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Transcatheter Closure of Ventricular Septal Defect
Zhong-Dong Du, MD; Ziyad M Hijazi, MD
Section of Pediatric Cardiology, Department
of Pediatrics, University of Chicago
Children's Hospital, Pritzker School of Medicine, Chicago, IL, USA
Ventricular septal defect (VSD) accounts for approximately 30% of all congenital heart disease . Although many of these defects are small and close spontaneously [2,3], the larger defects often persist to cause significant shunt and right ventricular hypertension. Large apical muscular VSDs complicate management decisions, particularly when they occur in association with other congenital cardiac defects. The results of surgery for apical muscular VSDs are often suboptimal owing to difficulties in defect visualization, residual shunting, and ventricular dysfunction . Since Porstmann et al  reported the first transcatheter closure of a patent ductus arteriosus in 1967, several interventional techniques have been developed to treat various intracardiac defects, such as atrial septal defect [6-8], patent foramen ovale , fenestrated Fontan , and have yielded promising closure results. VSD had also been targeted as the defect to close with a device 10 years ago, but their widespread use has been limited by several drawbacks such as large delivery sheaths, inability to recapture and reposition and a very high rate of residual shunts due to that devices used at that time were not originally designed for VSD closure [11-14]. In recent years, with the advent of new devices and refinement of techniques, a number of reports on percutaneous closure of VSD have been published with encouraging results [15-27]. According to published data, over 150 patients with VSDs have been reported for transcatheter closure using either the Rashkind double umbrella [11-16, 20, 23] (), the Bard Clamshell , the Button device , the Amplatzer septal, duct or muscular VSD occluder [17-21, 26-27], or the Gianturco coils . The purpose of this article is to review the evaluation of transcatheter closure of VSD, and to comment on some of the devices used for VSD closure.
DEVICE AND CLOSURE RESULTS
Rashkind double umbrella was the first device used for VSD closure. The device is a single-disk composed of polyurethane foam on a hexagonal stainless steel frame ( ) . The device was initially designed for closure of patent ductus arteriosus (PDA) or atrial septal defect (ASD) . In 1988, Lock et al  reported their attempt on transcatheter closure of VSD using a Rashkind device. At that time, Rashkind double umbrella was the only available device and was used to close various kinds of intracardiac defects . The authors pioneered to close postinfarction VSDs and congenital VSDs with this device. They passed through the VSD via the left ventricle and advanced a guide wire to the right heart. By snaring with a venous catheter, they crossed all the 7 VSDs in the 6 patients aged 8 months to 82 years, and could successfully implant a 17-mm double umbrella in each defect. However, all 3 patients with postinfraction VSD died after the procedure. Of the 3 patients with congenital VSDs, one patient died, one still had significant left to right shunt, and only one patient of 44 years of age with a 5 mm VSD had a complete closure. After this first report, a few other studies by the same group of investigators or others showed that although this device could reduce the left to right shunt and decrease rates of operative mortality, reoperation and left ventricular dysfunction in patients with a muscular VSD who needed surgery for other complicated lesions, the overall success rate and closure results were not satisfactory [12-17] ( ). Perforation of right aortic valve cusp, which needed surgery, has been reported in a patient .
|Figure 1. The devices used for transcatheter closure of ventricular septal defects. A, Rashkind double umbrella; B, Sideris Bottoned device; C and D, Clamshell device.|
The Amplatzer devices included septal occluder for ASD closure, duct occluder for PDA closure, PFO occluder for PFO closure and muscular VSD occluder (AVSDO) for VSD closure ( ). They are made of Nitinol, an alloy of 55% nickel and 45% titanium that has superelastic properties . It also has been proven to have excellent biocompatability. Amplatzer septal occluder has a 4 mm waist and a relatively larger left atrial disc. The Amplatzer duct occluder is a mushroom shape device. Full description of these two devices was reported in previous literatures [8,33], the reader is advised to review references 8 and 33.
|Figure 2. The AmplatzerÔ devices used for transcatheter closure of ventricular septal defects. A, Amplatzer septal occluder; B, Amplatzer PDA occluder; C, Amplatzer muscular VSD occluder; D, new concentric Amplatzer VSD occluder; E and F, new eccentric Amplatzer VSD occluders.|
The AVSDO is also a double disc device. The thickness of the Nitinol wire is 0.004" for devices 10 mm and smaller and 0.005" for larger devices. The leading retention disc is 4-mm larger and the proximal disc is 3-mm larger than the diameter of the waist. To achieve immediate complete closure, three Dacron polyester patches are sewn securely with polyester thread into the two discs and the waist of the device. The device size corresponds to the diameter of the waist. The mechanism of closure involves stenting of the VSD by the device and subsequent thrombus formation within the device with eventual complete neoendothelialization. The device is available in sizes from 6-24 mm now that are delivered through 6 to 9 French sheaths (). The delivery system is prepackaged with a long Mullins type sheath, loader, diaphragm with side arm flush, delivery cable and pin vise.
