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Mechanical Prostheses for Right Ventricular Outflow Tract Reconstruction: A Systematic Review and Meta-Analysis Ben Dunne, MRCS, Alex Xiao, PhD Biostat, Edward Litton, FCICM, and David Andrews, FRACS The Western Australian Cardiothoracic Research and Audit Group (WA CRAG), Perth; Department of Cardiothoracic Surgery, Royal Perth Hospital, Perth; and Intensive Care Unit, Fiona Stanley Hospital, Perth and School of Medicine and Pharmacology, University of Western Australia, Perth, Western Australia
It remains unclear as to whether mechanical valves have a role in pulmonary valve replacement. A systematic review and meta-analysis was performed to answer this question. Nineteen observational studies, including 299 pediatric and adult patients with a mean follow-up of 73 months, were analyzed. Nonstructural valve deterioration and valve thrombosis occurred in 1.5% and 2.2% of patients, respectively. Surgical reintervention was required
in 0.9% of cases and thrombolysis was required in 0.5%. Mechanical valves in the pulmonary position are associated with a low incidence of valve deterioration and thrombosis, as well as freedom from reoperation and thrombolysis.
P
primarily in terms of risk for thrombosis, nonstructural valve dysfunction (NSVD), and resternotomy.
Address correspondence to Dr Dunne, Department of Cardiothoracic Surgery, Royal Perth Hospital, Perth, Western Australia, WA 6000; e-mail: [email protected].
Ó 2015 by The Society of Thoracic Surgeons Published by Elsevier
Material and Methods A review of available literature was undertaken by online searches of the major clinical databases: Medline, PubMed, Embase, Cochrane database, Google Scholar. The search terms used were “Mechanical” or “TiltingDisc” or “Bileaflet” or “St. Jude” and “Pulmonary Valve” or “Right Ventricular Outflow Tract”. The search years included ranged from 1960 to 2013. Bibliographies, from included papers, were assessed for suitable references in an attempt to avoid missing potentially useful material. All papers presenting original data on mechanical valves in the pulmonary position were included. Review articles or opinion pieces were searched for useful references but not included in data analysis. All papers deemed suitable for inclusion on the above criteria were reviewed separately by 2 authors (B.D. and D.A.) to ensure suitability. Level of evidence for each study was recorded. Data were extracted from the studies and pooled to produce results reflective of the total published experience with mechanical valves in the pulmonary position. The primary outcomes of interest were rates of thrombosis, nonstructural valve dysfunction (NSVD), and surgical reintervention. Secondary outcomes of interest included rates of thrombolysis, severe bleeding, SVD, and New York Heart Association (NYHA) class. We defined a priori a subgroup including only series that mandated warfarin therapy postoperatively. Two statistical models, namely fixed effects and random 0003-4975/$36.00 http://dx.doi.org/10.1016/j.athoracsur.2014.11.058
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ulmonary valve replacement (PVR) or right ventricular outflow tract reconstruction (RVOTR) is the most common valve replacement and repair procedure performed in the Society of Thoracic Surgeons (STS) Congenital database, comprising 16% of procedures performed in the adult congenital population [1]. There is a growing population of children surviving well into adulthood with repaired congenital heart disease and the number of PVR and RVOTR procedures required will grow with this population. Since Ross and Somerville performed the first RVOTR using an aortic homograft in 1966 [2] the search for the optimal conduit choice has been the subject of much debate. While a cryopreserved homograft is the gold standard, calcification and homograft failure remain an issue, with only 40% to 75% of homografts remaining free from structural valve deterioration (SVD) at 10 years in the congenital population [3, 4]. Alternative bioprostheses face similar longevity problems [5, 6]. Although mechanical valves have been the gold standard for left-sided valve replacement for decades, with a reduced risk of resternotomy for conduit replacement, concerns regarding increased rates of thrombosis in pulmonary mechanical valves have led to low use among the majority of congenital surgeons [1]. The aim of this study was to systematically review all primary publications describing the outcomes associated with using mechanical valves, compared with bioprosthetic and homografts in the pulmonary position,
(Ann Thorac Surg 2015;99:1841–7) Ó 2015 by The Society of Thoracic Surgeons
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STS/AATS/EACTS [The Society of Thoracic Surgeon/ American Association for Thoracic Surgery/European Association for Cardio-Thoracic Surgery] report. Anticoagulant related bleeding events were graded as per the Global Use of Strategies to Open Occluded Arteries (GUSTO) scale. Severe or life threatening bleeding was defined as intracranial bleeding or bleeding causing hemodynamic compromise. Moderate bleeding was defined as bleeding requiring transfusion. Mild bleeding was bleeding not requiring transfusion. Inadequate anticoagulation at time of valve thrombosis was defined as whether the paper in question reported a subtherapeutic international normalized ratio (INR) at time of diagnosis of valve thrombosis, a history of noncompliance with warfarin therapy, or if that study did not mandate warfarin anticoagulation for all their mechanical pulmonary valve recipients. A search for comparative series of alternative bioprostheses and homografts was also performed to allow comparison with the results of our meta-analysis. Series including valves of diameter less than 19 mm were excluded as 19 mm is the smallest available mechanical valve and so comparison with smaller bioprostheses would be invalid.
