Ann Thorac Surg 2002;73:1836
© 2002 The Society of Thoracic Surgeons
Original article: cardiovascular
Invited commentary
W.R. Eric Jamieson, MDa
a St. Paul’s Hospital, 1081 Burrard St, Vancouver, BC V6Z 1Y6, Canada
e-mail: wrej{at}interchange.ubc.ca
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 Introduction
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The optimization of hemodynamic performance of aortic valve replacement substitutes is of paramount importance to surgeons, cardiologists, and industry as we gain more knowledge of the influence of exercise and the potential effects of inadequate left ventricular mass regression on survival. The authors have conducted a prospective hemodynamic evaluation of the St. Jude Medical Regent mechanical prosthesis designed to provide optimal hemodynamics. The study was conducted with 40 patients between March 2000 and July 2001.
The prosthesis design, to facilitate hemodynamic performance, is incompletely described in the article. The mechanical components of all St. Jude Medical prostheses are the same, except for rotatable configurations of the Masters and Regent series. The development of the St. Jude Medical mechanical prostheses has led to a progressively greater geometric orifice, while maintaining the same tissue annulus dimension. In the standard cuff of the St. Jude Medical prosthesis, part of the cuff fabric is intraannular, whereas in the HP series prosthesis, the fabric has been shifted to an entirely supraannular position. The St. Jude Medical Regent prosthesis shifts the carbon rim from intraannular to entirely supraannular.
Prosthesis–patient mismatch is avoided if the effective orifice area index (EOAI) is greater than or equal to 0.85 cm2/m2. The prosthesis performed optimally at all valve sizes with the EOAI at 1 year being greater than 0.85 cm2/m2. The authors sized the annulus intraoperatively with a Hegar dilator and found the mean annulus size to be no different from the mean valve size. The supraannular noneverting implantation technique used by the authors provides favorable hemodynamic performance. The mean gradients reduced over time but remained between 12 and 18 Hg, as do stented heterograft bioprostheses, as compared to stentless heterograft bioprostheses which have more physiological gradients. At 1 year, the left ventricular mass index did not reach normal gender values (males 130 g/m2 and females 110 g/m2). This may be related to the fact that only 9 of the 40 patients were available for an assessment after 1 year, as patient accrual was only completed in July 2001.
The surgeon has the responsibility for selecting the optimal prosthesis for each patient, whether biological or mechanical. Pibarot and Dumesnil (J Am Coll Cardiol 2000;36:1131–41) have proposed a three-step process to avoid patient–prosthesis mismatch. The desired minimal EOAI can be determined with the knowledge of body surface area, intraannular measurement (as conducted by the authors) or echocardiographic-derived left ventricular outflow track dimension, and the manufacturer’s prosthesis in vitro EOA by valve size. The stented in vitro values usually overestimate in vivo values by 10% to 15%. On the other hand, stentless valves in vitro values of EOA grossly overestimate in vivo values. Mechanical prostheses tend to have larger EOAs than stented bioprostheses, and in vivo EOAs for mechanical prostheses may be underestimated by Doppler echocardiography. The surgeon may consider the acceptable EOAI for any specific patient to range from greater than 0.75 cm2/m2 to 1.0 cm2/m2, depending on the activity level and age of the patient. Most manufacturers produce a hemodynamically favorable mechanical prosthesis; the St. Jude Medical Regent is one of these prostheses.