The first use of Amplatzer device for VSD closure in human was reported by Lee et al in 1998 . The authors successfully deployed an Amplatzer septal occluder in a 50-year old patient with acute VSD following myocardial infarction. The patient had significant improvement of clinical condition and a trivial residual shunt. At the time of procedure, the AVSDO was not available. The first use of AVSDO was reported in a study of closure of surgically created VSDs in dogs . The devices were implanted through catheter placed via right ventricular puncture with complete success and a 100% closure rate. The devices exhibited complete endothelialization at 3 months in autopsy examination. The first human implantation of the AVSDO was reported in an 8-month old child with a residual VSD after attempted surgical closure. Complete occlusion was noted after the device was implanted intraoperatively through a right ventricular approach . Tofeig et al  reported the first transcatheter use of AVSDO in a 5-year old girl with mid-muscular VSD. A residual shunt of less than 1 mm was identified by echocardiography at 3-month follow-up. Soon later, a number of studies on AVSDO closure of muscular VSD were reported. The largest number of patients reported by Hijazi et al  had excellent closure results with 100% complete closure rate at 6-month follow-up. A series of six patients were also reported with 100% complete occlusion . The only complication reported was transient arrhythmia that occurred during or immediately after deployment.
The additional advantages of AVSDO are that this device possesses some characteristics rendering it ideal for catheter closure of muscular VSDs in children. It has simple user-friendly delivery system, and requires small delivery sheaths. Therefore, the device can be delivered from the traditional venous route or from the retrograde arterial route. The device is available in many different sizes allowing the operators to close a wide range of defects located in the apical, posterior, anterior or mid-muscular portion of the ventricular septum. The last but the most important feature is the ability to reposition or recapture the device prior to release. Thus AVSDO seems to be a very good device for transcatheter closure of muscular VSD. The device is currently being used in a Phase I trial in the United States.
Button device was first introduced by Sideris et al  in 1990. This device is composed of a square sheet of polyurethane foam supported by two independent, diagonally situated wire arms and a separate counter occluder ( ). The foam occluder can be easily folded into the delivery sheath, and resume its square shape when advanced out of the delivery catheter. The disadvantage of this device is the deployment procedure is complex with a 19%-21% failure rate for ASD closure. This device was initially designed for ASD closure, but it has also been used to occlude PDA. In 1997, Sideris reported their multi-center study of this device to close VSDs . These authors deployed the device through right jugular vein for muscular VSD, and through femoral vein for perimembranous VSD in a total of 25 patients ( ). Only 18 (72%) of the patients had a successful deployment. Of these 18 patients, 13 (72%) had complete closure. At 2-week follow-up, 2 devices migrated from their original position. One patient developed aortic regurgitation due to the right coronary cusp of aortic valve was encroached. One patient had heart murmur recurrence, a moderate residual shunt and device migration which needed to be removed by surgery. So far this is the only report on transcatheter closure of VSD using this device.
Bard Clamshell umbrella
There have been two reports on transcatheter closure of VSD using a Bard Clamshell umbrella [15, 36]. The device was initially designed for ASD closure . It consisted of two opposing self-expanding umbrellas ( , ). The device had been withdrawn from investigational studies in 1991 due to arm fracture and high incidence of residual shunt. The manufacturer (Nitinol Medical Technologies Inc, Boston, MA) redesigned the device and now it is called CardioSeal device. Clamshell umbrella had been used for closure of isolated muscular VSD, VSDs associated with other cardiac lesions or post surgery patch leak [15, 36]. In one of their echocardiography reports , 6, 8, 2 and 3 patients had trivial, small, moderate and large residual shunt after device closure in their 26 patients with TEE assessment of residual shunt. Only 5 (17%) had complete closure. Another echocardiography study showed all 7 patients with closure of their apical muscular VSDs by Clamshell had residual shunt . Thus the efficacy of closure seems not satisfactory with this device. Clamshell device is no longer used right now. There has been no report on its successor, CardioSeal, for VSD closure.