Fig 1. Flow diagram of search strategy.
effects models, were used depending on study heterogeneity. Fixed effects models were used if the between study variance was less than 0, while a random effects model was used where the between study variance was larger than 0. The SVD, no NSVD, and valve thrombosis were defined by Akins and colleagues [7] in their joint
Results A total of 1,434 records were initially retrieved with the search strategy described above. After removing duplicates 948 studies remained. One hundred fifty-six were retrieved after initial review of the titles and abstracts. Of these, only 19 papers included original clinical data on
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Table 1. Characteristics of Included Studies Author [Ref]
Year
Shin [15] Dos [16] Ovcina [17] Stulak [13] Deorsola [18] Horer [14] Waterbolk [19] Reiss [20] Haas [21] Dearani [22] Iscan [12] Nurozler [9] Rosti [23] Fiane [24] Kawachi [25] Fleming [11] Miyamura [26] Goor [27] Cartmill [10] TOTAL
2013 2011 2011 2010 2010 2009 2006 2005 2005 2005 2004 2002 1998 1996 1991 1989 1987 1984 1974
ASA ¼ aspirin;
Level of Evidence
Trial Design Retrospective Retrospective Retrospective Retrospective Retrospective Retrospective Retrospective Retrospective Retrospective Retrospective Case Report Retrospective Retrospective Case Report Retrospective Retrospective Retrospective Retrospective Retrospective
case series case series case series case-control study case series case-control study case series case series case series case series case series case series case case case case case
series series series series series
INR ¼ international normalized ratio;
Level Level Level Level Level Level Level Level Level Level Level Level Level Level Level Level Level Level Level
4 4 4 3 4 3 4 4 4 4 4 4 4 4 4 4 4 4 4
Peds ¼ pediatrics.
No.
Mean F/U
37 22 24 54 4 19 27 37 14 17 1 5 8 1 18 2 5 7 7 299
25 91 32 26 131 69 66 72 35 99 180 170 77 120 60 96 24 17 8 73
Adult/Peds
Anticoagulation
Mix Adults Mix Mix Adults Adults Mix Mix Adults Adults Peds Mix Peds Adult Adults Peds Mix Mix Peds
INR 2–3 INR 2.5–3.5 INR 2.5–4 INR 2–3 Warfarin (?INR) INR 2–3 INR 2.5–4 INR 2.5–3.5 INR 3–4.5 INR 3–4 Nil ASA INR 2 Warfarin (?INR) Warfarin (?INR) ASAþpersantine Warfarin (?INR) Warfarin (?INR) Nil
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mechanical valves in the pulmonary position. Of the remaining 137, 136 were review articles or brief opinion pieces without original data. One paper describing a series of 9 patients with mechanical PVR and 6 mechanical tricuspid valve replacements (TVR) was excluded due to their results not being separated into PVR and TVR, precluding analysis of results for PVR alone [8]. A total of 19 papers were included in the review. No randomized trials were identified. Sixteen of these were retrospective case series, 2 were retrospective casecontrol series, and 1 was a case report (Fig 1). A total of 299 patients with a mean follow-up of 73 months were analyzed. Four papers described mechanical PVR in a purely pediatric population. Seven papers described PVR in a purely adult population. Eight papers were mixed pediatric and adult series. Two of the papers were retrospective case-control studies, the remaining 17 were retrospective series. The approach to anticoagulation was heterogenous. Four of the studies did not routinely prescribe warfarin anticoagulation for their mechanical pulmonary valves. A further 5 studies used warfarin but have not stated their target INR. The remaining 10 studies routinely used warfarin with target INR ranging between 2.0 and 3.0 and 3.0 to 4.5 (Table 1). No patients suffered structural valve deterioration. The NSVD occurred in 6 patients (mean incidence 1.5% [95% confidence interval (CI) 0% to 13.3%). Three cases were
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due to ingrowth of pannus on the valve. One case was due to muscular subvalvar obstruction. Two remaining cases were due to stenosis of the conduit portion of a valved-conduit; the valves themselves functioned well in these 2 cases. Four of these required surgical reintervention. The remaining 2 cases remained under observation as they were asymptomatic at time of publication. Valve thrombosis occurred at a mean of 2.2% (95% CI 0.2% to 8.4%). Of the 19 cases of valve thrombosis, 14 of these (74%) were inadequately anticoagulated as per our definition previously. Nine patients underwent thrombolysis; 4 of these were successful. Fourteen patients required surgical reintervention, 5 of these after failed thrombolysis. Four patients requiring thrombolysis (44%) and 5 patients requiring reoperation (36%) were from 4 small series (a total of 15 patients) [9–12] that did not use warfarin postoperatively. In total, surgical reintervention was required at a mean of 0.9% of cases (95% CI 0.7% to 5.3%) and thrombolysis was required at a mean of 0.5% (95% CI 0.4% to 8.7%). Major bleeding events (as per GUSTO scale), including those secondary to thrombolysis, occurred at a mean of 0.4% (95% CI 0% to 7.7%). Freedom from symptoms of heart failure (NYHA I/II) was 99.2% (93.9% to 100%). Excluding the 4 series that did not mandate warfarin therapy for mechanical valve recipients produces results more likely to parallel current practice. Indeed, the results
Table 2. Valve Outcomes No.
