Sinus Venosus Atrial Septal Defects 

Updated: Dec 15, 2020
Author: Gary M Satou, MD, FASE; Chief Editor: Howard S Weber, MD, FSCAI 

Overview

Background

In simple terms, an atrial septal defect (ASD) is a deficiency of the atrial septum. Atrial septal defects account for about 10-15% of all congenital cardiac anomalies and are the most common congenital cardiac lesion presenting in children and adults.[1] Sinus venosus atrial septal defects account for only 10% of atrial septal defects. The remaining atrial septal defects are ostium secundum type (70%), ostium primum type (20%), and unroofed coronary sinus, or coronary sinus septal defects, (< 1%). Most children with sinus venosus atrial septal defects are asymptomatic but may develop symptoms as they age.

Excellent surgical results with a mortality rate near 0% can be expected. This is particularly true in patients who undergo repair when younger than 15 years. An atrial septal defect was the first lesion repaired using cardiopulmonary bypass in 1954 by John Gibbon, MD, at the Mayo Clinic.

Pathophysiology

The more common sinus venosus type defect (often referred to as the "usual type") occurs in the upper atrial septum and is contiguous with the superior vena cava (SVC). The lesion is rostral and posterior to the fossa ovalis (where secundum type defects occur) and is separate from it. It is almost always associated with anomalous pulmonary venous drainage of the right upper pulmonary vein into the SVC. See the image below.

Panel A. Transesophageal echocardiogram (transvers Panel A. Transesophageal echocardiogram (transverse view) of a patient with a sinus venosus defect of the superior vena cava (SVC) type. The original defect (white star burst) has been repaired by placing a baffle (arrows), which directs blood from the anomalously connected right upper pulmonary vein into the left atrium (LA). In this patient, the baffle was redundant so at a more rostral level (Panel B), it could be seen (black open arrows) to bulge into the superior vena cava (SVC)–right atrial (RA) junction (trio of white arrows). The remainder of the atrial septum is denoted by the duo of white open arrows. Panel C is a transesophageal echocardiogram, sagittal view. Doppler color flow mapping verifies that the protruding baffle (white closed arrows) results in a narrowing of the pathway from the SVC to the RA. The quartet of white open arrows points to the remainder of the atrial septum.

Less commonly, the defect may occur at the junction of the right atrium and inferior vena cava (IVC) and be associated with anomalous connection of the right lower pulmonary vein to the IVC. Rarely, sinus venosus defects occur posterior to the fossa ovalis without bordering the SVC or IVC. The predominant hemodynamic consequence is a left-to-right shunt through the defect. See the image below.

Panel A is a transesophageal echocardiogram, trans Panel A is a transesophageal echocardiogram, transverse view. The white star burst shows the sinus venosus defect of the inferior vena cava (IVC) type, lying adjacent to the IVC junction with the right atrium (RA). The remainder of the atrial septum is just out of the view of this sector but is represented by the white open arrowheads. The leaflets of the closed tricuspid valve (TV) are visible. RV = right ventricle. Panel B is a transesophageal echocardiogram, sagittal view. This is the same patient as in Panel A. This view proves that the rostral portion of the atrial septum (which would be missing in a patient with a sinus venosus defect of the SVC type) is intact. ct = crista terminalis; svc = superior vena cava.

Etiology

During normal embryonic development, the right horn of the sinus venosus encompasses the right superior vena cava (SVC) and inferior vena cava (IVC). If abnormal resorption of the sinus venosus occurs, an atrial septal defect results near the orifice of either the SVC or IVC.

Atrial septal defects occur as associated anomalies in many major complex congenital lesions but sinus venosus atrial septal defects occur more often as an isolated abnormality.

Other abnormalities may exacerbate an atrial septal defect. For example, systemic hypertension in an adult with a sinus venosus atrial septal defect may result in left ventricular hypertrophy and reduce left ventricular compliance, which, in turn, exacerbates the atrial level left-to-right shunt. Mitral stenosis, which is either congenital or acquired, may also exacerbate the atrial level left-to-right shunt.

Epidemiology

United States data

Sinus venosus atrial septal defects represent approximately 1% of congenital cardiac lesions.

Race-, sex-, and age-related demographics

No racial predilection is known; however, atrial septal defects affect females more often than males. The female-to-male ratio is 2:1. No difference in outcome is associated with sex.

