Pleural flap closure of pericardial defects following intrapericardial pneumonectomy

Bioengineered tissue solutions for repair, correction and reconstruction in cardiovascular surgery

The treatment of cardiac alterations is still nowadays a dramatic issue in the cardiosurgical practice. Synthetic materials applied in this surgery have failed in their long-term therapeutic efficacy due to low biocompatibility and compliance, especially when used in contractile sites. In order to overcome these treatment pitfalls, novel solutions have been developed based on biological tissues. Patches in pericardium, small intestinal submucosa, as well as engineered tissues of myocardium, heart valves and blood vessels have undergone a large preclinical investigation in regenerative medicine studies. Clinical translation has been started or reached by several of these new bioengineered treatment alternatives. This review will describe the preclinical and clinical experiences realized so far with the application of biological tissues in cardiovascular surgery. It will depict the progressive steps realized in the evolution of this research, as well as it will point out the challenges yet to face in order to generate the ideal biomaterial for cardiovascular repair, corrective and reconstructive surgery.

Cardiac herniation following pneumonectomy--an old complication revisited

Cardiac herniation is a recognised complication of pneumonectomy when a pericardial defect has been made during resection. This complication is very rare and, with the increasing preference for more limited resections, is even less frequently encountered now than it was several decades ago. Uncorrected cardiac herniation is usually lethal, with a high incidence of morbidity and mortality even after correction. We present a case of left-sided cardiac herniation following intrapericardial pneumonectomy to illustrate the difficulty of making this rare diagnosis. Aetiology, pathophysiology, clinical picture and diagnosis of cardiac herniation are reviewed. We also describe the treatment and prevention of this serious complication. Cardiac herniation should be considered in any patient with acute deterioration after pneumonectomy.

Experience with Expanded Polytetrafluoroethylene (ePTFE Gore-Tex) Surgical Membrane for Coronary Artery Grafting: Does ePTFE Surgical Membrane Predispose to Postoperative Mediastinitis?

The advantage of completely closing the pericardium after a coronary artery bypass grafting is the avoidance of injury of the heart and grafts during a re-operation. However, it would obviously be counterproductive to close the pericardium with a substitute that is predisposed to infection. This study was designed to evaluate the safety of ePTFE surgical membrane in comparison to native pericardium or autologous tissue. Between January 1992 to March 2003, 695 coronary artery bypass graftings were performed. The hearts and grafts were covered with ePTFE surgical membrane (474 cases: ePTFE group), or autologous pericardium and/or other autologous tissue (221 cases: non-ePTFE group). Often, a bilateral dissection of the internal thoracic artery was performed, which lengthened the surgery, the cardiopulmonary bypass, and the aortic clamp, in the ePTFE group. But there was no difference between the ePTFE group (2.1%) and the non-ePTFE group (3.2%) in the development of postoperative mediastinitis. There was also no difference between the two groups in the organism type of the infection. Methicillin resistant Staphylococcus aureus (MRSA) is the most common organism cultured from sternal wound infections; there were five cases in the ePTFE group, and four cases in the non-ePTFE group. In the ePTFE group, the hospital mortality due to postoperative mediastinitis was zero, and there was also no significant difference between the ePTFE group and the non-ePTFE group in time from the drainage operation to discharge; 74.3 days in the ePTFE group, and 81.0 days in the non-ePTFE group. The clinical use of ePTFE surgical membrane for a coronary artery bypass grafting does not appear to be a risk factor for mediastinitis.

Expanded PTFE membrane to prevent cardiac injury during resternotomy for congenital heart disease

BACKGROUND

Resternotomy for repair of congenital cardiac defects can result in cardiac injury. Closure of the pericardium during the initial operation may prevent this, and several pericardial substitutes have been tried, with variable results, in patients in whom primary pericardial closure is not possible. We conducted a multicenter observational study of the use of the expanded polytetrafluoroethylene membrane (Preclude Pericardial Membrane, formerly called the Gore-Tex Surgical Membrane; W. L. Gore & Associates, Flagstaff, AZ) in patients likely to undergo reoperation for treatment of congenital heart disease.