Shin [15] Dos [16] Ovcina [17] Stulak [13] Deorsola [18] Horer [14] Waterbolk [19] Reiss [20] Haas [21] Dearani [22] Iscana [12] Nurozlera [9] Rosti [23] Fiane [24] Kawachi [25] Fleminga [11] Miyamura [26] Goor [27] Cartmilla [10] TOTAL
37 22 24 54 4 19 27 37 14 17 1 5 8 1 8 2 5 7 7 299
Warfarin
284
a
Nonstructural Dysfunction
Thrombosis
Surgical Reintervention
Thrombolysis
Severe Bleeding
NYHA 1/2
1 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 3 0 1.5% (0–13.3) 0.2% (0.06%–0.5%)
2 3 1 0 0 1 0 3 0 0 0 4 0 0 2 2 1 0 0 2.2% (0.2–8.4) 0.6% (0.1%–2.9%)
2 3 0 0 0 2 1 2 0 0 0 3 0 0 1 2 0 0 0 0.9% (0.7–5.3) 0.4% (0%–2.4%)
2 NR NR 0 0 NR 0 1 0 0 0 3 0 0 1 1 1 0 0 0.5% (0.4–8.7) 0.2% (0.1%–0.7%)
2 0 0 1 0 0 1 NR 0 NR 0 0 0 0 1 0 1 0 0 0.4% (0–7.7) 0.1% (0%–1.5%)
NR 16 24 NR 4 NR 25 NR 13 NR 1 NR NR 1 NR NR NR 7 7 99.2% (93.9–100) NR
These studies did not use warfarin postoperatively.
NR ¼ not reported;
NYHA ¼ New York Heart Association.
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Author
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Age (Years) 19 14 19 NR 14 5 6 5 8 20 8 17 2 NR NR NR 2 5 24 6 NR NR 16 1 21
Anatomy TOF Pulmonary Atresia þ VSD TOF Ross TOF DORV TOF TOF TOF TOF TOF TOF TOF NR NR NR TOF TOF TOF TOF TOF NR TOF NR TGA, VSD, PS
Type of PVR Bileaflet Tilting disc Tilting disc Bileaflet Bileaflet Bileaflet Bileaflet Bileaflet Bileaflet Bileaflet Bileaflet Bileaflet Bileaflet NR Bileaflet Bileaflet Bileaflet Bileaflet Bileaflet Tilting disc Bileaflet Bileaflet Tilting disc Bileaflet Tilting disc
Adequate Anticoagulation
Valved Conduit
Mechanism of Failure
Reoperation
Thrombolysis
N N N Y Y Y Y Y Y N N N N Y Y Y N N Y Y Y Y Y Y Y
N N N Y Y Y Y N N N N N N N Y N N N NR NR N Y NR Y NR
N Y N Y N N N N N N N N N NR NR NR N N N NR Y N N Y Y
Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Subvalvar pannus Pannus Pannus Pannus Conduit stenosis Conduit stenosis
Y Y Y Y Y N Y Y Y Y N Y Y N N Y Y Y N N Y Y N Y N
N N N N N Y Y N Y N Y Y N NR Y N Y Y Y N N N N N N
PS ¼ pulmonary stenosis;
PVR ¼ pulmonary valve replacement;
TGA ¼ transposition of the great arteries;
TOF ¼ tetralogy of Ann Thorac Surg 2015;99:1841–7
DORV ¼ double outlet right ventricle; NR ¼ not reported; Fallot; VSD ¼ ventricular septal defect.
