The Carpentier-Edwards Perimount Magna aortic xenograft: a new design with an improved hemodynamic performance
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《血管的通路杂志》
a Department of Cardiac Surgery, Salamanca University Hospital, Paseo de San Vicente 58-182, 37007 Salamanca, Spain
b Department of Cardiology, Salamanca University Hospital, Paseo de San Vicente 58-182, 37007 Salamanca, Spain
Presented at the 19th Annual Meeting of the European Association for Cardio-Thoracic Surgery and the 13th Annual Meeting of the European Society of Thoracic Surgeons, Barcelona, Spain, September 25–28, 2005.
Abstract
This study compares the implantation characteristics and the hemodynamic performance of the new Carpentier-Edwards Perimount Magna (CEPM) xenograft with those of the standard Perimount (CEPS) valve in the aortic position. Eighty consecutive patients surviving an aortic valve replacement with either the CEPS valve (n=40) or the CEPM prosthesis (n=40) in the supra-annular position were retrospectively reviewed. One year follow-up was complete and hemodynamic performance assessed by Doppler echocardiography. The mean valve size implanted was 21.3±1.7 mm (CEPS) vs. 22.2±1.8 mm (CEPM). The average mean pressure gradient was 13.6±5.1 mmHg in the CEPS group and 9.6±3.3 mmHg in the CEPM group (P<0.0001). Mean and peak gradients were slightly lower and the effective orifice areas (EOA) were larger for the Magna prosthesis than for the comparable standard valves: 19 mm (1.58±0.2 vs. 1.28±0.1 cm2), 21 mm (1.90±0.4 vs. 1.69±0.4 cm2), 23 mm (2.07±0.3 vs. 1.86±0.3 cm2), 25 mm (2.30±0.1 vs. 1.89±0.5 cm2). The average indexed EOA was statistically different between groups (CEPS 0.98±0.21 cm2/m2 vs. CEPM 1.20±0.25 cm2/m2). Patient-prosthesis mismatch (indexed EOA0.85 cm2/m2) was present in 40.7% (CEPS) vs. 16.6% (CEPM) of the patients with valve sizes 21 mm. Our study demonstrates that the Magna prosthesis significantly reduces the incidence of patient-prosthesis mismatch when compared to the standard Perimount valve in the aortic position.
Key Words: Aortic valve replacement; Tissue valves; Hemodynamic performance
1. Introduction
Recent practices in aortic valve replacement (AVR) have seen an increasing use of biological valve substitutes because of the growing proportion of elderly patients requiring surgery. In addition, the hemodynamic performance of aortic substitutes is receiving renewed interest due to the influence of patient-prosthesis mismatch (PPM) on left ventricular mass regression and clinical outcome after AVR [1,2].
The Carpentier-Edwards Perimount standard (CEPS) aortic tissue valve (Edwards Lifesciences LLC, Irvine, CA) has been in clinical use since 1981 and its long-term clinical and hemodynamic results have been reported to be excellent [3]. Introduced in 2002, the Carpentier-Edwards Perimount Magna (CEPM) aortic xenograft is a modification of the CEPS valve. Firstly, the width of the sewing ring has been significantly reduced so that the external diameter is 2 mm smaller than the corresponding CEPS valve. Secondly, the sewing cuff has been displaced upstream, so both sewing cuff and leaflets remain in a complete supra-annular position, thus achieving a maximal clearance of the aortic valve orifice. Thirdly, the sewing cuff is more flexible and scalloped, thereby facilitating the valve seating and decreasing the risk of dehiscence. Although all these modifications should improve the hemodynamic performance of the CEPS valve, no comparative data have been reported thus far.
The aim of our study was to define the one-year hemodynamic performance of the new CEPM xenograft and to compare it with that of the well established CEPS valve.
2. Patients and methods
The medical records of 80 consecutive patients (43 men and 37 women) surviving an AVR with either the CEPS or the CEPM valves between March 2002 and December 2004 were retrospectively reviewed. The CEPM prosthesis was introduced at our institution in April 2003, thus the first 40 patients receiving the new CEPM valve were compared with the last 40 consecutive patients who received the CEPS model. Patients undergoing an isolated AVR or those requiring AVR associated to aortocoronary bypass grafting, ascending aortic surgery or tricuspid annuloplasty were included in the study.