METHODS

Data were collected retrospectively on all patients in whom the expanded polytetrafluoroethylene membrane was inserted at the initial operation for congenital heart disease at 12 centers in 1984 to 1993.

RESULTS

A total of 1,085 patients (mean age, 55 +/- 2.5 months) received the membrane. During follow-up ranging from 1.3 to 10.5 years, 105 reoperations were performed. Injury during resternotomy occurred in only 1 patient (1% of reoperations). There were no membrane-related deaths or complications in the entire series of 1,085 patients.

CONCLUSIONS

The expanded polytetrafluoroethylene membrane was safe and effective in helping to prevent cardiac injury during resternotomy for treatment of congenital heart disease.

Pericardial repair after extensive resection: another use for the pedicled diaphragmatic flap

BACKGROUND

Extended resection for pulmonary malignancy frequently leaves a large pericardial defect, sometimes associated with resection of the phrenic nerve. On the left the defect does not require repair; as long as the defect is sufficiently large to avoid constriction, the heart can herniate freely. On the right such herniation is associated with venous inflow occlusion and death. The pedicled diaphragmatic flap has been used in other situations in thoracic surgery. We have modified this to allow closure of the pericardial defect and concurrent plication of the denervated diaphragm. It may also be used to cover the bronchial stump or a bronchial anastomosis.

METHODS

The flap has been used in 13 patients over an 11-year period.

RESULTS

Secure closure of the pericardial defect has been achieved in all patients with satisfactory plication of the diaphragm. Reoperation for bleeding was necessary in 3 patients, but in only 1 was the diaphragm shown to be the site of bleeding. Patients otherwise made an uneventful recovery.

CONCLUSIONS

A large pedicled flap of redundant diaphragm provides secure closure for large pericardial defects after extended right pneumonectomy.

A new biological membrane for pericardial closure

In an attempt to develop a new and better biological membrane for the pericardium, we evaluated the use of glutaraldehyde treated human amniotic membrane (AM) and compared it to polytetraflouroethylene (PTFE) membrane as a pericardial substitute. Four dogs underwent a right thoracotomy. Two 4 x 3-cm portions of pericardium, 3-4 cm apart, were excised in each animal and both sites replaced with a similar sized patch of 0.8% glutaraldehyde-treated AM and 0.2-mm PTFE membrane respectively. The AM was sutured to the pericardial defect with its smooth surface facing the epicardium. After 18 weeks, the materials were evaluated. The AM patches revealed minimal extrapericardial and no epicardial adhesion. The PTFE patches had moderate to severe epicardial adhesions and severe extrapericardial adhesions. Histopathological examination of AM patches revealed that the integrity of the AM was preserved, however, neovascularization and slight lymphocytic infiltration were observed. In the PTFE patches, there were severe inflammatory infiltration and fibroblast proliferation into both surfaces. AM patches by virtue of their low immunogenicity evoke very minimal host to graft reaction. These AM grafts, however, tear easily unless carefully sutured. Improved methods of treatment may improve suturing strength. We conclude that AM performs satisfactorily and is superior to PTFE as a pericardial substitute.

Pericardial substitutes: a survey

Many thoracic surgeons have used pericardial substitutes to reduce the risk of reoperation, but there have been few reports of these procedures. Therefore, we used a questionnaire to gather information on experience with use of pericardial substitutes and to document the findings at reoperation. A six-question survey was sent to 2,344 members of The Society of Thoracic Surgeons, requesting surgeons to list their experience with pericardial substitutes and at reoperation in patients with these substitutes in place. Of the 634 surgeons who responded to the survey, 120 reported the insertion of 3,828 pericardial substitutes. Two hundred thirty-six reoperations were reported by 89 surgeons. None of the pericardial substitutes was reported to be completely successful in facilitating reoperation. The experience with polytetrafluoroethylene (PTFE) pericardial substitutes was reported to be significantly more satisfactory than that with all other substitutes (p = 0.0004 by chi-square analysis), but 14% of surgeons who used PTFE said they were dissatisfied at reoperation. Based on the results of this survey, we suggest caution, careful documentation, and long-term follow-up studies before widespread use of pericardial substitutes can be recommended.