Warfarin
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Table 3. Valve Failures
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Table 4. Alternative Bioprostheses Bioprosthesis Homografts Bovine pericardial Contegra Edwards Prima Edwards porcine conduit Medtronic Freestyle Hancock II Melody Perimount Toronto SPV
Failure Rates at 3 Years [Ref]
Failure Rates at Time 5 Years [Ref]
Failure Rates at 10 Years [Ref]
12% [28]
40% [3] 11% [29] 20%–27% [30, 31]
25%–60% [3, 4] 22% [5]
4%–17% [34, 35]
50% [6]
11%–26% [35, 39]
20% [6]
20% [32] 0% [33] 7.1%–16.4% [12, 13] 2%–10% [36–38] 10.5% [40]
improved so that valve thrombosis occurred at a mean of 0.6% (95% CI 0.1% to 2.9%). Thrombolysis was required at a mean of 0.2% (95% CI 0.1% to 0.7%) and surgical reintervention was required in 0.4% (95% CI 0.2% to 2.4%). Severe bleeding was not increased when studies mandating warfarin therapy were analyzed alone, severe bleeding occurred at a mean of 0.1% (95% CI 0.0% to 1.5%) (Tables 2 and 3).
Alternatives
Comment To our knowledge, this is the largest systematic review and meta-analysis comparing mechanical and bioprosthetic PVR. Contrary to widely held belief, we found that mechanical PVR were associated with excellent outcomes with an incidence of thrombosis of 0.6% when studies that mandated warfarin therapy were analyzed, resulting in very low rates of both thrombolysis (0.2%)
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Two of the series reviewed and included in the above results were retrospective case-control series. Stulak and colleagues [13] retrospectively matched 54 mechanical pulmonary valves 1:2 with 108 unspecified bioprostheses. They showed a 100% versus 52% 10-year freedom from reoperation in favor of mechanical prostheses. There was a small, nonsignificant difference in 10year freedom from bleeding events (88% vs 96%, p ¼ 0.08). H€ orer and colleagues [14] matched 19 mechanical valves with 19 homografts. There were 2 reoperations in the mechanical group and 3 in the homograft group after 5 years; 1 thrombosed valve and 1 case of NSVD due to pannus in the mechanical group, and 3 cases of homograft stenosis. These matched series would suggest that mechanical valves are at least equivalent if not superior to bioprosthetic alternatives. A review of all available prosthetic options was also performed to allow comparison between the many available alternatives. There is a shortage of truly longterm data available; however, 5-year results are available for most bioprostheses. Across all bioprostheses, a 5-year failure rate of 10% to 40% exists, with failure rates at 10 years climbing to 25% to 60% (Table 4).
and surgical reintervention (0.4%) in these patients. Although little truly long-term data are available on mechanical valves in the pulmonary position, these 6-year results compare very well with existing 5-year data for alternative bioprostheses and homografts. Given the excellent longevity of mechanical valves on the left side of the heart, a sudden increase in valverelated complications at longer term follow-up would not be expected. However, further research is warranted to confirm the long-term safety of right-sided mechanical PVR. In selecting patients for mechanical PVR, the hazards of warfarin therapy and the vital importance of meticulous compliance bear consideration. Certain patient populations, especially those engaged in particularly active lifestyles or young women planning to have a family, are not suited to warfarin therapy and bioprosthetic valves remain the best option for these patients so long as they understand the likely need for further repeat procedures. A second downside to mechanical pulmonary valves is that, unlike bioprosthetic alternatives, they are not suitable for percutaneous replacement with the Melody valve, which has revolutionized treatment of failing pulmonary bioprostheses in recent years. Although longterm data on the Melody valve is awaited, and concerns around stent fracture remain, certainly it seems that percutaneous options will play an increasing role in the management of the RVOT in years to come. Our study has a number of limitations that bear consideration. First, the included studies were all observational in nature, thus the risk of confounding by selection or reporting bias cannot be excluded. A randomized, controlled trial of bioprosthetic versus mechanical PVR in this population however is unlikely to be viable due the length of follow-up required. Second, the overall number of patients included is relatively low. We did, however, use broad search terms and search multiple databases. The outcome data are relatively consistent across studies, suggesting that the results are generalizable. Finally, longterm follow-up (>10 years) is lacking, and this should be a focus for future registry data collection in order to determine the optimal valve replacement strategy. Mechanical pulmonary valve replacements or mechanical valves in Dacron conduits for RVOTR have long
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been regarded as prone to early thrombosis and failure that has been in stark contrast to their performance on the left side of the heart. However, these conclusions may have been based on early experiences with older generation mechanical valves and inadequate anticoagulation. This review of mechanical valves in the pulmonary position, especially when reviewing only those managed with full anticoagulation, has highlighted excellent rates of valve thrombosis (0.6%) and NSVD (0.2%) with a mean follow-up of over 6 years. These rates compare very well with homografts and currently available bioprostheses. Certainly, in patients with an existing indication for warfarin or numerous previous sternotomies, mechanical PVR is an attractive option. Even in the absence of an existing indication for warfarin, mechanical PVR can be considered a reasonable choice with good medium-term results.
