Aortic Valve Replacement With 17-mm Mechanical Prostheses: Is Patient Prosthesis Mismatch a Relevant Phenomenon?

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1 Aortic Valve Replacement With 17-mm Mechanical Prostheses: Is Patient Prosthesis Mismatch a Relevant Phenomenon? Andrea Garatti, MD, Francesca Mori, MD, Francesco Innocente, MD, Alberto Canziani, MD, Piervincenzo Gagliardotto, MD, Eugenio Mossuto, MD, Tiberio Santoro, MD, Vincenzo Montericcio, MD, Alessandro Frigiola, MD, and Lorenzo Menicanti, MD I Division of Cardiac Surgery, II Division of Cardiac Surgery, and Echocardiography, IRCCS Policlinico San Donato Hospital, San Donato Milanese, Milan; and Division of Cardiology, Casa Sollievo della Sofferenza, San Giovanni Rotondo, Foggia, Italy Background. We sought to evaluate the long-term performance of a consecutive cohort of patients implanted with a 17-mm bileaflet mechanical prosthesis. Methods. Between January 1995 and December 2005, 78 patients (74 women, mean age years) underwent aortic valve replacement with a 17-mm mechanical bileaflet prosthesis (Sorin Bicarbon-Slim and St. Jude Medical-HP). Preoperative mean body surface area and New York Heart Association class were m 2 and , respectively. Preoperative mean aortic annulus, indexed aortic valve area, and peak and mean gradients were mm, 0.42 cm 2 /m 2,89 32 mm Hg, and mm Hg, respectively. Patients were divided into two groups, according to the presence (group A, 29 patients) or absence of patient prosthesis mismatch (group B, 49 patients). Patient prosthesis mismatch was defined by an indexed effective orifice area less than 0.85 cm 2 /m 2. Results. Overall hospital mortality was 8.8%. Follow-up time averaged months. Actuarial 5-year and 10-year survival rates were 83.7% and 65.3%, respectively. The mean postoperative New York Heart Association class was (p < 0.001). Overall indexed left ventricular mass decreased from to g/m 2 (p < 0.001), whereas average peak and mean prosthesis gradients were 28 9mmHgand15 6mmHg, respectively (p < 0.001). Early and long-term mortality were similar between the two groups as well as longterm hemodynamic performance (mean peak gradient was 28 mm Hg and 27 mm Hg in group A and B, respectively, not significant); left ventricular mass regression occurred similarly in both groups (indexed left ventricular mass at follow-up was and in group A and B, respectively; not significant). Conclusions. Selected patients with aortic stenosis experience satisfactory clinical improvement after aortic valve replacement with modern small-diameter bileaflet prostheses. (Ann Thorac Surg 2011;91:71 8) 2011 by The Society of Thoracic Surgeons Aortic valve replacement (AVR) in elderly patients with a small aortic root is still a challenging scenario for the cardiac surgeon. It is generally accepted that biologic prostheses are the valve of choice in the elderly, but no stented prostheses less than 19 mm are actually available. Furthermore, small stented biologic valves, especially if implanted in patients with high body surface area, show high transprosthesis postoperative gradients, the so-called patient prosthesis mismatch (PPM) phenomenon [1]. Patient prosthesis mismatch was demonstrated to increase left ventricular (LV) work, to reduce LV mass regression, and to produce symptoms of aortic stenosis [2]. Some studies [3, 4] showed that PPM correlates with an increase in early Accepted for publication Aug 19, Address correspondence to Dr Garatti, Department of Cardiovascular Disease E. Malan, Cardiac Surgery Unit, Policlinico S. Donato Hospital, Via Morandi 30, S. Donato Milanese, Milan, Italy; agaratti@ tiscali.it. mortality and poor long-term outcomes, but this issue has yet to be fully solved. Actually, several surgical strategies can be applied to avoid PPM; these include the use of aortic root enlargement (ARE) procedures, and the implantation of stentless bioprostheses or of modern small bileaflet mechanical valves with an improved hemodynamic profile. Although root enlargement procedures, as well as stentless valve implantation, performed in experienced centers, showed good early and long-term results [5, 6], these are complex and time-consuming procedures that can be difficult to perform in elderly patients with a small, calcified aortic annulus and root. On the contrary, good results have been reported when bileaflet prostheses with improved hemodynamics were implanted in small aortic roots averaging 19 to 20 mm [7]. However, only a few studies report experiences with 17-mm mechanical valves. Thus, the aim of this study is to review our experience with a consecutive series of patients 2011 by The Society of Thoracic Surgeons /$36.00 Published by Elsevier Inc doi: /j.athoracsur

