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Ann Thorac Surg 2005;80:2301-2308
© 2005 The Society of Thoracic Surgeons
a Section of Cardiothoracic Surgery, James W. Riley Hospital for Children and Indiana University School of Medicine, Indianapolis, Indiana
b Section of Pediatric Cardiology, James W. Riley Hospital for Children and Indiana University School of Medicine, Indianapolis, Indiana
c Department of Surgery, St. Louis University School of Medicine, St. Louis, Missouri
Accepted for publication June 3, 2005.
* Address correspondence to Dr Brown, Section of Cardiothoracic Surgery, Indiana University School of Medicine, 545 Barnhill Dr, EH 215, Indianapolis, IN 46202-5123 (Email: jobrown{at}iupui.edu).
Presented at the Poster Session of the Fifty-first Annual Meeting of the Southern Thoracic Surgical Association, Cancun, Mexico, Nov 2–4, 2004.
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Abstract |
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METHODS: Records of 28 patients (age range, 2 weeks to 19 years) who underwent insertion of apical aortic conduit between September 1979 and June 1993 were reviewed. All patients had complex multilevel left ventricular outflow tract obstruction. All were symptomatic, and 22 (79%) had had one or two previous aortic valvotomies or left ventricular outflow tract operations, or both.
RESULTS: Hospital mortality was 11% (3 of 28). Twenty-five children survived the perioperative period and improved, and 21 have had one or more cardiac catheterization from 6 to 18 months (mean, 1.2 years) after the initial operation. Reduction or resolution of resting mean left ventricular–to-aortic peak gradient in the early postoperative period from 81.8 ± 24.0 to 15.4 ± 8.9 mm Hg was demonstrated (p < 0.001). Overall 25-year survival was 57%. Fourteen surviving patients (56%) have undergone subsequent procedures (n = 18) from 5 months to 16 years postoperatively (mean, 6.9 years) because they developed a recurrent left ventricular–to-aortic gradient of 58 ± 28 mm Hg (p < 0.002). One patient underwent heart transplantation. All other late survivors have normal left ventricular function as determined by serial echocardiography.
CONCLUSIONS: Apical aortic conduit is effective in relieving complex left ventricular outflow tract obstruction and improving left ventricular performance with acceptable short-term and midterm results, but late complications caused primarily by conduit tissue valve dysfunction are frequent in children. Since the early 1990s, the apical aortic conduit procedure has been largely replaced with the Ross or Ross-Konno procedure in our pediatric practice.
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Introduction |
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In cases of LVOTO not amenable to simple surgical valvotomy because of associated diffuse subvalvar or supravalvar stenosis, or because of annular hypoplasia, other surgical techniques have been used to allow for unobstructed egress of blood from the left ventricle. One such operation is the creation of a second outlet for the left ventricle by anastomosing a valved conduit from the left ventricular (LV) apex to the descending or ascending aorta. Such procedures were initially conceptualized as early as 1910 by Carrel [1], initially experimenting with a vein graft conduit interposed between the left ventricle and the thoracic aorta. By 1955, the technique was successfully applied in dogs [2]. Clinical series of apical aortic conduit (AAC) insertion began appearing in the late 1970s [3–9].
Between 1978 and 1993, we implanted 28 AACs in children. We continue to implant AACs in elderly adult patients with a porcelain ascending aorta, prior healed sternal wound infections, or relative contraindications to cardiopulmonary bypass in whom relief of critical LVOTO is indicated. In 1993, we adopted the Ross and Ross-Konno procedures for children with complex LVOTO. The autologous pulmonary valve, placed in the aortic position, does not require anticoagulation, has growth potential, and can be combined with a Konno septoplasty for diffuse forms of subaortic obstruction.
The purpose of this study was to examine the long-term outcome of children who underwent insertion of an AAC for LVOTO and to examine the effects of the conduit and subsequent procedures on their LV function.