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Mechanical Prostheses for Right Ventricular Outflow Tract Reconstruction: A Systematic Review and Meta-Analysis Ben Dunne, MRCS, Alex Xiao, PhD Biostat, Edward Litton, FCICM, and David Andrews, FRACS The Western Australian Cardiothoracic Research and Audit Group (WA CRAG), Perth; Department of Cardiothoracic Surgery, Royal Perth Hospital, Perth; and Intensive Care Unit, Fiona Stanley Hospital, Perth and School of Medicine and Pharmacology, University of Western Australia, Perth, Western Australia
It remains unclear as to whether mechanical valves have a role in pulmonary valve replacement. A systematic review and meta-analysis was performed to answer this question. Nineteen observational studies, including 299 pediatric and adult patients with a mean follow-up of 73 months, were analyzed. Nonstructural valve deterioration and valve thrombosis occurred in 1.5% and 2.2% of patients, respectively. Surgical reintervention was required
in 0.9% of cases and thrombolysis was required in 0.5%. Mechanical valves in the pulmonary position are associated with a low incidence of valve deterioration and thrombosis, as well as freedom from reoperation and thrombolysis.
P
primarily in terms of risk for thrombosis, nonstructural valve dysfunction (NSVD), and resternotomy.
Address correspondence to Dr Dunne, Department of Cardiothoracic Surgery, Royal Perth Hospital, Perth, Western Australia, WA 6000; e-mail: [email protected].
Ó 2015 by The Society of Thoracic Surgeons Published by Elsevier
Material and Methods A review of available literature was undertaken by online searches of the major clinical databases: Medline, PubMed, Embase, Cochrane database, Google Scholar. The search terms used were “Mechanical” or “TiltingDisc” or “Bileaflet” or “St. Jude” and “Pulmonary Valve” or “Right Ventricular Outflow Tract”. The search years included ranged from 1960 to 2013. Bibliographies, from included papers, were assessed for suitable references in an attempt to avoid missing potentially useful material. All papers presenting original data on mechanical valves in the pulmonary position were included. Review articles or opinion pieces were searched for useful references but not included in data analysis. All papers deemed suitable for inclusion on the above criteria were reviewed separately by 2 authors (B.D. and D.A.) to ensure suitability. Level of evidence for each study was recorded. Data were extracted from the studies and pooled to produce results reflective of the total published experience with mechanical valves in the pulmonary position. The primary outcomes of interest were rates of thrombosis, nonstructural valve dysfunction (NSVD), and surgical reintervention. Secondary outcomes of interest included rates of thrombolysis, severe bleeding, SVD, and New York Heart Association (NYHA) class. We defined a priori a subgroup including only series that mandated warfarin therapy postoperatively. Two statistical models, namely fixed effects and random 0003-4975/$36.00 http://dx.doi.org/10.1016/j.athoracsur.2014.11.058
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ulmonary valve replacement (PVR) or right ventricular outflow tract reconstruction (RVOTR) is the most common valve replacement and repair procedure performed in the Society of Thoracic Surgeons (STS) Congenital database, comprising 16% of procedures performed in the adult congenital population [1]. There is a growing population of children surviving well into adulthood with repaired congenital heart disease and the number of PVR and RVOTR procedures required will grow with this population. Since Ross and Somerville performed the first RVOTR using an aortic homograft in 1966 [2] the search for the optimal conduit choice has been the subject of much debate. While a cryopreserved homograft is the gold standard, calcification and homograft failure remain an issue, with only 40% to 75% of homografts remaining free from structural valve deterioration (SVD) at 10 years in the congenital population [3, 4]. Alternative bioprostheses face similar longevity problems [5, 6]. Although mechanical valves have been the gold standard for left-sided valve replacement for decades, with a reduced risk of resternotomy for conduit replacement, concerns regarding increased rates of thrombosis in pulmonary mechanical valves have led to low use among the majority of congenital surgeons [1]. The aim of this study was to systematically review all primary publications describing the outcomes associated with using mechanical valves, compared with bioprosthetic and homografts in the pulmonary position,
(Ann Thorac Surg 2015;99:1841–7) Ó 2015 by The Society of Thoracic Surgeons
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STS/AATS/EACTS [The Society of Thoracic Surgeon/ American Association for Thoracic Surgery/European Association for Cardio-Thoracic Surgery] report. Anticoagulant related bleeding events were graded as per the Global Use of Strategies to Open Occluded Arteries (GUSTO) scale. Severe or life threatening bleeding was defined as intracranial bleeding or bleeding causing hemodynamic compromise. Moderate bleeding was defined as bleeding requiring transfusion. Mild bleeding was bleeding not requiring transfusion. Inadequate anticoagulation at time of valve thrombosis was defined as whether the paper in question reported a subtherapeutic international normalized ratio (INR) at time of diagnosis of valve thrombosis, a history of noncompliance with warfarin therapy, or if that study did not mandate warfarin anticoagulation for all their mechanical pulmonary valve recipients. A search for comparative series of alternative bioprostheses and homografts was also performed to allow comparison with the results of our meta-analysis. Series including valves of diameter less than 19 mm were excluded as 19 mm is the smallest available mechanical valve and so comparison with smaller bioprostheses would be invalid.