Operations were performed through a complete median sternotomy using standard cardiopulmonary bypass techniques, including mild systemic hypothermia and antegrade and retrograde cold blood cardioplegia. After excision of the native aortic valve the annulus was measured with the corresponding sizer provided by the manufacturer (model 1161 for the CEPS and 1130 for the CEPM). The prosthesis size was determined by the largest sizer whose lower cylindrical portion comfortably fitted into the annulus. No attempts to oversize the valves were made in any patient. All valves were implanted in the supra-annular position using interrupted mattressed, pledgeted 2-0 Ticron sutures. No patients underwent annular enlargement procedures.
All patients were followed up by transthoracic Doppler echocardiography one year after the operation (mean 11±2.5 months). Echocardiography was performed using a Hewlett-Packard Sonos 5.500 ultrasound imaging system, with a 2.5-MHz phased array transducer (Hewlett-Packard, Inc, Andover, MA). The modified Bernoulli equation was used to calculate the peak and mean pressure gradients across the valve. Left ventricular outflow tract (LVOT) area was calculated by measuring the diameter (D) of the LVOT and assuming a circular shape (ALVOT=D2/4). Effective orifice area (EOA) was calculated by the continuity equation using the time velocity integral (TVI) of LVOT velocity (VLVOT, by pulsed-wave Doppler) and prosthetic valve velocity (VAo, by continuous-wave Doppler): EOA=ALVOT (TVILVOT/TVIAo). The postoperative EOAs of the aortic prosthesis were then indexed (IEOA) to the body surface area to assess the presence of patient-prosthesis mismatch (PPM). A significant PPM was defined by IEOA 0.85 cm2/m2.
The SPSS 11.0 for Windows (SPSS, Chicago, IL) program was used for statistical analysis. The continuous variables were expressed as mean values±S.D. and compared using a t-test and the Mann-Whitney U-test as indicated. Nominal data are presented as frequencies and percentages and compared by Pearson's 2 test with continuity correction or 2-sided Fisher exact test as appropriate. Statistical significance was defined as a P-value <0.05. The relationships between the Doppler variables and prosthesis size were evaluated by simple linear regression analysis (Pearson's correlation coefficient).
3. Results
Preoperative clinical characteristics were comparable in the two groups (Table 1). The number of implanted valves, with regards to valve type and labeled valve size, as well as surgical details are shown in Table 2. Although both groups showed a similar average BSA, gender distribution and aortic valve lesions, there was a tendency to implant larger prostheses in patients of the CEPM group than those of the CEPS one. In fact, 67.5% of the patients in the CEPS group received either a 19 or 21 mm valve whereas this percentage was 45% in the CEPM group. Operative and postoperative outcomes were similar in both groups.
3.1. Hemodynamic measurements
Comparison of the CEPS and CEPM prostheses with respect to peak velocity and peak and mean transvalvular pressure gradients are listed in Table 3. Overall, patients with a CEPM prosthesis showed significantly lower peak velocity and peak and mean transvalvular gradients (P<0.0001) than those with a CEPS valve. Peak velocity and transvalvular gradients were lower in the CEPM group for each valve size. This difference was statistically significant for the 21 mm (P=0.050) and 23 mm valves (P=0.036). Comparative parameters regarding valvular areas are shown in Table 4. The average EOA for all valve sizes was significantly larger in the CEPM group. This difference was mainly due to the larger EOA of 19 mm valves. Overall, the average IEOA was significantly higher (P<0.0001) in the Magna group (CEPS 0.98±0.21 cm2/m2 vs. CEPM 1.20±0.25 cm2/m2). When comparing individual valve sizes, there was a significant difference in favor of the 19 mm, 21 mm and 23 mm CEPM prostheses (P=0.02, P=0.05, P=0.05).
The prevalence of significant PPM was different according to the type and size of the implanted prosthesis. Overall, 30% of patients with a CEPS valve had an IEOA 0.85 cm2/m2 whereas this occurs in 10% of those with a CEPM valve (P<0.05). Significant PPM was especially frequent in patients with 19 mm valve size and its incidence clearly decreased as prosthetic size increased (Fig. 1).
