Abstract
Left ventricle to aortic conduits were used for the treatment of complex left ventricular outflow tract obstruction in the pediatric population in the mid-1970s. Although this technique has been largely replaced by the Ross-Konno procedure, many patients still have functioning apicoaortic conduits in place today. Few clinical reports or case series exist in pediatric cohorts documenting the natural history or potential long-term complications of this prosthesis. In this report, we describe our experience managing a patient with Shone’s syndrome and an apical aortic porcine-valved conduit remnant that became infected 17 years postconduit valve excision for valvular insufficiency.
Introduction
The management of tunnel aortic stenosis and multilevel obstruction to the left ventricular (LV) outflow tract remains challenging. One of the earliest techniques developed was a left ventricle to descending thoracic aorta valved conduit, creating a double outlet for the left ventricle. These conduits were devised experimentally in 1910 and 1 were successfully implemented clinically for the first time in 1962 (Templeton, MD, 2005, unpublished personal correspondence). Termed apical aortic conduits (AACs), these prostheses were used in earnest for pediatric patients in many centers starting in the mid-1970s. The early- and mid-term results showed promise but long-term follow-up revealed unsatisfactory longevity, largely secondary to poor porcine conduit valve durability. 2,3
The Ross or Ross-Konno operation has now largely replaced AAC but many children, adolescents, and adults still have functioning or nonfunctioning conduits in place. Complications reported in the literature include conduit valve stenosis and/or insufficiency, thrombosis, systemic emboli, and infection. Reoperations are common but when conduits are no longer functional, they are typically ligated rather than excised because complete excision is technically challenging requiring extensive dissection and the possible need for extracorporeal circulation. 2 We report our experience managing a patient whose AAC remnant became infected 17 years postligation and 27 years postimplantation.
Case
Our now 32-year-old female patient was found to have Shone’s syndrome with complex multilevel LV outflow tract obstruction (LVOTO), coarctation of the aorta, and severe LV hypertrophy at six weeks of age. She underwent surgical correction of coarctation at four months of age using subclavian flap aortoplasty. At seven months of age, she underwent aortic valvotomy with resection of an ill-defined subaortic membrane with myomectomy. A residual gradient of 60 mm Hg was reported postprocedure. At five years of age, an AAC containing a 14-mm porcine valve was placed via left thoracotomy without the use of cardiopulmonary bypass. She remained asymptomatic for several years and at the age of nine years had an LV pressure of 120/10.
At 13 years of age, she developed increasing dyspnea and an LV pressure of 190 mm Hg with a gradient into the aorta of 100 mm Hg. An aortic valve replacement (AVR) with Konno aortoventriculoplasty was performed using a 21-mm mechanical prosthesis. The AAC, which was severely stenotic, was not removed at that time. Postoperatively, there was no residual gradient and her exercise tolerance returned to normal.
Two years later she developed severe conduit valve insufficiency with evidence of pulmonary hypertension and LV dilatation. The insufficient porcine valve within the conduit was excised and each end of the conduit over sewn via a left thoracotomy without cardiopulmonary bypass. Postoperatively, the LV function improved significantly and her pulmonary hypertension decreased to mild.
In January 2012, 27 years postinsertion and 17 years postligation of the AAC, she presented with malaise, left-sided pleuritic chest pain, and left shoulder and neck pain. In the interim between her last operation and this presentation, she had developed rheumatoid arthritis and was being treated with steroids and a monoclonal antibody. Her white blood count was 2,000; blood cultures were negative. She had no fever but felt unwell. Chest radiograph and computerized tomographic scan demonstrated a fluid collection surrounding both conduit remnants (Figures 1 –3). The fluid around the conduit was aspirated and grew Streptococcus mitis. She was treated with broad-spectrum antibiotics prior to operation. Employing a fifth interspace left thoracotomy with single right lung ventilation, both conduit remnants were dissected to their origin. A portion of the sixth rib was resected as the graft was densely adherent to this rib. Using femoral arterial and venous extracorporeal circulation, the remnant attached to the apex of the left ventricle was excised and the opening closed with two concentric polypropylene pursestring stitches with homograft pledgets. The Dacron graft was completely removed from the descending thoracic aorta and the defect patched with aortic homograft. Her postoperative course was uneventful and she remains on long-term oral penicillin to which the organism is sensitive. The patient is now back to work full time and has no cardiac symptoms.
This is an image from the coronal portion of the computed tomography (CT) scan demonstrating a fluid collection in the area near the left ventricle (arrow). The conduit is not easily seen in this particular image.
This is an image from the axial sections of the computed tomography (CT) scan. The fluid collection next to the left ventricle is easily seen (arrow).
This shows the left ventricular portion of the conduit (arrow) from another coronal view of the computed tomography (CT) scan.
Comment
This report illustrates the benefits and limitations of AAC as well as one of the more rarely reported complications. Her AAC was placed at a time when short- and mid-term reports were promising regarding the utility of this approach for relief of complex, multilevel LVOTO not amenable to traditional operations. 4,5 Our patient did indeed have four years of excellent palliation with this AAC. However, the weakness of an AAC is the limited long-term durability of the conduit valve, which our patient demonstrated as early stenosis and later insufficiency. This necessitated conduit ligation and valve excision after nearly ten years. The limited durability issue could be obviated by the use of a mechanical prosthesis in the conduit. Nonetheless, the use of the AAC in children and young adults should be limited to those in whom a conventional approach (Konno or other root enlargement procedure) is not feasible. Interestingly, the AAC has been advocated in the adult population with calcific valvular aortic stenosis (with or without porcelain ascending aorta) to potentially avoid the inherent risk associated with cardiopulmonary bypass in the very elderly individuals. 6
Our patient’s history is an interesting compendium of problems related to complex LVOTO including the treatments utilized. Interestingly, she recovered well from each of these without significant sequelae. This report is primarily concerned about her most recent complication, infection, a somewhat rare event associated with AAC implantation. Previous complications reported in the literature include valve stenosis and/or regurgitation and, less commonly, the development of thrombosis, systemic emboli, and pseudo-aneurysm formation. 2,7 Very few infectious complications in these conduits have been reported as case reports or series. 4,8 This report underscores the important clinical point that retained AAC material can become a nidus for infection at any time in the patient’s life. It is highly unlikely that any of these conduits placed in children will be functional into adulthood. Should the entire prosthesis be removed when the valve is no longer functioning? This would be a significantly bigger operation than merely removing the valve and oversewing each end as was done initially in this patient. Given the rarity of late infection, it is difficult to make this recommendation. However, this could have been done at the time of the Konno/AVR without much additional risk and perhaps should be considered as part of the definitive LV outflow tract operation.
Footnotes
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) received no financial support for the research, authorship, and/or publication of this article.