Interact CardioVasc Thorac Surg 2009;8:602-605. doi:10.1510/icvts.2008.199786
© 2009 European Association of Cardio-Thoracic Surgery
Institutional report - Coronary |
Image-guided surgical repair of ventricular septal rupture using self-expanding device
Motoyuki Hisagia,*,
Yoshihiro Suematsua,b,
Akihiro Masuzawaa,
Minoru Onoa,
Noboru Motomuraa and
Shinich Takamotoa
a Department of Cardiothoracic Surgery, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan
b Department of Cardiovascular Surgery, Tsukuba Memorial Hospital, 1187-299 Kaname, Tsukuba-shi, Ibaraki, 300-2622, Japan
Received 28 November 2008;
received in revised form 13 February 2009;
accepted 17 February 2009
 Presented at the 16th Annual Meeting of the Asian Society for Cardiovascular and Thoracic Surgery in Singapore, March 13–16, 2008.
*Corresponding author. Tel.: +81-3-5800-8654; fax: +81-3-5684-3989.
E-mail address: mhisagi-tky{at}umin.ac.jp (M. Hisagi).
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Abstract
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The purpose of this study was to determine the possibility of a new surgical technique for the treatment of ventricular septal rupture after acute myocardial infarction. The operations were conducted under the guidance of real-time three-dimensional echocardiography (RT3DE) (iE33, Philips Medical Systems, Andover, MA). Six pigs were anesthetized, and after median sternotomy, the echo probe was applied directly to the surface of the heart. A ventricular septal defect (VSD) was created in all the six porcine hearts. The VSDs were closed with an Amplatzer septal occluder (AGA Medical Corp, Golden Valley, MN) through the right ventricular free wall under RT3DE monitoring. The procedure was successful in all the six pigs. The VSDs were precisely closed with the septal occluder under RT3DE guidance. Both left ventriculography and color-Doppler echocardiography showed no residual shunt in any of the six pigs. The use of the Amplatzer septal occluder under the guidance of real-time three-dimensional echocardiography made it possible to close the ventricular septal defect safely and successfully without the need to resort to cardiopulmonary bypass. Our results strongly suggest that the application of this new technique is feasible for the treatment of ventricular septal rupture after acute myocardial infarction.
Key Words: Minimally invasive surgery; Device; Echocardiography; Myocardial infarction
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1. Introduction
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Rupture of the ventricular septum following myocardial infarction is a relatively infrequent but life-threatening complication. Several surgical techniques for countering it exist, but their mortality and morbidity rates are extremely high [1]. We demonstrate a new surgical technique against ventricular septum rupture (VSR). The concept of this technique is to plug a ventricular septal rupture with a self-expanding device using 3D ultrasound image guidance in real time (RT3DE) (iE33, Philips Medical Systems, Andover, MA). This method is simple, safe, and minimally invasive.
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2. Materials and methods
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2.1. Surgical devices
The Amplatzer septal occluder (AGA Medical Corp, Golden Valley, MN) was used for VSR (ventricular septal rupture) closure. In brief, this device is made of a Nitinol wire mesh, which is shaped into two disks with a connecting waist. The device is self-expanding and self-centering and can be delivered through a long sheath. To improve its ability to close the VSR, the cavity that exists within each disk and the waist is partially filled with Dacron sewn firmly to the mesh with a polyester thread. A female screw is welded to the center of the right disk for attachment to the delivery cable. The device is available in sizes ranging from 16 to 20 mm in 2-mm increments. The delivery sheath size is dependent on the size of the device and ranges from 6 to 9 Fr.
2.2. Animal study
The study protocol was approved by a review committee at the University of Tokyo. All animals received humane care in compliance with the Guide for the Care and Use of Laboratory Animals published by the US National Institutes of Health (NIH publication 85-23, 1985) and with the approval of the University of Tokyo Institutional Animal Care and Use Committee.
Six female pigs (each weighing 45–50 kg) were anesthetized with Nembutal (30 mg/kg IV), and anesthesia was maintained with additional dosages of Nembutal. Respiration was maintained with a volume-control respirator. The ECG was monitored continuously throughout the procedure. Arterial blood gases were determined every 30 min, and bicarbonate was added as needed to maintain a physiological pH between 7.35 and 7.45. Aortic blood pressure was monitored with a 5 Fr micromanometer-tipped catheter (Millar Instruments) introduced through the left femoral artery.