There was a significant correlation between the size of the prosthesis and the mean transvalvular pressure gradient in either group (CEPS r=–0.282, P=0.03; CEPM r=–0.276, P=0.04). The EOA was also statistically related to the size of the prosthesis in the global group and in both subgroups (CEPS group, r=0.497, P=0.001; CEPM group, r=0.523, P<0.0001) (Fig. 2).
4. Discussion
The primary purpose of AVR is to restore an unimpeded ventricular ejection thus favoring the regression of left ventricular (LV) hypertrophy. For this purpose the hemodynamic performance of aortic prostheses is of paramount importance. A valve prosthesis that is too small is not able to accommodate the cardiac output, especially under conditions of hemodynamic stress. PPM after AVR is a frequent problem that is reflected by high transvalvular gradients through otherwise normally functioning valves [4,5]. It is responsible for an incomplete LV mass regression [6,7], a phenomenon clearly associated with a negative effect on intermediate and long-term survival [5,8,9]. Significant PPM has been associated with increased operative mortality, less symptomatic improvement and decreased long-term survival [1,2,5,8,9]. Nevertheless, as the true incidence of PPM and its importance in terms of survival and quality of life is still controversial [10], long term clinical outcomes are necessary.
Despite the continuous improvement in tissue manufacturing and valve design, most contemporary aortic tissue valves generate transvalvular gradients in varying degrees. This is due to the obstructive nature of the leaflets themselves, sewing ring and valve stents.
The CEPS is a second generation xenograft and many studies have shown excellent long-term hemodynamic and clinical results [3], even in small valve sizes [13] and also when compared with stentless prostheses [11,12]. The new CEPM aortic xenograft was designed to provide a superior hemodynamic performance. By reducing the sewing ring, manufacturers sought to enable the implantation of a one size larger prosthesis than with the standard model. A larger valve size meant a larger internal diameter within the same native aortic annulus thus reducing the probability of PPM.
The current study compared the implantation characteristics and the one-year hemodynamic performance of both Perimount valve models. Although we did not attempt to oversize the CEPM prosthesis, patients in this group received a slighty larger valve compared to those receiving a CEPS. The mean valve size implanted in the CEPM group was 22.2±1.8 mm and 21.3±1.7 mm in the CEPS group (P=0.03). This fact probably reflects the surgeon's confidence to select the larger CEPM valve in those patients whose anatomical annular diameter do not correspond exactly to any sizer diameter. However, a real larger aortic annular diameter in the CEPM group could not be discarded.
Our study supports the improved hemodynamic performance of the CEPM. The improved internal orifice to external diameter ratio results in a reduction of transvalvular gradients with the Magna prosthesis. Both peak and mean pressure gradients were significantly lower for the CEPM prosthesis (P<0.0001), particulary in valve sizes 21 and 23 mm. EOA has been consistently good in both groups, even in small valve sizes. These findings correlated closely with those reported by other investigators [14]. Although the internal orifice diameters of both prostheses did not differ between labeled valve size, our data clearly show an increase in EOA with the CEPM valves, reaching statistical significance when comparing the entire groups and in patients with 19 mm valve sizes.
In the current study, echocardiographic quantification of IEOA has been employed to define PPM. Nowadays, the IEOA is the only valid parameter that identifies PPM [15]. The definition of PPM based on the indexed internal geometric area and calculated from the anatomically measured internal diameter of the prosthesis may overestimate EOA in varying degrees, depending on prosthesis type, size and geometry [15]. Many studies, in which the performance of different aortic prostheses was evaluated, have emphasized that successful AVR should achieve an IEOA0.9 cm2/m2 in order to minimize prosthetic gradients and to favor LV mass regression [1,6,7]. The prevalence of PPM has been found in up to 52% of the patients with a stented aortic bioprosthesis, especially in those with small valve sizes [5,7].
