Atrial Septostomy and Atrial Septal Stenting: Role of Echocardiography

Jayashree Mishra

doi:10.4103/jiae.jiae_9_22

REVIEW ARTICLE

Year : 2022 | Volume : 6 | Issue : 3 | Page : 181-185

Atrial Septostomy and Atrial Septal Stenting: Role of Echocardiography

Jayashree Mishra
Department of Cardiology, Bai Jerbai Wadia Hospital for Children, Mumbai, Maharashtra, India

Date of Submission	29-Jan-2022
Date of Acceptance	15-Feb-2022
Date of Web Publication	29-Jul-2022

Correspondence Address:
Dr. Jayashree Mishra
Staff Quarters, 2^nd Floor, B J Wadia Children's Hospital Complex, Acharya Donde Marg, (Next to Tata Memorial Hospital), Parel, Mumbai, Maharashtra
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jiae.jiae_9_22

Abstract

An unrestricted interatrial septal orifice is required in many heart diseases in order to maintain hemodynamics. A variety of interventions have been described to achieve the above goal. This review summarizes each of them briefly. Of these, balloon atrial septostomy and interatrial stenting are the most commonly performed procedures. Echocardiography plays a pivotal role not only in the preprocedural evaluation and patient selection but also in intraprocedural guidance. The outcome of the procedure can also be evaluated immediately by echo on table allowing further attempts or changes in strategy. This review highlights the role of echocardiography in improving accuracy, feasibility, and safety of these procedures.

Keywords: Balloon atrial septostomy, interatrial stenting, septostomy

How to cite this article:
Mishra J. Atrial Septostomy and Atrial Septal Stenting: Role of Echocardiography. J Indian Acad Echocardiogr Cardiovasc Imaging 2022;6:181-5

How to cite this URL:
Mishra J. Atrial Septostomy and Atrial Septal Stenting: Role of Echocardiography. J Indian Acad Echocardiogr Cardiovasc Imaging [serial online] 2022 [cited 2023 Sep 27];6:181-5. Available from: https://jiaecho.org/text.asp?2022/6/3/181/352992

Introduction

In many congenital and acquired heart diseases, a large and unrestricted atrial septal defect (ASD) is needed to maintain hemodynamic stability. Balloon atrial septostomy (BAS), first described by Rashkind and Miller in 1966,^[1] is an interventional procedure that helps in widening a restrictive ASD. A BAS can even be planned antenatally, if a restrictive ASD is found in addition to a specific congenital heart defect on fetal echocardiogram.

BAS is done to either increase interatrial mixing, decompress the left atrium (LA), or augment cardiac output in right-sided obstructive lesions.^{[1],[2],[3],[4]} It is indicated when a restrictive ASD is associated with transposition of the great arteries (TGA), pulmonary atresia with intact ventricular septum, tricuspid atresia, and total anomalous pulmonary venous connection. It is also performed in neonates with hypoplastic left heart syndrome (HLHS) for emergency relief of the transseptal atrial gradient. The procedure and its modifications are also useful in acquired diseases such as severe pulmonary arterial hypertension (PAH) and postoperative right ventricular failure [Table 1].

Table 1: Indications for balloon atrial septostomy^[3],[4]

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From the first description, septostomy has undergone a variety of modifications. In patients with restrictive interatrial communication, dilatation can be obtained by several modalities – conventional balloon septostomy, static balloon, and cutting balloon dilatation. In patients with intact atrial septum or thick septum, the Brockenbrough puncture (needle atrial transseptal puncture) or radiofrequency wire perforations are indicated.^[1] This can then be followed by blade septostomy or interatrial stenting.

Methods

Following its first description, a variety of modifications of this procedural technique have been developed. Among these, most give temporary and short-term palliation preceding definitive surgery. Interatrial septal stenting can provide a long-lasting result, although with increased risk of thromboembolic and mechanical complications.^[3] Atrial flow regulator is another method usually employed in older children with severe PAH or adults with left heart failure which has the potential to provide long-term, regulated interatrial communication.

