Iatrogenic Atrial Septal Defect Closure Through the Steerable Guide Catheter: Description of Technique and Single-Center Experience

Abstract

Objectives. To introduce a novel method of direct iatrogenic atrial septal defect (iASD) closure through the MitraClip steerable guide catheter (SGC). Background. MitraClip implantation requires transseptal puncture and the creation of an iASD. There are relatively rare instances, such as hemodynamically significant shunting or concerns for embolus, where iASD must be closed during index procedure. In these instances, it may be beneficial to not give up access to left atrium. Methods. We retrospectively reviewed all iASD closures during MitraClip implantation at our institution from 2015 to 2020. Cases where an ASD occluder was deployed directly through SGC were included. Results. Eleven patients had immediate iASD closure through the SGC. Indications for using this method included concern for paradoxical embolus, large defect size and/or significant shunting. Closure device sizes ranged from 8 to 22 mm. Mean time from removal of clip delivery system to occlusion of iASD was 14.6 minutes. There were no procedural complications related to iASD closure using this method. Conclusion. Closure of iASD intra-procedurally directly through transseptal guide sheath via the method described was safe and allowed for continuous left atrium access.

J INVASIVE CARDIOL 2022;34(8):E633-E638. Epub 2022 July 27.

Key words: iatrogenic atrial septal defect, MitraClip, transcatheter closure

Transcatheter mitral edge-edge repair is now the established therapy for symptomatic prohibitive surgical risk patients with primary mitral regurgitation (MR) and for goal directed medical therapy treated patients with secondary MR.^{1, 2} The implantation of MitraClip (Abbott Vascular) necessitates transseptal puncture ultimately leading to insertion of a 22-Fr steerable guide catheter (SGC) across the inter-atrial septum. At the conclusion of the procedure, the SGC is withdrawn from the left atrium leaving behind an iatrogenic atrial septal defect (iASD).

There has been substantial interest in the implanting community as it relates to the natural history of iASD and the need for observation versus percutaneous closure.^3-5 In the latest Transcatheter Valve Therapy (TVT) registry publication, rates of iASD closure were 1.5%.⁶ In those where iASD closure is performed, there too has been a recent publication on the indications, expectations, and risks of percutaneous closure.⁷ Though not based on any specific randomized studies or societal guidelines, the generally accepted indications for iASD closure include evidence of right-to-left shunting, patients with severe pulmonary hypertension or right ventricular dysfunction, and/or those at risk for paradoxical embolus.⁸

Despite this interest in iASD closure, very little has been published on the technique nor outcomes related to iASD closure intra-procedurally. We believe most operators remove the SGC from the left atrium and re-insert an additional sheath over a wire. This results in loss of continous access to the left atrium, potential (albeit low) risk of right-to-left paradoxical embolus in patients with fibrinous or thrombotic material on right-sided leads, or transient risk of right-to-left shunting. To close the defect, the operator is now required to recross the septum for percutaneous closure. Herein, we describe an approach to percutaneously close the iASD through the MitraClip SGC without sacrificing risk of right-to-left shunting or paradoxical embolus during catheter exchanges.

Methods

Study design and data source. This single center retrospective study was conducted using institutional procedural databases derived from the University of California at Davis Medical Center (2015-2020). The Institutional Review and Ethics Board approved the study protocol.

Study population and data collection. All consecutive patients with severe (3-4+) symptomatic MR meeting approved indications for MitraClip implantation were eligible. During the study period a total of 303 patients underwent MitraClip implantation as previously described.⁹ During the same period, 11 patients underwent iASD closure intra-procedurally utilizing the closure technique described herein.

iASD closure via MitraClip SGC guide. After deployment of the last MitraClip, the clip delivery system (CDS) is removed in standard fashion leaving behind the 22-Fr SGC in the left atrium (Figure 1A). Next the Torqvue sheath (Abbott Vascular) with dilator (appropriately flushed and assembled) are advanced through the SGC valve in entirety (Figure 2A and 2B). At this point, the distal end of the Torqvue sheath remains within the SGC by 20 centimeters. The Torqvue dilator is removed and the sheath is aspirated and flushed in standard fashion and hemostasis achieved either by attaching a syringe or stopcock. On the back table, the selected occluder device is de-aired, flushed, prepped, and loaded per standard manufacturer specifications. The loading tube is then connected to the Torqvue sheath (in a fluid-to-fluid manner) and the Amplatzer cable is advanced allowing the collapsed occluder device to advance from within the loader and into the sheath (Figure 2C and 2D). However, given the discrepant lengths (Figure 3), when the occluder cable is advanced as far as allowable, the device has exited the Torqvue but remains constrained within the distal end MitraClip SGC. At this stage, on the backend, the occluder lock is disengaged and removed, next the loading tube (along with its Y connector) is disassembled and removed (Figure 2E). At this step, it is important to keep the proximal end of the Torqvue sheath below the level of the patient’s heart to prevent air entrainment. Next, the loading tube is disconnected from the Y connector followed by immediate advancement of the Y connector alone over the delivery cable to connect with the proximal end of the delivery sheath (Figure 2F). Hemostasis has now been re-achieved. By removing the loading tube, there is now sufficient cable length to advance the occluder beyond the distal end of the MitraClip SGC. The cable is advanced until the left atrial disc is deployed within the left atrium (Figure 2G and Figure 1B). The entire system is retracted until the left atrial disc is flush against the interatrial septum (Figure 1C). Next, the MitraClip SGC is withdrawn as the right atrial disc is formed (Figure 1D). Once appropriate positioning is confirmed, the delivery cable can be counterclockwise rotated per standard fashion until the threaded insert disengages and the device is fully deployed. The MitraClip SGC is now removed and femoral venotomy secured.