A median sternotomy was performed. A purse-string suture with a 3-0 monofilament was placed in the lateral wall of the right ventricle, and the echo probe was applied directly to the surface of the left ventricle. After intravenous administration of heparin 100 IU/kg, a 5–10 mm incision was made within the area enclosed by that suture, and a diamond cutter was inserted to carefully form a VSD, which was around 5–10 mm in diameter. The left to right shunt was made small so as to avoid causing the pig's sudden death, but not too small to be seen with color-Doppler echocardiography.
A 5 Fr sheath was placed in the left internal carotid artery by the Seldinger method. A 5 Fr pigtail catheter was inserted into the left ventricle through the sheath under fluoroscopic guidance. Left ventriculography (LVG) was done before and after VSD closure with 30 ml Iopamiron (10 ml/s, 3 s).
All of the surgical maneuvers were performed under RT3DE monitoring. The Amplatzer sheath was inserted into the right ventricle through the purse-string suture with great care to avoid entry of air into the cardiac cavity, and was advanced into the left ventricle through the VSD created. The left side of the Amplatzer device opened immediately. After careful pulling on the device, the right-side disk was extruded. After confirmation of adequate placement, the device was released (Fig. 1).
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Fig. 1. Procedure of the operation. (a) The echo probe is applied directly to the surface of the left ventricle. Created ventricular septal defect (arrow); (b) insert the sheath and open the left side of the Amplatzer; (c) after careful pulling, the right-side disk is extruded; (d) release the device and close the RV.
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After VSD closure was accomplished, the residual shunt was checked by color-Doppler echocardiography and LVG. When there was no residual shunt, the right ventricle was closed with a purse-string suture.
After sacrificing each animal, we opened the heart and checked the configuration of the Amplatzer.
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3. Results
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In all cases, VSDs were successfully created. Inter-ventricular communication was confirmed by 2D and 3D Doppler echocardiography. The location and the orifice of VSD were clearly visualized by RT3DE. LVG showed the shunt flow of VSD in four cases. The mean size of the VSD created was 5.0 mm on the 2D color-Doppler images.
Fig. 2 shows representative sequential images obtained during deployment of the Amplatzer device. The sheath, at whose tip the device was loaded, was inserted through the purse-string suture on the right ventricle and was advanced into the VSD. The left disk was deployed in the left ventricle, and the sheath and the disk were pulled back until the left disk was in full contact with the ventricular septum. The waist and the right disk were deployed while traction was maintained on the delivery cable. The proper position of the device was confirmed, and finally the device was released by rotating the delivery cable counterclockwise. It took about 5 min, on average, from the placement of the purse-string suture to release the device.
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Fig. 2. Images of RT3DE during deployment of the Amplatzer device. (a) Insert the sheath; (b) open the left-side disk; (c–e) pull back the device until the left disk is in full contact with the ventricular septum around the VSD; (f) extrude the right-side disk.
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The results of all procedures are summarized in Table 1. None of the animals had any residual shunt after VSD closure (Fig. 3). There was no significant introduction of air into the right ventricle during the procedure. Postmortem examination demonstrated that the configuration of the devices in the cardiac lumen was ideal. Especially in the left ventricle, the disk of the device was fully open and well fitted to the ventricular septum, and did not encroach on the mitral valve leaflets or the chordae tendineae (Fig. 4).
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Fig. 3. Color Doppler echocardiography and LVG before and after the VSD closure. (a, c) VSD flow before the VSD closure; (b, d) no residual shunt after the VSD closure.
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Fig. 4. Postmortem examination. *, ventricular septum; black arrowhead, the left-side disk of the Amplatzer; white arrowhead, the right-side disk of the Amplatzer. The configuration of the device in the cardiac lumen is ideal. Especially in the left ventricle, the disk of the device is fully open and in full contact with the ventricular septum.
