Interact CardioVasc Thorac Surg 2008;7:1129-1130. doi:10.1510/icvts.2008.183624
© 2008 European Association of Cardio-Thoracic Surgery
Negative results - Valves |
Wall rupture of Medtronic Freestyle stentless porcine aortic root bioprosthesis
Tomohiro Mizuno*
Department of Cardiovascular Surgery, Machida Municipal Hospital, 2-15-41, Asahi-machi, Machida, 194-0023, Tokyo, Japan
Received 11 May 2008;
received in revised form 15 July 2008;
accepted 16 July 2008
Corresponding author: Tel.: +81-42-722-2230; fax: +81-42-720-5680.
E-mail address: t-mizuno{at}yhc.att.ne.jp (T. Mizuno).
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Abstract
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The Medtronic Freestyle stentless bioprosthetic valve provides excellent hemodynamics and long-term durability. However, several studies have reported mid-term structural valve deterioration unique to cases of Freestyle bioprosthesis implantation. According to these reports, the degeneration of the porcine aortic wall causes the dilatation and disruption of the sinus of Valsalva. We encountered a very rare case of an 8 mm-long tear located just above the inflow end of the Dacron cloth. The sudden rupture of the bioprosthetic aortic wall formed a pseudoaneurysm that compressed and almost occluded the pulmonary artery leading to low cardiac output syndrome and shock.
Key Words: Heart valve; Stentless; Rupture; Aortic root
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1. Introduction
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The Medtronic Freestyle stentless bioprosthesis is expected to provide an excellent hemodynamic advantage over conventional stented bioprosthetic valves [1]. With regard to the durability, Mohammadi et al. demonstrated that freedom from structural valve deterioration (SVD) at 10 years was 95.8% (12/475 patients), e.g. leaflet tear (10), valve calcification (1), and cusp fibrosis (1) [2]. Bach et al. have reported that freedom from SVD at eight years is 98–100% [3]. However, some case reports have described the mid-term SVD in patients with a Freestyle bioprosthesis; this SVD differed completely from the SVD of conventional stented valves [4, 5]. Here, we report a very rare SVD involving a sudden tear in the porcine aortic wall followed by development of the low cardiac output syndrome (LOS).
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2. Case
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A 31-year-old woman was transferred to our hospital for investigation of a sudden onset of severe dizziness and nausea. Her blood pressure was 80/50 mmHg. She had undergone aortic valve replacement twice. The first aortic valve replacement was performed six years prior to admission for infective endocarditis; a 19-mm Medtronic Freestyle stentless bioprosthesis was implanted in the subcoronary fashion. The second replacement was performed three years prior to admission for stenosis of the left ventricular outflow tract caused by pannus formation; a 23-mm Medtronic Freestyle valve was inserted in a full root fashion following Konno's aortic annular dilatation technique and coronary artery bypass grafting to the right coronary artery. The neurologist diagnosed no neurological deficit in the patient. The echocardiogram indicated no aortic regurgitation or stenosis; severe tricuspid valve regurgitation with right ventricular dilatation was observed. Computed axial tomography (CAT) scans revealed that the aortic bioprosthesis had no structural deformation, but the right ventricular outflow tract (RVOT) and the main pulmonary artery (PA) were compressed and nearly obstructed by a highly enhanced extracardiac mass lesion (Fig. 1). An emergency surgery was required for removal of the mass.
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Fig. 1. Pulmonary artery is compressed and almost obstructed by the highly enhanced mass lesion (pseudoaneurysm). Black arrow: pseudoaneurysm, PA: pulmonary artery.