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Material and Methods |
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All patients had complex forms of AS that were not amenable to repair by established conventional methods at that time. The location of major obstruction was tunnel subvalvar AS in 15 and multilevel LVOTO in 13 patients. Among those patients with multilevel LVOTO, residual valvar and annular stenosis and subvalvular AS was present in 7, whereas supravalvar and subvalvar stenosis was observed in 4 and all three levels of LVOTO, in 2 patients. Seventeen of the 28 patients had undergone 26 prior operations to relieve left heart outflow obstruction. These operations included aortic valvotomy (n = 8), subvalvar resection of a membrane (n = 8), repair of supravalvar AS (n = 3), coarctation repair (n = 5), patch enlargement of hypoplastic transverse aortic arch (n = 1), and aortic valve replacement (n = 1).
Table 1 and Figure 1 show the age at operation, preoperative diagnosis, prior LVOTO procedures, conduit valve type, and follow-up on all 28 patients.
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Two of the 4 patients with moderate aortic incompetence underwent initial aortic valve replacement with small pericardial tissue prosthesis before AAC insertion. The other 2 had the AAC inserted despite the moderate AR, and postoperatively the AR subjectively seemed to be less. Eight patients had associated intracardiac lesions including single ventricle (n = 4), atrioventricular septal defect (n = 3), and tetralogy of Fallot (n = 1).
Operative Technique
The AAC was inserted using a median sternotomy or a fifth intercostal space left thoracotomy [4, 10]. If the left thoracotomy approach was used, then exposure with or without cannulation of the ipsilateral femoral artery and vein was undertaken on occasion in the event that partial cardiopulmonary bypass was indicated. A median sternotomy was used for insertion of the AAC only if coexisting cardiac lesions required repair at the time of conduit insertion.
When the left thoracotomy approach was used, the distal end of the Dacron valved conduit was sutured to the descending thoracic aorta with a partially occluding vascular clamp and pledgeted interrupted sutures. The patient was anticoagulated with heparin, and the partial occluding clamp was released to allow the distal end of the conduit to fill with blood up to the level of the conduit valve. The proximal end of the conduit, which always included a semirigid right-angled LV stent, was inserted after four pledged mattress sutures were placed about the proposed site of proximal conduit implantation, ie, the LV apex and the sewing ring on the LV stent. A circular piece of muscle was excised from the apex using a standard laboratory cork borer and a Foley catheter. Once the plug of muscle was removed from the apex of the left ventricle, the proximal end of the conduit was rapidly inserted. The four pledgeted sutures placed about the LV apex and through the sewing ring of the LV stent were tied, and additional pledgeted reinforcement mattress sutures were placed in the adjacent quadrants. Figure 2 illustrates the two anastomoses and the appearance of a completed AAC placement. A more detailed description of the surgical technique has been previously described [10]. The AAC valve was usually placed in the middle of the AAC. This location was chosen because it allowed clamping of the Dacron graft proximal and distal to the valve if valve replacement became necessary later.
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Patients with associated intracardiac lesions, before AAC insertion, underwent tetralogy of Fallot repair (n = 1) and complete atrioventricular communication repair after initial pulmonary artery banding (n = 1). Patients with single ventricle underwent pulmonary artery banding (n = 4) before AAC insertion, and one of them underwent completion Fontan operation after AAC implantation. Two patients with complete atrioventricular communication also underwent mitral valve replacement with mechanical prostheses before AAC insertion. One patient with severe AR and sinus of Valsalva fistula from aorta to the right atrium secondary to subacute bacterial endocarditis underwent initial aortic valve replacement with a xenograft valve 2 years before AAC insertion. Two other patients who had moderate AR underwent AAC insertion with concomitant aortic valve replacement with Ionescu-Shiley (Shiley Laboratories, Irvine, CA) pericardial prosthesis.
Statistical Analysis
SPSS statistical program for Windows version 10 (SPSS, Inc, Chicago, IL) was used to perform data analysis. Data are expressed as mean ± standard deviation and range. The Kaplan-Meier product limit method and Cox proportional hazards regression methods were used for actuarial survival analysis and analysis of freedom from reoperation. Multiple regression analysis was performed as conditional backward stepwise proportional hazards regression. Probability values of 0.05 or less were considered significant. An early death was defined as death in the hospital or within 30 days of discharge, whereas all other deaths were considered late.