Clinical experience with expanded polytetrafluoroethylene Gore-Tex surgical membrane for pericardial closure: a study of 110 cases

Complete closure of the pericardium after cardiac operations has the advantage of avoiding injury of the heart and great vessels during reoperation. Between 1985 and 1987, the pericardium was closed with Gore-Tex Surgical Membrane (SM) in a selected series of 110 patients 1 month to 76 years of age. Fifty-three patients had congenital heart lesions and 57 patients had acquired heart disease. Overall hospital mortality was 3/110 cases. In no instance was there a relationship between occurrence of death and pericardial closure with SM. There was one episode of cardiac tamponade on the seventh postoperative day. One patient developed fever and leukocytosis due to a mediastinal hematoma. During a mean follow-up of 15 months, four patients had to be reoperated upon three, four, eight weeks, and eight months after primary operation. The anterior wall of the heart had no adhesion with the SM and the other parts of pericardium could be dissected easily. Scanning electron microscopic examination of the explanted SM patches showed neither cellular ingrowth nor immunocompetent cellular elements. The Gore-Tex Surgical Membrane has the advantages of easy availability and lack of reaction between its surface and the epicardium and pericardium. We believe its routine use should be encouraged in patients with high probability of reoperation after repair of complex cardiac anomalies, implantation of bioprostheses, coronary revascularization for one- or two-vessel disease, and repair of degenerative disease of the ascending aorta.

Autologous pericardium versus a xenograft substitute in myocardial wound healing

This study compared repair of myocardial wounds covered with autologous pericardium to healing of wounds covered with glutaraldehyde-preserved bovine pericardium in an experimental canine model. Right (RV) and left (LV) full thickness ventriculotomies were made and closed. In the control group (n = 12), the pericardium was closed over the wound; in the experimental group (n = 12), wounds were covered with bovine pericardium. Animals were sacrificed at 14, 21, 28, and 42 days. After excising the pericardium, 6 mm punch biopsies of normal RV, RV wound, normal LV, and LV wound were assayed for hydroxyproline (HPro). Both autologous and bovine pericardium became densely adherent to the wounds. Bovine pericardium was mildly adherent over unwounded areas, while autologous pericardium was usually free. Normal RV contained more than twice as much HPro as normal LV (5.4 +/- 0.57 micrograms/mg vs 1.7 +/- 0.35 micrograms/mg, P less than 0.0002). A gradual rise in HPro over time was seen in both groups, but this increase was statistically significant only at 42 days (P less than 0.05). There was no significant difference in HPro between wounds covered with autologous pericardium and those covered with bovine grafts (P = 0.13) at any of the sample times in this study. In this experimental canine model, the pericardium does not appear to play a prominent role in myocardial wound healing by contributing collagen-producing fibroblasts. Furthermore, the bovine pericardial xenograft becomes densely adherent to LV and RV incisions. In the clinical setting, such may make reoperation more hazardous when the heart has been previously incised or coronary bypass grafts have been constructed.

Implantation of pericardial substitutes

Pericardial substitutes have been shown to decrease the formation of pericardial adhesions. For a pericardial substitute to be properly implanted, it must lie over the heart smoothly without buckling and prevent the accumulation of blood under its surface. The technique we describe prevents buckling of the pericardial substitute and consequently reduces the formation of pericardial adhesions.

Heterologous pericardium for the closure of pericardial defects

Patches of glutaraldehyde-preserved porcine pericardium were transplanted orthotopically into 20 dogs to see if they might make a satisfactory pericardial substitute. Two dogs had mediastinal infections and were excluded from this study. All animals were reoperated on at regular intervals between 15 and 300 days. In 15 dogs there were no adhesions between the porcine pericardium and the host's epicardium. Histological study showed healing between both pericardiums and no degenerative changes in transplanted pericardium. Glutaraldehyde porcine pericardium has been utilized in 8 patients to close the pericardial cavity. There have been no problems related to the pericardial grafts after a maximum follow-up of 9 months.