Late haemodynamic performance and survival after aortic valve replacement with the Mosaic bioprosthesis

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1 Interactive CardioVascular and Thoracic Surgery 19 (2014) doi: /icvts/ivu238 Advance Access publication 12 July 2014 ORIGINAL ARTICLE ADULTCARDIAC Late haemodynamic performance and survival after aortic valve replacement with the Mosaic bioprosthesis Natalie Glaser a,b, Anders Franco-Cereceda a,b and Ulrik Sartipy a,b, * a b Department of Cardiothoracic Surgery and Anesthesiology, Karolinska University Hospital, Stockholm, Sweden Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden * Corresponding author. Department of Cardiothoracic Surgery and Anesthesiology, Karolinska University Hospital, Stockholm, Sweden. Tel: ; fax: ; ulrik.sartipy@karolinska.se (U. Sartipy). Received 18 March 2014; received in revised form 12 June 2014; accepted 17 June 2014 Abstract OBJECTIVES: The objective was to evaluate the long-term haemodynamic performance of the Mosaic aortic bioprosthesis. Secondary objectives were to investigate the long-term survival, the rate of aortic valve reoperations, and the rate of prosthesis patient mismatch and its effect on long-term survival. METHODS: We included all patients who underwent aortic valve replacement with a Mosaic bioprosthesis at our institution between 2002 and Valve haemodynamics were assessed by transthoracic echocardiography as mean and peak pressure gradients. Patient characteristics and outcomes were collected from charts and national registers. RESULTS: We included 355 patients and echocardiographic evaluation was performed at early follow-up in 340 patients (96%) and at late follow-up in 161 patients (45%). The mean follow-up time was 7.1 (maximum 11.7) years. The unadjusted survival at 1, 5 and 10 years was 92, 79 and 42%, respectively. At the early postoperative echocardiography, the peak pressure gradient was 39.9 mmhg (SD 14.4) and the mean pressure gradient was 21.1 mmhg (SD 7.7) and, on late echocardiography, the peak pressure gradient was 38.6 mmhg (SD 15.6) and the mean pressure gradient was 22.5 mmhg (SD 10.1). Moderate or severe prosthesis patient mismatch was found in 250 (70%) and 49 patients (14%), respectively, but was not significantly associated with mortality in multivariable analyses. CONCLUSIONS: We found that the Mosaic aortic bioprosthesis had acceptable clinical performance at late follow-up. However, a substantial proportion of patients had high transvalvular gradients or moderate or severe prosthesis patient mismatch, although neither were significantly associated with long-term survival in our population. Keywords: Aortic valve Replacement Heart valve Bioprosthesis Outcomes INTRODUCTION The Medtronic Mosaic aortic bioprosthesis (Medtronic, Inc., Minneapolis, MN, USA) is one of the world s most commonly used bioprostheses for aortic valve replacement (AVR). It is a thirdgeneration, stented porcine bioprosthesis treated with a combination of alpha-amino oleic acid and glutaraldehyde fixation at zero pressure [1] to improve tissue durability and haemodynamic performance. The Mosaic bioprosthesis has been in clinical use since 1994 and follow-up studies have shown excellent results in terms of long-term survival [2 6] as well as haemodynamic performance [2, 3, 5]. However, some studies have shown results suggesting increased postoperative gradients at long-term follow-up [4, 7, 8] and a higher incidence of prosthesis patient mismatch (PPM) with the Mosaic bioprosthesis compared with other contemporary bioprostheses [8]. Additionally, early structural valve deterioration (SVD) of the Mosaic bioprosthesis has been reported in 6 patients [9, 10], suggesting a need for clinical awareness regarding this potential problem. In a previous study [11], we compared the Mosaic and the Carpentier-Edwards Perimount (Edwards Lifesciences, Irvine, CA, USA) aortic bioprostheses and, although we found no significant difference in terms of long-term survival or rate of reoperations, there was a higher incidence of PPM in the Mosaic population. Therefore, we conducted a study including all patients who underwent AVR with the Mosaic bioprosthesis at our department between 2002 and The primary objective of our study was to evaluate the long-term haemodynamic performance of the Mosaic bioprosthesis in the aortic position. The secondary objectives were to investigate the long-term survival, the rate of aortic valve reoperations, and the rate of PPM and its effect on long-term survival. PATIENTS AND METHODS The study was approved by the Regional Ethical Review Board, Stockholm, Sweden. Methods for data analysis and reporting were according to guidelines [12]. The Author Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