Balloon Atrial Septostomy

ASDs smaller than 4 mm on echocardiography are considered restrictive in TGA. In sick patients with TGA, creating a nonrestrictive ASD enhances interatrial mixing and increases systemic arterial oxygen saturation and cardiac output. In addition, it lowers the LA pressure. This results in stabilization of these neonates prior to undergoing arterial switch operation. A successful balloon septostomy requires a thin and pliable interatrial septum and hence it is effective in neonates <6 weeks of age.

Transthoracic echocardiography (using subcostal and bicaval views) is increasingly being used to monitor this procedure as single-plane fluoroscopy may not identify balloon position accurately and biplane fluoroscopy increases radiation exposure significantly.^[5],[6],[7] Furthermore, umbilical vein as an access site simplifies the procedure by avoiding need for femoral venous access.^[8] These have resulted in balloon septostomy being frequently performed in the neonatal intensive care unit as a bedside procedure.^[9],[10] Bedside BAS avoids transportation of the patient and radiation exposure and decreases burden on the cardiac catheterization laboratory. For echocardiographic guidance, subcostal view is the best as it allows visualization of both the atria and the atrial septum. Echocardiography helps in identifying catheter location (echo dense material) [Video 1] and aids in maneuvering the balloon catheter under direct visualization across the ASD/patent foramen ovale (PFO) into the LA. This prevents misplacement of the balloon catheter into the atrial appendages, right ventricle, pulmonary veins, or across the mitral valve, thereby reducing the risk of injury to these structures. It also helps in immediate identification of complications such as perforation, valvular laceration, or balloon rupture. In addition, it assesses immediate postprocedure outcome.^[11]

[Additional file 1]

Video 1: Subcostal view showing the echo dense septostomy catheter in the inferior vena cava as it is being advanced toward the right atrium.

Diagnosing left juxtaposed right atrial appendage (JRAA) is important while planning BAS and two-dimensional echocardiography is an excellent method for this. The left JRAA can be recognized by multiple transducer positions (subcostal and parasternal windows) that show both appendages located to the left of the great arteries. The most diagnostic finding of JRAA is the horizontal orientation of the anterior atrial septum in the parasternal short-axis view. In this view, the anterior atrial septum is formed by the floor of the RAA as it courses to the left behind the great arteries.^[12] During balloon septostomy, it is difficult to maneuver the balloon catheter across the abnormally oriented interatrial septum. The leftward positioned RAA might lead to incorrect catheter positioning, thereby making BAS a more risky procedure.^[12]

Procedure

Once vascular access is obtained via femoral or umbilical veins, heparin at 100 IU/Kg is administered. The balloon catheter is guided into the right atrium (RA) through inferior vena cava (IVC) under echocardiographic and fluoroscopic monitoring [Video 1]. The catheter is then maneuvered through a restrictive ASD/PFO into the LA [Video 2]. The balloon is inflated with 1–1.5 cc of diluted contrast or normal saline. The balloon position is checked, preferably under both fluoroscopy and echocardiography [Figure 1]. The inflated balloon in LA should not be within the pulmonary vein or interfere with the mitral valve. With a brisk movement, the balloon is pulled into the RA till IVC-RA junction, where it is immediately deflated. The movement should be sharp, in order to tear the flap of the ovale foramen. To achieve the desired result, the movement might need to be repeated several times. Finally, by echocardiography, the outcome is verified.

Figure 1: Balloon septostomy catheter advanced (a) through restrictive foramen ovale into the left atrium from the right atrium and confirmed on subxiphoid long-axis view of echocardiogram (b) before inflating the balloon (c) for a balloon atrial septostomy (d). Postseptostomy subxiphoid short-axis view (e) with color flow (f) shows the septostomy flap and flows through it. Courtesy: Dr Sivakumar, MMM, Chennai. LA: Left atrium, RA: Right atrium

Click here to view

[Additional file 2]

Video 2: Septostomy catheter seen across the restrictive atrial septal defect with the tip seen within the left atrium.