Gianturco coils were originally designed for closure of small to moderate size unwanted vascular communications . Latiff et al used it to close multiple muscular VSDs in a 10-month old boy . These authors successfully deployed 4 and 3 coils, respectively, for a 3.5-mm apical defect and 1.5-2.0 mm mid-muscular defect. A small residual shunt was found at 3-month follow-up with the patient's clinical picture improved significantly. Thus in special situation, Gianturco coils might be also used to close a muscular VSD.
DEVICE IMPLANTATION TECHNIQUE
Different from the atrial septum, the right ventricular trabeculae make crossing a muscular VSD difficult from a venous approach. Therefore a double-catheter approach has been widely used for the muscular VSD closure [12-27]. Generally the protocol of implantation for various devices are similar. Here we summarize the implantation techniques of AVSDO.
The procedure is done under general endotracheal anesthesia. Access is obtained in the femoral vein, the femoral artery and the right internal jugular vein. The patients are fully heparinized with a target activated clotting time of > 200 seconds at the time of device placement. Routine right and left heart catheterization is performed to assess the degree of shunting and to evaluate the pulmonary vascular resistance. Axial angiography is performed to define the location, size and number of VSDs (, ). For single VSD, the use of transesophageal echocardiographic (TEE) monitoring is optional ; however, for catheter closure of multiple muscular VSDs, TEE guidance should be routine. In very small children, TEE may not be well tolerated, transthoracic echocardiographic (TTE) monitoring may be used instead.
|Figure 3. Angiogram in a 9-month old, 8.4-kg child during transcatheter closure of muscular VSD using an AmplatzerÔ muscular VSD occluder. A, left ventricle (LV) angiogram in the 4-chamber view demonstrating a 7.2-mm mid-muscular VSD (arrow). B, cine image demonstrating a 7 Fr Cook sheath (arrow) from the right internal jugular vein through the VSD with an exchange guide wire forming an arterio-venous loop from the jugular vein out the femoral artery. C, cine-image demonstrating passage of the device (arrow) out the distal part of the sheath while pulling the wire from the jugular vein. The LV disk is deployed (arrow) in the LV, note there is a pigtail in the LV for angiography. D, an angiogram in the LV while the LV disk (arrow) was positioned in place. E, cine image releasing the device from the cable (arrow). F, an angiogram in the left ventricle after the device has been released revealing good device position and no, residual shunt.|
|Figure 4. Left ventricular (LV) angiogram in the 4-chamber view demonstrating a 6.3-mm mid-muscular VSD (arrow) in a 13-yr. old, 40-kg child with acquired muscular VSD after surgical repair of hypertrophic cardiomyopathy, followed by Kono operation 5 years later. The Qp/Qs ratio was 2.3:1 and the systolic pulmonary artery pressure was 55 mm Hg. B, cine image demonstrating arterio-venous wire loop from the femoral artery through the VSD and out the right internal jugular vein. C, cine image of a 10-mm Amplatzer MVSD device passing through the sheath (arrows) while the guide wire is still positioned inside the sheath to prevent kinking. D, angiogram in the LV after the LV disk has been deployed (arrow) in the LV. E, cine image during deployment of the right ventricle disk (arrow). F, angiogram in the LV prior to release of device to assess position. G, cine image immediately after the device has been released from the cable (arrow). H, LV angiogram 10 minutes after the device has been released demonstrating good device position and minimal foaming through the device which disappeared the following day, the pulmonary artery pressure dropped to 38 mm Hg.|
A complete TEE study is performed including the standard imaging views: transgastric, frontal 4-chamber, and basal short axis views. Any associated abnormalities are noted and gross assessment of chamber size and function is made. Specific attention is then paid to the VSD and nearby structures, namely, the papillary muscles, moderator band and the chordae tendonae. The atrioventricular valves are interrogated as a baseline for any regurgitation. The VSD is measured in multiple views including the frontal 4-chamber and basal short axis views. Tissue rims and distances from aortic and tricuspid valves are also measured in the above views.
The appropriate device size is chosen to be
equal to or 1-2 mm larger than the VSD size as assessed by TEE and angiographic
evaluation (maximal size at end-diastole). Some operators measure the balloon
stretched diameter of the muscular VSD by inflating a low-pressure balloon placed
across the defect until no shunting is detected via color Doppler . As the
muscular septum is stiff, we believe that balloon sizing for device closure
of muscular VSD is unnecessary.