2 N. Glaser et al. / Interactive CardioVascular and Thoracic Surgery 757 Study design and study population We performed a population-based cohort study including all patients who received a Medtronic Mosaic porcine aortic bioprosthesis at the Karolinska University Hospital, Stockholm, Sweden, between 2002 and The Mosaic bioprosthesis was the standard aortic bioprosthesis at our institution between 2002 and 2004 and, therefore, most valves were implanted during this period. Echocardiography The early postoperative transthoracic echocardiography (TTE) was performed during initial hospital stay, most commonly on postoperative day 3. All patients alive in August 2012 were asked to participate in this study and were offered a new TTE to assess the function of the Mosaic bioprosthesis. TTE data were collected from patient charts in patients who declined a new TTE and in patients who were not alive at the time. Patient charts were reviewed in October Outcome measures Valve haemodynamics were assessed by TTE as mean and peak pressure gradients (PPGs). Early mortality was defined as death within 30 days after surgery. The Swedish personal identity number [13] and the national Total Population Register at Statistics Sweden were used to determine late survival status and date of death, and follow-up ended in October The follow-up time regarding survival was defined as the time in days between the date of surgery and the date of death, the date of emigration, the date of reoperation for aortic bioprosthetic valve dysfunction or at the end of follow-up, whichever occurred first. The follow-up time regarding time to late TTE was defined as the number of days between surgery and the most recent TTE available. For the purpose of this study, severe aortic stenosis was defined as a mean pressure gradient (MPG) above 40 mmhg, and moderate aortic stenosis was defined as an MPG between 25 and 40 mmhg [14]. PPM was defined as moderate when the effective orifice area index (EOAI) 0.85 cm 2 /m 2 and severe when EOAI 0.65 cm 2 /m 2. The EOAI was calculated by using published in vivo measurements [15] indexed to body surface area. Surgical technique All patients underwent transoesophageal echocardiography in the operating room according to standard perioperative management, but the results were not systematically collected for the purpose of this study. All patients underwent a median sternotomy, and the manufacturer s sizer was used for selecting the appropriate valve size. Statistical methods Baseline characteristics were reported as means and standard deviations (SDs) for continuous variables, and proportions for categorical variables. Patients contributed person-time from the date of surgery and were censored at the date of death from any cause, date of emigration, date of reoperation for aortic bioprosthetic valve dysfunction or at the end of follow-up (October 2013), whichever occurred first. The cumulative survival was calculated by the Kaplan Meier method. We used a semi-parametric model [16] to estimate the cumulative incidence function to calculate the proportion of patients who underwent reoperation for aortic bioprosthetic valve dysfunction, thereby accounting for the competing risk of death, i.e. the possibility that death might occur before reoperation. The association between patient characteristics and late survival was analysed by Cox regression. Data management and statistical analyses were performed using Stata version 13.1 (StataCorp LP, College Station, TX, USA) and R version (R Foundation for Statistical Computing, Vienna, Austria). RESULTS Baseline and operative characteristics Baseline and operative characteristics are summarized in Tables 1 and 2. A total of 355 patients were