Intermediate follow-up of right ventricular outflow tract reconstruction with allograft conduits

Long-term clinical outcome and echocardiographic function of homografts in the right ventricular outflow tract†

OBJECTIVES

Although homografts are often the preferred valve conduits for right ventricular outflow tract (RVOT) reconstruction, data on long-term homograft-related outcomes, durability and impact on quality of life (QoL) are scarce. The aim of this study was therefore to describe the long-term homograft function, clinical outcomes and QoL after RVOT reconstruction.

METHODS

We performed a single-centre retrospective analysis of all consecutive patients who underwent RVOT reconstruction with a homograft. Multiple subsequent allografts in the same patients were regarded as separate subjects. Valve-related events were analysed by Kaplan-Meier and Life Table methods. Serial echocardiographic measurements were analysed with mixed effects models. In addition, QoL was repeatedly assessed and compared with a matched general population.

RESULTS

In total, 701 consecutive homografts were implanted in 604 patients [59.6% males, mean age at operation 19.5 ± 15.2 (standard deviation)]. Hospital mortality was 3.3%. After 25 years follow-up, survival and freedom from valve replacement were 84 ± 4% and 56 ± 6%, respectively. Freedom from valve replacement after 15 years for patients under 1 year of age was 28 ± 14% years, for those between 1 and 18 years, 59 ± 8%, and for those older than 18 years, 82 ± 5%. The peak gradient increased predominantly in the first postoperative decade in infants and paediatric patients from 19 to 54 mmHg. In adults, the average gradient increased from 9 to 31 mmHg after 14 years. Compared to a gender- and age-matched Dutch population, patients reported lower vitality and general health but less bodily pain. Patients, in whom QoL was repeatedly assessed, reported lower scores on physical functioning and vitality after a 5-year follow-up period. However, we found no differences in any of the subscales in patients who underwent valve replacement during the 5-year interval.

CONCLUSIONS

Homografts are a durable valve alternative for RVOT reconstruction; in particular, adults show extensive freedom from valve replacement and report QoL comparable with healthy subjects. An online interactive application form created by our institution can be used to assess patient outcome after RVOT reconstruction with a homograft for different patient profiles.

Small-sized conduits in the right ventricular outflow tract in young children: bicuspidalized homografts are a good alternative to standard conduits

OBJECTIVES

Downsizing a homograft (HG) through bicuspidalization has been used for more than 2 decades to overcome the shortage of small-sized conduits for reconstruction of the right ventricular outflow tract (RVOT) in young children. Our goal was to investigate the durability of bicuspidalized HGs compared with other small HGs.

METHODS

A retrospective analysis of 93 conduits ≤20 mm, implanted over 23 years, was performed. The end-points were survival, structural valve degeneration and conduit replacement. The conduits comprised 40 pulmonary HGs, 12 aortic HGs, 17 bicuspidalized HGs and 24 xenografts.

RESULTS

The median age, mean conduit diameter and z-value at implantation were 1.4 (interquartile range 0.3-3) years, 16.5 ± 2.7 mm and 2.8 ± 1.3, respectively. Valve position was heterotopic in 59 patients and orthotopic in 34 patients. At a mean follow-up period of 7.6 ± 5.9 years, the hospital survival rate was 89%. Freedom from explant at 5 and 10 years was 83 ± 5% and 52 ± 6%, respectively. Freedom from structural valve degeneration was 79 ± 5% at 5 years and 47 ± 6% at 10 years [68 ± 8% for pulmonary HG, 42 ± 16% for bicuspidalized HG, 31 ± 15% for aortic HG and 20 ± 9% for xenografts (log rank P < 0.001)]. Multivariable analysis indicated an increased risk for structural valve degeneration with smaller conduit size (hazard ratio 0.79, 95% confidence interval 0.67-0.94; P < 0.008), extra-anatomic position (hazard ratio 2.71, 95% confidence interval 1.33-5.50; P = 0.006) and the use of xenografts compared with non-downsized pulmonary HGs (hazard ratio 4.90, 95% confidence interval 2.23-10.76; P < 0.001).

CONCLUSIONS

Appropriately sized pulmonary HGs remain the most durable option for a right ventricular outflow tract conduit in young children. However, when a small pulmonary HG is unavailable, bicuspidalization offers a valid alternative, preferable to xenograft conduits, at mid-term follow-up.

