Assessment of the St. Jude Medical Regent Prosthetic Valve by Continuous-Wave Doppler. and dobutamine stress echocardiography

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1 Assessment of the St. Jude Medical Regent Prosthetic Valve by Continuous-Wave Doppler and Dobutamine Stress Echocardiography Akira Sezai, MD, PhD, Yuji Kasamaki, MD, PhD, Keisuke Abe, RMS, Mitsumasa Hata, MD, PhD, Hisakuni Sekino, MD, PhD, Kazuma Shimura, MD, PhD, and Kazutomo Minami, MD, PhD Departments of Cardiovascular Surgery and Cardiology, Sekino Hospital, Nihon University School of Medicine, Tokyo, Japan ADULT CARDIAC Background. The St. Jude Medical (SJM) Regent prosthetic valve (St. Paul, MN), a recently developed mechanical valve, is an improvement on the conventional SJM valve, having a wider valve area than the SJM HP valve. We evaluated this mechanical valve by Doppler echocardiography and dobutamine stress echocardiography (DSE). Methods. The functions of the SJM Regent valve were evaluated by continuous-wave Doppler echocardiography and DES in 58 cases of aortic valve replacement during a stable postoperative period. Results. The peak pressure gradient of the replaced valves sized 17, 19, 21, and 23 mm was , , , and , mm Hg respectively, and the effective orifice area index was , , , and cm 2 /m 2, respectively, with prosthesis-patient mismatch (PPM) found in 1, 3, 2, and 0 cases for the 17-, 19-, 21- and 23-mm valves, respectively, with a total incidence of 10.3%. In 20 cases, the peak pressure gradient and the effective orifice area index were significantly increased during DSE compared with those at rest. Conclusions. Although the PPM incidence was 6.6%, it was deemed from the data of DSE and clinical symptoms that there were no clinical issues for such cases of PPM in the early and intermediate phases after operation. Particularly, the effectiveness of the 17- and 19-mm valves in patients with a small aortic annulus was demonstrated, confirming the satisfactory functions of the SJM Regent prosthetic valve. (Ann Thorac Surg 2010;89:87 92) 2010 by The Society of Thoracic Surgeons Since the St. Jude Medical (SJM; St. Jude Medical Inc, St. Paul, MN) valve was introduced in 1977 as the first bileaflet mechanical valve, many reports have appeared about its durability, antithrombotic efficacy, and low level of hemolysis. It has been highly evaluated as an excellent mechanical valve based on long-term results and is the most widely used mechanical valve in the world [1 3]. The SJM valve was also used at our hospital in Japan for the first case of valve replacement (July 1978), and good clinical data have been obtained since then [1, 4, 5]. In recent years, various mechanical valves with a wide valve area have been developed for the replacement of a small aortic annulus, with which an adequately wide valve area can be secured without a surgical procedure for aortic annulus enlargement. Patient-prosthesis mismatch (PPM) does occur, however, and development of a prosthetic valve with a wider valve area has been desired. The SJM Regent valve of the present study has a wider valve area compared with conventional mechanical valves and was implanted for the first time in Japan at our facility in October 2004 [6]. The valve was considered Accepted for publication Sept 1, Address correspondence to Dr Sezai, Department of Cardiovascular Surgery, Nihon University School of Medicine, 30-1 Oyaguchi-kamimachi Itabashi-ku Tokyo, , Japan; asezai@med.nihon-u.ac.jp. an effective mechanical valve for Japanese patients, who generally have a physical constitution smaller than that of white patients. Data on the function of the SJM Regent valve after replacement are important for Japanese patients, who often have a small physique and a small aortic annulus, but it is unclear from the results to date how many patients have PPM. The objectives of the present study were to evaluate valve function by Doppler echocardiography, to detect patients with PPM, and to assess valve function under stress by performing dobutamine stress echocardiography (DSE) in patients who had undergone aortic valve replacement