Long-term effects of prosthetic materials

Short- and mid-term results of xenograft-bovine pericardial patch in the repair of intracardiac defects: final results of a single-centre study

INTRODUCTION

A variety of patch materials have been used in the repair of intracardiac defects. We evaluated the short- and mid-term clinical and echocardiography results of glutaraldehyde-preserved bovine pericardium patches used to repair intracardiac defects in our clinic.

METHODS AND RESULTS

This study examines the short- (up to 30 days post-operatively) and mid-term (up to 24 months post-operatively) results of 533 patients with intracardiac defects who underwent surgical correction with glutaraldehyde-preserved bovine pericardium patches between 2004 and 2010 at a university clinic. Short- and mid-term post-operative echocardiographic studies showed no evidence of calcification, thrombus, or aneurysmal dilatation on the patch. Vegetation developed in two (0.37%) of the 533 patients.

CONCLUSION

These results that have been obtained from a group of large number of patients imply that the glutaraldehyde-preserved bovine pericardium patches may be preferable in the closure of cardiac defects because of their low complication rates and ease of use.

Medtronic freestyle valves in right ventricular outflow tract reconstruction

BACKGROUND

Various pulmonary valve substitutes, with their inherent limitations, have been used in children and young adults. We chose the Medtronic Freestyle (Medtronics, Minneapolis, MN) valve because of its excellent hemodynamics, known durability in adults, and design features that allow modifications during implantation.

METHODS

Over a 3 1/2 year period the Freestyle valve was implanted in 47 patients age 2 to 58 years (mean 14.2, median 12.0) in the pulmonary position. All patients had pulmonic stenosis and(or) insufficiency from previous operations for tetralogy (27), pulmonary atresia (6), truncus (4), or other diagnosis (10). The indication for surgery was pure pulmonary insufficiency in 11 patients, pulmonic stenosis in 3, and mixed stenosis and insufficiency in 33. Root replacement technique was used with additional enlargement of the pulmonary artery branches in 10 patients.

RESULTS

Intraoperatively, one patient sustained a right ventricle tear and one a circumflex coronary artery injury during the dissection. There was one postoperative death. Two patients developed late subvalvular pannus formation, one of whom required reoperation. One patient was found to have an echo gradient of 95 mm Hg due to decreased leaflet motion and underwent cardiac catheterization at which the peak systolic gradient was determined to be 50 mm Hg. He has not required reintervention during his 3 1/2 years of follow-up. The remaining 43 patients have minimal gradients or insufficiency. All surviving patients are in New York Heart Association (NYHA) Class I.

CONCLUSIONS

The Medtronic Freestyle valve is an attractive alternative for RVOT (right ventricular outflow tract) reconstruction in children. It is readily available, versatile, and has excellent hemodynamic characteristics. Although long term follow-up is not yet available, longevity of this prosthesis, and freedom from complications, will hopefully be superior to valves with stents.

Reconstruction of the pulmonary valve and outflow tract with bicuspid prosthesis in tetralogy of Fallot

BACKGROUND

Right ventricular outflow tract and pulmonary valve implant in patients with tetralogy of Fallot may be required to avoid late postoperative right ventricular impairment. The use of porcine bicuspid prosthesis might be a technical alternative, although comprehensive studies on the long-term use of these prostheses are not available.

METHODS

Sixty-three patients (aged 5 months to 34 years; mean, 6 years) with tetralogy of Fallot and pulmonary hypoplasia underwent surgical repair and enlargement of the right ventricular outflow using preserved porcine pulmonary bicuspid prostheses. Fifty-two patients (82.5%) were followed and underwent clinical evaluation and serial Doppler echocardiography. The first 15 patients (29.4%), with ages ranging from 5 to 16 years (mean, 8.2 years) and postoperative follow-up of 48 to 87 months (mean, 65.1 months) underwent hemodynamic and cineangiographic evaluations.

RESULTS

There were 11 deaths (17.4%) in the early postoperative period. Of the 52 surviving patients (82.5%), 51 (80.9%) were followed for 1 to 87 months (mean, 42.0 months). Four patients (7.6%) had additional treatment. Of the 15 patients (29.1%) undergoing hemodynamic evaluation, 9 (60%), had mild valvular pulmonary insufficiency and 6 (40%) had moderate insufficiency. Only the right ventricle-to-pulmonary artery pressure gradients and the right ventricular ejection fraction showed statistically significant differences between groups. Right ventricular dimension, although increased in all patients, did not show statistically significant differences.

CONCLUSIONS

Right ventricular outflow tract and pulmonary valve repair in patients with tetralogy of Fallot using a bicuspid porcine pulmonary prosthesis is a simple, reliable procedure with good results in postoperative medium term follow-up.