Tissue-Engineered Heart Valves: A Call for Mechanistic Studies

Heart valve disease carries a substantial risk of morbidity and mortality. Outcomes are significantly improved by valve replacement, but currently available mechanical and biological replacement valves are associated with complications of their own. Mechanical valves have a high rate of thromboembolism and require lifelong anticoagulation. Biological prosthetic valves have a much shorter lifespan, and they are prone to tearing and degradation. Both types of valves lack the capacity for growth, making them particularly problematic in pediatric patients. Tissue engineering has the potential to overcome these challenges by creating a neovalve composed of native tissue that is capable of growth and remodeling. The first tissue-engineered heart valve (TEHV) was created more than 20 years ago in an ovine model, and the technology has been advanced to clinical trials in the intervening decades. Some TEHVs have had clinical success, whereas others have failed, with structural degeneration resulting in patient deaths. The etiologies of these complications are poorly understood because much of the research in this field has been performed in large animals and humans, and, therefore, there are few studies of the mechanisms of neotissue formation. This review examines the need for a TEHV to treat pediatric patients with valve disease, the history of TEHVs, and a future that would benefit from extension of the reverse translational trend in this field to include small animal studies.

Multiply adjusted comparisons: A meta-analysis method to compare single-arm clinical-trial data to literature results regarding a competitor

Prospective randomized controlled trials are difficult to obtain if a promising new therapy has to be tested against seemingly obsolete alternatives. One method to address this problem is to compare the results of (multicentre) trials to literature results. However, previous treatment-era changes and population-dependent results complicate objective comparisons. The presented approach describes a method to objectify such comparisons in cases in which individual raw data regarding a new therapy have to be compared to summary results regarding a conventional alternative published in the literature. The chosen example is the introduction of bovine neck veins as a substitute for dysfunctional human pulmonary valves, and the conventional therapeutic alternative is pulmonary-artery homografts. Literature research, subgroup identification, filtering, endpoint remodelling, weighting and, if necessary, confidence-limit calculation yield adjusted comparisons. These individual comparisons are then aggregated, first by article and then over several articles (similar to meta-analyses), resulting in a differentiated panel of answers (Multiply Adjusted Comparisons). In situations in which extensive raw data regarding a new therapeutic alternative but no randomized controlled trials and no raw data from previous studies using the conventional therapeutic alternative are available, the proposed method identifies the best evidence and is by far superior to unadjusted direct comparisons or gut feelings.

How Long Can the Next Intervention Be Delayed after Balloon Dilatation of Homograft in the Pulmonary Position?

Background and Objectives

We investigated the effectiveness of balloon dilatation of homograft conduits in the pulmonary position in delaying surgical replacement.

Subjects and Methods

We reviewed the medical records of patients who underwent balloon dilatation of their homograft in the pulmonary position from 2001 to 2015. The pressure gradient and ratio of right ventricular pressure were measured before and after the procedure. The primary goal of this study was to evaluate the parameters associated with the interval to next surgical or catheter intervention.

Results

Twenty-eight balloon dilations were performed in 26 patients. The median ages of patients with homograft insertion and balloon dilatation were 20.3 months and 4.5 years, respectively. The origins of the homografts were the aorta (53.6%), pulmonary artery (32.1%), and femoral vein (14.3%). The median interval after conduit implantation was 26.7 months. The mean ratio of balloon to graft size was 0.87. The pressure gradient through the homograft and the ratio of right ventricle to aorta pressure were significantly improved after balloon dilatation (p<0.001). There were no adverse events during the procedure with the exception of one case of balloon rupture. The median interval to next intervention was 12.9 months. The median interval of freedom from re-intervention was 16.6 months. Cox proportional hazards analysis revealed that the interval of freedom from re-intervention differed only according to origin of the homograft (p=0.032), with the pulmonary artery having the longest interval of freedom from re-intervention (p=0.043).

Conclusion

Balloon dilatation of homografts in the pulmonary position can be safely performed, and homografts of the pulmonary artery are associated with a longer interval to re-intervention.