with an SJM Regent valve at our hospital. Patients and Methods The Ethics Committee of Nihon University School of Medicine Itabashi Hospital approved this study. Details of the study were explained to each patient, and informed consent was obtained. This study was registered with the University Hospital Medical Information Network (UMIN; Study ID: UMIN ). The study cohort consisted of 58 patients who survived for 6 months or longer among the patients who underwent aortic valve replacement with an SJM Regent valve from October 2004 to August 2008 at the Itabashi Hospital 2010 by The Society of Thoracic Surgeons /10/$36.00 Published by Elsevier Inc doi: /j.athoracsur

2 ADULT CARDIAC 88 SEZAI ET AL Ann Thorac Surg ECHOCARDIOGRAPHIC DATA OF THE SJM REGENT 2010;89:87 92 Table 1. Preoperative Patient Characteristics Variable No. or Mean SD (Range) Patients, No 58 Age, years (51 76) Gender Male 30 Female 28 Body surface area, m Diagnosis Aortic stenosis 34 Aortic regurgitation 9 Aortic stenosis and regurgitation 15 Infective endocarditis 1 Previous operations Closed mitral commissurotomy 2 Mitral valve replacement 1 Ejection fraction New York Heart Association Class II 19 Class III 28 Class IV 11 SD standard deviation. of Nihon University. Among the 60 patients who had aortic valve replacement with the SJM Regent valve, one operative death (1.7%) occurred in a patient with chronic renal failure who went into shock during dialysis and died on postoperative day 7. One patient was discharged with no postoperative complications but died of arrhythmia during the second month postoperatively. An autopsy was performed in both cases, and no abnormalities of the artificial valves were found. The 58 remaining patients, 30 men (52%) and 28 women (48%), were a mean age of years (range, 51 to 76 years), and 18 patients (31.0%) were aged older than 70 years. Their causative diseases included aortic stenosis in 34, aortic regurgitation in 9, and aortic stenosis and regurgitation in 15. Some patients had already undergone mitral valve operations, but no patient had had a previous aortic valve intervention (Table 1). The size of the prosthetic valve used was 17 mm in 4 cases, 19 mm in 16, 21 mm in 20, and 23 mm in 18. The body surface area (BSA) in cm 2 for each valve was for the 17-mm valve, for the 19-mm valve, for the 21-mm valve, and for the 23-mm valve. Concomitant procedures consisted of mitral valve replacement in 11 patients, open mitral valve commissurotomy in 1, tricuspid annuloplasty in 2, coronary artery bypass grafting in 15, and the Maze procedure in 4 (sinus rhythm was restored in all 4 patients). Aortic valve replacement was always performed in the supra-annular position. All 58 patients in were New York Heart Association functional class I postoperatively. At 6 months postoperatively, the left ventricular enddiastolic diameter (LVEDD), left ventricular end-systolic diameter (LVESD), ejection fraction (EF), and percentage of fractional shortening (%FS) were measured by transthoracic echocardiography in the LV long-axis view. The maximum blood flow through the prosthetic valve was recorded by the continuous-wave Doppler method, after which peak pressure gradient (PPG) and mean pressure gradient (MPG) were calculated using the simplified Bernoulli formula. The effective orifice area (EOA) of the valve was determined by the continuous formula and divided by the BSA to calculate the EOA index (EOAI), with 0.65 to 0.85 cm 2 /m 2 defined as mild PPM and less than 0.65 cm 2 /m 2 defined as severe PPM [7, 8]. Dobutamine stress echocardiography was performed at 6 months postoperatively in 20 patients who gave consent. Infusion of dobutamine was started at 10 g/kg/ min after obtaining baseline data on LV function and Table 2. Left Ventricular Function in Before and After Operation Valve Size Variable 17 mm 19 mm 21 mm 23 mm LVEDD, mm Pre-op a a Post-op EF Pre-op a a Post-op LVESD, mm Pre-op a a Post-op %FS Pre-op a Post-op a p EF ejection fraction; LVEDD left ventricular end-diastolic diameter; LVESD left ventricular end-systolic diameter; %FS percentage fractional shortening.