Sinus venosus atrial septal defects are congenital lesions present at birth. The age at presentation depends on the size of the left-to-right shunt (atrial and partial anomalous pulmonary venous return). Atrial septal defects in infancy are usually asymptomatic. They are usually detected by echocardiography while undergoing a cardiac evaluation.

Prognosis

The prognosis is excellent for young patients who undergo repair of uncomplicated defects. Repair delayed until the third decade of life is associated with a decrease in life expectancy.[2]

Morbidity/mortality

Surgical repair in the first 2 decades of life is associated with a mortality rate near zero. Life expectancy approaches that of the general population if the defect is repaired during this time. Right heart dilation rapidly regresses after surgery, and the functional result is excellent. In cases of repair during adulthood, life expectancy may be decreased despite successful repair. Surgical morbidity rates are related to early postoperative pericardial effusion, early postoperative pulmonary venous or systemic venous obstruction, and supraventricular arrhythmias. If the baffle directing pulmonary venous blood to the left atrium is not placed correctly, it may obstruct pulmonary venous drainage. If the baffle bulges into the superior vena cava (SVC), it may obstruct SVC inflow, necessitating the placement of an augmentation patch on the anterior surface of the SVC and right atrial junction.

Untreated atrial septal defects are associated with a significantly shortened life expectancy. After age 20 years, the mortality rate is approximately 5% per decade with 90% of patients dead by age 60 years. These patients present with an increase in left-to-right shunting and occasionally with congestive heart failure with pulmonary hypertension in the fourth to sixth decades of life. Guidelines for the diagnosis and treatment of pulmonary artery hypertension have been established.[3]  Late problems in untreated patients also include the risk of paradoxical embolus as well as atrial fibrillation, pulmonary hypertension, and right heart failure.

Complications

Complications include the following:

  • Sinus node dysfunction

  • Pulmonary venous obstruction

  • Atrial fibrillation, atrial flutter, or supraventricular tachycardia (SVT)

  • Pulmonary hypertension

  • Atrial baffle leak

  • Pericardial effusion or postpericardiotomy syndrome

  • SVC syndrome

Patient Education

Patient education mainly focuses on preoperative and postoperative care and recovery, which are especially important in young children undergoing surgery. Centers with experienced child life personnel are invaluable in preparing children for open-heart surgery.

 

Presentation

History

Sinus venosus atrial septal defects (ASDs), like most ASDs, are diagnosed upon detection of a murmur, a fixed split second heart sound, and/or right heart enlargement on chest x-ray or electrocardiogram (ECG) in the usually asymptomatic patient. Note the following:

  • Symptoms of ASDs are typically a function of the size of the associated shunt.

  • As many as 60% of apparently asymptomatic patients may have easy fatigability and dyspnea. Such symptoms usually indicate a relatively large shunt.

  • Adults may not come to medical attention until symptoms occur. Arrhythmias, dyspnea, and a decrease in exercise tolerance are common symptoms.

Physical

A cardiac murmur secondary to increased pulmonary artery blood flow is heard over the upper left sternal border. The murmur is usually a soft grade 2/6 systolic ejection murmur. A prominent right ventricular impulse may also be noted along the left sternal border. A diastolic flow murmur may be present at the left lower sternal border and the tricuspid area and is indicative of a large left-to-right shunt.

The second heart sound is widely split and may be fixed or may vary little with respiration. The pulmonic component of the second heart sound is usually normal in intensity but may increase in intensity if pulmonary hypertension is present.

Patients with atrial septal defects may present with the "gracile habitus." These patients are thin for their height.

 

DDx

 

Workup

Imaging Studies

General laboratory studies are rarely helpful in sinus venosus atrial septal defect (ASD). However, imaging studies help in the evaluation and diagnosis of suspected sinus venosus ASD.

Chest radiography

Findings on chest radiography may include the following:

  • Prominent right atrium
  • Prominent main pulmonary artery
  • Increased heart size and pulmonary vascularity

Echocardiography

Echocardiography (ECHO) reveals ASD and most of the pulmonary vein connections in most patients and is the diagnostic modality of choice.[4]

Two-dimensional ECHO with color flow Doppler reveals the position and size of the defect and the presence of anomalous pulmonary venous drainage (in many of these cases). It also helps identify associated anomalies and reveals the left-to-right (or right-to-left) direction of flow and the degree of right ventricular overload.