Outcome of pulmonary and aortic homografts for right ventricular outflow tract reconstruction

To determine late patient outcome and homograft durability, we reviewed 326 patients who received aortic (n = 230) or pulmonary (n = 118) cryopreserved homografts for right ventricular outflow reconstruction between January 1985 and October 1993. Patient survival, including operative mortality, 5 years after the operation was similar between the two groups (pulmonary homograft 86%, aortic homograft 80%; p = not significant by log-rank test). However, 5-year freedom from homograft failure was significantly better for pulmonary homografts (94% versus 70%, p < 0.01 by log-rank test). Late calcification was evaluated by chest roentgenography and echocardiography. Overall, 20% of aortic homografts became moderately or severely calcified compared with 4% of pulmonary homografts (p < 0.01). Twenty-six percent of aortic homografts in children 4 years old or younger had moderate or severe obstruction associated with calcification, whereas only 11% of aortic homografts in patients over 4 years of age had calcific obstruction (p < 0.01). No late deaths among patients receiving pulmonary homografts were related to graft failure; two late deaths in the aortic homograft group were homograft related. Risk factors for patient mortality and homograft failure (defined as either need for homograft replacement because of homograft failure or as homograft-related death) were identified by the Cox multivariate analysis. Aortic type of homograft was a significant risk factor for homograft failure (p < 0.0001), but type of homograft was not correlated with patient mortality. Age 4 years or younger was a significant risk factor for both mortality (p < 0.01) and homograft failure (p = 0.03) in aortic homograft recipients but not in pulmonary homograft recipients. These results indicate that both aortic and pulmonary homografts provided excellent intermediate-term patient survival after right ventricular outflow tract reconstruction, but pulmonary homografts are more durable than aortic homografts with less calcification and obstruction, especially among children 4 years old or younger.

Severe stenotic scar contracture of the Microvel Hemashield right-sided extracardiac conduit

We report 2 patients who developed severe scar contracture of a Microvel Hemashield valveless right-sided extracardiac conduit implanted 14 months earlier. In both cases, the diameter of the conduit was reduced along its entire length, with the prosthetic material plicated inward by retraction and organization of connective fibrous tissue on either side of the conduit.

Extended use of a pulmonary homograft for right ventricular outflow tract reconstruction

When a pulmonary homograft is used for reconstruction of the right ventricular outflow tract a patch or tube extension is usually required to close the gap in the right ventriculotomy. We describe here a simple method by which a large patch can be tailored from the homograft using the distal main pulmonary artery and its branches.

Comparative studies of prosthetic materials in the left atrium of the dog

To assess the healing process of various intracardiac prosthetic graft materials, we inserted autologous left atrium (control), autologous pericardium (AP), bovine pericardium (BP), polytetrafluoroethylene (PTEE) and woven Dacron (WD) patches into excised defects in the left atrial wall of 15 dogs. Two patches were implanted into each heart utilizing six patches for each material. Three months after graft placement, histological examination revealed chronic inflammation and fibrosis for all materials. Dense connective tissue surrounded the grafts in which fibrosis was most prominent. Cartilage formation occurred in 11 grafts: 5 BP, 4 PTFE, 1 control and 1 AP site. This change was not evident with WD. The extent of cartilage formation was greatest in BP. Bone formation occurred in 3 BP sites. 2 PTFE and 1 control site. Quantitative calcium concentrations were similar for all of the grafts without bone formation. Calcium concentrations at sites with bone formation averaged 15.13 mg/g +/- 6.39 mg/g compared to 0.939 +/- 0.419 for sites without bone formation (p less than 0.0001). We conclude that while inflammation, fibrosis and connective tissue thickening occur with healing of all graft materials, cartilage and bone formation differ with respect to the material employed.

Late right ventricular reconstruction following valvotomy in pulmonary atresia with intact ventricular septum

Experience over two decades in the surgical management of pulmonary atresia with intact ventricular septum demonstrates that eventual right ventricular (RV) reconstruction is possible in the majority of patients surviving valvotomy in infancy. Ten of 17 operative survivors of early valvotomy have eventually received a patch graft to the RV outflow tract, with no reoperative deaths (mean follow-up, 7.4 years). RV systolic pressures, suprasystemic prior to reoperation, are near normal after outflow patch reconstruction. Serial cineangiograms show evidence of RV growth by measurement of tricuspid annulus diameter (TAD), and demonstrate a rate of growth [d(TAD)/d(body length)] greater than a normal rate derived from autopsy data. The mean TAD growth rate is significantly greater than that of patients with less favorable ventricle types treated with a systemic-pulmonary shunt alone. Measurement of TAD is a useful method for following RV growth, and may aid in selecting patients for RV reconstruction.