The next step in the closure sequence is placement of a long sheath (6-8 French) across the VSD. and demonstrate the steps of closure. This can be accomplished in a variety of ways. The most common approach used for mid muscular VSDs is to advance a curved end-hole catheter (Judkins right, or Cobra) into the VSD from the left ventricular side. An exchange length 0.035" Amplatz wire is then advanced through the VSD and the right ventricle into the pulmonary artery. This wire is snared in the pulmonary artery or in the right atrium using the Amplatz gooseneck snare (Microvena Corporation) and is exteriorized out the right internal jugular sheath. This provides a stable rail to allow advancement of the 6-8 French long sheath across the VSD. The sheath is preferentially advanced from the jugular approach to limit the sheath size in the artery. In some patients the catheter course is tortuous and this approach is not possible. The sheath can then be advanced from a retrograde approach through the femoral artery. On occasions to eliminate kinking of the sheath in the aortic arch or the septum area, a 0.018" glide wire is left inside the sheath while advancing the delivery cable and device. Once the device reaches the tip of the sheath, the wire is removed prior to deployment of the ventricular disk. In some patients with larger VSDs, the catheter could cross from the right ventricular side. If the VSD is crossed and a catheter can be placed in the body of the left ventricle the stiff wire is advanced into the left ventricle and the sheath is advanced through the right internal jugular vein into the left ventricle.
On occasions, we use the femoral vein approach for device deployment. This approach should not be used unless deployment through the jugular vein is not possible.
Once the sheath is in proper position the appropriate sized VSD device is then screwed onto the delivery cable and pulled into the loader under water. The loader is then flushed with saline through the side arm of the valve supplied with the delivery system to prevent any air embolism. The loader is placed into the proximal end of the long sheath and the device is advanced with short pushes of the delivery cable to the distal tip of the sheath. The cable should be advanced without rotation to prevent premature unscrewing of the device. The device is then slowly advanced out the sheath to allow the distal disc to expand. In the cavity of the LV, repeat small injections using the pigtail catheter positioned in the LV after each step is of paramount importance. These injections are used for optimal device positioning. The device and sheath are then retracted against the septum with gentle tension and the sheath is retracted to open the waist of the device in the VSD and open the proximal disc against the opposite side of the septum. The device position is then assessed using TEE in multiple views (). Atrioventricular valves are assessed for any induced valvular regurgitation. Angiographic assessment of device position is performed using the pigtail catheter in the left ventricle or through the side arm of the delivery sheath if the arterial approach is used (or via a pigtail catheter from the contralateral femoral artery). If the device is not well positioned across the VSD or increased valvar regurgitation has been noticed the device can be easily recaptured into the long sheath. The above steps are then repeated and the device repositioned.
|Figure 5. Transesophageal echocardiographic (TEE) images in a 31.5 year old, 123.5-kg male patient with a 4.5-mm mid-muscular VSD and a Qp/Qs ratio of 1.5. A and B, Left ventricular long axis view without (A) and with color Doppler (B) showing the muscular VSD (arrow); C, TEE image in the long-axis view demonstrating passage of the delivery sheath from the right to the left ventricle through the VSD. D, TEE image in the 4-chamber view during deployment of the LV disk (arrow). E and F, TEE images without (E) and with color Doppler (F) after a 6-mm AmplatzerÔ MVSD device (arrow) has been deployed demonstrating good device position and no residual shunt. AO, aorta, LA, left atrium; LV, left ventricle; RV, right ventricle.|
If device position is satisfactory, the pin vise is then fixed onto the delivery cable and the device is released with counter clockwise rotation. A repeat angiogram is performed in the left ventricle 10-minutes after release to assess the closure. After device release a brief, complete TEE study is performed with additional imaging in multiple planes to confirm device placement, assess for residual shunting and any obstruction or regurgitation induced by the device (). The device orientation commonly changes slightly as the device is released from the delivery cable and tension on the device is eliminated which allows it to completely align with the septum.
The patients receive a dose of an appropriate antibiotic (commonly Cephazolin at 20mg/kg) during the catheterization procedure and two further doses at eight-hour intervals. The patients are recovered in an appropriate setting and are routinely discharged the following day. Observation of subacute bacterial endocarditis prophylaxis is recommended for 6-months or until complete closure is obtained. Patients are maintained on 3-5 mg/kg of aspirin per day for six-months. Patients are instructed to avoid contact sports for one month. Follow up includes TTE, chest radiograph and EKG at 6 months post closure and yearly thereafter.
