Clinical study of prosthesis-patient mismatch after aortic valve replacement

Abstract

Objective The prosthesis used for aortic valve replacement (AVR) may be too small in relation to the body size, thus causing valve prosthesis-patient mismatch (PPM) and abnormally high transvalvular pressure gradients. The aim of this study was to evaluate the prevalence of PPM and the impact of PPM on hemodynamic and early mortality after AVR. Methods A total of 292 patients ( 167 males, 125 females; mean age of ( 52.8 ± 14.6 ) years, with ranging 22 - 82 years) who underwent AVR between January 2007 and December 2009 were retrospectively evaluated. Etiologies were: rheumatic in 243 cases, degenerative in 36, congenitally bicuspid aortic valve in 8, and infective endocarditis in 5. Combined operations with AVR including mitral valve replacement ( 172 cases), mitral valve repair (56 cases), tricuspid valve repair (238 cases), and coronary artery bypass grafting (32 cases). The aortic valve prosthesis effective valve orifice area (EOA) was divided by the body surface area (BSA) to obtain the EOA index (EOAI). PPM was then defined as none or mild if EOAI was ＞0.85 cm2/m2, as moderate for 0.65 -0.85 cm2/m2 and as severe for ＜0.65 cm2/m2. The mean flow rate through aortic prostheses and mean transvalvular pressure gradients were measured by color Doppler after AVR. The prevalence of PPM was compared between the different type ( mechanical or bioprosthetic valve) and the different size ( ＞21 mm or ≤21 mm) of aortic valve prostheses. The effect of PPM on hemodynamic and early mortality after AVR was also studied. Results 219 patients received mechanical AVR and 73 bioprosthetic AVR. Moderate PPM occurs more frequently with bioprosthetic AVR (6.25% versus 48.22%, P ＜0. 01 ). Bigger than 21mm prostheses were used in 191 patients and ≤21 mm prostheses in 101 patients. The prevalence of PPM was 13.61% and 33.66% respectively ( P ＜ 0. 05 ). According to the EOAI of the aortic valve prostheses,all the 219 patients were divided into two group, PPM group and non-PPM group. The mean flow rate of aortic prostheses and mean transvalvular pressure gradients in PPM group was significantly higher than those in non-PPM group [(2.66 ± 0.87 ) m/s versus ( 1. 58 ± 0.47 ) m/s, ( 26.50 ± 6.25 ) mm Hg versus ( 16.75 ± 3.46 ) mm Hg, P ＜ 0. 01]. There were 9 deaths during early period of operation, and the total 30-day operative mortality was 3.08%. The postoperative early mortality of PPM group and non-PPM group was 6.67% and 2.16% respectively, and there were significantly difference between the two group ( P ＜ 0. 05 ). Conclusion Prosthesis-patient mismatch is common present after AVR, especially in patients with bioprostheses and small size valve prostheses. PPM has a negative impact on postoperative hemodynamic and early mortality. PPM results in higher transvalvular pressure gradients and higher early mortality. Key words: Heart valre prosthesis implantation; Heart valve, prosthesis; Cardiac surgical procedures