, Christoph Jaschinski 1, Mina Farag 1, Elizabeth Fonseca-Escalante 1, Matthias Gorenflo 2, Matthias Karck 3, Tsvetomir Loukanov 11 Division of Congenital Cardiac Surgery, Department of Cardiac Surgery, University Hospital Heidelberg, 69120 Heidelberg, Germany
2 Department of Pediatric Cardiology and Congenital Heart Disease, University Hospital Heidelberg, 69120 Heidelberg, Germany
3 Department of Cardiac Surgery, University Hospital Heidelberg, 69120 Heidelberg, Germany
Abstract
Atrial septal defects (ASDs) are among the most prevalent congenital cardiac malformations. Closure of the defect and repair of associated cardiac malformations are typically indicated if an ASD is hemodynamically significant or symptomatic. This narrative review aims to summarize key aspects of surgical ASD closures. A non-systematic literature review was conducted to cover surgically relevant aspects of (developmental) anatomy, morphology, and treatment. ASDs result from diverse developmental alterations, leading to subtype-specific associated cardiac malformations, meaning surgical therapy varies accordingly. Presently, surgical repair yields excellent outcomes for all ASD subtypes, with minimally invasive approaches, especially in adults, increasingly employed for ASD closure. Surgical ASD repair is safe with excellent results. However, familiarity with ASD subtypes and typically associated lesions is crucial for optimal patient management.
Keywords
- atrial septal defect
- surgery
- congenital heart disease
- operative technique
Atrial septal defects (ASDs), defined as communications between the two atria of the heart, can occur alone or in conjunction with other congenital malformations. ASDs rank as the second-most common congenital cardiac malformation, occurring in 1.65/1000 live births and constituting 10 to 15% of all congenital cardiac malformations [1]. ASDs encompass various lesions with different embryological origins [2]. Meanwhile, these differences impact the decision-making regarding treatment indications and modalities and are reviewed in the following section. Pathophysiologically, ASDs in an otherwise normal four-chambered heart can lead to a shunt on the atrial level between the left atrium that receives the pulmonary venous return and the right atrium that receives the systemic venous return. The shunt volume is determined by the morphology and size of the ASD, by the pressure difference between the left and right atria resulting from right ventricular compliance and pulmonary vascular resistance (PVR). The shunt is usually directed from the left to the right atrium, resulting in a volume load of the right heart (left-to-right shunt). Contrarily to ventricular septal defects, ASDs do not impose pressure load on the right ventricle [3]. The shunt volume is usually described as the ratio of pulmonary blood flow (Qp) and systemic blood flow (Qs), with a Qp/Qsof more than 1.5 considered hemodynamically relevant in children and adults with ASD [4, 5, 6]. Symptoms are variable and usually less pronounced compared with other shunt lesions. Consecutively, ASDs are detected at a wide variety of ages, with symptoms typically resulting from pulmonary overcirculation and right heart failure (intolerance to exercise, failure to thrive) or (particularly in adults) from thromboembolic events caused by paradoxical embolism [7]. The natural history of untreated ASD, known from historical data, is associated with right heart failure and an increased annualized mortality risk beginning from young adulthood, resulting in a markedly reduced median life expectancy. However, given the variable clinical courses, some patients remain symptom-free until advanced adulthood [8, 9]. A landmark paper by Murphy et al. [10] showed that the life expectancy of ASD patients remains normal if surgical treatment is undertaken before the age of 25. Contrarily, if treated at an older age, patients exhibit increased mortality rates compared to the average population [10]. Therefore, surgical closure of ASDs has become universally accepted as the treatment of choice for patients with hemodynamically relevant ASD or symptoms related to ASD. Additionally, interventional closure techniques using closure devices have exceptionally evolved, offering now valid therapeutical strategies for certain ASD subtypes [11, 12, 13]. This review aims to focus on the surgical treatment of ASD, summarizing the current state of surgical techniques for different ASD subtypes and the choice of the surgical approach. Furthermore, the results, complications, and impact on the prognosis of surgical ASD treatment are discussed.