The incidence of PPM found in our patients with valve sizes <21 mm was 17% for the CEPM and 42% for the CEPS, figures that are lower than those reported in other studies on the CEPS [6,14]. However, the average BSA in our study population was rather small, less than 1.7 cm2 in both groups of patients, a circumstance that could partly explain the above findings. Regarding IEOA, our study clearly showed a significant difference between both prostheses in favor of the CEPM valves. Particulary, there was a significant superiority of the 19, 21 and 23 mm Magna prostheses when compared to the standard model. For this reason, the use of a CEPM valve may contribute to reducing the incidence of PPM, especially in patients with small aortic annulus.
In both groups there was a clear correlation between valve size and hemodynamic parameters. As expected, the mean pressure gradients decreased and the EOA increased with increasing prosthesis size. Therefore, the largest possible size should be implanted to achieve superior hemodynamics.
Nevertheless this investigation has a number of limitations. Firstly, it was a retrospective study susceptible to various sources of bias, although both groups were comparable according to age, BSA, gender distribution and other characteristics. Secondly, the average body size of our patients in both groups was rather small, which may have influenced the low incidence of PPM. Finally, the small number of patients in some valve size groups may have been responsible for the absence of statistical differences between groups.
In conclusion, our study supports that the hemodynamic outcomes of the CEPM prosthesis are substantially better than those of the standard model. The CEPM prosthesis significantly reduces the incidence of PPM when compared to the standard Perimount valve. The improved hemodynamic characteristics of the CEPM xenograft makes it ideal for use in patients with small aortic annulus.
Appendix. Conference discussion
Dr R. Lorusso (Brescia, Italy): I would like to ask you one thing regarding the hemodynamic performance, particularly of the 19 size because you really showed that you had major effective orifice area either absolute or indexed, but you didn't have a better hemodynamic performance. There was no difference between the two groups according to the mean or the peak gradients in the 19-size group.
Dr Dalmau: Yes, there was no significant difference in the mean and peak gradients. But index of effective orifice area was also lower for the Magna prosthesis I think. This is a clear sign that they had also better hemodynamics.
References
Pibarot P, Dumesnil JG. Hemodynamic and clinical impact of prosthesis-patient mismatch in the aortic valve position and its prevention. J Am Coll Cardiol 2000; 36:1131–1141.
Rao V, Jamieson WR, Ivanov J, Armstrong S, David TE. Prosthesis-patient mismatch affects survival after aortic valve replacement. Circulation 2000; 102:19 Supp13III-5–9.
Banbury MK, Cosgrove DM, Thomas JD, Blackstone EH, Rajeswaran J, Okies E, Frater RM. Hemodynamic stability during 17 years of the Carpentier-Edwards aortic pericardial bioprosthesis. Ann Thorac Surg 2002; 73:1460–1465.
Pibarot P, Honos GN, Durand LG, Dumesnil JG. The effect of prosthesis-patient mismatch on aortic bioprosthetic valve hemodynamic performance and patient clinical status. Can J Cardiol 1996; 12:379–387.
Pibarot P, Dumesnil JG, Lemieux M, Cartier P, Metras J, Durand LG. Impact of prosthesis–patient mismatch on hemodynamic and symptomatic status, morbidity and mortality after aortic valve replacement with a bioprosthetic heart valve. J Heart Valve Dis 1998; 7:211–218.
Tasca G, Brunelli F, Cirillo M, DallaTomba M, Mhagna Z, Troise G, Quaini E. Impact of valve prosthesis-patient mismatch on left ventricular mass regression following aortic valve replacement. Ann Thorac Surg 2005; 79:2505–510.
Del Rizzo DF, Abdoh A, Cartier P, Doty DB, Westaby S. Factors affecting left ventricular mass regression after aortic valve replacement with stentless valves. Semin Thorac Cardiovasc Surg 1999; 11:114–120.
Blais C, Dumesnil JG, Baillot R, Simard S, Doyle D, Pibarot P. Impact of valve prosthesis-patient mismatch on short-term mortality after aortic valve replacement. Circulation 2003; 108:983–988.
Fuster RG, Montero Argudo JA, Albarova OG, Sos FH, Lopez SC, Codoner MB, Buendia Minano JA, Albarran IR. Patient-prosthesis mismatch in aortic valve replacement: really tolerable. Eur J Cardiothorac Surg 2005; 27:441–449.
