The pulmonary valve is the most common heart valve

Transcription

1 Biologic versus Mechanical Valve Replacement of the Pulmonary Valve After Multiple Reconstructions of the RVOT Tract S. Adil Husain, MD, and John Brown, MD Indiana University School of Medicine, Department of Surgery, Section of Cardiothoracic Surgery, Indianapolis, IN. Address reprint requests to: John J. Brown, MD, Indiana University School of Medicine, Department of Surgery, Section of Cardiothoracic Surgery, Indianapolis, IN Presented as part of the Controversies in Cardiothoracic Surgery Session of the 86th Annual Meeting of the American Association for Thoracic Surgery, Philadelphia, Pennsylvania, April 29 May 3, The pulmonary valve is the most common heart valve repaired and replaced in the treatment of congenital heart disease. Valve-bearing extracardiac conduits from the pulmonary ventricle to the pulmonary artery have allowed for the surgical treatment of many complex congenital defects. The surgical controversy for reconstruction of the right ventricular outflow tract (RVOT) for the past 30 years has been primarily focused on which biologic valve to use when valve insertion is indicated. Replacement of the pulmonary valve with a mechanical valve has recently been advocated for a subset of older children and adults rather than using a biologic substitute. In the discussion to follow we hope to convince the reader that continued use of a biologic pulmonary valve is indicated in all but a handful of older patients who require anticoagulation for other reasons. Aortic and later pulmonary homografts (PH) were the first valved conduits to be introduced to treat complex congenital heart disease. Until recently, PH have remained the most frequent choice for RVOT reconstruction in infants and children when a conduit was required. At our institution more than 500 RVOT reconstructions using a valve of various types have been performed in children in comparison to 150 aortic valve replacements, 75 mitral valve replacements, and 15 tricuspid valve replacements. More specifically, the number of pulmonary valve replacements (PVRs) in children has increased in the last 13 years due to pulmonary autograft replacement of the aortic valve (n 90) as well as the mitral valve (n 8), employing Ross techniques. 1,2 These left heart valve replacements require a pulmonary valve conduit to replace the pulmonary autograft. During the past 30 years of pulmonary valve replacement at our institution, only three mechanical valves have been implanted in the pulmonary position in adult patients who already had other mechanical valves in the aortic or mitral positions. The data support our heavy bias against mechanical valves in the pulmonary position largely due to the need for lifelong anticoagulation, risks of thromboemboli, and the demonstrated durability of xenografts in the tricuspid and pulmonary positions. Perhaps the largest series to date evaluating the options and outcomes of PVR was published by the Mayo Clinic group where late follow-up was reported on 1095 patients undergoing biologic conduit placement from the pulmonary ventricle to the pulmonary artery. 3 Dearani and colleagues very eloquently described not only the impressive extent of follow-up (37 years), but also the relative rarity of multiple re-interventions on the RVOT. More specifically, in their series which involved 1270 operative interventions, only 306 patients (24%) required one reoperation; 55 patients (4.3%) required two reoperations; 6 patients (0.47%) required three reoperations; and only 3 patients (0.23%) required four reoperations. This extensive experience confirms that multiple reoperations in this patient population are infrequent and that the use of biologic valves, especially xenografts, have an excellent record for durability. Homograft valve regurgitation, which is often moderate to severe, develops within 1 year of PH implantation in many children. Regurgitation is rarely an indication for homograft replacement in children, although early regurgitation is disappointing. Obstruction of the PH is the most common mode of failure and, as such, replacement is usually required within 7 years in most large series of non-ross PVRs. Our experience with PH shows a 10-year survival without re-intervention of 86 7%. 4 PHs are even more durable following Ross AVR because the Ross AVR is usually done in older children and adolescents. The PH used to replace the autograft is placed in the orthotopic position and can be easily oversized to make up for the expected shrinkage. The freedom of PH replacement in most large Ross AVR series, including our own, approaches 95% at 10 years. Outside the arena of biologic pulmonary valve replacements, transannular pulmonary incisions used to repair Tetralogy and ventricular septal defect (VSD) with pulmonary atresia lend themselves to the insertion of a monocusp pulmonary valve leaflet under an RVOT patch. We have had extensive experience with the Gore-Tex monocusp RVOT patch (W.L. Gore and Associates, Flagstaff, AZ) pulmonary valve reconstruction and find this type valve reconstruction /06/$-see front matter 2006 Elsevier Inc. All rights reserved. doi: /j.optechstcvs

2 208 S. A. Husain and J. Brown Figure 1 Pulmonary arteriotomy.

