimally invasive approach could be discussed, but these ASDs are observed in children who usually have other more complex problems; thus, a minimally invasive approach often does not apply.

Multimedia

The dotted line illustrates the degenerated left ...

Media file 1: 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.

The fenestration is seen draining between the lef...

Media file 2: The fenestration is seen draining between the left atrial appendage and the pulmonary veins.

3A: A venous cannula stent opens the coronary sin...

Media file 3: 3A: A venous cannula stent opens the coronary sinus while sutures are placed. 3B: A pericardial patch is used in a roofing procedure.

A pericardial patch is used to baffle the pulmona...

Media file 4: 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 to drain to the right-sided atrium.

References

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Keywords

atrial septal defect, unroofed coronary sinus, ASD, coronary sinus atrial septal defect, coronary sinus ASD, persistent left superior vena cava, persistent LSVC, left superior vena cava, LSVC, left SVC, right superior vena cava, RSVC, right anterior cardinal vein, left anterior cardinal vein, coronary sinus, unroofed coronary sinus atrial septal defect, unroofed coronary sinus ASD, brain abscess, heart failure, heterotaxy syndrome, cor triatriatum, tetralogy of Fallot, pulmonary atresia, pulmonary stenosis, anomalous pulmonary venous return, Noonan syndrome

Contributor Information and Disclosures

Author

Samuel Weinstein, MD, Associate Professor, Albert Einstein College of Medicine; Director, Department of Pediatric Cardiothoracic Surgery, The Children's Hospital at Montefiore
Samuel Weinstein, MD is a member of the following medical societies: American College of Surgeons, American Heart Association, American Medical Association, Ohio State Medical Association, and Society of Thoracic Surgeons
Disclosure: Nothing to disclose.

Coauthor(s)

Robert E Michler, MD, Samuel I Belkin Chair, Professor and Chairman, Department of Surgery, Professor and Chairman, Department of Cardiothoracic Surgery, Albert Einstein College of Medicine; Surgeon-in-Chief, Chairman, Department of Surgery and Chairman, Department of Cardiothoracic Surgery, Co-Director Montefiore-Einstein Heart Center, Montefiore Medical Center
Robert E Michler, MD is a member of the following medical societies: American Association for Thoracic Surgery, American College of Cardiology, American College of Surgeons, American Medical Association, American Society for Artificial Internal Organs, American Society of Transplant Surgeons, International Society for Heart and Lung Transplantation, and Society of Thoracic Surgeons
Disclosure: Nothing to disclose.

Suzanne Courtwright, MS, CPNP-AC, Pediatric Nurse Practitioner, Department of Pediatric Cardiothoracic Surgery and Adult Congenital Heart Surgery, Montefiore Medical Center
Suzanne Courtwright, MS, CPNP-AC is a member of the following medical societies: American Academy of Pediatrics, American Nurses Association, Sigma Theta Tau International, Society of Critical Care Medicine, and Society of Thoracic Surgeons
Disclosure: Nothing to disclose.

Medical Editor

Daniel S Schwartz, MD, FACS, Assistant Clinical Professor of Cardiothoracic Surgery, Mount Sinai School of Medicine; Chief of Thoracic Surgery, Huntington Hospital
Daniel S Schwartz, MD, FACS is a member of the following medical societies: American Association for the Advancement of Science, American College of Cardiology, American College of Chest Physicians, American College of Surgeons, American Diabetes Association, American Heart Association, American Medical Association, Association for Academic Surgery, and Society of Thoracic Surgeons
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

John Myers, MD, Director, Pediatric and Congenital Cardiovascular Surgery, Departments of Surgery and Pediatrics, Professor, Penn State Children's Hospital, Milton S Hershey Medical Center
John Myers, MD is a member of the following medical societies: American Association for Thoracic Surgery, American College of Cardiology, American College of Surgeons, American Heart Association, American Medical Association, Congenital Heart Surgeons Society, Pennsylvania Medical Society, and Society of Thoracic Surgeons
Disclosure: Nothing to disclose.

CME Editor

Daniel Rauch, MD, FAAP, Director, Pediatric Hospitalist Program, Associate Professor, Department of Pediatrics, New York University School of Medicine
Daniel Rauch, MD, FAAP is a member of the following medical societies: Ambulatory Pediatric Association, American Academy of Pediatrics, and Society of Hospital Medicine
Disclosure: Baxter Honoraria Consulting; Pfizer Honoraria Consulting

Chief Editor

John Kupferschmid, MD, Director of Congenital Heart Surgery, Department of Surgery, Methodist Children's Hospital at San Antonio
John Kupferschmid, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Surgeons, Society of Thoracic Surgeons, and Society of Thoracic Surgeons
Disclosure: Nothing to disclose.

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