3 Ann Thorac Surg SEZAI ET AL 2010;89:87 92 ECHOCARDIOGRAPHIC DATA OF THE SJM REGENT Table 3. Valve Function in this Study and Data from Previous Reports on Each Size of the St. Jude Medical Regent Valve Valve Size No. PPG a (mm Hg) MPG a (mm Hg) EOAI a (cm 2 /m 2 ) PPM (%) 17 mm Sezai Gelsomino [9] Okamura [10] Takaseya [11] Minardi [12] mm Sezai Gelsomino [9] Bach [13] mm Sezai Gelsomino [9] Bach [13] Guenzinger [14] mm Sezai Gelsomino [9] Bach [13] Guenzinger [14] ADULT CARDIAC a Data are presented as the mean standard deviation. EOAI effective orifice area index; MPG mean pressure gradient; PPG peak pressure gradient; PPM patient-prosthesis mismatch. artificial valve function. The infusion rate was increased to 20, 30, and 40 g/kg/min at 15-minute intervals. Echocardiography was performed with a VIVID 7 model (E Yokokawa Medical Systems Co, Tokyo, Japan) at a frequency of 3.4 MHz by a specialist echocardiographer who was blinded to information about the size and type of the artificial valve. Statistical Analysis Data are presented as the mean standard deviation, and the echocardiography findings were compared by the unpaired t test. Comparison between the PPM and non-ppm groups was performed with the Fisher exact test or the unpaired t test. The level of significance was set at p All analyses were conducted with SPSS software (SPSS Inc, Chicago, IL). Results LV Function Preoperative and postoperative LV functions are summarized in Table 2. Postoperative LVEDD significantly decreased from the preoperative level for patients with the 21-mm valve (p 0.002) and the 23-mm valve (p 0.014). Postoperative LVDs also decreased from the preoperative level for patients with the 21-mm valve (p 0.007) and the 23-mm valve (p ). Postoperative EF significantly increased from the preoperative level in for cases with the 19-mm valve (p 0.026) and the 23-mm valve (p ), and postoperative % FS also increased from the baseline level for cases with the 23-mm valve (p ). Prosthetic Valve Functions Results of continuous-wave Doppler echocardiography for prosthetic valve functions are summarized in Table 3 [9 14]. The PPG values for patients with the 17-, 19-, 21-, and 23-mm valves were (range, 17.0 to 41.0), (range, 8.3 to 48.1), (range, 9.3 to 20.2), and (range, 4.3 to 18.9) mm Hg, respectively. The MPG values for cases with the 17-, 19-, 21- and 23-mm valves were (range, 9 to 19.0), (range, 3.5 to 19.9), (range, 9 to 12.7), and (range, 2.8 to 9.3) mm Hg, respectively. The EOA values for the 17-, 19-, 21-, and 23-mm valves were (range, 0.76 to 1.71), (range, 0.81 to 2.4), (range, 0.9 to 2.35), and (range, 1.42 to 3.00) cm 2, respectively. The EOAI values for patients with the 17-, 19-, 21-, and 23-mm valves were (0.53 to 1.23), (0.50 to 1.59), (0.61 to 1.82), and (0.86 to 2.08) cm 2 /m 2, respectively. Patient-prosthesis mismatch was found in 1 patient (25.0%) with the 17-mm valve (severe), in 3 (18.8%) with the 19-mm valve (2 mild, 1 severe), 2 (10.0%) with the 21-mm valve (both severe) and in no patients with the 23-mm valve, for with a total incidence of 10.3%. Comparison of Groups With and Without PPM An EOAI of 0.85 cm 2 /m 2 or less was defined as PPM, and the patients with and without PPM were compared (Table 4). No differences were found with respect to preoperative factors such as age, gender, BSA, and EF. In the PPM group, however, the size of the replacement

