The sorin freedom stentless pericardial valve: clinical and echocardiographic performance at 10 years.

Objective: The Sorin Pericarbon Freedom (SPF) is a stentless valve made of pericardium clinically available in 1990. We report the clinical and hemodynamic performance of the SPF at 10 years. Methods: From April 2000 to December 2005, 85 patients with a mean age of 75 \ub1 6 years (range 57-86), underwent aortic valve replacement (AVR) with an SPF. Mean left ventricular ejection fraction was 58 \ub1 10\% (range 29-86\%) and mean peak transvalvular gradient (PG) 86 \ub1 24 mmHg. Clinical evaluation was performed at 3, 6, 12 months, and yearly thereafter. Results: There were 2 operative deaths (2.4\%). Follow-up ranged from 2 to 135 months (mean 78 \ub1 32 months) and was 99\% complete. There were 35 late deaths, 7 of which were valve-related, with an actuarial survival of 45 \ub1 8\% at 10 years. Structural SPF deterioration occurred in 2 patients, with an actuarial freedom of 96 \ub1 3\%. A total of 4 patients were re-operated, 2 because of structural deterioration, 1 because of endocarditis, and 1 because of sinotubular junction dilatation; freedom from reoperation was 93 \ub1 4\% at 10 years. At last clinical control, 41 patients (89\%) were in NYHA class I or II. Mean SPF effective orifice area varied from 1.55 \ub1 0.66 cm2 for size 21 mm to 2.33 \ub1 0.86 cm2 for size 27 mm; PG varied from 19 \ub1 10 mmHg for size 21 mm to 11 \ub1 6 mmHg for size 27 mm. Left ventricular mass index decreased from 213 \ub1 51 gm/m2 to 157 \ub1 436 gm/m2 (p<0.001). Conclusions: The SPF has demonstrated overall good results in terms of valve durability and freedom from valve-related complications up to 10 years, with excellent hemodynamic performance

Developments in unsteady pipe flow friction modelling

This paper reviews a number of unsteady friction models for transient pipe flow. Two distinct unsteady friction models, the Zielke and the Brunone models, are investigated in detail. The Zielke model, originally developed for transient laminar flow, has been selected to verify its effectiveness for "low Reynolds number" transient turbulent flow. The Brunone model combines local inertia and wall friction unsteadiness. This model is verified using the Vardy's analytically deduced shear decay coefficient C* to predict the Brunone's friction coefficient k rather than use the traditional trial and error method for estimating k. The two unsteady friction models have been incorporated into the method of characteristics water hammer algorithm. Numerical results from the quasi-steady friction model and the Zielke and the Brunone unsteady friction models are compared with results of laboratory measurements for water hammer cases with laminar and low Reynolds number turbulent flows. Conclusions about the range of validity for the three friction models are drawn. In addition, the convergence and stability of these models are addressed.Anton Bergant, Angus Ross Simpson, John Vìtkovsk