In a retrospective study, Snarr et al found that the absence of the posterior rim ("bald" posterior wall) is a consistent finding in patients with an inferior sinus venosus defect (SVD) and that it distinguishes an inferior SVD from a large secundum ASD with inferior extension. In transthoracic echocardiograms, the posterior rim was absent in all 15 patients with a surgical diagnosis of inferior SVD, but it was present in all 14 patients with a secundum ASD. For all observers, the diagnostic accuracy of inferior SVDs showed a statistically significant increase with the use of the rim criterion (P< 0.0001).[5]

In children with difficult transthoracic windows, or in older or larger patients, transesophageal echocardiography may be helpful in imaging the defect and pulmonary vein connections.[6] In the current era, cardiac magnetic resonance angiography (MRA)/magnetic resonance imaging (MRI) may be alternatively used to complete the diagnostic information needed prior to surgery.

Cardiac MRI/MRA

Features that may be seen with MRI/MRA include the following:

  • Atrial septal defect size and location are shown.

  • Excellent delineation of individual pulmonary vein connections can be identified.

  • Right ventricle enlargement and indexing to body surface area (BSA) is available if helpful.

  • Flow-quantification may also be performed.

Electrocardiography

Note the following:

  • Right ventricular hypertrophy predominates, with a lengthened PR interval and incomplete right bundle branch block secondary to right ventricular dilation (small rSR').

  • Peaked P waves in lead II may demonstrate right atrial enlargement.

  • Abnormal P-wave axis (negative in lead AVF) would indicate a displaced sinus node inferiorly (non sinus atrial rhythm).

Procedures

Cardiac catheterization

Cardiac catheterization is usually not required in the preoperative assessment of patients with sinus venosus atrial septal defect, but it may be considered in the following circumstances:

  • In any child in whom associated lesions are suspected or in whom pulmonary hypertension is suspected, catheterization is performed to measure pulmonary artery pressure and, if pulmonary resistance is elevated, the response to pulmonary vasodilators.

  • Adults who have the potential for associated coronary atherosclerotic lesions should undergo catheterization to exclude these abnormalities before surgical repair of the sinus venosus atrial septal defect.

Histologic Findings

Patients with pulmonary hypertension and advanced pulmonary vascular obstructive disease may exhibit histologic changes similar to those seen in pulmonary vascular disease. Specifically, these include intimal and medial hypertrophy and, in more advanced lesions, luminal occlusion.

 

Treatment

Medical Care

Medical care of sinus venosus atrial septal defect (ASD) is primarily supportive and is not required for asymptomatic patients.

Patients presenting in heart failure should be stabilized in anticipation of elective repair. Consult with a pediatric cardiologist and a pediatric cardiac surgeon.

Patients with a sinus venosus ASD should be transferred to a center experienced in the repair of such a defect in children or adults. Patients with sinus venosus ASD in heart failure may require short-term continued support until pulmonary edema resolves, myocardial function improves, and until pulmonary vascular resistance, if elevated, normalizes.

Patients with sinus venosus ASD require a brief postoperative admission to a pediatric cardiac intensive care unit. The patient who undergoes uncomplicated surgical repair is usually discharged home within several days.

There are no dietary restrictions, and physical activity should not be limited in patients who undergo early and complete correction.

Pharmacotherapy

No long-term medication is required after repair of an uncomplicated atrial septal defect. Some surgeons prescribe aspirin or other anticoagulation regimens for several weeks in patients in whom a prosthetic patch was used to close the defect. This allows for endothelial ingrowth over the thrombogenic surface of the patch. Long-term anticoagulation is not indicated.

Antibiotic prophylaxis is not required in patients 6 months following repair of atrial septal defects.

Surgical Care

Surgical correction is the mainstay of therapy.

Repair of the sinus venosus atrial septal defect is more complex than repair of the average secundum atrial septal defect. A patch (synthetic material or pericardium) is used to redirect blood flow from the right superior pulmonary vein into the left atrium. This effectively closes the interatrial communication while also correcting the anomalous pulmonary venous drainage. Sometimes, to avoid creating superior vena cava (SVC) obstruction, a patch is placed on the anterior surface of the SVC. Care is taken to avoid injuring the nearby sinus node. Ligation of the azygous vein may also be required to eliminate its drainage into the left atrium and to prevent the resulting residual right-to-left shunt.[7]

When the location of the anomalous venous drainage is in the high SVC and is far from the atrial-caval junction, a different surgical approach can be used to decrease the probability of caval stenosis or pulmonary vein stenosis. As described by Warden et al, the repair consists of division of the SVC just above the take off of the anomalous pulmonary vein.[8] The distal caval end is oversewn or patched to assure no pulmonary vein compromise. Next, the well-mobilized cava is anastomosed to the right atrial appendage after amputation of the most distal end. The atrial septal defect is then closed by sewing a patch to cover the atrial septal defect and divided SVC orifice, thereby baffling the anomalous vein to the left atrium. This method is very effective in patients with more complicated pulmonary venous anomalies.