Pulmonary homograft muscle reduction to reduce the risk of homograft stenosis in the Ross procedure

OBJECTIVE

The Ross procedure has gained increasing interest as an attractive alternative for aortic valve replacement. Despite its advantages, there is a certain risk of structural valve deterioration, especially of the pulmonary homograft as a result of shrinkage and subsequent stenosis predominantly at the muscular annulus. Theoretically, reduction of homograft muscle tissue could reduce this risk.

METHODS

From February 1996 through December 2002, a total of 238 patients (mean age 44 +/- 13.2 years) underwent the Ross procedure with the subcoronary technique with follow-up investigations before discharge and after 12 and 24 months. To estimate the importance of homograft muscle reduction within our institution-specific risk factor scale for change of transhomograft pressure gradient with time, we performed a generalized estimating equation approach, which identified homograft muscle reduction, higher body surface area in male patients, younger patient age, smaller homograft diameter, blood transfusions, and follow-up time as independent risk factors demonstrating a high beta value (-2.8638) for muscle reduction. To find out whether muscle reduction influences transhomograft pressure gradient, we compared patients with (group A, n = 39) and without (group B, n = 199) muscle reduction. The other mentioned independent risk factors were not different between groups, except for blood transfusions (group A greater than B, P < .01), indicating a negative bias for group A.

RESULTS

The maximum pressure gradient across the homograft was lower in patients with muscle reduction before discharge (4.5 +/- 2.8 mm Hg group A vs 6.2 +/- 3.8 mm Hg group B, P = .004) and after 1 (9.3 +/- 5.8 vs 13.1 +/- 8.4 mm Hg, P = .028) and 2 years (10.8 +/- 7.6 vs 13.7 +/- 7.5 mm Hg, P = .013). No significant differences were found concerning homograft insufficiency.

CONCLUSIONS

We provide some evidence that transhomograft pressure gradient can be reduced significantly within the first 2 years after operation by homograft muscle reduction. Longer term follow-up is necessary to evaluate this promising operative technique further.

Pulmonary position cryopreserved homografts: Durability in pediatric Ross and non-Ross patients

OBJECTIVE

The purpose of this study was to evaluate the outcome and risk factors for implant failure in pediatric patients who underwent pulmonary position homograft placement for right ventricular outflow tract obstruction compared with conduit placement as a component of the Ross operation. Actuarial 5-year survivals for cryopreserved right ventricle-to-pulmonary artery homografts range from 55% to 94% at all ages. It is not known whether there is a difference in homograft durability when utilized for right ventricular outflow tract obstruction or as part of the Ross operation.

METHODS

The records of all pediatric patients receiving a right ventricle-to-pulmonary artery homograft from July 1989 through October 2003 were reviewed. Ninety-eight consecutive patients were studied (26 Ross, 72 non-Ross). In addition to Ross versus non-Ross comparisons, other potential risk factors for homograft failure analyzed included age at operation, follow-up time, type of surgery, and homograft type and size.

RESULTS

Ross and non-Ross patients were comparable in age at the time of the operation and follow-up time. Homograft failure rates were 12% and 51% for Ross and non-Ross patients, respectively. Freedom from reintervention was 93% in the Ross and 66% in the non-Ross group at 5 years (P = .019). On multivariate analysis, non-Ross operation and age less than 2 years were significant predictors of homograft failure.

CONCLUSIONS

1. Pediatric patients undergoing the Ross operation have longer homograft survival than pediatric patients treated for right ventricular outflow tract obstruction, independent of age. 2. Homografts placed in patients less than 2 years of age have shorter homograft survival.

Late follow-up of 1095 patients undergoing operation for complex congenital heart disease utilizing pulmonary ventricle to pulmonary artery conduits

BACKGROUND

Pulmonary ventricle (PV) to pulmonary artery (PA) conduits have made possible the correction of many complex congenital cardiac anomalies.

METHODS

Between April 1964 and January 2001, 1270 patients underwent operation with conduit placement from the PV to PA. The present study evaluates late outcome of 1095 patients (612 males, 483 females) having an operation before July 1992. Mean age was 9.6 +/- 8.2 years old. Diagnoses included pulmonary atresia/tetralogy of Fallot (459), transposition of the great arteries (TGA) (232), truncus arteriosus (193), double outlet right ventricle (DORV) (121), corrected TGA (49), septated univentricular heart (36), and other (5). A porcine-valved Dacron conduit was used in 730, homograft in 239, and non-valved conduit in 126.