3 Biologic versus mechanical valve replacement of the pulmonary valve 209 Figure 2 Stay sutures placed to display size of pulmonary valve annulus. Figure 3 Sizing of Gore-Tex monocusp valve based on annulus.

4 210 S. A. Husain and J. Brown Figure 4 Implantation of Gore-Tex monocusp valve.

5 Biologic versus mechanical valve replacement of the pulmonary valve 211 Figure 5 Gore-Tex monocusp valve following implantation. Figure 6 Gore-Tex closure of pulmonary arteriotomy.

6 212 S. A. Husain and J. Brown Figure 7 Sequence of implantation technique for Gore-Tex monocusp.

7 Biologic versus mechanical valve replacement of the pulmonary valve 213 Figure 8 Contegra conduit. Figure 9 Contegra bovine jugular vein with valve displayed.

8 214 S. A. Husain and J. Brown Table 1 Outcomes of Mechanical Conduits in the Pulmonary Position Authors/Country, Year of Publication No. of Patients Age (mean) Valve Type Mortality Thromboembolism Comments PRO Rosti/Italy, years 6-One-leaflet 0 No 6.4 years follow-up 2-Bileaflet Haas/Netherlands, years All bileaflet 0 No 2.9 years follow-up 2005 Dearani/Mayo-US, 9 17 Adults???? No 8.3 years follow-up 2005 CON Ilbawi/Chicago-US, ?? All bileaflet 0 No At 2 years 37% had valve dysfunction Miyamura/Japan, 10 5?? All bileaflet Fleming/Omaha, Kiyota/Japan, ?? All bileaflet 0 3 At 3.5 years 3 patients were reoperated on 11?? All bileaflet of 11 patients were reoperated on more durable than a PH in most non-ross patients. Implantation techniques for the Gore-Tex monocusp RVOT patch pulmonary valve reconstruction are described (Figs. 1-7). The more recently introduced Contegra, bovine jugular venous valved conduit [an Humanitarian Device Exemption (HDE) study device] (Medtronic Inc., Minneapolis, MN), shows considerable promise as a PVR in infants, small children, and in a wide range of older children (Figs. 8, 9). It has outperformed PH in non-ross PVR patients at our institution. It is available in sizes from 12 to 22 mm, does not require anticoagulation, does not shrink, and overall retains valve competence in a high percentage of patients. Seventy patients have undergone Contegra-valved conduit RVOT reconstruction at our institution since One conduit has been explanted 2[1\2] years postoperatively because of a RV pseudoaneurysm. Seven patients have required catheter reintervention to relieve stenosis beyond the distal anastomosis of the conduit to the pulmonary artery bifurcation. In these patients, the interval to re-intervention was a mean of months. The projected price of the Contegra valve is approximately one-half that of some PHs in the United States. With short-term freedom from dysfunction being similar, and the economic advantages presented, the Contegra valve appears to be an attractive option to PH in PVR and RVOT reconstruction. Longer follow-up studies with a large number of patients will be required to see if this trend continues. 5 When comparing the extensive and thorough literature on biologic options for pulmonary valve replacement, data available on outcomes when employing a mechanical conduit or valve in the pulmonary position are sparse (Table 1). Overall, placement of mechanical valves in the pulmonary position has been reported in fewer than 90 patients with very inconsistent results. 6 Ilbawi and coworkers have published an experience with 16 mechanical valves in the pulmonary position. Six of the 16 (37%) patients developed prosthesis dysfunction 1 to 6 months after insertion. Actuarial survival for these patients at 2 years was only 70%. 7 Hass and coworkers have more recently published an experience with 14 mechanical valve conduits in the pulmonary position. At follow-up (11 to 63 months) all but two patients had normal right ventricular function with no evidence of valve failure. All patients were maintained on aggressive anticoagulation to achieve an international normalized ratio of 3.0 to Tilting disc mechanical valves appear to be less thrombogenic than their bileaflet counterparts. 6 The few publications report small patient populations, overall short-term follow-up, and a general consensus that mechanical options should only be employed in a highly selective subset of patients requiring PVR (Table 1). More specifically, patients who are of older age, those with multiple previous operative interventions associated with complications, and those with familial support, which is congruent with anticoagulation compliance, may form a very small cohort of patients in whom this option is advisable. The complication of cardiac laceration and bleeding from redo sternotomy can be minimized by closing the pericardium at the first and subsequent sternotomies with Gore-Tex membrane. The complication of air emboli to the systemic circulation during PVR can be prevented by electively closing all atrial and ventricular shunts. The controversy over biologic versus mechanical valve replacement of the pulmonary valve, even in the case of multiple interventions on the RVOT, is unbalanced in favor of biologic substitutes. Perhaps the most well-published proponent of biological options is my opponent in this debate, Dr. Dearani. Dearani and colleagues experience at the Mayo Clinic as well as that of our institution are extensive in quantity of patients and overall good outcomes in patients with biologic PVR. The misconception that the patient population that requires multiple re-interventions (more than two) after initial PVR is large but it is less than 5%. The subset of this group who would be candidates for mechanical PVR would be less than 1 to 2%. The proven durability PH and xenografts in older children and adults and the promising durability of Gore-Tex monocusp and Contegra conduits outweigh the potential advantages of mechanical valves, which will require lifelong