2 72 GARATTI ET AL Ann Thorac Surg AVR WITH 17-MM PROSTHESES 2011;91:71 8 Table 1. Preoperative Characteristics Age (y), mean SD (73 [32 90]) Female sex 74 (95%) Height (cm), mean SD (158 [ ]) Weight (kg), mean SD (60 [40 98]) BSA (m 2 ), mean SD (1.55 [ ]) NYHA class I 13 (16%) II 21 (27%) III 39 (50%) IV 5 (7%) Aortic valve disease Degenerative 55 (70%) Rheumatic 17 (22%) Congenital 6 (8%) Hypertension 45 (58%) Diabetes 5 (7%) Dyslipidemia 11 (14%) Standard EuroScore, mean SD (6.0 [ ]) Logistic EuroScore, mean SD (5.9 [ ]) BSA body surface area; NYHA New York Heart Association; SD standard deviation. implanted with 17-mm mechanical valves for isolated aortic stenosis. Material and Methods Patient Characteristics Between January 1995 and December 2005, 2,570 isolated AVR procedures with mechanical prostheses were performed in our hospital. A 17-mm mechanical valve was implanted in 95 (3.7%) patients. Of those 95 patients, 17 patients with associated procedures (other than coronary artery bypass grafting) were excluded; thus, only 78 patients entered the study. Among them, 74 (95%) were female, with a mean age of years and a mean body surface area of m 2. Preoperative clinical features are shown in Table 1. Symptoms at admission included dyspnea in 43 patients (55%), angina in 20 patients (26%), and syncope or arrhythmia in 7 patients (9%). In 8 asymptomatic patients a surgical procedure was indicated for severe reduction of aortic valve area at echocardiography and high transvalvular gradients. Mean preoperative New York Heart Association (NYHA) class was In 27 patients (34%) associated coronary atherosclerosis was detected at preoperative coronary angiography. Coronary artery disease was defined as a severe narrowing ( 60%) of one or more coronary arteries. Every patient with coronary artery disease according to these criteria underwent coronary artery bypass grafting. The most common cause of the aortic stenosis was degenerative (70%). The Istituto Policlinico San Donato ethical committee waived the need for informed consent in consideration of the retrospective nature of the study. All patients admitted to the study gave informed consent to the scientific analysis of their clinical data in an anonymous form. Echocardiography A complete M-mode, two-dimensional, and Doppler evaluation was performed using commercially available ultrasonographic equipment (Vivid 5 or Vivid 7, GE Healthcare, Horten, Norway). All Doppler measurements were obtained as the average of at least three cycles in patients with sinus rhythm or more than five cycles in those with atrial fibrillation. Preoperative LV enddiastolic and end-systolic diameters and volumes, as well as LV ejection fraction, were calculated using the arealength method. Left ventricular mass index was calculated from Reichek s formula [8]. Diastolic interventricular septum and LV posterior wall thicknesses were measured in long-axis view. As regard to aortic valve evaluation, we measured aortic box (defined as the distance between noncoronary cusp and right cusp of the aortic valve measured in long-axis view), indexed aortic valve area, and aortic annulus diameter. The peak and mean gradients across the aortic valve as well as across the prostheses were calculated according to the modified Bernoulli equation. Echocardiographic evaluation with the same variables was repeated before discharge and at follow-up. Surgical Technique All the procedures were performed through a midline sternotomy, on cardiopulmonary bypass and mild hypothermia. Myocardial protection was achieved with antegrade cold crystalloid cardioplegia and topical heart cold irrigation. Valve prostheses were implanted with interrupted single pledgeted sutures. Fifty patients (63%) were implanted with a 17-mm Sorin Bicarbon Slim prosthesis (Sorin Biomedica, Saluggia, Italy), and 28 patients (37%) were implanted with a 17-mm St. Jude Medical Hemodynamic Plus (St. Jude Medical, St. Paul, MN). Coronary artery bypass grafting was performed in 26 patients (33%). Mean number of coronary artery bypass grafts per patient was (range, 1 to 5 grafts). Mean bypass time was minutes (range, 41 to 150 minutes) and cross-clamp time was minutes (range, 35 to 103 minutes). Postoperative inotropic support (defined as the isolated infusion of dopamine greater than 5 g kg 1 min 1 or in association with another inotropic agent) was required in 19 patients (24%). Mean intensive care unit stay was days (range, 1 to 13 days). After the second postoperative day, patients received oral anticoagulation with sodium warfarin at daily updated dosages according to international normalized ratios. The target international normalized ratio value was in accordance with American College of Cardiology/ American Heart Association guidelines.