RESULTS

Early mortality decreased from 23.5% prior to 1980 to 3.7% for the most recent decade. Mean follow-up was 10.9 years (maximum, 29 years). Actuarial survival for early survivors at 10 and 20 years was 77.0% +/- 1.5% and 59.5% +/- 2.6%. On univariate analysis, clinical and hemodynamic factors associated with late mortality were male gender, older age at operation, higher post-repair PV/systemic ventricle (SV) pressure ratio, higher distal PA pressure, and longer bypass time (p < or = 0.01 for all). On multivariate analysis, independent risk factors for late mortality were male gender, older age at operation, diagnosis of TGA, corrected TGA, truncus, or univentricular heart, and PV/SV pressure ratio > or = 0.72 (p < or = 0.03 for all). Freedom from reoperation for conduit failure at 10 and 20 years was 55.5% +/- 2.0% and 31.9% +/- 2.7%. On multivariate analysis, independent risk factors for conduit failure were homograft conduit, diagnosis of TGA, younger age at operation, and smaller conduit size (p < or = 0.007 for all). Reoperation for one conduit replacement was performed in 306 patients, two conduit replacements in 55 patients, three in 6 patients, and four in 3 patients. Overall early mortality for conduit replacement in this series was 4.9%; it was 1.7% for patients operated on from 1989 through 1992. At follow-up, 84% of survivors were in NYHA class I or II.

CONCLUSIONS

Operations that include conduit placement and replacement can be performed with low early mortality. Younger age at operation was associated with improved late survival. The diagnosis of TGA was associated with increased risk for conduit failure, and the durability of the homograft, in this series, was inferior to the porcine-valved Dacron conduit. Quality of life was excellent for most patients despite the need for reoperation.

Intermediate follow-up of a composite stentless porcine valved conduit of bovine pericardium in the pulmonary circulation

BACKGROUND

In the pediatric population, glutaraldehyde-preserved bovine pericardium conduit containing a stentless porcine valve has been proposed as an alternative to homografts for right ventricular outflow tract reconstruction.

METHODS

Between June 1996 and March 2000, a total of 55 patients, 20 with truncus arteriosus, 21 with pulmonary atresia with ventricular septal defect, and 14 with miscellaneous defects, received this conduit. Median age at implantation was 3.4 months (range, 3 days to 19 years), and 27 patients (50%) were less than 3 months old. Clinical outcome, echocardiographic data, and pathologic analysis were recorded. End points for conduit failure were conduit replacement or dilation. A mean follow-up of 27 months (range, 2 to 46 months) was available for 47 survivors.

RESULTS

Procedure for conduit obstruction was required in 13 patients. The most common procedure was operation, and all but 3 patients had an unsuccessful balloon angioplasty before reoperation. Actuarial freedom from conduit dilation or reoperation was 93.6% (95% confidence limits, 82% to 99%), 81.9% (95% confidence limits, 64% to 91%), 77.8% (95% confidence limits, 39% to 78%), and 64.3% (95% confidence limits, 26% to 73%) at 1, 2, 3, and 4 postoperative years, respectively. Univariate analysis identified small conduit size as a risk factor for conduit obstruction.

CONCLUSIONS

Although this new conduit was not free from progressive obstruction, our clinical results (easy to work and good valvular function) and the availability in small sizes encouraged us to use it as an alternative to small-size homografts when those were not available.

Extending the usable size range of homografts in the pulmonary circulation: outcome of bicuspid homografts

BACKGROUND

Small-sized homografts are often not available, making the use of surgically reduced cryopreserved homograft conduits appealing.

METHODS

From January 1993 to January 2000, 21 large homografts were size-reduced by excising one leaflet and were implanted in the pulmonary circulation. Valve function was compared with 21 children-matched for weight, homograft size, and year of operation-who received a standard homograft.

RESULTS

Implanted homograft size and patient weight were equivalent in both the bicuspid and standard groups. Median (range) in-hospital peak instantaneous echocardiographic gradient across the valve was 0 mm Hg (0 to 19) in the bicuspid group versus 0 mm Hg (0 to 17) in the standard group (p = 0.65). Median (range) in-hospital pulmonary insufficiency (scale of 0 to 4) was 2 (0 to 3) in the bicuspid group versus 1.5 (0 to 3) in the standard group (n = 10, p = 0.34). At a follow-up of 54+/-29 months there was no significant difference in conduit reinterventions between the groups.