Data definitions. Baseline demographics, transthoracic echocardiography (TTE), transesophageal echocardiography (TEE) and hemodynamic parameters were collected based on established definitions in the literature. At our institution, multiple TEE clip acquisitions (with corresponding time stamp) are conducted throughout the key parts of the procedure. Procedural time was defined as the time from transseptal puncture to the time when the final clip is deployed. iASD occluder time was defined as time from clip delivery system (CDS) removal to the time the delivery cable is disengaged from the occluder device. Procedural success was defined as implantation of at least 1 clip with reduction in MR to 2+ or less prior to hospital discharge.¹⁰

iASD defect size was measured on TEE imaging. Large defect was defined in this study as >12 mm. Left-to-right shunting was evaluated with color Doppler on TEE. The assessment on the degree of shunting was subjective, based on color flow and size of the defect. Pulmonary artery pressure was obtained from a pulmonary artery (PA) catheter, and standard definitions for pulmonary hypertension were used when evaluating pulmonary artery systolic pressure.

Results

From January 2015 to July 2020 there were 303 MitraClip procedures performed. There was a total of 20 iASD closures (6.6%) during the index procedure. Of these 20 immediate iASD closures, 11 were performed through the SGC.

The patients had a mean age of 79.0 and 27.3% were female. Prior to the procedure, patients had New York Heart Association (NYHA) functional class III (81.8%) or IV (18.2%) symptoms. Eighteen percent of patients had previous procedures requiring transseptal puncture, either left atrial ablation or left atrial appendage closure. Implantable cardiac devices (ICDs) were present in 7 patients (63.6%). Baseline characteristics of this cohort are described in Table 1.

Indications for iASD closure through the SGC included concern for paradoxical embolus, either due to mobile material on pacemaker leads or seen elsewhere on TEE, large iASD defect size, significant bi-directional shunting, and elevated PA pressures. The relative frequency of each indication is displayed in Figure 4.

In 4 cases (36.3%), it was deemed necessary to perform closure of the iASD before pulling the sheath into the right atrium. In all 4 of these cases the indication for closure was prevention of embolism due to mobile material seen in the right atrium by TEE. In the 7 other cases the guide sheath was pulled back into the right atrium but then was advanced back into the left atrium to deploy the closure device. Amplatzer devices (Abbott) were used in all cases to close the defect. Devices included the Amplatzer septal occluder (ASO), the Amplatzer cribiform multifenestrated septal occluder and the Amplatzer patent foramen ovale (PFO) occluder. Mean procedure time was 81.7 minutes, with mean occluder time 14.6 minutes. The sizes ranged from 8 to 22 mm. Procedural details are reported in Table 2.

None of the cases resulted in complications related to either the index procedure or the deployment of the ASO device. There were no instances of air embolism, device embolism, or failure to deliver the device. Patients were followed for a minimum of 30 days. There was 1 death (8.3%) due to an unknown cause and no myocardial infarctions or strokes. At repeat TTE, available for 10 patients, there was no evidence of persistent iASD.

Discussion

Main findings. To our knowledge, this is the first published report on a technique that allows immediate closure of iASDs without loss of left atrial access. In this small series, the technique is safe, reproducible and may have the potential to improve efficiency by eliminating need for multiple catheter exchanges to close iASD (when indicated).

Implication of persistent iASD. The rate of persistent iASD after MitraClip procedures has ranged from 27% to 50% at 6 months in previous studies.^5,11 Most agree that minimal left-to-right shunting does not warrant immediate closure, unless in rare instances where the defect is large and thus unlikely to close spontaneously.¹² Previous studies have shown a direct correlation between catheter size and the size of the created iASD.¹³ The distal end of the MitraClip steerable guide is 22 Fr indicating an expected iASD of approximately 7.3 mm. In the vast majority of cases, the residual defect is often slit-like rather than a discrete circumferential “hole” and may not necessitate closure. In the present series, the 2 cases with defect closure due to size had TEE iASD maximum dimensions of 12.7 and 15.0 millimeters. Previous studies have used the cutoff of 10 millimeters to define “large iASD.”⁷ Factors associated with larger iASD size include extensive movement of the SGC, longer duration of procedure and high left atrial pressure.¹⁴

The most common indication for immediate closure through the large bore sheath was to prevent paradoxical embolism, representing the cause for immediate closure in nearly half of cases. In all 4 cases where closure was performed prior to withdrawing the guide sheath from the left atrium, mobile material was seen in the right atrium, either on pacemaker leads, on the septum, or on the steerable guide catheter. The method of iASD closure demonstrated here presents a novel way of quickly closing an iASD without giving up access to the left atrium or further instrumentation of the septum, which may prevent thrombi from embolizing systemically.