included, 192 (54%) men and 163 (46%) women. The mean age was 75.7 years and 92% of the patients were 65 years or older. An additional procedure was performed in 53%, most commonly coronary artery bypass grafting (CABG). Most (70%) had preserved left ventricular ejection fraction at the time of surgery. The implanted valve sizes ranged from 19 to 29 mm and the most commonly implanted size was 23 mm. Figure 1A shows the distribution of bioprosthetic sizes. The number of implanted valves per year is shown in Figure 1B. In total, 26 patients (7.3%) received a 19-mm, 112 patients (31.6%) received a 21-mm, 148 patients (41.7%) received a 23-mm, 59 patients (16.6%) received a 25-mm, 9 patients (2.5%) received a 27-mm and 1 patient (0.3%) received a 29-mm bioprosthesis. Haemodynamic performance Echocardiographic data were available at early follow-up in 340 patients (96%) and at late follow-up in 161 patients (45%). The mean time from surgery to late postoperative TTE was 6.2 years (maximum 11.5 years). Of the 156 patients alive and free from reoperation because of Mosaic valve failure in August 2012, 89 agreed to participate in an additional echocardiographic study, and 57 actually underwent echocardiographic examination according to a predefined protocol. At the early postoperative TTE, the mean PPG was 39.9 mmhg (SD 14.4) and the mean MPG was 21.1 mmhg (SD 7.7) in the total study population. At late evaluation, the mean PPG was 38.6 mmhg (SD 15.6) and the mean MPG was 22.5 mmhg (SD 10.1) in the total study population. Transvalvular gradients at early and late TTE according to valve size in the total population are shown in Figure 2A. There was a significant association between MPGs at early postoperative TTE and the EOAI (P <0.001) as shown in Figure 2B. We divided the patients into three groups, based on the time from surgery to the late TTE. The first group included 51 patients with a late TTE performed between 30 days to 5 years after surgery. The second group included 49 patients who had information from a late TTE that was performed between 5 and 8 years after surgery. The third group included 61 patients with a late TTE performed between 8 and 12 years postoperatively. In the first group, where late TTE was performed between 30 days and 5 years after surgery, the mean PPG and MPG were 37.2 ORIGINAL ARTICLE

3 758 N. Glaser et al. / Interactive CardioVascular and Thoracic Surgery Table 1: Baseline characteristics in 355 patients who underwent aortic valve replacement with a Medtronic Mosaic bioprosthesis between 2002 and 2008 Table 2: Operative and postoperative characteristics in 355 patients who underwent aortic valve replacement with a Medtronic Mosaic bioprosthesis between 2002 and 2008 Number of patients (%) 355 (100) Age, years (SD) 75.7 (9.4) Female 46 Body mass index (kg/cm 2 ), mean (SD) 25.1 (4.1) egfr (ml/min/1.73 m 2 ), mean (SD) 69 (23) Diabetes mellitus 12 Atrial fibrillation 16 Hypertension 27 Cerebrovascular disease 15 Peripheral vascular disease 6 Chronic obstructive pulmonary disease 7 Prior percutaneous coronary intervention 4 Prior cardiac surgery 3 Left ventricular ejection fraction > <30 5 Aetiology of aortic valve disease Stenosis 84 Regurgitation 11 Stenosis and regurgitation 4 Endocarditis 3 Numbers are percentages unless otherwise stated. egfr: estimated glomerular filtration rate; SD: standard deviation. mmhg (SD 14.9) and 20.9 mmhg (SD 11.5), respectively. In the second group, where late TTE was performed between 5 and 8 years after surgery, the mean PPG and MPG were 40.3 mmhg (SD 14.1) and 23.2 mmhg (SD 8.8), respectively. In the third group, where late TTE was performed between 8 and 12 years, the mean PPG and MPG were 38.2 mmhg (SD 17.3) and 23.2 mmhg (SD 9.9), respectively. The mean PPG and MPG in the three groups, according to valve size, are shown in Figure 3. Patients with a mean pressure gradient corresponding to a moderate or severe aortic stenosis MPG was recorded in 137 of 161 patients with a late TTE. We found 6 patients with an MPG >40 mmhg corresponding to a severe aortic stenosis. One of these patients underwent transcatheter aortic valve implantation (TAVI) with a valve-in-valve procedure 6.5 years after surgery. Another patient was scheduled for reoperation. Two