CONCLUSIONS

Surgical creation of a bicuspid valve in the pulmonary circulation results in a functionally equivalent conduit compared with standard homograft as measured by early and midterm valve function.

The fate of small-diameter homografts in the pulmonary position

BACKGROUND

Limited durability is expected for small homograft valves that are used to correct congenital cardiac disease.

METHODS

All 76 homograft valves with an internal annulus diameter ranging from 8 to 13 mm that were implanted from 1987 through 2000 in the pulmonary position were retrospectively analyzed. In each case, homograft size was normalized to the patient's body surface area: z-value. For 93% (14 of 15) of the 8 to 9 mm grafts, z was less than 2. For 56% (5 of 9) of the 10 mm grafts and 98% (51 of 52) of the 11 to 13 mm allografts, z was greater than 2. Survival and freedom from complications were estimated by the Kaplan-Meier method. Homograft failure was defined as homograft replacement or late death; significant dysfunction, as homograft obstruction with an echo-Doppler gradient greater than 50 mm Hg or grade III or IV valvular insufficiency. The log-rank test was used to compare outcomes.

RESULTS

Seven patients died early after operation; three, late. Survival was 86.5% +/- 3.8% at 1 year and remained stable during the succeeding years. Freedom from failure for all homografts was 90.6% +/- 3.7%, 71.8% +/- 6.9%, and 61.8% +/- 9.0% at 1, 5, and 10 years, respectively. Corresponding freedom from significant dysfunction was 87.6% +/- 4.1%, 51.2% +/- 7.4%, and 10.1% +/- 8.3%. The smaller homografts (z less than 2) failed and deteriorated faster (p < 0.0001): only 32.1% +/- 13.0% were still functioning at 24 months. The larger grafts (z at least 2) retained function for the first 4 years, and 73.7% +/- 10.4% had not yet failed at 10 years.

CONCLUSIONS

Smaller (z less than 2) homografts (the great majority of 8 to 9 mm grafts) have to be replaced early, usually within 2 years of implantation. Larger (z at least 2) grafts (nearly all 11 to 13 mm grafts) show remarkable durability and are suitable valved conduits for establishing right ventricle to pulmonary artery continuity in neonates and young infants.

Reoperative homograft right ventricular outflow tract reconstruction

BACKGROUND

Homografts are implanted in the right ventricular outflow tract (RVOT) of children, with the knowledge that reoperation might be required. We reviewed 14 years of homograft RVOT reconstruction to assess the feasibility of homograft replacement and to determine risk factors for homograft survival.

METHODS

From February 1985 through March 1999, 223 children (age 5 days to 16.9 years) underwent primary RVOT reconstruction with an aortic or pulmonary homograft. Of these, 35 patients underwent homograft explant at the implanting hospital with insertion of a second homograft from 2 months to 13.3 years after the first implantation. The primary operation and reoperation patient groups were compared with regard to incidence of early death, late death, homograft-related intervention without explant, and homograft explant.

RESULTS

Actuarial survival and event-free curves for initial and replacement homografts were not significantly different. Univariable analysis was performed for the following risk factors: weight (p < 0.0001), age (p < 0.003), homograft diameter (p < 0.0001), homograft type (p < 0.01), surgery date (not significant [NS]), gender (NS), Blood Group match (NS), and type of distal anastomosis (NS). Multivariable analysis of significant univariable risks revealed small homograft diameter to be a significant risk factor (p < 0.001) for replacement.

CONCLUSIONS

The RVOT homografts eventually require replacement. Patient and homograft survival for replacement homografts is similar to primary homografts. Reoperative homograft RVOT reconstruction is possible, with reasonably low morbidity and mortality.

Shelhigh No-React porcine pulmonic valve conduit: a new alternative to the homograft

BACKGROUND

The Shelhigh No-React pulmonic valve conduit is a new porcine conduit that is glutaraldehyde-treated and detoxified using a proprietary heparin process. In our institution it has been implanted in 25 patients. The aim of this present contribution is to evaluate the short-term follow-up after its implantation.