The adequacy of septostomy can be ascertained by: (1) the size of the defect created, (2) the presence of flail tag of tissue at inferior rim of the ASD that moves from side to side, (3) neutral position of the interatrial septum between the two atria, and (4) a bidirectional flow across the ASD of low velocity, which indicates a lack of pressure difference across the atrial septum [Video 3].^[13] Following successful septostomy, there is clinical improvement with increase in oxygen saturation to at least >60% and resolution of metabolic acidosis. The ASD diameter following successful BAS should be >1/3^rd of the interatrial septal length measured on echo in subcostal view or >5 mm.^{[11],[14],[15]} The postprocedure transatrial gradient measured on pulsed-wave Doppler, is not considered a success criterion by some authors because it has a wide inter-observer variation related to the insonation angle. If the procedure is unsuccessfully evidenced by an inadequate interatrial communication, further attempts are made during the same sitting. This prevents the need for another procedure at a later date or the need for atrial septectomy.

[Additional file 3]

Video 3: Immediate postprocedure evaluation showing a large atrial septal defect with bidirectional flows on color Doppler.

Not all who undergo BAS show a predicable improvement in saturation and up to 20% failure rate has been reported. The causes of inadequate septostomy are incomplete balloon inflation in the LA or its too gentle withdrawal across the interatrial septum. This results in stretching of the ASD instead of creating a tear in the septum primum. A balloon diameter of 10–15 mm is needed to avulse and tear the septum primum. Some patients may not show improvement in oxygen saturation in spite of adequate septostomy and may benefit from prostaglandin E1 infusion.

BAS can have some serious complications such as failure of balloon deflation, balloon rupture [Video 4], perforation of atrial appendage and injury to pulmonary veins, IVC, or mitral valve. Echocardiography will aid in immediate recognition of these complications.^[16]

[Additional file 4]

Video 4: Balloon rupture complicating a septostomy with spillage of contrast within the right atrium.

Transthoracic echocardiography monitoring of BAS can have some limitations. Suboptimal echocardiographic windows are common in ventilated neonates with hyperinflated lungs. Furthermore, in patients in whom an umbilical venous access is used, the echocardiographic probe may interfere with catheter manipulation and vice-versa.

Blade Atrial Septostomy

This derived technique was first described by Park (also known as Park septostomy). It is useful in infants beyond the age of 6 weeks who have thick interatrial septum not amenable to classic BAS. This procedure is usually aided by transesophageal echocardiography and preceded by trans-septal puncture and dilatation. The Park blade catheter is then taken within a long sheath [Figure 2]. The catheter is used to make multiple cuts in the septum by changing its angle. The procedure is finally completed with a static balloon to produce an ASD. The blade can cause serious injury to cardiac structures, hence this technique is rarely used nowadays. It has also been associated with neurological complications.^[17],[18]

Figure 2: Dilated left atrium in a patient with single ventricle, parachute mitral valve, and stenosis shown in three-dimensional echocardiogram (a) where the two pulmonary veins are pointed by arrows. The atrial septum bows (b) into the right atrium due to high left atrium pressures. After septal puncture, dilated left atrium is defined by contrast (c) before a blade septostomy (d). The tear in the atrial septum is shown in subxiphoid long-axis view (e) and three-dimensional image (f). Courtesy: Dr Sivakumar, MMM, Chennai. IAS: Interatrial septum, LA: Left atrium, LLPV: Left lower pulmonary vein, RA: Right atrium, RLPV: Right lower pulmonary vein, SVC: Superior vena cava

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Static Balloon Atrial Dilatations

It was first described in humans by Shrivastava et al. in the year 1987.^[19] This is one of the methods adopted to create an ASD in patients with thick interatrial septum. With the plasty wire parked in the LA, pulmonary vein, or left ventricle, an angioplasty balloon is positioned across the interatrial communication and inflated till the indentation disappears. Contrary to classic BAS, the static balloon produces septal tear due to overstretching with the balloon in a fixed position.^[20] It is used to complement blade atrial septostomy as described in the previous section. This modification helps to reduce or eliminate some of the reported disadvantages of conventional BAS, such as IVC tear and rupture of the soft septostomy balloon.

