Naomali Amarasena

Oxford University Hospitals NHS Trust, Oxford, England, United Kingdom

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Publications (5)19.25 Total impact

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    ABSTRACT: The medium-term hemodynamic performance of stentless valves has not been widely reported, particularly in comparison with in vitro studies. Therefore, we have assessed prospectively the hemodynamics of the Edwards Prima valve in its fifth year after implantation in the aortic position, and compared the results with those at 1 month after implantation and also with in vitro data. Thirty-five patients (age, 77 +/- 6 years; 19 men) were prospectively studied by Doppler echocardiography at 1 month and 52 +/- 8 months after implantation of a Prima stentless valve. Valve hemodynamics were assessed by measuring the mean pressure gradient, mean valve resistance, and effective orifice area. Left ventricular systolic function was quantified by ejection fraction, the degree of hypertrophy by ventricular mass index, and the ratio of ventricular wall thickness to cavity radius as a measure of ventricular geometry. With a mean valve size of 24.6 +/- 2.2 mm in the fifth year after implantation, the mean pressure gradient was 6.2 +/- 3.5 mm Hg, the mean valve resistance, 29 +/- 16 dyne x s(-1) x cm(-5)), and the effective orifice area was 2.05 +/- 0.50 cm2. Compared with 1 month after operation, there was a 47% decrease in mean valve resistance (p = 0.002) and a 39% increase in effective orifice area (p = 0.001). Furthermore, both effective orifice area and mean valve resistance in the fifth year did not differ from their in vitro counterparts, whereas the left ventricular ejection fraction (0.64 +/- 0.14), the left ventricular mass index (119 +/- 49 g/m2), and the ratio of ventricular wall thickness to cavity radius (0.44 +/- 0.13) were within the normal range. This study suggests that the Prima valve is a reliable stentless aortic bioprosthesis. This is supported by a favorable medium-term clinical outcome, durable hemodynamic performance, and normal mean values of left ventricular ejection fraction and mass index in the fifth year after implantation.
    No preview · Article · Oct 1998 · The Annals of Thoracic Surgery
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    ABSTRACT: The Freestyle valve is a porcine aortic root fixed with net zero pressure across the cusps and treated with the anticalcification agent alpha-aminooleic acid. We evaluated the hemodynamic function of this stentless valve. We implanted the valve into 80 consecutive patients scheduled to receive a bioprosthesis. Sixty-nine patients were more than 70 years old and 14 had calcified aortic sinuses. The "cylinder within a cylinder" implantation technique was used. Twenty-seven patients received coronary grafts, and 3 had mitral repair. All patients were studied echocardiographically during week 1 and 41 were studied at 6 months. Median ischemic time for isolated aortic valve replacement was 44 minutes. There were four hospital deaths, none valve related. No patient had more than trivial aortic regurgitation. Mean systolic gradients for valve sizes 21 to 25 mm fell significantly with time (p < or = 0.05) due to remodeling of the porcine root and early regression of left ventricular hypertrophy. Late hemodynamic function was equivalent to an aortic homograft. The Freestyle valve is easily implanted and has excellent hemodynamics. Transvalvular gradients decrease progressively.
    No preview · Article · Jan 1996 · The Annals of Thoracic Surgery
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    ABSTRACT: We performed aortic valve replacement with the Free-style stentless xenograft in 55 consecutive patients requiring a bioprosthesis. Thirty-four were male and 21 female, and all were in New York Heart Association class III to V. Ages ranged from 44 to 87 years (median, 74 years). Fifteen patients required coronary bypass grafts. One required mitral valve replacement (after attempted repair) and another needed repair of both the mitral and tricuspid valves. Four were reoperations. Implantation involved two-thirds transection at the aortic sinotubular junction and insertion of the xenograft cylinder into the aortic sinuses. Ischemic times ranged from 34 to 58 minutes for isolated aortic valve replacement and up to 79 minutes for aortic plus mitral valve replacement. Two patients died in the hospital of left ventricular failure. Survivors underwent echocardiographic assessment of systolic gradients. The mean gradients for valve sizes of 21, 23, 25, and 27 cm were 13, 10, 8, and 6.5 mm Hg, respectively. No patient had more than trivial regurgitation. One died late of left ventricular failure. The Free-style stentless xenograft is user friendly and can be employed in a calcified root. The "cylinder within a cylinder" method is simple and reproducible and avoids aortic regurgitation. Follow-up has shown excellent hemodynamic function and decreasing gradients.
    No preview · Article · Sep 1995 · The Annals of Thoracic Surgery
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    ABSTRACT: Stentless porcine aortic valves demonstrate superior hemodynamic performance when compared with their stented counterparts. The technical considerations for implanting these valves can be demanding. The Medtronic Freestyle aortic root bioprosthesis resembles an allograft, has zero-pressure-fixed leaflets treated with an antimineralization agent, and can be implanted using a variety of techniques. In this study of that valve, total root replacement (TRR) was compared with a partial scallop aortic inclusion technique (PSI). Implications were performed in 75 patients (49 PSI and 26 TRR). There were no significant differences with respect to age, sex, or incidence of concomitant procedures. Mean aortic cross-clamp times were significantly less in the PSI group than in the TRR group (51.8 +/- 11.7 minutes versus 125.5 +/- 19.7 minutes; p = 0.0001). At discharge, mean systolic gradients seen on color-flow Doppler echocardiography were less in the TRR group than in the PSI group (6.17 +/- 3.66 versus 10.01 +/- 4.83 mm Hg; p = 0.014). Discharge echocardiography revealed trivial valve regurgitation in 8.3% of the TRR group and in 41.7% of the PSI group (p = 0.004). No patient experienced any significant valvular regurgitation on discharge echocardiography. We conclude that early experience with the Medtronic Freestyle aortic root bioprosthesis shows excellent short-term function regardless of implantation technique. Shorter cross-clamp times, comparable with those of stented valve procedures, occurred with PSI implantation. We anticipate that effects on long-term durability will be beneficial.
    No preview · Article · May 1995 · The Annals of Thoracic Surgery
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    ABSTRACT: Tissue valve degeneration has been variably attributed to preservation and fixation methods. Additionally, a rigid valve ring might contribute to valve failure. The use of a nonstented porcine valve in the aortic position has clear hemodynamic advantages, and the lack of a stent may favorably influence long-term function. We have implanted stentless aortic valves (Prima valve) in 31 patients. There were 17 men. The mean age was 71.5 years (range, 50 to 83 years). After sculpturing of the sinuses the valve is positioned below the coronary arteries. Valve sizes ranged from 19 to 27 mm. There were no early or late deaths. Mean follow-up to date is 8.9 months (range, 4 weeks to 15 months). Early hemodynamic follow-up using Doppler echocardiography shows average peak systolic and mean gradients of 20.4 mm Hg and 8.6 mm Hg, respectively, at 4 weeks in 26 patients, with no significant change in 13 patients at 6 months. All patients are currently in New York Heart Association class I or II. Our early experience of stentless aortic valves shows them to be reliable with a satisfactory early hemodynamic profile. Their use in the elderly may conserve homografts for children and the young.
    No preview · Article · Aug 1993 · The Annals of Thoracic Surgery