Fig 1. Flow diagram of search strategy.
effects models, were used depending on study heterogeneity. Fixed effects models were used if the between study variance was less than 0, while a random effects model was used where the between study variance was larger than 0. The SVD, no NSVD, and valve thrombosis were defined by Akins and colleagues [7] in their joint
Results A total of 1,434 records were initially retrieved with the search strategy described above. After removing duplicates 948 studies remained. One hundred fifty-six were retrieved after initial review of the titles and abstracts. Of these, only 19 papers included original clinical data on
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Table 1. Characteristics of Included Studies Author [Ref]
Year
Shin [15] Dos [16] Ovcina [17] Stulak [13] Deorsola [18] Horer [14] Waterbolk [19] Reiss [20] Haas [21] Dearani [22] Iscan [12] Nurozler [9] Rosti [23] Fiane [24] Kawachi [25] Fleming [11] Miyamura [26] Goor [27] Cartmill [10] TOTAL
2013 2011 2011 2010 2010 2009 2006 2005 2005 2005 2004 2002 1998 1996 1991 1989 1987 1984 1974
ASA ¼ aspirin;
Level of Evidence
Trial Design Retrospective Retrospective Retrospective Retrospective Retrospective Retrospective Retrospective Retrospective Retrospective Retrospective Case Report Retrospective Retrospective Case Report Retrospective Retrospective Retrospective Retrospective Retrospective
case series case series case series case-control study case series case-control study case series case series case series case series case series case series case case case case case
series series series series series
INR ¼ international normalized ratio;
Level Level Level Level Level Level Level Level Level Level Level Level Level Level Level Level Level Level Level
4 4 4 3 4 3 4 4 4 4 4 4 4 4 4 4 4 4 4
Peds ¼ pediatrics.
No.
Mean F/U
37 22 24 54 4 19 27 37 14 17 1 5 8 1 18 2 5 7 7 299
25 91 32 26 131 69 66 72 35 99 180 170 77 120 60 96 24 17 8 73
Adult/Peds
Anticoagulation
Mix Adults Mix Mix Adults Adults Mix Mix Adults Adults Peds Mix Peds Adult Adults Peds Mix Mix Peds
INR 2–3 INR 2.5–3.5 INR 2.5–4 INR 2–3 Warfarin (?INR) INR 2–3 INR 2.5–4 INR 2.5–3.5 INR 3–4.5 INR 3–4 Nil ASA INR 2 Warfarin (?INR) Warfarin (?INR) ASAþpersantine Warfarin (?INR) Warfarin (?INR) Nil
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mechanical valves in the pulmonary position. Of the remaining 137, 136 were review articles or brief opinion pieces without original data. One paper describing a series of 9 patients with mechanical PVR and 6 mechanical tricuspid valve replacements (TVR) was excluded due to their results not being separated into PVR and TVR, precluding analysis of results for PVR alone [8]. A total of 19 papers were included in the review. No randomized trials were identified. Sixteen of these were retrospective case series, 2 were retrospective casecontrol series, and 1 was a case report (Fig 1). A total of 299 patients with a mean follow-up of 73 months were analyzed. Four papers described mechanical PVR in a purely pediatric population. Seven papers described PVR in a purely adult population. Eight papers were mixed pediatric and adult series. Two of the papers were retrospective case-control studies, the remaining 17 were retrospective series. The approach to anticoagulation was heterogenous. Four of the studies did not routinely prescribe warfarin anticoagulation for their mechanical pulmonary valves. A further 5 studies used warfarin but have not stated their target INR. The remaining 10 studies routinely used warfarin with target INR ranging between 2.0 and 3.0 and 3.0 to 4.5 (Table 1). No patients suffered structural valve deterioration. The NSVD occurred in 6 patients (mean incidence 1.5% [95% confidence interval (CI) 0% to 13.3%). Three cases were
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due to ingrowth of pannus on the valve. One case was due to muscular subvalvar obstruction. Two remaining cases were due to stenosis of the conduit portion of a valved-conduit; the valves themselves functioned well in these 2 cases. Four of these required surgical reintervention. The remaining 2 cases remained under observation as they were asymptomatic at time of publication. Valve thrombosis occurred at a mean of 2.2% (95% CI 0.2% to 8.4%). Of the 19 cases of valve thrombosis, 14 of these (74%) were inadequately anticoagulated as per our definition previously. Nine patients underwent thrombolysis; 4 of these were successful. Fourteen patients required surgical reintervention, 5 of these after failed thrombolysis. Four patients requiring thrombolysis (44%) and 5 patients requiring reoperation (36%) were from 4 small series (a total of 15 patients) [9–12] that did not use warfarin postoperatively. In total, surgical reintervention was required at a mean of 0.9% of cases (95% CI 0.7% to 5.3%) and thrombolysis was required at a mean of 0.5% (95% CI 0.4% to 8.7%). Major bleeding events (as per GUSTO scale), including those secondary to thrombolysis, occurred at a mean of 0.4% (95% CI 0% to 7.7%). Freedom from symptoms of heart failure (NYHA I/II) was 99.2% (93.9% to 100%). Excluding the 4 series that did not mandate warfarin therapy for mechanical valve recipients produces results more likely to parallel current practice. Indeed, the results
Table 2. Valve Outcomes No.