Mean and peak aortic gradients were measured by Doppler echocardiography. The grade of aortic and conduit regurgitation was evaluated with color Doppler, using a five-grade (from 0 to 4; absent, trivial, mild, moderate, and severe), semiquantitative scale according to the ratio of the width of the regurgitant jet at its origin to the LV outflow tract diameter [11]. Aortic and conduit lesions were classified as predominant stenosis and predominant regurgitation according to the conclusive judgment of the operating surgeon after summarizing preoperative hemodynamic data and intraoperative findings.
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Results |
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The first child who died presented at age 17 years with acute bacterial endocarditis and severe AS and AR resulting in preoperative heart and liver failure. Preoperative hemodynamic instability necessitated aortic valve replacement with a small pericardial valve to eliminate the AR. Apical aortic conduit was inserted to relieve the residual AS. Both prostheses were implanted uneventfully, but the patient experienced coagulopathy and died 8 days postoperatively secondary to multiorgan system failure. No postmortem examination was performed.
The second death occurred in a 3-year-old patient with tunnel subaortic stenosis, critical valvar AS, and cardiogenic shock who had had multiple preoperative cardiac arrests. His operation was uneventful, but death occurred secondary to mechanical airway obstruction on the second postoperative day. Postmortem examination confirmed a normal functioning conduit.
The final early death occurred in a 2,300-g, 4-month-old infant with univentricular heart, transposition of the great arteries, interrupted aortic arch, and tunnel subvalvular AS. He underwent interrupted aortic arch repair with pulmonary artery banding at 6 weeks of age. At 4 months of age, the AAC was inserted using a 12-mm Hancock porcine valved conduit. The patient could not be weaned from ventilatory support and died 2 weeks postoperatively of sepsis secondary to pseudomonas pneumonia. At autopsy, thrombosis of two of three porcine valve cusps was observed. The 12-mm conduit was twice the size of the aorta, and we conjectured that cusp thrombosis was related to the inability of the small LV stroke volume to open all three cusps adequately.
Late Mortality
There were 9 late deaths (9 of 25; 36%). Six patients died of cardiac-related events that included respiratory arrests secondary to congestive heart failure (3 patients, at 6 months and 1 and 1.5 years), ventricular arrhythmia (1 patient at 1 year), dilated cardiomyopathy secondary to congestive heart failure (1 patient at 6 years), and cardiomyopathy 2 years after orthotopic heart transplant (1 patient). Two deaths were noncardiac related and included hemoptysis (1 patient at 4 years) and pulmonary hemorrhage (1 patient at 3 years postoperatively). The remaining late death occurred 7 years after AAC insertion and was of unknown cause. Overall survival estimated by the Kaplan-Meier method including early mortality was 75% at 1 years, 64% at 5 years, and 57% at 10, 20, and 25 years (Fig 3).
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Reoperations
Fifteen of 25 hospital survivors (60%) underwent 18 subsequent procedures 5 months to 16 years postoperatively (mean, 6.9 ± 4.6 years). The mean peak LV-to-aortic gradient at the time of the second operation was 58 ± 28 mm Hg (p = 0.002). Nine patients experienced significant conduit valve regurgitation, which was moderate in 7 patients and severe in 2. Overall freedom from reoperation was 83% at 1 year, 52% at 5 years, 23% at 10 years, and 5.6% at 15 years (Fig 4).
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Seven patients underwent conduit reintervention (n = 9; 2 patients had two concomitant procedures) as a result of porcine valve degeneration: replacement with St. Jude mechanical prosthesis (n = 3), and removal of AAC (n = 4) with concomitant Konno (n = 1) and Ross procedure (n = 1). The mean time from initial surgery to reoperation was 9.9 ± 3.8 years (range, 5 to 16 years). The predominant indication for reoperation was the presence of severe (5 of 7; 71%) or moderate (2 of 7; 29%) conduit valve regurgitation and conduit valve stenosis (n = 6) with mean peak gradient of 54 ± 21 mm Hg (range, 20 to 70 mm Hg). Only 1 patient still has a Hancock porcine valve 20 years after initial implantation. At last follow-up this patient has mild conduit regurgitation with a gradient of 15 mm Hg. The other 2 long-term AAC patients have had inserted mechanical (St. Jude Medical) valves.