METHODS

From November 1997 to August 1999, 25 patients (mean age, 20.2 years; range, 0.6 to 28.3 years) were operated on using this conduit. Seventeen patients underwent a Ross procedure for aortic valve disease, with the conduits implanted in anatomic position; 6 patients underwent right ventricular outflow tract reconstruction; 2 patients underwent the Rastelli operation. The follow-up was complete. Preoperative and postoperative two-dimensional echocardiography data were collected.

RESULTS

There were two non-conduit-related deaths. Two conduits needed to be exchanged because of an increase in the gradient. Overall, all patients were improved in terms of New York Heart Association class. Comparison of preoperative and postoperative two-dimensional echocardiography gradient showed significant improvement. At the 30-month follow-up, no calcification was seen on the explanted conduits or on the two-dimensional echocardiography, although many of the patients are children.

CONCLUSIONS

The Shelhigh conduits seem to be an alternative to homograft especially in infants. These experiences are preliminary, and longer follow-up is required.

Cryopreserved homografts in the pulmonary position: determinants of durability

BACKGROUND

The cryopreserved homograft has emerged as the pulmonary conduit of choice for the repair of many congenital heart defects. It is also used for pulmonary valve replacement in the Ross procedure. Because of a wide range of patient ages and diagnoses, the risk of homograft failure may vary.

METHODS

We reviewed 185 consecutive pulmonary position implants performed between September 1985 and January 1999. We examined three age groups: patients less than 1 year of age (n = 53), patients 1 to 10 years of age (n = 46), and patients more than 10 years of age (n = 86).

RESULTS

Five-year Kaplan-Meier homograft survival was 25%, 61%, and 81% for the groups, respectively (p < 0.02). Smaller homograft size, younger patient age, and truncus arteriosus were risk factors for homograft failure in univariate analysis (p < 0.05). Smaller homograft size was the only predictor for homograft failure in multivariate analysis (p < 0.001). Twenty of 99 implants in patients less than 10 years old underwent transcatheter intervention. The 3-year Kaplan-Meier implant survival of this group (79%) was not different from those who did not undergo intervention (77%, p = 0.84). Survival of aortic and pulmonary homografts in patients less than 10 years of age was not different (p = 0.35). Ross procedure implants appear to have optimal survival (94%) at 5 years. Non-Ross implants in patients more than 10 years of age have 76% 5-year Kaplan-Meier survival, which is not different from Ross patients (p = 0.33).

CONCLUSIONS

Small homografts have limited durability. Aortic homografts perform as well as pulmonary homografts in young patients. Once patients receive an "adult-size" homograft, at approximately 10 years of age, risk for implant failure approximates that of patients undergoing the Ross procedure. Transcatheter interventions, when indicated, may prolong homograft life.

Independent factors associated with longevity of prosthetic pulmonary valves and valved conduits

OBJECTIVE

To evaluate the age dependence of variables predictive of pulmonary valve prosthesis replacement, we conducted the following analysis.

METHODS

Retrospective analysis of 945 operations in 726 patients undergoing placement of pulmonary valve prostheses was performed. Age was identified as a strong independent predictor of valve failure. The database was stratified into age-based subsets and predictors of valve replacement were identified within each subset.

RESULTS

For the entire cohort, freedom from valve replacement at 5 years was 81%. Younger age was strongly associated with decreased time to valve replacement by multivariable analysis (hazard ratio: 0.71/log-year, P <.001). Other independent factors included diagnosis, type of prosthesis, and time-dependent requirement for pulmonary valve stent placement. Important predictors of valve failure varied among age groups and are as follows: for Age Less Than 3 Months: valve type; for Age 3 Months To Less Than 2 Years: smaller normalized valve prosthesis size; for Age 2 Years To Less Than 13 Years: sex, smaller normalized valve prosthesis size, placement of endovascular stents, and valve type; for Age 13 Years To 65 Years: smaller normalized valve prosthesis size, placement of endovascular stents, and increased number of previous valve placements.

CONCLUSION

Age is a dominant risk factor predictive of pulmonary valve prosthesis failure. A significant interaction exists between age and the effects of diagnosis, valve type, and size on prosthetic pulmonary valve longevity.