ECHOCARDIOGRAPHIC HEMODYNAMIC ASSESSMENT OF STENTLESS AND SUPERSTENTLESS AORTIC BIOPROSTHESES IN TERMS OF SURVIVAL ADVANTAGE
Authors: Sokol. I. 
Published: February 2004

Porcine xenografts as stentless and recently superstentless bioprosthetic aortic valves are anticipated to cause improved hemodynamics and increase longevity over stented bioprostheses. Stentless valves showed extremely good flow characteristics. Durability has been reported to be better than in stented xenografts accompanied by low gradients, rare and only trivial aortic valve regurgitation. As during the last years the well‐known and attractive aortic bioprostheses stentless St. Jude Toronto SPV and superstentless Shelhigh were often used all over the world including in our institute, we will present their morphologic and functional assessment. Toronto SPV prosthesis requires two suture lines to be implanted. The first row of sutures is between the left ventricular outflow tract and inflow of the valve and the second between the aortic sinuses and the valve. The subcoronary technique of the implantation is intraannular with aortic root as a stent. The diameter of sinotubular junction during diastole is crucial for valve competence and when it exceeds the diameter of the aortic annulus by more than 3 mm, the root is dilated and this valve should not be used. At the completion of the implantation of the valve, the sinotubular junction should not exceed the diameter of the valve. On the contrary, Shelhigh superstentless bioprosthetic aortic valves require one suture line and no sutures are needed in the vicinitiy of the coronary arteries (which might also distort the base of the valve). A composite valve mounted on a superflexible ring has three separate cusps, which allow the best hemodynamic characteristics. Valve implantation is easy with mini or total root replacement and with the possibillity of oversizing the valve conduit by one to three sizes enhancing the hemodynamic advantages.

A complete echocardiographic examination included the estimation of maximal and mean transvalvular gradients from transthoracic 5‐chamber view or transesophageal transgaastric view, as well as calculations of effective orifice area by the continuity equation or with planimetry in transesophageal short axis view, especially in the cases of aortic regurgitation. Effective orifice area index, a predictable measure of patient–prosthesis mismatch was calculated at the time of operation or postopertively. Aortic prosthesis valve regurgitation was recorded by pulsed and color Doppler. Left ventricular size, systolic and diastolic function are important clues regarding the severity of regurgitation. Transesophageal assessment of the structure and function of the bioprosthetic stentless valves in short and longitudinal axis provides the evaluation of clinical performance. Measurement of left ventricular mass after aortic valve replacement with both bioprosthetic stentless valves has been done by the truncated ellipse method. Twenty‐eight patients undergoing aortic valve replacement were assigned to receive either Toronto stentless or Shelhigh superstentles aortic valve. Transthoracic and transesophageal echocardiograms were performed after 1 week, 3 months and 6 months, postoperatively. We found maximal systolic transvalvular gradients ranged from 18 to 26 mmHg and mean systolic transvalvular gradients from 8.5 to 12 mmHg with effective orifice area from 1.5 to 2.1cm2 without significantly changes in both groups. Thesegradients after 3 and 6 months postoperatively dropped more in the Toronto stentless group, but not significantly hemodinamicly in relation to Shelhigh superstentles group, and the effective orifice area ranged in both groups from 2.4 to 2.8 cm2. Left ventricular mass had fallen in both groups but the degree of mass reduction was comparable. Diastolic function has significantly improved in both groups. In conclusion,we had only trivial regurgitation in two cases of Toronto stentless group. Stentless bioprostheses convey hemodynamically and possibly survival benefit through a low incidence of valve‐related complications. Owing to more recent developments of stentless technology with the most advanced anticalcification treatment and superior hemodynamic performance due to maintenance of the normal aortic physiology and flexibility of the aortic root, it is felt that these valves could last 15 years or longer.They will probably provide a useful alternative to aortic homografts in the future.