ST. Jude medical valve conduit
Six children underwent AAC implantation with St. Jude mechanical valve (initial, n = 3; redo, n = 3). There was 1 late death at 3 years because of pulmonary hemorrhage, and 1 patient was lost to follow-up. Of the remaining 4 patients, 2 underwent reoperation at 9 and 13 years after mechanical AAC insertion because of mechanical conduit valve thrombosis. Both patients had removal of the AAC and underwent a Ross procedure. The remaining 2 patients still have an AAC with a St. Jude mechanical valve at 13 and 14 years after implantation and are doing well with minimal conduit gradient (5 and 8 mm Hg) and mild conduit regurgitation.
Aortic homograft valve conduit
Nine children underwent AAC insertion with AH (n = 10; initial, n = 9; redo, n = 1). We started using cryopreserved AHs after 1987 (when they became available at our institution) because they were available in sizes smaller than 12 mm and because we hoped they would be more durable than xenograft valves in children. One patient experienced a pseudoaneurysm of the LV anastomosis 9 months after initial implantation and required redo surgery with insertion of an AH conduit. There were 3 late deaths (6 months and 1 and 6 years after implantation) with intact AACs at autopsy. Six patients underwent reintervention (n = 7) as a result of AH valve degeneration: replacement with Hancock porcine prosthesis (n = 1), removal of AAC (n = 5) with concomitant Konno (n = 1) or Ross procedure (n = 1), and conduit patch angioplasty (n = 1). The mean time from initial surgery to first reoperation was 3.3 ± 2.3 years (range, 5 months to 7 years; p = 0.001). The predominant indication for reoperation was the presence of severe (2 of 6; 33%) or moderate (4 of 6; 67%) conduit regurgitation and conduit stenosis (n = 4) with a mean peak gradient of 76 ± 37 mm Hg (range, 50 to 130 mm Hg). Our experience with AH in the AAC was poor owing largely to the poor durability of the AH valve (3.3 ± 2.3 years) in children.
Late Follow-Up
Finally, at latest clinical evaluation (mean time, 10.7 ± 8.2 years; range, 6 months to 25 years), all survivors (n = 14) were in New York Heart Association functional class I or II leading normal or near-normal lives. Only 3 patients still have their original AAC (20, 24, and 25 years after initial implantation), but 2 have had the porcine valves replaced with a mechanical prosthesis 11 years after initial AAC insertion. All surviving patients including patients who had an AAC followed by a Ross-Konno procedure have normal indices of LV function as determined by ejection fraction and LV fractional shortening on serial follow-up echocardiograms.
The peak gradient in the remaining 3 patients with Ross procedure (1 of them with Ross-Konno) at 2, 8, and 9 years after surgery was 17.3 ± 5.9 mm Hg (range, 13 to 24 mm Hg), and AR was trivial in 2 patients and mild in 1. The mean peak gradient in the remaining 2 patients with Konno procedure at 5 and 9 years after surgery was 18 and 20 mm Hg, and AR was trivial in both patients.
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Comment |
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TopAbstractIntroductionMaterial and MethodsResultsCommentReferences |
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While AACs were being developed, other surgical approaches to deal with the hypoplastic aortic annulus and subvalvar area evolved in parallel. In the late 1970s, Konno and colleagues [13] and then Rastan and associates [14] published a method for enlarging the aortic annulus and subaortic area using an oblique incision in the aortic septum placed in the midportion of the two coronary ostia, and combined this with a vertical incision in the outflow tract of the right ventricle to join the septal incision. In so doing, enlargement of the aortic annulus for aortic valve replacement was possible, and the repair completed by patch reconstruction of both ventricular outflow tracts. We did not initially adopt the Konno-Rastan procedure because we thought it was very complex, and had a significant learning curve and mortality. It had a significant risk of complete heart block, required long periods of bypass and myocardial ischemia, and usually required a mechanical valve and anticoagulation.
Although multiple studies have demonstrated good early results using AACs, the incidence of late problems associated with long-term durability of the conduit valve has been appreciable. The reported late complications of AACs are LV pseudoaneurysm, erosion of the conduit into the esophagus or stomach when placed to the abdominal aorta, systemic emboli, and tissue valve dysfunction [15–22]. An LV pseudoaneurysm was seen in one of our patients. The risk of this complication has been reduced by use of a cloth-covered and lined LV stent and by attaching the LV stent to the patients' pericardium after insertion of the AAC. Systemic emboli have not been encountered in our patients, as was reported by Stansel and associates [19], and have not been encountered in other series. If systemic emboli were to occur they would very likely go below the diaphragm inasmuch as flow in the AAC rarely goes proximal to the left subclavian artery. Flow to the other aortic arch vessels is antegrade through the native aortic valve. Erosion of the conduit into the esophagus or an abdominal viscus [21] has not been encountered in our series. This complication could be prevented by placing omentum over the AAC in the retroperitoneum, as suggested by Ergin and coworkers [20], or placing the entire conduit in the left chest, which is our strong preference.