David TE. Is prothesis-patient mismatch a clinically relevant entity. Circulation 2005; 111:3186–3187.
Carrier M, Pellerin M, Perrault LP, Hebert Y, Page P, Cartier R, Dyrda I, Pelletier LC. Experience with the 19-mm Carpentier-Edwards pericardial bioprosthesis in the elderly. Ann Thorac Surg 2001; 71:SupplS249–252.
Doss M, Martens S, Wood JP, Aybek T, Kleine P, Wimmer Greinecker G, Moritz A. Performance of stentless versus stented aortic valve bioprostheses in the elderly patient: a prospective randomized trial. Eur J Cardiothorac Surg 2003; 23:299–304.
Cohen G, Christakis GT, Joyner CD, Morgan CD, Tamariz M, Hanayama N, Mallidi H, Szalai JP, Katic M, Rao V, Fremes SE, Goldman BS. Are stentless valves hemodynamically superior to stented valves A prospective randomized trial. Ann Thorac Surg 2002; 73:767–778.
Eichinger WB, Botzenhardt F, Keithahn A, Guenzinger R, Bleiziffer S, Wagner I, Bauernschmitt R, Lange R. Exercise hemodynamics of bovine versus porcine bioprostheses: a prospective randomized comparison of the mosaic and perimount aortic valves. J Thorac Cardiovasc Surg 2005; 129:1056–1063.
Pibarot P, Dumesnil JG, Cartier PC, Mètras J, Lemieux MD. Patient-prosthesis mismatch can be predicted at the time of operation. Ann Thorac Surg 2001; 71:SupplS265–268.(Maria Jose Dalmau, Jose M)
b Department of Cardiology, Salamanca University Hospital, Paseo de San Vicente 58-182, 37007 Salamanca, Spain
Presented at the 19th Annual Meeting of the European Association for Cardio-Thoracic Surgery and the 13th Annual Meeting of the European Society of Thoracic Surgeons, Barcelona, Spain, September 25–28, 2005.
Abstract
This study compares the implantation characteristics and the hemodynamic performance of the new Carpentier-Edwards Perimount Magna (CEPM) xenograft with those of the standard Perimount (CEPS) valve in the aortic position. Eighty consecutive patients surviving an aortic valve replacement with either the CEPS valve (n=40) or the CEPM prosthesis (n=40) in the supra-annular position were retrospectively reviewed. One year follow-up was complete and hemodynamic performance assessed by Doppler echocardiography. The mean valve size implanted was 21.3±1.7 mm (CEPS) vs. 22.2±1.8 mm (CEPM). The average mean pressure gradient was 13.6±5.1 mmHg in the CEPS group and 9.6±3.3 mmHg in the CEPM group (P<0.0001). Mean and peak gradients were slightly lower and the effective orifice areas (EOA) were larger for the Magna prosthesis than for the comparable standard valves: 19 mm (1.58±0.2 vs. 1.28±0.1 cm2), 21 mm (1.90±0.4 vs. 1.69±0.4 cm2), 23 mm (2.07±0.3 vs. 1.86±0.3 cm2), 25 mm (2.30±0.1 vs. 1.89±0.5 cm2). The average indexed EOA was statistically different between groups (CEPS 0.98±0.21 cm2/m2 vs. CEPM 1.20±0.25 cm2/m2). Patient-prosthesis mismatch (indexed EOA0.85 cm2/m2) was present in 40.7% (CEPS) vs. 16.6% (CEPM) of the patients with valve sizes 21 mm. Our study demonstrates that the Magna prosthesis significantly reduces the incidence of patient-prosthesis mismatch when compared to the standard Perimount valve in the aortic position.
Key Words: Aortic valve replacement; Tissue valves; Hemodynamic performance
1. Introduction
Recent practices in aortic valve replacement (AVR) have seen an increasing use of biological valve substitutes because of the growing proportion of elderly patients requiring surgery. In addition, the hemodynamic performance of aortic substitutes is receiving renewed interest due to the influence of patient-prosthesis mismatch (PPM) on left ventricular mass regression and clinical outcome after AVR [1,2].