Cutting Balloon Atrial Septostomy

This was initially described in piglets by Coe. It is useful in patients with thick interatrial septum and small LA where the blade septostomy catheter cannot be used. The interatrial septum is perforated by a radiofrequency wire or a Brockenbrough needle and then the cutting balloon is used. The procedure can be completed by static balloon dilatation.^[21]

Interatrial Septal Stenting

In patients with thick interatrial septum, stenting provides a predictable and long-lasting communication. It is increasingly being used as a method to stabilize these patients or provide a long-term palliation. As described previously, conventional balloon septostomy may not be effective in these patients. Although effective, blade septostomy is fraught with unacceptably high risks of injury to cardiac structures. Static balloon dilatation may not be useful for long-term palliation. Bar-Cohen et al. compared the outcomes of static balloon dilatation with interatrial septal stenting in neonates with HLHS and restrictive ASD. They found no significant differences in outcomes; however, stenting required a smaller balloon diameter to achieve an adequate interatrial communication. The larger balloons used in static balloon dilatation have been shown to produce transient complete heart block in infants.^[22] Stenting of the atrial septum can be complicated by stent malposition, migration, fracture, thrombosis as well as injury to nearby structures.

Echocardiography aids septal stenting in many ways and increases the precision with which the procedure can be completed. In patients with HLHS, echocardiographic scoring systems can serve as a guide regarding the rigidity of the interatrial septum.^[23] This helps predict the force needed to perform trans-septal puncture. Preprocedural evaluation also helps to rule out interrupted IVC or bilateral superior vena cava, tunnel PFO, or thin, multifenestrated interatrial septum.^[24] All of these can pose challenges for the operator during the procedure. It is important to avoid putting the stent in a preexisting tunnel-like PFO. First, transthoracic or transesophageal echocardiography-guided trans-septal puncture is done.^[24] In small neonates, micro-transesophageal echocardiographic probe may facilitate intraprocedural guidance. In hybrid procedures, direct epicardial echocardiography is used to guide the site of puncture. Preprocedural measurement of total biatrial length (from IVC to pulmonary veins) and individual right/left atrial lengths is necessary (especially if LA is small). This helps decide the stent length that can be deployed safely without protrusion into veins or injury to cardiac structures. Usually, the chosen stent length is half the biatrial length and should avoid protrusion into IVC or pulmonary veins.

Echocardiography plays a pivotal role in stent positioning. The stent should be positioned in such a way that its middle third is aligned with the atrial septal tissue. It is taken through a long transseptal sheath with its tip positioned in LA. The stent is first exposed by peeling back the sheath, following which it is deployed by minimal inflation of the balloon. Once partially expanded, the stent position is checked again on echocardiography [Figure 3]. If the position is accurate, the stent is fully deployed leaving a small waist in the middle to create a dog bone or butterfly appearance.^[24]

Figure 3: Atrial septal stenting done for mitral atresia, single ventricle shown in subxiphoid short-axis view (a) and apical view (b). Three-dimensional images (c and d) show the stent between the right atrium and left atrium. Courtesy: Dr Sivakumar, MMM, Chennai. LA: Left atrium, RA: Right atrium, SVC: Superior vena cava

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Postdeployment interrogation of the septum is done to ensure stent position, stability, and the absence of any significant gradient across it. Follow-up echocardiograms, in addition to the above, should look for any interference to the pulmonary venous or IVC flows. A longer stent might lead to erosions in the atrium, or initiate thrombosis within the atrium.

Conclusion

BAS and similar interatrial septal interventions are indicated in conditions which require a patent and unrestrictive interatrial communication in order to maintain desirable hemodynamics. A variety of interventions have been described to achieve the above goal. Echocardiography plays a pivotal role not only in the preprocedural evaluation and patient selection but also in intraprocedural guidance. The outcome of the procedure can also be evaluated immediately by echocardiography allowing further attempts or changes in strategy. It also has a role in follow-up of these patients in order to ascertain long-term patency.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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