patients were declined surgery because of poor clinical status. Two patients were asymptomatic and were scheduled for echocardiographic follow-up. We found 40 patients (29% of patients with a recorded MPG) with an MPG between 25 and 40 mmhg corresponding to a moderate aortic stenosis. Survival The early mortality rate was 4.8% and the mean follow-up time was 7.1 years (maximum 11.7 years). The total follow-up time was 2523 patient-years. During follow-up, 189 patients died (53%). The cause of death was cardiac in 40 patients (21%), non-cardiac Concomitant cardiac procedure 53 Urgency Elective 89 Urgent 10 Emergent 1 Aortic root enlargement 7 Aortic cross-clamp time, mean (SD) 78 (28) Extracorporeal circulation, mean (SD) 109 (39) Days in the ICU, mean 2.4 Days in the hospital, mean 8.9 Acute kidney injury a 31 Acute kidney injury requiring dialysis 2.6 Indexed effective orifice area (cm 2 /m 2 ) > < Early postoperative transthoracic echocardiography b Peak pressure gradient, mean mmhg (SD) 39.9 (14.4) Mean pressure gradient, mean mmhg (SD) 21.1 (7.7) Numbers are percentages unless otherwise stated. ICU: intensive care unit; SD: standard deviation. a Acute kidney injury was defined as an increase of 26 mmol/l (0.3 mg/l) in postoperative creatinine. b The early postoperative transthoracic echocardiography was performed during the initial hospital stay, most commonly on postoperative day 3. in 45 patients (24%) and unknown in 104 patients (55%). The unadjusted survival at 1, 5 and 10 years was 92, 79 and 42%, respectively, and is shown in Figure 4. Factors associated with survival are given in Table 3. Aortic bioprosthetic valve reoperations The unadjusted cumulative incidence rate of reoperation because of aortic valve bioprosthetic failure after AVR with a Mosaic bioprosthesis was 0.3, 1.7 and 3.1% at 1, 5 and 10 years, respectively. In total, 10 patients (2.8%) underwent AVR or TAVI (valve-in-valve implantation) because of failure of the Mosaic bioprosthesis. The reason for reoperation was SVD in 8 patients (of which 3 patients underwent TAVI) and endocarditis in 2 patients. Reoperation for SVD within 48 months after surgery was required in 3 patients. Prosthesis patient mismatch and high transvalvular gradients Moderate and severe PPM was found in 250 (70%) and 49 patients (14%), respectively. Moderate or severe PPM was not significantly associated with early or late mortality in unadjusted or multivariable adjusted analyses (Table 3). No significant association between PPM and survival was found in patients with reduced left ventricular function. The Kaplan Meier estimated unadjusted survival in patients with no PMM, moderate PPM or severe PPM, and in patients with an MPG below or above 25 mmhg at early echocardiographic follow-up are shown in Figure 5.

4 N. Glaser et al. / Interactive CardioVascular and Thoracic Surgery 759 Figure 1: (A) Manufacturer-labelled bioprosthesis size for 355 patients who received a Medtronic Mosaic aortic valve bioprosthesis. (B) Number of Medtronic Mosaic aortic valve implantations per year. ORIGINAL ARTICLE Figure 2: (A) Transvalvular peak and mean pressure gradients at early and late postoperative echocardiography according to valve size in the total study population. The number of patients is shown inside the bars. (B) There was a significant association between mean pressure gradients at early postoperative transthoracic echocardiography and the effective orifice area index in 300 patients with a Medtronic Mosaic bioprosthesis (P <0.001). The fitted regression line is shown in red. TTE: transthoracic echocardiography. Figure 3: The patients were divided into three groups based on the time from surgery to the late echocardiography. The first group (n = 51) included patients with a late echocardiography performed between 30 days and 5 years after surgery. The second group (n = 49) included patients with a late echocardiography performed between 5 and 8 years after surgery. The third group (n = 61) included patients with a late echocardiography performed between 8 and 12 years after surgery. The transvalvular peak and mean pressure gradients for each group according to valve size are shown from left to right. The number of patients is shown inside the bars.