3 Ann Thorac Surg GARATTI ET AL 2011;91:71 8 AVR WITH 17-MM PROSTHESES Follow-Up Data All patients were followed in the outpatient center with clinical visits and echocardiography performed on an annual basis. A telephone interview was required only for patients with follow-up visits in excess of 6 months or for those lost to ambulatory follow-up. The follow-up was 100% complete, and the mean time to last follow-up was months (median, 76 months; range, 18 to 178 months). Valve-related complications were reported according to the American Association for Thoracic Surgery Guidelines for reporting morbidity and mortality after cardiac valvular operations [9]. 73 Statistical Analysis Results are presented as mean standard deviation. Paired two-sided Student s t test was used for comparison of continuous variables. A Wilcoxon two-sample test was used for comparison of continuous variables when the examined samples were small in number with unknown distribution. Fisher s exact test (two-tailed) was used for categorical variables. A probability value less than 0.05 was considered statistically significant. Potential univariate predictors of outcome (in-hospital mortality and long-term mortality) were individually tested for equality with a one-way analysis of variance test. Linear regression multivariate analysis was performed incorporating all variables that had a probability value of 0.05 or less at analysis of variance testing. Stepwise forward selection and backward elimination techniques were used with a probability value of 0.05 for entry and a probability value of 0.10 for removal criteria. Results Clinical Results and Follow-Up The overall 30-day mortality was 8.8% (7 patients; mean age, 78 6 years). No further 60- or 90-day mortality occurred. All of these early deaths were non valverelated deaths: low cardiac output syndrome (5 patients, 72%), acute renal failure (1 patient, 14%), and cerebrovascular event (1 patient, 14%). The 7 patients who died in the hospital were significantly at risk compared with survivors; they were older (78 6 years compared with years; p 0.005), with advanced NYHA class ( compared with ; p 0.005), and with higher incidence of coronary artery disease (57% compared with 32%; p 0.001). This worse clinical status was expressed also by the mean standard and logistic EuroScores (early deaths: Standard EuroScore 8 2; Logistic EuroScore 11 6; survivors: Standard EuroScore 6 2; Logistic EuroScore 7 4; p 0.005). Early complications were observed in 12 patients (15%). Three patients experienced low output cardiac syndrome requiring high-dose inotropic support, whereas 2 patients returned to the operating room for excessive postoperative bleeding. Two patients experienced transient postoperative acute renal failure, whereas in 5 patients we observed total atrioventricular block requiring pacemaker implant. Fig 1. Long-term postoperative survival. The Kaplan-Meier survival estimates were 83.7% at 5 years and 65.3% at 10 years. (Pts patients.) Univariate and multivariate analyses identified preoperative NYHA class as the only significant predictor of in-hospital mortality (p 0.009). Of the 71 survivors, 14 patients (20%) died after discharge. Among them, 4 patients died of chronic heart failure, 2 patients died as a consequence of cerebral hemorrhage, and 2 patients died of chronic renal failure; the remaining 6 patients died of noncardiac causes. Actuarial 5-year and 10-year survival rates were 83.7% and 65.3%, respectively (Fig 1). Two patients experienced late cerebral hemorrhage. There was no structural failure of the prostheses, no paravalvular leak, and no prosthetic endocarditis. Freedom from reoperation was 100%. The postoperative average NYHA class was with 48 patients in class I (Fig 2). Univariate analysis identified preoperative coronary artery disease, mean preoperative transvalvular gradient, and mean preoperative LV mass as predictors of longterm mortality. At multivariate analysis preoperative coronary artery disease was the only independent predictor of long-term mortality (p 0.005). Fig 2. Functional New York Heart Association class assessment before surgery and at follow-up.