Shin [15] Dos [16] Ovcina [17] Stulak [13] Deorsola [18] Horer [14] Waterbolk [19] Reiss [20] Haas [21] Dearani [22] Iscana [12] Nurozlera [9] Rosti [23] Fiane [24] Kawachi [25] Fleminga [11] Miyamura [26] Goor [27] Cartmilla [10] TOTAL
37 22 24 54 4 19 27 37 14 17 1 5 8 1 8 2 5 7 7 299
Warfarin
284
a
Nonstructural Dysfunction
Thrombosis
Surgical Reintervention
Thrombolysis
Severe Bleeding
NYHA 1/2
1 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 0 3 0 1.5% (0–13.3) 0.2% (0.06%–0.5%)
2 3 1 0 0 1 0 3 0 0 0 4 0 0 2 2 1 0 0 2.2% (0.2–8.4) 0.6% (0.1%–2.9%)
2 3 0 0 0 2 1 2 0 0 0 3 0 0 1 2 0 0 0 0.9% (0.7–5.3) 0.4% (0%–2.4%)
2 NR NR 0 0 NR 0 1 0 0 0 3 0 0 1 1 1 0 0 0.5% (0.4–8.7) 0.2% (0.1%–0.7%)
2 0 0 1 0 0 1 NR 0 NR 0 0 0 0 1 0 1 0 0 0.4% (0–7.7) 0.1% (0%–1.5%)
NR 16 24 NR 4 NR 25 NR 13 NR 1 NR NR 1 NR NR NR 7 7 99.2% (93.9–100) NR
These studies did not use warfarin postoperatively.
NR ¼ not reported;
NYHA ¼ New York Heart Association.
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Author
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Age (Years) 19 14 19 NR 14 5 6 5 8 20 8 17 2 NR NR NR 2 5 24 6 NR NR 16 1 21
Anatomy TOF Pulmonary Atresia þ VSD TOF Ross TOF DORV TOF TOF TOF TOF TOF TOF TOF NR NR NR TOF TOF TOF TOF TOF NR TOF NR TGA, VSD, PS
Type of PVR Bileaflet Tilting disc Tilting disc Bileaflet Bileaflet Bileaflet Bileaflet Bileaflet Bileaflet Bileaflet Bileaflet Bileaflet Bileaflet NR Bileaflet Bileaflet Bileaflet Bileaflet Bileaflet Tilting disc Bileaflet Bileaflet Tilting disc Bileaflet Tilting disc
Adequate Anticoagulation
Valved Conduit
Mechanism of Failure
Reoperation
Thrombolysis
N N N Y Y Y Y Y Y N N N N Y Y Y N N Y Y Y Y Y Y Y
N N N Y Y Y Y N N N N N N N Y N N N NR NR N Y NR Y NR
N Y N Y N N N N N N N N N NR NR NR N N N NR Y N N Y Y
Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Thrombosis Subvalvar pannus Pannus Pannus Pannus Conduit stenosis Conduit stenosis
Y Y Y Y Y N Y Y Y Y N Y Y N N Y Y Y N N Y Y N Y N
N N N N N Y Y N Y N Y Y N NR Y N Y Y Y N N N N N N
PS ¼ pulmonary stenosis;
PVR ¼ pulmonary valve replacement;
TGA ¼ transposition of the great arteries;
TOF ¼ tetralogy of Ann Thorac Surg 2015;99:1841–7
DORV ¼ double outlet right ventricle; NR ¼ not reported; Fallot; VSD ¼ ventricular septal defect.