5 760 N. Glaser et al. / Interactive CardioVascular and Thoracic Surgery DISCUSSION Figure 4: Kaplan Meier estimated unadjusted survival in 355 patients after aortic valve replacement with a Medtronic Mosaic bioprosthesis. We found that the Mosaic bioprosthesis in the aortic position had acceptable clinical performance up to 11.7 years of follow-up. However, one-third of the patients had transvalvular gradients corresponding to a moderate-to-severe aortic stenosis at late follow-up. Additionally, 84% had a moderate-to-severe PPM. Neither high postoperative gradients nor PPM was significantly associated with long-term survival in our population. The Mosaic bioprosthesis in the aortic position has been in clinical use since 1994 with several follow-up studies reporting excellent clinical performance [2, 3, 6, 17]. Jamieson et al. performed a multicentre study including 797 patients undergoing AVR with the Mosaic bioprosthesis. The mean follow-up was 7.5 years and their results showed a satisfactory performance with an overall survival rate of 62.5% at 10 years and 55.8% at 12 years. They reported a cumulative incidence rate of freedom from reoperation because of SVD at 12 years of 95.9 and 80.6% in patients above or below Table 3: Unadjusted and adjusted association between patient characteristics and all-cause mortality in 355 patients who underwent aortic valve replacement with a Medtronic Mosaic bioprosthesis between 2002 and 2008 Unadjusted hazard ratio 95% CI P-value Adjusted hazard ratio 95% CI P-value Age (1 year) < <0.001 Female sex (male sex reference) Body mass index (1 kg/cm 2 ) egfr (1 ml/min/1.73 m 2 ) < Diabetes mellitus Atrial fibrillation Hypertension Cerebrovascular disease Peripheral vascular disease Chronic obstructive pulmonary disease Prior percutaneous coronary intervention Prior cardiac surgery < Left ventricular ejection fraction (%) >49 (reference) < < Aetiology of aortic valve disease Stenosis (reference) Regurgitation Stenosis and regurgitation Endocarditis Urgency Elective (reference) Urgent Emergent Aortic cross-clamp time (1 min) Extracorporeal circulation (1 min) Concomitant cardiac procedure Aortic root enlargement Acute kidney injury a < Indexed effective orifice area (cm 2 /m 2 ) >0.85 (reference) < Early postoperative transthoracic echocardiography b Peak pressure gradient (1 mmhg) Mean pressure gradient (1 mmhg) Mean pressure gradient 25 mmhg CI: confidence interval; egfr: estimated glomerular filtration rate. a Acute kidney injury was defined as an increase of 26 mmol/l (0.3 mg/l) in postoperative creatinine. b The early postoperative transthoracic echocardiography was performed during initial hospital stay, most commonly on postoperative day 3.

6 N. Glaser et al. / Interactive CardioVascular and Thoracic Surgery 761 Figure 5: Kaplan Meier estimated unadjusted survival after aortic valve replacement with a Medtronic Mosaic bioprosthesis in patients with no PMM, moderate PPM or severe PPM (left-hand graph), and in patients with a mean pressure gradient (MPG) below or above 25 mmhg at early echocardiographic follow-up (right-hand graph). PPM: prosthesis patient mismatch. 60 years, respectively. One participating centre evaluated the echocardiographic performance of all valve sizes and found an MPG of 12.5 ± 5.1 mmhg at 1 year (223 patients) and 15.8 ± 8.3 mmhg at 10 years (71 patients). However, other longitudinal follow-up studies have shown that the Mosaic bioprosthesis transvalvular gradients increased with time [4, 18]. Our echocardiographic data showed an increasing transvalvular MPG from early to late TTE in smaller valve sizes (19 and 21 mm) but not in valve sizes 23 mm and above. Furthermore, other studies have shown results suggesting higher gradients as well as a higher incidence of PPM in the Mosaic bioprosthesis in comparison with other contemporary bioprostheses [7, 8, 19]. Dalmau et al. prospectively evaluated the haemodynamic performance and long-term survival in 108 patients undergoing AVR with either the Carpentier-Edwards Perimount Magna bioprosthesis (n = 54) or the Mosaic bioprosthesis (n = 54). They reported a significantly lower transvalvular gradient at 1 and 5 years in the Perimount Magna group than in the Mosaic group with an MPG of 10.3 vs 16.3 mmhg at 1 year and 9.6 vs 16.8 mmhg at 5 years. They also found a higher incidence of PPM in the Mosaic group (30.1% at 1 year and 73.9% at 5 years) than in the Perimount Magna group (9.2% at 1 year and 22.9% at 5 years). Moderate-to-severe PPM was present in 84% of