4 74 GARATTI ET AL Ann Thorac Surg AVR WITH 17-MM PROSTHESES 2011;91:71 8 Table 2. Comparison of Echocardiographic Characteristics Before Surgery, at Discharge, and at Follow-Up a Variable Preoperative At Discharge Follow-up p Value b Peak gradient (mm Hg) (89[70 164]) (30[12 60]) 28 9 (25[14 52]) Mean gradient (mm Hg) (55[45 106]) 18 7 (17[7 40]) 15 6 (14[7 32]) Indexed LV mass (g/m 2 ) (161[ ]) (138[70 245]) (107[70 206]) IV septum (mm) 14 3 (14[7 23]) 13 3 (13[8 21]) 11 3 (12[9 18]) Posterior wall (mm) 13 2 (13[8 19]) 13 2 (13[9 18]) 11 2 (11[8 17]) EF (0.59[ ]) (0.56[ ]) (0.57[ ]) a Values are reported as mean SD. b Paired Student s t test is applied between preoperative and follow-up values. EF ejection fraction; IV interventricular; LV left ventricular; SD standard deviation. Echocardiographic Follow-Up Echocardiographic results are summarized in Table 2. A significant reduction in peak and mean gradients was observed in all patients, with a mean difference versus preoperative values of mm Hg and mm Hg (p 0.001), respectively. Furthermore, we failed to find significantly different reduction in postoperative gradients between survivors and nonsurvivors (average peak and mean gradients were mm Hg and 16 7mmHgin survivors compared with mm Hg and 17 7mm Hg in nonsurvivors, respectively; not significant). A statistically significant reduction in mean LV mass was found with a mean difference of g/m 2 (p 0.001). No significant difference was observed between preoperative and postoperative mean ejection fraction (Fig 3). Patient Prosthesis Mismatch Comparison The prevalence of PPM, defined as an indexed effective orifice area (EOA) of less than 0.85 cm 2 /m 2, was documented in 29 patients (37%). Clinical and echocardiographic data of patients with PPM compared with those without PPM are depicted in Table 3. When compared with the group of patients without PPM, the group with PPM had a significantly larger body surface area and proportion of males. However, the presence of PPM did not affect early and long-term survival or postoperative functional status. A significant reduction of peak and mean gradients, as well as LV hypertrophy, occurred in both groups, with PPM patients showing a significantly higher transprosthesis gradient at discharge compared with non-ppm patients. However, at follow-up no significant difference between the two groups occurred in terms of transvalvular gradient or in LV mass reduction (mean indexed LV mass difference versus preoperative value was versus 43 7 in PPM and no-ppm groups, respectively; not significant). Comment Surgical management of the small aortic root at the time of AVR has been discussed in the cardiac surgery literature for more than 30 years. In particular, the optimal prosthesis for AVR in patients with aortic roots smaller than 19 mm remains an unresolved problem in the elderly. In such cases the three available options are selection of a 19-mm stented bioprosthesis with ARE, root replacement with a 19-mm stentless valve, or implantation of a 17-mm bileaflet mechanical valve. Despite the fact that several studies report good clinical and echocardiographic outcomes of patients who underwent AVR with small (21-mm or 19-mm) mechanical bileaflet valves [10, 11], reported experiences with 17-mm mechanical valve are extremely scarce [12 14]. Thus the purpose of the present study was to evaluate the early and long-term results of AVR with modern 17-mm mechanical bileaflet prosthesis in a population of elderly patients affected by severe aortic stenosis. Fig 3. Evolution of echocardiographic characteristics before surgery through discharge and followup. Probability value is calculated according to paired Student s t test between preoperative and follow-up results. (EF ejection fraction; LV left ventricle.)