The major drawback of currently available AACs appears to be the limited durability of the porcine and AH valves in children. Conduit failure secondary to early bioprosthetic conduit valve degeneration and calcification has been previously identified as the major late complication of bioprosthetic valves in children. This fact is demonstrated by our study. Conduit valve failure occurred in 15 of the 25 children who survived initial placement. Several of our patients had an AAC valve change by means of a repeat left thoracotomy. Valve replacement was accomplished by clamping the graft on both sides of the valve. Bypass was not necessary in any patients. In patients who underwent a subsequent direct treatment of their LVOTO, the AAC was ligated and left in place.
High early and late mortality rates after conduit placement were observed by DiDonato and colleagues [7] and Norwood and associates [22] after conduit placement in children younger than 2 years of age. They attributed the poor outcome in these young children to congenital maldevelopment of the left ventricle associated with complex left-sided obstruction. Early conduit failure secondary to conduit valve stenosis or regurgitation was more prevalent in their younger group as well, particularly in infants younger than 1 year of age at conduit placement. Those patients undergoing conduit placement after 6 years of age had longer conduit durability, but conduit bioprosthetic valve failure eventually led to reoperation. Durability of the porcine xenograft valve in older children and adults is much better, and we have a few older children in whom the xenograft valve functioned well for 15 to 20 years.
Use of a more durable mechanical valve in the conduit is possible but requires warfarin sodium anticoagulation, which is not attractive in children. We have used mechanical valves in selected patients (n = 6). Unlike aortoventriculoplasty, the extracardiac location of the valve in AACs makes the apical aortic approach ideal for reoperation on malfunctioning prosthetic valves without bypass and permits a delayed primary attack on the LVOTO. Two of our patients still have their original AAC, 24 and 25 years after initial implantation, but both have had the porcine valve replaced with a mechanical prosthesis 13 and 14 years after initial AAC insertion.
Since the early 1990s the AAC procedure has been largely replaced with the Ross or Ross-Konno procedures in our pediatric practice. Patients with single ventricle and LVOTO (3 in this series) are currently better-served with a Damus-Kaye-Stansel procedure. We currently would only consider using an AAC in a child if there were serious reservations about doing a repeat sternotomy (ie, prior healed mediastinitis). The AAC procedure with a porcine xenograft valve continues to have a role in older adult patients with critical AS with or without mild AR in whom a direct approach through a median sternotomy is unattractive (ie, calcified eggshell ascending aorta, prior sternal wound infection, or multiple patent arterial or venous bypass grafts). The porcine xenograft in these patients has a durability of more than 10 years, and the procedure is performed routinely without cardiopulmonary bypass. A routine preoperative assessment of lower thoracic aorta by computed tomographic scan is performed to assure a safe location for the distal conduit anastomosis in these older patients. Efforts are currently under way to develop instrumentation to further simplify insertion of the AAC through a limited left thoracotomy and without bypass in the older patient population. The off-pump apical aortic approach to the LVOTO may compete favorably with techniques designed to percutaneously dilate and replace the stenotic native aortic valve in poor-risk adults, which are currently under investigation.
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References |
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  J. L. Herrmann, M. Ruzmetov, M. D. Rodefeld, M. H. Hoyer, and J. W. Brown Simultaneous apicoaortic conduit placement and mitral valve replacement in an adolescent with porcelain aorta, aortic stenosis, and mitral stenosis. Ann. Thorac. Surg., September 1, 2009; 88(3): 998 - 1000. [Abstract] [Full Text] [PDF]
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 T. P. Graham Jr The Year in Congenital Heart Disease J. Am. Coll. Cardiol., June 20, 2006; 47(12): 2545 - 2553. [Full Text] [PDF]
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