9 Biologic versus mechanical valve replacement of the pulmonary valve 215 anticoagulation. Mechanical valves in the pulmonary position should be reserved for adult patients who require coumadin anticoagulation for other reasons. References 1. Brown JW, Ruzmetov M, Rodefeld MD, et al: Right ventricular outflow tract reconstruction with an allograft conduit in non-ross patients: risk factors for homograft dysfunction and failure. Ann Thorac Surg 80: , Brown JW, Ruzmetov M, Rodefeld MD, et al: Mitral valve replacement with Ross II technique: initial experience. Ann Thorac Surg 81: , Dearani JA, Danielson GK, Puga FJ, et al: Late follow-up of 1095 patients undergoing operation for complex congenital heart disease utilizing pulmonary ventricle to pulmonary artery conduits. Ann Thorac Surg 75: , Yemets IM, Williams WG, Webb GD, et al: Pulmonary valve replacement late after repair of Tetralogy of Fallot. Ann Thorac Surg 64: , Brown JW, Ruzmetov M, Rodefeld MD, et al: Valved bovine jugular vein conduits for right ventricular outflow tract reconstruction in children: an attractive alternative to pulmonary homograft. Ann Thorac Surg 2006 (in press) 6. Rosti L, Murzi B, Colli AM, et al: Pulmonary valve replacement: a role for mechanical prosthesis? Ann Thorac Surg 65: , Ilbawi MN, Lockhart CG, Idriss FS, et al: Experience with St. Jude mechanical valve prosthesis in children. A word of caution regarding right sided placement. J Thorac Cardiovasc Surg 93:73-79, Hass F, Schreiber C, Horer J, et al: Is there a role for mechanical valved conduits in the pulmonary position? Ann Thorac Surg 79: , Dearani JA: Invited commentary. Ann Thorac Surg 79: , Miyamura H, Kanazawa H, Hayashi J, et al: Thrombosed St. Jude Medical valve prosthesis in the right side of the heart in patients with tetralogy of Fallot. J Thorac Cardiovasc Surg 94: , Fleming WH, Sarafian LB, Moulton AL, et al: Valve replacement in the right side of the heart in children: long-term follow-up. Ann Thorac Surg 48: , Kiyota Y, Shiroyama T, Akamatsu T, et al: In vitro closing behavior of the St. Jude Medical heart valve in the pulmonary position: valve incompetence originating in the prosthesis itself. J Thorac Cardiovasc Surg 104: , 1992