Structural degeneration of pulmonary homografts used as aortic valve substitute underlines early graft failure.

OBJECTIVES: The limited availability of donor valves and experimental evidence that pulmonary valves can withstand systemic pressure made us use cryopreserved pulmonary homografts as aortic valve substitutes. We observed a high incidence of early reoperation because of severe graft insufficiency due to cuspal tears. The mid-term results are evaluated in this study and histological analysis of explanted homografts is performed to investigate the cause of graft failure. METHODS: From December 1991 to April 1994, 16 patients (13 male; mean age 37.3 years, range 21-59 years) underwent aortic valve replacement with a cryopreserved pulmonary homograft. The indication was endocarditis (n = 4), bioprosthesis degeneration (n = 3) or congenital aortic valve disease (n = 9). All homografts were implanted freehand in the subcoronary position. All patients were contacted for follow-up and recent echo-Doppler studies were reviewed. Six explanted homografts were examined microscopically using routine histological techniques to analyze changes in cell population, collagen and elastic fiber structure. RESULTS: Follow-up was complete in all patients. Reoperation was required in ten patients because of severe graft incompetence (mean implantation time 5.9 years, range 2.8-8.0 years). In two patients, recurrent endocarditis was the cause of graft failure. In the other eight patients the leaflets looked pliable and thin with gross tearing in one or more cusps. The histopathologic changes observed were remarkably similar in all examined grafts: the cusp tissue was almost non-cellular and the collagen fiber structure had mostly disappeared. At the site of rupture, the tissue had become thin with strongly degenerated collagen and elastic fiber structure. In the six patients with a homograft remaining in situ, echo-Doppler showed trivial to mild insufficiency in five cases and moderate to severe in one case, whereas no significant gradients were observed. CONCLUSIONS: We concluded that structural reduction of cell number and degenerative alterations in the molecular composition of the extracellular matrix in valve tissue is the main cause of early graft failure in this series. The use of cryopreserved pulmonary homografts in the systemic circulation is therefore not advised.     

Results of the Ross operation in a pediatric population

Objective: To analyse the results of the mid-term clinical and echocardiographic follow-up of the pediatric Ross operation. Methods: Echo-Doppler follow-up of 53 consecutive pediatric Ross procedures performed between 1994 and 2003. Median age was 9.7 years at time of operation (2 weeks–17.7 years). Six patients were younger than 3 months. Median age at follow-up was 15.6 years. Aortic valve/left ventricular outflow tract (LVOT) anomalies were congenital in 49 (92%). Seventy percent had previous surgery or balloon valvuloplasty. Root replacement was used in all. Thirteen patients (25%) had LVOT enlargement. Mean cross-clamp time was 113 (69–189) minutes. Results: Early mortality occurred in 3 patients after emergency surgery following balloon failure (n=1) and extended Ross following interrupted arch/VSD repair (n=2). Late mortality was due to LV fibroelastosis in 2 patients and complicated pulmonary artery stenting in another. RVOT reoperations were required because of late homograft obstruction in 2 patients and because of pulmonary artery stenosis in another. Five patients (9.4%) were reoperated for pulmonary autograft dilatation (n=3) and for leaflet fibrosis or perforation (n=2). Autografts were repaired in two patients, while a mechanical valve was inserted in 3 cases. At 9 years the actuarial survival and event free survival were 89 and 74%, respectively. At last follow-up 90% of autograft diameters indexed to body surface area was above the 90th percentile of normal aortic root diameters. LVOT and RVOT gradients were low and autograft insufficiency was trivial to mild in 84% and mild to moderate in 16%. Autograft stenosis was not noticed. Conclusions: The pediatric Ross procedure remains an important tool but autograft dilatation also occurs in the pediatric population. The significance of this finding has yet to be determined.     

Behavioural Effects of the Methanolic Root Bark Extract of Securinega Virosa in Rodents

Securinega virosa is used traditionally as sedative in children and in mental illnesses. In this study, the behavioral effects of methanolic root bark extract of S. virosa were investigated in mice. The results revealed that the extract significantly (P<0.05) and dose-dependently reduced the onset and prolonged the duration of sleep. The extract significantly (P<0.05) decreased exploratory activity and reduced the rate of apomorphine-induced stereotyped climbing at the doses tested (6.25–25mg/kg). It also produced a significant and dose-dependent motor coordination deficit in mice at the doses tested (P<0.01). The intraperitoneal median lethal dose in mice was 774.6mg/kg while the preliminary phytochemical screening revealed the presence of alkaloids, tannins, saponins and flavonoids. These results suggest that methanolic root bark extract of S. virosa contains biologically active principles that are sedative in nature and lend pharmacological credence to the ethnomedical use of the plant.