J Thorac Cardiovasc Surg 2007;133:565-567
© 2007 The American Association for Thoracic Surgery
Facile conversion from mechanical to bioprosthetic composite aortic root replacement
Luca A. Vricella, MD*,
Duke E. Cameron, MD
Division of Cardiac Surgery, The Johns Hopkins Medical Institutions, Baltimore, Md.
Received for publication October 12, 2006; accepted for publication October 24, 2006.
* Address for reprints: Luca A. Vricella, MD, FACS, Division of Cardiac Surgery, The Johns Hopkins Hospital, 600 N Wolfe St, Blalock 618, Baltimore, MD 21287. (Email: lvricella{at}jhmi.edu).
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Drs Vricella and Cameron (left to right)
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Aortic root replacement with a composite valve graft mechanical prosthesis has become established therapy for acute and chronic pathology that eventually leads to enlargement, dissection, or rupture of the aortic root. Although minimal early and late morbidity and mortality have been reported, some patients will require operative reintervention on the neoaortic root, with the goal of conversion from a mechanical to a xenograft aortic valve prosthesis.
We describe an easily reproducible technique that aims at minimizing the degree of complexity of such reintervention while still achieving the goal of freedom from anticoagulation.
Clinical Summary
A 38-year-old man with a history of Marfan syndrome and intravenous drug abuse presented to our institution in 1999 with symptomatic aneurysmal dilation of the aortic root and aortic regurgitation and underwent aortic root replacement with a 27-mm composite mechanical valved prosthesis (St Jude Medical, St Paul, Minn). Despite enrollment in a drug rehabilitation program, the patient was lost to follow-up and presented in September of 2003 with congestive heart failure. Reportedly, he had discontinued oral anticoagulation for 6 months while continuing intravenous drug abuse. Preoperative workup revealed his mechanical prosthesis to be frozen in the open position, with massive aortic regurgitation and an estimated ejection fraction of 15%. Blood culture results were negative.
At the time of the operation, the aortic root was exposed after redo sternotomy and takedown of very tenacious adhesions. Rather than proceeding with root replacement with a xenograft or a homograft with coronary reimplantation, a less-conventional approach was chosen. The Dacron graft was opened, exposing the mechanical prosthesis, immobilized by a well-organized clot. To follow, a 30-mL Foley catheter was inserted within the left ventricular outflow tract and pulled against the inferior margin of the mechanical prosthesis (Figure 1). The valve leaflets were then grasped with a clamp and unhinged from the prosthetic housing; the few prosthetic fragments that were left on the convexity of the exposed balloon were easily retrieved with suction. The Dacron portion of the composite valve graft visible below the coronary ostia was then rimmed with interrupted, horizontal mattress 2-0 braided sutures (Figure 2). The sutures where then passed through the sewing ring of a 23-mm bovine pericardial valve (Edwards Lifesciences, Irvine, Calif), which was lowered in place in the subcoronary position (Figure 3). Cardiopulmonary bypass time and crossclamp time were 38 and 59 minutes, respectively. The postoperative course was unremarkable, and the patient was discharged home on postoperative day 6. He is alive and free from embolic complications 2 years and 7 months postoperatively.
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Figure 1. The Dacron graft has been incised, and a 30-mL Foley catheter has been inserted in the left ventricular outflow tract. The leaflets have been unhinged from the housing of the mechanical aortic root prosthesis.
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Figure 2. Double-loaded, horizontal, mattress braided sutures are then placed circumferentially in the Dacron graft along a horizontal plane between the nadir of the coronary ostia and the superior margin of the valve housing.
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Figure 3. A 23-mm bovine pericardial prosthesis has been implanted, and the mechanical housing is visible in the subvalvar position.
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Discussion
Aortic root replacement with a mechanical prosthesis has been widely used in the treatment of proximal aortic pathology, with excellent short- and long-term outcomes and limited need for operative reintervention.1
There are, however, patients who require reoperation and, in particular, conversion from a mechanical to a biological prosthesis because of issues most often related to oral anticoagulation. Poor compliance with warfarin therapy, recurrent thrombosis, and anticoagulation-related hemorrhage are the most frequent clinical issues that prompt consideration for conversion to a bioprosthesis. In patients with valve thrombosis without intolerance to anticoagulants, thrombolysis and thrombectomy are the only alternatives to replacement.
Reintervention to replace an aortic root prosthesis is often a challenging undertaking because of dense adhesions and the need for reimplantation of the coronary ostia, and although good outcomes have been reported in contemporary series,2,3 bleeding or coronary ischemia in the postoperative phase are distinct possibilities in repeat aortic root replacement. Furthermore, in patients with decreased myocardial function, such as the patient described, an expeditious operation with reduced myocardial ischemic and perfusion times is desirable.
Harada and colleagues4 reported extirpation of a Bjork–Shiley mechanical valve, root enlargement, and insertion of a mechanical prosthesis within the cuff of the valve, a concept also reported in reoperative mitral and aortic replacement by Geha and coworkers.5 In the latter report, the bioprosthetic struts were amputated, and a mechanical valve was sutured to the prosthetic sewing ring (valve-on-valve technique). With the technique described herein, the mechanical prosthesis is not removed in its entirety because the valve housing is left in situ, and the leaflets are simply unhinged. We have found this not to be an issue with thrombus formation in this and in 2 additional cases performed at our institution because the smooth surface of the housing and the high flow within the left ventricular outflow tract are most likely protective against recurrent thrombosis after removal of the leaflets.
The technique reported is reliable, easily reproducible, and offers reduced crossclamp time, potential for bleeding, and coronary malperfusion to this challenging group of reoperative patients.
References
- Gott VL, Cameron DE, Alejo DE, Greene PS, Shake JG, Capparelli DJ, et al. Aortic root replacement in 271 patients: a 24-year experience. Ann Thorac Surg 2002;73:438-443.[Abstract/Free Full Text]
- Hahn C, Tam SKC, Vlahakes GJ, Hilgenberg AD, Akins CW, Buckley MJ. Repeat aortic root replacement. Ann Thorac Surg 1998;66:88-91.[Abstract/Free Full Text]
- Valley MP, Huges CF, Bannon PG, Hendel PN, French BG, Bayfield MS. Composite graft replacement of the aortic root after previous cardiac surgery: a 20-year experience. Ann Thorac Surg 2000;70:851-855.[Abstract/Free Full Text]
- Harada H, Ito T, Mawatari T, Abe T. Replacement of a thrombosed valve after the Bentall procedure. Ann Thorac Surg 2002;73:965-967.[Abstract/Free Full Text]
- Geha AS, Massad MG, Snow NJ. Replacement of degenerated mitral and aortic bioprosthesis without explantation. Ann Thorac Surg 2001;72:1509-1514.[Abstract/Free Full Text]