A narrative, non-systematic review was conducted, defining subjects to be covered in advance. Literature searches were performed in PubMed using appropriate search and MeSH (Medical Subject Headings) terms. Additionally, potentially relevant literature not listed in PubMed was extracted from Google Scholar. The search was conducted without time limits, and the following search terms were used in various combinations: ‘atrial septal defect’, ‘ASD’, ‘surgical treatment’, ‘embryology’, ‘anatomy’, and ‘morphology’. Original works, case reports, case series, and reviews were considered eligible literature sources for this review.
A comprehensive understanding of the term ‘ASD’ goes beyond the notion of a simple hole in the interatrial septum. A deeper understanding of the anatomy of the interatrial septum, the resulting subtypes of ASD, and particularly the typically associated subtype-specific malformations, is crucial for developing tailored surgical treatment strategies and ensuring patient safety.
The relevant processes of the formation of the atria and the interatrial septum occur between the fourth and sixth weeks of gestation. After simplifying these complex processes for this review, three significant aspects emerged:
Firstly, a common atrium forms from the inlet portion of the heart tube around the fourth week of gestation. This atrium receives blood from two venous channels, which develop into the two horns of the sinus venosus. Eventually, this sinus venosus then septates into the coronary sinus and the two venae cavae. An additional venous channel will connect posteriorly to the sinus venosus, forming the pulmonary veins. These veins then migrate left alongside the posterior wall of the sinus venosus. Disruptions in the septation of the evolving coronary sinus from the atrium will result in a communication between the coronary sinus and the left atrium, namely a coronary sinus ASD. These rare defects account for less than 1% of all ASDs [14].
Anomalies in the leftward migration of the pulmonary veins will result in an abnormally right-sided and anterior position of the right pulmonary veins. This anterior position can lead to a loss of septation between the coronary sinus and, in most cases, the upper cavoatrial junctions. This leads to superior sinus venosus ASD, which represents 4 to 11% of all ASDs, whereas inferior sinus venosus ASD is much rarer, accounting for less than 1% of all ASDs [15].
Secondly, the common atrium undergoes septation into the left and right atria. A septum primum grows from the atrial roof towards the endocardial cushions, forming the atrioventricular (AV) junction. The space between the growing septum primum and the AV junction is the ostium primum, which is gradually obliterated as the septum primum grows. To facilitate blood flow into the left heart, the septum primum perforates subsequently in its cranial aspect, forming the ostium secundum. Concurrently, an inward fold in the atrial roof to the right of the septum primum develops. This fold (septum secundum) overlaps with the ostium secundum, creating a flap valve and enabling right-to-left-shunting. The caudal end of the septum secundum forms the limbus of the fossa ovalis. The region caudal to the limbus is called the fossa ovalis. Postnatally, as the pressure in the left atrium exceeds the right atrial pressure, the septum primum is pressed against the septum secundum, and the flap valve closes. Subsequently, the tissue of the septum primum and the septum secundum merge. If the septum secundum insufficiently overlaps the ostium secundum, a tissue defect in the septum primum at the fossa ovalis, the secundum ASD, will remain. Secundum ASDs are the most common ASD subtype and constitute about 75% of all ASDs [16]. If there is no tissue deficiency but a lack of flap valve–tissue merging, a patent foramen ovale (PFO) consequently forms; PFOs exist in about 25 to 30% of the general population [17].
Thirdly, the AV canal undergoes septation into left- and right-sided AV valves through ingrowth and fusion of a superior and an inferior endocardial cushion. Additionally, two lateral endocardial cushions grow towards the center of the AV canal, contributing to the AV valve formation [18]. The septum primum joins the crest formed by the fused inferior and superior endocardial cushions, leading to the closure of the atrial septum at this site. If this fusion is incomplete, i.e., the foramen primum remains patent, a primum ASD is formed [19], which accounts for about 10% of all ASDs [20].
Closure of an ASD may be warranted for several reasons: hemodynamic relevance of
the shunt (Qp/Qs
In recent years, interventional treatment options have grown safer and more effective, meaning that for a subset of ASDs (namely PFOs and secumdum ASDs), interventional closure has become an accepted alternative to surgical treatment for eligible patients [23]. Transcatheter closure of sinus venosus ASDs using covered stents has been reported to be feasible; however, it is still associated with high rates of major complications, such as stent embolization and caval vein occlusion [24].