Warfarin
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Table 3. Valve Failures
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Table 4. Alternative Bioprostheses Bioprosthesis Homografts Bovine pericardial Contegra Edwards Prima Edwards porcine conduit Medtronic Freestyle Hancock II Melody Perimount Toronto SPV
Failure Rates at 3 Years [Ref]
Failure Rates at Time 5 Years [Ref]
Failure Rates at 10 Years [Ref]
12% [28]
40% [3] 11% [29] 20%–27% [30, 31]
25%–60% [3, 4] 22% [5]
4%–17% [34, 35]
50% [6]
11%–26% [35, 39]
20% [6]
20% [32] 0% [33] 7.1%–16.4% [12, 13] 2%–10% [36–38] 10.5% [40]
improved so that valve thrombosis occurred at a mean of 0.6% (95% CI 0.1% to 2.9%). Thrombolysis was required at a mean of 0.2% (95% CI 0.1% to 0.7%) and surgical reintervention was required in 0.4% (95% CI 0.2% to 2.4%). Severe bleeding was not increased when studies mandating warfarin therapy were analyzed alone, severe bleeding occurred at a mean of 0.1% (95% CI 0.0% to 1.5%) (Tables 2 and 3).
Alternatives
Comment To our knowledge, this is the largest systematic review and meta-analysis comparing mechanical and bioprosthetic PVR. Contrary to widely held belief, we found that mechanical PVR were associated with excellent outcomes with an incidence of thrombosis of 0.6% when studies that mandated warfarin therapy were analyzed, resulting in very low rates of both thrombolysis (0.2%)
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Two of the series reviewed and included in the above results were retrospective case-control series. Stulak and colleagues [13] retrospectively matched 54 mechanical pulmonary valves 1:2 with 108 unspecified bioprostheses. They showed a 100% versus 52% 10-year freedom from reoperation in favor of mechanical prostheses. There was a small, nonsignificant difference in 10year freedom from bleeding events (88% vs 96%, p ¼ 0.08). H€ orer and colleagues [14] matched 19 mechanical valves with 19 homografts. There were 2 reoperations in the mechanical group and 3 in the homograft group after 5 years; 1 thrombosed valve and 1 case of NSVD due to pannus in the mechanical group, and 3 cases of homograft stenosis. These matched series would suggest that mechanical valves are at least equivalent if not superior to bioprosthetic alternatives. A review of all available prosthetic options was also performed to allow comparison between the many available alternatives. There is a shortage of truly longterm data available; however, 5-year results are available for most bioprostheses. Across all bioprostheses, a 5-year failure rate of 10% to 40% exists, with failure rates at 10 years climbing to 25% to 60% (Table 4).
and surgical reintervention (0.4%) in these patients. Although little truly long-term data are available on mechanical valves in the pulmonary position, these 6-year results compare very well with existing 5-year data for alternative bioprostheses and homografts. Given the excellent longevity of mechanical valves on the left side of the heart, a sudden increase in valverelated complications at longer term follow-up would not be expected. However, further research is warranted to confirm the long-term safety of right-sided mechanical PVR. In selecting patients for mechanical PVR, the hazards of warfarin therapy and the vital importance of meticulous compliance bear consideration. Certain patient populations, especially those engaged in particularly active lifestyles or young women planning to have a family, are not suited to warfarin therapy and bioprosthetic valves remain the best option for these patients so long as they understand the likely need for further repeat procedures. A second downside to mechanical pulmonary valves is that, unlike bioprosthetic alternatives, they are not suitable for percutaneous replacement with the Melody valve, which has revolutionized treatment of failing pulmonary bioprostheses in recent years. Although longterm data on the Melody valve is awaited, and concerns around stent fracture remain, certainly it seems that percutaneous options will play an increasing role in the management of the RVOT in years to come. Our study has a number of limitations that bear consideration. First, the included studies were all observational in nature, thus the risk of confounding by selection or reporting bias cannot be excluded. A randomized, controlled trial of bioprosthetic versus mechanical PVR in this population however is unlikely to be viable due the length of follow-up required. Second, the overall number of patients included is relatively low. We did, however, use broad search terms and search multiple databases. The outcome data are relatively consistent across studies, suggesting that the results are generalizable. Finally, longterm follow-up (>10 years) is lacking, and this should be a focus for future registry data collection in order to determine the optimal valve replacement strategy. Mechanical pulmonary valve replacements or mechanical valves in Dacron conduits for RVOTR have long
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been regarded as prone to early thrombosis and failure that has been in stark contrast to their performance on the left side of the heart. However, these conclusions may have been based on early experiences with older generation mechanical valves and inadequate anticoagulation. This review of mechanical valves in the pulmonary position, especially when reviewing only those managed with full anticoagulation, has highlighted excellent rates of valve thrombosis (0.6%) and NSVD (0.2%) with a mean follow-up of over 6 years. These rates compare very well with homografts and currently available bioprostheses. Certainly, in patients with an existing indication for warfarin or numerous previous sternotomies, mechanical PVR is an attractive option. Even in the absence of an existing indication for warfarin, mechanical PVR can be considered a reasonable choice with good medium-term results.
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16. 17. 18. 19.
20.
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