5 Ann Thorac Surg GARATTI ET AL 2011;91:71 8 AVR WITH 17-MM PROSTHESES Table 3. Clinical and Echocardiographic Characteristics Comparison Between Patients With and Without Patient Prosthesis Mismatch a Variable PPM No PPM p Value 75 Number 29 (37%) 49 (63%) Age (y) (72) (73) Female sex 25 (86%) 49 (100%) BSA (m 2 ) Indexed EOA (cm 2 /m 2 ) Preoperative NYHA class Coronary artery disease 8 (27%) 19 (38%) In-hospital mortality 1 (4%) 6 (12%) Follow-up mortality 5 (23%) 9 (27%) Follow-up NYHA class Preoperative echocardiography Peak gradient (mm Hg) (100) (85) Mean gradient (mm Hg) (62) (52) Indexed LV mass (g/m 2 ) (167) (154) EF (0.58) (0.59) Postoperative echocardiography Peak gradient (mm Hg) (37) 27 7 (27) Mean gradient (mm Hg) 23 8 (20) 15 4 (15) Indexed LV mass (g/m 2 ) (143) (136) EF (0.55) (0.56) Echocardiography at follow-up Peak gradient (mm Hg) Mean gradient (mm Hg) Indexed LV mass (g/m 2 ) EF a Values are reported as mean SD (median) or as number (percentage). BSA body surface area; EF ejection fraction; EOA effective orifice area; LV left ventricular; NYHA New York Heart Association; PPM patient prosthesis mismatch; SD standard deviation. In this cohort of patients we observed that (1) in small and calcified aortic annulus, mechanical valve implantation was safe, simple, and rapid, yielding satisfying in-hospital outcomes in a relatively high-risk population (mean logistic EuroScore was 7.3); (2) clinical outcomes of AVR with mechanical valves in an elderly population showed good results, with functional status improvement and very low incidence of valve-related and anticoagulation-related complications; (3) 17-mm mechanical prostheses showed a significant reduction of transprosthesis gradients and LV mass both postoperatively and at follow-up; and (4) PPM incidence in our cohort was 37% of patients, but it showed no impact on early and long-term outcomes or on hemodynamic performances and LV hypertrophy regression. We chose to implant 17-mm mechanical valves in this population for several reasons. First, our cohort of patients showed a moderately high-risk profile (high proportion of female patients [95%], advanced NYHA class [57%], and associated coronary artery disease [34%]), so that a quick and simple procedure was desirable. In fact it has been well documented that aortic cross-clamp time is one of the most important predictors of in-hospital mortality for elderly patients undergoing cardiac surgery [15]. Although several good results have been reported for ARE procedures [5] or for stentless valve implantation [16], these procedures are technically more difficult, require longer cross-clamp times, and may have greater morbidity than simple valve replacement, especially in elderly patients who often have a calcified aortic root. Furthermore, Kulik and coworkers [17] recently demonstrated that patients with small aortic roots treated with ARE and AVR have better hemodynamic outcomes after surgery, without experiencing an increased risk of perioperative morbidity or mortality, but the ARE procedure did not appreciably improve long-term clinical outcomes after AVR. The surgeon s dilemma emerges especially in planning treatment for elderly patients who are scheduled for concomitant procedures that carry the prospect of long crossclamp times. In this situation implanting a modern bileaflet mechanical valve seems a reasonable and attractive procedure. However, another emerging technology seems extremely promising in an elderly, high-risk population. Sutureless aortic valve are stentless bioprostheses mounted on a self-expanding nitinol frame, which allows the fixation of the device in the directly decalcified aortic annulus without surgical sutures by virtue of outward radial forces inherent in the nitinol stent. This approach allows significant shortening of the aortic cross-clamp time, especially if concomitant procedures are scheduled. Actually very few experience of sutureless aortic valve are reported. Martens