In children, ASD closure is typically scheduled electively. Spontaneous closure of the ASD, mostly seen in small secundum defects or PFOs, is unlikely beyond three years [25]. Therefore, surgical ASD closure in asymptomatic children is often performed conveniently between the ages of three and school age. However, intolerance to exercise or large shunt volumes with severe right heart enlargement might warrant earlier closure. Infants presenting with severe heart failure symptoms alongside an isolated ASD should prompt suspicion of additional underlying conditions. In adults, unnecessarily delaying ASD closure should be avoided, as this might decrease the likelihood of normalizing right heart function, increase the risk of arrhythmias, and also potentially reduce life expectancy [10, 26, 27].
For all ASD subtypes, a thorough echocardiographic evaluation should be conducted both preoperatively and intraoperatively to rule out the presence of more than one lesion in the atrial septum (such as an additional sinus venosus ASD in a patient scheduled for PFO closure) [28]. Surgical ASD closure necessitates the use of cardiopulmonary bypass with bicaval canulation to obtain a bloodless operative field. During intracardiac correction, primarily performed via a right atriotomy, it is crucial to avoid air embolism into the ascending aorta. While some surgeons consider induced ventricular fibrillation adequate for the relatively brief period of intracardiac surgery, we advocate for the safer approach of aortic clamping and cardioplegia application. Upon opening the right atrium, meticulous anatomical inspection is imperative to exclude concomitant ASDs and anomalously returning pulmonary veins. Furthermore, it is essential to accurately locate the coronary sinus, the triangle of Koch, and the openings of the superior and inferior venae cavae. Following correction, residual shunts should be excluded using echocardiography with or without the Valsalva maneuver and bubble testing [29].
Surgical closure of a PFO as an isolated lesion has become exceedingly rare due to the advancements in interventional PFO closure [30]. Larger secundum ASDs are frequently not suitable for percutaneous closure and are thus referred for surgical correction. Intraoperatively, the initial inspection should determine the size of the defect. The border zone between the limbus of the fossa ovalis and the septum primum should be carefully inspected for additional fenestrations. If multiple fenestrations are identified, resectioning the septum primum tissue may be reasonable. Moreover, the inferior border of the ASD should be well-defined. A decision must be made regarding whether to close the ASD with or without patch material. Notably, a PFO can frequently be closed with direct continuous or interrupted sutures, obviating the need for patch material [31]. However, for larger secundum ASDs, utilizing patch material (e.g., autologous pericardium fixed in formaldehyde or xenogeneic patch material) offers a safe means of preventing tears and residual defects [32]. The patch is typically secured to the ASD borders using continuous non-resorbable sutures. Our group previously described the operative technique in a video tutorial [33].
Contemporary studies on surgical closure of secundum ASD report low perioperative mortality rates of 0 to 0.3% [34, 35]. However, preoperative severe tricuspid regurgitation and severe right heart dysfunction appear to diminish long-term survival. Postoperatively, pericardial effusions develop in about 10 to 15% of patients within up to two months after surgery, underscoring the need for regular echocardiographic monitoring [36].
Primum ASD represents an endocardial cushion defect and, therefore, is often accompanied by additional lesions. A cleft in the left AV valve between the inferior and superior bridging leaflet is present in 100% of cases. Additional left-sided malformations, such as single papillary muscle or left-ventricular outflow tract (LVOT) obstruction, are present in approximately 10% of cases [37]. The AV valves can be separated (with two distinct valve annuli) or configured as a common valve. In the latter scenario, the AV node is displaced posteriorly and lies between the coronary sinus and the inferior border of the AV valve—surgical correction aims to close the defect and repair the left AV valve. Closure of the ASD with a patch follows a similar approach to that described for secundum ASD. However, one has to consider that the sutures of the caudal border of the ASD are placed directly at the AV valve plane. Depending on the presence of a small rim in this region and the tissue quality, the patch can be affixed using continuous sutures with superficial stitches or interrupted sutures placed from the right ventricular side through the AV valve plane and the patch [20, 37, 38]. Different techniques exist in the AV node region to prevent AV block [39]. While some surgeons avoid this region entirely by suturing the patch around the coronary sinus and allowing the coronary sinus to drain to the left-atrial side, we believe the risk of AV block can be sufficiently mitigated by placing stitches superficially in this region and staying close to the AV valve annulus.