The Carpentier-Edwards Perimount standard (CEPS) aortic tissue valve (Edwards Lifesciences LLC, Irvine, CA) has been in clinical use since 1981 and its long-term clinical and hemodynamic results have been reported to be excellent [3]. Introduced in 2002, the Carpentier-Edwards Perimount Magna (CEPM) aortic xenograft is a modification of the CEPS valve. Firstly, the width of the sewing ring has been significantly reduced so that the external diameter is 2 mm smaller than the corresponding CEPS valve. Secondly, the sewing cuff has been displaced upstream, so both sewing cuff and leaflets remain in a complete supra-annular position, thus achieving a maximal clearance of the aortic valve orifice. Thirdly, the sewing cuff is more flexible and scalloped, thereby facilitating the valve seating and decreasing the risk of dehiscence. Although all these modifications should improve the hemodynamic performance of the CEPS valve, no comparative data have been reported thus far.
The aim of our study was to define the one-year hemodynamic performance of the new CEPM xenograft and to compare it with that of the well established CEPS valve.
2. Patients and methods
The medical records of 80 consecutive patients (43 men and 37 women) surviving an AVR with either the CEPS or the CEPM valves between March 2002 and December 2004 were retrospectively reviewed. The CEPM prosthesis was introduced at our institution in April 2003, thus the first 40 patients receiving the new CEPM valve were compared with the last 40 consecutive patients who received the CEPS model. Patients undergoing an isolated AVR or those requiring AVR associated to aortocoronary bypass grafting, ascending aortic surgery or tricuspid annuloplasty were included in the study.
Operations were performed through a complete median sternotomy using standard cardiopulmonary bypass techniques, including mild systemic hypothermia and antegrade and retrograde cold blood cardioplegia. After excision of the native aortic valve the annulus was measured with the corresponding sizer provided by the manufacturer (model 1161 for the CEPS and 1130 for the CEPM). The prosthesis size was determined by the largest sizer whose lower cylindrical portion comfortably fitted into the annulus. No attempts to oversize the valves were made in any patient. All valves were implanted in the supra-annular position using interrupted mattressed, pledgeted 2-0 Ticron sutures. No patients underwent annular enlargement procedures.
All patients were followed up by transthoracic Doppler echocardiography one year after the operation (mean 11±2.5 months). Echocardiography was performed using a Hewlett-Packard Sonos 5.500 ultrasound imaging system, with a 2.5-MHz phased array transducer (Hewlett-Packard, Inc, Andover, MA). The modified Bernoulli equation was used to calculate the peak and mean pressure gradients across the valve. Left ventricular outflow tract (LVOT) area was calculated by measuring the diameter (D) of the LVOT and assuming a circular shape (ALVOT=D2/4). Effective orifice area (EOA) was calculated by the continuity equation using the time velocity integral (TVI) of LVOT velocity (VLVOT, by pulsed-wave Doppler) and prosthetic valve velocity (VAo, by continuous-wave Doppler): EOA=ALVOT (TVILVOT/TVIAo). The postoperative EOAs of the aortic prosthesis were then indexed (IEOA) to the body surface area to assess the presence of patient-prosthesis mismatch (PPM). A significant PPM was defined by IEOA 0.85 cm2/m2.
The SPSS 11.0 for Windows (SPSS, Chicago, IL) program was used for statistical analysis. The continuous variables were expressed as mean values±S.D. and compared using a t-test and the Mann-Whitney U-test as indicated. Nominal data are presented as frequencies and percentages and compared by Pearson's 2 test with continuity correction or 2-sided Fisher exact test as appropriate. Statistical significance was defined as a P-value <0.05. The relationships between the Doppler variables and prosthesis size were evaluated by simple linear regression analysis (Pearson's correlation coefficient).
3. Results
Preoperative clinical characteristics were comparable in the two groups (Table 1). The number of implanted valves, with regards to valve type and labeled valve size, as well as surgical details are shown in Table 2. Although both groups showed a similar average BSA, gender distribution and aortic valve lesions, there was a tendency to implant larger prostheses in patients of the CEPM group than those of the CEPS one. In fact, 67.5% of the patients in the CEPS group received either a 19 or 21 mm valve whereas this percentage was 45% in the CEPM group. Operative and postoperative outcomes were similar in both groups.