6 76 GARATTI ET AL Ann Thorac Surg AVR WITH 17-MM PROSTHESES 2011;91:71 8 and coworkers [18] reported on 32 patients implanted with the nitinol-stented 3f Enable valve (ATS Medical, Minneapolis, MN), and Shrestha and coworkers [19] reported on 30 patients implanted with the Percefal S sutureless valve (Sorin Biomedica, Saluggia, Italy). These initial experiences are encouraging; however no sutureless valves smaller than 21 mm are commercially available at the moment, thus limiting this encouraging approach in patients with very small aortic root (like our study population). Furthermore, the follow-up was limited to 1 year, and the reported postoperative peak and mean transvalvular gradients were 18 9mmHgand10 4 mm Hg, respectively, which are not so different from our reported postoperative gradients with a significantly smaller prosthesis. Some could argue that mechanical valves in the elderly may increase mortality and morbidity if compared with bioprostheses, especially as a result of anticoagulationrelated complication [20]. However, in our aged population, implantation of mechanical valves resulted in excellent outcomes, with very low incidence of valve-related and anticoagulation-related complications. Ninet and associates [21] and Sawaki and colleagues [22], reporting on isolated mechanical AVR in patients older than 70 years, have shown low rates of anticoagulation-related complications, suggesting that mechanical valves are not a risk for late mortality or morbidity with good prothrombin time international normalized ratio control (1.8 to 2.2). Furthermore, quantitative measurement of the quality of life at follow-up was behind the aim of this study. However, our group, in a previously reported experience of 345 octogenarians operated on for isolated AVR [23], was able to demonstrate a higher survival rate, a reduced cardiacrelated death, and a better quality-of-life SF-36 test score in patients implanted with mechanical valves compared with bioprostheses. The hemodynamic behavior of 17-mm mechanical prostheses in the present experience was excellent, with significant reduction of transprosthesis gradients and LV mass both postoperatively and at follow-up. Functional improvement was also excellent, with the vast majority of patients in NYHA class I or II postoperatively. These results are consistent with the published experience by Takaseya and coworkers [24]; these authors reported excellent long-term hemodynamic performance in 34 Japanese patients who underwent AVR with a 17-mm St. Jude Regent valve. These satisfying results are probably related to the excellent EOA of modern bileaflet 17-mm mechanical prostheses. The EOA of the 17-mm Sorin Bicarbon Slim valve (which constitutes the vast majority of the present study s implanted valves) is 1.58 cm 2, which favorably compares with the EOA of the 19-mm and 21-mm Carpentier-Edwards pericardial stented bioprosthesis (1.3 and 1.5 cm 2, respectively) and the EOA of the Edwards Prima Plus stentless porcine bioprosthesis (1.66 cm 2 ; Edwards Lifesciences, Irvine, CA). It is notable that such hemodynamic and clinical improvement was achieved despite the presence in the study group of a proportion of PPM of nearly 40%. The concept of PPM was first introduced by Rahimtoola [1] in 1978 to describe the condition in which the prosthetic valve orifice area is less than that of the native human valve. Subsequent studies examining the physiologic sequelae of PPM have fostered the recommendation that the indexed EOA of an aortic prosthesis should ideally be greater than 0.85 cm 2 /m 2 to minimize postoperative gradients and improve clinical results [25]. There continues to be controversy in the literature as to the relevance of PPM. A large number of studies have examined the effect of PPM on survival after AVR [26,27]. Initial reports suggested a stepwise increase in in-hospital and late mortality rates associated with mismatch. These studies also noted a similar association with increasing age and female sex and acknowledged that the decrease in late survival may have been related to this increased risk profile. Further analyses taking into account the different risk profiles found no adverse effect on survival associated with both moderate PPM and severe PPM for the cohort as a whole [28], but subgroup analyses from these more recent studies have suggested that younger patients or patients with impaired ventricular function may still be at risk of reduced survival with severe PPM [29]. With regard to PPM, we can offer the following conclusions: in our experience, PPM was not an independent risk factor for early or late mortality; PPM did not affect clinical improvement or LV mass regression; and despite that, patients without PPM experienced a significantly better hemodynamic profile compared with PPM patients at discharge. This difference was not sustained at