While perioperative mortality rates after primum ASD repair are low, a notable risk for re-operations primarily arises from left AV valve dysfunction. Indeed, re-operations between 5 and 15% have previously been reported [40, 41, 42]. Another cause to re-do surgery in these patients is the development of LVOT obstruction due to the anatomically frequently narrow and long LVOT, with additional fibrous obstruction developing over time [43, 44, 45].
The upper sinus venosus defect is usually located near the upper cavo-atrial junction. The right upper pulmonary veins may either drain into the region of the ASD in the left atrium (functional partial anomalous pulmonary vein return (PAPVR)) or drain directly into the right atrium or the superior vena cava (anatomical PAPVR). Preoperative diagnostics should identify the presence of PAPVR and the anatomical locations of anomalously returning pulmonary veins. Surgical correction aims to close the ASD and redirect pulmonary venous return to the left atrium. Therefore, the patch used for ASD closure is implanted to retain the pulmonary veins on the left atrial side of the patch. The higher the pulmonary veins return to the superior vena cava (SVC), the longer this tunnel must be. A common problem with tunneling PAPVR to the SVC is obstruction of either the pulmonary venous tunnel or the SVC. To prevent SVC stenosis, a second patch can be used to augment the cavoatrial junction and the SVC (two-patch technique) [46, 47]. However, this technique, which involves an incision in the cavoatrial junction, has been associated with higher rates of postoperative sinus node dysfunction than the single-patch technique [48, 49, 50]. The Warden procedure is a technique to correct particularly remote PAPVR into the SVC [51]. This technique divides the SVC cranially into the uppermost pulmonary vein and closes the stump. The ASD patch is sutured so the anomalous pulmonary vein completely drains to the left atrium, and the cranial stump of the SVC is anastomosed to the right atrial appendage. While this technique avoids incisions in the cavoatrial junction, it might be associated with higher rates of SVC obstructions, particularly in the region of the cavoatrial anastomosis. A wide and tension-free anastomosis should be fashioned to prevent this after carefully removing all trabeculations inside the right atrial appendage [52, 53, 54, 55]. In adults, modifications of the Warden technique using interposition grafts between the SVC and the right atrium have been described [56, 57, 58].
Lower sinus venosus defects are rare, often near the inferior cavoatrial junction. The right lower pulmonary veins can frequently connect to the right atrium or even the inferior vena cava (IVC) in this area. Surgical correction follows the same principles described for the upper sinus venosus defects, aiming to close the ASD while re-routing the pulmonary venous return to the left atrium. To facilitate the exposure of the ASD and the pulmonary veins, the IVC should be cannulated as far caudally as possible. In larger patients, a femoral venous cannula may enhance exposure.
The perioperative mortality is similarly low to that described for other ASD subtypes. The main long-term issues result from sinus node dysfunction and stenoses of the SVC and pulmonary venous baffles. The Warden procedure has been described as reducing sinus node dysfunction compared with the two-patch technique [48, 59]. Meanwhile, SVC obstruction after the Warden procedure has been described to occur in 2 to 5% of patients [60, 61].
In this exceedingly rare ASD subtype, there is a tissue deficiency between the coronary sinus and the left atrium. It is also referred to as ‘unroofed coronary sinus’. The extent of this deficiency can vary from one or more small defects to a complete absence of a roof over the coronary sinus. The lesion is frequently associated with a persisting left-sided superior vena cava (LSVC), which typically drains into the unroofed coronary sinus or, if the deficiency extends over the entire coronary sinus, into the left atrial roof. Various surgical approaches exist to correct this lesion, aiming to eliminate the interatrial communication and re-route the LSVC to the right atrium [62]. In this regard, a roof of the coronary sinus, which also tunnels the LSVC via the coronary sinus to the right atrium, is constructed [63]. If this approach is used, care must be taken to avoid compromising the pulmonary venous return or the mitral valve inflow. If a neo-roof of the coronary sinus cannot be constructed with reasonable risk, the opening of the coronary sinus to the right atrium can be closed with a patch, while the LSVC is transected and anastomosed to the right atrial appendage, either directly or with an interposition graft. This leaves the coronary sinus draining into the left atrium, which usually does not cause detectable desaturation.
Long-term data on outcomes for this rare ASD subtype are limited. However, current case reports and small series suggest favorable long-term results following surgical repair [64, 65].