3.1. Hemodynamic measurements
Comparison of the CEPS and CEPM prostheses with respect to peak velocity and peak and mean transvalvular pressure gradients are listed in Table 3. Overall, patients with a CEPM prosthesis showed significantly lower peak velocity and peak and mean transvalvular gradients (P<0.0001) than those with a CEPS valve. Peak velocity and transvalvular gradients were lower in the CEPM group for each valve size. This difference was statistically significant for the 21 mm (P=0.050) and 23 mm valves (P=0.036). Comparative parameters regarding valvular areas are shown in Table 4. The average EOA for all valve sizes was significantly larger in the CEPM group. This difference was mainly due to the larger EOA of 19 mm valves. Overall, the average IEOA was significantly higher (P<0.0001) in the Magna group (CEPS 0.98±0.21 cm2/m2 vs. CEPM 1.20±0.25 cm2/m2). When comparing individual valve sizes, there was a significant difference in favor of the 19 mm, 21 mm and 23 mm CEPM prostheses (P=0.02, P=0.05, P=0.05).
The prevalence of significant PPM was different according to the type and size of the implanted prosthesis. Overall, 30% of patients with a CEPS valve had an IEOA 0.85 cm2/m2 whereas this occurs in 10% of those with a CEPM valve (P<0.05). Significant PPM was especially frequent in patients with 19 mm valve size and its incidence clearly decreased as prosthetic size increased (Fig. 1).
There was a significant correlation between the size of the prosthesis and the mean transvalvular pressure gradient in either group (CEPS r=–0.282, P=0.03; CEPM r=–0.276, P=0.04). The EOA was also statistically related to the size of the prosthesis in the global group and in both subgroups (CEPS group, r=0.497, P=0.001; CEPM group, r=0.523, P<0.0001) (Fig. 2).
4. Discussion
The primary purpose of AVR is to restore an unimpeded ventricular ejection thus favoring the regression of left ventricular (LV) hypertrophy. For this purpose the hemodynamic performance of aortic prostheses is of paramount importance. A valve prosthesis that is too small is not able to accommodate the cardiac output, especially under conditions of hemodynamic stress. PPM after AVR is a frequent problem that is reflected by high transvalvular gradients through otherwise normally functioning valves [4,5]. It is responsible for an incomplete LV mass regression [6,7], a phenomenon clearly associated with a negative effect on intermediate and long-term survival [5,8,9]. Significant PPM has been associated with increased operative mortality, less symptomatic improvement and decreased long-term survival [1,2,5,8,9]. Nevertheless, as the true incidence of PPM and its importance in terms of survival and quality of life is still controversial [10], long term clinical outcomes are necessary.
Despite the continuous improvement in tissue manufacturing and valve design, most contemporary aortic tissue valves generate transvalvular gradients in varying degrees. This is due to the obstructive nature of the leaflets themselves, sewing ring and valve stents.
The CEPS is a second generation xenograft and many studies have shown excellent long-term hemodynamic and clinical results [3], even in small valve sizes [13] and also when compared with stentless prostheses [11,12]. The new CEPM aortic xenograft was designed to provide a superior hemodynamic performance. By reducing the sewing ring, manufacturers sought to enable the implantation of a one size larger prosthesis than with the standard model. A larger valve size meant a larger internal diameter within the same native aortic annulus thus reducing the probability of PPM.
The current study compared the implantation characteristics and the one-year hemodynamic performance of both Perimount valve models. Although we did not attempt to oversize the CEPM prosthesis, patients in this group received a slighty larger valve compared to those receiving a CEPS. The mean valve size implanted in the CEPM group was 22.2±1.8 mm and 21.3±1.7 mm in the CEPS group (P=0.03). This fact probably reflects the surgeon's confidence to select the larger CEPM valve in those patients whose anatomical annular diameter do not correspond exactly to any sizer diameter. However, a real larger aortic annular diameter in the CEPM group could not be discarded.