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4. Discussion
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Acquired VSD is a rare, often life-threatening complication of acute myocardial infarction. Before the era of pharmacological and mechanical reperfusion therapy, it occurred in 1–3% of cases, but the incidence is <1% in recent years. However, postinfarction VSD has been recognized as a lethal complication accounting for approximately 5% of early deaths after myocardial infarction [1]. The average time from infarction to rupture has been reported to be between 2 and 4 days, but it may be as short as a few hours or as long as 2 weeks [2]. The most important determinant of early outcome following postinfarction VSD is the development of heart failure (left, right, or both). The associated cardiogenic shock leads to end-organ malperfusion, which may be irreversible. The degree to which heart failure develops depends on the size of the ventricular infarction and the magnitude of the left-to-right shunt [2–5].
It is reported that the survival rate of patients who receive only medical treatment for ventricular septal rupture is 40% in 48 h, 25% in 30 days, and <10% in a year. Early closure of the ventricular septal rupture is necessary, but 30-day survival of those who receive conventional surgical closure is only 47%. Nevertheless, the 5-year survival rate of these 47% is 75% [6]. The 5-year survival rate cannot be called satisfactory, but suggests that an important first step is to survive the perioperative period. One risk factor in surgical closure of a VSR is an operation performed within 24 h after the septal rupture, because the muscle of the ventricular septum is very fragile during that time. Other risk factors include multiple rupture resulting from unsuitable anatomical characteristics, poor preoperative cardiac function, cardiogenic shock, and so on [4, 6]. Surgical invasions, such as cardiopulmonary bypass, induced cardiac arrest, and left ventriculotomy, result in deterioration of the postoperative cardiac function, and also worsen the prognosis [7].
We hypothesized that the avoidance of such surgical invasions can improve prognosis. Our results showed that our method was less invasive surgery than conventional surgical closure techniques in the following respects. The operation can almost always be performed without a cardiopulmonary bypass. In cases of poor cardiac function or sudden collapse of the patient, the operation can be performed with a cardiopulmonary bypass without cardiac arrest or with intra-aortic balloon pump. The left ventricular function may be preserved because left ventriculotomy is avoided.
The Amplatzer septal occluder is a recently developed device. There are several reports of ventricular septal rupture closure with this device by way of catheterization. But there are problems with the catheter method, such as the inaccessibility of the VSD and occasional residual shunts [8, 9]. In the present study, there was no residual shunt. It is speculated that the reason for this was that the angle between the VSD and the device could be selected in this method, so that an almost perpendicular angle can be achieved easily, which makes for a maximal contact area. The problem of inaccessibility is not yet completely solved, but our method may allow coverage of a wide area of the ventricular septum by changes in the location of insertion in the right ventricle. The approach via the right ventricle has advantages to that via the right atrium at the point of this angle and the location because of tricuspid valve.
The surgical maneuvers are performed safely under RT3DE, whereas the catheter method proceeds under fluoroscopic guidance [10]. If the catheter method was performed under RT3DE, the operability would not improve. The management of acute hemodynamic deterioration, like the establishment of a cardiopulmonary bypass, can be performed immediately in this method because the chest is open.
Our study method has some limitations. One is that this study is an acute-phase experiment. The aim of this study was the establishment of the procedure. Therefore a late-phase study, perhaps of three or six months, may be needed in future. Second, the result of the Amplatzer placement on the fragile ventricular septum is not well known. However, a model of postinfarction VSD is difficult to prepare. The solution to this problem is thought to be further improvement of the Amplatzer septal occluder, for example, the enlargement of the left-side disk or the shape modification of the disks to fit better into the location of the VSD. Finally, although this method is a minimally invasive technique, median sternotomy was required to perform all of the surgical procedures in the present study. But it is speed, safety, and reliability that are needed because the target patient is in a critical condition, and this method effects these. In addition, the introduction of a new robotic system and the technological development of the RT3DE system, including a transesophageal echo probe, will make this method speedier and easier.
In summary, acquired VSDs in an animal model were successfully closed with Amplatzer septal occluders, using RT3DE monitoring without cardiopulmonary bypass. This method is thought to be a simple, safe, minimally invasive, and reliable surgical technique. This result strongly suggests that the application of this new technique is feasible for the treatment of ventricular septal rupture after acute myocardial infarction.
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References
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Abstract
1. Introduction