the patients in our study, which is comparable with previous reports from Kandler et al. (82%), Dalmau et al. (73.9%) and Eichinger et al. (69%) [8, 19, 20]. PPM is generally considered to cause a reduced left ventricular mass regression, higher incidence of cardiac complications and an increase in all-cause mortality [15, 21]. In our study population, we found no association between PPM and long-term survival. Although the long-term survival in our study population was lower than that reported by Jamieson et al. (42 and 62.5%, respectively, at 10 years), this can probably be explained by differences in baseline characteristics and inclusion criteria, such as lower age (69 vs 75.7 years) and exclusion of patients with concomitant surgery except CABG in their cohort. In our study group, echocardiography demonstrated higher transvalvular gradients than that reported for other commonly used bioprostheses in the aortic position, including the Carpentier-Edwards Perimount pericardial bioprosthesis, the Medtronic Hancock II porcine bioprosthesis and the St Jude Medical Biocor porcine bioprostheses. In long-term follow-up studies, the Perimount bioprosthesis has been reported to have a mean PPG of 24.9 mmhg and an MPG of 13.4; the Hancock II a PPG of 32.7 mmhg and an MPG of 16.0 mmhg; and the Biocor a PPG of 30.8 mmhg and an MPG of 16.6 mmhg [22, 23]. In addition to the higher than expected postoperative gradients, our results also showed that 34% of the patients had an MPG 25 mmhg at long-term follow-up echocardiography, corresponding to a moderate-to-severe aortic stenosis. However, an MPG 25 mmhg was not associated with higher mortality in our study. Study limitations The major limitation was that late echocardiographic data were not available in all patients for various reasons. In an attempt to achieve a more complete TTE follow-up, we invited all patients alive in the fall of 2012 to an additional long-term follow-up echocardiography as part of this study protocol. Echocardiographic examinations were generally performed by clinicians for clinical reasons and not by dedicated study personnel according to a predefined prospectively designed study protocol. This might introduce bias because symptomatic patients might undergo TTE evaluation more often, and could possibly skew our data towards higher gradients. However, almost all examinations were performed by clinical physiologists (a clinical medical specialty for physicians in Sweden) at accredited clinical physiology departments. Therefore, echocardiographic data were mostly collected according to a standardized procedure. This was a single-centre, non-randomized study. However, during the study period, the Mosaic bioprosthesis was the standard valve used for AVR according to institutional policy at our department, thus minimizing selection bias. Additionally, because it was a single-centre study, patient management and care were very similar in all patients. A particular strength of our study was the high quality of the Swedish national registers that ensured complete follow-up, with no loss to follow-up. Other strengths were the relatively large number of patients and long follow-up. However, the study data were limited to what was attainable from patient charts, and institutional and national registers. CONCLUSIONS We found that the Mosaic bioprosthesis in the aortic position had acceptable clinical performance up to 11.7 years of follow-up. However, one-third of the patients had transvalvular gradients ORIGINAL ARTICLE

7 762 N. Glaser et al. / Interactive CardioVascular and Thoracic Surgery corresponding to a moderate-to-severe aortic stenosis at late follow-up. Additionally, 84% had a moderate-to-severe PPM. Neither high postoperative gradients nor PPM was significantly associated with long-term survival in our population. Nevertheless, these results suggest a need for further evaluation of the Mosaic bioprosthesis in the aortic position. ACKNOWLEDGEMENTS The authors thank Susanne Hylander, for excellent assistance with data collection. Funding This work was supported by research grants from the Mats Kleberg Foundation. Conflict of interest: none declared. REFERENCES [1] Duarte IG, MacDonald MJ, Cooper WA, Schmarkey SL, Gott JP, Brown WM III et al. In vivo hemodynamic, histologic, and antimineralization characteristics of the Mosaic bioprosthesis. Ann Thorac Surg 2001;71:92 9. [2] Jamieson WR, Riess FC, Raudkivi PJ, Metras J, Busse EF, Goldstein J et al. 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