Patients are selected for transcatheter occlusion based on the presence of a hemodynamically significant VSD with left to right shunt. The patients are evaluated with history, physical examination, EKG, and a TTE. All patients should have clinical and or echocardiographic evidence consistent with a hemodynamically significant VSD. Exclusion criteria include: weight less than 3.0 kg; distance of less than 4 mm between the VSD and the aortic; pulmonic; mitral or tricuspid valves; pulmonary vascular resistance greater than 7 Woods units; sepsis and patients with conditions that would be expected to be exacerbated by the use of aspirin unless other anti-platelet agents could be used for six months.
Prior to the transcatheter closure procedure, a comprehensive TTE study is of critical importance. Accurate delineation of anatomic details of the number and location of defects, their origin and exit on the left and right ventricular aspects, and their relationships with neighboring muscle bundles and valvular apparatus are important for effective transcatheter therapy. For apical muscular VSD, the anatomy in the apical region is also important for the choice of device and implantation route .
SUMMARY AND FUTURE CONSIDERATION
In view of interventional treatment, VSD is much more complicated than secundum ASD or PDA. There are valve apparatus in both ventricular cavities. There are also moderator and other muscle bands in the right ventricular cavity. The chordae tendonae and papillary muscle of septal leaflet of tricuspid valves sit on the septum. Perimembranous VSD usually located in an area quite near the aortic and tricuspid valves. Encroaching any of these structures would cause severe complications. In addition, the position and orientation make the defect difficult to be passed by catheters or guide wires. Therefore most of the defects targeted for closure are muscular defects which are at least 4 mm away from any cardiac valves. The closure results and safety depend on the device used, and also the location of the defects. With Rashkind double umbrella, Buttoned device and Bard Clamshell device, the general success rate and complete closure rate are lower, while the fluoroscopy time and procedure time are longer than the Amplatzer device. With the newly designed AVSDO, the complete closure rate was as high as 100% in the two small series of patients [20,27]. Besides, AVSDO has simple and small delivery system, and can be effectively repositioned or retrieved until it is released in an optimal position. Thus with the newly designed device, transcatheter closure of muscular VSD in selected patients can be used as an alternative for surgical closure.
The limitation of AVSDO is that it can only be used to close muscular VSD. As muscular VSD only account for 10% of VSDs, a large number of patients with VSDs still could not benefit from this procedure. Very recently, Gu et al  tried to close perimembranous VSD in a swine model using specially designed devices modified from AVSDO. The devices had either concentric or eccentric left-sided retention disks (). Thus positioned appropriately, the devices could minimize the risk of interference with aortic or other cardiac valve movement. The authors successfully deployed the devices in 11 of their 12 piglets with a 91%, 91% and 100% complete closure rate at 1, 3 and 6-month follow-up. An associated aneurysm of the membranous septum increased in size in 2 of the 3 animals using concentric device, and in none of the animals using eccentric device. Aortic regurgitation occurred in 2/3 animals with concentric device, and only 1/8 animals with eccentric device. Pathologic examination showed that all devices were covered by smooth neoendothelium at 3 months. The closure result and safety are very encouraging, especially with the eccentric device. Some investigators also tried to close perimembranous VSD with enforced nitinol coils. Therefore that in the future, new devices for closure of perimembranous VSD would be available.
The complications encountered in transcatheter closure of muscular VSD using an AVSDO are arrythmias occurred during or soon after the procedure. Fortunately all the reported arrhythimias were transient. However, data on this complication after the deployment of devices is still needed because the potential that Nitinol device might interfere with the conduction or other electrophysiologic properties of the ventricular muscles.
In conclusion, the initial experience with
transcatheter closure of muscular VSDs in selected patients has been very encouraging
with the newly designed AVSDO. All the common types of muscular VSDs can be
effectively occluded with this device. If further investigation and follow-up
continue to produce similar results, this device may become an important component
in the armamentarium of the interventional cardiologist caring for patients
with congenital heart disease. Although the results of transcatheter closure
of perimembranous VSD with Rashkind double umbrella and Buttoned device seems
not so satisfactory, a specially designed new Amplatzer eccentric device has
shown hope for transcatheter closure of this category of VSD.
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