Our study supports the improved hemodynamic performance of the CEPM. The improved internal orifice to external diameter ratio results in a reduction of transvalvular gradients with the Magna prosthesis. Both peak and mean pressure gradients were significantly lower for the CEPM prosthesis (P<0.0001), particulary in valve sizes 21 and 23 mm. EOA has been consistently good in both groups, even in small valve sizes. These findings correlated closely with those reported by other investigators [14]. Although the internal orifice diameters of both prostheses did not differ between labeled valve size, our data clearly show an increase in EOA with the CEPM valves, reaching statistical significance when comparing the entire groups and in patients with 19 mm valve sizes.
In the current study, echocardiographic quantification of IEOA has been employed to define PPM. Nowadays, the IEOA is the only valid parameter that identifies PPM [15]. The definition of PPM based on the indexed internal geometric area and calculated from the anatomically measured internal diameter of the prosthesis may overestimate EOA in varying degrees, depending on prosthesis type, size and geometry [15]. Many studies, in which the performance of different aortic prostheses was evaluated, have emphasized that successful AVR should achieve an IEOA0.9 cm2/m2 in order to minimize prosthetic gradients and to favor LV mass regression [1,6,7]. The prevalence of PPM has been found in up to 52% of the patients with a stented aortic bioprosthesis, especially in those with small valve sizes [5,7].
The incidence of PPM found in our patients with valve sizes <21 mm was 17% for the CEPM and 42% for the CEPS, figures that are lower than those reported in other studies on the CEPS [6,14]. However, the average BSA in our study population was rather small, less than 1.7 cm2 in both groups of patients, a circumstance that could partly explain the above findings. Regarding IEOA, our study clearly showed a significant difference between both prostheses in favor of the CEPM valves. Particulary, there was a significant superiority of the 19, 21 and 23 mm Magna prostheses when compared to the standard model. For this reason, the use of a CEPM valve may contribute to reducing the incidence of PPM, especially in patients with small aortic annulus.
In both groups there was a clear correlation between valve size and hemodynamic parameters. As expected, the mean pressure gradients decreased and the EOA increased with increasing prosthesis size. Therefore, the largest possible size should be implanted to achieve superior hemodynamics.
Nevertheless this investigation has a number of limitations. Firstly, it was a retrospective study susceptible to various sources of bias, although both groups were comparable according to age, BSA, gender distribution and other characteristics. Secondly, the average body size of our patients in both groups was rather small, which may have influenced the low incidence of PPM. Finally, the small number of patients in some valve size groups may have been responsible for the absence of statistical differences between groups.
In conclusion, our study supports that the hemodynamic outcomes of the CEPM prosthesis are substantially better than those of the standard model. The CEPM prosthesis significantly reduces the incidence of PPM when compared to the standard Perimount valve. The improved hemodynamic characteristics of the CEPM xenograft makes it ideal for use in patients with small aortic annulus.
Appendix. Conference discussion
Dr R. Lorusso (Brescia, Italy): I would like to ask you one thing regarding the hemodynamic performance, particularly of the 19 size because you really showed that you had major effective orifice area either absolute or indexed, but you didn't have a better hemodynamic performance. There was no difference between the two groups according to the mean or the peak gradients in the 19-size group.
Dr Dalmau: Yes, there was no significant difference in the mean and peak gradients. But index of effective orifice area was also lower for the Magna prosthesis I think. This is a clear sign that they had also better hemodynamics.
References
Pibarot P, Dumesnil JG. Hemodynamic and clinical impact of prosthesis-patient mismatch in the aortic valve position and its prevention. J Am Coll Cardiol 2000; 36:1131–1141.
Rao V, Jamieson WR, Ivanov J, Armstrong S, David TE. Prosthesis-patient mismatch affects survival after aortic valve replacement. Circulation 2000; 102:19 Supp13III-5–9.
Banbury MK, Cosgrove DM, Thomas JD, Blackstone EH, Rajeswaran J, Okies E, Frater RM. Hemodynamic stability during 17 years of the Carpentier-Edwards aortic pericardial bioprosthesis. Ann Thorac Surg 2002; 73:1460–1465.
Pibarot P, Honos GN, Durand LG, Dumesnil JG. The effect of prosthesis-patient mismatch on aortic bioprosthetic valve hemodynamic performance and patient clinical status. Can J Cardiol 1996; 12:379–387.
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