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The mediastinum was exposed in the third sternotomy. Severe arterial bleeding began suddenly from the middle of the mediastinum during dissection. A femoro-femoral bypass was performed and hypothermia was induced. The ascending aorta and the PA were covered with a bioprosthetic pericardial sheet which had prevented the adhesion to the sternum. We found that the massive bleeding originated from under the bioprosthetic sheet, and the highly enhanced mass on CAT scans was a pseudoaneurysm covered with the bioprosthetic sheet that compressed the RVOT and PA. Under circulatory arrest with deep hypothermia, the bioprosthetic pericardial sheet was removed and the bleeding point was exposed. The bioprosthetic aortic wall just above the inflow end of the Dacron cloth was torn by 8 mm (Fig. 2). Signs of infection or aneurysmal formation in the wall were not recognized. The tear was closed with 4-0 monofilament sutures reinforced with felt strips. The patient's postoperative course was uneventful.
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Fig. 2. The aortic wall just above the Dacron cloth of the inflow was torn by 8 mm. Arrow: tear, dotted arrow: Dacron cloth of the Freestyle bioprosthesis, CA: porcine coronary artery.
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3. Discussion
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Several studies have reported some types of SVD that are uniquely associated with Freestyle stentless bioprosthesis implantation. If a valve dehiscence occurs at the inflow or outflow suture line of the Freestyle valve implanted by the subcoronay technique, a cavity between the preserved porcine aortic wall and the native aortic wall is filled with a hematoma that destroys the three-dimensional structure of the Freestyle valve, leading to SVD [4].
The degeneration of the porcine aortic wall also induces SVD [5]. When the stentless bioprosthesis is implanted by the full root technique, the degeneration causes the porcine aortic wall to weaken. Aortic wall rupture may occur following dilation of the wall and formation of an aneurysm. Because the perforation of the porcine aortic wall often occurs at the non-coronary sinus, a pseudoaneurysm, which can be detected by the CAT scan, is formed around the aortic wall. But this type of SVD sometimes results in a catastrophic outcome.
In this patient, the tear was located just above the inflow of the Dacron cuff. The suture of the Dacron cuff might have weakened the aortic wall and induced the tear at this site. Further, no aneurysmal formation or infection of the aortic wall was observed. Because the location of the tear was different from that observed in other cases, the mechanism responsible for the formation of the tear in this case is considered to be completely different from those involved in the former two types of SVD. Unfortunately, because any pathological study could not be performed, we could not assess which factor had caused the SVD in this case.
Interestingly, the unique SVDs of the Freestyle porcine aortic root bioprosthesis mostly occurred in patients with aortic valve incompetence; in such patients, relatively larger valves were selected. This tendency might be a key point in unveiling the mechanism of catastrophic SVD in cases of Freestyle aortic bioprosthesis implantation.
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References
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- Borger MA, Carson SM, Ivanov J, Rao V, Scully HE, Feindel CM, David TE. Stentless aortic valves are hemodynamically superior to stented valves during mid-term follow-up: a large retrospective study. Ann Thorac Surg 2005;80:2180–2185.[Abstract/Free Full Text]
- Mohammadi S, Baillot R, Voisine P, Mathieu P, Dagenais F. Structural deterioration of the Freestyle aortic valve: mode of presentation and mechanisms. J Thorac Cardiovasc Surg 2006;132:401–406.[Abstract/Free Full Text]
- Bach DS, Kong ND, Dumesnil JG, Sintek CF, Doty DB. Eight-year results after aortic valve replacement with the Freestyle stentless bioprosthesis. J Thorac Cardiovasc Surg 2004;127:1657–1663.[Abstract/Free Full Text]
- Takami Y, Masumoto H, Fyfe-Kirschner B. Late disruption of a Freestyle stentless bioprosthesis used for repair of sinus of Valsalva aneurysm of non-coronary cusp. Ann Thorac Surg 2007;83:2210–2212.[Abstract/Free Full Text]
- Ozaki N, Hino Y, Hanafusa Y, Yamashita T, Okada K, Tsukube T, Okita Y. Perforation of the Valsalva sinus after implantation of Medtronic Freestyle aortic bioprosthesis. Ann Thorac Surg 2006;82:2282–2285.[Abstract/Free Full Text]
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Abstract
1. Introduction