In our cohort, more than half of patients had ICDs. Previous studies have demonstrated that leads of ICDs can cause an increase in risk of stroke in patients with septal defects.¹⁵ A recent study has demonstrated a 75% increase in transient ischemic attacks, stroke or systemic embolism in patients with ICDs after transeptal procedures compared to those without devices.¹⁶ It is important to note that ICDs appear to be a risk factor for thrombus formation and require special consideration during transeptal puncture procedures due to the risk of paradoxical embolism.

In the case where iASD was closed due to elevated PA pressure, the pulmonary artery systolic pressure was measured at 73 mmHg. In the setting of right ventricular dysfunction and elevated right-sided pressures, there remains a clinical concern for symptomatic right-to-left shunting with hypoxia.^7,14,17

Need for iASD closure without loss of LA access. In the absence of this technique, closure of the iASD brings about several important procedural hurdles. First, removal of the MitraClip SGC over-the-wire with or without maintaining a left atrium rail is required. During this period there remains a theoretical and potential risk for paradoxical embolism. Second, after removal of the SGC from the body there is a need to maintain hemostasis at the venotomy while the selected closure device is prepped for delivery and deployment. This can occur by either inserting an access sheath with a similar outer diameter as the MitraClip SGC or using a smaller side arm sheath that would accommodate the iASD closure sheath while tightening down on ProGlide sutures (if used). These approaches can add to the cost of the overall procedure and based on the size of the replacement sheath used, can cause bleeding at the venotomy. Finally, if an LA rail was not maintained, the iASD would require re-crossing before ultimate iASD closure. This adds to the risk of paradoxical embolism especially if hardware must be navigated through the previously identified thrombus or fibrinous material on devices and/or the septum.

Closure of the iASD through the large bore MitraClip guide provides a novel and quick method to deliver an atrial septal occluder without giving up access to the left atrium and circumvents the need to find a replacement sheath all while maintaining hemostasis. Immediate closure of ASD during the index procedure remains rare, with an incidence of only 6.6% in our study. In the latest publication from the TVT registry, immediate iASD closure rates were 1.5%.⁶ The data presented here demonstrate overall safety of utilizing this approach, without the need for recapture and redeployment of any device, and without any immediate complications during the procedures. 

Device selection for iASD closure through the SGC. In our cohort, only Amplatzer devices were used due to their ability to be delivered via smaller sheath sizes and ability to maximize usage of the delivery cable. The minimum sheath size needed depends on the size of the septal occluder device delivered, and thus the size of the defect. In general, the SGC can accommodate any Torqvue sheath needed for closure of all devices used to close iASD. The Gore Cardioform Occluder is the only other commercially available product in the US which has been used for iASD closure. The device comes pre-packaged and is a larger profile delivery catheter.¹³ Most importantly, there is no manner in which the working delivery rail can be extended or modified as is done with the Amplatzer system. As such, use of this device through the MitraClip SGC is not feasible. This is an important technical aspect to consider when selecting what closure device to use in this method.

Study limitations. The retrospective nature of this investigation carries inherent biases. However, the group of patients selected for iASD closure represent those referred consecutively. Complete seal was achieved with different sizes and types of devices all from the same manufacturer. However, alternative manufacturer devices are not technically feasible to be delivered via this approach.

Conclusion

Closure of an iASD at the conclusion of large-bore transseptal structural heart procedures is not a common occurrence. Persistence of a defect has been linked with worsened outcomes in certain scenarios. In cases where closure of the defect is desired prior to removing the large bore transseptal guide sheath, the technique shown herein may be used to close the defect without loss of left atrium guide access. In this small single-center series, the technique is safe and reproducible.

Affiliations and Disclosures

From the Division of Cardiovascular Medicine, University of California Davis Medical Center, Sacramento, California.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Smith reports consulting fees from Abbott, Gore Medical, Boston Scientific; lecture honoraria from Abbott. Dr Singh reports consultant, advisory board, and proctor fees from Abbott Vascular, Boston Scientific, and W.L Gore and Associates. Dr Stripe reports consulting fees from Abbott. The remaining authors report no conflict of interests regarding the content herein.

The authors report that patient consent was provided for publication of the images used herein.

Manuscript accepted February 10, 2022.

Address for correspondence: Gagan D. Singh, MD, 4860 Y Street, Suite 2820, Sacramento CA 95616. Email: drsingh@ucdavis.edu

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