Comparison of prosthetic graft materials as intracardiac right atrial patches

An experimental animal model was developed to study the fate of prosthetic graft materials within the heart. Autologous pericardium, bovine pericardium, polytetrafluoroethylene, woven Dacron, and autologous right atrium (control) patches were implanted into the wall at three sites on the right atrium in each of 10 dogs (six patches for each graft material). The atria were harvested 90-100 days later and histologic examination and quantitation of calcium were performed. Chronic inflammation and fibrosis were found in 29 of 30 grafts. Cartilage formed in 26 of 30 sites and was found both in the center and around the edges of the grafts. In addition to cartilage, bone including marrow elements formed in the two autologous materials at 4 of the 12 sites and in 1 of the Dacron graft sites. Calcium content was greater in the control and the bovine pericardial grafts than in the other graft materials (P = NS). The incidence and degree of inflammation, fibrosis, calcification and cartilage, and bone formation were similar in all materials. We conclude that the healing process of these intracardiac graft materials is a generalized phenomenon independent of the inherent properties of a specific graft material.

Bovine pericardium for correction of congenital heart defects

From July, 1980, until January, 1985, preserved bovine pericardium was utilized in the repair of a wide variety of congenital heart defects in 105 patients. Ages ranged from newborn to 56 years (mean, 9.6 years). Eighty-three of the 87 long-term survivors are in New York Heart Association Functional Class I or II. Bovine pericardium was not a contributing factor in the 12 hospital and 6 late deaths. The material was found to be flexible and easy to suture. No patient has demonstrated calcification of the patch in follow-up ranging from 6 to 60 months (mean, 30.2 months). Preserved bovine pericardium offers several potential advantages in the correction of congenital intracardiac defects.

Pharmacologic inhibition of scar contracture of intracardiac prosthetic patches

Significant fibrosis and contracture often cause complications of pericardial and Dacron grafts within the heart. Both continue to be utilized because more suitable materials are unavailable. Newer prosthetic materials and the administration of drugs that might minimize intracardiac fibrosis and contracture after implantation were studied. Measured patches of three prosthetic materials were implanted into the right atrium of 18 dogs: 6 with expanded polytetrafluoroethylene (PTFE or Gore-Tex--W. L. Gore & Associates, Elkton, Md.), 6 with glutaraldehyde-preserved bovine pericardium, and 6 with Dacron patches. The animals were sacrificed after 8 weeks and gross and microscopic pathologic examinations were performed. The patch materials did not intrinsically shrink but all demonstrated marked distortion from the growth of surrounding scar tissue. In a fourth group of eight dogs with intraatrial Dacron patches, four were treated for 8 weeks with oral 3-aminopropionitrile fumarate, and four were not treated. A blinded observed evaluated the adhesions on a scale of 0 = no adhesions or patch distortion, to 4 = dense adhesions with marked distortion of the patches. The untreated dogs had dense adhesions of the lung and pericardium and the patches were encased in scar tissue with marked distortion. The average score was 3.5. The treated dogs had only minimal pleural adhesions and only a thin neointimal covering of the patch with virtually no distortion. The average score was 1.0 (P = 0.0032). The tensile strength of the healed atriotomies was evaluated with stress testing. The intact atrial wall ruptured at a force of 2.60 +/- 0.37 kg/m/sec2, the untreated atriotomy wound at 2.38 +/- 0.18 kg/m/sec2, and the treated atriotomy wound at 2.60 +/- 0.17 kg/m/sec2. There was no statistically significant difference among these groups. No other side effects of the 3-aminopropionitrile fumarate were noted, with only a single superficial wound infection caused by early postoperative trauma. Pharmacologic inhibition of scar formation minimized distortion and contracture of intracardiac prosthetic patches and decreased adhesions. Though further experimental evaluations are necessary, prolonged low-dose oral administration of beta-aminoproprionitrile (BAPN) may be beneficial in preventing complications of prosthetic implants and reoperative cardiac surgery in children.

Second operations for pulmonary stenosis or insufficiency after repair of tetralogy of Fallot

Twenty-four patients with previous surgery for repair of tetralogy of Fallot were in need of subsequent operative procedures for either residual pulmonary stenosis or pulmonary valve incompetence. The second operation was performed 1 to 21 years after the initial repair. The patients with pulmonary valve incompetence had evidence of marked right ventricular dysfunction and required pulmonary valve replacement. The patients with residual pulmonary stenosis had modifications of their pulmonary outflow tract to reduce the gradient. Five of the 15 patients with stenosis required pulmonary valve replacement. Clinical improvement has been good, but objective reversal of right ventricular dysfunction has been difficult to document.