4 ADULT CARDIAC 90 SEZAI ET AL Ann Thorac Surg ECHOCARDIOGRAPHIC DATA OF THE SJM REGENT 2010;89:87 92 Table 4. Clinical Profile and Echocardiographic Data Patients With and Without Prosthesis Mismatch Variable a PPM ( ) PPM ( ) p Value Patients, No Age, years Female gender 3 (50.0) 25 (48.1) 0.99 Body surface area, m Ejection fraction Pre-op Post-op Valve size Peak pressure gradient, mm Hg Mean pressure gradient, mm Hg Effective orifice area, cm 2 EOAI, cm 2 /m a Continuous data are shown as mean standard deviation, categoric data as No. (%). EOAI effective orifice area index; PPM patient-prosthesis mismatch. valve was significantly smaller (p ) and significantly higher values were noted for PPG (p ) and MPG (p ). The EOA was significantly smaller in the PPM group (p ), as was the EOAI (p ). The postoperative EF showed no significant difference between the two groups. Dobutamine Stress Echocardiography Results of DSE are summarized in Table 5. Systolic blood pressure, heart rate, PPG, and MPG significantly increased in all 20 patients with DSE at rest and at doses of 10, 20, 30, and 40 g/kg/min. EF significantly increased at rest and at doses of 30 and 40 g/kg/min, whereas EOA and EOAI significantly increased at rest and at a dose of 40 g/kg/min. Four patients who showed an EF higher than 100 mm Hg by dobutamine stress. DSE was performed on 2 patients with PPM, showing that EF did not exceed 100 mm Hg by dobutamine stress in both cases. Comment In recent years, the HP series of the SJM valve [15], the AP series of the ATS valve [16] (ATS Medical Inc, Minneapolis, MN), and the TopHat series of the CarboMedics valve (Carbomedics, Austin, TX) [17] were developed to secure a wide valve area for replacement of a small aortic annulus without annular enlargement, and these valves have been used clinically. Patients still have PPM, however, so the development of mechanical valves with a wider effective orifice area is awaited. The SJM Regent valve used in this study showed no design changes in terms of the contact area with the blood, but it is an improved mechanical valve with a wider orifice area than the standard series or HP series of SJM valves. Walker and colleagues [18] compared the valve sizes of 17-, 19-, and 21-mm between the SJM Regent and the SJM-HP valves by an in vitro study, and reported that the PPG of the SJM Regent valve decreased by 37%, 36%, and 39%, respectively, and the EOA increased by 22%, 22%, and 21%, respectively, compared with the SJM HP series valve [18]. Although few reports on the clinical use of the SJM Regent valve are available, its efficacy has been reported in Western countries. Albes and colleagues [19] reported that the SJM Regent valve had a lower pressure gradient than the Carbo- Medics standard and the SJM HP valve, and that the 21-mm valve had a lower pressure gradient than the CarboMedics standard [19]. In a study of 32 patients with SJM Regent valves, Gelsomino and colleagues [9] found that 15.6% had PPM on discharge, but the rate decreased to 6.3% by 1 year. Bach and colleagues [13] reported the results obtained with SJM Regent valves in 361 patients at 17 hospitals. In 197 patients who underwent echocardiography at 6 months postoperatively, MPG was 10 mm Hg or less and EOAI was 1.0 cm 2 /m 2 or higher at all valve sizes from 19 mm up. No PPM was detected. However, Guenzinger and colleagues [14] studied 40 patients with SJM Regent valves and found severe PPM in 2.6% and moderate PPM in 10.3%. In the present study, the MPG exceeded mm Hg, and was 10 mm Hg for the 17-mm valve, but was 10 mm Hg or less for all sizes from 19 mm up. The prevalence of PPM was 25% at 17 mm, 18.8% at 19 mm, and 10% at 21 mm (10.3% of all patients). Because few patients with the SJM Regent valve have been reported so far, direct comparison is impossible. However, the SJM Regent valve appears to cause less PPM than conventional mechanical valves, although PPM occurs Table 5. Results of Dobutamine Stress Echocardiography a Dosage SBP DBP HR PPG MPG EOA EOAI (mm Hg) (mm Hg) (beats/min) EF (mm Hg) (mm Hg) (cm 2 ) (cm 2 /cm 2 ) Rest b c c c c c c c c c b c c c c b c c b b a Data are presented as mean standard deviation. b p c p g/kg/min; DBP diastolic blood pressure; EF ejection fraction; EOA effective orifice area; EOAI effective orifice area index; HR heart rate; MPG mean pressure gradient; PPG peak pressure gradient; SBP systolic blood pressure.