follow-up, so that PPM failed to be a risk factor for late hemodynamic improvement. No further subgroup analysis (ie, PPM effect on younger age) was possible owing to the limited numbers of the study population. Study Limitations The first limitation of the study is its retrospective design. Furthermore, the small sample size and the lack of a control group can limit the power of our observations. However, our aim was not to compare different valve types or surgical strategies to address the issue of a small aortic root in the elderly. We wanted to analyze the clinical and hemodynamic performance of a small bileaflet mechanical valve. Given that in our study the early and long-term outcomes are encouraging, even in the absence of a control group, we think that our results can support the idea that a 17-mm mechanical valve can be safely implanted in certain circumstances. Another limitation concerns the PPM analysis. In our study we failed to find PPM as a risk factor for early and long-term mortality. However, the vast majority of our patients exhibited moderate PPM (indexed EOA 0.85 cm 2 /m 2 ), and only 6 patients had severe PPM (indexed EOA 0.65 cm 2 /m 2 ); this fact may have influenced our results. However, even if these numbers are too small for a meaningless analysis, we failed to find any significant difference in terms of long-term mortality between patients with severe PPM compared with patients with moderate PPM (severe PPM group [6 patients]: 1 death [16%], with mean follow-up length, months; moderate PPM group [23 patients]: 5 deaths [21%], with mean follow-up length, months; not significant).

7 Ann Thorac Surg GARATTI ET AL 2011;91:71 8 AVR WITH 17-MM PROSTHESES Conclusions In conclusion, we believe that the 17-mm bileaflet mechanical valve can be a good choice in elderly patients with a small aortic root less than 19 mm. This can be an alternative to longer and more complex procedures, and it showed very good results in terms of late survival, clinical and hemodynamic improvement, and freedom from severe anticoagulation-related complications. Furthermore, early and long-term outcomes, as well as clinical improvement, seem to be unaffected by the presence of moderate to severe PPM. Further studies on larger populations are required to evaluate the impact of implanting small prostheses (especially if a PPM is present) in younger patients or in the presence of LV dysfunction. References 1. Rahimtoola S. The problem of valve prosthesis-patient mismatch. Circulation 1978;58: Pibarot P, Dumesnil JG, Lemieux M, Cartier P, Metras J, Durand LG. 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Eur J Cardiothorac Surg 1998;13: Sawaki S, Usui A, Abe T, Yoshikawa M, Akita T, Ueda Y. Late mortality and morbidity in elderly patients with mechanical heart valves. Asian Cardiovasc Thorac Ann 2006;14: De Vincentiis C, Kunkl AB, Trimarchi S, et al. Aortic valve replacement in octogenarians: is biologic valve the unique solution? Ann Thorac Surg 2008;85: Takaseya T, Kawara T, Tokunaga S, Kohno M, Oishi Y, Morita S. Aortic valve replacement with 17-mm St. Jude Medical prostheses for a small aortic root in elderly patients. Ann Thorac Surg 2007;83: 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: Tasca G, Mhagna Z, Perotti S. Impact of prosthesis-patient mismatch on short term on cardiac events and mid-term mortality after aortic valve replacement in patients with pure aortic stenosis. Circulation 2006;113: Walther T, Rastan A, Falk V, et al. Patient prosthesis mismatch affects short- and long-term outcome after aortic valve replacement. Circulation 2003;108: Howell NJ, Keogh BE, Barnet V, et al. Patient-prosthesis mismatch does not affect survival following aortic valve replacement. Eur J Cardiothorac Surg 2006;30: Mohty D, Dumensil JG, Echahidi N, et al. Impact of prosthesis-patient mismatch on long-term survival after aortic valve replacement: influence of age, obesity and left ventricular dysfunction. J Am Coll Cardiol 2009;53: INVITED COMMENTARY Common sense suggests that if a diseased heart valve is to be replaced, the implanted prosthesis should be large enough so that the heart can function properly. Nevertheless, the subject of patient-prosthesis mismatch (PPM), currently defined as an effective orifice area of less than 0.85 cm 2 m 2 body surface area (BSA), is still 2011 by The Society of Thoracic Surgeons /$36.00 Published by Elsevier Inc doi: /j.athoracsur