A novel anticalcification treatment strategy for bioprosthetic valves and review of the literature.

BACKGROUND AND AIM OF THE STUDY: Glutaraldehyde (Glut) fixed bioprosthetic valves fail due to progressive dystrophic calcification. Many treatments have been proposed to eliminate calcification but none have been entirely successful. Calcitonin (CT) and sodium bisulfite (BSF) have recently been introduced as independent anticalcification reagents. It is postulated that their combined effect, along with the addition of the detergent Tween 80 and alcohol at 37°C, may efficiently minimize tissue calcification due to aldehyde adduct formation and elimination of lipids. MATERIAL AND METHODS: Three groups were created from porcine aortic leaflets: group I (Glut only), group II (Glut with 1% CT, 12.5% BSF, and 1.2% Tween 80 at 37°C), and group III (Glut with 1% CT, 10% BSF, 1.2% Tween 80, and 20% alcohol at 37°C). All tissues were implanted subdermally in three sets of eight (group I), six (group II), and five (group III) Wistar rats. After 4 months, the tissues were retrieved and lyophilized at -40°C at 100 mm Hg. The calcium was measured with a flat atomic absorption technique. RESULTS: The preimplantation calcium (Ca) concentration in mg Ca/gram of tissue was 1.79 ± 0.14 in group I, 1.65 ± 0.28 in group II, and 0.72 ± 0.79 in group III (P = ns). After 4 months, the Ca concentration was 277.55 ± 32.52, 103.54 ± 5.39 (P < .001) and 42.02 ± 15.63 (P < .001), respectively. There was also a significant difference (P < .001) between groups II and III. CONCLUSION: The combination of CT and BSF along with the detergent Tween 80 and alcohol at 37°C mitigates the calcification efficiently as compared to Glut treatment only.

Calcitonin as an anticalcification treatment for implantable biological tissues.

BACKGROUND AND AIM OF THE STUDY: Calcification remains the major role of failure of implantable biomedical material and in particular of bioprosthetic valves. Various treatments have been proposed to mitigate calcification of glutaraldehyde-fixed bioprosthetic valves but none have succeeded in inhibiting or mitigating efficiently the calcification process of the implantable biological tissues. Since the discovery of calcitonin (CT) and its therapeutic role in treating hypercalcemic patients, CT has never been tried as an anticalcification treatment for biomaterials. It is postulated, that tissue calcification may be efficiently minimized by forming adducts with aldehyde groups thus eliminating the places of the biological tissues onto the calcium cations could be deposited. MATERIAL AND METHODS: Fresh porcine aortic leaflets were cut radially in three parts. Three groups of tissue were created. Group I (glutaraldehyde only), Group II (glutaraldehyde with 1% CT) and Group III (glutaraldehyde with 10% CT). All tissues were then implanted subdermally in three sets of 8 (Group I) and 9 (Group II and Group III) male Wistar rats of 12 days old. 21 days later the rats were euthanized by inhalation of CO2. The tissues were retrieved and after rinsing with distilled water 3 times, were lyophilized at -40°C at high vacuum pressure of approximately 100mmHg for 16h. The calcium content was then measured with flat atomic absorption technique. RESULTS: The preimplantation values of Ca concentration as expressed in mg Ca/g of tissue were 1.79±0.14 in Group I, 4.78±0.0079 in Group II and 2.88±0.17 in Group III (p=ns). 21 days later the values of Ca concentration were 126.95±12.97 for Group I, 24.69±2.71 for Group II (p<0.05) and 27.16±2.95 for Group III (p<0.05). There was not significance difference between Groups II and III, even if Group II showed a less accumulation of Ca concentration (×5.16) than Group III (×9.43). CONCLUSION: An anticalcification treatment based on calcitonin as an additive to buffered glutaraldehyde, mitigates the calcification process of the implantable biological tissues, as compared to glutaraldehyde treatment only.

Results of the modified bi-pectoral muscle flap procedure for post-sternotomy deep wound infection.

PURPOSE: Post-sternotomy deep sternal wound infection (DSWI) is a severe complication of cardiac surgery. The introduction of omental and muscle flaps has resulted in a significant decrease in morbidity and mortality. In this article, we present the findings for a series of 55 consecutive patients with DSWI treated using an alternative bi-pectoral musculofascial flap technique. METHODS: The patients were stratified into two groups (one-or two-stage intervention). Patients with septic wounds initially underwent debridement and wound treatment, while vacuum therapy was used in a subset of the subjects. All patients were treated with wound debridement and bi-pectoral advancement flap reconstruction. RESULTS: 30-day mortality was 5.4%. Most patients (72%) were treated in two stages, while vacuum therapy was used in 20% of the patients. The mean number of hospitalization days was 8 and 12 for the one- and the two-stage groups, respectively. Reconstruction was successful in all but three patients, each of whom developed recurrent infection. No major morbidity was reported at a mean follow-up of 82 months with excellent functional and aesthetic outcomes. CONCLUSIONS: Pectoralis-major muscle flaps remain relevant in the modern management of post-sternotomy mediastinitis. The addition of an omental flap should be considered in cases in which the lower sternum is involved. Prompt diagnosis and a meticulous surgical technique ensure favorable results for the majority of patients.

The Belsey Mark IV: an operation with an enduring role in the management of complicated hiatal hernia.