5 Ann Thorac Surg SEZAI ET AL 2010;89:87 92 ECHOCARDIOGRAPHIC DATA OF THE SJM REGENT with the smaller valve sizes. However, there have been reports stating that no clinical problems occur in patients with PPM, and we also found no clinical problems in any of the patients, even those with PPM. Okamura and colleagues [10] examined 23 cases of replacement with the 17-mm SJM Regent valve in Japanese patients, who generally have a smaller physical constitution than that of whites, and reported that the PPG was mm Hg, the EOA was cm 2 /m 2, and that PPM was found in 8 patients (34.8%). Takaseya and colleagues [11] reported replacement with the 17-mm SJM-Regent valve in 11 elderly patients, in whom the PPG was mm Hg, MPG was mm Hg, EOAI was cm 2 /m 2, and that incidence of PPM was 18.2%. Both articles concluded that the SJM Regent valve was effective for patients with a small aortic root and that there were no clinical issues, despite the occurrence of PPM. Although reports have indicated that PPM is strongly related to midterm and long-term mortality rates or cardiac events [20, 21], they have also indicated PPM is not significant for elderly patients or patients with a small physical constitution, although it may become a negative factor in young patients or patients with a larger physical constitution [22], and there have been no issues even in cases of PPM using modern mechanical valves [23]. Therefore, there is no clear consensus with respect to PPM. The incidence of PPM with the SJM Regent valve is lower than for conventional valves, and it gives better short-term outcomes, being considered as the most effective mechanical valve currently available for cardiac operations in patients with a narrow valve ring, although assessment through long-term follow-up is necessary in the future. Dobutamine stress echocardiography of the SJM Regent valve has only been reported previously by Minardi and colleagues [12], who examined 19 cases of replacement with the 17-mm SJM Regent valve and reported significant increases during DSE for heart rate ( to beat/min), EF ( to ), PPG ( to mm Hg), and MPG ( to mm Hg) compared with values at rest, whereas EOA and EOAI were unchanged. In the present study, systolic blood pressure, heart rate, PPG, and MPG were significantly increased during DSE at all time points at rest and at doses of 10, 20, 30, and 40 g/kg/min. Ejection fraction was significantly increased at rest and at doses of 30 and 40 g/kg/min, whereas EOA and EOAI were significantly increased at rest and at the dose of 40 g/kg/min. Four patients showed blood pressure higher than 100 mm Hg by dobutamine stress. Dobutamine stress echocardiography was performed on 2 patients with PPM, whose blood pressure did not exceed 100 mm Hg. However, DSE was performed only on 20 patients in the present study, from whom consent was first obtained, and no comparisons by size of mechanical valve and the presence or absence of PPM were made; therefore, further examination with an increased number of cases is necessary. In addition, we also consider it necessary to examine patients showing PPM data at rest. The debut of the SJM Regent valve in the Japanese medical field is very interesting, because there are more patients with a small aortic annulus in the Japanese population compared with the white population. In the present study, echocardiographic functional assessment on the SJM Regent valve proved that its functions as a prosthetic valve are excellent; thus, the acceptance of the prosthetic valve is expected in the future. Hereafter, we will accumulate the number of cases using this mechanical valve to continue further examination. In particular, we consider it necessary to make observations focusing on the point at which changes are found through long-term follow-up for cases of PPM. This study evaluated the function of the SJM Regent valve by Doppler echocardiography and DSE to clarify potential future problems with the valve. When performing the evaluation of artificial valves, however, it is important to examine valve-related complications during long-term follow-up. One