A very small right upper pulmonary vein that drains into the high SVC could be left intact and not incorporated into the surgical repair if it is deemed high risk for late pulmonary vein obstruction.

SVC stenosis or obstruction after the Warden procedure has been reported.[9, 10, 11] Modifications to the Warden technique based on anatomic characteristics have demonstrated improved outcomes.[12, 13, 14]

Ling et al report excellent outcomes with their modified Warden cavoatrial anastomosis technique for the treatment of anomalous pulmonary veins. In a study conducted from 2007 to 2015 in 26 patients with anomalous pulmonary veins (mean age: 22 years; range, 4-70 years), 24 patients had a sinus venosus ASD. Following the modified Warden procedure, all patients had unobstructed caval and pulmonary venous flow, and no patients had long-term arrhythmias or died.[12]

Asymptomatic children generally undergo repair when aged 3-5 years.

Sinus venosus defects do not close spontaneously. Adults with left-to-right shunts greater than 1.5 benefit from surgical closure.

Patients with significant pulmonary hypertension and elevated pulmonary vascular resistance unresponsive to pulmonary vasodilator therapy (eg, oxygen, nitric oxide, calcium channel blockers,) may not be good candidates for surgical repair. Such patients may develop acute right ventricular failure if their heart no longer has the ability to shunt right to left at the atrial communication in response to increases in pulmonary vascular resistance.

Repair is performed most often through a standard median sternotomy. More cosmetic incisions may also be used, such as partial sternotomies, small right anterior thoracotomies, and inframammary incisions. All approaches still require the use of cardiopulmonary bypass for closure of the atrial septal defect.

Although transcatheter occlusion devices are currently used for closing secundum atrial septal defects, such devices are not indicated (at present) for the closure of sinus venosus atrial septal defects because of the position of the defect and because of the lack of surrounding tissue adequate to seat such an occlusion device. In addition, such a device may obstruct SVC flow and does not achieve redirection of the anomalous right pulmonary venous flow to the left atrium.

Long-Term Monitoring

Postoperative follow-up

Postoperative follow-up usually involves an office visit with the pediatric cardiologist (and possibly the cardiac surgeon) 1-3 weeks after hospital discharge.

Echocardiography is used to effectively evaluate the repair for evidence of residual shunting, superior vena cava (SVC) or pulmonary vein obstruction, pericardial effusion, and ventricular function.

The potential for late postoperative narrowing of the SVC and possible superior vena cava syndrome is observed after repair of sinus venosus atrial septal defects.

Sinus node dysfunction screening should be part of outpatient follow-up care, because sinus node dysfunction may become apparent years after repair of a sinus venosus atrial septal defect.

 

Medication

Medication Summary

Medical management is ineffective in the treatment of sinus venosus defects. The rare patient who presents in congestive heart failure can be stabilized medically with diuretics and inotropic support.

Inotropic agents

Class Summary

These agents provide myocardial support in patients with dysfunction secondary to pulmonary overcirculation from left-to-right shunting. Positive inotropic agents increase the force of contraction of the myocardium and are used to treat acute and chronic congestive heart failure (CHF). Some may also increase or decrease the heart rate (ie, positive or negative chronotropic agents), provide vasodilatation, or improve myocardial relaxation. These additional properties influence the choice of drug for specific circumstances.

Digoxin (Lanoxin)

Exerts its inotropic effects by increasing amount of intracellular calcium available during excitation-contraction coupling. One of numerous inotropic agents that can be used in infants with congenital cardiac defects. Generally used for long-term administration and is rarely drug of choice for acute management of heart failure in ICU setting.

Dopamine (Intropin)

Adrenergic agonists often are used for inotropic support in critical care setting for their rapid onset of action and rapid time to peak effect, which make them easier to titrate to effect

Loop diuretics

Class Summary

These agents are used for management of right heart failure and pulmonary edema. They promote excretion of water and electrolytes by the kidneys.

Furosemide (Lasix)

Highly effective first-line diuretic in newborns and infants. A sulfonamide derivative, it exerts its effects on the loop of Henle and distal renal tubule, inhibiting reabsorption of sodium and chloride.