BACKGROUND: The Belsey Mark IV operation has been used for the management of hiatal hernia for over 40 years, but with the introduction of laparoscopic techniques its role has become questionable. To determine the current role of this procedure we present a contemporary series of patients. METHODS: We reviewed fifteen consecutive patients, mean age of 63 years, who underwent a Belsey Mark IV fundoplication for gastroesophageal reflux in the presence of a hiatal hernia in our Department from January 2005 to March 2011. Indications for the thoracic approach included paraesophageal hernias, recurrent hiatal hernias and previous upper abdominal surgery. RESULTS: There was no operative mortality. Immediate postoperative morbidity included 1 case of bleeding, 1 case of pneumonia and 1 case of atrial fibrillation. The mean length of stay was 5.9 days. After a mean follow-up time of 49 months, all patients reported total or partial alleviation of their symptoms. No hernia recurrence was detected during barium swallow examination. CONCLUSIONS: The Belsey approach is a procedure that can be useful as an alternative in selected cases when there are co-morbidities complicating the transabdominal (laparoscopic) approach.

Hydrodynamic performance of a prototype bioprosthetic valve derived from the pulmonary valve of Phoca groenlandica.

Biological valves offer significant advantages over mechanical valves, and for this reason, we studied the possibility of using a new animal source such as that of Phoca groenlandica. Four aortic and four pulmonary leaflets were cut radially and their uniaxial tensile testing was evaluated. Three prototype pulmonary valves of Phoca groenlandica preserved in buffered glutaraldehyde solution 0.625% at pH 7.4 were mounted on a 19, 21, and 27 mm novel support system (stent) with heart shape commissural posts covered with polytetrafluoroethylene. The valves were tested in a steady flow system, the peak pressure gradients (PPGs) were measured, and the effective orifice areas (EOAs) were calculated for the flows of 3, 4, 5, 6, and 8 L/min. There were five different measurements for each flow variant. Aortic and pulmonary leaflets present no statistically significant difference in failure strength (p = 0.93). The PPGs across the valves for the flow of 3, 4, 5, 6, and 8 L/min for all three tested valves were low and the corresponding calculated EOAs were large. The new bioprosthetic valve derived from the pulmonary valve of Phoca groenlandica mounted on this novel support system presented a satisfactory hydrodynamic performance in a steady flow system. More research is needed before it can be considered suitable for human cardiac valve replacement.

Cardiopulmonary bypass assisted resection of mediastinal masses.

We report a recurrent solitary fibrous tumor of the mediastinum that was encircling the right pulmonary artery. The resection of the tumor with the involved right pulmonary artery segment and sequential graft reconstruction of the vessel was facilitated by the use of cardiopulmonary bypass. We review the indications, management, and outcomes of cardiopulmonary bypass for the resection of mediastinal masses.

In vivo calcification of glutaraldehyde-fixed cardiac valve and pericardium of Phoca groenlandica.

Calcification remains the main reason for failure of bioprosthetic valves. The aim of this study was to evaluate the in vivo calcification response of a new bioprosthetic valve, derived from cardiac tissue of Phoca groenlandica. Aortic and pulmonary leaflets, bovine, and Phoca groenlandica pericardia were fixed in buffered glutaraldehyde solution. Tissues were divided into four groups: group 1, bovine pericardium (BP); group 2, pulmonary leaflets; group 3, seal pericardium; and group 4, aortic leaflets. All samples were implanted subdermally into four sets of eight female 12-day-old Wistar rats for 21 days. The tissues were divided into two parts for calcium measurement, and histology with hematoxylin-eosin, von Kossa, and Weigert Van Gieson staining. All groups experienced significant calcification. Group 1 with 1.39 mg/g (0.34) before and 125.78 mg/g (21.48) after implantation (p < 0.001), group 2 with 1.50 mg/g (0.43) before and 151.85 mg/g (19.1) after (p < 0.001), group 3 with 3.15 mg/g (0.62) before and 116.38 mg/g (33.74) after (p < 0.001), and group 4 with 1.84 mg/g (0.52) before and 126.95 mg/g (13.37) after (p < 0.001). Explant samples showed foreign body response, disorganized collagen, and obvious calcification. The cardiac valve and pericardium of Phoca groenlandica calcify to the same extent as the BP.

Experimental replacement of pig trachea with novel bioprosthesis from harp seal.

Tracheal replacement has been a challenging problem for thoracic surgeons for over half of a century. We evaluated the in-vivo performance of a new tracheal bioprosthesis derived from Harp seal (Phoca groelandica) trachea that was fixed and preserved in 0.625% buffered glutaraldehyde solution for 3 months. Ten young male pigs weighing 27-32 kg (mean, 28.7 kg) underwent replacement of a tracheal segment with this new bioprosthesis. The length of replaced trachea was 1.8-2.4 cm (mean, 2.17 cm), representing 2-3 cartilage rings. All pigs survived the operation uneventfully. No immunosuppression drugs were used. The pigs eventually developed dyspnea and were euthanized on postoperative day 17-39 (mean, 30.8 days). Macroscopic and histological analysis showed an intact bioprosthesis but near-total occlusion of the native trachea by a ring of inflammatory infiltration at the site of distal anastomosis. More experiments involving a different concentration of the preservation agent, different management, and perhaps the use of bioengineering techniques are needed to improve the performance of this novel bioprosthesis.