limitation of our study is that such an examination could not be performed because of the small number of patients and short follow-up period. Therefore, more patients must be recruited and longer-term results need to be obtained in the future. By performing a randomized controlled trial for comparison with other mechanical valves and biologic prostheses, it will be possible to further clarify the efficacy and potential problems of the SJM Regent valve. Such a randomized controlled trial should be planned in the future. References 1. Sezai Y. Experience with the St. Jude Medical prosthesis. In: DeBakey ME (ed). Advances in cardiac valves: clinical perspectives. DeBakey ME (ed). New York: Yorke Medical Books; 1983: Emery RW, Krough CC, Arom KV, Emery AM, et al. The St. Jude Medical cardiac valve prosthesis: a 25-year experience with single valve replacement. Ann Thorac Surg 2005;79: Yoshikawa K, Fukunaga S, Arinaga K, et al. Long-term results of aortic valve replacement with a small St. Jude Medical valve in Japanese patients. Ann Thorac Surg 2008;85: Sezai A, Shiono M, Akiyama K, et al. Evaluation of St. Jude Medical valve s long-term function by Doppler echocardiography. Ann Thorac Cardiovasc Surg 2001;7: Sezai A, Shiono M, Hata M, Iida M, Negishi N, Sezai Y. 40 years experience in mitral valve replacement using Starr- Edwards, St. Jude Medical and ATS valves. Ann Thorac Cardiovasc Surg 2006;12: Sezai A, Shiono M, Akiyama K, et al. A case of aortic valve replacement with St. Jude Medical Regent valve (first implant in Japan). Ann Thorac Cardiovasc Surg 2005;11: Blais C, Dumesnil JG, Baillot R, Simard S, Doyle D, Pibator P. Impact of valve prosthesis-patient mismatch on short-term mortality after aortic valve replacement. Circulation 2003;108: Pibarot P, Dumesnil JG. Prosthesis-patient mismatch: definition, clinical impact, and prevention. Heart 2006;92: Gelsomino S, Morocutti G, Da Col P, et al. Early in vivo hemodynamic results after aortic valve replacement with the St. Jude Medical Regent mechanical heart valve in patients with pure aortic stenosis. J Card Surg 2003;18: Okamura H, Yamaguchi A, Tanaka M, et al. The 17-mm St. Jude Medical Regent valve is a valid option for patients with a small aortic annulus. Ann Thorac Surg 2009;87: Takaseya T, Kawara T, Tokunaga S, et al. Aortic valve replacement with 17-mm St. Jude Medical prostheses for a small aortic root in elderly patients. Ann Thorac Surg 2007;83: Minardi G, Manzara C, Creazzo V, et al. Evaluation of 17-mm St. Jude Medical Regent prosthetic aortic heart valves by rest and dobutamine stress echocardiography. J Cardiothorac Surg 2006;1: ADULT CARDIAC

6 ADULT CARDIAC 92 SEZAI ET AL Ann Thorac Surg ECHOCARDIOGRAPHIC DATA OF THE SJM REGENT 2010;89: Bach DS, Sakwa MP, Goldbach M, Petracek MR, Emery RW, Mohr FW. Hemodynamics and early clinical performance of the St. Jude Medical Regent mechanical aortic valve. Ann Thorac Surg 2002;74: Guenzinger R, Eichinger WB, Hettich I, et al. A prospective randomized comparison of the Medtronic Advantage Supra and St. Jude Medical Regent mechanical heart valves in the aortic position: is there an additional benefit of supra-annular valve positioning? J Thorac Cardiovasc Surg 2008;136: Vitale N, Caldarera I, Muneretto C, et al. Clinical evaluation of St. Jude Medical Hemodynamic Plus versus standard aortic valve prostheses: the Italian multicenter prospective, randomized study. J Thorac Cardiovasc Surg 2001;122: Labrousse LM, Choukroun E, Serena D. Prospective study of hemodynamic performances of standard ATS and AP-ATS valves. J Heart Valve Dis 2003;12: Gillinov AM, Blackstone EH, Alster JM, et al. The CarboMedics Top Hat supraannular aortic valve: a multicenter study. Ann Thorac Surg 2003;75: Walker DK, Brendzel AM, Scotten LN. The new St. Jude Medical Regent mechanical heart valve: laboratory measurements of hydrodynamic performance. J Heart Valve Dis 1999;8: Albes JM, Hartrumpf M, Rudolph V, et al. Are mechanical valves with enhanced inner diameter advantageous in the small sized aortic annulus? Ann Thorac Surg 2003;76: Mohty-Echahidi D, Malouf JF, Girard SG, et