In certain cases, surgical ASD closure may be necessary following previous percutaneous device closure. Indications for this approach include device endocarditis, device malposition, incomplete device closure, and the presence of an additional, frequent superior sinus venosus defect, which has not been detected before the device closure of the concomitant PFO [66]. If device endocarditis is present, the device should be completely explanted during surgery, and the resulting defect should preferably be closed with an autologous patch [67, 68]. In the other previously mentioned scenarios, the grade of device ingrowth and the associated risks of device explanation determine whether the device is left in place while closing the additional shunt.
A more far-reaching indication for surgery arises from the perforation of a closure device, which can affect the aortic root or the atrial roof [69]. The resulting hemopericardium frequently leads to rapid circulatory deterioration. If the patients reach the hospital, emergent sternotomy and connection to the heart–lung machine are undertaken to stabilize the patient. Following induction of cardioplegic arrest, the situation can be assessed. The surgical correction should include explantation of the device and perforation repair. This can be achieved by reconstructing the atrial roof and the interatrial septum with patches or, in the case of aortic root perforation, by an aortic root replacement [70, 71].
While conventional access for surgical ASD closure has been a standard median sternotomy, different alternative access routes have recently been suggested that aim at being minimally invasive and reducing surgical trauma.
These alternative approaches include lower hemi-sternotomy, right lateral thoracotomy, and, particularly for larger patients, totally endoscopic approaches via right lateral mini-thoracotomy. For right lateral thoracotomy, both horizontal (parallel to the ribs) and vertical (craniocaudal) skin incisions have been described. The vertical skin incisions appear to provide a better exposure of the situs than the horizontal approach [72, 73, 74, 75, 76]. Generally, in minimally invasive approaches, the surgeon must decide whether central cannulation or peripheral cannulation is preferred. Peripheral cannulation offers greater access to the surgical field. However, the risk of ischemic complications after femoral cannulation needs to be considered, especially for smaller patients and longer cardiopulmonary bypass durations.
For adults, the totally endoscopic approach presents an elegant solution. Cardiopulmonary bypass is established via the groin vessels. An additional venous cannula in the SVC inserted via the internal jugular vein offers, from our experience, a comfortable way to conduct total bypass without interfering with the operative situs. Results of totally endoscopic ASD closure, primarily in secundum ASDs, show that the cardiopulmonary bypass and cardioplegic arrest times are longer than with the median sternotomy approach. However, the total duration of surgery does not appear substantially longer, and recovery times may even be shorter than after conventional ASD closure [77, 78, 79, 80].
From our perspective, each program should define its preferred pathway to achieve the best possible surgical results, prioritizing maximal patient safety. If minimally invasive approaches do not compromise these aspects, they should be considered equivalent or even superior (owing to cosmetic advantages, the avoidance of sternotomy, and possibly accelerated recovery) to the standard approach via a median sternotomy. To enhance process safety, minimizing inter-surgeon variability within a program is crucial.
This non-systematic review narrative aims to provide an overview of the relevant points surgeons should be familiar with when treating patients with different ASD subtypes. As demonstrated, ASDs encompass a wide spectrum of defect morphologies and subtypes. While the majority of ASDs consist of secundum ASDs and PFOs, other subtypes pose specific morphological particularities and associated malformations. Thus, surgeons must know these nuances to address these challenges effectively. Additionally, this underscores the importance of precise preoperative diagnostics and multidisciplinary planning of the appropriate approach within a dedicated heart team with expertise in treating congenital heart defects.
Surgical treatment of ASD is safe and effective, with low rates of severe complications and good predictability and reproducibility of results. It is key for the treating surgeon to be familiar with the different anatomical atrial septal defect subtypes and the typically associated lesions to treat the patient with maximized safety. The surgical treatment of ASD generally allows for normalization of cardiac function and life expectancy.
PG, CJ, MF, EFE, MG, MK and TL designed the concept of the manuscript, PG wrote the manuscript, CJ and TL helped to write the manuscript. All authors reviewed and contributed to editorial changes in the manuscript. All authors read and approved the final manuscript. All authors have participated sufficiently in the work and agreed to be accountable for all aspects of the work.
Not applicable.
Thanks to Barbara Fritz-Rodszies for her support in editorial work.
This research received no external funding.
The authors declare no conflict of interest.
References
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