al. Impact of prosthesis-patient mismatch on long-term survival in patients with small St. Jude Medical mechanical prostheses in the aortic position. Circulation 2006;113: Tasca G, Mhagna Z, Perotti S, et al. Impact of prosthesispatient mismatch on cardiac events and midterm mortality after aortic valve replacement in patients with pure aortic stenosis. Circulation 2006;113: Moon MR, Pasque MK, Munfakh NA, et al. Prosthesis-patient mismatch after aortic valve replacement: impact of age and body size on late survival. Ann Thorac Surg 2006;81: Izzat MB, Kadir I, Reeves B, Wilde P, Bryan AJ, Angelini GD. Patient-prosthesis mismatch is negligible with modern small-size aortic valve prostheses. Ann Thorac Surg 1999;68: INVITED COMMENTARY The St. Jude Medical Regent valve (St. Jude Medical, St. Paul, MN) was designed to maximize the effective flow orifice area for any given tissue annulus diameter. It was the first mechanical valve prosthesis to demonstrate left ventricular mass regression similar to stentless biologic valves, yet with unquestioned durability. Sezai and colleagues [1] are well known for their work with prosthetic heart valves and have documented the hemodynamics of smaller sized St. Jude Medical Regent valves implanted in the Japanese population. They found low peak to peak and low mean gradients across the prostheses, and a minimal incidence of patient prosthesis mismatch (PPM). Although the numbers are small, if PPM was present, there was no impact on the postoperative morbidity or mortality or on the follow-up survival. These data are similar to our report that was made to The Society of Thoracic Surgeons in 2005 (unpublished data), in which we presented a review of PPM after aortic valve replacement, using the St. Jude Medical valve and follow-up for as long as 25 years. The PPM occurred the least with the St. Jude Medical Regent valve compared with the HP and standard model valves. In addition, PPM (whether moderate or severe, geometric, or echocardiographically determined) did not impact mortality or survival for the operative course or for the long-term follow-up. However, age, ventricular function, and patient activity level were unable to be evaluated. Importantly, this may be an advantage for using a mechanical valve prosthesis. In the early postoperative period, even though a mismatch may occur, the transvalvar gradients are substantially reduced from that of the aortic stenosis of the preoperative period. This allows for ventricular recovery and ventricular mass regression. Gradients across the mechanical prosthesis do not change with time, as Dr Emery discloses a financial relationship with St. Jude Medical Inc. opposed to biological valves, which most commonly become more rigid as structural valve degeneration occurs, recreating an environment of aortic stenosis within the biologic valve. As with Sezai and colleagues [1], our group has not found aortic annular enlargement procedures necessary since the approval of the St. Jude Medical Regent valve. However, it is interesting that the highest incidence of severe PPM in this report consisted of only two cases having occurred with the size 21 St. Jude Medical Regent valve, which had a reported mean valve area of cm 2. This is approximately equivalent to the flow orifice area of a St. Jude Medical standard size 24 prosthesis; therefore, it must have been implanted in substantially larger individuals. In summary, we concur with the conclusion of the article that finds the following: Echocardiographic functional assessment was done on the SJM Regent valve and proved that its functions as a prosthetic valve are excellent. Robert W. Emery, MD Cardiovascular Surgery St. Joseph s Hospital 69 W Exchange St St. Paul, MN rwemery@healtheast.org Goya V. Raikar, MD Regions Hospital 655 Jackson St St. Paul, MN Reference 1. Sezai A, Kasamaki Y, Abe K, et al. Assessment of the St. Jude Medical Regent prosthetic valve by continuous-wave Doppler and dobutamine stress echocardiography. Ann Thorac Surg 2010;89: by The Society of Thoracic Surgeons /10/$36.00 Published by Elsevier Inc doi: /j.athoracsur